Throughfall under a teak plantation in Thailand: a multifactorial analysis on the effects of canopy phenology and meteorological conditions

NASA Astrophysics Data System (ADS)

Tanaka, N.; Levia, D. F., Jr.; Igarashi, Y.; Nanko, K.; Yoshifuji, N.; Tanaka, K.; Chatchai, T.; Suzuki, M.; Kumagai, T.

2014-12-01

Teak (Tectona grandis Linn. f.) plantations cover vast areas throughout Southeast Asia and are of great economic importance. This study has sought to increase our understanding of throughfall inputs under teak by analyzing the abiotic and biotic factors governing throughfall amounts and throughfall ratios in relation to three canopy phenophases (leafless, leafing, and leafed). There is no rain during the brief leaf senescence phenophase. Daily data was available for both throughfall volumes and depths as well as leaf area index. Detailed meteorological data were available in situ every ten minutes. Leveraging this high-resolution field data, we employed boosted regression trees (BRT) analysis to identify the primary controls on throughfall amount and ratio during each of the three canopy phenophases. Whereas throughfall amounts were always dominated by the magnitude of rainfall (as expected), throughfall ratios were governed by a suite of predictor variables during each phenophase. The BRT analysis demonstrated that throughfall ratio in the leafless phase was most influenced (in descending order of importance) by air temperature, rainfall amount, maximum wind speed, and rainfall intensity. Throughfall ratio in the leafed phenophase was dominated by rainfall amount which exerted 54.0% of the relative influence. The leafing phenophase was an intermediate case where rainfall amount, air temperature, and vapor pressure deficit were most important. Our results highlight the fact that throughfall ratios are differentially influenced by a suite of meteorological variables during leafless, leafing, and leafed phenophases. Abiotic variables (rainfall amount, air temperature, vapor pressure deficit, and maximum wind speed) trumped leaf area index and stand density in their effect on throughfall ratio. The leafing phenophase, while transitional in nature and short in duration, has a detectable and unique impact on water inputs to teak plantations. Further work is clearly needed to better gauge the importance of the leaf emergence period to the stemflow hydrology and forest biogeochemistry of teak plantations.

Functional traits of the understory plant community of a pyrogenic longleaf pine forest across environmental gradients.

PubMed

Ames, Gregory M; Anderson, Steven M; Ungberg, Eric A; Wright, Justin P

2017-08-01

Understanding and predicting the response of plant communities to environmental changes and disturbances such as fire requires an understanding of the functional traits present in the system, including within and across species variability, and their dynamics over time. These data are difficult to obtain as few studies provide comprehensive information for more than a few traits or species, rarely cover more than a single growing season, and usually present only summary statistics of trait values. As part of a larger study seeking to understand the dynamics of plant communities in response to different prescribed fire regimes, we measured the functional traits of the understory plant communities located in over 140 permanent plots spanning strong gradients in soil moisture in a pyrogenic longleaf pine forest in North Carolina, USA, over a four-year period from 2011 and 2014. We present over 120,000 individual trait measurements from over 130 plant species representing 91 genera from 47 families. We include data on the following 18 traits: specific leaf area, leaf dry matter content, leaf area, leaf length, leaf width, leaf perimeter, plant height, leaf nitrogen, leaf carbon, leaf carbon to nitrogen ratio, water use efficiency, time to ignition, maximum flame height, maximum burn temperature, mass-specific burn time, mass-specific smolder time, branching architecture, and the ratio of leaf matter consumed by fire. We also include information on locations, soil moisture, relative elevation, soil bulk density, and fire histories for each site. © 2017 by the Ecological Society of America.

Plant Trait-Species Abundance Relationships Vary with Environmental Properties in Subtropical Forests in Eastern China

PubMed Central

Yan, En-Rong; Yang, Xiao-Dong; Chang, Scott X.; Wang, Xi-Hua

2013-01-01

Understanding how plant trait-species abundance relationships change with a range of single and multivariate environmental properties is crucial for explaining species abundance and rarity. In this study, the abundance of 94 woody plant species was examined and related to 15 plant leaf and wood traits at both local and landscape scales involving 31 plots in subtropical forests in eastern China. Further, plant trait-species abundance relationships were related to a range of single and multivariate (PCA axes) environmental properties such as air humidity, soil moisture content, soil temperature, soil pH, and soil organic matter, nitrogen (N) and phosphorus (P) contents. At the landscape scale, plant maximum height, and twig and stem wood densities were positively correlated, whereas mean leaf area (MLA), leaf N concentration (LN), and total leaf area per twig size (TLA) were negatively correlated with species abundance. At the plot scale, plant maximum height, leaf and twig dry matter contents, twig and stem wood densities were positively correlated, but MLA, specific leaf area, LN, leaf P concentration and TLA were negatively correlated with species abundance. Plant trait-species abundance relationships shifted over the range of seven single environmental properties and along multivariate environmental axes in a similar way. In conclusion, strong relationships between plant traits and species abundance existed among and within communities. Significant shifts in plant trait-species abundance relationships in a range of environmental properties suggest strong environmental filtering processes that influence species abundance and rarity in the studied subtropical forests. PMID:23560114

Effects of deer on the photosynthetic performance of invasive and native forest herbs.

PubMed

Heberling, J Mason; Brouwer, Nathan L; Kalisz, Susan

2017-03-01

Overabundant generalist herbivores can facilitate non-native plant invasions, presumably through direct and indirect modifications to the environment that affect plant performance. However, ecophysiological mechanisms behind ungulate-mediated plant invasions have not been well-studied. At a long-term Odocoileus virginianus (white-tailed deer) exclusion site in a temperate deciduous forest, we quantified deer-mediated ecophysiological impacts on an invasive biennial Alliaria petiolata (garlic mustard) and two palatable native herbaceous perennials, Maianthemum racemosum and Trillium grandiflorum . In mid-summer, we found that leaf-level light availability was higher in unfenced areas compared with areas fenced to exclude deer. Alliaria in unfenced areas exhibited 50 % higher mean maximum photosynthetic rates compared with fenced areas. Further, specific leaf area decreased by 48 % on average in unfenced areas, suggesting leaf structural responses to higher light levels. Similarly, Maianthemum had 42 % higher mean photosynthetic rates and 33 % decreased mean specific leaf area in unfenced areas, but these functional advantages were likely countered by high rates of deer herbivory. By contrast, Trillium exhibited significantly lower (26 %) maximum photosynthetic rates in unfenced areas, but SLA did not differ. Deer-mediated differences in light saturated photosynthetic rates for all three species were only significant during months with overstory tree canopy cover, when light availability in the herb layer was significantly lower in fenced areas. Alliaria 's enhanced photosynthetic rates implicate overabundant deer, a situation that is nearly ubiquitous across its invaded range. Collectively, our results provide empirical evidence that generalist herbivores can alter non-native plant physiology to facilitate invasion.

Hydraulic constraints modify optimal photosynthetic profiles in giant sequoia trees.

PubMed

Ambrose, Anthony R; Baxter, Wendy L; Wong, Christopher S; Burgess, Stephen S O; Williams, Cameron B; Næsborg, Rikke R; Koch, George W; Dawson, Todd E

2016-11-01

Optimality theory states that whole-tree carbon gain is maximized when leaf N and photosynthetic capacity profiles are distributed along vertical light gradients such that the marginal gain of nitrogen investment is identical among leaves. However, observed photosynthetic N gradients in trees do not follow this prediction, and the causes for this apparent discrepancy remain uncertain. Our objective was to evaluate how hydraulic limitations potentially modify crown-level optimization in Sequoiadendron giganteum (giant sequoia) trees up to 90 m tall. Leaf water potential (Ψ l ) and branch sap flow closely followed diurnal patterns of solar radiation throughout each tree crown. Minimum leaf water potential correlated negatively with height above ground, while leaf mass per area (LMA), shoot mass per area (SMA), leaf nitrogen content (%N), and bulk leaf stable carbon isotope ratios (δ(13)C) correlated positively with height. We found no significant vertical trends in maximum leaf photosynthesis (A), stomatal conductance (g s), and intrinsic water-use efficiency (A/g s), nor in branch-averaged transpiration (E L), stomatal conductance (G S), and hydraulic conductance (K L). Adjustments in hydraulic architecture appear to partially compensate for increasing hydraulic limitations with height in giant sequoia, allowing them to sustain global maximum summer water use rates exceeding 2000 kg day(-1). However, we found that leaf N and photosynthetic capacity do not follow the vertical light gradient, supporting the hypothesis that increasing limitations on water transport capacity with height modify photosynthetic optimization in tall trees.

Strategies of leaf expansion in Ficus carica under semiarid conditions.

PubMed

González-Rodríguez, A M; Peters, J

2010-05-01

Leaf area expansion, thickness and inclination, gas exchange parameters and relative chlorophyll content were analysed in field-grown fig (Ficus carica L.) leaves over time, from emergence until after full leaf expansion (FLE). Ficus carica leaves showed a subtle change in shape during the early stages of development, and FLE was reached within ca. 30 days after emergence. Changes in leaf thickness and inclination after FLE demonstrated good adaptation to environmental conditions during summer in areas with a Mediterranean climate. Changes in gas exchange parameters and relative chlorophyll content showed that F. carica is a delayed-greening species, reaching maximum values 20 days after FLE. Correlation analysis of datasets collected during leaf expansion, confirmed dependence among structural and functional traits in F. carica. Pn was directly correlated with stomatal conductance (Gs), transpiration (E), leaf area (LA) and relative chlorophyll content up to FLE. The effect of pruning on leaf expansion, a cultural technique commonly applied in this fruit tree, was also evaluated. Although leaf development in pruned branches gave a significantly higher relative leaf area growth rate (RGR(l)) and higher LA than non-pruned branches, no significant differences were found in other morphological and physiological traits, indicating no pruning effect on leaf development. All studied morphological and physiological characteristics indicate that F. carica is well adapted to semiarid conditions. The delayed greening strategy of this species is discussed.

Constraints on physiological function associated with branch architecture and wood density in tropical forest trees.

PubMed

Meinzer, Frederick C; Campanello, Paula I; Domec, Jean-Christophe; Genoveva Gatti, M; Goldstein, Guillermo; Villalobos-Vega, Randol; Woodruff, David R

2008-11-01

This study examined how leaf and stem functional traits related to gas exchange and water balance scale with two potential proxies for tree hydraulic architecture: the leaf area:sapwood area ratio (A(L):A(S)) and wood density (rho(w)). We studied the upper crowns of individuals of 15 tropical forest tree species at two sites in Panama with contrasting moisture regimes and forest types. Transpiration and maximum photosynthetic electron transport rate (ETR(max)) per unit leaf area declined sharply with increasing A(L):A(S), as did the ratio of ETR(max) to leaf N content, an index of photosynthetic nitrogen-use efficiency. Midday leaf water potential, bulk leaf osmotic potential at zero turgor, branch xylem specific conductivity, leaf-specific conductivity and stem and leaf capacitance all declined with increasing rho(w). At the branch scale, A(L):A(S) and total leaf N content per unit sapwood area increased with rho(w), resulting in a 30% increase in ETR(max) per unit sapwood area with a doubling of rho(w). These compensatory adjustments in A(L):A(S), N allocation and potential photosynthetic capacity at the branch level were insufficient to completely offset the increased carbon costs of producing denser wood, and exacerbated the negative impact of increasing rho(w) on branch hydraulics and leaf water status. The suite of tree functional and architectural traits studied appeared to be constrained by the hydraulic and mechanical consequences of variation in rho(w).

Potential of trees leaf/ bark to control atmospheric metals in a gas and petrochemical zone.

PubMed

Safari, Mojgan; Ramavandi, Bahman; Sanati, Ali Mohammad; Sorial, George A; Hashemi, Seyedenayat; Tahmasebi, Saeid

2018-05-22

Leaf and bark of trees are tools for assessing the effects of the heavy metals pollution and monitoring the environmental air quality. The aim of this study was to evaluate the presence of Ni, Pb, V, and Co metals in four tree/shrub species (Conocarpus erectus, Nerium oleander, Bougainvillea spectabilis willd, and Hibiscus rosa-sinensis) in the heavily industrial zone of Asaloyeh, Iran. Two industrial zones (sites 1 and 2), two urban areas (sites 3 and 4), and two rural areas (sites 5 and 6) in the Asaloyeh industrial zone and an uncontaminated area as a control were selected. Sampling from leaf and bark of trees was carried out in spring 2016. The metals content in the washed and unwashed leaf and bark was investigated. The results showed that four studied metals in N. oleander, C. erectus, and B. spectabilis willd in all case sites were significantly higher than that of in the control site (p < 0.05). The highest concentration of metals was found in sites 3, 4, and 6; this was due to dispersion of the pollutants from industrial environments by dominant winds. The highest comprehensive bio-concentration index (CBCI) was found in leaf (0.37) and bark (0.12) of N. oleander. The maximum metal accumulation index (MAI) in the samples was found in leaf of N. oleander (1.58) and in bark of H. rosa-sinensis (1.95). The maximum bio-concentration factor (BCF) was seen for cobalt metal in the N. oleander leaf (0.89). The nickel concentration in washed-leaf samples of C. erectus was measured to be 49.64% of unwashed one. In general, the N. oleander and C. erectus species were found to have the highest absorption rate from the atmosphere and soil than other studied species, and are very suitable tools for managing air pollution in highly industrialized areas. Copyright © 2018 Elsevier Ltd. All rights reserved.

Linking Xylem Hydraulic Conductivity and Vulnerability to the Leaf Economics Spectrum—A Cross-Species Study of 39 Evergreen and Deciduous Broadleaved Subtropical Tree Species

PubMed Central

Kröber, Wenzel; Zhang, Shouren; Ehmig, Merten; Bruelheide, Helge

2014-01-01

While the fundamental trade-off in leaf traits related to carbon capture as described by the leaf economics spectrum is well-established among plant species, the relationship of the leaf economics spectrum to stem hydraulics is much less known. Since carbon capture and transpiration are coupled, a close connection between leaf traits and stem hydraulics should be expected. We thus asked whether xylem traits that describe drought tolerance and vulnerability to cavitation are linked to particular leaf traits. We assessed xylem vulnerability, using the pressure sleeve technique, and anatomical xylem characteristics in 39 subtropical tree species grown under common garden conditions in the BEF-China experiment and tested for correlations with traits related to the leaf economics spectrum as well as to stomatal control, including maximum stomatal conductance, vapor pressure deficit at maximum stomatal conductance and vapor pressure deficit at which stomatal conductance is down-regulated. Our results revealed that specific xylem hydraulic conductivity and cavitation resistance were closely linked to traits represented in the leaf economic spectrum, in particular to leaf nitrogen concentration, as well as to log leaf area and leaf carbon to nitrogen ratio but not to any parameter of stomatal conductance. The study highlights the potential use of well-known leaf traits from the leaf economics spectrum to predict plant species' drought resistance. PMID:25423316

Linking xylem hydraulic conductivity and vulnerability to the leaf economics spectrum--a cross-species study of 39 evergreen and deciduous broadleaved subtropical tree species.

PubMed

Kröber, Wenzel; Zhang, Shouren; Ehmig, Merten; Bruelheide, Helge

2014-01-01

While the fundamental trade-off in leaf traits related to carbon capture as described by the leaf economics spectrum is well-established among plant species, the relationship of the leaf economics spectrum to stem hydraulics is much less known. Since carbon capture and transpiration are coupled, a close connection between leaf traits and stem hydraulics should be expected. We thus asked whether xylem traits that describe drought tolerance and vulnerability to cavitation are linked to particular leaf traits. We assessed xylem vulnerability, using the pressure sleeve technique, and anatomical xylem characteristics in 39 subtropical tree species grown under common garden conditions in the BEF-China experiment and tested for correlations with traits related to the leaf economics spectrum as well as to stomatal control, including maximum stomatal conductance, vapor pressure deficit at maximum stomatal conductance and vapor pressure deficit at which stomatal conductance is down-regulated. Our results revealed that specific xylem hydraulic conductivity and cavitation resistance were closely linked to traits represented in the leaf economic spectrum, in particular to leaf nitrogen concentration, as well as to log leaf area and leaf carbon to nitrogen ratio but not to any parameter of stomatal conductance. The study highlights the potential use of well-known leaf traits from the leaf economics spectrum to predict plant species' drought resistance.

Does citrus leaf miner impair hydraulics and fitness of citrus host plants?

PubMed

Raimondo, Fabio; Trifilò, Patrizia; Gullo, Maria A Lo

2013-12-01

Gas exchange and hydraulic features were measured in leaves of three different Citrus species (Citrus aurantium L., Citrus limon L., Citrus  ×  paradisii Macfad) infested by Phyllocnistis citrella Staiton, with the aim to quantify the impact of this pest on leaf hydraulics and, ultimately, on plant fitness. Infested leaves were characterized by the presence on the leaf blade of typical snake-shaped mines and, in some cases, of a crumpled leaf blade. Light microscopy showed that leaf crumpling was induced by damage to the cuticular layer. In all three Citrus species examined: (a) the degree of infestation did not exceed 10% of the total surface area of infested plants; (b) control and infested leaves showed similar values of minimum diurnal leaf water potential, leaf hydraulic conductance and functional vein density; and (c) maximum diurnal values of stomatal conductance to water vapour, transpiration rate and photosynthetic rate (An) were similar in both control leaves and the green areas of infested leaves. A strong reduction of An was recorded only in mined leaf areas. Our data suggest that infestation with P. citrella does not cause conspicuous plant productivity reductions in young Citrus plants, at least not in the three Citrus species studied here.

A Constrained Maximization Model for inspecting the impact of leaf shape on optimal leaf size and stoma resistance

NASA Astrophysics Data System (ADS)

Ding, J.; Johnson, E. A.; Martin, Y. E.

2017-12-01

Leaf is the basic production unit of plants. Water is the most critical resource of plants. Its availability controls primary productivity of plants by affecting leaf carbon budget. To avoid the damage of cavitation from lowering vein water potential t caused by evapotranspiration, the leaf must increase the stomatal resistance to reduce evapotranspiration rate. This comes at the cost of reduced carbon fixing rate as increasing stoma resistance meanwhile slows carbon intake rate. Studies suggest that stoma will operate at an optimal resistance to maximize the carbon gain with respect to water. Different plant species have different leaf shapes, a genetically determined trait. Further, on the same plant leaf size can vary many times in size that is related to soil moisture, an indicator of water availability. According to metabolic scaling theory, increasing leaf size will increase total xylem resistance of vein, which may also constrain leaf carbon budget. We present a Constrained Maximization Model of leaf (leaf CMM) that incorporates metabolic theory into the coupling of evapotranspiration and carbon fixation to examine how leaf size, stoma resistance and maximum net leaf primary productivity change with petiole xylem water potential. The model connects vein network structure to leaf shape and use the difference between petiole xylem water potential and the critical minor vein cavitation forming water potential as the budget. The CMM shows that both maximum net leaf primary production and optimal leaf size increase with petiole xylem water potential while optimal stoma resistance decreases. Narrow leaf has overall lower optimal leaf size and maximum net leaf carbon gain and higher optimal stoma resistance than those of broad leaf. This is because with small width to length ratio, total xylem resistance increases faster with leaf size. Total xylem resistance of narrow leaf increases faster with leaf size causing higher average and marginal cost of xylem water potential with respect to net leaf carbon gain. With same leaf area, total xylem resistance of narrow leaf is higher than broad leaf. Given same stoma resistance and petiole water potential, narrow leaf will lose more xylem water potential than broad leaf. Consequently, narrow leaf has smaller size and higher stoma resistance at optimum.

Effects of height on treetop transpiration and stomatal conductance in coast redwood (Sequoia sempervirens).

PubMed

Ambrose, Anthony R; Sillett, Stephen C; Koch, George W; Van Pelt, Robert; Antoine, Marie E; Dawson, Todd E

2010-10-01

Treetops become increasingly constrained by gravity-induced water stress as they approach maximum height. Here we examine the effects of height on seasonal and diurnal sap flow dynamics at the tops of 12 unsuppressed Sequoia sempervirens (D. Don) Endl. (coast redwood) trees 68-113 m tall during one growing season. Average treetop sap velocity (V(S)), transpiration per unit leaf area (E(L)) and stomatal conductance per unit leaf area (G(S)) significantly decreased with increasing height. These differences in sap flow were associated with an unexpected decrease in treetop sapwood area-to-leaf area ratios (A(S):A(L)) in the tallest trees. Both E(L) and G(S) declined as soil moisture decreased and vapor pressure deficit (D) increased throughout the growing season with a greater decline in shorter trees. Under high soil moisture and light conditions, reference G(S) (G(Sref); G(S) at D = 1 kPa) and sensitivity of G(S) to D (-δ; dG(S)/dlnD) significantly decreased with increasing height. The close relationship we observed between G(Sref) and -δ is consistent with the role of stomata in regulating E(L) and leaf water potential (Ψ(L)). Our results confirm that increasing tree height reduces gas exchange of treetop foliage and thereby contributes to lower carbon assimilation and height growth rates as S. sempervirens approaches maximum height.

Sensitivity Analysis of Biome-Bgc Model for Dry Tropical Forests of Vindhyan Highlands, India

NASA Astrophysics Data System (ADS)

Kumar, M.; Raghubanshi, A. S.

2011-08-01

A process-based model BIOME-BGC was run for sensitivity analysis to see the effect of ecophysiological parameters on net primary production (NPP) of dry tropical forest of India. The sensitivity test reveals that the forest NPP was highly sensitive to the following ecophysiological parameters: Canopy light extinction coefficient (k), Canopy average specific leaf area (SLA), New stem C : New leaf C (SC:LC), Maximum stomatal conductance (gs,max), C:N of fine roots (C:Nfr), All-sided to projected leaf area ratio and Canopy water interception coefficient (Wint). Therefore, these parameters need more precision and attention during estimation and observation in the field studies.

Speed versus endurance tradeoff in plants: Leaves with higher photosynthetic rates show stronger seasonal declines

PubMed Central

Zhang, Yong-Jiang; Sack, Lawren; Cao, Kun-Fang; Wei, Xue-Mei; Li, Nan

2017-01-01

We tested for a tradeoff across species between plant maximum photosynthetic rate and the ability to maintain photosynthesis under adverse conditions in the unfavorable season. Such a trade-off would be consistent with the observed trade-off between maximum speed and endurance in athletes and some animals that has been explained by cost-benefit theory. This trend would have importance for the general understanding of leaf design, and would simplify models of annual leaf carbon relations. We tested for such a trade-off using a database analysis across vascular plants and using an experimental approach for 29 cycad species, representing an ancient plant lineage with diversified evergreen leaves. In both tests, a higher photosynthetic rate per mass or per area in the favorable season was associated with a stronger absolute or percent decline in the unfavorable season. We resolved a possible mechanism based on biomechanics and nitrogen allocation; cycads with high leaf toughness (leaf mass per area) and higher investment in leaf construction than in physiological function (C/N ratio) tended to have lower warm season photosynthesis but less depression in the cool season. We propose that this trade-off, consistent with cost-benefit theory, represents a significant physio-phenological constraint on the diversity and seasonal dynamics of photosynthetic rate. PMID:28186201

Turning over a new 'leaf': multiple functional significances of leaves versus phyllodes in Hawaiian Acacia koa.

PubMed

Pasquet-Kok, Jessica; Creese, Christine; Sack, Lawren

2010-12-01

Hawaiian endemic tree Acacia koa is a model for heteroblasty with bipinnately compound leaves and phyllodes. Previous studies suggested three hypotheses for their functional differentiation: an advantage of leaves for early growth or shade tolerance, and an advantage of phyllodes for drought tolerance. We tested the ability of these hypotheses to explain differences between leaf types for potted plants in 104 physiological and morphological traits, including gas exchange, structure and composition, hydraulic conductance, and responses to varying light, intercellular CO(2) , vapour pressure deficit (VPD) and drought. Leaf types were similar in numerous traits including stomatal pore area per leaf area, leaf area-based gas exchange rates and cuticular conductance. Each hypothesis was directly supported by key differences in function. Leaves had higher mass-based gas exchange rates, while the water storage tissue in phyllodes contributed to greater capacitance per area; phyllodes also showed stronger stomatal closure at high VPD, and higher maximum hydraulic conductance per area, with stronger decline during desiccation and recovery with rehydration. While no single hypothesis completely explained the differences between leaf types, together the three hypotheses explained 91% of differences. These findings indicate that the heteroblasty confers multiple benefits, realized across different developmental stages and environmental contexts. © 2010 Blackwell Publishing Ltd.

Effects of water stress on irradiance acclimation of leaf traits in almond trees.

PubMed

Egea, Gregorio; González-Real, María M; Baille, Alain; Nortes, Pedro A; Conesa, María R; Ruiz-Salleres, Isabel

2012-04-01

Photosynthetic acclimation to highly variable local irradiance within the tree crown plays a primary role in determining tree carbon uptake. This study explores the plasticity of leaf structural and physiological traits in response to the interactive effects of ontogeny, water stress and irradiance in adult almond trees that have been subjected to three water regimes (full irrigation, deficit irrigation and rain-fed) for a 3-year period (2006-08) in a semiarid climate. Leaf structural (dry mass per unit area, N and chlorophyll content) and photosynthetic (maximum net CO(2) assimilation, A(max), maximum stomatal conductance, g(s,max), and mesophyll conductance, g(m)) traits and stem-to-leaf hydraulic conductance (K(s-l)) were determined throughout the 2008 growing season in leaves of outer south-facing (S-leaves) and inner northwest-facing (NW-leaves) shoots. Leaf plasticity was quantified by means of an exposure adjustment coefficient (ε=1-X(NW)/X(S)) for each trait (X) of S- and NW-leaves. Photosynthetic traits and K(s-l) exhibited higher irradiance-elicited plasticity (higher ε) than structural traits in all treatments, with the highest and lowest plasticity being observed in the fully irrigated and rain-fed trees, respectively. Our results suggest that water stress modulates the irradiance-elicited plasticity of almond leaves through changes in crown architecture. Such changes lead to a more even distribution of within-crown irradiance, and hence of the photosynthetic capacity, as water stress intensifies. Ontogeny drove seasonal changes only in the ε of area- and mass-based N content and mass-based chlorophyll content, while no leaf age-dependent effect was observed on ε as regards the physiological traits. Our results also indicate that the irradiance-elicited plasticity of A(max) is mainly driven by changes in leaf dry mass per unit area, in g(m) and, most likely, in the partitioning of the leaf N content.

LCE: leaf carbon exchange data set for tropical, temperate, and boreal species of North and Central America.

PubMed

Smith, Nicholas G; Dukes, Jeffrey S

2017-11-01

Leaf canopy carbon exchange processes, such as photosynthesis and respiration, are substantial components of the global carbon cycle. Climate models base their simulations of photosynthesis and respiration on an empirical understanding of the underlying biochemical processes, and the responses of those processes to environmental drivers. As such, data spanning large spatial scales are needed to evaluate and parameterize these models. Here, we present data on four important biochemical parameters defining leaf carbon exchange processes from 626 individuals of 98 species at 12 North and Central American sites spanning ~53° of latitude. The four parameters are the maximum rate of Rubisco carboxylation (V cmax ), the maximum rate of electron transport for the regeneration of Ribulose-1,5,-bisphosphate (J max ), the maximum rate of phosphoenolpyruvate carboxylase carboxylation (V pmax ), and leaf dark respiration (R d ). The raw net photosynthesis by intercellular CO 2 (A/C i ) data used to calculate V cmax , J max , and V pmax rates are also presented. Data were gathered on the same leaf of each individual (one leaf per individual), allowing for the examination of each parameter relative to others. Additionally, the data set contains a number of covariates for the plants measured. Covariate data include (1) leaf-level traits (leaf mass, leaf area, leaf nitrogen and carbon content, predawn leaf water potential), (2) plant-level traits (plant height for herbaceous individuals and diameter at breast height for trees), (3) soil moisture at the time of measurement, (4) air temperature from nearby weather stations for the day of measurement and each of the 90 d prior to measurement, and (5) climate data (growing season mean temperature, precipitation, photosynthetically active radiation, vapor pressure deficit, and aridity index). We hope that the data will be useful for obtaining greater understanding of the abiotic and biotic determinants of these important biochemical parameters and for evaluating and improving large-scale models of leaf carbon exchange. © 2017 by the Ecological Society of America.

Height-related changes in leaf photosynthetic traits in diverse Bornean tropical rain forest trees.

PubMed

Kenzo, Tanaka; Inoue, Yuta; Yoshimura, Mitsunori; Yamashita, Megumi; Tanaka-Oda, Ayumi; Ichie, Tomoaki

2015-01-01

Knowledge of variations in morphophysiological leaf traits with forest height is essential for quantifying carbon and water fluxes from forest ecosystems. Here, we examined changes in leaf traits with forest height in diverse tree species and their role in environmental acclimation in a tropical rain forest in Borneo that does not experience dry spells. Height-related changes in leaf physiological and morphological traits [e.g., maximum photosynthetic rate (Amax), stomatal conductance (gs), dark respiration rate (Rd), carbon isotope ratio (δ(13)C), nitrogen (N) content, and leaf mass per area (LMA)] from understory to emergent trees were investigated in 104 species in 29 families. We found that many leaf area-based physiological traits (e.g., A(max-area), Rd, gs), N, δ(13)C, and LMA increased linearly with tree height, while leaf mass-based physiological traits (e.g., A(max-mass)) only increased slightly. These patterns differed from other biomes such as temperate and tropical dry forests, where trees usually show decreased photosynthetic capacity (e.g., A(max-area), A(max-mass)) with height. Increases in photosynthetic capacity, LMA, and δ(13)C are favored under bright and dry upper canopy conditions with higher photosynthetic productivity and drought tolerance, whereas lower R d and LMA may improve shade tolerance in lower canopy trees. Rapid recovery of leaf midday water potential to theoretical gravity potential during the night supports the idea that the majority of trees do not suffer from strong drought stress. Overall, leaf area-based photosynthetic traits were associated with tree height and the degree of leaf drought stress, even in diverse tropical rain forest trees.

Leaf gas exchange characteristics of three neotropical mangrove species in response to varying hydroperiod

USGS Publications Warehouse

Krauss, Ken W.; Twilley, Robert R.; Doyle, Thomas W.; Gardiner, Emile S.

2006-01-01

We determined how different hydroperiods affected leaf gas exchange characteristics of greenhouse-grown seedlings (2002) and saplings (2003) of the mangrove species Avicennia germinans (L.) Stearn., Laguncularia racemosa (L.) Gaertn. f., and Rhizophora mangle L. Hydroperiod treatments included no flooding (unflooded), intermittent flooding (intermittent), and permanent flooding (flooded). Plants in the intermittent treatment were measured under both flooded and drained states and compared separately. In the greenhouse study, plants of all species maintained different leaf areas in the contrasting hydroperiods during both years. Assimilation–light response curves indicated that the different hydroperiods had little effect on leaf gas exchange characteristics in either seedlings or saplings. However, short-term intermittent flooding for between 6 and 22 days caused a 20% reduction in maximum leaf-level carbon assimilation rate, a 51% lower light requirement to attain 50% of maximum assimilation, and a 38% higher demand from dark respiration. Although interspecific differences were evident for nearly all measured parameters in both years, there was little consistency in ranking of the interspecific responses. Species by hydroperiod interactions were significant only for sapling leaf area. In a field study, R. mangle saplings along the Shark River in the Everglades National Park either demonstrated no significant effect or slight enhancement of carbon assimilation and water-use efficiency while flooded. We obtained little evidence that contrasting hydroperiods affect leaf gas exchange characteristics of mangrove seedlings or saplings over long time intervals; however, intermittent flooding may cause short-term depressions in leaf gas exchange. The resilience of mangrove systems to flooding, as demonstrated in the permanently flooded treatments, will likely promote photosynthetic and morphological adjustment to slight hydroperiod shifts in many settings..

High-Throughput Phenotyping of Maize Leaf Physiological and Biochemical Traits Using Hyperspectral Reflectance1[OPEN

PubMed Central

Yendrek, Craig R.; Tomaz, Tiago; Montes, Christopher M.; Cao, Youyuan; Morse, Alison M.; Brown, Patrick J.; McIntyre, Lauren M.; Leakey, Andrew D.B.

2017-01-01

High-throughput, noninvasive field phenotyping has revealed genetic variation in crop morphological, developmental, and agronomic traits, but rapid measurements of the underlying physiological and biochemical traits are needed to fully understand genetic variation in plant-environment interactions. This study tested the application of leaf hyperspectral reflectance (λ = 500–2,400 nm) as a high-throughput phenotyping approach for rapid and accurate assessment of leaf photosynthetic and biochemical traits in maize (Zea mays). Leaf traits were measured with standard wet-laboratory and gas-exchange approaches alongside measurements of leaf reflectance. Partial least-squares regression was used to develop a measure of leaf chlorophyll content, nitrogen content, sucrose content, specific leaf area, maximum rate of phosphoenolpyruvate carboxylation, [CO2]-saturated rate of photosynthesis, and leaf oxygen radical absorbance capacity from leaf reflectance spectra. Partial least-squares regression models accurately predicted five out of seven traits and were more accurate than previously used simple spectral indices for leaf chlorophyll, nitrogen content, and specific leaf area. Correlations among leaf traits and statistical inferences about differences among genotypes and treatments were similar for measured and modeled data. The hyperspectral reflectance approach to phenotyping was dramatically faster than traditional measurements, enabling over 1,000 rows to be phenotyped during midday hours over just 2 to 4 d, and offers a nondestructive method to accurately assess physiological and biochemical trait responses to environmental stress. PMID:28049858

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maurer, K. D.; Bohrer, G.; Kenny, W. T.

Surface roughness parameters, namely the roughness length and displacement height, are an integral input used to model surface fluxes. However, most models assume these parameters to be a fixed property of plant functional type and disregard the governing structural heterogeneity and dynamics. In this study, we use large-eddy simulations to explore, in silico, the effects of canopy-structure characteristics on surface roughness parameters. We performed a virtual experiment to test the sensitivity of resolved surface roughness to four axes of canopy structure: (1) leaf area index, (2) the vertical profile of leaf density, (3) canopy height, and (4) canopy gap fraction.more » We found roughness parameters to be highly variable, but uncovered positive relationships between displacement height and maximum canopy height, aerodynamic canopy height and maximum canopy height and leaf area index, and eddy-penetration depth and gap fraction. We also found negative relationships between aerodynamic canopy height and gap fraction, as well as between eddy-penetration depth and maximum canopy height and leaf area index. We generalized our model results into a virtual "biometric" parameterization that relates roughness length and displacement height to canopy height, leaf area index, and gap fraction. Using a decade of wind and canopy-structure observations in a site in Michigan, we tested the effectiveness of our model-driven biometric parameterization approach in predicting the friction velocity over heterogeneous and disturbed canopies. We compared the accuracy of these predictions with the friction-velocity predictions obtained from the common simple approximation related to canopy height, the values calculated with large-eddy simulations of the explicit canopy structure as measured by airborne and ground-based lidar, two other parameterization approaches that utilize varying canopy-structure inputs, and the annual and decadal means of the surface roughness parameters at the site from meteorological observations. We found that the classical representation of constant roughness parameters (in space and time) as a fraction of canopy height performed relatively well. Nonetheless, of the approaches we tested, most of the empirical approaches that incorporate seasonal and interannual variation of roughness length and displacement height as a function of the dynamics of canopy structure produced more precise and less biased estimates for friction velocity than models with temporally invariable parameters.« less

[Effects of canopy position and leaf age on photosynthesis and transpiration of Pinus koraiensis].

PubMed

Huo, Hong; Wang, Chuan-kuan

2007-06-01

The photosynthesis and transpiration of Pinus koraiensis needles at different canopy positions and of different leaf ages were measured in the field with a Li-6400 portable CO2/H2O infrared gas analyzer. The results showed that canopy position and leaf age had significant effects on the maximum net photosynthetic rate (Pmax), light saturation point (LSP), light compensation point (LCP), maximum apparent quantum efficiency (alpha), transpiration rate (T(r)), and specific leaf area (SLA), but no effects on water use efficiency (WUE). The Pmax decreased with the decrease of canopy position and the increase of leaf age, ranging in 6.55-9.05 micromol.m(-2).s(-1) on average. There were great variations in LSP and LCP among different canopy positions and leaf ages. The needles at middle canopy position had the greatest capacity of utilizing both weak and strong radiation. The T(r) decreased with canopy position decreasing, and varied from 1.37 to 1.59 mmol.m(-2).s(-1) across different leaf ages. There was a significant positive correlation between T(r) and photosynthetically active radiation (R2 = 0.967), and between WUE and net photosynthetic rate (R2 = 0.860). The SLA decreased with canopy position and leaf age increasing, ranging in 6.61-8.41 m2.kg(-1) and 6.65-8.38 m2.kg(-1), respectively.

Coordination of physiological and structural traits in Amazon forest trees

NASA Astrophysics Data System (ADS)

Patiño, S.; Fyllas, N. M.; Baker, T. R.; Paiva, R.; Quesada, C. A.; Santos, A. J. B.; Schwarz, M.; Ter Steege, H.; Phillips, O. L.; Lloyd, J.

2012-02-01

Many plant traits covary in a non-random manner reflecting interdependencies associated with "ecological strategy" dimensions. To understand how plants integrate their structural and physiological investments, data on leaf and leaflet size and the ratio of leaf area to sapwood area (ΦLS) obtained for 1020 individual trees (encompassing 661 species) located in 52 tropical forest plots across the Amazon Basin were incorporated into an analysis utilising existing data on species maximum height (Hmax), seed size, leaf mass per unit area (MA), foliar nutrients and δ13C, and branch xylem density (ρx). Utilising a common principal components approach allowing eigenvalues to vary between two soil fertility dependent species groups, five taxonomically controlled trait dimensions were identified. The first involves primarily cations, foliar carbon and MA and is associated with differences in foliar construction costs. The second relates to some components of the classic "leaf economic spectrum", but with increased individual leaf areas and a higher ΦLS newly identified components for tropical tree species. The third relates primarily to increasing Hmax and hence variations in light acquisition strategy involving greater MA, reductions in ΦLS and less negative δ13C. Although these first three dimensions were more important for species from high fertility sites the final two dimensions were more important for low fertility species and were associated with variations linked to reproductive and shade tolerance strategies. Environmental conditions influenced structural traits with ρx of individual species decreasing with increased soil fertility and higher temperatures. This soil fertility response appears to be synchronised with increases in foliar nutrient concentrations and reductions in foliar [C]. Leaf and leaflet area and ΦLS were less responsive to the environment than ρx. Thus, although genetically determined foliar traits such as those associated with leaf construction costs coordinate independently of structural characteristics such as maximum height, others such as the classical "leaf economic spectrum" covary with structural traits such as leaf size and ΦLS. Coordinated structural and physiological adaptions are also associated with light acquisition/shade tolerance strategies with several traits such as MA and [C] being significant components of more than one ecological strategy dimension. This is argued to be a consequence of a range of different potential underlying causes for any observed variation in such "ambiguous" traits. Environmental effects on structural and physiological characteristics are also coordinated but in a different way to the gamut of linkages associated with genotypic differences.

Height-related trends in leaf xylem anatomy and shoot hydraulic characteristics in a tall conifer: safety versus efficiency in water transport

Treesearch

D.R. Woodruff; F.C. Meinzer; B. Lachenbruch

2008-01-01

Growth and aboveground biomass accumulation follow a common pattern as tree size increases, with productivity peaking when leaf area reaches its maximum and then declining as tree age and size increase. Age- and size-related declines in forest productivity are major considerations in setting the rotational age of commercial forests, and relate to issues of carbon...

Growth maximization trumps maintenance of leaf conductance in the tallest angiosperm.

PubMed

Koch, George W; Sillett, Stephen C; Antoine, Marie E; Williams, Cameron B

2015-02-01

Structural and physiological changes that occur as trees grow taller are associated with increased hydraulic constraints on leaf gas exchange, yet it is unclear if leaf-level constraints influence whole-tree growth as trees approach their maximum size. We examined variation in leaf physiology, leaf area to sapwood area ratio (L/S), and annual aboveground growth across a range of tree heights in Eucalyptus regnans. Leaf photosynthetic capacity did not differ among upper crown leaves of individuals 61.1-92.4 m tall. Maximum daily and integrated diurnal stomatal conductance (g s) averaged 36 and 34% higher, respectively, in upper crown leaves of ~60-m-tall, 80-year-old trees than in ~90-m-tall, 300-year-old trees, with larger differences observed on days with a high vapor pressure deficit (VPD). Greater stomatal regulation in taller trees resulted in similar minimum daily leaf water potentials (Ψ L) in shorter and taller trees over a broad range of VPDs. The long-term stomatal limitation on photosynthesis, as inferred from leaf δ (13)C composition, was also greater in taller trees. The δ (13)C of wood indicated that the bulk of photosynthesis used to fuel wood production in the main trunk and branches occurred in the upper crown. L/S increased with tree height, especially after accounting for size-independent variation in crown structure across 27 trees up to 99.8 m tall. Despite greater stomatal limitation of leaf photosynthesis in taller trees, total L explained 95% of the variation in annual aboveground biomass growth among 15 trees measured for annual biomass growth increment in 2006. Our results support a theoretical model proposing that, in the face of increasing hydraulic constraints with height, whole-tree growth is maximized by a resource trade-off that increases L to maximize light capture rather than by reducing L/S to sustain g s.

Influence of irrigation and fertilization on transpiration and hydraulic properties of Populus deltoides.

PubMed

Samuelson, Lisa J; Stokes, Thomas A; Coleman, Mark D

2007-05-01

Long-term hydraulic acclimation to resource availability was explored in 3-year-old Populus deltoides Bartr. ex Marsh. clones by examining transpiration, leaf-specific hydraulic conductance (G(L)), canopy stomatal conductance (G(S)) and leaf to sapwood area ratio (A(L):A(S)) in response to irrigation (13 and 551 mm year(-1) in addition to ambient precipitation) and fertilization (0 and 120 kg N ha(-1) year(-1)). Sap flow was measured continuously over one growing season with thermal dissipation probes. Fertilization had a greater effect on growth and hydraulic properties than irrigation, and fertilization effects were independent of irrigation treatment. Transpiration on a ground area basis (E) ranged between 0.3 and 1.8 mm day(-1), and increased 66% and 90% in response to irrigation and fertilization, respectively. Increases in G(L), G(S) at a reference vapor pressure deficit of 1 kPa, and transpiration per unit leaf area in response to increases in resource availability were associated with reductions in A(L):A(S) and consequently a minimal change in the water potential gradient from soil to leaf. Irrigation and fertilization increased leaf area index similarly, from an average 1.16 in control stands to 1.45, but sapwood area was increased from 4.0 to 6.3 m(2) ha(-1) by irrigation and from 3.7 to 6.7 m(2) ha(-1) by fertilization. The balance between leaf area and sapwood area was important in understanding long-term hydraulic acclimation to resource availability and mechanisms controlling maximum productivity in Populus deltoides.

Seasonal patterns of leaf gas exchange and water relations in dry rain forest trees of contrasting leaf phenology.

PubMed

Choat, Brendan; Ball, Marilyn C; Luly, Jon G; Donnelly, Christine F; Holtum, Joseph A M

2006-05-01

Diurnal and seasonal patterns of leaf gas exchange and water relations were examined in tree species of contrasting leaf phenology growing in a seasonally dry tropical rain forest in north-eastern Australia. Two drought-deciduous species, Brachychiton australis (Schott and Endl.) A. Terracc. and Cochlospermum gillivraei Benth., and two evergreen species, Alphitonia excelsa (Fenzal) Benth. and Austromyrtus bidwillii (Benth.) Burret. were studied. The deciduous species had higher specific leaf areas and maximum photosynthetic rates per leaf dry mass in the wet season than the evergreens. During the transition from wet season to dry season, total canopy area was reduced by 70-90% in the deciduous species and stomatal conductance (g(s)) and assimilation rate (A) were markedly lower in the remaining leaves. Deciduous species maintained daytime leaf water potentials (Psi(L)) at close to or above wet season values by a combination of stomatal regulation and reduction in leaf area. Thus, the timing of leaf drop in deciduous species was not associated with large negative values of daytime Psi(L) (greater than -1.6 MPa) or predawn Psi(L) (greater than -1.0 MPa). The deciduous species appeared sensitive to small perturbations in soil and leaf water status that signalled the onset of drought. The evergreen species were less sensitive to the onset of drought and g(s) values were not significantly lower during the transitional period. In the dry season, the evergreen species maintained their canopies despite increasing water-stress; however, unlike Eucalyptus species from northern Australian savannas, A and g(s) were significantly lower than wet season values.

Leaf morphology shift linked to climate change.

PubMed

Guerin, Greg R; Wen, Haixia; Lowe, Andrew J

2012-10-23

Climate change is driving adaptive shifts within species, but research on plants has been focused on phenology. Leaf morphology has demonstrated links with climate and varies within species along climate gradients. We predicted that, given within-species variation along a climate gradient, a morphological shift should have occurred over time due to climate change. We tested this prediction, taking advantage of latitudinal and altitudinal variations within the Adelaide Geosyncline region, South Australia, historical herbarium specimens (n = 255) and field sampling (n = 274). Leaf width in the study taxon, Dodonaea viscosa subsp. angustissima, was negatively correlated with latitude regionally, and leaf area was negatively correlated with altitude locally. Analysis of herbarium specimens revealed a 2 mm decrease in leaf width (total range 1-9 mm) over 127 years across the region. The results are consistent with a morphological response to contemporary climate change. We conclude that leaf width is linked to maximum temperature regionally (latitude gradient) and leaf area to minimum temperature locally (altitude gradient). These data indicate a morphological shift consistent with a direct response to climate change and could inform provenance selection for restoration with further investigation of the genetic basis and adaptive significance of observed variation.

Arbuscular mycorrhizal fungi improve photosynthetic energy use efficiency and decrease foliar construction cost under recurrent water deficit in woody evergreen species.

PubMed

Barros, Vanessa; Frosi, Gabriella; Santos, Mariana; Ramos, Diego Gomes; Falcão, Hiram Marinho; Santos, Mauro Guida

2018-06-01

Plants suffer recurrent cycles of water deficit in semiarid regions and have several mechanisms to tolerate low water availability. Thus, arbuscular mycorrhizal fungi (AMF) can alleviate deleterious effects of stress. In this study, Cynophalla flexuosa plants, a woody evergreen species from semiarid, when associated with AMF were exposed to two consecutive cycles of water deficit. Leaf primary metabolism, specific leaf area (SLA), leaf construction cost (CC) and photosynthetic energy use efficiency (PEUE) were measured. The maximum stress occurred on seven days (cycle 1) and ten days (cycle 2) after suspending irrigation (photosynthesis close to zero). The rehydration was performed for three days after each maximum stress. In both cycles, plants submitted to water deficit showed reduced gas exchange and leaf relative water content. However, Drought + AMF plants had significantly larger leaf relative water content in cycle 2. At cycle 1, the SLA was larger in non-inoculated plants, while CC was higher in inoculated plants. At cycle 2, Drought + AMF treatment had lower CC and large SLA compared to control, and high PEUE compared to Drought plants. These responses suggest AMFs increase tolerance of C. flexuosa to recurrent water deficit, mainly in cycle 2, reducing the CC, promoting the improvement of SLA and PEUE, leading to higher photosynthetic area. Thus, our result emphasizes the importance of studies on recurrence of water deficit, a common condition in semiarid environments. Copyright © 2018 Elsevier Masson SAS. All rights reserved.

Dominant Species in Subtropical Forests Could Decrease Photosynthetic N Allocation to Carboxylation and Bioenergetics and Enhance Leaf Construction Costs during Forest Succession

PubMed Central

Xiao, Yihua; Liu, Shirong; Tong, Fuchun; Chen, Bufeng; Kuang, Yuanwen

2018-01-01

It is important to understand how eco-physiological characteristics shift in forests when elucidating the mechanisms underlying species replacement and the process of succession and stabilization. In this study, the dominant species at three typical successional stages (early-, mid-, and late-succession) in the subtropical forests of China were selected. At each stage, we compared the leaf construction costs (CC), payback time (PBT), leaf area based N content (NA), maximum CO2 assimilation rate (Pmax), specific leaf area (SLA), photosynthetic nitrogen use efficiency (PNUE), and leaf N allocated to carboxylation (NC), and to bioenergetics (NB). The relationships between these leaf functional traits were also determined. The results showed that the early-succession forest is characterized with significantly lower leaf CC, PBT, NA, but higher Pmax, SLA, PNUE, NC, and NB, in relation to the late-succession forest. From the early- to the late-succession forests, the relationship between Pmax and leaf CC strengthened, whereas the relationships between NB, NC, PNUE, and leaf CC weakened. Thus, the dominant species are able to decrease the allocation of the photosynthetic N fraction to carboxylation and bioenergetics during forest succession. The shift in these leaf functional traits and their linkages might represent a fundamental physiological mechanism that occurs during forest succession and stabilization. PMID:29472939

Dominant Species in Subtropical Forests Could Decrease Photosynthetic N Allocation to Carboxylation and Bioenergetics and Enhance Leaf Construction Costs during Forest Succession.

PubMed

Xiao, Yihua; Liu, Shirong; Tong, Fuchun; Chen, Bufeng; Kuang, Yuanwen

2018-01-01

It is important to understand how eco-physiological characteristics shift in forests when elucidating the mechanisms underlying species replacement and the process of succession and stabilization. In this study, the dominant species at three typical successional stages (early-, mid-, and late-succession) in the subtropical forests of China were selected. At each stage, we compared the leaf construction costs (CC), payback time (PBT), leaf area based N content ( N A ), maximum CO 2 assimilation rate ( P max ), specific leaf area (SLA), photosynthetic nitrogen use efficiency (PNUE), and leaf N allocated to carboxylation ( N C ), and to bioenergetics ( N B ). The relationships between these leaf functional traits were also determined. The results showed that the early-succession forest is characterized with significantly lower leaf CC, PBT, N A , but higher P max , SLA, PNUE, N C , and N B , in relation to the late-succession forest. From the early- to the late-succession forests, the relationship between P max and leaf CC strengthened, whereas the relationships between N B , N C , PNUE, and leaf CC weakened. Thus, the dominant species are able to decrease the allocation of the photosynthetic N fraction to carboxylation and bioenergetics during forest succession. The shift in these leaf functional traits and their linkages might represent a fundamental physiological mechanism that occurs during forest succession and stabilization.

High doses of ethylenediurea (EDU) as soil drenches did not increase leaf N content or cause phytotoxicity in willow grown in fertile soil.

PubMed

Agathokleous, Evgenios; Paoletti, Elena; Manning, William J; Kitao, Mitsutoshi; Saitanis, Costas J; Koike, Takayoshi

2018-01-01

Ground-level ozone (O 3 ) levels are nowadays elevated in wide regions of the Earth, causing significant effects on plants that finally lead to suppressed productivity and yield losses. Ethylenediurea (EDU) is a chemical compound which is widely used in research projects as phytoprotectant against O 3 injury. The EDU mode of action remains still unclear, while there are indications that EDU may contribute to plants with nitrogen (N) when the soil is poor in N and the plants have relatively small leaf area. To reveal whether the N content of EDU acts as a fertilizer to plants when the soil is not poor in N and the plants have relatively large total plant leaf area, willow plants (Salix sachalinensis Fr. Schm) were exposed to low ambient O 3 levels and treated ten times (9-day interval) with 200mL soil drench containing 0, 800 or 1600mg EDU L -1 . Fertilizer was added to a nutrient-poor soil, and the plants had an average plant leaf area of 9.1m 2 at the beginning of EDU treatments. Indications for EDU-induced hormesis in maximum electron transport rate (J max ) and ratio of intercellular to ambient CO 2 concentration (C i :C a ) were observed at the end of the experiment. No other EDU-induced effects on leaf greenness and N content, maximum quantum yield of photosystem II (F v /F m ), gas exchange, growth and matter production suggest that EDU did not act as N fertilizer and did not cause toxicity under these experimental conditions. Copyright © 2017 Elsevier Inc. All rights reserved.

Leaf photoacclimatory responses of the tropical seagrass Thalassia testudinum under mesocosm conditions: a mechanistic scaling-up study.

PubMed

Cayabyab, Napo M; Enríquez, Susana

2007-01-01

Here, the leaf photoacclimatory plasticity and efficiency of the tropical seagrass Thalassia testudinum were examined. Mesocosms were used to compare the variability induced by three light conditions, two leaf sections and the variability observed at the collection site. The study revealed an efficient photosynthetic light use at low irradiances, but limited photoacclimatory plasticity to increase maximum photosynthetic rates (P(max)) and saturation (E(k)) and compensation (E(c)) irradiances under high light irradiance. A strong, positive and linear association between the percentage of daylight hours above saturation and the relative maximum photochemical efficiency (F(V)/F(M)) reduction observed between basal and apical leaf sections was also found. The results indicate that T. testudinum leaves have a shade-adapted physiology. However, the large amount of heterotrophic biomass that this seagrass maintains may considerably increase plant respiratory demands and their minimum quantum requirements for growth (MQR). Although the MQR still needs to be quantified, it is hypothesized that the ecological success of this climax species in the oligotrophic and highly illuminated waters of the Caribbean may rely on the ability of the canopy to regulate the optimal leaf light environment and the morphological plasticity of the whole plant to enhance total leaf area and to reduce carbon respiratory losses.

Relation of Stem Diameter, Branch Basal Area, and Leaf Biomass in Rapidly Growing Loblolly Pine

Treesearch

Thomas M. Williams; Charles A. Gresham

2004-01-01

Twenty loblolly pines, growing in International Paper’s maximum growth experiment at Bainbridge GA, were destructively sampled at the end of the sixth growing season. Ten trees in the control and 10 in the maximum treatment were sampled. All trees were planted at a 2.4- by 3.6-m spacing and grown with complete competition control. The maximum trees also received...

Modelling temporal and large-scale spatial variability of soil respiration from soil water availability, temperature and vegetation productivity indices

NASA Astrophysics Data System (ADS)

Reichstein, M.; Rey, A.; Freibauer, A.; Tenhunen, J.; Valentini, R.; Soil Respiration Synthesis Team

2003-04-01

Field-chamber measurements of soil respiration from 17 different forest and shrubland sites in Europe and North America were summarized and analyzed with the goal to develop a model describing seasonal, inter-annual and spatial variability of soil respiration as affected by water availability, temperature and site properties. The analysis was performed at a daily and at a monthly time step. With the daily time step, the relative soil water content in the upper soil layer expressed as a fraction of field capacity was a good predictor of soil respiration at all sites. Among the site variables tested, those related to site productivity (e.g. leaf area index) correlated significantly with soil respiration, while carbon pool variables like standing biomass or the litter and soil carbon stocks did not show a clear relationship with soil respiration. Furthermore, it was evidenced that the effect of precipitation on soil respiration stretched beyond its direct effect via soil moisture. A general statistical non-linear regression model was developed to describe soil respiration as dependent on soil temperature, soil water content and site-specific maximum leaf area index. The model explained nearly two thirds of the temporal and inter-site variability of soil respiration with a mean absolute error of 0.82 µmol m-2 s-1. The parameterised model exhibits the following principal properties: 1) At a relative amount of upper-layer soil water of 16% of field capacity half-maximal soil respiration rates are reached. 2) The apparent temperature sensitivity of soil respiration measured as Q10 varies between 1 and 5 depending on soil temperature and water content. 3) Soil respiration under reference moisture and temperature conditions is linearly related to maximum site leaf area index. At a monthly time-scale we employed the approach by Raich et al. (2002, Global Change Biol. 8, 800-812) that used monthly precipitation and air temperature to globally predict soil respiration (T&P-model). While this model was able to explain some of the month-to-month variability of soil respiration, it failed to capture the inter-site variability, regardless whether the original or a new optimized model parameterization was used. In both cases, the residuals were strongly related to maximum site leaf area index. Thus, for a monthly time scale we developed a simple T&P&LAI-model that includes leaf area index as an additional predictor of soil respiration. This extended but still simple model performed nearly as well as the more detailed time-step model and explained 50 % of the overall and 65% of the site-to-site variability. Consequently, better estimates of globally distributed soil respiration should be obtained with the new model driven by satellite estimates of leaf area index.

Estimates of leaf area index from spectral reflectance of wheat under different cultural practices and solar angle

NASA Technical Reports Server (NTRS)

Asrar, G.; Kanemasu, E. T.; Yoshida, M.

1985-01-01

The influence of management practices and solar illumination angle on the leaf area index (LAI) was estimated from measurements of wheat canopy reflectance evaluated by two methods, a regression formula and an indirect technique. The date of planting and the time of irrigation in relation to the stage of plant growth were found to have significant effects on the development of leaves in spring wheat. A reduction in soil moisture adversely affected both the duration and magnitude of the maximum LAI for late planting dates. In general, water stress during vegetative stages resulted in a reduction in maximum LAI, while water stress during the reproductive period shortened the duration of green LAI in spring wheat. Canopy geometry and solar angle also affected the spectral properties of the canopies, and hence the estimated LAI. Increase in solar zenith angles resulted in a general increase in estimated LAI obtained from both methods.

Are trait-growth models transferable? Predicting multi-species growth trajectories between ecosystems using plant functional traits

PubMed Central

Vesk, Peter A.

2017-01-01

Plant functional traits are increasingly used to generalize across species, however few examples exist of predictions from trait-based models being evaluated in new species or new places. Can we use functional traits to predict growth of unknown species in different areas? We used three independently collected datasets, each containing data on heights of individuals from non-resprouting species over a chronosquence of time-since-fire sites from three ecosystems in south-eastern Australia. We examined the influence of specific leaf area, woody density, seed size and leaf nitrogen content on three aspects of plant growth; maximum relative growth rate, age at maximum growth and asymptotic height. We tested our capacity to perform out-of-sample prediction of growth trajectories between ecosystems using species functional traits. We found strong trait-growth relationships in one of the datasets; whereby species with low SLA achieved the greatest asymptotic heights, species with high leaf-nitrogen content achieved relatively fast growth rates, and species with low seed mass reached their time of maximum growth early. However these same growth-trait relationships did not hold across the two other datasets, making accurate prediction from one dataset to another unachievable. We believe there is evidence to suggest that growth trajectories themselves may be fundamentally different between ecosystems and that trait-height-growth relationships may change over environmental gradients. PMID:28486535

Stem and leaf hydraulics of congeneric tree species from adjacent tropical savanna and forest ecosystems.

PubMed

Hao, Guang-You; Hoffmann, William A; Scholz, Fabian G; Bucci, Sandra J; Meinzer, Frederick C; Franco, Augusto C; Cao, Kun-Fang; Goldstein, Guillermo

2008-03-01

Leaf and stem functional traits related to plant water relations were studied for six congeneric species pairs, each composed of one tree species typical of savanna habitats and another typical of adjacent forest habitats, to determine whether there were intrinsic differences in plant hydraulics between these two functional types. Only individuals growing in savanna habitats were studied. Most stem traits, including wood density, the xylem water potential at 50% loss of hydraulic conductivity, sapwood area specific conductivity, and leaf area specific conductivity did not differ significantly between savanna and forest species. However, maximum leaf hydraulic conductance (K (leaf)) and leaf capacitance tended to be higher in savanna species. Predawn leaf water potential and leaf mass per area were also higher in savanna species in all congeneric pairs. Hydraulic vulnerability curves of stems and leaves indicated that leaves were more vulnerable to drought-induced cavitation than terminal branches regardless of genus. The midday K (leaf) values estimated from leaf vulnerability curves were very low implying that daily embolism repair may occur in leaves. An electric circuit analog model predicted that, compared to forest species, savanna species took longer for their leaf water potentials to drop from predawn values to values corresponding to 50% loss of K (leaf) or to the turgor loss points, suggesting that savanna species were more buffered from changes in leaf water potential. The results of this study suggest that the relative success of savanna over forest species in savanna is related in part to their ability to cope with drought, which is determined more by leaf than by stem hydraulic traits. Variation among genera accounted for a large proportion of the total variance in most traits, which indicates that, despite different selective pressures in savanna and forest habitats, phylogeny has a stronger effect than habitat in determining most hydraulic traits.

Co-regulation of photosynthetic capacity by nitrogen, phosphorus and magnesium in a subtropical Karst forest in China.

PubMed

Wang, Jing; Wen, Xuefa; Zhang, Xinyu; Li, Shenggong; Zhang, Da-Yong

2018-05-09

Leaf photosynthetic capacity is mainly constrained by nitrogen (N) and phosphorus (P). Little attention has been given to the photosynthetic capacity of mature forests with high calcium (Ca) and magnesium (Mg) in the Karst critical zone. We measured light-saturated net photosynthesis (A sat ), photosynthetic capacity (maximum carboxylation rate [V cmax ], and maximum electron transport rate [J max ]) as well as leaf nutrient contents (N, P, Ca, Mg, potassium [K], and sodium [Na]), leaf mass per area (LMA), and leaf thickness (LT) in 63 dominant plants in a mature subtropical forest in the Karst critical zone in southwestern China. Compared with global data, plants showed higher A sat for a given level of P. V cmax and J max were mainly co-regulated by N, P, Mg, and LT. The ratios of V cmax to N or P, and J max to N or P were significantly positively related to Mg. We speculate that the photosynthetic capacity of Karst plants can be modified by Mg because Mg can enhance photosynthetic N and P use efficiency.

Large-eddy simulations of surface roughness parameter sensitivity to canopy-structure characteristics

DOE PAGES

Maurer, K. D.; Bohrer, G.; Kenny, W. T.; ...

2015-04-30

Surface roughness parameters, namely the roughness length and displacement height, are an integral input used to model surface fluxes. However, most models assume these parameters to be a fixed property of plant functional type and disregard the governing structural heterogeneity and dynamics. In this study, we use large-eddy simulations to explore, in silico, the effects of canopy-structure characteristics on surface roughness parameters. We performed a virtual experiment to test the sensitivity of resolved surface roughness to four axes of canopy structure: (1) leaf area index, (2) the vertical profile of leaf density, (3) canopy height, and (4) canopy gap fraction.more » We found roughness parameters to be highly variable, but uncovered positive relationships between displacement height and maximum canopy height, aerodynamic canopy height and maximum canopy height and leaf area index, and eddy-penetration depth and gap fraction. We also found negative relationships between aerodynamic canopy height and gap fraction, as well as between eddy-penetration depth and maximum canopy height and leaf area index. We generalized our model results into a virtual "biometric" parameterization that relates roughness length and displacement height to canopy height, leaf area index, and gap fraction. Using a decade of wind and canopy-structure observations in a site in Michigan, we tested the effectiveness of our model-driven biometric parameterization approach in predicting the friction velocity over heterogeneous and disturbed canopies. We compared the accuracy of these predictions with the friction-velocity predictions obtained from the common simple approximation related to canopy height, the values calculated with large-eddy simulations of the explicit canopy structure as measured by airborne and ground-based lidar, two other parameterization approaches that utilize varying canopy-structure inputs, and the annual and decadal means of the surface roughness parameters at the site from meteorological observations. We found that the classical representation of constant roughness parameters (in space and time) as a fraction of canopy height performed relatively well. Nonetheless, of the approaches we tested, most of the empirical approaches that incorporate seasonal and interannual variation of roughness length and displacement height as a function of the dynamics of canopy structure produced more precise and less biased estimates for friction velocity than models with temporally invariable parameters.« less

Large-eddy simulations of surface roughness parameter sensitivity to canopy-structure characteristics

NASA Astrophysics Data System (ADS)

Maurer, K. D.; Bohrer, G.; Kenny, W. T.; Ivanov, V. Y.

2015-04-01

Surface roughness parameters, namely the roughness length and displacement height, are an integral input used to model surface fluxes. However, most models assume these parameters to be a fixed property of plant functional type and disregard the governing structural heterogeneity and dynamics. In this study, we use large-eddy simulations to explore, in silico, the effects of canopy-structure characteristics on surface roughness parameters. We performed a virtual experiment to test the sensitivity of resolved surface roughness to four axes of canopy structure: (1) leaf area index, (2) the vertical profile of leaf density, (3) canopy height, and (4) canopy gap fraction. We found roughness parameters to be highly variable, but uncovered positive relationships between displacement height and maximum canopy height, aerodynamic canopy height and maximum canopy height and leaf area index, and eddy-penetration depth and gap fraction. We also found negative relationships between aerodynamic canopy height and gap fraction, as well as between eddy-penetration depth and maximum canopy height and leaf area index. We generalized our model results into a virtual "biometric" parameterization that relates roughness length and displacement height to canopy height, leaf area index, and gap fraction. Using a decade of wind and canopy-structure observations in a site in Michigan, we tested the effectiveness of our model-driven biometric parameterization approach in predicting the friction velocity over heterogeneous and disturbed canopies. We compared the accuracy of these predictions with the friction-velocity predictions obtained from the common simple approximation related to canopy height, the values calculated with large-eddy simulations of the explicit canopy structure as measured by airborne and ground-based lidar, two other parameterization approaches that utilize varying canopy-structure inputs, and the annual and decadal means of the surface roughness parameters at the site from meteorological observations. We found that the classical representation of constant roughness parameters (in space and time) as a fraction of canopy height performed relatively well. Nonetheless, of the approaches we tested, most of the empirical approaches that incorporate seasonal and interannual variation of roughness length and displacement height as a function of the dynamics of canopy structure produced more precise and less biased estimates for friction velocity than models with temporally invariable parameters.

Evaluation and interpretation of Thematic Mapper ratios in equations for estimating corn growth parameters

NASA Technical Reports Server (NTRS)

Dardner, B. R.; Blad, B. L.; Thompson, D. R.; Henderson, K. E.

1985-01-01

Reflectance and agronomic Thematic Mapper (TM) data were analyzed to determine possible data transformations for evaluating several plant parameters of corn. Three transformation forms were used: the ratio of two TM bands, logarithms of two-band ratios, and normalized differences of two bands. Normalized differences and logarithms of two-band ratios responsed similarly in the equations for estimating the plant growth parameters evaluated in this study. Two-term equations were required to obtain the maximum predictability of percent ground cover, canopy moisture content, and total wet phytomass. Standard error of estimate values were 15-26 percent lower for two-term estimates of these parameters than for one-term estimates. The terms log(TM4/TM2) and (TM4/TM5) produced the maximum predictability for leaf area and dry green leaf weight, respectively. The middle infrared bands TM5 and TM7 are essential for maximizing predictability for all measured plant parameters except leaf area index. The estimating models were evaluated over bare soil to discriminate between equations which are statistically similar. Qualitative interpretations of the resulting prediction equations are consistent with general agronomic and remote sensing theory.

Effects of tree height on branch hydraulics, leaf structure and gas exchange in California redwoods.

PubMed

Ambrose, Anthony R; Sillett, Stephen C; Dawson, Todd E

2009-07-01

We examined changes in branch hydraulic, leaf structure and gas exchange properties in coast redwood (Sequoia sempervirens) and giant sequoia (Sequoiadendron giganteum) trees of different sizes. Leaf-specific hydraulic conductivity (k(L)) increased with height in S. sempervirens but not in S. giganteum, while xylem cavitation resistance increased with height in both species. Despite hydraulic adjustments, leaf mass per unit area (LMA) and leaf carbon isotope ratios (delta(13)C) increased, and maximum mass-based stomatal conductance (g(mass)) and photosynthesis (A(mass)) decreased with height in both species. As a result, both A(mass) and g(mass) were negatively correlated with branch hydraulic properties in S. sempervirens and uncorrelated in S. giganteum. In addition, A(mass) and g(mass) were negatively correlated with LMA in both species, which we attributed to the effects of decreasing leaf internal CO(2) conductance (g(i)). Species-level differences in wood density, LMA and area-based gas exchange capacity constrained other structural and physiological properties, with S. sempervirens exhibiting increased branch water transport efficiency and S. giganteum exhibiting increased leaf-level water-use efficiency with increasing height. Our results reveal different adaptive strategies for the two redwoods that help them compensate for constraints associated with growing taller, and reflect contrasting environmental conditions each species faces in its native habitat.

Association of tomato leaf curl Gujarat virus and tomato leaf curl Bangladesh betasatellite on papaya showing typical leaf curl symptoms in North India.

PubMed

Varun, Priyanka; Saxena, Sangeeta

2018-05-01

Papaya leaf curl is an economically important disease occurring in papaya growing tropical and subtropical areas. Papaya leaf curl virus, a begomovirus, is the main causative agent for the disease, but many other begomoviruses as well as betasatellites have also been reported on papaya leaf curl disease. Rapidly evolving host range of begomoviruses is a major issue for developing successful resistance strategies against begomoviral infection considering their expanding host range and mixed infection. In our study, we have identified the presence of begomovirus and associated satellite molecule on papaya showing severe leaf curl symptoms in Lucknow, India. Analysis of complete DNA-A component of this isolate (MG757245) revealed the highest similarity (91%) with tomato leaf curl Gujarat virus (ToLCuGuV), while sequence data of betasatellite (MG478451) showed maximum (89%) identity with tomato leaf curl Bangladesh betasatellite (ToLCuBB). This is the first report on identification of ToLCuGuV and ToLCuBB coinfecting papaya plants in Lucknow, Uttar Pradesh (India).

Modeling temporal and large-scale spatial variability of soil respiration from soil water availability, temperature and vegetation productivity indices

NASA Astrophysics Data System (ADS)

Reichstein, Markus; Rey, Ana; Freibauer, Annette; Tenhunen, John; Valentini, Riccardo; Banza, Joao; Casals, Pere; Cheng, Yufu; Grünzweig, Jose M.; Irvine, James; Joffre, Richard; Law, Beverly E.; Loustau, Denis; Miglietta, Franco; Oechel, Walter; Ourcival, Jean-Marc; Pereira, Joao S.; Peressotti, Alessandro; Ponti, Francesca; Qi, Ye; Rambal, Serge; Rayment, Mark; Romanya, Joan; Rossi, Federica; Tedeschi, Vanessa; Tirone, Giampiero; Xu, Ming; Yakir, Dan

2003-12-01

Field-chamber measurements of soil respiration from 17 different forest and shrubland sites in Europe and North America were summarized and analyzed with the goal to develop a model describing seasonal, interannual and spatial variability of soil respiration as affected by water availability, temperature, and site properties. The analysis was performed at a daily and at a monthly time step. With the daily time step, the relative soil water content in the upper soil layer expressed as a fraction of field capacity was a good predictor of soil respiration at all sites. Among the site variables tested, those related to site productivity (e.g., leaf area index) correlated significantly with soil respiration, while carbon pool variables like standing biomass or the litter and soil carbon stocks did not show a clear relationship with soil respiration. Furthermore, it was evidenced that the effect of precipitation on soil respiration stretched beyond its direct effect via soil moisture. A general statistical nonlinear regression model was developed to describe soil respiration as dependent on soil temperature, soil water content, and site-specific maximum leaf area index. The model explained nearly two thirds of the temporal and intersite variability of soil respiration with a mean absolute error of 0.82 μmol m-2 s-1. The parameterized model exhibits the following principal properties: (1) At a relative amount of upper-layer soil water of 16% of field capacity, half-maximal soil respiration rates are reached. (2) The apparent temperature sensitivity of soil respiration measured as Q10 varies between 1 and 5 depending on soil temperature and water content. (3) Soil respiration under reference moisture and temperature conditions is linearly related to maximum site leaf area index. At a monthly timescale, we employed the approach by [2002] that used monthly precipitation and air temperature to globally predict soil respiration (T&P model). While this model was able to explain some of the month-to-month variability of soil respiration, it failed to capture the intersite variability, regardless of whether the original or a new optimized model parameterization was used. In both cases, the residuals were strongly related to maximum site leaf area index. Thus, for a monthly timescale, we developed a simple T&P&LAI model that includes leaf area index as an additional predictor of soil respiration. This extended but still simple model performed nearly as well as the more detailed time step model and explained 50% of the overall and 65% of the site-to-site variability. Consequently, better estimates of globally distributed soil respiration should be obtained with the new model driven by satellite estimates of leaf area index. Before application at the continental or global scale, this approach should be further tested in boreal, cold-temperate, and tropical biomes as well as for non-woody vegetation.

Hydraulic architecture and photosynthetic capacity as constraints on release from suppression in Douglas-fir and western hemlock.

PubMed

Renninger, Heidi J; Meinzer, Frederick C; Gartner, Barbara L

2007-01-01

We compared hydraulic architecture, photosynthesis and growth in Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), a shade-intolerant species, and western hemlock (Tsuga heterophylla (Raf.) Sarg.), a shade-tolerant species, to study the temporal pattern of release from suppressive shade. In particular, we sought to determine whether hydraulic architecture or photosynthetic capacity is most important in constraining release. The study was conducted at two sites with mixed stands of 10- to 20-year-old Douglas-fir and western hemlock. At one site, the stand had been thinned allowing release of the understory trees, whereas at the other site, the stand remained unthinned. Douglas-fir had lower height growth (from 1998-2003) and lower relative height growth (height growth from 1998 to 2003/height in 1998) than western hemlock. However, relative height growth of released versus suppressed trees was higher in Douglas-fir (130%) than in western hemlock (65%), indicating that, although absolute height growth was less, Douglas-fir did release from suppression. Release seemed to be constrained initially by a limited photosynthetic capacity in both species. Five years after release, Douglas-fir trees had 14 times the leaf area and 1.5 times the leaf nitrogen concentration (N (area)) of suppressed trees. Needles of released western hemlock trees had about twice the maximum assimilation rate (A (max)) at ambient [CO(2)] as needles of suppressed trees and exhibited no photoinhibition at the highest irradiances. After release, trees increased in leaf area, leaf N concentration and overall photosynthetic capacity. Subsequently, hydraulic architecture appeared to constrain release in Douglas-fir and, to a lesser extent, in western hemlock. Released trees had significantly less negative foliar delta(13)C values than suppressed trees and showed a positive relationship between leaf area:sapwood area ratio (A (L)/A (S)) and delta(13)C, suggesting that trees with more leaf area for a given sapwood area experienced a stomatal limitation on carbon gain. Nonetheless, these changes had no significant effects on leaf specific conductivities of suppressed versus released trees of either species, but leaf specific root conductance was significantly lower in released Douglas-fir.

Growth synchrony between leaves and stems during twig development differs among plant functional types of subtropical rainforest woody species.

PubMed

Meng, Fengqun; Zhang, Guangfu; Li, Xincheng; Niklas, Karl J; Sun, Shucun

2015-06-01

During the development of woody twigs, the growth in leaf may or may not be proportional to the growth in stem. The presence or absence of a synchronicity between these two phenologies may reflect differences in life history adaptive strategies concerning carbon gain. We hypothesized that sun-adapted species are more likely to be less synchronous between growths in total leaf area (TLA) and stem length compared with shade-adapted species, with a bias in growth in stem length, and that shade-adapted species are more likely to be more synchronous between increases in individual leaf area (ILA) (leaf size) and leaf number (LN) during twig development compared with sun-adapted species, giving priority to growth of leaf size. We tested these two hypotheses by recording the phenologies of leaf emergence, leaf expansion and stem elongation during twig development for 19 evergreen woody species (including five shade-adapted understory species, six sun-adapted understory species and eight sun-adapted canopy species) in a subtropical evergreen broad-leaved forest in eastern China. We constructed indices to characterize the synchronicity between TLA and stem length (αLS) and between leaf size and leaf number (αSN) and we derived the α values from logistic functions taking the general form of A = A(max)/[1 + exp(β - αB)] (where A is the TLA or average ILA, B is the corresponding stem length or LN at a specific time, and A(max) is the maximum TLA or the maximum ILA of a twig; the higher the numerical value of α, the less synchronous the corresponding phenologies). Consistent with our hypotheses, sun-adapted species were higher both in α(LS) and α(SN), showing less synchronous patterns in the growths of TLA vs stem length and leaf size vs LN during twig development. Moreover, α(LS) and α(SN) were significantly positively correlated with relative growth rates of LN and leaf size across species, as indicated by both analyses of ordinary regression and phylogenetic generalized least squares. The across-species synchronies during twig development show that the temporal dynamics of the leaf size-twig size spectrum is of adaptive significance in plants. We suggest that temporal dynamics of plant functional traits should be extensively studied to characterize plant life history. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Preliminary validation of leaf area index sensor in Huailai

NASA Astrophysics Data System (ADS)

Cai, Erli; Li, Xiuhong; Liu, Qiang; Dou, Baocheng; Chang, Chongyan; Niu, Hailin; Lin, Xingwen; Zhang, Jialin

2015-12-01

Leaf area index (LAI) is a key variable in many land surface models that involve energy and mass exchange between vegetation and the environment. In recent years, extracting vegetation structure parameters from digital photography becomes a widely used indirect method to estimate LAI for its simplicity and ease of use. A Leaf Area Index Sensor (LAIS) system was developed to continuously monitor the growth of crops in several sampling points in Huailai, China. The system applies 3G/WIFI communication technology to remotely collect crop photos in real-time. Then the crop photos are automatically processed and LAI is estimated based on the improved leaf area index of Lang and Xiang (LAILX) algorithm in LAIS. The objective of this study is to primarily verify the LAI estimated from LAIS (Lphoto) through comparing them with the destructive green LAI (Ldest). Ldest was measured across the growing season ntil maximum canopy development while plants are still green. The preliminary verification shows that Lphoto corresponds well with the Ldest (R2=0.975). In general, LAI could be accurately estimated with LAIS and its LAI shows high consistency compared with the destructive green LAI. The continuous LAI measurement obtained from LAIS could be used for the validation of remote sensing LAI products.

Climate controls photosynthetic capacity more than leaf nitrogen contents

NASA Astrophysics Data System (ADS)

Ali, A. A.; Xu, C.; McDowell, N. G.

2013-12-01

Global vegetation models continue to lack the ability to make reliable predictions because the photosynthetic capacity varies a lot with growth conditions, season and among species. It is likely that vegetation models link photosynthetic capacity to concurrent changes in leaf nitrogen content only. To improve the predictions of the vegetation models, there is an urgent need to review species growth conditions and their seasonal response to changing climate. We sampled the global distribution of the Vcmax (maximum carboxylation rates) data of various species across different environmental gradients from the literature and standardized its value to 25 degree Celcius. We found that species explained the largest variation in (1) the photosynthetic capacity and (2) the proportion of nitrogen allocated for rubisco (PNcb). Surprisingly, climate variables explained more variations in photosynthetic capacity as well as PNcb than leaf nitrogen content and/or specific leaf area. The chief climate variables that explain variation in photosynthesis and PNcb were radiation, temperature and daylength. Our analysis suggests that species have the greatest control over photosynthesis and PNcb. Further, compared to leaf nitrogen content and/or specific leaf area, climate variables have more control over photosynthesis and PNcb. Therefore, climate variables should be incorporated in the global vegetation models when making predictions about the photosynthetic capacity.

The impact of long-term water stress on relative growth rate and morphology of needles and shoots of Metasequoia glyptostroboides seedlings: research toward identifying mechanistic models.

PubMed

Zhang, Yanxiang; Equiza, Maria Alejandra; Zheng, Quanshui; Tyree, Melvin T

2011-09-01

Leaf morphology in the upper canopy of trees tends to be different from that lower down. The effect of long-term water stress on leaf growth and morphology was studied in seedlings of Metasequoia glyptostroboides to understand how tree height might affect leaf morphology in larger trees. Tree height increases water stress on growing leaves through increased hydraulic resistance to water flow and increased gravitational potential, hence we assume that water stress imposed by soil dehydration will have an effect equivalent to stress induced by height. Seedlings were subjected to well-watered and two constant levels of long-term water stress treatments. Drought treatment significantly reduced final needle count, area and mass per area (leaf mass area, LMA) and increased needle density. Needles from water-stressed plants had lower maximum volumetric elastic modulus (ε(max)), osmotic potential at full turgor (Ψ¹⁰⁰(π)) (and at zero turgor (Ψ⁰(π)) (than those from well-watered plants. Palisade and spongy mesophyll cell size and upper epidermal cell size decreased significantly in drought treatments. Needle relative growth rate, needle length and cell sizes were linear functions of the daily average water potential at the time of leaf growth (r² 0.88-0.999). We conclude that water stress alone does mimic the direction and magnitude of changes in leaf morphology observed in tall trees. The results are discussed in terms of various models for leaf growth rate. Copyright © Physiologia Plantarum 2011.

Light-dependent leaf trait variation in 43 tropical dry forest tree species.

PubMed

Markesteijn, Lars; Poorter, Lourens; Bongers, Frans

2007-04-01

Our understanding of leaf acclimation in relation to irradiance of fully grown or juvenile trees is mainly based on research involving tropical wet forest species. We studied sun-shade plasticity of 24 leaf traits of 43 tree species in a Bolivian dry deciduous forest. Sampling was confined to small trees. For each species, leaves were taken from five of the most and five of the least illuminated crowns. Trees were selected based on the percentage of the hemisphere uncovered by other crowns. We examined leaf trait variation and the relation between trait plasticity and light demand, maximum adult stature, and ontogenetic changes in crown exposure of the species. Leaf trait variation was mainly related to differences among species and to a minor extent to differences in light availability. Traits related to the palisade layer, thickness of the outer cell wall, and N(area) and P(area) had the greatest plasticity, suggesting their importance for leaf function in different light environments. Short-lived pioneers had the highest trait plasticity. Overall plasticity was modest and rarely associated with juvenile light requirements, adult stature, or ontogenetic changes in crown exposure. Dry forest tree species had a lower light-related plasticity than wet forest species, probably because wet forests cast deeper shade. In dry forests light availability may be less limiting, and low water availability may constrain leaf trait plasticity in response to irradiance.

Mechanisms behind the estimation of photosynthesis traits from leaf reflectance observations

NASA Astrophysics Data System (ADS)

Dechant, Benjamin; Cuntz, Matthias; Doktor, Daniel; Vohland, Michael

2016-04-01

Many studies have investigated the reflectance-based estimation of leaf chlorophyll, water and dry matter contents of plants. Only few studies focused on photosynthesis traits, however. The maximum potential uptake of carbon dioxide under given environmental conditions is determined mainly by RuBisCO activity, limiting carboxylation, or the speed of photosynthetic electron transport. These two main limitations are represented by the maximum carboxylation capacity, V cmax,25, and the maximum electron transport rate, Jmax,25. These traits were estimated from leaf reflectance before but the mechanisms underlying the estimation remain rather speculative. The aim of this study was therefore to reveal the mechanisms behind reflectance-based estimation of V cmax,25 and Jmax,25. Leaf reflectance, photosynthetic response curves as well as nitrogen content per area, Narea, and leaf mass per area, LMA, were measured on 37 deciduous tree species. V cmax,25 and Jmax,25 were determined from the response curves. Partial Least Squares (PLS) regression models for the two photosynthesis traits V cmax,25 and Jmax,25 as well as Narea and LMA were studied using a cross-validation approach. Analyses of linear regression models based on Narea and other leaf traits estimated via PROSPECT inversion, PLS regression coefficients and model residuals were conducted in order to reveal the mechanisms behind the reflectance-based estimation. We found that V cmax,25 and Jmax,25 can be estimated from leaf reflectance with good to moderate accuracy for a large number of species and different light conditions. The dominant mechanism behind the estimations was the strong relationship between photosynthesis traits and leaf nitrogen content. This was concluded from very strong relationships between PLS regression coefficients, the model residuals as well as the prediction performance of Narea- based linear regression models compared to PLS regression models. While the PLS regression model for V cmax,25 was fully based on the correlation to Narea, the PLS regression model for Jmax,25 was not entirely based on it. Analyses of the contributions of different parts of the reflectance spectrum revealed that the information contributing to the Jmax,25 PLS regression model in addition to the main source of information, Narea, was mainly located in the visible part of the spectrum (500-900 nm). Estimated chlorophyll content could be excluded as potential source of this extra information. The PLS regression coefficients of the Jmax,25 model indicated possible contributions from chlorophyll fluorescence and cytochrome f content. In summary, we found that the main mechanism behind the estimation of V cmax,25 and Jmax,25 from leaf reflectance observations is the correlation to Narea but that there is additional information related to Jmax,25 mainly in the visible part of the spectrum.

Leaf morphology of 40 evergreen and deciduous broadleaved subtropical tree species and relationships to functional ecophysiological traits.

PubMed

Kröber, W; Heklau, H; Bruelheide, H

2015-03-01

We explored potential of morphological and anatomical leaf traits for predicting ecophysiological key functions in subtropical trees. We asked whether the ecophysiological parameters stomatal conductance and xylem cavitation vulnerability could be predicted from microscopy leaf traits. We investigated 21 deciduous and 19 evergreen subtropical tree species, using individuals of the same age and from the same environment in the Biodiversity-Ecosystem Functioning experiment at Jiangxi (BEF-China). Information-theoretic linear model selection was used to identify the best combination of morphological and anatomical predictors for ecophysiological functions. Leaf anatomy and morphology strongly depended on leaf habit. Evergreen species tended to have thicker leaves, thicker spongy and palisade mesophyll, more palisade mesophyll layers and a thicker subepidermis. Over 50% of all evergreen species had leaves with multi-layered palisade parenchyma, while only one deciduous species (Koelreuteria bipinnata) had this. Interactions with leaf habit were also included in best multi-predictor models for stomatal conductance (gs ) and xylem cavitation vulnerability. In addition, maximum gs was positively related to log ratio of palisade to spongy mesophyll thickness. Vapour pressure deficit (vpd) for maximum gs increased with the log ratio of palisade to spongy mesophyll thickness in species having leaves with papillae. In contrast, maximum specific hydraulic conductivity and xylem pressure at which 50% loss of maximum specific xylem hydraulic conductivity occurred (Ψ50 ) were best predicted by leaf habit and density of spongy parenchyma. Evergreen species had lower Ψ50 values and lower maximum xylem hydraulic conductivities. As hydraulic leaf and wood characteristics were reflected in structural leaf traits, there is high potential for identifying further linkages between morphological and anatomical leaf traits and ecophysiological responses. © 2014 German Botanical Society and The Royal Botanical Society of the Netherlands.

Stomatal regulation, structural acclimation and metabolic shift towards defensive compounds reduce O3 load in birch under chronic O3 stress

NASA Astrophysics Data System (ADS)

Oksanen, E.; Riikonen, J.; Kontunen-Soppela, S.; Maenpaa, M.; Rousi, M.

2009-12-01

Northern forests are encountering new threats due to continuously increasing load of oxidative stress, e.g. due to rising tropospheric O3 levels, and simultaneous climate warming, which is more intense in northern latitudes as compared to global means. The proportion of silver birch (Betula pendula) in Finnish forests is expected to increase with climate warming. Unfortunately, we have growing evidence that the vitality and the carbon sink strength of birch trees are weakened under chronic O3 stress. In this study we investigated the effects of slightly elevated O3 concentration (1.3 x the ambient), temperature (T) and their combination on the antioxidant defense, gas exchange and leaf growth of Betula pendula saplings (clone 12) growing in open-field conditions over two growing seasons. The plants were measured for SLA (specific leaf area), total leaf area, net photosynthesis (Pn), stomatal conductance (gs), maximum rate of carboxylation (Vc,max), maximum rate of electron transport (Jmax), relative stomatal limitation to photosynthesis (ls), dark respiration (Rd), apoplastic concentrations of AA (ascorbic acid), DHA (dehydroascobate) and total ascorbate, the redox state of apoplastic ascorbate, and total antioxidant capacity. Elevated O3 enhanced the total antioxidant capacity in the apoplast in the first year of the experiment at the ambient T. However, during the second year of the experiment, the saplings responded to elevated O3 level by closing the stomata and by developing leaves with a lower leaf area per mass, rather than by accumulating ascorbate in the apoplast. O3 did not affect the total leaf area, whereas Pn was slightly and gs significantly reduced in the second year. Elevated T enhanced the total leaf area, Pn and Vc,max, redox state of ascorbate and total antioxidant capacity in the apoplast. The effects of T and O3 on total leaf area and net photosynthesis were counteractive. We were not able to detect significant differences in Rd between the treatments. Our results with birch suggest that (1) apoplastic AA plays only a minor and transient role in O3 defence whereas (2) stomatal regulation and structural plasticity of leaves are more important long-term mechanisms leading to O3 avoidance in chronic O3 stress with relatively low O3 concentrations. The role of antioxidant capacity was, however, modified by temperature in a complex manner. We should also remember that the clonal differences are wide in birch responses to O3 and therefore the role of AA in scavencing ROS in the apoplast maybe more important in other birch genotypes. Our previous studies with O3-stressed birches have indicated a considerable shift in leaf metabolome towards quercetin-phenolic compounds and chlorogenic acid, which have good radical-scavencing properties, and compounds related to leaf cuticular wax layer. Therefore we can conclude that the long-term protection of birch against chronic O3 stress in mainly composed of stomatal closure, secondary compounds and structural acclimation.

Psidium guajava as a bioaccumulator of nickel around an oil refinery, southern Brazil.

PubMed

Trindade Perry, Carolina; Divan, Armando Molina; Raya Rodriguez, Maria Teresa; Lúcia Atz, Vera

2010-05-01

To evaluate the potential of Psidium guajava as a biological accumulator of air pollutants, saplings were exposed at nine sites receiving atmospheric emissions from an oil refinery (five within, four outside the industrial area) and another reference site located at the Federal University of Rio Grande do Sul, 27 km from the refinery. Exposures lasted about 3 months each, coincided with the seasons, and totaled five exposures between 2005 and 2006. The following parameters were evaluated: dry weight of leaves, stems, and roots, leaf area, rate of relative height increase, Ni and S contents, maximum assimilation rate, and carboxylation efficiency invivo. P. guajava was found to be an efficient accumulator of Ni, since highly significant differences were observed (P<0.001) between sites within the industrial area and the reference site for all periods of exposure and a significant negative correlation between distance from emission source and Ni content. The S content showed significant differences (P<0.05) only at sites within the industrial area for two exposures. The dry weight, leaf area, rate of relative height increase, maximum assimilation rate, and carboxylation efficiency did not present significant differences for any period of exposure. In view of the above, we conclude that P. guajava is a good bioaccumulator for Ni. Copyright 2009 Elsevier Inc. All rights reserved.

Successional change in photosynthetic capacities after wildfires across the North American boreal forests

NASA Astrophysics Data System (ADS)

Tahara, N.; Ueyama, M.; Iwata, H.; Ichii, K.; Harazono, Y.; Nagano, H.

2015-12-01

Wildfire is a major disturbance across the North American boreal forests. Canopy ecophysiology is important to understand recovery of carbon dioxide and water vapor fluxes after wildfires. We developed a big-leaf model coupled photosynthesis (Farquhar et al., 1980) and stomatal conductance (Ball et al., 1987) models. We inputted eddy covariance data from fire chronosequence across the North American boreal forests into the big-leaf model for optimizing parameters: maximum carboxylation rate at 25℃ (Vcmax25) and stomatal conductance parameters. The model was optimized with a global optimization technique: SCE-UA method (Duan et al., 1994). The estimated canopy-scale parameters were then downscaled into a leaf scale (vcmax25; values per sun leaf area) using a two-leaf radiation transfer model (de Pury and Farquhar, 1997) and leaf area index. We used 6 sites from two fire chronosequence in Alaska (1~, 3~, 5~, 15~ and 80~ years after fire; Liu et al., 2005; Iwata et al., 2011) and 6 sites from a Canadian chronosequence study (6~, 15~, 23~, 40~ and 74~ years after fire; Goulden et al., 2010). Preliminary results showed clear seasonal variations in canopy-scale Vcmax25 with the maximum during the summer. In Alaska, the downscaled vcmax25 for four years after fire exceeded those of mature forests, indicating that the photosynthetic capacity recovered quickly in the early successional stage. This quick recovery was not seen in gross primary productivity. We will show the variations of the ecophysiological parameters in terms of environment conditions and stand age. References Ball et al., 1987: In Progress in Photosynthesis Research, 221-224. de Pury and Farquhar, 1997: Plant, Cell and Environ., 20, 537-557. Duan et al., 1994: J. Hydrology, 158, 265-284. Farquhar et al., 1980: Planta, 149, 78-90. Goulden et al., 2010: Global Change Biol., 17, 855-871. Iwata et al., 2011: SOLA., 7, 105-108. Liu et al., 2005: J. Geophys. Res., 110, D13101.

Abiotic and biotic determinants of leaf carbon exchange capacity from tropical to high boreal biomes

NASA Astrophysics Data System (ADS)

Smith, N. G.; Dukes, J. S.

2016-12-01

Photosynthesis and respiration on land represent the two largest fluxes of carbon dioxide between the atmosphere and the Earth's surface. As such, the Earth System Models that are used to project climate change are high sensitive to these processes. Studies have found that much of this uncertainty is due to the formulation and parameterization of plant photosynthetic and respiratory capacity. Here, we quantified the abiotic and biotic factors that determine photosynthetic and respiratory capacity at large spatial scales. Specifically, we measured the maximum rate of Rubisco carboxylation (Vcmax), the maximum rate of Ribulose-1,5-bisphosphate regeneration (Jmax), and leaf dark respiration (Rd) in >600 individuals of 98 plant species from the tropical to high boreal biomes of Northern and Central America. We also measured a bevy of covariates including plant functional type, leaf nitrogen content, short- and long-term climate, leaf water potential, plant size, and leaf mass per area. We found that plant functional type and leaf nitrogen content were the primary determinants of Vcmax, Jmax, and Rd. Mean annual temperature and mean annual precipitation were not significant predictors of these rates. However, short-term climatic variables, specifically soil moisture and air temperature over the previous 25 days, were significant predictors and indicated that heat and soil moisture deficits combine to reduce photosynthetic capacity and increase respiratory capacity. Finally, these data were used as a model benchmarking tool for the Community Land Model version 4.5 (CLM 4.5). The benchmarking analyses determined errors in the leaf nitrogen allocation scheme of CLM 4.5. Under high leaf nitrogen levels within a plant type the model overestimated Vcmax and Jmax. This result suggested that plants were altering their nitrogen allocation patterns when leaf nitrogen levels were high, an effect that was not being captured by the model. These data, taken with models in mind, provide paths forward for improving model structure and parameterization of leaf carbon exchange at large spatial scales.

The relationship between tree height and leaf area: sapwood area ratio.

PubMed

McDowell, N; Barnard, H; Bond, B; Hinckley, T; Hubbard, R; Ishii, H; Köstner, B; Magnani, F; Marshall, J; Meinzer, F; Phillips, N; Ryan, M; Whitehead, D

2002-06-01

The leaf area to sapwood area ratio (A l :A s ) of trees has been hypothesized to decrease as trees become older and taller. Theory suggests that A l :A s must decrease to maintain leaf-specific hydraulic sufficiency as path length, gravity, and tortuosity constrain whole-plant hydraulic conductance. We tested the hypothesis that A l :A s declines with tree height. Whole-tree A l :A s was measured on 15 individuals of Douglas-fir (Pseudotsuga menziesii var. menziesii) ranging in height from 13 to 62 m (aged 20-450 years). A l :A s declined substantially as height increased (P=0.02). Our test of the hypothesis that A l :A s declines with tree height was extended using a combination of original and published data on nine species across a range of maximum heights and climates. Meta-analysis of 13 whole-tree studies revealed a consistent and significant reduction in A l :A s with increasing height (P<0.05). However, two species (Picea abies and Abies balsamea) exhibited an increase in A l :A s with height, although the reason for this is not clear. The slope of the relationship between A l :A s and tree height (ΔA l :A s /Δh) was unrelated to mean annual precipitation. Maximum potential height was positively correlated with ΔA l :A s /Δh. The decrease in A l :A s with increasing tree size that we observed in the majority of species may be a homeostatic mechanism that partially compensates for decreased hydraulic conductance as trees grow in height.

Variation in light-intercepting area and photosynthetic rate of sun and shade shoots of two Picea species in relation to the angle of incoming light.

PubMed

Ishii, Hiroaki; Hamada, Yoko; Utsugi, Hajime

2012-10-01

We investigated the effects of sun- and shade-shoot architecture on the photosynthetic rates of two Picea species by applying light from various angles in the laboratory. Compared with sun shoots, shade shoots were characterized by lower mass allocation per light-intercepting area, less leaf mass per shoot mass, less mutual shading among leaves and more efficient allocation of chlorophyll to photosynthesis. The shoot silhouette to total leaf area ratio (STAR(ϕ)) decreased with increasing shoot inclination angle (ϕ, the shoot axis angle relative to the projection plane) and was consistently higher for the shade shoots. Morphological and physiological characteristics of the shade shoots resulted in maximum rates of net photosynthesis at ϕ = 0° (P(max,0)) similar to that of the sun shoots when expressed on a leaf mass, total leaf area and chlorophyll basis. When the angle of incoming light was varied, P(max,ϕ) per total leaf area (P(max,ϕ )/A(T)) of the shade shoots increased linearly with increasing STAR(ϕ), while P(max,ϕ) per shoot silhouette area did not change. In contrast, the response of the sun shoots was non-linear, and an optimum angle of incoming light was determined. Our results suggest that shade-shoot morphology is adaptive for utilizing diffuse light incoming from various angles, while sun-shoot morphology is adaptive for avoiding the negative effects of strong direct radiation and for enhancing light diffusion into the canopy. We propose that the angle of incoming light should be taken into account when estimating photosynthetic rates of sun shoots of conifer trees in the field.

Some dynamics of spread and infection by aeciospores of Puccinia punctiformis, a biological control pathogen of Cirsium arvense

USDA-ARS?s Scientific Manuscript database

In this study, effective spread of aeciospores from an area source in a field was fit to an exponential decline model with a predicted maximum distance of spread of 30 m from the area source to observed uredinia on one leaf of one C. arvense shoot. However, the greatest number of shoots bearing leav...

SU-E-T-444: Gravity Effect On Maximum Leaf Speed in Dynamic IMRT Treatments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Olasolo, J; Pellejero, S; Gracia, M

Purpose: A leaf sequencing algorithm has been recently developed in our department. Our purpose is to utilize this algorithm to reduce treatment time by studying the feasibility of using several maximum leaf speeds depending on gantry angle and leaf thickness (0.5 or 1 cm at isocenter). To do so, the gravity effect on MLC performance has been examined by means of analysing the dynalog files. Methods: Leaf position errors has been ascertained according to gantry angle and leaf speed in MLC Millenium120 (Varian). In order to do this, the following test has been designed: all leaves move in synchrony, withmore » same speed and 1 cm gap between opposite leaves. This test is implemented for 18 different speeds: 0.25-0.5-0.75-1-1.25-1.5-1.75-2-2.1-2.2-2.3-2.4-2.5-2.6-2.7-2.8-2.9-3.0 cm/s and 8 gantry angles: 0-45-90-135-180-225-270-315. Collimator angle is 2 degrees in all cases since it is the most usual one in IMRT treatments in our department. Dynamic tolerance is 2 mm. Dynalogs files of 10 repetitions of the test are analysed with a Mathlab in-house developed software and RMS error and 95th percentiles are calculated. Varian recommends 2.5 cm/s as the maximum leaf speed for its segmentation algorithm. In our case, we accept this speed in the most restrictive situation: gantry angle 270 and 1 cm leaf thickness. Maximum speeds for the rest of the cases are calculated by keeping the difference between 95th percentile and dynamic tolerance. In this way, beam hold-off probability does not increase. Results: Maximum speeds every 45 degrees of gantry rotation have been calculated for both leaf thickness. These results are 2.9-2.9-2.9-2.9-2.7-2.6-2.6-2.7 cm/s for 0.5 cm leaf thickness and 2.7-2.7-2.7-2.7-2.6-2.5-2.5-2.6 cm/s for 1 cm leaf thickness. Conclusion: Gravity effect on MLC positioning has been studied. Maximum leaf speed according to leaf thickness and gantry angle have been calculated which reduces treatment time.« less

Photosystem II functionality and antioxidant system changes during leaf rolling in post-stress emerging Ctenanthe setosa exposed to drought.

PubMed

Terzi, Rabiye; Saruhan, Neslihan; Sağlam, A; Nar, Hatice; Kadioğlu, A

2009-12-01

We studied the changes in antioxidant system and chlorophyll fluorescence parameters in post-stress emerging Ctenanthe setosa (Rosc.) Eichler (Marantaceae) plants (PSE plants) having reduced leaf area under drought stress causing leaf rolling and re-watering. PSE plants were compared to primary stressed plants (PS) in previous studies. The parameters were measured at different visual leaf rolling scores from 1 to 4 (1 is unrolled, 4 is tightly rolled and the others is intermediate form). Water potentials and stomatal conductance of leaves were gradually decreased during leaf rolling. Similarly, maximum quantum efficiency of open PS II center and quantum yield of PS II decreased during the rolling period. Non-photochemical quenching of chlorophyll fluorescence decreased at score 2 then increased while photochemical quenching did not change during leaf rolling. Electron transport rate decreased only at score 4 but approximately reached to score 1 level after re-watering. Superoxide dismutase activity was not constant at all leaf rolling scores. Ascorbate peroxidase, catalase and glutathione reductase activities generally tended to increase during leaf rolling. Lipid peroxidation and H 2 O 2 content increased at score 2 but decreased at the later scores. On the other hand, O 2 .- production increased during the rolling period. After re-watering of the plants having score 4 of leaf rolling, antioxidant enzyme activities were lower than those of score 1. Other physiological parameters also tended to reach the value of score 1. The results indicated that PSE plants gained drought tolerance by reducing leaf area effectively induced their antioxidant systems and protected the photosynthesis under drought stress similar to PS plants.

Overproduction of Abscisic Acid in Tomato Increases Transpiration Efficiency and Root Hydraulic Conductivity and Influences Leaf Expansion1[OA

PubMed Central

Thompson, Andrew J.; Andrews, John; Mulholland, Barry J.; McKee, John M.T.; Hilton, Howard W.; Horridge, Jon S.; Farquhar, Graham D.; Smeeton, Rachel C.; Smillie, Ian R.A.; Black, Colin R.; Taylor, Ian B.

2007-01-01

Overexpression of genes that respond to drought stress is a seemingly attractive approach for improving drought resistance in crops. However, the consequences for both water-use efficiency and productivity must be considered if agronomic utility is sought. Here, we characterize two tomato (Solanum lycopersicum) lines (sp12 and sp5) that overexpress a gene encoding 9-cis-epoxycarotenoid dioxygenase, the enzyme that catalyzes a key rate-limiting step in abscisic acid (ABA) biosynthesis. Both lines contained more ABA than the wild type, with sp5 accumulating more than sp12. Both had higher transpiration efficiency because of their lower stomatal conductance, as demonstrated by increases in δ13C and δ18O, and also by gravimetric and gas-exchange methods. They also had greater root hydraulic conductivity. Under well-watered glasshouse conditions, mature sp5 plants were found to have a shoot biomass equal to the wild type despite their lower assimilation rate per unit leaf area. These plants also had longer petioles, larger leaf area, increased specific leaf area, and reduced leaf epinasty. When exposed to root-zone water deficits, line sp12 showed an increase in xylem ABA concentration and a reduction in stomatal conductance to the same final levels as the wild type, but from a different basal level. Indeed, the main difference between the high ABA plants and the wild type was their performance under well-watered conditions: the former conserved soil water by limiting maximum stomatal conductance per unit leaf area, but also, at least in the case of sp5, developed a canopy more suited to light interception, maximizing assimilation per plant, possibly due to improved turgor or suppression of epinasty. PMID:17277097

Overproduction of abscisic acid in tomato increases transpiration efficiency and root hydraulic conductivity and influences leaf expansion.

PubMed

Thompson, Andrew J; Andrews, John; Mulholland, Barry J; McKee, John M T; Hilton, Howard W; Horridge, Jon S; Farquhar, Graham D; Smeeton, Rachel C; Smillie, Ian R A; Black, Colin R; Taylor, Ian B

2007-04-01

Overexpression of genes that respond to drought stress is a seemingly attractive approach for improving drought resistance in crops. However, the consequences for both water-use efficiency and productivity must be considered if agronomic utility is sought. Here, we characterize two tomato (Solanum lycopersicum) lines (sp12 and sp5) that overexpress a gene encoding 9-cis-epoxycarotenoid dioxygenase, the enzyme that catalyzes a key rate-limiting step in abscisic acid (ABA) biosynthesis. Both lines contained more ABA than the wild type, with sp5 accumulating more than sp12. Both had higher transpiration efficiency because of their lower stomatal conductance, as demonstrated by increases in delta(13)C and delta(18)O, and also by gravimetric and gas-exchange methods. They also had greater root hydraulic conductivity. Under well-watered glasshouse conditions, mature sp5 plants were found to have a shoot biomass equal to the wild type despite their lower assimilation rate per unit leaf area. These plants also had longer petioles, larger leaf area, increased specific leaf area, and reduced leaf epinasty. When exposed to root-zone water deficits, line sp12 showed an increase in xylem ABA concentration and a reduction in stomatal conductance to the same final levels as the wild type, but from a different basal level. Indeed, the main difference between the high ABA plants and the wild type was their performance under well-watered conditions: the former conserved soil water by limiting maximum stomatal conductance per unit leaf area, but also, at least in the case of sp5, developed a canopy more suited to light interception, maximizing assimilation per plant, possibly due to improved turgor or suppression of epinasty.

Coordination of physiological and structural traits in Amazon forest trees

NASA Astrophysics Data System (ADS)

Patiño, S.; Fyllas, N. M.; Baker, T. R.; Paiva, R.; Quesada, C. A.; Santos, A. J. B.; Schwarz, M.; Ter Steege, H.; Phillips, O. L.; Lloyd, J.

2011-05-01

Many plant traits covary in a non-random manner reflecting interdependencies associated with "ecological strategy" dimensions. To understand how plants modulate their structural investments to best maintain and utilise their physiological capabilities, data on leaf and leaflet size and the ratio of leaf area to sapwood area (ΦLS) obtained for 1040 tree species located in 53 tropical forest plots across the Amazon Basin were incorporated into an analysis utilising existing data on species maximum height (Hmax), seed size, leaf mass per unit area (MA), foliar nutrients and δ13C and branch xylem density (ρx). Utilising a common principal components approach allowing eigenvalues to vary between two soil fertility dependent species groups, five genetically controlled trait dimensions were identified. The first involves primarily cations, foliar carbon and MA and is associated with differences in foliar construction costs. The second relates to the classic "leaf economic spectrum", but with increased individual leaf areas and a higher ΦLS newly identified components. The third relates primarily to increasing Hmax and hence variations in light acquisition strategy involving greater MA, reductions in ΦLS and less negative δ13C. Although these first three dimensions were more important for species from high fertility sites the final two dimensions were more important for low fertility species and were associated with variations linked to reproductive and shade tolerance strategies. Environmental conditions also influenced structural traits with ρx decreasing with increased soil fertility and decreasing with increased temperatures. This soil fertility response appears to be synchronised with increases in foliar nutrient concentrations and reductions in foliar [C]. Leaf and leaflet area and ΦLS were less responsive to the environment than ρx. Thus although genetically determined foliar traits such as those associated with leaf construction costs coordinate independently of structural characteristics, others tend to covary with leaf size, ΦLS, S tolerance strategies. Several traits such as MA and [C] are important components of more than one dimension with their ambiguous nature reflecting different underlying causes of variation. Environmental effects on structural and physiological characteristics are also coordinated but in a different way to the gamut of linkages associated with genotypic differences.

Photosynthesis and carbon allocation are both important predictors of genotype productivity responses to elevated CO2 in Eucalyptus camaldulensis.

PubMed

Aspinwall, Michael J; Blackman, Chris J; de Dios, Víctor Resco; Busch, Florian A; Rymer, Paul D; Loik, Michael E; Drake, John E; Pfautsch, Sebastian; Smith, Renee A; Tjoelker, Mark G; Tissue, David T

2018-05-08

Intraspecific variation in biomass production responses to elevated atmospheric carbon dioxide (eCO2) could influence tree species' ecological and evolutionary responses to climate change. However, the physiological mechanisms underlying genotypic variation in responsiveness to eCO2 remain poorly understood. In this study, we grew 17 Eucalyptus camaldulensis Dehnh. subsp. camaldulensis genotypes (representing provenances from four different climates) under ambient atmospheric CO2 and eCO2. We tested whether genotype leaf-scale photosynthetic and whole-tree carbon (C) allocation responses to eCO2 were predictive of genotype biomass production responses to eCO2. Averaged across genotypes, growth at eCO2 increased in situ leaf net photosynthesis (Anet) (29%) and leaf starch concentrations (37%). Growth at eCO2 reduced the maximum carboxylation capacity of Rubisco (-4%) and leaf nitrogen per unit area (Narea, -6%), but Narea calculated on a total non-structural carbohydrate-free basis was similar between treatments. Growth at eCO2 also increased biomass production and altered C allocation by reducing leaf area ratio (-11%) and stem mass fraction (SMF, -9%), and increasing leaf mass area (18%) and leaf mass fraction (5%). Overall, we found few significant CO2 × provenance or CO2 × genotype (within provenance) interactions. However, genotypes that showed the largest increases in total dry mass at eCO2 had larger increases in root mass fraction (with larger decreases in SMF) and photosynthetic nitrogen-use efficiency (PNUE) with CO2 enrichment. These results indicate that genetic differences in PNUE and carbon sink utilization (in roots) are both important predictors of tree productivity responsiveness to eCO2.

Leaf-level photosynthetic capacity in lowland Amazonian and high-elevation Andean tropical moist forests of Peru.

PubMed

Bahar, Nur H A; Ishida, F Yoko; Weerasinghe, Lasantha K; Guerrieri, Rossella; O'Sullivan, Odhran S; Bloomfield, Keith J; Asner, Gregory P; Martin, Roberta E; Lloyd, Jon; Malhi, Yadvinder; Phillips, Oliver L; Meir, Patrick; Salinas, Norma; Cosio, Eric G; Domingues, Tomas F; Quesada, Carlos A; Sinca, Felipe; Escudero Vega, Alberto; Zuloaga Ccorimanya, Paola P; Del Aguila-Pasquel, Jhon; Quispe Huaypar, Katherine; Cuba Torres, Israel; Butrón Loayza, Rosalbina; Pelaez Tapia, Yulina; Huaman Ovalle, Judit; Long, Benedict M; Evans, John R; Atkin, Owen K

2017-05-01

We examined whether variations in photosynthetic capacity are linked to variations in the environment and/or associated leaf traits for tropical moist forests (TMFs) in the Andes/western Amazon regions of Peru. We compared photosynthetic capacity (maximal rate of carboxylation of Rubisco (V cmax ), and the maximum rate of electron transport (J max )), leaf mass, nitrogen (N) and phosphorus (P) per unit leaf area (M a , N a and P a , respectively), and chlorophyll from 210 species at 18 field sites along a 3300-m elevation gradient. Western blots were used to quantify the abundance of the CO 2 -fixing enzyme Rubisco. Area- and N-based rates of photosynthetic capacity at 25°C were higher in upland than lowland TMFs, underpinned by greater investment of N in photosynthesis in high-elevation trees. Soil [P] and leaf P a were key explanatory factors for models of area-based V cmax and J max but did not account for variations in photosynthetic N-use efficiency. At any given N a and P a , the fraction of N allocated to photosynthesis was higher in upland than lowland species. For a small subset of lowland TMF trees examined, a substantial fraction of Rubisco was inactive. These results highlight the importance of soil- and leaf-P in defining the photosynthetic capacity of TMFs, with variations in N allocation and Rubisco activation state further influencing photosynthetic rates and N-use efficiency of these critically important forests. © 2016 The Authors. New Phytologist © 2016 New Phytologist Trust.

Optimal allocation of leaf epidermal area for gas exchange.

PubMed

de Boer, Hugo J; Price, Charles A; Wagner-Cremer, Friederike; Dekker, Stefan C; Franks, Peter J; Veneklaas, Erik J

2016-06-01

A long-standing research focus in phytology has been to understand how plants allocate leaf epidermal space to stomata in order to achieve an economic balance between the plant's carbon needs and water use. Here, we present a quantitative theoretical framework to predict allometric relationships between morphological stomatal traits in relation to leaf gas exchange and the required allocation of epidermal area to stomata. Our theoretical framework was derived from first principles of diffusion and geometry based on the hypothesis that selection for higher anatomical maximum stomatal conductance (gsmax ) involves a trade-off to minimize the fraction of the epidermis that is allocated to stomata. Predicted allometric relationships between stomatal traits were tested with a comprehensive compilation of published and unpublished data on 1057 species from all major clades. In support of our theoretical framework, stomatal traits of this phylogenetically diverse sample reflect spatially optimal allometry that minimizes investment in the allocation of epidermal area when plants evolve towards higher gsmax . Our results specifically highlight that the stomatal morphology of angiosperms evolved along spatially optimal allometric relationships. We propose that the resulting wide range of viable stomatal trait combinations equips angiosperms with developmental and evolutionary flexibility in leaf gas exchange unrivalled by gymnosperms and pteridophytes. © 2016 The Authors New Phytologist © 2016 New Phytologist Trust.

[Seasonal differences in the leaf hydraulic conductance of mature Acacia mangium in response to its leaf water use and photosynthesis].

PubMed

Zhao, Ping; Sun, Gu-Chou; Ni, Guang-Yan; Zeng, Xiao-Ping

2013-01-01

In this study, measurements were made on the leaf water potential (psi1), stomatal conductance (g(s)), transpiration rate, leaf area index, and sapwood area of mature Acacia mangium, aimed to understand the relationships of the leaf hydraulic conductance (K1) with the leaf water use and photosynthetic characteristics of the A. mangium in wet season (May) and dry season (November). The ratio of sapwood area to leaf area (A(sp)/A(cl)) of the larger trees with an average height of 20 m and a diameter at breast height (DBH) of 0.26 m was 8.5% higher than that of the smaller trees with an average height of 14.5 m and a DBH of 0.19 m, suggesting that the larger trees had a higher water flux in their leaf xylem, which facilitated the water use of canopy leaf. The analysis on the vulnerability curve of the xylem showed that when the K1 decreased by 50%, the psi1 in wet season and dry season was -1.41 and -1.55 MPa, respectively, and the vulnerability of the xylem cavitation was higher in dry season than in wet season. The K1 peak value in wet season and dry season was 5.5 and 4.5 mmol x m(-2) x s(-1) x MPa(-1), and the maximum transpiration rate (T(r max)) was 3.6 and 1.8 mmol x m(-2) x s(-1), respectively. Both the K1 and T(r max), were obviously higher in wet season than in dry season. Within a day, the K1 and T(r), fluctuated many times, reflecting the reciprocated cycle of the xylem cavitation and refilling. The leaf stomatal closure occurred when the K1 declined over 50% or the psi1 reached -1.6 MPa. The g(s) would be maintained at a high level till the K1 declined over 50%. The correlation between the hydraulic conductance and photosynthetic rate was more significant in dry season than in wet season. The loss of leaf hydraulic conductance induced by seasonal change could be the causes of the decrease of T(r) and CO2 gas exchange.

Effect of light regime and provenance on leaf characteristics, growth and flavonoid accumulation in Cyclocarya paliurus (Batal) Iljinskaja coppices.

PubMed

Liu, Yang; Qian, Chenyun; Ding, Sihui; Shang, Xulan; Yang, Wanxia; Fang, Shengzuo

2016-12-01

As a highly valued and multiple function tree species, Cyclocarya paliurus is planted and managed for timber production and medical use. However, limited information is available on its genotype selection and cultivation for growth and phytochemicals. Responses of growth and secondary metabolites to light regimes and genotypes are useful information to determine suitable habitat conditions for the cultivation of medicinal plants. Both light regime and provenance significantly affected the leaf characteristics, leaf flavonoid contents, biomass production and flavonoid accumulation per plant. Leaf thickness, length of palisade cells and chlorophyll a/b decreased significantly under shading conditions, while leaf areas and total chlorophyll content increased obviously. In the full light condition, leaf flavonoid contents showed a bimodal temporal variation pattern with the maximum observed in August and the second peak in October, while shading treatment not only reduced the leaf content of flavonoids but also delayed the peak appearing of the flavonoid contents in the leaves of C. paliurus. Strong correlations were found between leaf thickness, palisade length, monthly light intensity and measured flavonoid contents in the leaves of C. paliurus. Muchuan provenance with full light achieved the highest leaf biomass and flavonoid accumulation per plant. Cyclocarya paliurus genotypes show diverse responses to different light regimes in leaf characteristics, biomass production and flavonoid accumulation, highlighting the opportunity for extensive selection in the leaf flavonoid production.

A safety vs efficiency trade-off identified in the hydraulic pathway of grass leaves is decoupled from photosynthesis, stomatal conductance and precipitation.

PubMed

Ocheltree, Troy W; Nippert, Jesse B; Prasad, P V Vara

2016-04-01

A common theme in plant physiological research is the trade-off between stress tolerance and growth; an example of this trade-off at the tissue level is the safety vs efficiency hypothesis, which suggests that plants with the greatest resistance to hydraulic failure should have low maximum hydraulic conductance. Here, we quantified the leaf-level drought tolerance of nine C4 grasses as the leaf water potential at which plants lost 50% (P50 × RR ) of maximum leaf hydraulic conductance (Ksat ), and compared this trait with other leaf-level and whole-plant functions. We found a clear trade-off between Ksat and P50 × RR when Ksat was normalized by leaf area and mass (P = 0.05 and 0.01, respectively). However, no trade-off existed between P50 × RR and gas-exchange rates; rather, there was a positive relationship between P50 × RR and photosynthesis (P = 0.08). P50 × RR was not correlated with species distributions based on precipitation (P = 0.70), but was correlated with temperature during the wettest quarter of the year (P < 0.01). These results suggest a trade-off between safety and efficiency in the hydraulic system of grass leaves, which can be decoupled from other leaf-level functions. The unique physiology of C4 plants and adaptations to pulse-driven systems may provide mechanisms that could decouple hydraulic conductance from other plant functions. © 2015 The Authors. New Phytologist © 2015 New Phytologist Trust.

SU-E-T-01: 2-D Characterization of DLG Among All MLC Leaf Pairs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumaraswamy, L; Xu, Z; Podgorsak, M

Purpose: The aim of this study is to evaluate the variation of dosimetric leaf-gap (DLG) along the travel path of each MLC leaf pair. This study evaluates whether the spatial variations in DLG could cause dose differences between TPS-calculated and measured dose. Methods: The 6MV DLG values were measured for all leaf pairs in the direction of leaf motion using a 2-D diode array and 0.6cc ion chamber. These measurements were performed on two Varian Linacs, employing the Millennium 120-leaf MLC and a 2-D-DLG variation map was created via in-house software. Several test plans were created with sweeping MLC fieldsmore » using constant gaps from 2mm to 10mm and corrected for 2-D variation utilizing in-house software. Measurements were performed utilizing the MapCHECK at 5.0cm depth for plans with and without the 2-D DLG correction and compared to the TPS calculated dose via gamma analysis (3%/3mm). Results: The measured DLGs for the middle 40 MLC leaf pairs (0.5cm width) were very similar along the central superior-inferior axis, with maximum variation of 0.2mm. The outer 20 MLC leaf pairs (1.0cm width) have DLG values from 0.32mm (mean) to 0.65mm (maximum) lower than the central leaf-pair, depending on off-axis distance. Gamma pass rates for the 2mm, 4mm, and 6mm sweep plans increased by 23.2%, 28.7%, and 26.0% respectively using the 2-D-DLG correction. The most improved dose points occur in areas modulated by the 1.0cm leaf-pairs. The gamma pass rate for the 10mm sweep plan increased by only 7.7%, indicating that the 2D variation becomes less significant for dynamic plans with larger MLC gaps. Conclusion: Fluences residing significantly off-axis with narrow sweeping gaps may exhibit significant variations from planned dose due to large differences between the true DLG exhibited by the 1.0cm leaf-pairs versus the constant DLG value utilized by the TPS for dose calculation.« less

Plant traits and environment: floating leaf blade production and turnover of waterlilies.

PubMed

Klok, Peter F; van der Velde, Gerard

2017-01-01

Floating leaf blades of waterlilies fulfill several functions in wetland ecosystems by production, decomposition and turnover as well as exchange processes. Production and turnover rates of floating leaf blades of three waterlily species, Nuphar lutea (L.) Sm., Nymphaea alba L. and Nymphaea candida Presl, were studied in three freshwater bodies, differing in trophic status, pH and alkalinity. Length and percentages of leaf loss of marked leaf blades were measured weekly during the growing season. Area and biomass were calculated based on leaf length and were used to calculate the turnover rate of floating leaf blades. Seasonal changes in floating leaf production showed that values decreased in the order: Nymphaea alba , Nuphar lutea , Nymphaea candida . The highest production was reached for Nuphar lutea and Nymphaea alba in alkaline, eutrophic water bodies. The production per leaf was relatively high for both species in the acid water body. Nymphaea candida showed a very short vegetation period and low turnover rates. The ratio Total potential leaf biomass/Maximum potential leaf biomass (P/B max ) of the three species ranged from 1.35-2.25. The ratio Vegetation period (Period with floating leaves)/Mean leaf life span ranged from 2.94-4.63, the ratio Growth period (Period with appearance of new floating leaves)/Vegetation period from 0.53-0.73. The clear differences between Nymphaea candida versus Nuphar lutea and Nymphaea alba , may be due to adaptations of Nymphaea candida to an Euro-Siberic climate with short-lasting summer conditions.

Plant traits and environment: floating leaf blade production and turnover of waterlilies

PubMed Central

2017-01-01

Floating leaf blades of waterlilies fulfill several functions in wetland ecosystems by production, decomposition and turnover as well as exchange processes. Production and turnover rates of floating leaf blades of three waterlily species, Nuphar lutea (L.) Sm., Nymphaea alba L. and Nymphaea candida Presl, were studied in three freshwater bodies, differing in trophic status, pH and alkalinity. Length and percentages of leaf loss of marked leaf blades were measured weekly during the growing season. Area and biomass were calculated based on leaf length and were used to calculate the turnover rate of floating leaf blades. Seasonal changes in floating leaf production showed that values decreased in the order: Nymphaea alba, Nuphar lutea, Nymphaea candida. The highest production was reached for Nuphar lutea and Nymphaea alba in alkaline, eutrophic water bodies. The production per leaf was relatively high for both species in the acid water body. Nymphaea candida showed a very short vegetation period and low turnover rates. The ratio Total potential leaf biomass/Maximum potential leaf biomass (P/Bmax) of the three species ranged from 1.35–2.25. The ratio Vegetation period (Period with floating leaves)/Mean leaf life span ranged from 2.94–4.63, the ratio Growth period (Period with appearance of new floating leaves)/Vegetation period from 0.53–0.73. The clear differences between Nymphaea candida versus Nuphar lutea and Nymphaea alba, may be due to adaptations of Nymphaea candida to an Euro-Siberic climate with short-lasting summer conditions. PMID:28462025

[PS II photochemical efficiency in flag leaf of wheat varieties and its adaptation to strong sun- light intensity on farmland of Xiangride in Qinghai Province, Northwest China].

PubMed

Shi, Sheng-Bo; Chen, Wen-Jie; Shi, Rui; Li, Miao; Zhang, Huai-Gang; Sun, Ya-Nan

2014-09-01

Taking four wheat varieties developed by Northwest Institute of Plateau Biology, Chinese Academy of Sciences, as test materials, with the measurement of content of photosynthetic pigments, leaf area, fresh and dry mass of flag leaf, the PS II photochemistry efficiency of abaxial and adaxial surface of flag leaf and its adaptation to strong solar radiation during the period of heading stage in Xiangride region were investigated with the pulse-modulated in-vivo chlorophyll fluorescence technique. The results indicated that flag leaf angle mainly grew in horizontal state in Gaoyuan 314, Gaoyuan 363 and Gaoyuan 584, and mainly in vertical state in Gaoyuan 913 because of its smaller leaf area and larger width. Photosynthetic pigments were different among the 4 varieties, and positively correlated with intrinsic PS II photochemistry efficiencies (Fv/Fm). In clear days, especially at noon, the photosynthetic photoinhibition was more serious in abaxial surface of flag leaf due to directly facing the solar radiation, but it could recover after reduction of sunlight intensity in the afternoon, which meant that no inactive damage happened in PS II reaction centers. There were significant differences of PS II actual and maximum photochemical efficiencies at the actinic light intensity (ΦPS II and Fv'/Fm') between abaxial and adaxial surface, and their relative variation trends were on the contrary. The photochemical and non-photochemical quenching coefficients (qP and NPQ) had a similar tendency in both abaxial and adaxial surfaces. Although ΦPS II and qP were lower in adaxial surface of flag leaf, the Fv'/Fm' was significantly higher, which indicated that the potential PS II capture efficiency of excited energy was higher. The results demonstrated that process of photochemical and non-photochemical quenching could effectively dissipate excited energy caused by strong solar radiation, and there were higher adaptation capacities in wheat varieties natively cultivated in Qinghai-Tibetan Plateau area.

Leaf gas films, underwater photosynthesis and plant species distributions in a flood gradient.

PubMed

Winkel, Anders; Visser, Eric J W; Colmer, Timothy D; Brodersen, Klaus P; Voesenek, Laurentius A C J; Sand-Jensen, Kaj; Pedersen, Ole

2016-07-01

Traits for survival during flooding of terrestrial plants include stimulation or inhibition of shoot elongation, aerenchyma formation and efficient gas exchange. Leaf gas films form on superhydrophobic cuticles during submergence and enhance underwater gas exchange. The main hypothesis tested was that the presence of leaf gas films influences the distribution of plant species along a natural flood gradient. We conducted laboratory experiments and field observations on species distributed along a natural flood gradient. We measured presence or absence of leaf gas films and specific leaf area of 95 species. We also measured, gas film retention time during submergence and underwater net photosynthesis and dark respiration of 25 target species. The presence of a leaf gas film was inversely correlated to flood frequency and duration and reached a maximum value of 80% of the species in the rarely flooded locations. This relationship was primarily driven by grasses that all, independently of their field location along the flood gradient, possess gas films when submerged. Although the present study and earlier experiments have shown that leaf gas films enhance gas exchange of submerged plants, the ability of species to form leaf gas films did not show the hypothesized relationship with species composition along the flood gradient. © 2016 John Wiley & Sons Ltd.

Quantitative study of Xanthosoma violaceum leaf surfaces using RIMAPS and variogram techniques.

PubMed

Favret, Eduardo A; Fuentes, Néstor O; Molina, Ana M

2006-08-01

Two new imaging techniques (rotated image with maximum averaged power spectrum (RIMAPS) and variogram) are presented for the study and description of leaf surfaces. Xanthosoma violaceum was analyzed to illustrate the characteristics of both techniques. Both techniques produce a quantitative description of leaf surface topography. RIMAPS combines digitized images rotation with Fourier transform, and it is used to detect patterns orientation and characteristics of surface topography. Variogram relates the mathematical variance of a surface with the area of the sample window observed. It gives the typical scale lengths of the surface patterns. RIMAPS detects the morphological variations of the surface topography pattern between fresh and dried (herbarium) samples of the leaf. The variogram method finds the characteristic dimensions of the leaf microstructure, i.e., cell length, papillae diameter, etc., showing that there are not significant differences between dry and fresh samples. The results obtained show the robustness of RIMAPS and variogram analyses to detect, distinguish, and characterize leaf surfaces, as well as give scale lengths. Both techniques are tools for the biologist to study variations of the leaf surface when different patterns are present. The use of RIMAPS and variogram opens a wide spectrum of possibilities by providing a systematic, quantitative description of the leaf surface topography.

Modeling the leaf angle dynamics in rice plant.

PubMed

Zhang, Yonghui; Tang, Liang; Liu, Xiaojun; Liu, Leilei; Cao, Weixing; Zhu, Yan

2017-01-01

The leaf angle between stem and sheath (SSA) is an important rice morphological trait. The objective of this study was to develop and validate a dynamic SSA model under different nitrogen (N) rates for selected rice cultivars. The time-course data of SSA were collected in three years, and a dynamic SSA model was developed for different main stem leaf ranks under different N rates for two selected rice cultivars. SSA increased with tiller age. The SSA of the same leaf rank increased with increase in N rate. The maximum SSA increased with leaf rank from the first to the third leaf, then decreased from the third to the final leaf. The relationship between the maximum SSA and leaf rank on main stem could be described with a linear piecewise function. The change of SSA with thermal time (TT) was described by a logistic equation. A variety parameter (the maximum SSA of the 3rd leaf on main stem) and a nitrogen factor were introduced to quantify the effect of cultivar and N rate on SSA. The model was validated against data collected from both pot and field experiments. The relative root mean square error (RRMSE) was 11.56% and 14.05%, respectively. The resulting models could be used for virtual rice plant modeling and plant-type design.

Simultaneous minimization of leaf travel distance and tongue-and-groove effect for segmental intensity-modulated radiation therapy.

PubMed

Dai, Jianrong; Que, William

2004-12-07

This paper introduces a method to simultaneously minimize the leaf travel distance and the tongue-and-groove effect for IMRT leaf sequences to be delivered in segmental mode. The basic idea is to add a large enough number of openings through cutting or splitting existing openings for those leaf pairs with openings fewer than the number of segments so that all leaf pairs have the same number of openings. The cutting positions are optimally determined with a simulated annealing technique called adaptive simulated annealing. The optimization goal is set to minimize the weighted summation of the leaf travel distance and tongue-and-groove effect. Its performance was evaluated with 19 beams from three clinical cases; one brain, one head-and-neck and one prostate case. The results show that it can reduce the leaf travel distance and (or) tongue-and-groove effect; the reduction of the leaf travel distance reaches its maximum of about 50% when minimized alone; the reduction of the tongue-and-groove reaches its maximum of about 70% when minimized alone. The maximum reduction in the leaf travel distance translates to a 1 to 2 min reduction in treatment delivery time per fraction, depending on leaf speed. If the method is implemented clinically, it could result in significant savings in treatment delivery time, and also result in significant reduction in the wear-and-tear of MLC mechanics.

Influence of Water Relations and Temperature on Leaf Movements of Rhododendron Species 1

PubMed Central

Nilsen, Erik Tallak

1987-01-01

Rhododendron maximum L. and R. Catawbiense L. are subcanopy evergreen shrubs of the eastern United States deciduous forest. Field measurements of climate factors and leaf movements of these species indicated a high correlation between leaf temperature and leaf curling; and between leaf water potential and leaf angle. Laboratory experiments were performed to isolate the influence of temperature and cellular water relations on leaf movements. Significant differences were found between the patterns of temperature induction of leaf curling in the two species. Leaves of the species which curled at higher temperatures (R. catawbiense) also froze at higher leaf temperatures. However, in both cases leaf curling occurred at leaf temperatures two to three degrees above the leaf freezing point. Pressure volume curves indicated that cellular turgor loss was associated with a maximum of 45% curling while 100% or more curling occurred in field leaves which still had positive cell turgor. Moisture release curves indicated that 70% curling requires a loss of greater than 60% of symplastic water which corresponds to leaf water potentials far below those experienced in field situations. Conversely, most laboratory induced changes in leaf angle could be related to leaf cell turgor loss. PMID:16665296

To what extent is altitudinal variation of functional traits driven by genetic adaptation in European oak and beech?

PubMed

Bresson, Caroline C; Vitasse, Yann; Kremer, Antoine; Delzon, Sylvain

2011-11-01

The phenotypic responses of functional traits in natural populations are driven by genetic diversity and phenotypic plasticity. These two mechanisms enable trees to cope with rapid climate change. We studied two European temperate tree species (sessile oak and European beech), focusing on (i) in situ variations of leaf functional traits (morphological and physiological) along two altitudinal gradients and (ii) the extent to which these variations were under environmental and/or genetic control using a common garden experiment. For all traits, altitudinal trends tended to be highly consistent between species and transects. For both species, leaf mass per area displayed a positive linear correlation with altitude, whereas leaf size was negatively correlated with altitude. We also observed a significant increase in leaf physiological performance with increasing altitude: populations at high altitudes had higher maximum rates of assimilation, stomatal conductance and leaf nitrogen content than those at low altitudes. In the common garden experiment, genetic differentiation between populations accounted for 0-28% of total phenotypic variation. However, only two traits (leaf mass per area and nitrogen content) exhibited a significant cline. The combination of in situ and common garden experiments used here made it possible to demonstrate, for both species, a weaker effect of genetic variation than of variations in natural conditions, suggesting a strong effect of the environment on leaf functional traits. Finally, we demonstrated that intrapopulation variability was systematically higher than interpopulation variability, whatever the functional trait considered, indicating a high potential capacity to adapt to climate change.

Use of GLM approach to assess the responses of tropical trees to urban air pollution in relation to leaf functional traits and tree characteristics.

PubMed

Mukherjee, Arideep; Agrawal, Madhoolika

2018-05-15

Responses of urban vegetation to air pollution stress in relation to their tolerance and sensitivity have been extensively studied, however, studies related to air pollution responses based on different leaf functional traits and tree characteristics are limited. In this paper, we have tried to assess combined and individual effects of major air pollutants PM 10 (particulate matter ≤ 10 µm), TSP (total suspended particulate matter), SO 2 (sulphur dioxide), NO 2 (nitrogen dioxide) and O 3 (ozone) on thirteen tropical tree species in relation to fifteen leaf functional traits and different tree characteristics. Stepwise linear regression a general linear modelling approach was used to quantify the pollution response of trees against air pollutants. The study was performed for six successive seasons for two years in three distinct urban areas (traffic, industrial and residential) of Varanasi city in India. At all the study sites, concentrations of air pollutants, specifically PM (particulate matter) and NO 2 were above the specified standards. Distinct variations were recorded in all the fifteen leaf functional traits with pollution load. Caesalpinia sappan was identified as most tolerant species followed by Psidium guajava, Dalbergia sissoo and Albizia lebbeck. Stepwise regression analysis identified maximum response of Eucalyptus citriodora and P. guajava to air pollutants explaining overall 59% and 58% variability's in leaf functional traits, respectively. Among leaf functional traits, maximum effect of air pollutants was observed on non-enzymatic antioxidants followed by photosynthetic pigments and leaf water status. Among the pollutants, PM was identified as the major stress factor followed by O 3 explaining 47% and 33% variability's in leaf functional traits. Tolerance and pollution response were regulated by different tree characteristics such as height, canopy size, leaf from, texture and nature of tree. Outcomes of this study will help in urban forest development by selection of specific pollutant tolerant tree species and leaf traits, which is suitable as air pollution mitigation measure. Copyright © 2018 Elsevier Inc. All rights reserved.

Shenandoah National Park Phenology Project-Weather data collection, description, and processing

USGS Publications Warehouse

Jones, John W.; Aiello, Danielle P.; Osborne, Jesse D.

2010-01-01

The weather data described in this document are being collected as part of a U.S. Geological Survey (USGS) study of changes in Shenandoah National Park (SNP) landscape phenology (Jones and Osbourne, 2008). Phenology is the study of the timing of biological events, such as annual plant flowering and seasonal bird migration. These events are partially driven by changes in temperature and precipitation; therefore, phenology studies how these events may reflect changes in climate. Landscape phenology is the study of changes in biological events over broad areas and assemblages of vegetation. To study climate-change relations over broad areas (at landscape scale), the timing and amount of annual tree leaf emergence, maximum foliage, and leaf fall for forested areas are of interest. To better link vegetation changes with climate, weather data are necessary. This report documents weather-station data collection and processing procedures used in the Shenandoah National Park Phenology Project.

The seasonality of AVHRR data of temperate coniferous forests - Relationship with leaf area index

NASA Technical Reports Server (NTRS)

Spanner, Michael A.; Pierce, Lars L.; Running, Steven W.; Peterson, David L.

1990-01-01

The relationship between the advanced very high resolution radiometer (AVHRR) normalized difference vegetation index (NDVI) and coniferous forest leaf area index (LAI) over the western United States is examined. AVHRR data from the NOAA-9 satellite were acquired of the western U.S. from March 1986 to November 1987 and monthly maximum value composites of AVHRR NDVI were calculated for 19 coniferous forest stands in Oregon, Washington, Montana, and California. It is concluded that the relationships under investigation vary according to seasonal changes in surface reflectance based on key biotic and abiotic controls including phenological changes in LAI caused by seasonal temperature and precipitation variations, the proportions of surface cover types contributing to the overall reflectance, and effects resulting from large variations in the solar zenith angle.

Evaluation of Methane from Sisal Leaf Residue and Palash Leaf Litter

NASA Astrophysics Data System (ADS)

Arisutha, S.; Baredar, P.; Deshpande, D. M.; Suresh, S.

2014-12-01

The aim of this study is to evaluate methane production from sisal leaf residue and palash leaf litter mixed with different bulky materials such as vegetable market waste, hostel kitchen waste and digested biogas slurry in a laboratory scale anaerobic reactor. The mixture was prepared with 1:1 proportion. Maximum methane content of 320 ml/day was observed in the case of sisal leaf residue mixed with vegetable market waste as the feed. Methane content was minimum (47 ml/day), when palash leaf litter was used as feed. This was due to the increased content of lignin and polyphenol in the feedstock which were of complex structure and did not get degraded directly by microorganisms. Sisal leaf residue mixtures also showed highest content of volatile fatty acids (VFAs) as compared to palash leaf litter mixtures. It was observed that VFA concentration in the digester first increased, reached maximum (when pH was minimum) and then decreased.

Variation in chlorophyll content per unit leaf area in spring wheat and implications for selection in segregating material.

PubMed

Hamblin, John; Stefanova, Katia; Angessa, Tefera Tolera

2014-01-01

Reduced levels of leaf chlorophyll content per unit leaf area in crops may be of advantage in the search for higher yields. Possible reasons include better light distribution in the crop canopy and less photochemical damage to leaves absorbing more light energy than required for maximum photosynthesis. Reduced chlorophyll may also reduce the heat load at the top of canopy, reducing water requirements to cool leaves. Chloroplasts are nutrient rich and reducing their number may increase available nutrients for growth and development. To determine whether this hypothesis has any validity in spring wheat requires an understanding of genotypic differences in leaf chlorophyll content per unit area in diverse germplasm. This was measured with a SPAD 502 as SPAD units. The study was conducted in series of environments involving up to 28 genotypes, mainly spring wheat. In general, substantial and repeatable genotypic variation was observed. Consistent SPAD readings were recorded for different sampling positions on leaves, between different leaves on single plant, between different plants of the same genotype, and between different genotypes grown in the same or different environments. Plant nutrition affected SPAD units in nutrient poor environments. Wheat genotypes DBW 10 and Transfer were identified as having consistent and contrasting high and low average SPAD readings of 52 and 32 units, respectively, and a methodology to allow selection in segregating populations has been developed.

The hydraulic limitation hypothesis revisited.

PubMed

Ryan, Michael G; Phillips, Nathan; Bond, Barbara J

2006-03-01

We proposed the hydraulic limitation hypothesis (HLH) as a mechanism to explain universal patterns in tree height, and tree and stand biomass growth: height growth slows down as trees grow taller, maximum height is lower for trees of the same species on resource-poor sites and annual wood production declines after canopy closure for even-aged forests. Our review of 51 studies that measured one or more of the components necessary for testing the hypothesis showed that taller trees differ physiologically from shorter, younger trees. Stomatal conductance to water vapour (g(s)), photosynthesis (A) and leaf-specific hydraulic conductance (K L) are often, but not always, lower in taller trees. Additionally, leaf mass per area is often greater in taller trees, and leaf area:sapwood area ratio changes with tree height. We conclude that hydraulic limitation of gas exchange with increasing tree size is common, but not universal. Where hydraulic limitations to A do occur, no evidence supports the original expectation that hydraulic limitation of carbon assimilation is sufficient to explain observed declines in wood production. Any limit to height or height growth does not appear to be related to the so-called age-related decline in wood production of forests after canopy closure. Future work on this problem should explicitly link leaf or canopy gas exchange with tree and stand growth, and consider a more fundamental assumption: whether tree biomass growth is limited by carbon availability.

Estimating maximum mean canopy stomatal conductance for use in models

Treesearch

Brent E. Ewers; Ram Oren; Kurt H. Johnsen; J.J Landsberg

2001-01-01

Fertilized (F) and irrigated and fertilized (IF) stands of Pinus taeda L. produced twice the leaf area index of irrigated (I) and control (C) stands. Based on sap flux-scaled mean stomatal conductance (GS), we found that stomatal conductance in F was half that in other treatments. During the growing season, GS was related to...

Growth response of Douglas-fir seedlings to nitrogen fertilization: importance of Rubisco activation state and respiration rates.

PubMed

Manter, Daniel K; Kavanagh, Kathleen L; Rose, Cathy L

2005-08-01

High foliar nitrogen concentration ([N]) is associated with high rates of photosynthesis and thus high tree productivity; however, at excessive [N], tree productivity is reduced. Reports of excessive [N] in the Douglas-fir forests of the Oregon Coast Range prompted this investigation of growth and needle physiological responses to increasing foliar N concentrations in 1-year-old Douglas-fir seedlings. After 1 year of N fertilization, total seedling biomass increased with each successive increase in N fertilizer concentration, except in the highest N fertilization treatment. Of the many physiological responses that were analyzed, only photosynthetic capacity (i.e., Vcmax), respiration rates and leaf specific conductance (KL) differed significantly between N treatments. Photosynthetic capacity showed a curvilinear relationship with foliar [N], reaching an apparent maximum rate when needle N concentrations exceeded about 12 mg g(-1). In vitro measurements of ribulose-1,5-bisphosphate carboxylase (Rubisco) activity suggested that photosynthetic capacity was best related to activated, not total, Rubisco content. Rubisco activation state declined as foliar [N] increased, and based on its significant correlation (r2= 0.63) with foliar Mn:Mg ratios, it may be related to Mn inactivation of Rubisco. Respiration rates increased linearly as foliar N concentration increased (r2= 0.84). The value of K(L) also increased as foliar [N] increased, reaching a maximum when foliar [N] exceeded about 10 mg g(-1). Changes in K(L) were unrelated to changes in leaf area or sapwood area because leaf area to sapwood area ratios remained constant. Cumulative effects of the observed physiological responses to N fertilization were analyzed by modeling annual net CO2 assimilation (Anet) based on treatment specific values of Vcmax, dark respiration (Rdark) and KL. Estimates of Anet were highly correlated with measured total seedling biomass (r2= 0.992), suggesting that long-term, cumulative effects of maximum Rubisco carboxylation, Rdark and KL responses to N fertilization may limit seedling production when foliar N exceeds about 13 mg g(-1) or is reduced to less than about 11 mg g(-1).

Predicting the limits to tree height using statistical regressions of leaf traits.

PubMed

Burgess, Stephen S O; Dawson, Todd E

2007-01-01

Leaf morphology and physiological functioning demonstrate considerable plasticity within tree crowns, with various leaf traits often exhibiting pronounced vertical gradients in very tall trees. It has been proposed that the trajectory of these gradients, as determined by regression methods, could be used in conjunction with theoretical biophysical limits to estimate the maximum height to which trees can grow. Here, we examined this approach using published and new experimental data from tall conifer and angiosperm species. We showed that height predictions were sensitive to tree-to-tree variation in the shape of the regression and to the biophysical endpoints selected. We examined the suitability of proposed end-points and their theoretical validity. We also noted that site and environment influenced height predictions considerably. Use of leaf mass per unit area or leaf water potential coupled with vulnerability of twigs to cavitation poses a number of difficulties for predicting tree height. Photosynthetic rate and carbon isotope discrimination show more promise, but in the second case, the complex relationship between light, water availability, photosynthetic capacity and internal conductance to CO(2) must first be characterized.

Leaf habit and woodiness regulate different leaf economy traits at a given nutrient supply.

PubMed

Ordoñez, Jenny C; van Bodegom, Peter M; Witte, Jan-Philip M; Bartholomeus, Ruud P; van Dobben, Han F; Aerts, Rien

2010-11-01

The large variation in the relationships between environmental factors and plant traits observed in natural communities exemplifies the alternative solutions that plants have developed in response to the same environmental limitations. Qualitative attributes, such as growth form, woodiness, and leaf habit can be used to approximate these alternative solutions. Here, we quantified the extent to which these attributes affect leaf trait values at a given resource supply level, using measured plant traits from 105 different species (254 observations) distributed across 50 sites in mesic to wet plant communities in The Netherlands. For each site, soil total N, soil total P, and water supply estimates were obtained by field measurements and modeling. Effects of growth forms, woodiness, and leaf habit on relations between leaf traits (SLA, specific leaf area; LNC, leaf nitrogen concentration; and LPC, leaf phosphorus concentration) vs. nutrient and water supply were quantified using maximum-likelihood methods and Bonferroni post hoc tests. The qualitative attributes explained 8-23% of the variance within sites in leaf traits vs. soil fertility relationships, and therefore they can potentially be used to make better predictions of global patterns of leaf traits in relation to nutrient supply. However, at a given soil fertility, the strength of the effect of each qualitative attribute was not the same for all leaf traits. These differences may imply a differential regulation of the leaf economy traits at a given nutrient supply, in which SLA and LPC seem to be regulated in accordance to changes in plant size and architecture while LNC seems to be primarily regulated at the leaf level by factors related to leaf longevity.

Structural and Physiological Changes in Sugar Beet Leaves during Sink to Source Conversion 1

PubMed Central

Fellows, Robert J.; Geiger, Donald R.

1974-01-01

The onset of export during leaf development was correlated with changes in metabolism and ultrastructure and with patterns of solute distribution in the developing seventh leaf of sugar beet (Beta vulgaris L.) in order to study the cause of initiation of translocation. Infrared gas analysis of carbon dioxide uptake showed a broad peak for net photosynthesis dm−2 at 35 to 40% final laminar length. Pulse labeling with 14CO2 demonstrated that maximum import of translocate occurred at 25% final laminar length; export was first observed at 35% final laminar length. Between 40 and 50% final laminar length a rapid increase in amount of export occurred, primarily as a result of the increase in the area of leaf which was exporting. Whole leaf autoradiography revealed that onset of phloem loading spread basipetally from the leaf tip; loading was initiated at about 22% final laminar length and was essentially complete by 50% final laminar length. Those areas which clearly exhibited loading no longer imported from other parts of the plant while the area in transition still appeared to import label from source regions. There was little difference between source and sink leaf tissue in the kinetic parameters Kj and Jmax (30) for uptake of exogenous sucrose supplied via free space. The concentration of solutes in sieve elements and companion cells of the sink leaf was highest in the mature tip area and gradually decreased in the direction of the immature base. There appeared to be no dramatic structural transformation within the phloem of the minor veins that was closely correlated with the time when phloem loading or export began. Rather, there appeared to be a gradual differentiation of phloem which resulted in a sizable proportion of the population of minor vein sieve elements and companion cells attaining maturity in the older sink regions prior to initiation of phloem loading. The area of the leaf undergoing development appeared to exhibit the beginnings of phloem loading 30 to 45 hours prior to onset of export. Import continued into the area in transition until the full level of vein loading was attained. Structural maturation of the phloem and onset of phloem loading are felt to be more preparatory in nature rather than immediately causal events which triggered export. The initiation of export out of a developing leaf, we believe, is the result of the increasing solute content within the sieve element and companion cells of the minor veins, in particular. The higher osmotic pressure in the sieve tubes causes a reversal of the previously inward directed gradient and produces a mass flow, through unobstructed sieve elements, out of the new source region of the leaf. Images PMID:16658993

Integrated crop management practices for maximizing grain yield of double-season rice crop.

PubMed

Wang, Depeng; Huang, Jianliang; Nie, Lixiao; Wang, Fei; Ling, Xiaoxia; Cui, Kehui; Li, Yong; Peng, Shaobing

2017-01-12

Information on maximum grain yield and its attributes are limited for double-season rice crop grown under the subtropical environment. This study was conducted to examine key characteristics associated with high yielding double-season rice crop through a comparison between an integrated crop management (ICM) and farmers' practice (FP). Field experiments were conducted in the early and late seasons in the subtropical environment of Wuxue County, Hubei Province, China in 2013 and 2014. On average, grain yield in ICM was 13.5% higher than that in FP. A maximum grain yield of 9.40 and 10.53 t ha -1 was achieved under ICM in the early- and late-season rice, respectively. Yield improvement of double-season rice with ICM was achieved with the combined effects of increased plant density and optimized nutrient management. Yield gain of ICM resulted from a combination of increases in sink size due to more panicle number per unit area and biomass production, further supported by the increased leaf area index, leaf area duration, radiation use efficiency, crop growth rate, and total nitrogen uptake compared with FP. Further enhancement in the yield potential of double-season rice should focus on increasing crop growth rate and biomass production through improved and integrated crop management practices.

Phenology, Canopy Aging and Seasonal Carbon Balance as Related to Delayed Winter Pruning of Vitis vinifera L. cv. Sangiovese Grapevines

PubMed Central

Gatti, Matteo; Pirez, Facundo J.; Chiari, Giorgio; Tombesi, Sergio; Palliotti, Alberto; Merli, Maria C.; Poni, Stefano

2016-01-01

Manipulating or shifting annual grapevine growing cycle to offset limitations imposed by global warming is a must today, and delayed winter pruning is a tool to achieve it. However, no information is available about its physiological background, especially in relation to modifications in canopy phenology, demography and seasonal carbon budget. Mechanistic hypothesis underlying this work was that very late winter pruning (LWP) can achieve significant postponement of phenological stages so that ripening might occur in a cooler period and, concurrently, ripening potential can be improved due to higher efficiency and prolonged longevity of the canopy. Variability in the dynamics of the annual cycle was created in mature potted cv. Sangiovese grapevines subjected to either standard winter pruning (SWP) or late and very late winter pruning (LWP, VLWP) performed when apical shoots on the unpruned canes were at the stage of 2 and 7 unfolded leaves. Vegetative growth, phenology and canopy net CO2 exchange (NCER) were followed throughout the season. Despite LWP and VLWP induced a bud-burst delay of 17 and 31 days vs. SWP, the delay was fully offset at harvest for LWP and was reduced to 6 days in VLWP. LWP showed notably higher canopy efficiency as shorter time needed to reach maximum NCER/leaf area (22 days vs. 34 in SWP), highest maximum NCER/leaf area (+37% as compared to SWP) and higher NCER/leaf area rates from veraison to end of season. As a result, seasonal cumulated carbon in LWP was 17% higher than SWP. A negative functional relationship was also established between amount of leaf area removed at winter pruning and yield per vine and berry number per cluster. Although retarded winter pruning was not able to postpone late-season phenological stages under the warm conditions of this study, it showed a remarkable potential to limit yield while improving grape quality, thereby fostering the hypothesis that it could be used to replace time-consuming and costly cluster thinning. This preliminary study indicates that proper winter pruning date should be timed so as not to exceed the stage of two unfolded leaves. PMID:27242860

Study of the Light Received Characteristics of a Plant-Shoot-Light-Condensing System with Simple Leaves or Lobed Leaves

NASA Astrophysics Data System (ADS)

Obara, Shin'ya

Plant shoot configurations evolve so that maximum sunlight may be obtained. The objective of this study is to develop a compact light-condensing system mimicking a plant shoot configuration that is applicable to a light source from a large area. In this paper, the relationship between the position of a light source (the sun) and the rate at which light is absorbed by each leaf was investigated in detail for plant shoot models of a dogwood (simple leaf) and a ginkgo tree (lobed leaf). The rate of light quantum received in each leaf model is reported to an analysis program that uses cross entropy (CE). The analyses showed that the peak amount of light received in the plant-shoot-light-condensing system was during February (vernal equinox) and October (autumnal equinox). Similarly, the rate of light quantum received in each leaf was measured with the CE. The results found that the plant-shoot-light-condensing system that maximizes the amount of light received has differences in the light received in each leaf. Furthermore, the light-condensing characteristics of the ginkgo biloba model are better than the dogwood model. The light-condensing characteristics of a leaf are influenced by the size, a lobe, shape, and the length of the branch.

Are lianas more drought-tolerant than trees? A test for the role of hydraulic architecture and other stem and leaf traits.

PubMed

van der Sande, Masha T; Poorter, Lourens; Schnitzer, Stefan A; Markesteijn, Lars

2013-08-01

Lianas are an important component of neotropical forests, where evidence suggests that they are increasing in abundance and biomass. Lianas are especially abundant in seasonally dry tropical forests, and as such it has been hypothesized that they are better adapted to drought, or that they are at an advantage under the higher light conditions in these forests. However, the physiological and morphological characteristics that allow lianas to capitalize more on seasonal forest conditions compared to trees are poorly understood. Here, we evaluate how saplings of 21 tree and liana species from a seasonal tropical forest in Panama differ in cavitation resistance (P50) and maximum hydraulic conductivity (K(h)), and how saplings of 24 tree and liana species differ in four photosynthetic leaf traits (e.g., maximum assimilation and stomatal conductance) and six morphological leaf and stem traits (e.g., wood density, maximum vessel length, and specific leaf area). At the sapling stage, lianas had a lower cavitation resistance than trees, implying lower drought tolerance, and they tended to have a higher potential hydraulic conductivity. In contrast to studies focusing on adult trees and lianas, we found no clear differences in morphological and photosynthetic traits between the life forms. Possibly, lianas and trees are functionally different at later ontogenetic stages, with lianas having deeper root systems than trees, or experience their main growth advantage during wet periods, when they are less vulnerable to cavitation and can achieve high conductivity. This study shows, however, that the hydraulic characteristics and functional traits that we examined do not explain differences in liana and tree distributions in seasonal forests.

Leaf and stem economics spectra drive diversity of functional plant traits in a dynamic global vegetation model.

PubMed

Sakschewski, Boris; von Bloh, Werner; Boit, Alice; Rammig, Anja; Kattge, Jens; Poorter, Lourens; Peñuelas, Josep; Thonicke, Kirsten

2015-01-22

Functional diversity is critical for ecosystem dynamics, stability and productivity. However, dynamic global vegetation models (DGVMs) which are increasingly used to simulate ecosystem functions under global change, condense functional diversity to plant functional types (PFTs) with constant parameters. Here, we develop an individual- and trait-based version of the DGVM LPJmL (Lund-Potsdam-Jena managed Land) called LPJmL- flexible individual traits (LPJmL-FIT) with flexible individual traits) which we apply to generate plant trait maps for the Amazon basin. LPJmL-FIT incorporates empirical ranges of five traits of tropical trees extracted from the TRY global plant trait database, namely specific leaf area (SLA), leaf longevity (LL), leaf nitrogen content (N area ), the maximum carboxylation rate of Rubisco per leaf area (vcmaxarea), and wood density (WD). To scale the individual growth performance of trees, the leaf traits are linked by trade-offs based on the leaf economics spectrum, whereas wood density is linked to tree mortality. No preselection of growth strategies is taking place, because individuals with unique trait combinations are uniformly distributed at tree establishment. We validate the modeled trait distributions by empirical trait data and the modeled biomass by a remote sensing product along a climatic gradient. Including trait variability and trade-offs successfully predicts natural trait distributions and achieves a more realistic representation of functional diversity at the local to regional scale. As sites of high climatic variability, the fringes of the Amazon promote trait divergence and the coexistence of multiple tree growth strategies, while lower plant trait diversity is found in the species-rich center of the region with relatively low climatic variability. LPJmL-FIT enables to test hypotheses on the effects of functional biodiversity on ecosystem functioning and to apply the DGVM to current challenges in ecosystem management from local to global scales, that is, deforestation and climate change effects. © 2015 John Wiley & Sons Ltd.

Assessing soybean leaf area and leaf biomass by spectral measurements

NASA Technical Reports Server (NTRS)

Holben, B. N.; Tucker, C. J.; Fan, C. J.

1979-01-01

Red and photographic infrared spectral radiances were correlated with soybean total leaf area index, green leaf area index, chlorotic leaf area index, green leaf biomass, chlorotic leaf biomass, and total biomass. The most significant correlations were found to exist between the IR/red radiance ratio data and green leaf area index and/or green leaf biomass (r squared equals 0.85 and 0.86, respectively). These findings demonstrate that remote sensing data can supply information basic to soybean canopy growth, development, and status by nondestructive determination of the green leaf area or green leaf biomass.

Model estimates of leaf area and reference canopy stomatal conductance suggest correlation between phenology and physiology in both trembling aspen and red pine

NASA Astrophysics Data System (ADS)

Mackay, D. S.; Ewers, B. E.; Kruger, E. L.

2006-12-01

Phenological variations impact water and carbon fluxes, as evidenced by the large interannual variability of net ecosystem exchange of carbon dioxide and evapotranspiration (ET). In northern Wisconsin we observed daily variations of canopy transpiration from hardwoods from 1.0 to 1.7 mm/day during the leaf unfolding period and 1.7 to 2.6 mm/day with leaves fully out. Correlations between such flux rates and phenology have not been extensively tested and mechanistic connections are in their infancy. Some data suggest that stomatal conductance and photosynthesis increases up to full expansion. Moreover, in conifers, the interaction of phenology and physiology is more complicated than in deciduous trees because needles are retained for several years. Using inverse modeling with a coupled photosynthesis-transpiration model we estimated reference canopy stomatal conductance, Gsref, for red pine (Pinus resinosa), and Gsref and leaf area index, L, for trembling aspen (Populus tremuloides), using 30-min continuous sap flux data spanning a period from just prior to the start of leaf expansion to just after leaf senescence. The red pine showed Gsref ramp up from 105 to 179 mmol m-2 leaf s-1, which represented a 37 to 50 percent increase in Gsref after accounting for maximum possible changes in L. After full leaf out, the trembling aspen were almost immediately defoliated, and then reflushed after three weeks. Model estimates of L reflected this pattern and were consistent with measurements. However, Gsref never exceeded 45 mmol m-2 s-1 prior to defoliation, but peaked at 112 mmol m-2 s-1 after reflushing. These results support the need for further work that aims to separate phenology and physiology.

The expression of light-related leaf functional traits depends on the location of individual leaves within the crown of isolated Olea europaea trees

PubMed Central

Escribano-Rocafort, Adrián G.; Ventre-Lespiaucq, Agustina B.; Granado-Yela, Carlos; Rubio de Casas, Rafael; Delgado, Juan A.; Balaguer, Luis

2016-01-01

Background The spatial arrangement and expression of foliar syndromes within tree crowns can reflect the coupling between crown form and function in a given environment. Isolated trees subjected to high irradiance and concomitant stress may adjust leaf phenotypes to cope with environmental gradients that are heterogeneous in space and time within the tree crown. The distinct expression of leaf phenotypes among crown positions could lead to complementary patterns in light interception at the crown scale. Methods We quantified eight light-related leaf traits across 12 crown positions of ten isolated Olea europaea trees in the field. Specifically, we investigated whether the phenotypic expression of foliar traits differed among crown sectors and layers and five periods of the day from sunrise to sunset. We investigated the consequences in terms of the exposed area of the leaves at the tree scale during a single day. Key Results All traits differed among crown positions except the length-to-width ratio of the leaves. We found a strong complementarity in the patterns of the potential exposed area of the leaves among day periods as a result of a non-random distribution of leaf angles across the crown. Leaf exposure at the outer layer was below 60 % of the displayed surface, reaching maximum interception during morning periods. Daily interception increased towards the inner layer, achieving consecutive maximization from east to west positions within the crown, matching the sun’s trajectory. Conclusions The expression of leaf traits within isolated trees of O. europaea varies continuously through the crown in a gradient of leaf morphotypes and leaf angles depending on the exposure and location of individual leaves. The distribution of light-related traits within the crown and the complementarity in the potential exposure patterns of the leaves during the day challenges the assumption of low trait variability within individuals. PMID:26944783

Photosynthetic thermotolerance of woody savanna species in China is correlated with leaf life span

PubMed Central

Zhang, Jiao-Lin; Poorter, L.; Hao, Guang-You; Cao, Kun-Fang

2012-01-01

Background and Aims Photosynthetic thermotolerance (PT) is important for plant survival in tropical and sub-tropical savannas. However, little is known about thermotolerance of tropical and sub-tropical wild plants and its association with leaf phenology and persistence. Longer-lived leaves of savanna plants may experience a higher risk of heat stress. Foliar Ca is related to cell integrity of leaves under stresses. In this study it is hypothesized that (1) species with leaf flushing in the hot-dry season have greater PT than those with leaf flushing in the rainy season; and (2) PT correlates positively with leaf life span, leaf mass per unit area (LMA) and foliar Ca concentration ([Ca]) across woody savanna species. Methods The temperature-dependent increase in minimum fluorescence was measured to assess PT, together with leaf dynamics, LMA and [Ca] for a total of 24 woody species differing in leaf flushing time in a valley-type savanna in south-west China. Key Results The PT of the woody savanna species with leaf flushing in the hot-dry season was greater than that of those with leaf flushing in the rainy season. Thermotolerance was positively associated with leaf life span and [Ca] for all species irrespective of the time of flushing. The associations of PT with leaf life span and [Ca] were evolutionarily correlated. Thermotolerance was, however, independent of LMA. Conclusions Chinese savanna woody species are adapted to hot-dry habitats. However, the current maximum leaf temperature during extreme heat stress (44·3 °C) is close to the critical temperature of photosystem II (45·2 °C); future global warming may increase the risk of heat damage to the photosynthetic apparatus of Chinese savanna species. PMID:22875810

SU-E-T-306: Dosimetric Comparison of Leaf with Or Without Interdigitation in Multiple Brain Metastasis VMAT Treatment Planning

DOE Office of Scientific and Technical Information (OSTI.GOV)

NONE

Purpose: To evaluate the effects of leaf with or without interdigitation in multiple brain metastasis volumetric modulated arc therapy (VMAT) plans. Methods: Twenty patients with 2 to 6 brain metastases of our hospital were retrospectively studied to be planned with dual arc VMAT using Monaco 3.3 TPS on the Elekta Synergy linear accelerator. The prescription dose of PTV was 60Gy/30 fractions. Two plans with or without leaf interdigitation were designed. The homogeneity index (HI), conformity index (CI), dose volume histograms (DVHs), monitor unit (MU), treatment time (T), the segments, the dose coverage of the target, were all evaluated. Results: Themore » plans with leaf interdigitation could achieve better CI (p<0.05) than without leaf interdigitation, while no significant difference were found in HI (p> 0.05) and the dose coverage of the target (p> 0.05).The MU,T, and the segments of the plan with leaf interdigitation were more than the plan without leaf interdigitation (p<0.05). There was no significant difference found in radiation dose of spinal cord, lenses and parotids, while the maximum dose of brain stem of leaf without interdigitation was higher than leaf with interdigitation (p< 0.05). It was worth noting that the areas of low dose regions with leaf interdigitation plan were much less than the without leaf interdigitation plan in the doublication planes (p< 0.05). Conclusion: This study shows that leaf with interdigitation has some advantages than leaf without interdigitation in multiple brain metastasis VMAT plans although the clinical relevance remains to be proven.« less

Maximum growth potential in loblolly pine: results from a 47-year-old spacing study in Hawaii

Treesearch

Lisa J. Samuelson; Thomas L. Eberhardt; John R. Butnor; Tom A. Stokes; Kurt H. Johnsen

2010-01-01

Growth, allocation to woody root biomass, wood properties, leaf physiology, and shoot morphology were examined in a 47-year-old loblolly pine (Pinus taeda L.) density trial located in Maui, Hawaii, to determine if stands continued to carry the high density, basal area, and volume reported at younger ages and to identify potential factors controlling...

Canopy architectural and physiological characterization of near-isogenic wheat lines differing in the tiller inhibition gene tin.

PubMed

Moeller, Carina; Evers, Jochem B; Rebetzke, Greg

2014-01-01

Tillering is a core constituent of plant architecture, and influences light interception to affect plant and crop performance. Near-isogenic lines (NILs) varying for a tiller inhibition (tin) gene and representing two genetic backgrounds were investigated for tillering dynamics, organ size distribution, leaf area, light interception, red: far-red ratio, and chlorophyll content. Tillering ceased earlier in the tin lines to reduce the frequencies of later primary and secondary tillers compared to the free-tillering NILs, and demonstrated the genetically lower tillering plasticity of tin-containing lines. The distribution of organ sizes along shoots varied between NILs contrasting for tin. Internode elongation commenced at a lower phytomer, and the peduncle was shorter in the tin lines. The flag leaves of tin lines were larger, and the longest leaf blades were observed at higher phytomers in the tin than in free-tillering lines. Total leaf area was reduced in tin lines, and non-tin lines invested more leaf area at mid-canopy height. The tiller economy (ratio of seed-bearing shoots to numbers of shoots produced) was 10% greater in the tin lines (0.73-0.76) compared to the free-tillering sisters (0.62-0.63). At maximum tiller number, the red: far-red ratio (light quality stimulus that is thought to induce the cessation of tillering) at the plant-base was 0.18-0.22 in tin lines and 0.09-0.11 in free-tillering lines at levels of photosynthetic active radiation of 49-53% and 30-33%, respectively. The tin lines intercepted less radiation compared to their free-tillering sisters once genotypic differences in tiller numbers had established, and maintained green leaf area in the lower canopy later into the season. Greater light extinction coefficients (k) in tin lines prior to, but reduced k after, spike emergence indicated that differences in light interception between NILs contrasting in tin cannot be explained by leaf area alone but that geometric and optical canopy properties contributed. The careful characterization of specifically-developed NILs is refining the development of a physiology-based model for tillering to improve understanding of the value of architectural traits for use in cereal improvement.

Assessment of MODIS-EVI, MODIS-NDVI and VEGETATION-NDVI composite data using agricultural measurements: an example at corn fields in western Mexico.

PubMed

Chen, Pei-Yu; Fedosejevs, Gunar; Tiscareño-López, Mario; Arnold, Jeffrey G

2006-08-01

Although several types of satellite data provide temporal information of the land use at no cost, digital satellite data applications for agricultural studies are limited compared to applications for forest management. This study assessed the suitability of vegetation indices derived from the TERRA-Moderate Resolution Imaging Spectroradiometer (MODIS) sensor and SPOT-VEGETATION (VGT) sensor for identifying corn growth in western Mexico. Overall, the Normalized Difference Vegetation Index (NDVI) composites from the VGT sensor based on bi-directional compositing method produced vegetation information most closely resembling actual crop conditions. The NDVI composites from the MODIS sensor exhibited saturated signals starting 30 days after planting, but corresponded to green leaf senescence in April. The temporal NDVI composites from the VGT sensor based on the maximum value method had a maximum plateau for 80 days, which masked the important crop transformation from vegetative stage to reproductive stage. The Enhanced Vegetation Index (EVI) composites from the MODIS sensor reached a maximum plateau 40 days earlier than the occurrence of maximum leaf area index (LAI) and maximum intercepted fraction of photosynthetic active radiation (fPAR) derived from in-situ measurements. The results of this study showed that the 250-m resolution MODIS data did not provide more accurate vegetation information for corn growth description than the 500-m and 1000-m resolution MODIS data.

Age- and size-related changes in physiological characteristics and chemical composition of Acer pseudoplatanus and Fraxinus excelsior trees.

PubMed

Abdul-Hamid, Hazandy; Mencuccini, Maurizio

2009-01-01

Forest growth is an important factor both economically and ecologically, and it follows a predictable trend with age. Generally, growth accelerates as canopies develop in young forests and declines substantially soon after maximum leaf area is attained. The causes of this decline are multiple and may be linked to age- or size-related processes, or both. Our objective was to determine the relative effects of tree age and tree size on the physiological attributes of two broadleaf species. As age and size are normally coupled during growth, an approach based on grafting techniques to separate the effects of size from those of age was adopted. Genetically identical grafted seedlings were produced from scions taken from trees of four age classes, ranging from 4 to 162 years. We found that leaf-level net photosynthetic rate per unit of leaf mass and some other leaf structural and biochemical characteristics had decreased substantially with increasing size of the donor trees in the field, whereas other gas exchange parameters expressed on a leaf area basis did not. In contrast, these parameters remained almost constant in grafted seedlings, i.e., scions taken from donor trees with different meristematic ages show no age-related trend after they were grafted onto young rootstocks. In general, the results suggested that size-related limitations triggered the declines in photosynthate production and tree growth, whereas less evidence was found to support a role of meristematic age.

Hydraulic efficiency and coordination with xylem resistance to cavitation, leaf function, and growth performance among eight unrelated Populus deltoidesxPopulus nigra hybrids.

PubMed

Fichot, Régis; Chamaillard, Sylvain; Depardieu, Claire; Le Thiec, Didier; Cochard, Hervé; Barigah, Têtè S; Brignolas, Franck

2011-03-01

Tests were carried out to determine whether variations in the hydraulic architecture of eight Populus deltoides×Populus nigra genotypes could be related to variations in leaf function and growth performance. Measurements were performed in a coppice plantation on 1-year-old shoots under optimal irrigation. Hydraulic architecture was characterized through estimates of hydraulic efficiency (the ratio of conducting sapwood area to leaf area, A(X):A(L); leaf- and xylem-specific hydraulic conductance of defoliated shoots, k(SL) and k(SS), respectively; apparent whole-plant leaf-specific hydraulic conductance, k(plant)) and xylem safety (water potential inducing 50% loss in hydraulic conductance). The eight genotypes spanned a significant range of k(SL) from 2.63  kg s(-1) m(-2) MPa(-1) to 4.18  kg s(-1) m(-2) MPa(-1), variations being mostly driven by k(SS) rather than A(X):A(L). There was a strong trade-off between hydraulic efficiency and xylem safety. Values of k(SL) correlated positively with k(plant), indicating that high-pressure flowmeter (HPFM) measurements of stem hydraulic efficiency accurately reflected whole-plant water transport efficiency of field-grown plants at maximum transpiration rate. No clear relationship could be found between hydraulic efficiency and either net CO(2) assimilation rates, water-use efficiency estimates (intrinsic water-use efficiency and carbon isotope discrimination against (13)C), or stomatal characteristics (stomatal density and stomatal pore area index). Estimates of hydraulic efficiency were negatively associated with relative growth rate. This unusual pattern, combined with the trade-off observed between hydraulic efficiency and xylem safety, provides the rationale for the positive link already reported between relative growth rate and xylem safety among the same eight P. deltoides×P. nigra genotypes.

Weak coordination between leaf structure and function among closely related tomato species.

PubMed

Muir, Christopher D; Conesa, Miquel À; Roldán, Emilio J; Molins, Arántzazu; Galmés, Jeroni

2017-03-01

Theory predicts that natural selection should favor coordination between leaf physiology, biochemistry and anatomical structure along a functional trait spectrum from fast, resource-acquisitive syndromes to slow, resource-conservative syndromes. However, the coordination hypothesis has rarely been tested at a phylogenetic scale most relevant for understanding rapid adaptation in the recent past or for the prediction of evolutionary trajectories in response to climate change. We used a common garden to examine genetically based coordination between leaf traits across 19 wild and cultivated tomato taxa. We found weak integration between leaf structure (e.g. leaf mass per area) and physiological function (photosynthetic rate, biochemical capacity and CO 2 diffusion), even though all were arrayed in the predicted direction along a 'fast-slow' spectrum. This suggests considerable scope for unique trait combinations to evolve in response to new environments or in crop breeding. In particular, we found that partially independent variation in stomatal and mesophyll conductance may allow a plant to improve water-use efficiency without necessarily sacrificing maximum photosynthetic rates. Our study does not imply that functional trait spectra, such as the leaf economics spectrum, are unimportant, but that many important axes of variation within a taxonomic group may be unique and not generalizable to other taxa. © 2016 The Authors. New Phytologist © 2016 New Phytologist Trust.

Easy Leaf Area: Automated digital image analysis for rapid and accurate measurement of leaf area.

PubMed

Easlon, Hsien Ming; Bloom, Arnold J

2014-07-01

Measurement of leaf areas from digital photographs has traditionally required significant user input unless backgrounds are carefully masked. Easy Leaf Area was developed to batch process hundreds of Arabidopsis rosette images in minutes, removing background artifacts and saving results to a spreadsheet-ready CSV file. • Easy Leaf Area uses the color ratios of each pixel to distinguish leaves and calibration areas from their background and compares leaf pixel counts to a red calibration area to eliminate the need for camera distance calculations or manual ruler scale measurement that other software methods typically require. Leaf areas estimated by this software from images taken with a camera phone were more accurate than ImageJ estimates from flatbed scanner images. • Easy Leaf Area provides an easy-to-use method for rapid measurement of leaf area and nondestructive estimation of canopy area from digital images.

Leaf area dynamics of conifer forests

DOE Office of Scientific and Technical Information (OSTI.GOV)

Margolis, H.; Oren, R.; Whitehead, D.

1995-07-01

Estimating the surface area of foliage supported by a coniferous forest canopy is critical for modeling its biological properties. Leaf area represents the surface area available for the interception of energy, the absorption of carbon dioxide, and the diffusion of water from the leaf to the atmosphere. The concept of leaf area is pertinent to the physiological and ecological dynamics of conifers at a wide range of spatial scales, from individual leaves to entire biomes. In fact, the leaf area of vegetation at a global level can be thought of as a carbon-absorbing, water-emitting membrane of variable thickness, which canmore » have an important influence on the dynamics and chemistry of the Earth`s atmosphere over both the short and the long term. Unless otherwise specified, references to leaf area herein refer to projected leaf area, i.e., the vertical projection of needles placed on a flat plane. Total leaf surface area is generally from 2.0 to 3.14 times that of projected leaf area for conifers. It has recently been suggested that hemisurface leaf area, i.e., one-half of the total surface area of a leaf, a more useful basis for expressing leaf area than is projected area. This chapter is concerned with the dynamics of coniferous forest leaf area at different spatial and temporal scales. In the first part, we consider various hypotheses related to the control of leaf area development, ranging from simple allometric relations with tree size to more complex mechanistic models that consider the movement of water and nutrients to tree canopies. In the second part, we consider various aspects of leaf area dynamics at varying spatial and temporal scales, including responses to perturbation, seasonal dynamics, genetic variation in crown architecture, the responses to silvicultural treatments, the causes and consequences of senescence, and the direct measurement of coniferous leaf area at large spatial scales using remote sensing.« less

Leaf-IT: An Android application for measuring leaf area.

PubMed

Schrader, Julian; Pillar, Giso; Kreft, Holger

2017-11-01

The use of plant functional traits has become increasingly popular in ecological studies because plant functional traits help to understand key ecological processes in plant species and communities. This also includes changes in diversity, inter- and intraspecific interactions, and relationships of species at different spatiotemporal scales. Leaf traits are among the most important traits as they describe key dimensions of a plant's life history strategy. Further, leaf area is a key parameter with relevance for other traits such as specific leaf area, which in turn correlates with leaf chemical composition, photosynthetic rate, leaf longevity, and carbon investment. Measuring leaf area usually involves the use of scanners and commercial software and can be difficult under field conditions. We present Leaf-IT, a new smartphone application for measuring leaf area and other trait-related areas. Leaf-IT is free, designed for scientific purposes, and runs on Android 4 or higher. We tested the precision and accuracy using objects with standardized area and compared the area measurements of real leaves with the well-established, commercial software WinFOLIA using the Altman-Bland method. Area measurements of standardized objects show that Leaf-IT measures area with high accuracy and precision. Area measurements with Leaf-IT of real leaves are comparable to those of WinFOLIA. Leaf-IT is an easy-to-use application running on a wide range of smartphones. That increases the portability and use of Leaf-IT and makes it possible to measure leaf area under field conditions typical for remote locations. Its high accuracy and precision are similar to WinFOLIA. Currently, its main limitation is margin detection of damaged leaves or complex leaf morphologies.

Hydrostatic constraints on morphological exploitation of light in tall Sequoia sempervirens trees.

PubMed

Ishii, Hiroaki T; Jennings, Gregory M; Sillett, Stephen C; Koch, George W

2008-07-01

We studied changes in morphological and physiological characteristics of leaves and shoots along a height gradient in Sequoia sempervirens, the tallest tree species on Earth, to investigate whether morphological and physiological acclimation to the vertical light gradient was constrained by hydrostatic limitation in the upper crown. Bulk leaf water potential (Psi) decreased linearly and light availability increased exponentially with increasing height in the crown. During the wet season, Psi was lower in the outer than inner crown. C isotope composition of leaves (delta(13)C) increased with increasing height indicating greater photosynthetic water use efficiency in the upper crown. Leaf and shoot morphology changed continuously with height. In contrast, their relationships with light availability were discontinuous: morphological characteristics did not correspond to increasing light availability above 55-85 m. Mass-based chlorophyll concentration (chl) decreased with increasing height and increasing light availability. In contrast, area-based chl remained constant or increased with increasing height. Mass-based maximum rate of net photosynthesis (P (max)) decreased with increasing height, whereas area-based P (max) reached maximum at 78.4 m and decreased with increasing height thereafter. Mass-based P (max) increased with increasing shoot mass per area (SMA), whereas area-based P (max) was not correlated with SMA in the upper crown. Our results suggest that hydrostatic limitation of morphological development constrains exploitation of light in the upper crown and contributes to reduced photosynthetic rates and, ultimately, reduced height growth at the tops of tall S. sempervirens trees.

Relating Stomatal Conductance to Leaf Functional Traits.

PubMed

Kröber, Wenzel; Plath, Isa; Heklau, Heike; Bruelheide, Helge

2015-10-12

Leaf functional traits are important because they reflect physiological functions, such as transpiration and carbon assimilation. In particular, morphological leaf traits have the potential to summarize plants strategies in terms of water use efficiency, growth pattern and nutrient use. The leaf economics spectrum (LES) is a recognized framework in functional plant ecology and reflects a gradient of increasing specific leaf area (SLA), leaf nitrogen, phosphorus and cation content, and decreasing leaf dry matter content (LDMC) and carbon nitrogen ratio (CN). The LES describes different strategies ranging from that of short-lived leaves with high photosynthetic capacity per leaf mass to long-lived leaves with low mass-based carbon assimilation rates. However, traits that are not included in the LES might provide additional information on the species' physiology, such as those related to stomatal control. Protocols are presented for a wide range of leaf functional traits, including traits of the LES, but also traits that are independent of the LES. In particular, a new method is introduced that relates the plants' regulatory behavior in stomatal conductance to vapor pressure deficit. The resulting parameters of stomatal regulation can then be compared to the LES and other plant functional traits. The results show that functional leaf traits of the LES were also valid predictors for the parameters of stomatal regulation. For example, leaf carbon concentration was positively related to the vapor pressure deficit (vpd) at the point of inflection and the maximum of the conductance-vpd curve. However, traits that are not included in the LES added information in explaining parameters of stomatal control: the vpd at the point of inflection of the conductance-vpd curve was lower for species with higher stomatal density and higher stomatal index. Overall, stomata and vein traits were more powerful predictors for explaining stomatal regulation than traits used in the LES.

Hydraulic architecture and photoinhibition influence spatial distribution of the arborescent palm Euterpe edulis in subtropical forests.

PubMed

Gatti, M Genoveva; Campanello, Paula I; Villagra, Mariana; Montti, Lía; Goldstein, Guillermo

2014-06-01

Physiological characteristics of saplings can be considered one of the most basic constraints on species distribution. The shade-tolerant arborescent palm Euterpe edulis Mart. is endemic to the Atlantic Forest of Argentina, Brazil and Paraguay. At a local scale, saplings of this species growing in native forests are absent in gaps. We tested the hypothesis whether sensitivity to photoinhibition or hydraulic architecture constrains the distribution of E. edulis saplings in sun-exposed forest environments. Using shade houses and field studies, we evaluated growth, survival, hydraulic traits and the susceptibility of Photosystem II to photoinhibition in E. edulis saplings under different growth irradiances. Survival rates in exposed sites in the field were very low (a median of 7%). All saplings exhibited photoinhibition when exposed to high radiation levels, but acclimation to a high radiation environment increased the rate of recovery. Petiole hydraulic conductivity was similar across treatments regardless of whether it was expressed per petiole cross-sectional area or per leaf area. At the plant level, investment in conductive tissues relative to leaf area (Huber values) increased with increasing irradiance. Under high irradiance conditions, plants experienced leaf water potentials close to the turgor-loss point, and leaf hydraulic conductance decreased by 79% relative to its maximum value. Euterpe edulis saplings were able to adjust their photosynthetic traits to different irradiance conditions, whereas hydraulic characteristics at the leaf level did not change across irradiance treatments. Our results indicate that uncoupling between water demand and supply to leaves apparently associated with high resistances to water flow at leaf insertion points, in addition to small stems with low water storage capacity, weak stomatal control and high vulnerability of leaves to hydraulic dysfunction, are the main ecophysiological constraints that prevent the growth and survival of E. edulis saplings in gaps in the native forest where native lianas and bamboos show aggressive growth. © The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Dynamic-MLC leaf control utilizing on-flight intensity calculations: a robust method for real-time IMRT delivery over moving rigid targets.

PubMed

McMahon, Ryan; Papiez, Lech; Rangaraj, Dharanipathy

2007-08-01

An algorithm is presented that allows for the control of multileaf collimation (MLC) leaves based entirely on real-time calculations of the intensity delivered over the target. The algorithm is capable of efficiently correcting generalized delivery errors without requiring the interruption of delivery (self-correcting trajectories), where a generalized delivery error represents anything that causes a discrepancy between the delivered and intended intensity profiles. The intensity actually delivered over the target is continually compared to its intended value. For each pair of leaves, these comparisons are used to guide the control of the following leaf and keep this discrepancy below a user-specified value. To demonstrate the basic principles of the algorithm, results of corrected delivery are shown for a leading leaf positional error during dynamic-MLC (DMLC) IMRT delivery over a rigid moving target. It is then shown that, with slight modifications, the algorithm can be used to track moving targets in real time. The primary results of this article indicate that the algorithm is capable of accurately delivering DMLC IMRT over a rigid moving target whose motion is (1) completely unknown prior to delivery and (2) not faster than the maximum MLC leaf velocity over extended periods of time. These capabilities are demonstrated for clinically derived intensity profiles and actual tumor motion data, including situations when the target moves in some instances faster than the maximum admissible MLC leaf velocity. The results show that using the algorithm while calculating the delivered intensity every 50 ms will provide a good level of accuracy when delivering IMRT over a rigid moving target translating along the direction of MLC leaf travel. When the maximum velocities of the MLC leaves and target were 4 and 4.2 cm/s, respectively, the resulting error in the two intensity profiles used was 0.1 +/- 3.1% and -0.5 +/- 2.8% relative to the maximum of the intensity profiles. For the same target motion, the error was shown to increase rapidly as (1) the maximum MLC leaf velocity was reduced below 75% of the maximum target velocity and (2) the system response time was increased.

Constructing seasonal LAI trajectory by data-model fusion for global evergreen needle-leaf forests

NASA Astrophysics Data System (ADS)

Wang, R.; Chen, J.; Mo, G.

2010-12-01

For decades, advancements in optical remote sensors made it possible to produce maps of a biophysical parameter--the Leaf Area Index (LAI), which is critically necessary in regional and global modeling of exchanges of carbon, water, energy and other substances, across large areas in a fast way. Quite a few global LAI products have been generated since 2000, e.g. GLOBCARBON (Deng et al., 2006), MODIS Collection 5 (Shabanov et al., 2007), CYCLOPES (Baret et al., 2007), etc. Albeit these progresses, the basic physics behind the technology restrains it from accurate estimation of LAI in winter, especially for northern high-latitude evergreen needle-leaf forests. Underestimation of winter LAI in these regions has been reported in literature (Yang et al., 2000; Cohen et al., 2003; Tian et al., 2004; Weiss et al., 2007; Pisek et al., 2007), and the distortion is usually attributed to the variations of canopy reflectance caused by understory change (Weiss et al., 2007) as well as by the presence of ice and snow on leaves and ground (Cohen, 2003; Tian et al., 2004). Seasonal changes in leaf pigments can also be another reason for low LAI retrieved in winter. Low conifer LAI values in winter retrieved from remote sensing make them unusable for surface energy budget calculations. To avoid these drawbacks of remote sensing approaches, we attempt to reconstruct the seasonal LAI trajectory through model-data fusion. A 1-degree LAI map of global evergreen needle-leaf forests at 10-day interval is produced based on the carbon allocation principle in trees. With net primary productivity (NPP) calculated by the Boreal Ecosystems Productivity Simulator (BEPS) (Chen et al., 1999), carbon allocated to needles is quantitatively evaluated and then can be further transformed into LAI using the specific leaf area (SLA). A leaf-fall scheme is developed to mimic the carbon loss caused by falling needles throughout the year. The seasonally maximum LAI from remote sensing data for each pixel is used as an anchor point of the LAI trajectory. Ground data are used for validation. The resulting LAI does not show strong seasonality within a year, which is reasonable for evergreen needle-leaf forests with known leaf longevity.

Arctic Climate during Eocene Hyperthermals: Wet Summers on Ellesmere Island?

NASA Astrophysics Data System (ADS)

Greenwood, D. R.; West, C. K.; Basinger, J. F.

2012-12-01

Previous work has shown that during the late Paleocene to middle Eocene, mesothermal conditions (i.e., MAT ~12-15° C) and high precipitation (MAP > 150cm/yr) characterized Arctic climates - an Arctic rain forest. Recent analyses of Arctic Eocene wood stable isotope chemistry are consistent with the annual and seasonal temperature estimates from leaf physiognomy and nearest living relative analogy from fossil plants, including the lack of freezing winters, but is interpreted as showing that there was a summer peak in precipitation - modern analogs are best sought on the summer-wet east coasts (e.g., China, Japan, South Korea) not the winter-wet west coasts of present-day northern temperate continents (e.g., Pacific northwest of North America). Highly seasonal 'monsoon-type' summer-wet precipitation regimes (i.e., summer precip./winter precip. > 3.0) seem to characterize Eocene hyperthermal conditions in several regions of the earth, including the Arctic and Antarctic, based on both climate model sensitivity experiments and the paleoclimate proxy evidence. The leaf physiognomy proxy previously applied to estimate Arctic Paleogene precipitation was leaf area analysis (LAA), a correlation between mean leaf size in woody dicot vegetation and annual precipitation. New data from modern monsoonal sites, however demonstrates that for deciduous-dicot dominated vegetation, summer precipitation determines mean leaf size, not annual totals, and therefore that under markedly seasonal precipitation and/or light regimes that summer precipitation is being estimated using LAA. Presented here is a new analysis of a leaf macrofloras from 3 separate florules of the Margaret Formation (Split Lake, Stenkul Fiord and Strathcona Fiord) from Ellesmere Island that are placed stratigraphically as early Eocene, and likely fall within Eocene thermal maximum 1 (ETM1; = the 'PETM') or ETM2. These floras are each characterized by a mix of large-leafed and small-leafed dicot taxa, with overall mean leaf size across all leaf morphotypes comparable to that previously reported for late Paleocene to middle Eocene floras from Ellesmere and Axel Heiberg islands of Nunavut. Applying the conventional leaf area analysis to the putatively ETM1 floras yielded estimates of mean annual precipitation 100-200cm/yr, consistent with the previous reports for the late Paleocene to middle Eocene. CLAMP analysis applied to these floras yields growing season precipitation comparable to the annual precipitation estimate from leaf area analysis. These data are interpreted as reflecting high summer precipitation in the Arctic during the late Paleocene to middle Eocene, including ETM1, as precipitation in the dark polar winter months will have had no effect on leaf size while the trees were dormant, corroborating the results from Eocene wood chemistry. High summer precipitation (i.e., light-season = wettest season) in the Eocene Arctic during hyperthermals would have contributed to regional warmth.

Leaf maximum photosynthetic rate and venation are linked by hydraulics.

PubMed

Brodribb, Tim J; Feild, Taylor S; Jordan, Gregory J

2007-08-01

Leaf veins are almost ubiquitous across the range of terrestrial plant diversity, yet their influence on leaf photosynthetic performance remains uncertain. We show here that specific physical attributes of the vascular plumbing network are key limiters of the hydraulic and photosynthetic proficiency of any leaf. Following the logic that leaf veins evolved to bypass inefficient water transport through living mesophyll tissue, we examined the hydraulic pathway beyond the distal ends of the vein system as a possible limiter of water transport in leaves. We tested a mechanistic hypothesis that the length of this final traverse, as water moves from veins across the mesophyll to where it evaporates from the leaf, governs the hydraulic efficiency and photosynthetic carbon assimilation of any leaf. Sampling 43 species across the breadth of plant diversity from mosses to flowering plants, we found that the post-vein traverse as determined by characters such as vein density, leaf thickness, and cell shape, was strongly correlated with the hydraulic conductivity and maximum photosynthetic rate of foliage. The shape of this correlation provided clear support for the a priori hypothesis that vein positioning limits photosynthesis via its influence on leaf hydraulic efficiency.

Apoplastic infusion of sucrose into stem internodes during female flowering does not increase grain yield in maize plants grown under nitrogen-limiting conditions.

PubMed

Peng, Yunfeng; Li, Chunjian; Fritschi, Felix B

2013-08-01

Nitrogen (N) limitation reduces leaf growth and photosynthetic rates of maize (Zea mays), and constrains photosynthate translocation to developing ears. Additionally, the period from about 1 week before to 2 weeks after silking is critical for establishing the reproductive sink capacity necessary to attain maximum yield. To investigate the influence of carbohydrate availability in plants of differing N status, a greenhouse study was performed in which exogenous sucrose (Suc) was infused around the time of silking into maize stems grown under different N regimes. N deficiency significantly reduced leaf area, leaf longevity, leaf chlorophyll content and photosynthetic rate. High N-delayed leaf senescence, particularly of the six uppermost leaves, compared to the other two N treatments. While N application increased ear leaf soluble protein concentration, it did not influence glucose and suc concentrations. Interestingly, ear leaf starch concentration decreased with increasing N application. Infusion of exogenous suc tended to increase non-structural carbohydrate concentrations in the developing ears of all N treatments at silking and 6 days after silking. However, leaf photosynthetic rates were not affected by suc infusion, and suc infusion failed to increase grain yield in any N treatment. The lack of an effect of suc infusion on ear growth and the high ear leaf starch concentration of N-deficient maize, suggest that yield reduction under N deficiency may not be due to insufficient photosynthate availability to the developing ear during silking, and that yield reduction under N deficiency may be determined at an earlier growth stage. Copyright © Physiologia Plantarum 2012.

Ecological Impact of Climate Change on Leaf Economic Strategies Across the Paleocene- Eocene Thermal Maximum, Bighorn Basin, Wyoming

NASA Astrophysics Data System (ADS)

Royer, D. L.; Currano, E. D.; Wilf, P.; Wing, S. L.; Labandeira, C. C.; Lovelock, E. C.

2007-12-01

Deciphering the ecological impacts of climate change is a key priority for paleontologists and ecologists alike. An important ecological metric in vegetated settings is the leaf economics spectrum, which represents an adaptive continuum running from rapid resource acquisition to maximized resource retention. This spectrum is comprised of a large number of coordinated traits, including leaf mass per area (LMA), leaf lifespan, photosynthetic rate, nutrient concentration, and palatability to herbivores. Here we apply a recently developed technique for reconstructing LMA to a suite of four isotaphonomic fossil plant sites spanning the Paleocene-Eocene thermal maximum (PETM) in the Bighorn Basin, Wyoming, USA. This technique is based on the biomechanical scaling between petiole width and leaf mass, and it has been calibrated with 65 present-day sites from five continents and tested on two well-known Eocene fossil localities (Bonanza, Utah and Republic, Washington). There are no significant differences in LMA among plants across the PETM. This stasis is present despite a backdrop of extreme climate change during the PETM in this region, including a three-to-four-fold increase in atmospheric CO2, an ~5 °C rise in temperature, and possible drying. Moreover, quantitative measurements of insect herbivory show, on average, a two-fold increase during the PETM relative to before and after the event. We interpret our results to suggest that leaf-economic relationships can, in some situations, partially decouple. More specifically, our documented increase in insect herbivory during the PETM with no concomitant decrease in LMA implies that during this interval less carbon was being captured by plants per unit of investment. Because the rate and magnitude of climate change during the PETM is similar to present-day anthropogenic changes, our results may provide clues for predictions of ecological impacts in the near future.

Leaf-trait responses to irrigation of the endemic fog-oasis tree Myrcianthes ferreyrae: can a fog specialist benefit from regular watering?

PubMed

Ramírez, David A; Balaguer, Luis; Mancilla, Rosa; González, Virginia; Coaguila, Daniel; Talavera, Carmelo; Villegas, Luis; Ortega, Aldo; Jiménez, Percy; Moreno, José M

2012-01-01

Myrcianthes ferreyrae is an endemic, endangered species, with a small number of individuals located only in hyperarid, fog-oases known as lomas along the Peruvian desert in southern Peru, where fog is the main source of water. Following centuries of severe deforestation, reforestation with this native species was conducted in the Atiquipa lomas, Arequipa-Perú. On five slopes, five 2-year-old seedlings were irrigated monthly with water trapped by raschel-mesh fog collectors, supplementing natural rainfall with 0, 20, 40, 60 and 80 mm month(-1) from February to August 2008. We measured plant growth, increment in basal diameter, height and five leaf traits: leaf mass area (LMA), leaf carbon isotope composition (δ(13)C), nitrogen per leaf area, total leaf carbon and stomatal density; which are indicative of the physiological changes resulting from increased water supply. Plant growth rates, estimated from the variation of either shoot basal diameter or maximum height, were highly correlated with total biomass. Only LMA and δ(13)C were higher in irrigated than in control plants, but we found no further differences among irrigation treatments. This threshold response suggests an on-off strategy fitted to exploit pulses of fog water, which are always limited in magnitude in comparison with natural rain. The absence of a differential response to increased water supply is in agreement with the low phenotypic plasticity expected in plants from very stressful environments. Our results have practical implications for reforestation projects, since irrigating with 20 mm per month is sufficient to achieve the full growth capacity of this species.

Vertical leaf area distribution, light transmittance, and application of the Beer-Lambert Law in four mature hardwood stands in the southern Appalachians

Treesearch

James M. Vose; Neal H. Sullivan; Barton D. Clinton; Paul V. Bolstad

1995-01-01

We quantified stand leaf area index and vertical leaf area distribution, and developed canopy extinction coefficients (k), in four mature hardwood stands. Leaf area index, calculated from litter fall and specific leaf area (cm²·g-1), ranged from 4.3 to 5.4 m²·m-2. In three of the four stands, leaf area was distributed in...

Estimating Net Primary Productivity Using Satellite and Ancillary Data

NASA Technical Reports Server (NTRS)

Choudhury, B. J.; Houser, Paul (Technical Monitor)

2001-01-01

The net primary productivity (C) or annual rate of carbon accumulation per unit ground area by terrestrial plant communities is the difference of the rate of gross photosynthesis (A(sub g)) and autotrophic respiration (R) per unit ground area. Although available observations show that R is a large and variable fraction of A(sub g), viz., 0.3 to 0.7, it is generally recognized that much uncertainties exist in this fraction due to difficulties associated with the needed measurements. Additional uncertainties arise when these measurements are extrapolated to regional or global land surface using empirical equations, for example, using regression equations relating C to mean annual precipitation and air temperature. Here, a process-based approach has been taken to calculate A(sub g) and R using satellite and ancillary data. A(sub g) has been expressed as a product of radiation use efficiency, magnitude of intercepted photosynthetically active radiation (PAR), and normalized by stresses due to soil water shortage and air temperature away from the optimum range. A biophysical model has been used to determine the radiation use efficiency from the maximum rate of carbon assimilation by a leaf, foliage temperature, and the fraction of diffuse PAR incident on a canopy. All meteorological data (PAR, air temperature, precipitation, etc.) needed for the calculation are derived from satellite observations, while a land use, land cover data (based on satellite and ground measurements) have been used to assess the maximum rate of carbon assimilation by a leaf of varied cover type based on field measurements. R has been calculated as the sum of maintenance and growth components. The maintenance respiration of foliage and live fine roots at a standard temperature of different land cover has been determined from their nitrogen content using field and satellite measurements, while that of living fraction of woody stem (viz., sapwood) from the seasonal maximum leaf area index as determined from satellite observations. These maintenance respiration values were then adjusted to that corresponding to air temperature according to a prescribed non-linear variation of respiration with temperature. The growth respiration has been calculated from the difference of Ag and maintenance respiration, according to the two-compartment model. The results of calculations will be reported for 36 consecutive months (1987-1989) over large contiguous areas (ca. 10(exp 5) sq km) Of agricultural land and tropical humid evergreen forests, and compared with available field data.

Performance of sorghum cultivars for biomass quality and biomethane yield grown in semi-arid area of Pakistan.

PubMed

Hassan, Muhammad Umair; Chattha, Muhammad Umer; Mahmood, Athar; Sahi, Shahbaz Talib

2018-05-01

Biomass is a promising renewable energy source and its significance is escalating in the context of climate change and depletion of fossil foils. This study was conducted for two consecutive years 2016 and 2017, using five sorghum cultivars, i.e., JS-263, Jawar-2011, Hagari, JS-2002, and YS-2016, in order to determine the best cultivars in terms of dry matter yield, chemical composition, and biomethane yield grown under semi-arid conditions in Pakistan. The results revealed that sorghum cultivars responded differently in terms of growth, biomass yield, chemical composition, and methane yield. Cultivars Jawar-2011 produced maximum leaf area index, leaf area duration, crop growth rate, plant height, and leaves per plant, however, they were comparable with Sorghum-2016, whereas cultivar JS-2002 performed poorly among the tested cultivars. Similarly, cultivar Jawar-2011 produced maximum dry matter yield (16.37 t ha -1 ) similar to that of YS-2016, further cultivar JS-2002 performed poorly and gave lower dry matter yield (12.87 t ha -1 ). The maximum protein concentration (10.95), neutral detergent fibers (61.20), and lignin contents (5.55) found in Jawar-2011 were comparable with those in YS-2016, while the lowest neutral detergent fiber and lignin contents were found in JS-2002. Although JS-2002 produced the highest specific methane yield per kilogram of volatile solids, it was overcompensated by Jawar-2011 owing to higher dry matter yield per hectare. These results suggested that cultivar Jawar-2011 can be grown successfully in semi-arid conditions of Pakistan in order to get good biomass yield along with higher methane yield.

Different leaf cost-benefit strategies of ferns distributed in contrasting light habitats of sub-tropical forests.

PubMed

Zhu, Shi-Dan; Li, Rong-Hua; Song, Juan; He, Peng-Cheng; Liu, Hui; Berninger, Frank; Ye, Qing

2016-03-01

Ferns are abundant in sub-tropical forests in southern China, with some species being restricted to shaded understorey of natural forests, while others are widespread in disturbed, open habitats. To explain this distribution pattern, we hypothesize that ferns that occur in disturbed forests (FDF) have a different leaf cost-benefit strategy compared with ferns that occur in natural forests (FNF), with a quicker return on carbon investment in disturbed habitats compared with old-growth forests. We chose 16 fern species from contrasting light habitats (eight FDF and eight FNF) and studied leaf functional traits, including leaf life span (LLS), specific leaf area (SLA), leaf nitrogen and phosphorus concentrations (N and P), maximum net photosynthetic rates (A), leaf construction cost (CC) and payback time (PBT), to conduct a leaf cost-benefit analysis for the two fern groups. The two groups, FDF and FNF, did not differ significantly in SLA, leaf N and P, and CC, but FDF had significantly higher A, greater photosynthetic nitrogen- and phosphorus-use efficiencies (PNUE and PPUE), and shorter PBT and LLS compared with FNF. Further, across the 16 fern species, LLS was significantly correlated with A, PNUE, PPUE and PBT, but not with SLA and CC. Our results demonstrate that leaf cost-benefit analysis contributes to understanding the distribution pattern of ferns in contrasting light habitats of sub-tropical forests: FDF employing a quick-return strategy can pre-empt resources and rapidly grow in the high-resource environment of open habitats; while a slow-return strategy in FNF allows their persistence in the shaded understorey of old-growth forests. © The Author 2015. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Different leaf cost–benefit strategies of ferns distributed in contrasting light habitats of sub-tropical forests

PubMed Central

Zhu, Shi-Dan; Li, Rong-Hua; Song, Juan; He, Peng-Cheng; Liu, Hui; Berninger, Frank; Ye, Qing

2016-01-01

Background and Aims Ferns are abundant in sub-tropical forests in southern China, with some species being restricted to shaded understorey of natural forests, while others are widespread in disturbed, open habitats. To explain this distribution pattern, we hypothesize that ferns that occur in disturbed forests (FDF) have a different leaf cost–benefit strategy compared with ferns that occur in natural forests (FNF), with a quicker return on carbon investment in disturbed habitats compared with old-growth forests. Methods We chose 16 fern species from contrasting light habitats (eight FDF and eight FNF) and studied leaf functional traits, including leaf life span (LLS), specific leaf area (SLA), leaf nitrogen and phosphorus concentrations (N and P), maximum net photosynthetic rates (A), leaf construction cost (CC) and payback time (PBT), to conduct a leaf cost–benefit analysis for the two fern groups. Key Results The two groups, FDF and FNF, did not differ significantly in SLA, leaf N and P, and CC, but FDF had significantly higher A, greater photosynthetic nitrogen- and phosphorus-use efficiencies (PNUE and PPUE), and shorter PBT and LLS compared with FNF. Further, across the 16 fern species, LLS was significantly correlated with A, PNUE, PPUE and PBT, but not with SLA and CC. Conclusions Our results demonstrate that leaf cost–benefit analysis contributes to understanding the distribution pattern of ferns in contrasting light habitats of sub-tropical forests: FDF employing a quick-return strategy can pre-empt resources and rapidly grow in the high-resource environment of open habitats; while a slow-return strategy in FNF allows their persistence in the shaded understorey of old-growth forests. PMID:26684751

[Latitude variation mechanism of leaf traits of Metasequoia glyptostroboides in eastern coastal China].

PubMed

Guo, Wei Hong; Wang, Hua; Yu, Mu Kui; Wu, Tong Gui; Han, You Zhi

2017-03-18

We analyzed the rules of Metasequoia glyptostroboides along with latitude, including leaf length, leaf width, leaf perimeter, leaf area, ratio of leaf length to width, specific leaf area (SLA), and leaf dry mass based on eight stands growing at different latitudes in the coastal area of eastern China, as well as their relationships with climatic and soil factors. The results showed that the leaf length, leaf width and leaf perimeter increased with increasing latitude, while the leaf area and SLA firstly increased and then decreased. The mean annual temperature and annual precipitation were the major environmental factors affecting the leaf traits along latitude gradient. With the increase of soil N content, the SLA decreased firstly and then increased, while the leaf mass decreased significantly. With the increase of soil P content, the SLA increased, and the leaf mass decreased significantly.

Actual and potential transpiration and carbon assimilation in an irrigated poplar plantation.

PubMed

Kim, Hyun-Seok; Oren, Ram; Hinckley, Thomas M

2008-04-01

We examined the tradeoffs between stand-level water use and carbon uptake that result when biomass production of trees in plantations is maximized by removing nutrient and water limitations. A Populus trichocarpa Torr. x P. deltoides Bartr. & Marsh. plantation was irrigated and received frequent additions of nutrients to optimize biomass production. Sap flux density was measured continuously over four of the six growing-season months, supplemented with periodic measurements of leaf gas exchange and water potential. Measurements of tree diameter and height were used to estimate leaf area and biomass production based on allometric relationships. Sap flux was converted to canopy conductance and analyzed with an empirical model to isolate the effects of water limitation. Actual and soil-water-unlimited potential CO(2) uptakes were estimated with a canopy conductance constrained carbon assimilation (4C-A) scheme, which couples actual or potential canopy conductance with vertical gradients of light distribution, leaf-level conductance, maximum Rubisco capacity and maximum electron transport. Net primary production (NPP) was about 43% of gross primary production (GPP); when estimated for individual trees, this ratio was independent of tree size. Based on the NPP/GPP ratio, we found that current irrigation reduced growth by about 18% compared with growth with no water limitation. To achieve maximum growth, however, would require 70% more water for transpiration, and would reduce water-use efficiency by 27%, from 1.57 to 1.15 g stem wood C kg(-1) water. Given the economic and social values of water, plantation managers appear to have optimized water use.

Temporal pattern in biometrics and nutrient stoichiometry of the intertidal seagrass Zostera japonica and its adaptation to air exposure in a temperate marine lagoon (China): Implications for restoration and management.

PubMed

Zhang, Xiaomei; Zhou, Yi; Liu, Peng; Wang, Feng; Liu, Bingjian; Liu, Xujia; Yang, Hongsheng

2015-05-15

In coastal areas of China, the seagrass Zostera japonica has drastically decreased in the past decades. Swan Lake is an exception, where we found extensive areas of Z. japonica beds. The growth of Z. japonica in the lagoon exhibited strong seasonal variation. The maximum shoot density of 9880±2786 shoots m(-2) occurred in August. The maximum specific growth rate (SGR) of 4.99±1.99%⋅d(-1) was recorded in June 2012. SGR might be a good parameter for assessing the growth status of Z. japonica population. N and P contents in the rhizome were significantly lower than those in the leaf and leaf sheath. Lower C/P ratios suggested P enrichment of the seagrass. The occurrence of Z. japonica in Swan Lake was featured by adapting to the intertidal harsh environments. The transplantation method using sectioned rhizomes would be a potential way for restoration of degraded Z. japonica beds. The establishment of the Rongcheng Swan National Nature Reserve in China has contributed to the survival and expansion of Z. japonica in Swan Lake. Copyright © 2015 Elsevier Ltd. All rights reserved.

Rapid photosynthetic acclimation of Shorea johorensis seedlings after logging disturbance in Central Kalimantan.

PubMed

Clearwater, M J; Susilawaty, R; Effendi, R; van Gardingen, P R

1999-12-01

This study examined the photosynthetic acclimation of pre-existing Shorea johorensis (Dipterocarpaceae) seedlings to the change in conditions that occurs at the time of logging in Central Kalimantan, Indonesia. The hypothesis was that the seedlings would be unable to acclimate beyond partially open conditions after canopy disturbance caused by logging, therefore limiting the potential for regeneration in the most open areas. Bleaching and reductions in the predawn ratio of variable to maximum fluorescence (F v /F m ) indicated chronic photoinhibition and damage to the previously shade-adapted leaves of seedlings in an area logged 2 weeks earlier. The majority of seedlings in partially open and open environments of an area logged 3 months earlier were already growing fast. Leaves that had developed in the new environment showed only small reductions in predawn F v /F m and large increases in the light saturated rate of photosynthesis (A max ) per unit area when compared to shaded seedlings. Leaves in the most open environments had higher but more variable nitrogen concentrations, A max per unit area and A max per unit mass when compared to seedlings in partially open environments. Increases in dark respiration were disproportionately large compared to increases in A max , and may have been the result of increased investment in photoprotective mechanisms. The response of stomatal conductance to the vapour pressure deficit and leaf temperature was examined, but it suggested only a 10% reduction in daily leaf level carbon gain in open environments. The ratio of leaf area to fine root mass was highest in shade-suppressed and newly exposed seedlings, suggesting a potential hydraulic limitation to transpiration during acclimation. However, rainfall during this period was high and leaf water potentials did not differ between disturbed and undisturbed environments. S. johorensis seedlings were capable of significant acclimation to conditions more extreme than partial canopy opening. Low seedling density after logging during the wet season cannot be explained by a limited potential for photosynthetic acclimation.

Light interception in species with different functional groups coexisting in moorland plant communities.

PubMed

Kamiyama, Chiho; Oikawa, Shimpei; Kubo, Takuya; Hikosaka, Kouki

2010-11-01

Competition for light is one of the most essential mechanisms affecting species composition. It has been suggested that similar light acquisition efficiency (Φ(mass), absorbed photon flux per unit aboveground mass) may contribute to species coexistence in multi-species communities. On the other hand, it is known that traits related with light acquisition vary among functional groups. We studied whether Φ(mass) was similar among species with different functional groups coexisting in moorland communities. We conducted stratified clipping in midsummer when the stand biomass reached a maximum. Light partitioning among species was estimated using a model accounting for both direct and diffuse light. Evergreen species were found to have a significantly lower Φ(mass) than deciduous species, which resulted from their lower absorbed photon flux per unit leaf area and lower specific leaf area. Shrubs had a smaller leaf mass fraction, but their Φ(mass) was not lower than that of herbs because they had a higher leaf position due to the presence of wintering stems. Species with vertical leaves had a higher Φ(mass) than those with horizontal leaves despite vertical leaves being a decided disadvantage in terms of light absorption. This higher Φ(mass) was achieved by a greater leaf height in species with vertical leaves. Our results clearly demonstrate that light acquisition efficiency was different among the functional groups. However, the trend observed is not necessarily the same as that expected based on prior knowledge, suggesting that disadvantages in some traits for light acquisition efficiency are partly compensated for by other traits.

Species-Independent Down-Regulation of Leaf Photosynthesis and Respiration in Response to Shading: Evidence from Six Temperate Tree Species

PubMed Central

Chen, Anping; Lichstein, Jeremy W.; Osnas, Jeanne L. D.; Pacala, Stephen W.

2014-01-01

The ability to down-regulate leaf maximum net photosynthetic capacity (Amax) and dark respiration rate (Rdark) in response to shading is thought to be an important adaptation of trees to the wide range of light environments that they are exposed to across space and time. A simple, general rule that accurately described this down-regulation would improve carbon cycle models and enhance our understanding of how forest successional diversity is maintained. In this paper, we investigated the light response of Amax and Rdark for saplings of six temperate forest tree species in New Jersey, USA, and formulated a simple model of down-regulation that could be incorporated into carbon cycle models. We found that full-sun values of Amax and Rdark differed significantly among species, but the rate of down-regulation (proportional decrease in Amax or Rdark relative to the full-sun value) in response to shade was not significantly species- or taxon-specific. Shade leaves of sun-grown plants appear to follow the same pattern of down-regulation in response to shade as leaves of shade-grown plants. Given the light level above a leaf and one species-specific number (either the full-sun Amax or full-sun Rdark), we provide a formula that can accurately predict the leaf's Amax and Rdark. We further show that most of the down regulation of per unit area Rdark and Amax is caused by reductions in leaf mass per unit area (LMA): as light decreases, leaves get thinner, while per unit mass Amax and Rdark remain approximately constant. PMID:24727745

The expression of light-related leaf functional traits depends on the location of individual leaves within the crown of isolated Olea europaea trees.

PubMed

Escribano-Rocafort, Adrián G; Ventre-Lespiaucq, Agustina B; Granado-Yela, Carlos; Rubio de Casas, Rafael; Delgado, Juan A; Balaguer, Luis

2016-04-01

The spatial arrangement and expression of foliar syndromes within tree crowns can reflect the coupling between crown form and function in a given environment. Isolated trees subjected to high irradiance and concomitant stress may adjust leaf phenotypes to cope with environmental gradients that are heterogeneous in space and time within the tree crown. The distinct expression of leaf phenotypes among crown positions could lead to complementary patterns in light interception at the crown scale. We quantified eight light-related leaf traits across 12 crown positions of ten isolated Olea europaea trees in the field. Specifically, we investigated whether the phenotypic expression of foliar traits differed among crown sectors and layers and five periods of the day from sunrise to sunset. We investigated the consequences in terms of the exposed area of the leaves at the tree scale during a single day. All traits differed among crown positions except the length-to-width ratio of the leaves. We found a strong complementarity in the patterns of the potential exposed area of the leaves among day periods as a result of a non-random distribution of leaf angles across the crown. Leaf exposure at the outer layer was below 60 % of the displayed surface, reaching maximum interception during morning periods. Daily interception increased towards the inner layer, achieving consecutive maximization from east to west positions within the crown, matching the sun's trajectory. The expression of leaf traits within isolated trees of O. europaea varies continuously through the crown in a gradient of leaf morphotypes and leaf angles depending on the exposure and location of individual leaves. The distribution of light-related traits within the crown and the complementarity in the potential exposure patterns of the leaves during the day challenges the assumption of low trait variability within individuals. © The Author 2016. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Water limitations on forest carbon cycling and conifer traits along a steep climatic gradient in the Cascade Mountains, Oregon

NASA Astrophysics Data System (ADS)

Berner, L. T.; Law, B. E.

2015-11-01

Severe droughts occurred in the western United States during recent decades, and continued human greenhouse gas emissions are expected to exacerbate warming and drying in this region. We investigated the role of water availability in shaping forest carbon cycling and morphological traits in the eastern Cascade Mountains, Oregon, focusing on the transition from low-elevation, dry western juniper (Juniperus occidentalis) woodlands to higher-elevation, wetter ponderosa pine (Pinus ponderosa) and grand fir (Abies grandis) forests. We examined 12 sites in mature forests that spanned a 1300 mm yr-1 gradient in mean growing-year climate moisture index (CMIgy ), computed annually (1964 to 2013) as monthly precipitation minus reference evapotranspiration and summed October to September. Maximum leaf area, annual aboveground productivity, and aboveground live tree biomass increased with CMIgy (r2 = 0.67-0.88, P < 0.05), approximately 50-, 30-, and 10-fold along this drier to wetter gradient. Interannual fluctuations in CMI affected the annual radial growth of 91 % of juniper, 51 % of pine, and 12 % of fir individuals from 1964 to 2013. The magnitude of the site-average growth-CMI correlations decreased with increased CMIgy (r2 = 0.53, P < 0.05). All three species, particularly fir, experienced pronounced declines in radial growth from c. 1985 to 1994, coinciding with a period of sustained below-average CMIgy and extensive insect outbreak. Traits of stress-tolerant juniper included short stature, high wood density for cavitation resistance, and high investment in water transport relative to leaf area. Species occupying wetter areas invested more resources in height growth in response to competition for light relative to investment in hydraulic architecture. Consequently, maximum tree height, leaf area : sapwood area ratio, and stem wood density were all correlated with CMIgy . The tight coupling of forest carbon cycling and species traits with water availability suggests that warmer and drier conditions projected for the 21st century could have significant biogeochemical, ecological, and social consequences in the Pacific Northwest.

Water limitations on forest carbon cycling and conifer traits along a steep climatic gradient in the Cascade Mountains, Oregon

NASA Astrophysics Data System (ADS)

Berner, L. T.; Law, B. E.

2015-09-01

Severe droughts occurred in the western United States during recent decades and continued human greenhouse gas emissions are expected to exacerbate warming and drying in this region. We investigated the role of water availability in shaping forest carbon cycling and morphological traits in the eastern Cascade Mountains, Oregon, focusing on the transition from low-elevation, dry western juniper (Juniperus occidentalis) woodlands to higher-elevation, wetter ponderosa pine (Pinus ponderosa) and grand fir (Abies grandis) forests. We examined 12 sites in mature forests that spanned a 1300 mm yr-1 gradient in mean growing-year climate moisture index (CMIgy ), computed annually (1964 to 2013) as monthly precipitation minus reference evapotranspiration and summed October to September. Maximum leaf area, annual aboveground productivity, and aboveground live tree biomass increased with CMIgy (r2 = 0.58-0.85, P < 0.05), approximately 50-, 30-, and 10-fold along this drier to wetter gradient. Interannual fluctuations in CMI affected the annual radial growth of 91 % of juniper, 51 % of pine, and 12 % of fir from 1964 to 2013. The magnitude of the site-average growth-CMI correlations decreased with increased CMIgy (r2 = 0.65, P < 0.05). All three species, particularly fir, experienced pronounced declines in radial growth from ca. 1985 to 1994, coinciding with a period of sustained below-average CMIgy and extensive insect outbreak. Traits of stress-tolerant juniper included short stature, high wood density for cavitation resistance, and high investment in water transport relative to leaf area. Species occupying wetter areas invested more resources in height growth in response to competition for light relative to investment in hydraulic architecture. Correspondingly, maximum tree height, leaf area:sapwood area ratio, and stem wood density were all correlated with CMIgy . The tight coupling of forest carbon cycling and species traits with water availability suggests that warmer and drier conditions projected for the 21st century could have significant biogeochemical, ecological, and social consequences in the Pacific Northwest.

Comparison of dwarf bamboos (Indocalamus sp.) leaf parameters to determine relationship between spatial density of plants and total leaf area per plant.

PubMed

Shi, Pei-Jian; Xu, Qiang; Sandhu, Hardev S; Gielis, Johan; Ding, Yu-Long; Li, Hua-Rong; Dong, Xiao-Bo

2015-10-01

The relationship between spatial density and size of plants is an important topic in plant ecology. The self-thinning rule suggests a -3/2 power between average biomass and density or a -1/2 power between stand yield and density. However, the self-thinning rule based on total leaf area per plant and density of plants has been neglected presumably because of the lack of a method that can accurately estimate the total leaf area per plant. We aimed to find the relationship between spatial density of plants and total leaf area per plant. We also attempted to provide a novel model for accurately describing the leaf shape of bamboos. We proposed a simplified Gielis equation with only two parameters to describe the leaf shape of bamboos one model parameter represented the overall ratio of leaf width to leaf length. Using this method, we compared some leaf parameters (leaf shape, number of leaves per plant, ratio of total leaf weight to aboveground weight per plant, and total leaf area per plant) of four bamboo species of genus Indocalamus Nakai (I. pedalis (Keng) P.C. Keng, I. pumilus Q.H. Dai and C.F. Keng, I. barbatus McClure, and I. victorialis P.C. Keng). We also explored the possible correlation between spatial density and total leaf area per plant using log-linear regression. We found that the simplified Gielis equation fit the leaf shape of four bamboo species very well. Although all these four species belonged to the same genus, there were still significant differences in leaf shape. Significant differences also existed in leaf area per plant, ratio of leaf weight to aboveground weight per plant, and leaf length. In addition, we found that the total leaf area per plant decreased with increased spatial density. Therefore, we directly demonstrated the self-thinning rule to improve light interception.

Green leaf phenology at Landsat resolution: scaling from the plot to satellite

NASA Astrophysics Data System (ADS)

Fisher, J. I.; Mustard, J. F.; Vadeboncour, M.

2005-12-01

Despite the large number of in situ, plot-level phenological measurements and satellite-derived phenological studies, there has been little success to date in merging these records temporally or spatially. In particular, while most phenological patterns and trends derived from satellites appear realistic and coherent, they may not reflect spatial and temporal patterns at the plot level. An obvious explanation is the drastic scale difference from plot-level to most satellite observations. In this research, we bridge this scale gap through higher resolution satellite records (Landsat) and quantify the accuracy of satellite-derived metrics with direct field measurements. We compiled fifty-seven Landsat scenes from southern New England (P12 R51) from 1984 to 2002. Green vegetation areal abundance for each scene was derived from spectral mixture analysis and a single set of endmembers. The leaf area signal was fit with a logistic-growth simulating sigmoid curve to derive phenological markers (half-maximum leaf-onset and offset). Spring leaf-onset dates in homogenous stands of deciduous forests displayed significant and persistent local variability. The local variability was validated with multiple springtime ground observations (r2 = 0.91). The highest degree of verified small-scale variation occurred where contiguous forests displayed leaf-onset gradients of 10-14 days over short distances (<500 m). These dramatic gradients, of a similar magnitude to differences in leaf-onset from MD to MA, occur in of low-relief (<40 m) upland regions. The patterns suggest that microclimates resulting from springtime cold-air drainage may be influential in governing the start of leaf growth. These microclimates may be of crucial importance in interpreting in situ records and interpolating phenology from satellite data. Regional patterns from the Landsat analyses suggest topographic, coastal, and land-use controls on phenology. For example, our results indicate that deciduous forests in the Providence, RI metropolitan area leaf out 5-7 days earlier than comparable rural areas. In preliminary work, we validated the Landsat-derived metrics with similar analyses of MODIS and AVHRR, and demonstrate that aggregating diverse local phenologies into coarse grids may convolute interpretations. Despite these complications, the platform-independent curve-fit methodology may be extended across platforms and field data. The methodologically consistent approach, in tandem with Landsat data, allows us to effectively scale between plot and satellite phenological observations.

Are endemics functionally distinct? Leaf traits of native and exotic woody species in a New Zealand forest.

PubMed

Heberling, J Mason; Mason, Norman W H

2018-01-01

Recent studies have concluded that native and invasive species share a common set of trait relationships. However, native species in isolated regions might be functionally constrained by their unique evolutionary histories such that they follow different carbon capture strategies than introduced species. We compared leaf traits relating to resource investment, carbon return, and resource-use efficiency in 16 native (endemic) and three non-native (invasive) species in a temperate forest in Canterbury, South Island, New Zealand. Trait differences were more closely associated with leaf habit than nativity. Deciduous species (including invaders) exhibited greater maximum photosynthetic rates at similar resource costs, which resulted in greater nitrogen- and energy-use efficiencies than evergreen natives. Leaf area was the only trait that differed significantly by nativity (over two-fold larger in invaders). Invaders and deciduous natives both occupied the 'fast return' end of the leaf economics spectrum in contrast to the native evergreens which had comparatively slow return on investment. Dominant woody invaders in this forest are physiologically distinct from many New Zealand endemic species, which are overwhelmingly evergreen. It remains unclear whether these trait differences translate to an ecological divergence in plant strategy, but these results suggest that ecophysiological tradeoffs are likely constrained by biogeography.

Changes in leaf organisation, photosynthetic performance and wood formation during ex vitro acclimatisation of black mulberry (Morus nigra L.).

PubMed

Misalová, A; Durkovic, J; Mamonová, M; Priwitzer, T; Lengyelová, A; Hladká, D; Lux, A

2009-09-01

Changes in anatomical organisation of the leaf, photosynthetic performance and wood formation were examined to evaluate the temporal and spatial patterns of acclimatisation of micropropagated slow-growing black mulberry (Morus nigra L.) plantlets to the ex vitro environment. Leaf structure differentiation, the rates of net photosynthesis (P(n)), transpiration (E) and stomatal conductance (g(s)), and secondary xylem growth were determined in the course of a 56-day acclimatisation. Differentiation of palisade parenchyma was observed 7 days after transfer. At this stage, the rates of P(n), E and g(s) reached maximum values, after which the rates of all three gas exchange parameters gradually decreased. The highest proportion of woody area occupied by vessels was also observed 7 days after transfer. An important feature of developing woody tissue is the difference in patterns of vessel distribution from the characteristic differentiation patterns of earlywood and latewood vessels in mature wood of ring-porous trees. Vessels with lumen areas over 3000 microm(2) were only differentiated in acclimatised plantlets, whereas vessels in stems sampled on days 0 and 7 had very small lumen areas of up to 560 microm(2). Full acclimatisation, observed 56 days after transfer to the ex vitro environment, was associated with the rapid growth of new in vivo formed leaves, very low rates of E and g(s), and much increased secondary xylem tissue within the stem area.

Long-Term Effects of Red- and Blue-Light Emitting Diodes on Leaf Anatomy and Photosynthetic Efficiency of Three Ornamental Pot Plants

PubMed Central

Zheng, Liang; Van Labeke, Marie-Christine

2017-01-01

Light quality critically affects plant development and growth. Development of light-emitting diodes (LEDs) enables the use of narrow band red and/or blue wavelengths as supplementary lighting in ornamental production. Yet, long periods under these wavelengths will affect leaf morphology and physiology. Leaf anatomy, stomatal traits, and stomatal conductance, leaf hydraulic conductance (Kleaf), and photosynthetic efficiency were investigated in three ornamental pot plants, namely Cordyline australis (monocot), Ficus benjamina (dicot, evergreen leaves), and Sinningia speciosa (dicot, deciduous leaves) after 8 weeks under LED light. Four light treatments were applied at 100 μmol m−2 s−1 and a photoperiod of 16 h using 100% red (R), 100% blue (B), 75% red with 25% blue (RB), and full spectrum white light (W), respectively. B and RB resulted in a greater maximum quantum yield (Fv/Fm) and quantum efficiency (ΦPSII) in all species compared to R and W and this correlated with a lower biomass under R. B increased the stomatal conductance compared with R. This increase was linked to an increasing stomatal index and/or stomatal density but the stomatal aperture area was unaffected by the applied light quality. Leaf hydraulic conductance (Kleaf) was not significantly affected by the applied light qualities. Blue light increased the leaf thickness of F. benjamina, and a relative higher increase in palisade parenchyma was observed. Also in S. speciosa, increase in palisade parenchyma was found under B and RB, though total leaf thickness was not affected. Palisade parenchyma tissue thickness was correlated to the leaf photosynthetic quantum efficiency (ΦPSII). In conclusion, the role of blue light addition in the spectrum is essential for the normal anatomical leaf development which also impacts the photosynthetic efficiency in the three studied species. PMID:28611818

Satellite retrievals of leaf chlorophyll and photosynthetic capacity for improved modeling of GPP

USDA-ARS?s Scientific Manuscript database

This study investigates the utility of in-situ and satellite-based leaf chlorophyll (Chl) estimates for quantifying leaf photosynthetic capacity and for constraining model simulations of Gross Primary Productivity (GPP) over a corn field in Maryland, U.S.A. The maximum rate of carboxylation (Vmax) r...

Morphological and phenological shoot plasticity in a Mediterranean evergreen oak facing long-term increased drought.

PubMed

Limousin, Jean-Marc; Rambal, Serge; Ourcival, Jean-Marc; Rodríguez-Calcerrada, Jesus; Pérez-Ramos, Ignacio M; Rodríguez-Cortina, Raquel; Misson, Laurent; Joffre, Richard

2012-06-01

Mediterranean trees must adjust their canopy leaf area to the unpredictable timing and severity of summer drought. The impact of increased drought on the canopy dynamics of the evergreen Quercus ilex was studied by measuring shoot growth, leaf production, litterfall, leafing phenology and leaf demography in a mature forest stand submitted to partial throughfall exclusion for 7 years. The leaf area index rapidly declined in the throughfall-exclusion plot and was 19% lower than in the control plot after 7 years of treatment. Consequently, leaf litterfall was significantly lower in the dry treatment. Such a decline in leaf area occurred through a change in branch allometry with a decreased number of ramifications produced and a reduction of the leaf area supported per unit sapwood area of the shoot (LA/SA). The leafing phenology was slightly delayed and the median leaf life span was slightly longer in the dry treatment. The canopy dynamics in both treatments were driven by water availability with a 1-year lag: leaf shedding and production were reduced following dry years; in contrast, leaf turnover was increased following wet years. The drought-induced decrease in leaf area, resulting from both plasticity in shoot development and slower leaf turnover, appeared to be a hydraulic adjustment to limit canopy transpiration and maintain leaf-specific hydraulic conductivity under drier conditions.

ERTS-1 data collection systems used to predict wheat disease severities. [Riley County, Kansas

NASA Technical Reports Server (NTRS)

Kanemasu, E. T.; Schimmelpfenning, H.; Choy, E. C.; Eversmeyer, M. G.; Lenhert, D.

1974-01-01

The author has identified the following significant results. The feasibility of using the data collection system on ERTS-1 to predict wheat leaf rust severity and resulting yield loss was tested. Ground-based data collection platforms (DCP'S), placed in two commercial wheat fields in Riley County, Kansas, transmitted to the satellite such meteorological information as maximum and minimum temperature, relative humidity, and hours of free moisture. Meteorological data received from the two DCP'S from April 23 to 29 were used to estimate the disease progress curve. Values from the curve were used to predict the percentage decrease in wheat yields resulting from leaf rust. Actual decrease in yield was obtained by applying a zinc and maneb spray (5.6 kg/ha) to control leaf rust, then comparing yields of the controlled (healthy) and the noncontrolled (rusted) areas. In each field a 9% decrease in yield was predicted by the DCP-derived data; actual decreases were 12% and 9%.

[Effects of irrigation and planting patterns on photosynthetic characteristics of flag leaf and yield at late growth stages of winter wheat].

PubMed

Dong, Hao; Bi, Jun; Xia, Guang-Li; Zhou, Xun-Bo; Chen, Yu-Hai

2014-08-01

High-yield winter wheat cultivar Jimai 22 was used to study effects of irrigation and planting patterns on water consumption characteristics and photosynthetic characteristics of winter wheat in field from 2009 to 2011. Three different planting patterns (uniform row, wide-narrow row and furrow) and four irrigation schedules (W0, no irrigation; W1, irrigation at jointing stage; W2, irrigations at jointing and anthesis stages; W3, irrigation at jointing, anthesis and milking stages. Each irrigation rate was 60 mm) were designed in the experiment. Results showed that, with the increasing of irrigation amount, flag leaf area, net photosynthesis rate, maximum photochemical efficiency and actual light transformation efficiency at late growth stages of winter wheat increased. Compared with W0 treatment, the other irrigation treatments had higher grain yields, but lower water use efficiencies. Under the same irrigation condition, the flag leaf net photosynthesis, maximum photochemical efficiency and actual light transformation efficiency were much higher in furrow pattern. Grain yields of winter wheat under furrow pattern and W2 treatment were significantly higher than that of the other treatments. Taking grain yield and WUE into consideration, furrow pattern combined with irrigation at jointing and anthesis stages might be the optimal water-saving and planting mode for the winter wheat production in North China Plain.

Wheat productivity estimates using LANDSAT data

NASA Technical Reports Server (NTRS)

Nalepka, R. F.; Colwell, J. (Principal Investigator)

1975-01-01

The author has identified the following significant results. The electro-optical leaf area meter was the most accurate of the approaches tested on harvested wheat samples, but it is very time consuming. It was decided to infer leaf area from dry weight biomass after establishing a relationship between dry weight biomass and area as measured by the leaf area meter. There is a good correlation between leaf area as measured by the meter and dry leaf biomass. There is a less consistent relationship between stem area and stem biomass.

Seasonal variations of gas exchange and water relations in deciduous and evergreen trees in monsoonal dry forests of Thailand.

PubMed

Ishida, Atsushi; Harayama, Hisanori; Yazaki, Kenichi; Ladpala, Phanumard; Sasrisang, Amornrat; Kaewpakasit, Kanokwan; Panuthai, Samreong; Staporn, Duriya; Maeda, Takahisa; Gamo, Minoru; Diloksumpun, Sapit; Puangchit, Ladawan; Ishizuka, Moriyoshi

2010-08-01

This study compared leaf gas exchange, leaf hydraulic conductance, twig hydraulic conductivity and leaf osmotic potential at full turgor between two drought-deciduous trees, Vitex peduncularis Wall. and Xylia xylocarpa (Roxb.) W. Theob., and two evergreen trees, Hopea ferrea Lanessan and Syzygium cumini (L.) Skeels, at the uppermost canopies in tropical dry forests in Thailand. The aims were to examine (i) whether leaf and twig hydraulic properties differ in relation to leaf phenology and (ii) whether xylem cavitation is a determinant of leaf shedding during the dry season. The variations in almost all hydraulic traits were more dependent on species than on leaf phenology. Evergreen Hopea exhibited the lowest leaf-area-specific twig hydraulic conductivity (leaf-area-specific K(twig)), lamina hydraulic conductance (K(lamina)) and leaf osmotic potential at full turgor (Ψ(o)) among species, whereas evergreen Syzygium exhibited the highest leaf-area-specific K(twig), K(lamina) and Ψ(o). Deciduous Xylia had the highest sapwood-area-specific K(twig), along with the lowest Huber value (sapwood area/leaf area). More negative osmotic Ψ(o) and leaf osmotic adjustment during the dry season were found in deciduous Vitex and evergreen Hopea, accompanied by low sapwood-area-specific K(twig). Regarding seasonal changes in hydraulics, no remarkable decrease in K(lamina) and K(twig) was found during the dry season in any species. Results suggest that leaf shedding during the dry season is not always associated with extensive xylem cavitation.

[Caloric value and energy allocation of Chloris virgata in northeast grassland].

PubMed

Guo, J; Wang, R; Wang, W

2001-06-01

The rules of seasonal changes in caloric values of individual plant, stem, and leaves of Chloris virgata were similar, which had two peak values from early July to early August, and then decreased gradually. Those of inflorescence assumed U shape, and had two peak values in early August and middle September, respectively. The seasonal changes in caloric values of dead standing were irregular, and the maximum value was appeared in early August. The seasonal changes in existent energy value of the aboveground parts in Chloris virgata population presented double peak curve. The two peak values were appeared in early August and early September respectively, and the maximum value was 7381.27 kJ.m-2 in early September. The energy allocation in different seasons was leaf > stem in early July, stem > leaf > dead standing in middle July, stem > leaf > inflorescence > dead standing in August, stem > inflorescence > leaf > dead standing in early September, and stem > inflorescence > dead standing > leaf in middle September. The vertical structure of energy in the aboveground parts was that the energy value gradually increased from the earth's surface to 20 cm high, and then decreased. The maximum value, which accounted for 25.75% of energy in the aboveground parts, was appeared in the layer of 10-20 cm high. In the underground parts, the energy value progressively decreased with the increase of depth, and the maximum value, which accounted for 74.21% of energy in the underground parts, was appeared in the layer of 0-10 cm depth.

Effect of solution and leaf surface polarity on droplet spread area and contact angle.

PubMed

Nairn, Justin J; Forster, W Alison; van Leeuwen, Rebecca M

2016-03-01

How much an agrochemical spray droplet spreads on a leaf surface can significantly influence efficacy. This study investigates the effect solution polarity has on droplet spreading on leaf surfaces and whether the relative leaf surface polarity, as quantified using the wetting tension dielectric (WTD) technique, influences the final spread area. Contact angles and spread areas were measured using four probe solutions on 17 species. Probe solution polarity was found to affect the measured spread area and the contact angle of the droplets on non-hairy leaves. Leaf hairs skewed the spread area measurement, preventing investigation of the influence of surface polarity on hairy leaves. WTD-measured leaf surface polarity of non-hairy leaves was found to correlate strongly with the effect of solution polarity on spread area. For non-polar leaf surfaces the spread area decreases with increasing solution polarity, for neutral surfaces polarity has no effect on spread area and for polar leaf surfaces the spread area increases with increasing solution polarity. These results attest to the use of the WTD technique as a means to quantify leaf surface polarity. © 2015 Society of Chemical Industry. © 2015 Society of Chemical Industry.

Evapotranspiration modelled from stands of three broad-leaved tropical trees in Costa Rica

NASA Astrophysics Data System (ADS)

Bigelow, Seth

2001-10-01

To examine the impact of tree species on the water cycle in a wet tropical region, annual evapotranspiration (ET) was estimated in Costa Rican plantations of three native, broad-leaved tree species that contrasted strongly in leaf size, leaf area and phenology. Evapotranspiration was estimated using the Penman-Monteith equation for transpiration from the dry canopy, the equilibrium equation for evaporation from the understory and a modified Rutter model of interception for evaporation of water from the canopy when wetted by rainfall. Canopy conductance was estimated from stomatal conductance, leaf area and leaf boundary-layer conductance; canopy storage capacity and filling rate were estimated from throughfall measurements. Micrometeorological instruments were mounted on a scaffolding tower.Mean stomatal conductance, which ranged from 0·1 to 0·7 mol m-2 s-1, was similar to boundary-layer conductance, 0·1 to 0·5 mol m-2 s-1, indicating decoupling of stomata from atmospheric conditions. Mean canopy conductance varied from 0·6 to 0·7 mol m-2 s-1 in the 1994 wet season then dropped to 0·3-0·4 mol m-2 s-1 in stands of the two deciduous species, Cordia and Cedrela, as a result of reduced leaf area during the dry season. Despite increased understory evaporation, dry-season ET from these stands was only 78-81% of ET in stands of the evergreen species, Hyeronima. Maximum canopy water depth varied from 0·2 to 2·2 mm, causing modelled interception to vary from 6% to 25% of annual ET. Higher dry-season transpiration rates along with high rates of evaporation of intercepted rainfall in all seasons led to 14% higher annual ET in Hyeronima stands (1509 mm) than in stands of the species with lowest ET,

Long-Term Effects of Red- and Blue-Light Emitting Diodes on Leaf Anatomy and Photosynthetic Efficiency of Three Ornamental Pot Plants.

PubMed

Zheng, Liang; Van Labeke, Marie-Christine

2017-01-01

Light quality critically affects plant development and growth. Development of light-emitting diodes (LEDs) enables the use of narrow band red and/or blue wavelengths as supplementary lighting in ornamental production. Yet, long periods under these wavelengths will affect leaf morphology and physiology. Leaf anatomy, stomatal traits, and stomatal conductance, leaf hydraulic conductance (K leaf ), and photosynthetic efficiency were investigated in three ornamental pot plants, namely Cordyline australis (monocot), Ficus benjamina (dicot, evergreen leaves), and Sinningia speciosa (dicot, deciduous leaves) after 8 weeks under LED light. Four light treatments were applied at 100 μmol m -2 s -1 and a photoperiod of 16 h using 100% red (R), 100% blue (B), 75% red with 25% blue (RB), and full spectrum white light (W), respectively. B and RB resulted in a greater maximum quantum yield (F v /F m ) and quantum efficiency (Φ PSII ) in all species compared to R and W and this correlated with a lower biomass under R. B increased the stomatal conductance compared with R. This increase was linked to an increasing stomatal index and/or stomatal density but the stomatal aperture area was unaffected by the applied light quality. Leaf hydraulic conductance (K leaf ) was not significantly affected by the applied light qualities. Blue light increased the leaf thickness of F. benjamina , and a relative higher increase in palisade parenchyma was observed. Also in S. speciosa , increase in palisade parenchyma was found under B and RB, though total leaf thickness was not affected. Palisade parenchyma tissue thickness was correlated to the leaf photosynthetic quantum efficiency (Φ PSII ). In conclusion, the role of blue light addition in the spectrum is essential for the normal anatomical leaf development which also impacts the photosynthetic efficiency in the three studied species.

Leaf area prediction models for Tsuga canadensis in Maine

Treesearch

Laura S. Kenefic; R.S. Seymour

1999-01-01

Tsuga canadensis (L.) Carr. (eastern hemlock) is a common species throughout the Acadian forest. Studies of leaf area and growth efficiency in this forest type have been limited by the lack of equations to predict leaf area of this species. We found that sapwood area was an effective leaf area surrogate in T. canadensis, though...

Regulation and acclimation of leaf gas exchange in a piñon-juniper woodland exposed to three different precipitation regimes.

PubMed

Limousin, Jean-Marc; Bickford, Christopher P; Dickman, Lee T; Pangle, Robert E; Hudson, Patrick J; Boutz, Amanda L; Gehres, Nathan; Osuna, Jessica L; Pockman, William T; McDowell, Nate G

2013-10-01

Leaf gas-exchange regulation plays a central role in the ability of trees to survive drought, but forecasting the future response of gas exchange to prolonged drought is hampered by our lack of knowledge regarding potential acclimation. To investigate whether leaf gas-exchange rates and sensitivity to drought acclimate to precipitation regimes, we measured the seasonal variations of leaf gas exchange in a mature piñon-juniper Pinus edulis-Juniperus monosperma woodland after 3 years of precipitation manipulation. We compared trees receiving ambient precipitation with those in an irrigated treatment (+30% of ambient precipitation) and a partial rainfall exclusion (-45%). Treatments significantly affected leaf water potential, stomatal conductance and photosynthesis for both isohydric piñon and anisohydric juniper. Leaf gas exchange acclimated to the precipitation regimes in both species. Maximum gas-exchange rates under well-watered conditions, leaf-specific hydraulic conductance and leaf water potential at zero photosynthetic assimilation all decreased with decreasing precipitation. Despite their distinct drought resistance and stomatal regulation strategies, both species experienced hydraulic limitation on leaf gas exchange when precipitation decreased, leading to an intraspecific trade-off between maximum photosynthetic assimilation and resistance of photosynthesis to drought. This response will be most detrimental to the carbon balance of piñon under predicted increases in aridity in the southwestern USA. © 2013 John Wiley & Sons Ltd.

Chemopreventive efficacy of a betel leaf extract against benzo[a]pyrene-induced forestomach tumors in mice.

PubMed

Bhide, S V; Zariwala, M B; Amonkar, A J; Azuine, M A

1991-09-01

The effect of betel leaf extract and some of its constituents, eugenol, hydroxychavicol, beta-carotene and alpha-tocopherol, on benzo[a]pyrene-induced forestomach neoplasia in male Swiss mice was examined. Betel leaf and its constituents decreased the number of papillomas per animal with the maximum protection, considering molar dosage, exhibited by beta-carotene and alpha-tocopherol. Except for beta-carotene, eugenol, hydroxychavicol and alpha-tocopherol increased the levels of reduced glutathione in the liver while glutathione S-transferase activity was enhanced by all except eugenol. Of seven sources, Banarasi betel leaves showed the maximum amounts of beta-carotene and alpha-tocopherol.

Analysis of elevation changes detected from multi-temporal LiDAR surveys in forested landslide terrain in western Oregon

USGS Publications Warehouse

Burns, W.J.; Coe, J.A.; Kaya, B.S.; Ma, Liwang

2010-01-01

We examined elevation changes detected from two successive sets of Light Detection and Ranging (LiDAR) data in the northern Coast Range of Oregon. The first set of LiDAR data was acquired during leafon conditions and the second set during leaf-off conditions. We were able to successfully identify and map active landslides using a differential digital elevation model (DEM) created from the two LiDAR data sets, but this required the use of thresholds (0.50 and 0.75 m) to remove noise from the differential elevation data, visual pattern recognition of landslideinduced elevation changes, and supplemental QuickBird satellite imagery. After mapping, we field-verified 88 percent of the landslides that we had mapped with high confidence, but we could not detect active landslides with elevation changes of less than 0.50 m. Volumetric calculations showed that a total of about 18,100 m3 of material was missing from landslide areas, probably as a result of systematic negative elevation errors in the differential DEM and as a result of removal of material by erosion and transport. We also examined the accuracies of 285 leaf-off LiDAR elevations at four landslide sites using Global Positioning System and total station surveys. A comparison of LiDAR and survey data indicated an overall root mean square error of 0.50 m, a maximum error of 2.21 m, and a systematic error of 0.09 m. LiDAR ground-point densities were lowest in areas with young conifer forests and deciduous vegetation, which resulted in extensive interpolations of elevations in the leaf-on, bare-earth DEM. For optimal use of multi-temporal LiDAR data in forested areas, we recommend that all data sets be flown during leaf-off seasons.

Exploring the limits of crop productivity: A model to evaluate progress

NASA Technical Reports Server (NTRS)

Bugbee, Bruce

1990-01-01

The goal was to determine the limits of crop productivity when all environmental constraints were removed. Researchers define productivity as food output per unit of input. Researchers evaluated cultivars of wheat with reduced leaf size and number to decrease the leaf area index at high plant densities. These cultivars may also have an improved harvest index. Hydroponic studies indicate that 1 mM nitrate in solution is adequate to support maximum growth in these systems, provided iron nutrition is adequate. Wheat does not accumulate nitrate in leaves even when the solution nitrate concentration is 15 mM. Long-term photosynthetic efficiency (g mol (exp -1) of photons) and harvest index were not altered by photoperiod (16, 20, or 24 hours). Wheat does not need, nor benefit from, a diurnal dark period.

Soil water availability and capacity of nitrogen accumulation influence variations of intrinsic water use efficiency in rice.

PubMed

Xue, Wei; Nay-Htoon, Bhone; Lindner, Steve; Dubbert, Maren; Otieno, Dennis; Ko, Jonghan; Werner, Christiane; Tenhunen, John

2016-04-01

Leaf intrinsic water use efficiency (WUEi) coupling maximum assimilation rate (Amax) and transpirable water lost via stomatal conductance (gsc) has been gaining increasing concern in sustainable crop production. Factors that influence leaf Amax and WUEi in rice (Oryza sativa L. cv Unkang) at flooding and rainfed conditions were evaluated. Positive correlations for leaf nitrogen content (Nm) and maximum carboxylation rate (Vcmax), for nitrogen allocation in Rubisco enzymes and mesophyll conductance (gm) were evident independent of cropping cultures. Rainfed rice exhibited enriched canopy leaf average Nm resulting in higher Amax, partially supporting improved leaf WUEi. Maximum WUEi (up to 0.14 μmol mmol(-1)) recorded in rainfed rice under drought conditions resulted from increasing gm/gsc ratio while at cost of significant decline in Amax due to hydraulically constrained gsc. Amax sensitivity related to gsc which was regulated by plant hydraulic conductance. WUEi was tightly correlated to Vcmax/gsc and gm/gsc ratios across the paddy and rainfed not to light environment, morphological and physiological traits, highlighting enhance capacity of Nm accumulation in rainfed rice with gsc at moderately high level similar to paddy rice facilitate optimization in Amax and WUEi while, is challenged by drought-vulnerable plant hydraulic conductance. Copyright © 2016 Elsevier GmbH. All rights reserved.

[Effects of eutrophic nitrogen nutrition on carbon balance capacity of Liquidambar formosana seedlings under low light].

PubMed

Wang, Chuan-Hua; Li, Jun-Qing; Yang, Ying

2011-12-01

To investigate the effects of atmospheric nitrogen deposition on the seedlings regeneration of Liquidambar formosana, a greenhouse experiment was conducted, in which, the low light- and nitrogen supplies were controlled similar to those in typical L. formosana secondary forests, with the effects of different light- and nitrogen supply on the L. formosana seedlings survival, leaf functional traits, biomass allocation, and gas exchange studied. The whole plant light compensation point (LCP(whoIe-plant)) of the seedlings was estimated with a whole plant carbon balance model, and then compared with the understory photosynthetic active radiance (PAR) of the typical secondary forests. Under 3.0% and 6.0% of full sunlight, eutrophic nitrogen supply led to a decrease of seedlings survival (shade tolerance) and specific leaf area (SLA), but had no obvious effects on the seedlings biomass allocation. At eutrophic nitrogen supply, light intensity had significant effects on the leaf area based maximum assimilation rate, whereas increasing nitrogen supply under low light induced the increase of leaf mass based dark respiration rate. Both light intensity and nitrogen supply had significant effects on the mass based leaf respiration rate, and the interaction of light and nitrogen had significant effects on the mass based stem respiration rate. Increasing nitrogen supply increased the LCP(wholeplant), under 3.0%, 6.0%, and 12.0% of full sunlight, but decreased the LCP(whoIe-plant) under 25.0% of full sunlight. The decrease of the seedlings shade tolerance induced by the increasing nitrogen supply under low light was correlated with the variations of the seedlings carbon balance capacity. Under the background of elevated atmospheric nitrogen deposition, the maintenance of L. formosana populations in China would more depend on disturbances and gap regeneration, and the population dynamics would be deeply affected.

[Effects of tillage at pre-planting of winter wheat and summer maize on leaf senescence of summer maize].

PubMed

Li, Xia; Zhang, Ji-wang; Ren, Bai-zhao; Fan, Xia; Dong, Shu-ting; Liu, Peng; Zhao, Bin

2015-05-01

This study explored the effects of different tillage treatments at pre-planting winter wheat and summer maize on leaf senescence physiological characteristics of summer maize in double cropping system. Zhengdan 958 was used as experimental material. Three tillage treatments, including rotary tillage before winter wheat seeding and no-tillage before summer maize seeding (RN), mold- board plow before winter wheat seeding and no-tillage before summer maize seeding (MN), and moldboard plow before winter wheat seeding and rotary tillage before summer maize seeding (MR), were designed to determine the effects of different tillage treatments on leaf area (LA) , leaf area reduction, photosynthetic pigments content, superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) activities and malondialdehyde (MDA) content in ear leaves of summer maize after tasselling (VT). LA of MN and MR were higher than that of RN from VT to 40 days after tasseling (VT + 40) and LA reduction of MR was the highest after VT + 40. As for MR, MN and NT, the photosynthetic pigments content got the maximum value at 20 days after tasselling (VT + 20) and then decreased, following the change of unimodal curve. At VT + 20, the contents of chlorophyll a in MR and MN were increased by 11.4% and 9.7%, the contents of chlorophyll b in MR and MN were increased by 14.9% and 15.9%, compared with RN. The soluble protein content in ear leaves decreased following the growth process in all treatments, and that of MR and MN remained 11.5% and 24.4% higher than that of RN from VT to VT + 40. SOD, CAT and POD activities of three treatments got the maximum values at VT + 20 and then decreased, following the change of unimodal curve. MDA content increased following the growth process in all treatments and that of RN always remained at high levels. Grain yields of MN and MR were 24.0% and 30.6% greater than that of RN, respectively. Grain yield of MR was 5.2% higher than that of MN. In conclusion, the ability of leaf senescence resistance of MN was improved, which was helpful to increase the yield of summer maize.

Different mechanisms drive the performance of native and invasive woody species in response to leaf phosphorus supply during periods of drought stress and recovery.

PubMed

Oliveira, Marciel Teixeira; Medeiros, Camila Dias; Frosi, Gabriella; Santos, Mauro Guida

2014-09-01

The effects of drought stress and leaf phosphorus (Pi) supply on photosynthetic metabolism in woody tropical species are not known, and given the recent global environmental change models that forecast lower precipitation rates and periods of prolonged drought in tropical areas, this type of study is increasingly important. The effects of controlled drought stress and Pi supply on potted young plants of two woody species, Anadenanthera colubrina (native) and Prosopis juliflora (invasive), were determined by analyzing leaf photosynthetic metabolism, biochemical properties and water potential. In the maximum stress, both species showed higher leaf water potential (Ψl) in the treatment drought +Pi when compared with the respective control -Pi. The native species showed higher gas exchange under drought +Pi than under drought -Pi conditions, while the invasive species showed the same values between drought +Pi and -Pi. Drought affected the photochemical part of photosynthetic machinery more in the invasive species than in the native species. The invasive species showed higher leaf amino acid content and a lower leaf total protein content in both Pi treatments with drought. The two species showed different responses to the leaf Pi supply under water stress for several variables measured. In addition, the strong resilience of leaf gas exchange in the invasive species compared to the native species during the recovery period may be the result of higher efficiency of Pi use. The implications of this behavior for the success of this invasive species in semiarid environments are discussed. Copyright © 2014 Elsevier Masson SAS. All rights reserved.

Relationships of leaf dark respiration to leaf nitrogen, specific leaf area and leaf life-span: a test across biomes and functional groups

Treesearch

Peter B. Reich; Michael B. Walters; David S. Ellsworth; [and others; [Editor’s note: James M.. Vose is the SRS co-author for this publication.

1998-01-01

Based on prior evidence of coordinated multiple leaf trait scaling, the authors hypothesized that variation among species in leaf dark respiration rate (Rd) should scale with variation in traits such as leaf nitrogen (N), leaf life-span, specific leaf area (SLA), and net photosynthetic capacity (Amax). However, it is not known whether such scaling, if it exists, is...

Global scale environmental control of plant photosynthetic capacity

DOE PAGES

Ali, Ashehad; Xu, Chonggang; Rogers, Alistair; ...

2015-12-01

Photosynthetic capacity, determined by light harvesting and carboxylation reactions, is a key plant trait that determines the rate of photosynthesis; however, in Earth System Models (ESMs) at a reference temperature, it is either a fixed value for a given plant functional type or derived from a linear function of leaf nitrogen content. In this study, we conducted a comprehensive analysis that considered correlations of environmental factors with photosynthetic capacity as determined by maximum carboxylation (V c,m) rate scaled to 25°C (i.e., V c,25; μmol CO 2·m –2·s –1) and maximum electron transport rate (Jmax) scaled to 25°C (i.e., J 25;more » μmol electron·m –2·s –1) at the global scale. Our results showed that the percentage of variation in observed Vc,25 and J25 explained jointly by the environmental factors (i.e., day length, radiation, temperature, and humidity) were 2–2.5 times and 6–9 times of that explained by area-based leaf nitrogen content, respectively. Environmental factors influenced photosynthetic capacity mainly through photosynthetic nitrogen use efficiency, rather than through leaf nitrogen content. The combination of leaf nitrogen content and environmental factors was able to explain ~56% and ~66% of the variation in V c,25 and J 25 at the global scale, respectively. As a result, our analyses suggest that model projections of plant photosynthetic capacity and hence land–atmosphere exchange under changing climatic conditions could be substantially improved if environmental factors are incorporated into algorithms used to parameterize photosynthetic capacity in ESMs.« less

Are trait-scaling relationships invariant across contrasting elevations in the widely distributed treeline species Nothofagus pumilio?

PubMed

Fajardo, Alex

2016-05-01

The study of scaling examines the relative dimensions of diverse organismal traits. Understanding whether global scaling patterns are paralleled within species is key to identify causal factors of universal scaling. I examined whether the foliage-stem (Corner's rules), the leaf size-number, and the leaf mass-leaf area scaling relationships remained invariant and isometric with elevation in a wide-distributed treeline species in the southern Chilean Andes. Mean leaf area, leaf mass, leafing intensity, and twig cross-sectional area were determined for 1-2 twigs of 8-15 Nothofagus pumilio individuals across four elevations (including treeline elevation) and four locations (from central Chile at 36°S to Tierra del Fuego at 54°S). Mixed effects models were fitted to test whether the interaction term between traits and elevation was nonsignificant (invariant). The leaf-twig cross-sectional area and the leaf mass-leaf area scaling relationships were isometric (slope = 1) and remained invariant with elevation, whereas the leaf size-number (i.e., leafing intensity) scaling was allometric (slope ≠ -1) and showed no variation with elevation. Leaf area and leaf number were consistently negatively correlated across elevation. The scaling relationships examined in the current study parallel those seen across species. It is plausible that the explanation of intraspecific scaling relationships, as trait combinations favored by natural selection, is the same as those invoked to explain across species patterns. Thus, it is very likely that the global interspecific Corner's rules and other leaf-leaf scaling relationships emerge as the aggregate of largely parallel intraspecific patterns. © 2016 Botanical Society of America.

Estimated winter wheat yield from crop growth predicted by LANDSAT

NASA Technical Reports Server (NTRS)

Kanemasu, E. T.

1977-01-01

An evapotranspiration and growth model for winter wheat is reported. The inputs are daily solar radiation, maximum temperature, minimum temperature, precipitation/irrigation and leaf area index. The meteorological data were obtained from National Weather Service while LAI was obtained from LANDSAT multispectral scanner. The output provides daily estimates of potential evapotranspiration, transpiration, evaporation, soil moisture (50 cm depth), percentage depletion, net photosynthesis and dry matter production. Winter wheat yields are correlated with transpiration and dry matter accumulation.

Trait Acclimation Mitigates Mortality Risks of Tropical Canopy Trees under Global Warming.

PubMed

Sterck, Frank; Anten, Niels P R; Schieving, Feike; Zuidema, Pieter A

2016-01-01

There is a heated debate about the effect of global change on tropical forests. Many scientists predict large-scale tree mortality while others point to mitigating roles of CO2 fertilization and - the notoriously unknown - physiological trait acclimation of trees. In this opinion article we provided a first quantification of the potential of trait acclimation to mitigate the negative effects of warming on tropical canopy tree growth and survival. We applied a physiological tree growth model that incorporates trait acclimation through an optimization approach. Our model estimated the maximum effect of acclimation when trees optimize traits that are strongly plastic on a week to annual time scale (leaf photosynthetic capacity, total leaf area, stem sapwood area) to maximize carbon gain. We simulated tree carbon gain for temperatures (25-35°C) and ambient CO2 concentrations (390-800 ppm) predicted for the 21st century. Full trait acclimation increased simulated carbon gain by up to 10-20% and the maximum tolerated temperature by up to 2°C, thus reducing risks of tree death under predicted warming. Functional trait acclimation may thus increase the resilience of tropical trees to warming, but cannot prevent tree death during extremely hot and dry years at current CO2 levels. We call for incorporating trait acclimation in field and experimental studies of plant functional traits, and in models that predict responses of tropical forests to climate change.

Coupled hydraulic and photosynthetic feedbacks on forest transpiration throughout the growing season

NASA Astrophysics Data System (ADS)

Mackay, D. S.; Ewers, B. E.

2007-12-01

Ecosystem models account for vegetative controls on water fluxes using environmental drivers and hydraulic and/or biochemical limits on canopy stomatal conductance (Gs), variations in space and time of leaf area index (L), and species or biome specific parameters. However, some parameters, such as maximum stomatal conductance or its reference proxy at vapor pressure deficit of 1 kPa (Gsref), may not be strictly time-independent suggesting as yet undefined mechanisms in the models. We developed a model of coupled canopy water and carbon exchange, which allowed us to examine photosynthetic and hydraulic feedbacks on Gsref spanning the whole growing season for several dominant tree species in wetland and upland positions that collectively account for most a 1600 square km region centered on the WLEF AmeriFlux tower in Wisconsin, USA. The model assimilated half-hourly sap flux and micrometeorological data to quantify and explain temporal variations in Gsref for trembling aspen, sugar maple, and red pine in upland sites, and speckled alder and white cedar in wetland sites. Results show (1) phenological effects on photosynthetic activity with feedback on Gsref in all species, and (2) lags of up to two months between maximum per unit leaf area photosynthetic rates for conifer versus deciduous species. These results show that for given environmental conditions canopy transpiration depends on both L and timing of biochemical activation, both of which have implications for regional ecosystem water cycling.

Using the conservative nature of fresh leaf surface density to measure foliar area

NASA Astrophysics Data System (ADS)

Castillo, Omar S.; Zaragoza, Esther M.; Alvarado, Carlos J.; Barrera, Maria G.; Dasgupta-Schubert, Nabanita

2014-10-01

For a herbaceous species, the inverse of the fresh leaf surface density, the Hughes constant, is nearly conserved. We apply the Hughes constant to develop an absolute method of leafarea measurement that requires no regression fits, prior calibrations or oven-drying. The Hughes constant was determined in situ using a known geometry and weights of a sub-set obtained from the fresh leaves whose areas are desired. Subsequently, the leaf-areas (at any desired stratification level), were derived by utilizing the Hughes constant and the masses of the fresh leaves. The proof of concept was established for leaf-discs of the plants Mandevilla splendens and Spathiphyllum wallisii. The conservativeness of the Hughes constant over individual leaf-zones and different leaftypes from the leaves of each species was quantitatively validated. Using the globally averaged Hughes constant for each species, the leaf-area of these and additional co-species plants, were obtained. The leaf-area-measurement-by-mass was cross-checked with standard digital image analysis. There were no statistically significant differences between the leaf-area-measurement-by-mass and the digital image analysis measured leaf-areas and the linear correlation between the two methods was very good. Leaf-areameasurement- by-mass was found to be rapid and simple with accuracies comparable to the digital image analysis method. The greatly reduced cost of leaf-area-measurement-by-mass could be beneficial for small agri-businesses in developing countries.

The relationship between leaf area growth and biomass accumulation in Arabidopsis thaliana

PubMed Central

Weraduwage, Sarathi M.; Chen, Jin; Anozie, Fransisca C.; Morales, Alejandro; Weise, Sean E.; Sharkey, Thomas D.

2015-01-01

Leaf area growth determines the light interception capacity of a crop and is often used as a surrogate for plant growth in high-throughput phenotyping systems. The relationship between leaf area growth and growth in terms of mass will depend on how carbon is partitioned among new leaf area, leaf mass, root mass, reproduction, and respiration. A model of leaf area growth in terms of photosynthetic rate and carbon partitioning to different plant organs was developed and tested with Arabidopsis thaliana L. Heynh. ecotype Columbia (Col-0) and a mutant line, gigantea-2 (gi-2), which develops very large rosettes. Data obtained from growth analysis and gas exchange measurements was used to train a genetic programming algorithm to parameterize and test the above model. The relationship between leaf area and plant biomass was found to be non-linear and variable depending on carbon partitioning. The model output was sensitive to the rate of photosynthesis but more sensitive to the amount of carbon partitioned to growing thicker leaves. The large rosette size of gi-2 relative to that of Col-0 resulted from relatively small differences in partitioning to new leaf area vs. leaf thickness. PMID:25914696

The relationship between leaf area growth and biomass accumulation in Arabidopsis thaliana

DOE PAGES

Weraduwage, Sarathi M.; Chen, Jin; Anozie, Fransisca C.; ...

2015-04-09

Leaf area growth determines the light interception capacity of a crop and is often used as a surrogate for plant growth in high-throughput phenotyping systems. The relationship between leaf area growth and growth in terms of mass will depend on how carbon is partitioned among new leaf area, leaf mass, root mass, reproduction, and respiration. A model of leaf area growth in terms of photosynthetic rate and carbon partitioning to different plant organs was developed and tested with Arabidopsis thaliana L. Heynh. ecotype Columbia (Col-0) and a mutant line, gigantea-2 (gi-2), which develops very large rosettes. Data obtained from growthmore » analysis and gas exchange measurements was used to train a genetic programming algorithm to parameterize and test the above model. The relationship between leaf area and plant biomass was found to be non-linear and variable depending on carbon partitioning. The model output was sensitive to the rate of photosynthesis but more sensitive to the amount of carbon partitioned to growing thicker leaves. The large rosette size of gi-2 relative to that of Col-0 resulted from relatively small differences in partitioning to new leaf area vs. leaf thickness.« less

Ratio of Cut Surface Area to Leaf Sample Volume for Water Potential Measurements by Thermocouple Psychrometers

PubMed Central

Walker, Sue; Oosterhuis, Derrick M.; Wiebe, Herman H.

1984-01-01

Evaporative losses from the cut edge of leaf samples are of considerable importance in measurements of leaf water potential using thermocouple psychrometers. The ratio of cut surface area to leaf sample volume (area to volume ratio) has been used to give an estimate of possible effects of evaporative loss in relation to sample size. A wide range of sample sizes with different area to volume ratios has been used. Our results using Glycine max L. Merr. cv Bragg indicate that leaf samples with area to volume values less than 0.2 square millimeter per cubic millimeter give psychrometric leaf water potential measurements that compare favorably with pressure chamber measurements. PMID:16663578

Dynamic tumor tracking using the Elekta Agility MLC

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fast, Martin F., E-mail: martin.fast@icr.ac.uk; Nill, Simeon, E-mail: simeon.nill@icr.ac.uk; Bedford, James L.

2014-11-01

Purpose: To evaluate the performance of the Elekta Agility multileaf collimator (MLC) for dynamic real-time tumor tracking. Methods: The authors have developed a new control software which interfaces to the Agility MLC to dynamically program the movement of individual leaves, the dynamic leaf guides (DLGs), and the Y collimators (“jaws”) based on the actual target trajectory. A motion platform was used to perform dynamic tracking experiments with sinusoidal trajectories. The actual target positions reported by the motion platform at 20, 30, or 40 Hz were used as shift vectors for the MLC in beams-eye-view. The system latency of the MLCmore » (i.e., the average latency comprising target device reporting latencies and MLC adjustment latency) and the geometric tracking accuracy were extracted from a sequence of MV portal images acquired during irradiation for the following treatment scenarios: leaf-only motion, jaw + leaf motion, and DLG + leaf motion. Results: The portal imager measurements indicated a clear dependence of the system latency on the target position reporting frequency. Deducting the effect of the target frequency, the leaf adjustment latency was measured to be 38 ± 3 ms for a maximum target speed v of 13 mm/s. The jaw + leaf adjustment latency was 53 ± 3 at a similar speed. The system latency at a target position frequency of 30 Hz was in the range of 56–61 ms for the leaves (v ≤ 31 mm/s), 71–78 ms for the jaw + leaf motion (v ≤ 25 mm/s), and 58–72 ms for the DLG + leaf motion (v ≤ 59 mm/s). The tracking accuracy showed a similar dependency on the target position frequency and the maximum target speed. For the leaves, the root-mean-squared error (RMSE) was between 0.6–1.5 mm depending on the maximum target speed. For the jaw + leaf (DLG + leaf) motion, the RMSE was between 0.7–1.5 mm (1.9–3.4 mm). Conclusions: The authors have measured the latency and geometric accuracy of the Agility MLC, facilitating its future use for clinical tracking applications.« less

Leaf mass per area, not total leaf area, drives differences in above-ground biomass distribution among woody plant functional types.

PubMed

Duursma, Remko A; Falster, Daniel S

2016-10-01

Here, we aim to understand differences in biomass distribution between major woody plant functional types (PFTs) (deciduous vs evergreen and gymnosperm vs angiosperm) in terms of underlying traits, in particular the leaf mass per area (LMA) and leaf area per unit stem basal area. We used a large compilation of plant biomass and size observations, including observations of 21 084 individuals on 656 species. We used a combination of semiparametric methods and variance partitioning to test the influence of PFT, plant height, LMA, total leaf area, stem basal area and climate on above-ground biomass distribution. The ratio of leaf mass to above-ground woody mass (MF /MS ) varied strongly among PFTs. We found that MF /MS at a given plant height was proportional to LMA across PFTs. As a result, the PFTs did not differ in the amount of leaf area supported per unit above-ground biomass or per unit stem basal area. Climate consistently explained very little additional variation in biomass distribution at a given plant size. Combined, these results demonstrate consistent patterns in above-ground biomass distribution and leaf area relationships among major woody PFTs, which can be used to further constrain global vegetation models. © 2016 The Authors. New Phytologist © 2016 New Phytologist Trust.

Greater deciduous shrub abundance extends tundra peak season and increases modeled net CO2 uptake.

PubMed

Sweet, Shannan K; Griffin, Kevin L; Steltzer, Heidi; Gough, Laura; Boelman, Natalie T

2015-06-01

Satellite studies of the terrestrial Arctic report increased summer greening and longer overall growing and peak seasons since the 1980s, which increases productivity and the period of carbon uptake. These trends are attributed to increasing air temperatures and reduced snow cover duration in spring and fall. Concurrently, deciduous shrubs are becoming increasingly abundant in tundra landscapes, which may also impact canopy phenology and productivity. Our aim was to determine the influence of greater deciduous shrub abundance on tundra canopy phenology and subsequent impacts on net ecosystem carbon exchange (NEE) during the growing and peak seasons in the arctic foothills region of Alaska. We compared deciduous shrub-dominated and evergreen/graminoid-dominated community-level canopy phenology throughout the growing season using the normalized difference vegetation index (NDVI). We used a tundra plant-community-specific leaf area index (LAI) model to estimate LAI throughout the green season and a tundra-specific NEE model to estimate the impact of greater deciduous shrub abundance and associated shifts in both leaf area and canopy phenology on tundra carbon flux. We found that deciduous shrub canopies reached the onset of peak greenness 13 days earlier and the onset of senescence 3 days earlier compared to evergreen/graminoid canopies, resulting in a 10-day extension of the peak season. The combined effect of the longer peak season and greater leaf area of deciduous shrub canopies almost tripled the modeled net carbon uptake of deciduous shrub communities compared to evergreen/graminoid communities, while the longer peak season alone resulted in 84% greater carbon uptake in deciduous shrub communities. These results suggest that greater deciduous shrub abundance increases carbon uptake not only due to greater leaf area, but also due to an extension of the period of peak greenness, which extends the period of maximum carbon uptake. © 2015 John Wiley & Sons Ltd.

Convergent Evolution towards High Net Carbon Gain Efficiency Contributes to the Shade Tolerance of Palms (Arecaceae).

PubMed

Ma, Ren-Yi; Zhang, Jiao-Lin; Cavaleri, Molly A; Sterck, Frank; Strijk, Joeri S; Cao, Kun-Fang

2015-01-01

Most palm species occur in the shaded lower strata of tropical rain forests, but how their traits relate to shade adaptation is poorly understood. We hypothesized that palms are adapted to the shade of their native habitats by convergent evolution towards high net carbon gain efficiency (CGEn), which is given by the maximum photosynthetic rate to dark respiration rate ratio. Leaf mass per area, maximum photosynthetic rate, dark respiration and N and P concentrations were measured in 80 palm species grown in a common garden, and combined with data of 30 palm species growing in their native habitats. Compared to other species from the global leaf economics data, dicotyledonous broad-leaved trees in tropical rainforest or other monocots in the global leaf economics data, palms possessed consistently higher CGEn, achieved by lowered dark respiration and fairly high foliar P concentration. Combined phylogenetic analyses of evolutionary signal and trait evolution revealed convergent evolution towards high CGEn in palms. We conclude that high CGEn is an evolutionary strategy that enables palms to better adapt to shady environments than coexisting dicot tree species, and may convey advantages in competing with them in the tropical forest understory. These findings provide important insights for understanding the evolution and ecology of palms, and for understanding plant shade adaptations of lower rainforest strata. Moreover, given the dominant role of palms in tropical forests, these findings are important for modelling carbon and nutrient cycling in tropical forest ecosystems.

Seasonal Changes in Leaf Area of Amazon Forests from Leaf Flushing and Abscission

NASA Astrophysics Data System (ADS)

Samanta, A.; Knyazikhin, Y.; Xu, L.; Dickinson, R.; Fu, R.; Costa, M. H.; Ganguly, S.; Saatchi, S. S.; Nemani, R. R.; Myneni, R.

2011-12-01

A large increase in near-infrared (NIR) reflectance of Amazon forests during the light-rich dry season and a corresponding decrease during the light-poor wet season has been observed in satellite measurements. This has been variously interpreted as seasonal changes in leaf area resulting from net leaf flushing in the dry season and net leaf abscission in the wet season, enhanced photosynthetic activity during the dry season from flushing new leaves and as change in leaf scattering and absorption properties between younger and older leaves covered with epiphylls. Reconciling these divergent views using theory and observations is the goal of this article. The observed changes in NIR reflectance of Amazon forests could be due to similar, but small, changes in NIR leaf albedo (reflectance plus transmittance) only, from exchanging older leaves with newer ones, with total leaf area unchanged. However, this argument ignores accumulating evidence from ground-based studies of higher leaf area in the dry season relative to the wet season, seasonal changes in litterfall and does not satisfactorily explain why NIR reflectance of these forests decreases in the wet season. A more convincing explanation for the observed increase in NIR reflectance during the dry season and decrease during the wet season is one that invokes changes in both leaf area and leaf optical properties. Such an argument is consistent with known phonological behavior of tropical forests, ground-based reports of seasonal changes in leaf area, litterfall, leaf optical properties and fluxes of evapotranspiration, and thus, reconciles the various seemingly divergent views.

Seasonal changes in leaf area of Amazon forests from leaf flushing and abscission

NASA Astrophysics Data System (ADS)

Samanta, Arindam; Knyazikhin, Yuri; Xu, Liang; Dickinson, Robert E.; Fu, Rong; Costa, Marcos H.; Saatchi, Sassan S.; Nemani, Ramakrishna R.; Myneni, Ranga B.

2012-03-01

A large increase in near-infrared (NIR) reflectance of Amazon forests during the light-rich dry season and a corresponding decrease during the light-poor wet season has been observed in satellite measurements. This increase has been variously interpreted as seasonal change in leaf area resulting from net leaf flushing in the dry season or net leaf abscission in the wet season, enhanced photosynthetic activity during the dry season from flushing new leaves and as change in leaf scattering and absorption properties between younger and older leaves covered with epiphylls. Reconciling these divergent views using theory and observations is the goal of this article. The observed changes in NIR reflectance of Amazon forests could be due to similar, but small, changes in NIR leaf albedo (reflectance plus transmittance) resulting from the exchange of older leaves for newer ones, but with the total leaf area unchanged. However, this argument ignores accumulating evidence from ground-based reports of higher leaf area in the dry season than the wet season, seasonal changes in litterfall and does not satisfactorily explain why NIR reflectance of these forests decreases in the wet season. More plausibly, the increase in NIR reflectance during the dry season and the decrease during the wet season would result from changes in both leaf area and leaf optical properties. Such change would be consistent with known phenological behavior of tropical forests, ground-based reports of seasonal changes in leaf area, litterfall, leaf optical properties and fluxes of evapotranspiration, and thus, would reconcile the various seemingly divergent views.

Canopy-scale relationships between foliar nitrogen and albedo are not observed in leaf reflectance and transmittance within temperate deciduous tree species

Treesearch

Megan K. Bartlett; Scott V. Ollinger; David Y. Hollinger; Haley F. Wicklein; Andrew D. Richardson

2011-01-01

Strong positive correlations between the maximum rate of canopy photosynthesis, canopy-averaged foliar nitrogen concentration, and canopy albedo have been shown in previous studies. While leaf-level relationships between photosynthetic capacity and foliar nitrogen are well documented, it is not clear whether leaf-level relationships between solar-weighted reflectance...

Comparison of direct and indirect methods for assessing leaf area index across a tropical rain forest landscape

Treesearch

Paulo C. Olivas; Steven F. Oberbauer; David B. Clark; Deborah A. Clark; Michael G. Ryan; Joseph J. O' Brien; Harlyn Ordonez

2013-01-01

Many functional properties of forests depend on the leaf area; however, measuring leaf area is not trivial in tall evergreen vegetation. As a result, leaf area is generally estimated indirectly by light absorption methods. These indirect methods are widely used, but have never been calibrated against direct measurements in tropical rain forests, either at point or...

Leaf area compounds height-related hydraulic costs of water transport in Oregon White Oak trees.

Treesearch

N. Phillips; B. J. Bond; N. G. McDowell; Michael G. Ryan; A. Schauer

2003-01-01

The ratio of leaf to sapwood area generally decreases with tree size, presumably to moderate hydraulic costs of tree height. This study assessed consequences of tree size and leaf area on water flux in Quercus garryana Dougl. ex. Hook (Oregon White Oak), a species in which leaf to sapwood area ratio increases with tree size. We tested hypotheses that...

Broad Anatomical Variation within a Narrow Wood Density Range--A Study of Twig Wood across 69 Australian Angiosperms.

PubMed

Ziemińska, Kasia; Westoby, Mark; Wright, Ian J

2015-01-01

Just as people with the same weight can have different body builds, woods with the same wood density can have different anatomies. Here, our aim was to assess the magnitude of anatomical variation within a restricted range of wood density and explore its potential ecological implications. Twig wood of 69 angiosperm tree and shrub species was analyzed. Species were selected so that wood density varied within a relatively narrow range (0.38-0.62 g cm-3). Anatomical traits quantified included wood tissue fractions (fibres, axial parenchyma, ray parenchyma, vessels, and conduits with maximum lumen diameter below 15 μm), vessel properties, and pith area. To search for potential ecological correlates of anatomical variation the species were sampled across rainfall and temperature contrasts, and several other ecologically-relevant traits were measured (plant height, leaf area to sapwood area ratio, and modulus of elasticity). Despite the limited range in wood density, substantial anatomical variation was observed. Total parenchyma fraction varied from 0.12 to 0.66 and fibre fraction from 0.20 to 0.74, and these two traits were strongly inversely correlated (r = -0.86, P < 0.001). Parenchyma was weakly (0.24 ≤|r|≤ 0.35, P < 0.05) or not associated with vessel properties nor with height, leaf area to sapwood area ratio, and modulus of elasticity (0.24 ≤|r|≤ 0.41, P < 0.05). However, vessel traits were fairly well correlated with height and leaf area to sapwood area ratio (0.47 ≤|r|≤ 0.65, all P < 0.001). Modulus of elasticity was mainly driven by fibre wall plus vessel wall fraction rather than by the parenchyma component. Overall, there seem to be at least three axes of variation in xylem, substantially independent of each other: a wood density spectrum, a fibre-parenchyma spectrum, and a vessel area spectrum. The fibre-parenchyma spectrum does not yet have any clear or convincing ecological interpretation.

Joint Leaf chlorophyll and leaf area index retrieval from Landsat data using a regularized model inversion system

USDA-ARS?s Scientific Manuscript database

Leaf area index (LAI) and leaf chlorophyll (Chl) content represent key biophysical and biochemical controls on water, energy and carbon exchange processes in the terrestrial biosphere. In combination, LAI and leaf Chl content provide critical information on vegetation density, vitality and photosynt...

Effects of fully open-air [CO2] elevation on leaf photosynthesis and ultrastructure of Isatis indigotica fort.

PubMed

Hao, Xingyu; Li, Ping; Feng, Yongxiang; Han, Xue; Gao, Ji; Lin, Erda; Han, Yuanhuai

2013-01-01

Traditional Chinese medicine relies heavily on herbs, yet there is no information on how these herb plants would respond to climate change. In order to gain insight into such response, we studied the effect of elevated [CO2] on Isatis indigotica Fort, one of the most popular Chinese herb plants. The changes in leaf photosynthesis, chlorophyll fluorescence, leaf ultrastructure and biomass yield in response to elevated [CO2] (550±19 µmol mol(-1)) were determined at the Free-Air Carbon dioxide Enrichment (FACE) experimental facility in North China. Photosynthetic ability of I. indigotica was improved under elevated [CO2]. Elevated [CO2] increased net photosynthetic rate (P N), water use efficiency (WUE) and maximum rate of electron transport (J max) of upper most fully-expended leaves, but not stomatal conductance (gs), transpiration ratio (Tr) and maximum velocity of carboxylation (V c,max). Elevated [CO2] significantly increased leaf intrinsic efficiency of PSII (Fv'/Fm') and quantum yield of PSII(ΦPS II ), but decreased leaf non-photochemical quenching (NPQ), and did not affect leaf proportion of open PSII reaction centers (qP) and maximum quantum efficiency of PSII (Fv/Fm). The structural chloroplast membrane, grana layer and stroma thylakoid membranes were intact under elevated [CO2], though more starch grains were accumulated within the chloroplasts than that of under ambient [CO2]. While the yield of I. indigotica was higher due to the improved photosynthesis under elevated [CO2], the content of adenosine, one of the functional ingredients in indigowoad root was not affected.

Growth form and seasonal variation in leaf gas exchange of Colophospermum mopane savanna trees in northwest Botswana.

PubMed

Veenendaal, Elmar M; Mantlana, Khanyisa B; Pammenter, Norman W; Weber, Piet; Huntsman-Mapila, Phillipa; Lloyd, Jon

2008-03-01

We investigated differences in physiological and morphological traits between the tall and short forms of mopane (Colophospermum mopane (Kirk ex Benth.) Kirk ex J. Léonard) trees growing near Maun, Botswana on a Kalahari sandveld overlying an impermeable calcrete duricrust. We sought to determine if differences between the two physiognomic types are attributable to the way they exploit available soil water. The tall form, which was located on deeper soil than the short form (5.5 versus 1.6 m), had a lower leaf:fine root biomass ratio (1:20 versus 1:6), but a similar leaf area index (0.9-1.0). Leaf nitrogen concentrations varied between 18 and 27 mg g(-1) and were about 20% higher in the tall form than in the short form. Maximum net assimilation rates (A sat) occurred during the rainy seasons (March-April 2000 and January-February 2001) and were similar in the tall and short forms (15-22 micromol m(-2) s(-1)) before declining to less than 10 micromol m(-2) s(-1) at the end of the rainy season in late April. As the dry season progressed, A sat, soil water content, predawn leaf water potential (Psi pd) and leaf nitrogen concentration declined rapidly. Before leaf abscission, Psi pd was more negative in the short form (-3.4 MPa) than in the tall form (-2.7 MPa) despite the greater availability of soil water beneath the short form trees. This difference appeared attributable to differences in root depth and density between the physiognomic types. Stomatal regulation of water use and carbon assimilation differed between years, with the tall form having a consistently more conservative water-use strategy as the dry season progressed than the short form.

Variation in crown light utilization characteristics among tropical canopy trees.

PubMed

Kitajima, Kaoru; Mulkey, Stephen S; Wright, S Joseph

2005-02-01

Light extinction through crowns of canopy trees determines light availability at lower levels within forests. The goal of this paper is the exploration of foliage distribution and light extinction in crowns of five canopy tree species in relation to their shoot architecture, leaf traits (mean leaf angle, life span, photosynthetic characteristics) and successional status (from pioneers to persistent). Light extinction was examined at three hierarchical levels of foliage organization, the whole crown, the outermost canopy and the individual shoots, in a tropical moist forest with direct canopy access with a tower crane. Photon flux density and cumulative leaf area index (LAI) were measured at intervals of 0.25-1 m along multiple vertical transects through three to five mature tree crowns of each species to estimate light extinction coefficients (K). Cecropia longipes, a pioneer species with the shortest leaf life span, had crown LAI <0.5. Among the remaining four species, crown LAI ranged from 2 to 8, and species with orthotropic terminal shoots exhibited lower light extinction coefficients (0.35) than those with plagiotropic shoots (0.53-0.80). Within each type, later successional species exhibited greater maximum LAI and total light extinction. A dense layer of leaves at the outermost crown of a late successional species resulted in an average light extinction of 61% within 0.5 m from the surface. In late successional species, leaf position within individual shoots does not predict the light availability at the individual leaf surface, which may explain their slow decline of photosynthetic capacity with leaf age and weak differentiation of sun and shade leaves. Later-successional tree crowns, especially those with orthotropic branches, exhibit lower light extinction coefficients, but greater total LAI and total light extinction, which contribute to their efficient use of light and competitive dominance.

Leaf area and photosynthesis of newly emerged trifoliolate leaves are regulated by mature leaves in soybean.

PubMed

Wu, Yushan; Gong, Wanzhuo; Wang, Yangmei; Yong, Taiwen; Yang, Feng; Liu, Weigui; Wu, Xiaoling; Du, Junbo; Shu, Kai; Liu, Jiang; Liu, Chunyan; Yang, Wenyu

2018-03-29

Leaf anatomy and the stomatal development of developing leaves of plants have been shown to be regulated by the same light environment as that of mature leaves, but no report has yet been written on whether such a long-distance signal from mature leaves regulates the total leaf area of newly emerged leaves. To explore this question, we created an investigation in which we collected data on the leaf area, leaf mass per area (LMA), leaf anatomy, cell size, cell number, gas exchange and soluble sugar content of leaves from three soybean varieties grown under full sunlight (NS), shaded mature leaves (MS) or whole plants grown in shade (WS). Our results show that MS or WS cause a marked decline both in leaf area and LMA in newly developing leaves. Leaf anatomy also showed characteristics of shade leaves with decreased leaf thickness, palisade tissue thickness, sponge tissue thickness, cell size and cell numbers. In addition, in the MS and WS treatments, newly developed leaves exhibited lower net photosynthetic rate (Pn), stomatal conductance (Gs) and transpiration rate (E), but higher carbon dioxide (CO 2 ) concentration in the intercellular space (Ci) than plants grown in full sunlight. Moreover, soluble sugar content was significantly decreased in newly developed leaves in MS and WS treatments. These results clearly indicate that (1) leaf area, leaf anatomical structure, and photosynthetic function of newly developing leaves are regulated by a systemic irradiance signal from mature leaves; (2) decreased cell size and cell number are the major cause of smaller and thinner leaves in shade; and (3) sugars could possibly act as candidate signal substances to regulate leaf area systemically.

Moisture availability constraints on the leaf area to sapwood area ratio: analysis of measurements on Australian evergreen angiosperm trees

NASA Astrophysics Data System (ADS)

Togashi, Henrique; Prentice, Colin; Evans, Bradley; Forrester, David; Drake, Paul; Feikema, Paul; Brooksbank, Kim; Eamus, Derek; Taylor, Daniel

2014-05-01

The leaf area to sapwood area ratio (LA:SA) is a key plant trait that links photosynthesis to transpiration. Pipe model theory states that the sapwood cross-sectional area of a stem or branch at any point should scale isometrically with the area of leaves distal to that point. Optimization theory further suggests that LA:SA should decrease towards drier climates. Although acclimation of LA:SA to climate has been reported within species, much less is known about the scaling of this trait with climate among species. We compiled LA:SA measurements from 184 species of Australian evergreen angiosperm trees. The pipe model was broadly confirmed, based on measurements on branches and trunks of trees from one to 27 years old. We found considerable scatter in LA:SA among species. However quantile regression showed strong (0.2

Morphological and moisture availability controls of the leaf area-to-sapwood area ratio: analysis of measurements on Australian trees.

PubMed

Togashi, Henrique Furstenau; Prentice, Iain Colin; Evans, Bradley John; Forrester, David Ian; Drake, Paul; Feikema, Paul; Brooksbank, Kim; Eamus, Derek; Taylor, Daniel

2015-03-01

The leaf area-to-sapwood area ratio (LA:SA) is a key plant trait that links photosynthesis to transpiration. The pipe model theory states that the sapwood cross-sectional area of a stem or branch at any point should scale isometrically with the area of leaves distal to that point. Optimization theory further suggests that LA:SA should decrease toward drier climates. Although acclimation of LA:SA to climate has been reported within species, much less is known about the scaling of this trait with climate among species. We compiled LA:SA measurements from 184 species of Australian evergreen angiosperm trees. The pipe model was broadly confirmed, based on measurements on branches and trunks of trees from one to 27 years old. Despite considerable scatter in LA:SA among species, quantile regression showed strong (0.2 < R1 < 0.65) positive relationships between two climatic moisture indices and the lowermost (5%) and uppermost (5-15%) quantiles of log LA:SA, suggesting that moisture availability constrains the envelope of minimum and maximum values of LA:SA typical for any given climate. Interspecific differences in plant hydraulic conductivity are probably responsible for the large scatter of values in the mid-quantile range and may be an important determinant of tree morphology.

Morphological and moisture availability controls of the leaf area-to-sapwood area ratio: analysis of measurements on Australian trees

PubMed Central

Togashi, Henrique Furstenau; Prentice, Iain Colin; Evans, Bradley John; Forrester, David Ian; Drake, Paul; Feikema, Paul; Brooksbank, Kim; Eamus, Derek; Taylor, Daniel

2015-01-01

The leaf area-to-sapwood area ratio (LA:SA) is a key plant trait that links photosynthesis to transpiration. The pipe model theory states that the sapwood cross-sectional area of a stem or branch at any point should scale isometrically with the area of leaves distal to that point. Optimization theory further suggests that LA:SA should decrease toward drier climates. Although acclimation of LA:SA to climate has been reported within species, much less is known about the scaling of this trait with climate among species. We compiled LA:SA measurements from 184 species of Australian evergreen angiosperm trees. The pipe model was broadly confirmed, based on measurements on branches and trunks of trees from one to 27 years old. Despite considerable scatter in LA:SA among species, quantile regression showed strong (0.2 < R1 < 0.65) positive relationships between two climatic moisture indices and the lowermost (5%) and uppermost (5–15%) quantiles of log LA:SA, suggesting that moisture availability constrains the envelope of minimum and maximum values of LA:SA typical for any given climate. Interspecific differences in plant hydraulic conductivity are probably responsible for the large scatter of values in the mid-quantile range and may be an important determinant of tree morphology. PMID:25859331

Final report on the safety assessment of AloeAndongensis Extract, Aloe Andongensis Leaf Juice,aloe Arborescens Leaf Extract, Aloe Arborescens Leaf Juice, Aloe Arborescens Leaf Protoplasts, Aloe Barbadensis Flower Extract, Aloe Barbadensis Leaf, Aloe Barbadensis Leaf Extract, Aloe Barbadensis Leaf Juice,aloe Barbadensis Leaf Polysaccharides, Aloe Barbadensis Leaf Water, Aloe Ferox Leaf Extract, Aloe Ferox Leaf Juice, and Aloe Ferox Leaf Juice Extract.

PubMed

2007-01-01

Plant materials derived from the Aloe plant are used as cosmetic ingredients, including Aloe Andongensis Extract, Aloe Andongensis Leaf Juice, Aloe Arborescens Leaf Extract, Aloe Arborescens Leaf Juice, Aloe Arborescens Leaf Protoplasts, Aloe Barbadensis Flower Extract, Aloe Barbadensis Leaf, Aloe Barbadensis Leaf Extract, Aloe Barbadensis Leaf Juice, Aloe Barbadensis Leaf Polysaccharides, Aloe Barbadensis Leaf Water, Aloe Ferox Leaf Extract, Aloe Ferox Leaf Juice, and Aloe Ferox Leaf Juice Extract. These ingredients function primarily as skin-conditioning agents and are included in cosmetics only at low concentrations. The Aloe leaf consists of the pericyclic cells, found just below the plant's skin, and the inner central area of the leaf, i.e., the gel, which is used for cosmetic products. The pericyclic cells produce a bitter, yellow latex containing a number of anthraquinones, phototoxic compounds that are also gastrointestinal irritants responsible for cathartic effects. The gel contains polysaccharides, which can be acetylated, partially acetylated, or not acetylated. An industry established limit for anthraquinones in aloe-derived material for nonmedicinal use is 50 ppm or lower. Aloe-derived ingredients are used in a wide variety of cosmetic product types at concentrations of raw material that are 0.1% or less, although can be as high as 20%. The concentration of Aloe in the raw material also may vary from 100% to a low of 0.0005%. Oral administration of various anthraquinone components results in a rise in their blood concentrations, wide systemic distribution, accumulation in the liver and kidneys, and excretion in urine and feces; polysaccharide components are distributed systemically and metabolized into smaller molecules. aloe-derived material has fungicidal, antimicrobial, and antiviral activities, and has been effective in wound healing and infection treatment in animals. Aloe barbadensis (also known as Aloe vera)-derived ingredients were not toxic in acute oral studies using mice and rats. In parenteral studies, the LD(50) using mice was > 200 mg/kg, rats was > 50 mg/kg, and using dogs was > 50 mg/kg. In intravenous studies the LD(50) using mice was > 80 mg/kg, rats was > 15 mg/kg, and dogs was > 10 mg/kg. The 14-day no observed effect level (NOEL) for the Aloe polysaccharide, acemannan, in the diet of Sprague-Dawley rats, was 50,000 ppm or 4.1 to 4.6 g/kg day(-1). In a 3-month study using mice, Aloe vera (extracted in ethanol) given orally in drinking water at 100 mg/kg produced reproductive toxicity, inflammation, and mortality above that seen in control animals. Aloe vera extracted in methanol and given to mice at 100 mg/kg in drinking water for 3 months caused significant sperm damage compared to controls. Aloe barbadensis extracted with water and given to pregnant Charles Foster albino rats on gestational days (GDs) 0 through 9 was an abortifacient and produced skeletal abnormalities. Both negative and positive results were found in bacterial and mammalian cell genotoxicity assays using Aloe barbadensis-derived material, Aloe Ferox-derived material, and various anthraquinones derived from Aloe. Aloin (an anthraquinone) did not produce tumors when included in the feed of mice for 20 weeks, nor did aloin increase the incidence of colorectal tumors induced with 1,2-dimethylhydrazine. Aloe-emodin (an anthraquinone) given to mice in which tumor cells had been injected inhibited growth of malignant tumors. Other animal data also suggest that components of Aloe inhibit tumor growth and improve survival. Various in vitro assays also demonstrated anticarcinogenic activity of aloe-emodin. Diarrhea was the only adverse effect of note with the use of Aloe-derived ingredients to treat asthma, ischemic heart disease, diabetes, ulcers, skin disease, and cancer. Case reports include acute eczema, contact urticaria, and dermatitis in individuals who applied Aloe-derived ingredients topically. The Cosmetic Ingredient Review Expert Panel concluded that anthraquinone levels in the several Aloe Barbadensis extracts are well understood and can conform to the industry-established level of 50 ppm. Although the phototoxicity anthraquinone components of Aloe plants have been demonstrated, several clinical studies of preparations derived from Aloe barbadensis plants demonstrated no phototoxicity, confirming that the concentrations of anthraquinones in such preparations are too low to induce phototoxicity. The characterization of aloe-derived ingredients from other species is not clear. In the absence of well-characterized derivatives, biological studies of these materials are considered necessary. The studies needed are 28-day dermal toxicity studies on Aloe Andongensis Extract, Aloe Andongensis Leaf Juice, Aloe Arborescens Leaf Extract, Aloe Arborescens Leaf Juice, Aloe Ferox Leaf Extract, Aloe Ferox Leaf Juice, and Aloe Ferox Leaf Juice (ingredients should be tested at current use concentrations). In Aloe-derived ingredients used in cosmetics, regardless of species, anthraquinone levels should not exceed 50 ppm. The Cosmetic Ingredient Review Expert Panel advised the industry that the total polychlorobiphenyl (PCB)/pesticide contamination of any plant-derived cosmetic ingredient should be limited to not more than 40 ppm, with not more than 10 ppm for any specific residue and that limits were appropriate for the following impurities: arsenic (3 mg/kg maximum), heavy metals (20 mg/kg maximum), and lead (5 mg/kg maximum).

Prediction of leaf area in individual leaves of cherrybark oak seedlings (Quercus pagoda Raf.)

Treesearch

Yanfei Guo; Brian Lockhart; John Hodges

1995-01-01

The prediction of leaf area for cherrybark oak (Quercus pagoda Raf.) seedlings is important for studying the physiology of the species. Linear and polynomial models involving leaf length, width, fresh weight, dry weight, and internodal length were tested independently and collectively to predict leaf area. Twenty-nine cherrybark oak seedlings were...

Estimating leaf area and leaf biomass of open-grown deciduous urban trees

Treesearch

David J. Nowak

1996-01-01

Logarithmic regression equations were developed to predict leaf area and leaf biomass for open-grown deciduous urban trees based on stem diameter and crown parameters. Equations based on crown parameters produced more reliable estimates. The equations can be used to help quantify forest structure and functions, particularly in urbanizing and urban/suburban areas.

The sensitivity of stand-scale photosynthesis and transpiration to changes in atmospheric CO2 concentration and climate

NASA Astrophysics Data System (ADS)

Kruijt, B.; Barton, C.; Rey, A.; Jarvis, P. G.

The 3-dimensional forest model MAESTRO was used to simulate daily and annual photosynthesis and transpiration fluxes of forest stands and the sensitivity of these fluxes to potential changes in atmospheric CO2 concentration ([CO2]), temperature, water stress and phenology. The effects of possible feed-backs from increased leaf area and limitations to leaf nutrition were simulated by imposing changes in leaf area and nitrogen content. Two different tree species were considered: Picea sitchensis (Bong.) Carr., a conifer with long needle longevity and large leaf area, and Betula pendula Roth., a broad-leaved deciduous species with an open canopy and small leaf area. Canopy photosynthetic production in trees was predicted to increase with atmospheric [CO2] and length of the growing season and to decrease with increased water stress. Associated increases in leaf area increased production further only in the B. pendula canopy, where the original leaf area was relatively small. Assumed limitations in N uptake affected B. pendula more than P. sitchensis. The effect of increased temperature was shown to depend on leaf area and nitrogen content. The different sensitivities of the two species were related to their very different canopy structure. Increased [CO2] reduced transpiration, but larger leaf area, early leaf growth, and higher temperature all led to increased water use. These effects were limited by feedbacks from soil water stress. The simulations suggest that, with the projected climate change, there is some increase in stand annual `water use efficiency', but the actual water losses to the atmosphere may not always decrease.

Inter- and intraspecific variation in leaf economic traits in wheat and maize

PubMed Central

Hale, Christine E; Cerabolini, Bruno E L; Cornelissen, Johannes H C; Craine, Joseph; Gough, William A; Kattge, Jens; Tirona, Cairan K F

2018-01-01

Abstract Leaf Economics Spectrum (LES) trait variation underpins multiple agroecological processes and many prominent crop yield models. While there are numerous independent studies assessing trait variation in crops, to date there have been no comprehensive assessments of intraspecific trait variation (ITV) in LES traits for wheat and maize: the world’s most widespread crops. Using trait databases and peer-reviewed literature, we compiled over 700 records of specific leaf area (SLA), maximum photosynthetic rates (Amax) and leaf nitrogen (N) concentrations, for wheat and maize. We evaluated intraspecific LES trait variation, and intraspecific trait–environment relationships. While wheat and maize occupy the upper 90th percentile of LES trait values observed across a global species pool, ITV ranged widely across the LES in wheat and maize. Fertilization treatments had strong impacts on leaf N, while plant developmental stage (here standardized as the number of days since planting) had strong impacts on Amax; days since planting, N fertilization and irrigation all influenced SLA. When controlling for these factors, intraspecific responses to temperature and precipitation explained 39.4 and 43.7 % of the variation in Amax and SLA, respectively, but only 5.4 % of the variation in leaf N. Despite a long history of domestication in these species, ITV in wheat and maize among and within cultivars remains large. Intraspecific trait variation is a critical consideration to refine regional to global models of agroecosystem structure, function and food security. Considerable opportunities and benefits exist for consolidating a crop trait database for a wider range of domesticated plant species. PMID:29484152

Blade life span, structural investment, and nutrient allocation in giant kelp.

PubMed

Rodriguez, Gabriel E; Reed, Daniel C; Holbrook, Sally J

2016-10-01

The turnover of plant biomass largely determines the amount of energy flowing through an ecosystem and understanding the processes that regulate turnover has been of interest to ecologists for decades. Leaf life span theory has proven useful in explaining patterns of leaf turnover in relation to resource availability, but the predictions of this theory have not been tested for macroalgae. We measured blade life span, size, thickness, nitrogen content, pigment content, and maximum photosynthetic rate (P max) in the giant kelp (Macrocystis pyrifera) along a strong resource (light) gradient to test whether the predictions of leaf life span theory applied to this alga. We found that shorter blade life spans and larger blade areas were associated with increased light availability. In addition, nitrogen and P max decreased with blade age, and their decrease was greater in shorter lived blades. These observations are generally consistent with patterns observed for higher plants and the prevailing theory of leaf life span. By contrast, variation observed in pigments of giant kelp was inconsistent with that predicted by leaf life span theory, as blades growing in the most heavily shaded portion of the forest had the lowest chlorophyll content. This result may reflect the dual role of macroalgal blades in carbon fixation and nutrient absorption and the ability of giant kelp to modify blade physiology to optimize the acquisition of light and nutrients. Thus, the marine environment may place demands on resource acquisition and allocation that have not been previously considered with respect to leaf life span optimization.

Inter- and intraspecific variation in leaf economic traits in wheat and maize.

PubMed

Martin, Adam R; Hale, Christine E; Cerabolini, Bruno E L; Cornelissen, Johannes H C; Craine, Joseph; Gough, William A; Kattge, Jens; Tirona, Cairan K F

2018-02-01

Leaf Economics Spectrum (LES) trait variation underpins multiple agroecological processes and many prominent crop yield models. While there are numerous independent studies assessing trait variation in crops, to date there have been no comprehensive assessments of intraspecific trait variation (ITV) in LES traits for wheat and maize: the world's most widespread crops. Using trait databases and peer-reviewed literature, we compiled over 700 records of specific leaf area (SLA), maximum photosynthetic rates ( A max ) and leaf nitrogen (N) concentrations, for wheat and maize. We evaluated intraspecific LES trait variation, and intraspecific trait-environment relationships. While wheat and maize occupy the upper 90th percentile of LES trait values observed across a global species pool, ITV ranged widely across the LES in wheat and maize. Fertilization treatments had strong impacts on leaf N, while plant developmental stage (here standardized as the number of days since planting) had strong impacts on A max ; days since planting, N fertilization and irrigation all influenced SLA. When controlling for these factors, intraspecific responses to temperature and precipitation explained 39.4 and 43.7 % of the variation in A max and SLA, respectively, but only 5.4 % of the variation in leaf N. Despite a long history of domestication in these species, ITV in wheat and maize among and within cultivars remains large. Intraspecific trait variation is a critical consideration to refine regional to global models of agroecosystem structure, function and food security. Considerable opportunities and benefits exist for consolidating a crop trait database for a wider range of domesticated plant species.

[Leaf water potential of spring wheat and field pea under different tillage patterns and its relationships with environmental factors].

PubMed

Zhang, Ming; Zhang, Ren-Zhi; Cai, Li-Qun

2008-07-01

Based on a long-term experiment, the leaf water potential of spring wheat and field pea, its relationships with environmental factors, and the diurnal variations of leaf relative water content and water saturation deficient under different tillage patterns were studied. The results showed that during whole growth period, field pea had an obviously higher leaf water potential than spring wheat, but the two crops had similar diurnal variation trend of their leaf water potential, i.e., the highest in early morning, followed by a descent, and a gradual ascent after the descent. For spring wheat, the maximum leaf water potential appeared at its jointing and heading stages, followed by at booting and flowering stages, and the minimum appeared at filling stage. For field pea, the maximum leaf water potential achieved at squaring stage, followed by at branching and flowering stages, and the minimum was at podding stage. The leaf relative water content of spring wheat was the highest at heading stage, followed by at jointing and flowering stages, and achieved the minimum at filling stage; while the water saturation deficient was just in adverse. With the growth of field pea, its leaf relative water content decreased, but leaf water saturation deficient increased. The leaf water potential of both spring wheat and field pea had significant correlations with environmental factors, including soil water content, air temperature, solar radiation, relative air humidity, and air water potential. Path analysis showed that the meteorological factor which had the strongest effect on the diurnal variation of spring wheat' s and field pea' s leaf water potential was air water potential and air temperature, respectively. Compared with conventional tillage, the protective tillage patterns no-till, no-till plus straw mulching, and conventional tillage plus straw returning increased the leaf water potential and relative water content of test crops, and the effect of no-till plus straw mulching was most significant.

Light acclimation optimizes leaf functional traits despite height-related constraints in a canopy shading experiment.

PubMed

Coble, Adam P; Cavaleri, Molly A

2015-04-01

Within-canopy gradients of leaf functional traits have been linked to both light availability and vertical gradients in leaf water potential. While observational studies can reveal patterns in leaf traits, within-canopy experimental manipulations can provide mechanistic insight to tease apart multiple interacting drivers. Our objectives were to disentangle effects of height and light environment on leaf functional traits by experimentally shading branches along vertical gradients within a sugar maple (Acer saccharum) forest. Shading reduced leaf mass per area (LMA), leaf density, area-based leaf nitrogen (N(area)), and carbon:nitrogen (C:N) ratio, and increased mass-based leaf nitrogen (N(mass)), highlighting the importance of light availability on leaf morphology and chemistry. Early in the growing season, midday leaf water potential (Ψ(mid)), LMA, and N(area) were driven primarily by height; later in the growing season, light became the most important driver for LMA and Narea. Carbon isotope composition (δ(13)C) displayed strong, linear correlations with height throughout the growing season, but did not change with shading, implying that height is more influential than light on water use efficiency and stomatal behavior. LMA, leaf density, N(mass), C:N ratio, and δ(13)C all changed seasonally, suggesting that leaf ageing effects on leaf functional traits are equally as important as microclimatic conditions. Overall, our results indicate that: (1) stomatal sensitivity to vapor pressure deficit or Ψ(mid) constrains the supply of CO2 to leaves at higher heights, independent of light environment, and (2) LMA and N(area) distributions become functionally optimized through morphological acclimation to light with increasing leaf age despite height-related constraints.

Spatial distribution of SPAD value and determination of the suitable leaf for N diagnosis in cucumber

NASA Astrophysics Data System (ADS)

Hu, Jing; Li, Chenxiao; Wen, Yifang; Gao, Xinhao; Shi, Feifei; Han, Luhua

2018-01-01

To determine the best leaf position for nitrogen diagnosis in cucumber with SPAD meter, greenhouse experiments were carried out to study spatial distribution of SPAD value of different position of the 3rd fully expanded cucumber leaf in the effect of different nitrogen levels, and the correlations between SPAD values and nitrogen concentration of chlorophyll. The results show that there is remarkable different SPAD value in different positions of the 3rd fully expanded leaf in the flowering and fruiting stage. Comparing the coefficients of SPAD value variation, we find that the coefficient of variation of leaf edge was significantly higher than the edge of the main vein, and the coefficient of variation of triangular area of leaf tip is significantly higher than any other leaf area. There is a significant correlation between SPAD values and leaf nitrogen content. Preliminary study shows that triangular area of leaf tip from the 20% leaf tip to leaf edge is the best position for nitrogen diagnosis.

Modeling and measuring the nocturnal drainage flow in a high-elevation, subalpine forest with complex terrain

USGS Publications Warehouse

Yi, C.; Monson, Russell K.; Zhai, Z.; Anderson, D.E.; Lamb, B.; Allwine, G.; Turnipseed, A.A.; Burns, Sean P.

2005-01-01

The nocturnal drainage flow of air causes significant uncertainty in ecosystem CO2, H2O, and energy budgets determined with the eddy covariance measurement approach. In this study, we examined the magnitude, nature, and dynamics of the nocturnal drainage flow in a subalpine forest ecosystem with complex terrain. We used an experimental approach involving four towers, each with vertical profiling of wind speed to measure the magnitude of drainage flows and dynamics in their occurrence. We developed an analytical drainage flow model, constrained with measurements of canopy structure and SF6 diffusion, to help us interpret the tower profile results. Model predictions were in good agreement with observed profiles of wind speed, leaf area density, and wind drag coefficient. Using theory, we showed that this one-dimensional model is reduced to the widely used exponential wind profile model under conditions where vertical leaf area density and drag coefficient are uniformly distributed. We used the model for stability analysis, which predicted the presence of a very stable layer near the height of maximum leaf area density. This stable layer acts as a flow impediment, minimizing vertical dispersion between the subcanopy air space and the atmosphere above the canopy. The prediction is consistent with the results of SF6 diffusion observations that showed minimal vertical dispersion of nighttime, subcanopy drainage flows. The stable within-canopy air layer coincided with the height of maximum wake-to-shear production ratio. We concluded that nighttime drainage flows are restricted to a relatively shallow layer of air beneath the canopy, with little vertical mixing across a relatively long horizontal fetch. Insight into the horizontal and vertical structure of the drainage flow is crucial for understanding the magnitude and dynamics of the mean advective CO2 flux that becomes significant during stable nighttime conditions and are typically missed during measurement of the turbulent CO2 flux. The model and interpretation provided in this study should lead to research strategies for the measurement of these advective fluxes and their inclusion in the overall mass balance for CO2 at this site with complex terrain. Copyright 2005 by the American Geophysical Union.

Modeling and measuring the nocturnal drainage flow in a high-elevation, subalpine forest with complex terrain

NASA Astrophysics Data System (ADS)

Yi, Chuixiang; Monson, Russell K.; Zhai, Zhiqiang; Anderson, Dean E.; Lamb, Brian; Allwine, Gene; Turnipseed, Andrew A.; Burns, Sean P.

2005-11-01

The nocturnal drainage flow of air causes significant uncertainty in ecosystem CO2, H2O, and energy budgets determined with the eddy covariance measurement approach. In this study, we examined the magnitude, nature, and dynamics of the nocturnal drainage flow in a subalpine forest ecosystem with complex terrain. We used an experimental approach involving four towers, each with vertical profiling of wind speed to measure the magnitude of drainage flows and dynamics in their occurrence. We developed an analytical drainage flow model, constrained with measurements of canopy structure and SF6 diffusion, to help us interpret the tower profile results. Model predictions were in good agreement with observed profiles of wind speed, leaf area density, and wind drag coefficient. Using theory, we showed that this one-dimensional model is reduced to the widely used exponential wind profile model under conditions where vertical leaf area density and drag coefficient are uniformly distributed. We used the model for stability analysis, which predicted the presence of a very stable layer near the height of maximum leaf area density. This stable layer acts as a flow impediment, minimizing vertical dispersion between the subcanopy air space and the atmosphere above the canopy. The prediction is consistent with the results of SF6 diffusion observations that showed minimal vertical dispersion of nighttime, subcanopy drainage flows. The stable within-canopy air layer coincided with the height of maximum wake-to-shear production ratio. We concluded that nighttime drainage flows are restricted to a relatively shallow layer of air beneath the canopy, with little vertical mixing across a relatively long horizontal fetch. Insight into the horizontal and vertical structure of the drainage flow is crucial for understanding the magnitude and dynamics of the mean advective CO2 flux that becomes significant during stable nighttime conditions and are typically missed during measurement of the turbulent CO2 flux. The model and interpretation provided in this study should lead to research strategies for the measurement of these advective fluxes and their inclusion in the overall mass balance for CO2 at this site with complex terrain.

Satellite-derived estimates of forest leaf area index in southwest Western Australia are not tightly coupled to interannual variations in rainfall: implications for groundwater decline in a drying climate.

PubMed

Smettem, Keith R J; Waring, Richard H; Callow, John N; Wilson, Melissa; Mu, Qiaozhen

2013-08-01

There is increasing concern that widespread forest decline could occur in regions of the world where droughts are predicted to increase in frequency and severity as a result of climate change. The average annual leaf area index (LAI) is an indicator of canopy cover and the difference between the annual maximum and minimum LAI is an indicator of annual leaf turnover. In this study, we analyzed satellite-derived estimates of monthly LAI across forested coastal catchments of southwest Western Australia over a 12 year period (2000-2011) that included the driest year on record for the last 60 years. We observed that over the 12 year study period, the spatial pattern of average annual satellite-derived LAI values was linearly related to mean annual rainfall. However, interannual changes to LAI in response to changes in annual rainfall were far less than expected from the long-term LAI-rainfall trend. This buffered response was investigated using a physiological growth model and attributed to availability of deep soil moisture and/or groundwater storage. The maintenance of high LAIs may be linked to a long-term decline in areal average underground water storage and diminished summer flows, with an emerging trend toward more ephemeral flow regimes. © 2013 John Wiley & Sons Ltd.

Trait Acclimation Mitigates Mortality Risks of Tropical Canopy Trees under Global Warming

PubMed Central

Sterck, Frank; Anten, Niels P. R.; Schieving, Feike; Zuidema, Pieter A.

2016-01-01

There is a heated debate about the effect of global change on tropical forests. Many scientists predict large-scale tree mortality while others point to mitigating roles of CO2 fertilization and – the notoriously unknown – physiological trait acclimation of trees. In this opinion article we provided a first quantification of the potential of trait acclimation to mitigate the negative effects of warming on tropical canopy tree growth and survival. We applied a physiological tree growth model that incorporates trait acclimation through an optimization approach. Our model estimated the maximum effect of acclimation when trees optimize traits that are strongly plastic on a week to annual time scale (leaf photosynthetic capacity, total leaf area, stem sapwood area) to maximize carbon gain. We simulated tree carbon gain for temperatures (25–35°C) and ambient CO2 concentrations (390–800 ppm) predicted for the 21st century. Full trait acclimation increased simulated carbon gain by up to 10–20% and the maximum tolerated temperature by up to 2°C, thus reducing risks of tree death under predicted warming. Functional trait acclimation may thus increase the resilience of tropical trees to warming, but cannot prevent tree death during extremely hot and dry years at current CO2 levels. We call for incorporating trait acclimation in field and experimental studies of plant functional traits, and in models that predict responses of tropical forests to climate change. PMID:27242814

Vertical and Horizontal Vegetation Structure across Natural and Modified Habitat Types at Mount Kilimanjaro.

PubMed

Rutten, Gemma; Ensslin, Andreas; Hemp, Andreas; Fischer, Markus

2015-01-01

In most habitats, vegetation provides the main structure of the environment. This complexity can facilitate biodiversity and ecosystem services. Therefore, measures of vegetation structure can serve as indicators in ecosystem management. However, many structural measures are laborious and require expert knowledge. Here, we used consistent and convenient measures to assess vegetation structure over an exceptionally broad elevation gradient of 866-4550 m above sea level at Mount Kilimanjaro, Tanzania. Additionally, we compared (human)-modified habitats, including maize fields, traditionally managed home gardens, grasslands, commercial coffee farms and logged and burned forests with natural habitats along this elevation gradient. We distinguished vertical and horizontal vegetation structure to account for habitat complexity and heterogeneity. Vertical vegetation structure (assessed as number, width and density of vegetation layers, maximum canopy height, leaf area index and vegetation cover) displayed a unimodal elevation pattern, peaking at intermediate elevations in montane forests, whereas horizontal structure (assessed as coefficient of variation of number, width and density of vegetation layers, maximum canopy height, leaf area index and vegetation cover) was lowest at intermediate altitudes. Overall, vertical structure was consistently lower in modified than in natural habitat types, whereas horizontal structure was inconsistently different in modified than in natural habitat types, depending on the specific structural measure and habitat type. Our study shows how vertical and horizontal vegetation structure can be assessed efficiently in various habitat types in tropical mountain regions, and we suggest to apply this as a tool for informing future biodiversity and ecosystem service studies.

Correlations of leaf area with length and width measurements of leaves of black oak, white oak, and sugar maple

Treesearch

Philip M. Wargo

1978-01-01

Correlations of leaf area with length, width, and length times width of leaves of black oak, white oak, and sugar maple were determined to see if length and/or width could be used as accurate estimators of leaf area. The correlation of length times width with leaf area was high (r > + .95) for all three species. The linear equation Y = a + bX, where X = length times...

Bleaching of leaf litter and associated microfungi in subboreal and subalpine forests.

PubMed

Hagiwara, Yusuke; Matsuoka, Shunsuke; Hobara, Satoru; Mori, Akira S; Hirose, Dai; Osono, Takashi

2015-10-01

Fungal decomposition of lignin leads to the whitening, or bleaching, of leaf litter, especially in temperate and tropical forests, but less is known about such bleaching in forests of cooler regions, such as boreal and subalpine forests. The purposes of the present study were to examine the extent of bleached area on the surface of leaf litter and its variation with environmental conditions in subboreal and subalpine forests in Japan and to examine the microfungi associated with the bleaching of leaf litter by isolating fungi from the bleached portions of the litter. Bleached area accounted for 21.7%-32.7% and 2.0%-10.0% of total leaf area of Quercus crispula and Betula ermanii, respectively, in subboreal forests, and for 6.3% and 18.6% of total leaf area of B. ermanii and Picea jezoensis var. hondoensis, respectively, in a subalpine forest. In subboreal forests, elevation, C/N ratio and pH of the FH layer, and slope aspect were selected as predictor variables for the bleached leaf area. Leaf mass per area and lignin content were consistently lower in the bleached area than in the nonbleached area of the same leaves, indicating that the selective decomposition of acid unhydrolyzable residue (recalcitrant compounds such as lignin, tannins, and cutins) enhanced the mass loss of leaf tissues in the bleached portions. Isolates of a total of 11 fungal species (6 species of Ascomycota and 5 of Basidiomycota) exhibited leaf-litter-bleaching activity under pure culture conditions. Two fungal species (Coccomyces sp. and Mycena sp.) occurred in both subboreal and subalpine forests, which were separated from each other by approximately 1100 km.

Using Small Drone (UAS) Imagery to Bridge the Gap Between Field- and Satellite-Based Measurements of Vegetation Structure and Change

NASA Astrophysics Data System (ADS)

Mayes, M. T.; Estes, L. D.; Gago, X.; Debats, S. R.; Caylor, K. K.; Manfreda, S.; Oudemans, P.; Ciraolo, G.; Maltese, A.; Nadal, M.; Estrany, J.

2016-12-01

Leaf area is an important ecosystem variable that relates to vegetation biomass, productivity, water and nutrient use in natural and agricultural systems globally. Since the 1980s, optical satellite image-based estimates of leaf area based on indices such as Normalized Difference Vegetation Index (NDVI) have greatly improved understanding of vegetation structure, function, and responses to disturbance at landscape (10^3 km2) to continental (10^6 km2) spatial scales. However, at landscape scales, satellites have failed to capture many leaf area patterns indicative of vegetation succession, crop types, stress and other conditions important for ecological processes. Small drones (UAS - unmanned aerial systems) offer new means for assessing leaf area and vegetation structure at higher spatial resolutions (<1 m) and land cover features such as substrate exposure that may affect estimates of vegetation structure in satellite data. Yet it is unclear how differences in spatial and spectral resolution between UAS and satellite data affect their relationships to each other, and to common field measurements of leaf area (e.g. LiCOR photosensors) and land cover. Constraining these relationships is important for leveraging UAS data to improve scaling of field data on leaf area and biomass to satellite data from Landsat, Sentinel-2, and increasing numbers of commercial sensors. Here, we quantify relationships among field, UAS and satellite estimates of vegetation leaf area and biomass in three case study landscapes spanning semi-arid Mediterranean (Matera, Southern Italy and Mallorca, Spain) and North American temperate ecosystems (New Jersey, USA). We assess how land cover and sensor spectral characteristics affect UAS and satellite-derived NDVI, leaf-area and biomass estimates. Then, we assess the fidelity of UAS, WorldView-2, and Landsat leaf-area and biomass estimates to field-measured landscape changes and variability, including vegetation recovery from fire (Mallorca), and leaf-area and biomass variability due to orchard type and agro-ecosystem management (Matera, New Jersey). Finally, we highlight promising ways forward for improving field data collection and the use of UAS observations to monitor vegetation leaf-area and biomass change at landscape scales in natural and agricultural systems.

Effects of branch height on leaf gas exchange, branch hydraulic conductance and branch sap flux in open-grown ponderosa pine.

PubMed

Hubbard, Robert M; Bond, Barbara J; Senock, Randy S; Ryan, Michael G

2002-06-01

Recent studies have shown that stomata respond to changes in hydraulic conductance of the flow path from soil to leaf. In open-grown tall trees, branches of different heights may have different hydraulic conductances because of differences in path length and growth. We determined if leaf gas exchange, branch sap flux, leaf specific hydraulic conductance, foliar carbon isotope composition (delta13C) and ratios of leaf area to sapwood area within branches were dependent on branch height (10 and 25 m) within the crowns of four open-grown ponderosa pine (Pinus ponderosa Laws.) trees. We found no difference in leaf gas exchange or leaf specific hydraulic conductance from soil to leaf between the upper and lower canopy of our study trees. Branch sap flux per unit leaf area and per unit sapwood area did not differ between the 10- and 25-m canopy positions; however, branch sap flux per unit sapwood area at the 25-m position had consistently lower values. Branches at the 25-m canopy position had lower leaf to sapwood area ratios (0.17 m2 cm-2) compared with branches at the 10-m position (0.27 m2 cm-2) (P = 0.03). Leaf specific conductance of branches in the upper crown did not differ from that in the lower crown. Other studies at our site indicate lower hydraulic conductance, sap flux, whole-tree canopy conductance and photosynthesis in old trees compared with young trees. This study suggests that height alone may not explain these differences.

Height-related trends in leaf xylem anatomy and shoot hydraulic characteristics in a tall conifer: safety versus efficiency in water transport.

PubMed

Woodruff, D R; Meinzer, F C; Lachenbruch, B

2008-01-01

Hydraulic vulnerability of Douglas-fir (Pseudotsuga menziesii) branchlets decreases with height, allowing shoots at greater height to maintain hydraulic conductance (K shoot) at more negative leaf water potentials (Psi l). To determine the basis for this trend shoot hydraulic and tracheid anatomical properties of foliage from the tops of Douglas-fir trees were analysed along a height gradient from 5 to 55 m. Values of Psi l at which K shoot was substantially reduced, declined with height by 0.012 Mpa m(-1). Maximum K shoot was reduced by 0.082 mmol m(-2) MPa(-1) s(-1) for every 1 m increase in height. Total tracheid lumen area per needle cross-section, hydraulic mean diameter of leaf tracheid lumens, total number of tracheids per needle cross-section and leaf tracheid length decreased with height by 18.4 microm(2) m(-1), 0.029 microm m(-1), 0.42 m(-1) and 5.3 microm m(-1), respectively. Tracheid thickness-to-span ratio (tw/b)2 increased with height by 1.04 x 10(-3) m(-1) and pit number per tracheid decreased with height by 0.07 m(-1). Leaf anatomical adjustments that enhanced the ability to cope with vertical gradients of increasing xylem tension were attained at the expense of reduced water transport capacity and efficiency, possibly contributing to height-related decline in growth of Douglas fir.

Below- and above-ground controls on tree water use in lowland tropical forests

NASA Astrophysics Data System (ADS)

Meinzer, F. C.; Woodruff, D.; McCulloh, K.; Domec, J.

2012-12-01

Even in moist tropical forests, fluctuations in soil water availability and atmospheric evaporative demand can constrain tree water use. Our research in three lowland tropical forest sites in Panama over the past two decades has identified a series of tree biophysical and functional traits related to daily and seasonal patterns of uptake, transport and loss of water. Studies combining measurements of sap flow and natural abundance of hydrogen isotopes in soil and xylem water during the dry season show considerable variation in depth of soil water uptake among co-occurring species. Trees able to exploit progressively deeper sources of soil water during the dry season, as indicated by increasingly negative xylem water hydrogen isotope ratios, were also able to maintain constant or even increased rates of water use. Injections of a stable isotope tracer (deuterated water) into tree trunks revealed a considerable range of water transit and residence times among co-occurring, similarly-sized trees. Components of tree hydraulic architecture were also strong determinants of patterns of water use. Sapwood hydraulic capacitance, the amount of water released per unit change in tissue water potential, was a strong predictor of several tree water use and water relations traits, including sap velocity, water residence time, daily maximum branch xylem tension, and the time of day at which stomata began to increasingly restrict transpiration. Among early and late successional species, hydraulic traits such as trunk-to-branch tapering of xylem vessels, branch sap flux, branch sapwood specific conductivity and whole-tree leaf area-specific hydraulic conductance scaled uniformly with branch wood density. Consistent with differences in trunk-to-branch tapering of vessels between early and late successional species, the ratio of branch to trunk sap flux was substantially greater in early successional species. Among species, stomatal conductance and transpiration per unit leaf area scaled uniformly with branch leaf-specific conductivity and with the branch leaf area to sapwood area ratio; a tree architecture-based proxy for leaf-specific conductivity. At the canopy-atmosphere interface, a combination of high stomatal conductance and relatively large leaf size enhanced the role of the boundary layer over stomata in controlling transpiration (increased decoupling coefficient; omega). Uniform scaling of tree water use characteristics with simple biophysical, hydraulic and architectural traits across species may facilitate predictions of changes in tropical forest water use with shifts in species composition associated with climate change and changing land-use.

Carbohydrate production, balance and translocation in leaves, shoots and fruits of Montmorency sour cherry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kappes, E.M.

1986-01-01

Carbohydrate production, export and use were studied for different organs of sour cherry (Prunus cerasus L. Montmorency). Gross carbohydrate (/sup 14/CO/sub 2/) export started between 27.2 and 77.6% of full leaf expansion. The 10th leaf developing started export later than the 7th leaf, suggesting that higher carbohydrate availability during leaf expansion delays export initiation. In support of this, gross export started earlier (44.4-52.4% full expansion) after source leaf removal, than in the control (77.6%). Translocation was primarily vertical (following orthostichies). Most leaves of fruiting shoots exported bidirectionally to the apex and fruits, only leaves closest to fruits exported exclusively tomore » fruits during rapid cell division (Stage I) and rapid cell expansion (Stage III). Net export, determined from carbohydrate balance models started at 17 and 51% expansion for the 7th and terminal leaf, and at 26.5% of shoot elongation. Cumulative carbohydrate production of the 7th and terminal leaves during the first 9 and 11 days after emergence, exceeded carbohydrate accumulated at final size, 464.2 and 148.9 mg. A fruit carbohydrate balance was developed to determine contributions by fruit photosynthesis and fruit respiration, and to identify periods of greatest carbohydrate import. Fruit photosynthesis during development was characterized under different environmental conditions. Gross photosynthesis and chlorophyll content per fruit increased to a maximum during stage II and decreased thereafter. Gross photosynthesis approached a maximum at 40/sub 0/C. Since dark respiration increased exponentially over the same temperature range, net photosynthesis reached a maximum at 18/sup 0/C. Photorespiration was not detected.« less

Hyperspectral reflectance as a tool to measure biochemical and physiological traits in wheat

DOE PAGES

Silva-Perez, Viridiana; Molero, Gemma; Serbin, Shawn P.; ...

2017-12-22

Improving photosynthesis to raise wheat yield potential has emerged as a major target for wheat physiologists. Photosynthesis-related traits, such as nitrogen per unit leaf area (N area) and leaf dry mass per area (LMA), require laborious, destructive, laboratory-based methods, while physiological traits underpinning photosynthetic capacity, such as maximum Rubisco activity normalized to 25 °C (V cmax25) and electron transport rate (J), require time-consuming gas exchange measurements. The aim of this study was to assess whether hyperspectral reflectance (350–2500 nm) can be used to rapidly estimate these traits on intact wheat leaves. Predictive models were constructed using gas exchange and hyperspectralmore » reflectance data from 76 genotypes grown in glasshouses with different nitrogen levels and/or in the field under yield potential conditions. Models were developed using half of the observed data with the remainder used for validation, yielding correlation coefficients (R 2 values) of 0.62 for V cmax25, 0.7 for J, 0.81 for SPAD, 0.89 for LMA, and 0.93 for N area, with bias <0.7%. The models were tested on elite lines and landraces that had not been used to create the models. The bias varied between -2.3% and -5.5% while relative error of prediction was similar for SPAD but slightly greater for LMA and N area.« less

Hyperspectral reflectance as a tool to measure biochemical and physiological traits in wheat

DOE Office of Scientific and Technical Information (OSTI.GOV)

Silva-Perez, Viridiana; Molero, Gemma; Serbin, Shawn P.

Improving photosynthesis to raise wheat yield potential has emerged as a major target for wheat physiologists. Photosynthesis-related traits, such as nitrogen per unit leaf area (N area) and leaf dry mass per area (LMA), require laborious, destructive, laboratory-based methods, while physiological traits underpinning photosynthetic capacity, such as maximum Rubisco activity normalized to 25 °C (V cmax25) and electron transport rate (J), require time-consuming gas exchange measurements. The aim of this study was to assess whether hyperspectral reflectance (350–2500 nm) can be used to rapidly estimate these traits on intact wheat leaves. Predictive models were constructed using gas exchange and hyperspectralmore » reflectance data from 76 genotypes grown in glasshouses with different nitrogen levels and/or in the field under yield potential conditions. Models were developed using half of the observed data with the remainder used for validation, yielding correlation coefficients (R 2 values) of 0.62 for V cmax25, 0.7 for J, 0.81 for SPAD, 0.89 for LMA, and 0.93 for N area, with bias <0.7%. The models were tested on elite lines and landraces that had not been used to create the models. The bias varied between -2.3% and -5.5% while relative error of prediction was similar for SPAD but slightly greater for LMA and N area.« less

Leaf traits and associated ecosystem characteristics across subtropical and timberline forests in the Gongga Mountains, Eastern Tibetan Plateau

Treesearch

Tianxiang Luo; Ji Luo; Yude Pan

2005-01-01

Knowledge of how leaf characteristics might be used to deduce information on ecosystem functioning and how this scaling task could be done is limited. In this study, we present field data for leaf lifespan, specific leaf area (SLA) and mass and area-based leaf nitrogen concentrations (Nmass, Narea) of dominant tree species...

Leaf mass area, Feb2016-May2016, PA-SLZ, PA-PNM, PA-BCI: Panama

DOE Data Explorer

Ely, Kim [Brookhaven National Lab; Rogers, Alistair [Brookhaven National Lab; Serbin, Shawn [Brookhaven National Lab; Wu, Jin [BNL; Wolfe, Brett [Smithsonian; Dickman, Turin [Los Alamos National Lab; Collins, Adam [Los Alamos National Lab; Detto, Matteo [Princeton; Grossiord, Charlotte [Los Alamos National Lab; McDowell, Nate [Los Alamos National Lab; Michaletz, Sean

2017-01-01

Leaf mass per unit area measured on a monthly basis from Feb to April 2016 at SLZ and PNM. Data from BCI only available for March. This data was collected as part of the 2016 ENSO campaign. See related datasets (existing and future) for further sample details, leaf water potential, leaf spectra, gas exchange and leaf chemistry.

Convergence of tree water use within an arid-zone woodland.

PubMed

O'Grady, A P; Cook, P G; Eamus, D; Duguid, A; Wischusen, J D H; Fass, T; Worldege, D

2009-07-01

We examined spatial and temporal patterns of tree water use and aspects of hydraulic architecture in four common tree species of central Australia--Corymbia opaca, Eucalyptus victrix, E. camaldulensis and Acacia aneura--to better understand processes that constrain water use in these environments. These four widely distributed species occupy contrasting niches within arid environments including woodlands, floodplains and riparian environments. Measurements of tree water use and leaf water potential were made at two sites with contrasting water table depths during a period of high soil water availability following summer rainfall and during a period of low soil water availability following 7 months of very little rainfall during 2007. There were significant differences in specific leaf area (SLA), sapwood area to leaf area ratios and sapwood density between species. Sapwood to leaf area ratio increased in all species from April to November indicating a decline in leaf area per unit sapwood area. Despite very little rainfall in the intervening period three species, C. opaca, E. victrix and E. camaldulensis maintained high leaf water potentials and tree water use during both periods. In contrast, leaf water potential and water use in the A. aneura were significantly reduced in November compared to April. Despite contrasting morphology and water use strategies, we observed considerable convergence in water use among the four species. Wood density in particular was strongly related to SLA, sapwood area to leaf area ratios and soil to leaf conductance, with all four species converging on a common relationship. Identifying convergence in hydraulic traits can potentially provide powerful tools for scaling physiological processes in natural ecosystems.

The limits to tree height.

PubMed

Koch, George W; Sillett, Stephen C; Jennings, Gregory M; Davis, Stephen D

2004-04-22

Trees grow tall where resources are abundant, stresses are minor, and competition for light places a premium on height growth. The height to which trees can grow and the biophysical determinants of maximum height are poorly understood. Some models predict heights of up to 120 m in the absence of mechanical damage, but there are historical accounts of taller trees. Current hypotheses of height limitation focus on increasing water transport constraints in taller trees and the resulting reductions in leaf photosynthesis. We studied redwoods (Sequoia sempervirens), including the tallest known tree on Earth (112.7 m), in wet temperate forests of northern California. Our regression analyses of height gradients in leaf functional characteristics estimate a maximum tree height of 122-130 m barring mechanical damage, similar to the tallest recorded trees of the past. As trees grow taller, increasing leaf water stress due to gravity and path length resistance may ultimately limit leaf expansion and photosynthesis for further height growth, even with ample soil moisture.

Evolutionary History Underlies Plant Physiological Responses to Global Change Since the Last Glacial Maximum

NASA Astrophysics Data System (ADS)

Becklin, K. M.; Medeiros, J. S.; Sale, K. R.; Ward, J. K.

2014-12-01

Assessing family and species-level variation in physiological responses to global change across geologic time is critical for understanding factors that underlie changes in species distributions and community composition. Ancient plant specimens preserved within packrat middens are invaluable in this context since they allow for comparisons between co-occurring plant lineages. Here we used modern and ancient plant specimens preserved within packrat middens from the Snake Range, NV to investigate the physiological responses of a mixed montane conifer community to global change since the last glacial maximum. We used a conceptual model to infer relative changes in stomatal conductance and maximum photosynthetic capacity from measures of leaf carbon isotopes, stomatal characteristics, and leaf nitrogen content. Our results indicate that most of the sampled taxa decreased stomatal conductance and/or photosynthetic capacity from glacial to modern times. However, plant families differed in the timing and magnitude of these physiological responses. Additionally, leaf-level responses were more similar within plant families than within co-occurring species assemblages. This suggests that adaptation at the level of leaf physiology may not be the main determinant of shifts in community composition, and that plant evolutionary history may drive physiological adaptation to global change over recent geologic time.

Simplification of a light-based model for estimating final internode length in greenhouse cucumber canopies.

PubMed

Kahlen, Katrin; Stützel, Hartmut

2011-10-01

Light quantity and quality affect internode lengths in cucumber (Cucumis sativus), whereby leaf area and the optical properties of the leaves mainly control light quality within a cucumber plant community. This modelling study aimed at providing a simple, non-destructive method to predict final internode lengths (FILs) using light quantity and leaf area data. Several simplifications of a light quantity and quality sensitive model for estimating FILs in cucumber have been tested. The direct simplifications substitute the term for the red : far-red (R : FR) ratios, by a term for (a) the leaf area index (LAI, m(2) m(-2)) or (b) partial LAI, the cumulative leaf area per m(2) ground, where leaf area per m(2) ground is accumulated from the top of each plant until a number, n, of leaves per plant is reached. The indirect simplifications estimate the input R : FR ratio based on partial leaf area and plant density. In all models, simulated FILs were in line with the measured FILs over various canopy architectures and light conditions, but the prediction quality varied. The indirect simplification based on leaf area of ten leaves revealed the best fit with measured data. Its prediction quality was even higher than of the original model. This study showed that for vertically trained cucumber plants, leaf area data can substitute local light quality data for estimating FIL data. In unstressed canopies, leaf area over the upper ten ranks seems to represent the feedback of the growing architecture on internode elongation with respect to light quality. This highlights the role of this domain of leaves as the primary source for the specific R : FR signal controlling the final length of an internode and could therefore guide future research on up-scaling local processes to the crop level.

A hydraulic-photosynthetic model based on extended HLH and its application to Coast redwood (Sequoia sempervirens).

PubMed

Du, Ning; Fan, Jintu; Chen, Shuo; Liu, Yang

2008-07-21

Although recent investigations [Ryan, M.G., Yoder, B.J., 1997. Hydraulic limits to tree height and tree growth. Bioscience 47, 235-242; Koch, G.W., Sillett, S.C.,Jennings, G.M.,Davis, S.D., 2004. The limits to tree height. Nature 428, 851-854; Niklas, K.J., Spatz, H., 2004. Growth and hydraulic (not mechanical) constraints govern the scaling of tree height and mass. Proc. Natl Acad. Sci. 101, 15661-15663; Ryan, M.G., Phillips, N., Bond, B.J., 2006. Hydraulic limitation hypothesis revisited. Plant Cell Environ. 29, 367-381; Niklas, K.J., 2007. Maximum plant height and the biophysical factors that limit it. Tree Physiol. 27, 433-440; Burgess, S.S.O., Dawson, T.E., 2007. Predicting the limits to tree height using statistical regressions of leaf traits. New Phytol. 174, 626-636] suggested that the hydraulic limitation hypothesis (HLH) is the most plausible theory to explain the biophysical limits to maximum tree height and the decline in tree growth rate with age, the analysis is largely qualitative or based on statistical regression. Here we present an integrated biophysical model based on the principle that trees develop physiological compensations (e.g. the declined leaf water potential and the tapering of conduits with heights [West, G.B., Brown, J.H., Enquist, B.J., 1999. A general model for the structure and allometry of plant vascular systems. Nature 400, 664-667]) to resist the increasing water stress with height, the classical HLH and the biochemical limitations on photosynthesis [von Caemmerer, S., 2000. Biochemical Models of Leaf Photosynthesis. CSIRO Publishing, Australia]. The model has been applied to the tallest trees in the world (viz. Coast redwood (Sequoia sempervirens)). Xylem water potential, leaf carbon isotope composition, leaf mass to area ratio at different heights derived from the model show good agreements with the experimental measurements of Koch et al. [2004. The limits to tree height. Nature 428, 851-854]. The model also well explains the universal trend of declining growth rate with age.

Photosynthetic light capture and processing from cell to canopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stenberg, P.; DeLucia, E.H.; Schoettle, A.W.

1995-07-01

We have addressed the unique structural features of conifers, as they relate to photosynthetic production, at different levels of organization (from needle to canopy). Many concepts and measures must be defined for conifers so that they are consistent with the structural properties of needles and shoots. Consistency is needed in comparing the photosynthetic performance of conifers and broad leaves, wherein it is important to distinguish the effect of structural factors on light capture from differences in the photosynthetic response at a fixed interception. Needles differ from broad leaves both with respect to inner structure and external shape, which includes amore » continuum from nearly flat to cylindrical. For nonflat three-dimensional objects such as for conifer needles, total surface area is the natural measure. The meaning of the one-sided area of needles is not clear, but consistency requires that it be defined as half the total needle surface area, as concluded. Characteristic structural factors of conifers that affect their ability to harvest light are a deep canopy combined with a small needle size, which create an important penumbra effect, and the clustering of needles on shoots, which creates a discontinuous distribution of needle area. These factors imply that, at a fixed leaf area index, the intercepted PAR would be smaller in coniferous than in broad-leafed canopies, but the vertical gradient of light in conifers is less steep and light reaching the lower canopy is all penumbral (diffuse). Conifers can maintain a higher leaf area index, and this may be accomplished by a more even distribution of light between shoots at different locations in the canopy and also because shade shoots have a structure that effectively intercepts light. Broad leaves in general have higher maximum photosynthetic rates than do needles, and yet conifers are at least equally productive on a stand basis. Possible reasons are discussed.« less

[Effects of cropping patterns on photosynthesis characteristics of summer maize and its utilization of solar and heat resources].

PubMed

Zhu, Yuan-Gang; Dong, Shu-Ting; Zhang, Ji-Wang; Liu, Peng; Yang, Jin-Sheng; Jia, Chun-Lan; Liu, Jing-Guo; Li, Deng-Hai

2010-06-01

In order to investigate the effects of interplanting and direct seeding on the photosynthesis characteristics of summer maize and its utilization of solar and heat resources, two summer maize cultivars (Zhengdan 958 and Denghai 661) were planted in the farmlands of Denghai Seed Co. Ltd in Laizhou City of Shandong Province, with 67500 plants x hm(-2) and three sowing dates. The above-ground biomass, plant growth rate, leaf area index, and net photosynthetic rate per ear leaf were measured to reveal the photosynthesis characteristics of test cultivars. In the meantime, the characters of grain-filling were simulated by Richards' model, and the solar resource utilization efficiency of the cultivars was calculated, in combining with meteorological data. Comparing with interplanting, direct seeding increased the grain yield by 1.17%-3.33%, but decreased the thousand-grain weight significantly. Growth stages were extended under earlier sowing. The leaf area index and net photosynthetic rate from flowering to 30 d after anthesis were significantly higher under direct seeding than under interplanting, but after then, they decreased faster. Direct seeding induced a higher accumulation of dry matter and a faster plant growth rate before and after flowering. Under direct seeding, the maximum grain-filling rate reached earlier, the starting potential was higher, but the grain-filling period, active grain-filling period, and W(max) were lower, compared with those under interplanting. Also under direct seeding, the total accumulative temperature and solar radiation during growth period decreased by 150-350 degrees C x d and 200-400 MJ x m(-2), respectively, but the solar resource utilization efficiency of grain increased by 10.5%-24.7%. All the results suggested that direct seeding was superior to interplanting for the summer maize production under field condition. In order to enhance solar and heat utilization efficiency and excavate yield potential, it would be essential to improve the leaf photosynthesis efficiency and postpone leaf aging.

Climate influences the leaf area/sapwood area ratio in Scots pine.

PubMed

Mencuccini, M; Grace, J

1995-01-01

We tested the hypothesis that the leaf area/sapwood area ratio in Scots pine (Pinus sylvestris L.) is influenced by site differences in water vapor pressure deficit of the air (D). Two stands of the same provenance were selected, one in western Scotland and one in eastern England, so that effects resulting from age, genetic variability, density and fertility were minimized. Compared with the Scots pine trees at the cooler and wetter site in Scotland, the trees at the warmer and drier site in England produced less leaf area per unit of conducting sapwood area both at a stem height of 1.3 m and at the base of the live crown, whereas stem permeability was similar at both sites. Also, trees at the drier site had less leaf area per unit branch cross-sectional area at the branch base than trees at the wetter site. For each site, the average values for leaf area, sapwood area and permeability were used, together with values of transpiration rates at different D, to calculate average stem water potential gradients. Changes in the leaf area/sapwood area ratio acted to maintain a similar water potential gradient in the stems of trees at both sites despite climatic differences between the sites.

Predicted distribution of visible and near-infrared radiant flux above and below a transmittant leaf

NASA Technical Reports Server (NTRS)

Roberts, Dar A.; Adams, John B.; Smith, Milton O.

1990-01-01

The effects are studied analytically of leaf size, leaf height, and background reflectance on the upward and downward radiant flux (RF) of a leaf. The leaf is horizontal and isotropically scattering in the computer model which examines the light environment in three regions about the leaf. The spectral properties of the leaf are based on measurements of the big-leaf maple, and the model is interpreted in terms of relative RF which is defined as a percentage of the total light in the model. The results demonstrate the dependence of upward relative RF on the light's wavelength and background reflectance with large variations in the NIR. Brightness varies directly with distance from background with maximum brightness achieved at lower heights for smaller leaves. These and other results suggest that NIR canopy reflectance due to leaves is highly dependent on the background reflectance.

Endophytic Ability of Different Isolates of Entomopathogenic Fungi Beauveria bassiana (Balsamo) Vuillemin in Stem and Leaf Tissues of Maize (Zea mays L.).

PubMed

Renuka, S; Ramanujam, B; Poornesha, B

2016-06-01

The present study was conducted to examine the ability of six promising indigenous isolates of Beauveria bassiana (NBAII-Bb-5a, 7, 14, 19, 23 and 45) as an endophyte in maize stem and leaf tissues. Maize seedlings (var. Nithyashree) were inoculated with conidial suspensions and were examined for endophytic establishment in leaf and stems at different intervals during 15-90 days after treatment. All six isolates showed colonization in stem and leaf tissues with varying abilities of colonization and persistence. The mean percent colonization ranged from 7.41 to 20.37 % in older stem tissues and 3.70 to 21.29 % in young stem tissues and in leaf, it ranged from 6.46 to 27.78 % in older leaf tissues and 11.11 to 26.85 % in young leaf tissues. Among six isolates tested, Bb-23 isolate recorded the maximum mean colonization in older stem (20.37 %), older leaf (27.78 %) and in young stem (21.29 %). Bb-5a isolate showed maximum mean colonization in young leaf tissues (26.85 %). Persistence of inoculated fungal isolates decreased with increase in age of the plant. No physical symptoms of damage were observed in any of the B. bassiana treated plants. No colonization of B. bassiana was observed in the untreated control maize plants. The results obtained in plating and PCR techniques were similar with regard to the confirmation of endophytic establishment of B. bassiana. This study indicated the possibility of using B. bassiana as an endophyte in maize for management of maize stem borer, Chilo partellus.

Plant traits demonstrate that temperate and tropical giant eucalypt forests are ecologically convergent with rainforest not savanna.

PubMed

Tng, David Y P; Jordan, Greg J; Bowman, David M J S

2013-01-01

Ecological theory differentiates rainforest and open vegetation in many regions as functionally divergent alternative stable states with transitional (ecotonal) vegetation between the two forming transient unstable states. This transitional vegetation is of considerable significance, not only as a test case for theories of vegetation dynamics, but also because this type of vegetation is of major economic importance, and is home to a suite of species of conservation significance, including the world's tallest flowering plants. We therefore created predictions of patterns in plant functional traits that would test the alternative stable states model of these systems. We measured functional traits of 128 trees and shrubs across tropical and temperate rainforest - open vegetation transitions in Australia, with giant eucalypt forests situated between these vegetation types. We analysed a set of functional traits: leaf carbon isotopes, leaf area, leaf mass per area, leaf slenderness, wood density, maximum height and bark thickness, using univariate and multivariate methods. For most traits, giant eucalypt forest was similar to rainforest, while rainforest, particularly tropical rainforest, was significantly different from the open vegetation. In multivariate analyses, tropical and temperate rainforest diverged functionally, and both segregated from open vegetation. Furthermore, the giant eucalypt forests overlapped in function with their respective rainforests. The two types of giant eucalypt forests also exhibited greater overall functional similarity to each other than to any of the open vegetation types. We conclude that tropical and temperate giant eucalypt forests are ecologically and functionally convergent. The lack of clear functional differentiation from rainforest suggests that giant eucalypt forests are unstable states within the basin of attraction of rainforest. Our results have important implications for giant eucalypt forest management.

Plant Traits Demonstrate That Temperate and Tropical Giant Eucalypt Forests Are Ecologically Convergent with Rainforest Not Savanna

PubMed Central

Tng, David Y. P.; Jordan, Greg J.; Bowman, David M. J. S.

2013-01-01

Ecological theory differentiates rainforest and open vegetation in many regions as functionally divergent alternative stable states with transitional (ecotonal) vegetation between the two forming transient unstable states. This transitional vegetation is of considerable significance, not only as a test case for theories of vegetation dynamics, but also because this type of vegetation is of major economic importance, and is home to a suite of species of conservation significance, including the world’s tallest flowering plants. We therefore created predictions of patterns in plant functional traits that would test the alternative stable states model of these systems. We measured functional traits of 128 trees and shrubs across tropical and temperate rainforest – open vegetation transitions in Australia, with giant eucalypt forests situated between these vegetation types. We analysed a set of functional traits: leaf carbon isotopes, leaf area, leaf mass per area, leaf slenderness, wood density, maximum height and bark thickness, using univariate and multivariate methods. For most traits, giant eucalypt forest was similar to rainforest, while rainforest, particularly tropical rainforest, was significantly different from the open vegetation. In multivariate analyses, tropical and temperate rainforest diverged functionally, and both segregated from open vegetation. Furthermore, the giant eucalypt forests overlapped in function with their respective rainforests. The two types of giant eucalypt forests also exhibited greater overall functional similarity to each other than to any of the open vegetation types. We conclude that tropical and temperate giant eucalypt forests are ecologically and functionally convergent. The lack of clear functional differentiation from rainforest suggests that giant eucalypt forests are unstable states within the basin of attraction of rainforest. Our results have important implications for giant eucalypt forest management. PMID:24358359

Epidermal Micromorphology and Mesophyll Structure of Populus euphratica Heteromorphic Leaves at Different Development Stages

PubMed Central

Liu, Yubing; Li, Xinrong; Chen, Guoxiong; Li, Mengmeng; Liu, Meiling; Liu, Dan

2015-01-01

Leaf epidermal micromorphology and mesophyll structure during the development of Populus euphratica heteromorphic leaves, including linear, lanceolate, ovate, dentate ovate, dentate rhombic, dentate broad-ovate and dentate fan-shaped leaves, were studied by using electron and light microscopy. During development of heteromorphic leaves, epidermal appendages (wax crystals and trichomes) and special cells (mucilage cells and crystal idioblasts) increased in all leaf types while chloroplast ultrastructure and stomatal characters show maximum photosynthetic activity in dentate ovate and rhombic leaves. Also, functional analysis by subordinate function values shows that the maximum adaptability to adverse stress was exhibited in the broad type of mature leaves. The 12 heteromorphic leaf types are classified into three major groups by hierarchical cluster analysis: young, developing and mature leaves. Mature leaves can effectively obtain the highest stress resistance by combining the protection of xerophytic anatomy from drought stress, regulation of water uptake in micro-environment by mucilage and crystal idioblasts, and assistant defense of transpiration reduction through leaf epidermal appendages, which improves photosynthetic activity under arid desert conditions. Our data confirms that the main leaf function is differentiated during the developing process of heteromorphic leaves. PMID:26356300

Epidermal Micromorphology and Mesophyll Structure of Populus euphratica Heteromorphic Leaves at Different Development Stages.

PubMed

Liu, Yubing; Li, Xinrong; Chen, Guoxiong; Li, Mengmeng; Liu, Meiling; Liu, Dan

2015-01-01

Leaf epidermal micromorphology and mesophyll structure during the development of Populus euphratica heteromorphic leaves, including linear, lanceolate, ovate, dentate ovate, dentate rhombic, dentate broad-ovate and dentate fan-shaped leaves, were studied by using electron and light microscopy. During development of heteromorphic leaves, epidermal appendages (wax crystals and trichomes) and special cells (mucilage cells and crystal idioblasts) increased in all leaf types while chloroplast ultrastructure and stomatal characters show maximum photosynthetic activity in dentate ovate and rhombic leaves. Also, functional analysis by subordinate function values shows that the maximum adaptability to adverse stress was exhibited in the broad type of mature leaves. The 12 heteromorphic leaf types are classified into three major groups by hierarchical cluster analysis: young, developing and mature leaves. Mature leaves can effectively obtain the highest stress resistance by combining the protection of xerophytic anatomy from drought stress, regulation of water uptake in micro-environment by mucilage and crystal idioblasts, and assistant defense of transpiration reduction through leaf epidermal appendages, which improves photosynthetic activity under arid desert conditions. Our data confirms that the main leaf function is differentiated during the developing process of heteromorphic leaves.

Leaf area and tree increment dynamics of even-aged and multiaged lodgepole pine stands in Montana

Treesearch

Cassandra L. Kollenberg; Kevin L. O' Hara

1999-01-01

Age structure and distribution of leaf area index (LAI) of even and multiaged lodgepole pine (Pinus contorta var. latifolia Engelm.) stands were examined on three study areas in western and central Montana. Projected leaf area was determined based on a relationship with sapwood cross-sectional area at breast height. Stand structure and LAI varied considerably between...

Accumulation of Pb and Cu heavy metals in sea water, sediment, and leaf and root tissue of Enhalus sp. in the seagrass bed of Banten Bay

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fauziah, Faiza, E-mail: faiza.fauziah@gmail.com; Choesin, Devi N., E-mail: faiza.fauziah@gmail.com

2014-03-24

Banten Bay in Indonesia is a coastal area which has been highly affected by human activity. Previous studies have reported the presence of lead (Pb) and copper (Cu) heavy metals in the seawater of this area. This study was conducted to measure the accumulation of Pb and Cu in seawater, sediment, leaf tissue, and root tissue of the seagrass species Enhalus sp. Sampling was conducted at two observation stations in Banten Bay: Station 1 (St.1) was located closer to the coastline and to industrial plants as source of pollution, while Station 2 (St.2) was located farther away offshore. At eachmore » station, three sampling points were established by random sampling. Field sampling was conducted at two different dates, i.e., on 29 May 2012 and 30 June 2012. Samples were processed by wet ashing using concentrated HNO{sub 3} acid and measured using Atomic Absorption Spectrometry (AAS). Accumulation of Pb was only detected in sediment samples in St.1, while Cu was detected in all samples. Average concentrations of Cu in May were as follows: sediment St.1 = 0.731 ppm, sediment St.2 = 0.383 ppm, seawater St.1 = 0.163 ppm, seawater St.2 = 0.174 ppm, leaf St.1 = 0.102 ppm, leaf St.2 = 0.132 ppm, root St.1= 0.139 ppm, and root St.2 = 0.075 ppm. Average measurements of Cu in June were: sediment St.1 = 0.260 ppm, leaf St.1 = 0.335 ppm, leaf St.2 = 0.301 ppm, root St.1= 0.047 ppm, and root St.2 = 0.060 ppm. In June, Cu was undetected in St.2 sediment and seawater at both stations. In May, Cu concentration in seawater exceeded the maximum allowable threshold for water as determined by the Ministry of the Environment. Spatial and temporal variation in Pb and Cu accumulation were most probably affected by distance from source and physical conditions of the environment (e.g., water current and mixing)« less

Association of spectral development patterns with development stages of corn

NASA Technical Reports Server (NTRS)

Crist, E. P. (Principal Investigator)

1982-01-01

Association is made between the development stages of corn as defined by Hanway and the temporal-spectral development pattern of corn in a transformed data space derived from Landsat-MSS band reflectance values, using field-collected reflectance and associated data. Results indicate that the spectral vegetation index used (a reflectance equivalent of Tasseled Cap Greenness) reaches a maximum well before the stage at which corn is expected to achieve its peak leaf area index. Possible physiological and canopy geometry related causes for this and other results are presented.

Leaf anatomy mediates coordination of leaf hydraulic conductance and mesophyll conductance to CO2 in Oryza.

PubMed

Xiong, Dongliang; Flexas, Jaume; Yu, Tingting; Peng, Shaobing; Huang, Jianliang

2017-01-01

Leaf hydraulic conductance (K leaf ) and mesophyll conductance (g m ) both represent major constraints to photosynthetic rate (A), and previous studies have suggested that K leaf and g m is correlated in leaves. However, there is scarce empirical information about their correlation. In this study, K leaf , leaf hydraulic conductance inside xylem (K x ), leaf hydraulic conductance outside xylem (K ox ), A, stomatal conductance (g s ), g m , and anatomical and structural leaf traits in 11 Oryza genotypes were investigated to elucidate the correlation of H 2 O and CO 2 diffusion inside leaves. All of the leaf functional and anatomical traits varied significantly among genotypes. K leaf was not correlated with the maximum theoretical stomatal conductance calculated from stomatal dimensions (g smax ), and neither g s nor g smax were correlated with K x . Moreover, K ox was linearly correlated with g m and both were closely related to mesophyll structural traits. These results suggest that K leaf and g m are related to leaf anatomical and structural features, which may explain the mechanism for correlation between g m and K leaf . © 2016 The Authors. New Phytologist © 2016 New Phytologist Trust.

The Relationship between Anatomy and Photosynthetic Performance of Heterobaric Leaves1

PubMed Central

Nikolopoulos, Dimosthenis; Liakopoulos, Georgios; Drossopoulos, Ioannis; Karabourniotis, George

2002-01-01

Heterobaric leaves show heterogeneous pigmentation due to the occurrence of a network of transparent areas that are created from the bundle sheaths extensions (BSEs). Image analysis showed that the percentage of photosynthetically active leaf area (Ap) of the heterobaric leaves of 31 plant species was species dependent, ranging from 91% in Malva sylvestris to only 48% in Gynerium sp. Although a significant portion of the leaf surface does not correspond to photosynthetic tissue, the photosynthetic capacity of these leaves, expressed per unit of projected area (Pmax), was not considerably affected by the size of their transparent leaf area (At). This means that the photosynthetic capacity expressed per Ap (P*max) should increase with At. Moreover, the expression of P*max could be allowing the interpretation of the photosynthetic performance in relation to some critical anatomical traits. The P*max, irrespective of plant species, correlated with the specific leaf transparent volume (λt), as well as with the transparent leaf area complexity factor (CFAt), parameters indicating the volume per unit leaf area and length/density of the transparent tissues, respectively. Moreover, both parameters increased exponentially with leaf thickness, suggesting an essential functional role of BSEs mainly in thick leaves. The results of the present study suggest that although the Ap of an heterobaric leaf is reduced, the photosynthetic performance of each areole is increased, possibly due to the light transferring capacity of BSEs. This mechanism may allow a significant increase in leaf thickness and a consequent increase of the photosynthetic capacity per unit (projected) area, offering adaptive advantages in xerothermic environments. PMID:12011354

Leaf litter dynamics and nitrous oxide emission in a Mediterranean riparian forest: implications for soil nitrogen dynamics.

PubMed

Bernal, S; Butturini, A; Nin, E; Sabater, F; Sabater, S

2003-01-01

Mediterranean riparian zones can experience severe drought periods that lead to low soil moisture content, which dramatically affects their performance as nitrate removal systems. In the Mediterranean riparian zone of this study, we determined that N2O emission was practically nil. To understand the role of forest floor processes in nitrogen retention of a Mediterranean riparian area, we studied leaf litter dynamics of two tree species, London planetree [Platanus x acerifolia (Aiton) Willd.] and alder [Alnus glutinosa (L.) Gaertn.], for two years, along with soil nitrogen mineralization rates. Annual leaf litter fall equaled 562.6 +/- 10.1 (standard error) g dry wt. m(-2), 68% of which was planetree and 32% of which was alder. The temporal distribution of litterfall showed a two-peak annual cycle, one occurring in midsummer, the other in autumn. Planetree provided the major input of organic nitrogen to the forest floor, and the amount of planetree leaves remaining on the forest floor was equivalent to approximately four years of stock. Leaf litter decomposition was three times higher for alder (decay coefficient [k] = 1.13 yr(-1)) than for planetree (k = 0.365 yr(-1)). Mineralization rates showed a seasonal pattern, with the maximum rate in summer (1.92 mg N kg(-1) d(-1)). Although the forest floor was an important sink for nitrogen due to planetree leaf accumulation, 7.5% of this leaf litter was scoured to the streambed by wind. This loss was irrelevant for alder leaves. Due to the litter quality, the forest floor of this Mediterranean riparian forest acts as a nitrogen sink.

Plasticity of vulnerability to leaf hydraulic dysfunction during acclimation to drought in grapevines: an osmotic-mediated process.

PubMed

Martorell, Sebastian; Medrano, Hipolito; Tomàs, Magdalena; Escalona, José M; Flexas, Jaume; Diaz-Espejo, Antonio

2015-03-01

Previous studies have reported correlation of leaf hydraulic vulnerability with pressure-volume parameters related to cell turgor. This link has been explained on the basis of the effects of turgor on connectivity among cells and tissue structural integrity, which affect leaf water transport. In this study, we tested the hypothesis that osmotic adjustment to water stress would shift the leaf vulnerability curve toward more negative water potential (Ψ leaf ) by increasing turgor at low Ψ leaf . We measured leaf hydraulic conductance (K leaf ), K leaf vulnerability [50 and 80% loss of K leaf (P50 and P80 ); |Ψ leaf | at 50 and 80% loss of K leaf , respectively), bulk leaf water relations, leaf gas exchange and sap flow in two Vitis vinifera cultivars (Tempranillo and Grenache), under two water treatments. We found that P50 , P80 and maximum K leaf decreased seasonally by more than 20% in both cultivars and watering treatments. However, K leaf at 2 MPa increased threefold, while osmotic potential at full turgor and turgor loss point decreased. Our results indicate that leaf resistance to hydraulic dysfunction is seasonally plastic, and this plasticity may be mediated by osmotic adjustment. © 2014 Scandinavian Plant Physiology Society.

Using the value of Lin's concordance correlation coefficient as a criterion for efficient estimation of areas of leaves of eelgrass from noisy digital images.

PubMed

Echavarría-Heras, Héctor; Leal-Ramírez, Cecilia; Villa-Diharce, Enrique; Castillo, Oscar

2014-01-01

Eelgrass is a cosmopolitan seagrass species that provides important ecological services in coastal and near-shore environments. Despite its relevance, loss of eelgrass habitats is noted worldwide. Restoration by replanting plays an important role, and accurate measurements of the standing crop and productivity of transplants are important for evaluating restoration of the ecological functions of natural populations. Traditional assessments are destructive, and although they do not harm natural populations, in transplants the destruction of shoots might cause undesirable alterations. Non-destructive assessments of the aforementioned variables are obtained through allometric proxies expressed in terms of measurements of the lengths or areas of leaves. Digital imagery could produce measurements of leaf attributes without the removal of shoots, but sediment attachments, damage infringed by drag forces or humidity contents induce noise-effects, reducing precision. Available techniques for dealing with noise caused by humidity contents on leaves use the concepts of adjacency, vicinity, connectivity and tolerance of similarity between pixels. Selection of an interval of tolerance of similarity for efficient measurements requires extended computational routines with tied statistical inferences making concomitant tasks complicated and time consuming. The present approach proposes a simplified and cost-effective alternative, and also a general tool aimed to deal with any sort of noise modifying eelgrass leaves images. Moreover, this selection criterion relies only on a single statistics; the calculation of the maximum value of the Concordance Correlation Coefficient for reproducibility of observed areas of leaves through proxies obtained from digital images. Available data reveals that the present method delivers simplified, consistent estimations of areas of eelgrass leaves taken from noisy digital images. Moreover, the proposed procedure is robust because both the optimal interval of tolerance of similarity and the reproducibility of observed leaf areas through digital image surrogates were independent of sample size. The present method provides simplified, unbiased and non-destructive measurements of eelgrass leaf area. These measurements, in conjunction with allometric methods, can predict the dynamics of eelgrass biomass and leaf growth through indirect techniques, reducing the destructive effect of sampling, fundamental to the evaluation of eelgrass restoration projects thereby contributing to the conservation of this important seagrass species.

Hydraulic patterns and safety margins, from stem to stomata, in three eastern U.S. tree species.

PubMed

Johnson, D M; McCulloh, K A; Meinzer, F C; Woodruff, D R; Eissenstat, D M

2011-06-01

Adequate water transport is necessary to prevent stomatal closure and allow for photosynthesis. Dysfunction in the water transport pathway can result in stomatal closure, and can be deleterious to overall plant health and survival. Although much is known about small branch hydraulics, little is known about the coordination of leaf and stem hydraulic function. Additionally, the daily variations in leaf hydraulic conductance (K(leaf)), stomatal conductance and water potential (Ψ(L)) have only been measured for a few species. The objective of the current study was to characterize stem and leaf vulnerability to hydraulic dysfunction for three eastern U.S. tree species (Acer rubrum, Liriodendron tulipifera and Pinus virginiana) and to measure in situ daily patterns of K(leaf), leaf and stem Ψ, and stomatal conductance in the field. Sap flow measurements were made on two of the three species to compare patterns of whole-plant water use with changes in K(leaf) and stomatal conductance. Overall, stems were more resistant to hydraulic dysfunction than leaves. Stem P50 (Ψ resulting in 50% loss in conductivity) ranged from -3.0 to -4.2 MPa, whereas leaf P50 ranged from -0.8 to -1.7 MPa. Field Ψ(L) declined over the course of the day, but only P. virginiana experienced reductions in K(leaf) (nearly 100% loss). Stomatal conductance was greatest overall in P. virginiana, but peaked midmorning and then declined in all three species. Midday stem Ψ in all three species remained well above the threshold for embolism formation. The daily course of sap flux in P. virginiana was bell-shaped, whereas in A. rubrum sap flux peaked early in the morning and then declined over the remainder of the day. An analysis of our data and data for 39 other species suggest that there may be at least three distinct trajectories of relationships between maximum K(leaf) and the % K(leaf) at Ψ(min). In one group of species, a trade-off between maximum K(leaf) and % K(leaf) at Ψ(min) appeared to exist, but no trade-off was evident in the other two trajectories.

Photosynthetic capacity and dry mass partitioning in dwarf and semi-dwarf wheat (Triticum aestivum L.)

NASA Technical Reports Server (NTRS)

Bishop, D. L.; Bugbee, B. G.

1998-01-01

Efficient use of space and high yields are critical for long-term food production aboard the International Space Station. The selection of a full dwarf wheat (less than 30 cm tall) with high photosynthetic and yield potential is a necessary prerequisite for growing wheat in the controlled, volume-limited environments available aboard long-term spaceflight missions. This study evaluated the photosynthetic capacity and carbon partitioning of a full-dwarf wheat cultivar, Super Dwarf, which is routinely used in spaceflight studies aboard U.S. space shuttle and NASA/Mir missions and made comparisons with other dwarf and semi-dwarf wheat cultivars utilized in other ground-based studies in plant space biology. Photosynthetic capacity of the flag leaf in two dwarf (Super Dwarf, BB-19), and three semi-dwarf (Veery-10, Yecora Rojo, IBWSN 199) wheat cultivars (Triticum aestivum L.) was assessed by measuring: net maximum photosynthetic rate, RuBP carboxylation efficiency, chlorophyll concentration and flag leaf area. Dry mass partitioning of carbohydrates to the leaves, sheaths, stems and ear was also assessed. Plants were grown under controlled environmental conditions in three replicate studies: slightly enriched CO2 (370 micromoles mol-1), high photosynthetic photon flux (1000 micromoles m-2 s-1; 58 mol m-2 d-1) for a 16 h photoperiod, 22/15 degrees C day/night temperatures, ample nutrients and water provided by one-half strength Hoagland's nutrient solution (Hoagland and Arnon, 1950). Photosynthetic capacity of the flag leaf was determined at anthesis using net CO2 exchange rate versus internal CO2 concentration curves measured under saturating light (2000 micromoles m-2 s-1) and CO2 (1000 micromoles mol-1). Dwarf wheat cultivars had greater photosynthetic capacities than the taller semi-dwarfs, they averaged 20% higher maximum net photosynthetic rates compared to the taller semi-dwarfs, but these higher rates occurred only at anthesis, had slightly greater carboxylation efficiencies and significantly increased chlorophyll concentrations per unit leaf area. The reduced-height wheat had significantly less dry mass fraction in the stem but greater dry mass partitioned to the ear than the taller semi-dwarfs (Yecora rojo, IBWSN-199). Studies with detached heads confirm that the head is a significant sink in the shorter wheat cultivars.

Senna leaf curl virus: a novel begomovirus identified in Senna occidentalis.

PubMed

Kumar, Jitesh; Alok, Anshu; Kumar, Jitendra; Tuli, Rakesh

2016-09-01

Begomoviruses are whitefly-transmitted, single-stranded DNA viruses that infect a variety of cultivated (crop) and non-cultivated (weed) plants. The present study identified a novel begomovirus and satellites (alpha- and betasatellite) in Senna occidentalis (syn. Cassia occidentalis) showing leaf curl symptoms. The begomovirus shared a maximum sequence identity of 88.6 % with french bean leaf curl virus (JQ866297), whereas the alphasatellite and the betasatellite shared identities of 98 % and 90 % with ageratum yellow vein India alphasatellite (LK054802) and papaya leaf curl betasatellite (HM143906), respectively. No other begomovirus or satellites were detected in the suspected plants. We propose to name the virus "senna leaf curl virus" (SenLCuV).

Rhododendron thickets alter N Cycling and soul extracellular enzyme activities in southern Appalachian hardwood forests

Treesearch

Nina Wurzburger; Ronald L. Hendrick

2007-01-01

Rhododendron maximum L., a spreading understory shrub, inhibits overstory. Regeneration and alters forest community structure in southern Appalachian hardwood forests. Using paired plots and reciprocal litter transplants in forests with and without R. maximum cover, we examined the influence of R. maximum on Leaf...

Seasonal Dynamics in Leaf Area Index in Intensively Managed Loblolly Pine

Treesearch

Timothy B. Harrington; Jason A. Gatch; Bruce E. Borders

2002-01-01

Leaf area index (LAI; leaf area per ground area) was measured monthly or bimonthly for two years (March 1999 to February 2001) with the LAI-2000 in intensively managed plantations of loblolly pine (Pinus taeda L.) at Eatonton and Waycross GA. Since establishment of the three age classes at each site, the stands have received combinations of complete...

Structural adjustments in resprouting trees drive differences in post-fire transpiration.

PubMed

Nolan, Rachael H; Mitchell, Patrick J; Bradstock, Ross A; Lane, Patrick N J

2014-02-01

Following disturbance many woody species are capable of resprouting new foliage, resulting in a reduced leaf-to-sapwood area ratio and altered canopy structure. We hypothesized that such changes would promote adjustments in leaf physiology, resulting in higher rates of transpiration per unit leaf area, consistent with the mechanistic framework proposed by Whitehead et al. (Whitehead D, Jarvis PG, Waring RH (1984) Stomatal conductance, transpiration and resistance to water uptake in a Pinus sylvestris spacing experiment. Can J For Res 14:692-700). We tested this in Eucalyptus obliqua L'Hér following a wildfire by comparing trees with unburnt canopies with trees that had been subject to 100% canopy scorch and were recovering their leaf area via resprouting. In resprouting trees, foliage was distributed along the trunk and on lateral branches, resulting in shorter hydraulic path lengths. We evaluated measurements of whole-tree transpiration and structural and physiological traits expected to drive any changes in transpiration. We used these structural and physiological measurements to parameterize the Whitehead et al. equation, and found that the expected ratio of transpiration per unit leaf area between resprouting and unburnt trees was 3.41. This is similar to the observed ratio of transpiration per unit leaf area, measured from sapflow observations, which was 2.89 (i.e., resprouting trees had 188% higher transpiration per unit leaf area). Foliage at low heights (<2 m) was found to be significantly different to foliage in the tree crown (14-18 m) in a number of traits, including higher specific leaf area, midday leaf water potential and higher rates of stomatal conductance and photosynthesis. We conclude that these post-fire adjustments in resprouting trees help to drive increased stomatal conductance and hydraulic efficiency, promoting the rapid return of tree-scale transpiration towards pre-disturbance levels. These transient patterns in canopy transpiration have important implications for modelling stand-level water fluxes in forests capable of resprouting, which is frequently done on the basis of the leaf area index.

Costs of measuring leaf area index of corn

NASA Technical Reports Server (NTRS)

Daughtry, C. S. T.; Hollinger, S. E.

1984-01-01

The magnitude of plant-to-plant variability of leaf area of corn plants selected from uniform plots was examined and four representative methods for measuring leaf area index (LAI) were evaluated. The number of plants required and the relative costs for each sampling method were calculated to detect 10, 20, and 50% differences in LAI using 0.05 and 0.01 tests of significance and a 90% probability of success (beta = 0.1). The natural variability of leaf area per corn plant was nearly 10%. Additional variability or experimental error may be introduced by the measurement technique employed and by nonuniformity within the plot. Direct measurement of leaf area with an electronic area meter had the lowest CV, required that the fewest plants be sampled, but required approximately the same amount of time as the leaf area/weight ratio method to detect comparable differences. Indirect methods based on measurements of length and width of leaves required more plants but less total time than the direct method. Unless the coefficients for converting length and width to area are verified frequently, the indirect methods may be biased. When true differences in LAI among treatments exceed 50% of mean, all four methods are equal. The method of choice depends on the resources available, the differences to be detected, and what additional information, such as leaf weight or stalk weight, is also desired.

[Effects of nitrogen application on canopy vertical structure, grain-leaf ratio and economic benefit of winter wheat under drip irrigation.

PubMed

Zhang, Na; Xu, Wen Xiu; Li, Lan Hai; Wu, Ni Ping; Wu, Pei Jie; Cheng, Xue Feng

2016-08-01

To optimize the fertilization rate of winter wheat under drip irrigation in Xinjiang region, a field investigation was carried out to assess effects of nitrogen (N) applications on canopy vertical structure, grain-leaf ratio, yield and economic benefit of winter wheat. Four rates of nitrogen application, 0 kg·hm -2 (N 0 ), 104 kg·hm -2 (N 1 ), 173 kg·hm -2 (N 2 ) and 242 kg·hm -2 (N 3 ) were set in a randomized block experimental design. Meantime, leaf and stem morphological characters, canopy temperature and humidity in flowering stage, grain-leaf area ratio, yield and yield components, economic benefits of winter wheat were observed under different treatments. The results showed that the leaf length and width at different positions of wheat under the nitrogen fertilization treatments were significantly higher than that without nitrogen fertilization (P<0.05), and plant height ranged from 65.57 to 81.58 cm. With an increasing rate of nitrogen fertilization, both leafarea index and stem diameter presented a trend of first increasing and then decreasing, and reached the maximum under N 2 treatment, which was 5.48 and 0.49 cm, respectively. Diurnal variation of canopy temperature and humidity were "convex" and "concave" shape, followed an order of N 0 >N 1 >N 2 >N 3 in temperature, but reversely in canopy humidity. The duration of high temperature higher than 35 ℃ were shorten 1 hour to 3.5 hours as the nitrogen application level increased, and there was significant difference between N 1 and N 3 on grain-leaf ratio. Yield and economic be-nefit decreased initially and then increased with increasing nitrogen application. Yield and economic benefit of treatment N 2 were 32.8% and 77.7% higher than those of treatment N 0 , 12.6% and 5.4% higher than those of treatment N 1 , and 5.2% and 4.2% higher than those of treatment N 3 , respectively. These results indicated that nitrogen application at about 173 kg·hm -2 could be recommended as the optimum rate for winter wheat, which had good leaf and plant morphology, appropriate canopy temperature and humidity, high yield and economic efficiency in the experiment area.

Biosynthesis of silver nanoparticles using Momordica charantia leaf broth: Evaluation of their innate antimicrobial and catalytic activities.

PubMed

Ajitha, B; Reddy, Y Ashok Kumar; Reddy, P Sreedhara

2015-05-01

Silver nanoparticles (AgNPs) were prepared through green route with the aid of Momordica charantia leaf extract as both reductant and stabilizer. X-ray diffraction pattern (XRD) and selected area electron diffraction (SAED) fringes revealed the structure of AgNPs as face centered cubic (fcc). Morphological studies elucidate the nearly spherical AgNPs formation with particle size in nanoscale. Biosynthesized AgNPs were found to be photoluminescent and UV-Vis absorption spectra showed one surface plasmon resonance peak (SPR) at 424nm attesting the spherical nanoparticles formation. XPS study provides the surface chemical nature and oxidation state of the synthesized nanoparticles. FTIR spectra ascertain the reduction and capping nature of phytoconstituents of leaf extract in AgNPs synthesis. Further, these AgNPs showed effective antimicrobial activity against tested pathogens and thus applicable as potent antimicrobial agent. In addition, the synthesized AgNPs were observed to have an excellent catalytic activity on the reduction of methylene blue by M. charantia which was confirmed by the decrement in maximum absorbance values of methylene blue with respect to time and is ascribed to electron relay effect. Copyright © 2015 Elsevier B.V. All rights reserved.

Spring leaf flush in aspen (Populus tremuloides) clones is altered by long-term growth at elevated carbon dioxide and elevated ozone concentration.

PubMed

McGrath, Justin M; Karnosky, David F; Ainsworth, Elizabeth A

2010-04-01

Early spring leaf out is important to the success of deciduous trees competing for light and space in dense forest plantation canopies. In this study, we investigated spring leaf flush and how long-term growth at elevated carbon dioxide concentration ([CO(2)]) and elevated ozone concentration ([O(3)]) altered leaf area index development in a closed Populus tremuloides (aspen) canopy. This work was done at the Aspen FACE experiment where aspen clones have been grown since 1997 in conditions simulating the [CO(2)] and [O(3)] predicted for approximately 2050. The responses of two clones were compared during the first month of spring leaf out when CO(2) fumigation had begun, but O(3) fumigation had not. Trees in elevated [CO(2)] plots showed a stimulation of leaf area index (36%), while trees in elevated [O(3)] plots had lower leaf area index (-20%). While individual leaf area was not significantly affected by elevated [CO(2)], the photosynthetic operating efficiency of aspen leaves was significantly improved (51%). There were no significant differences in the way that the two aspen clones responded to elevated [CO(2)]; however, the two clones responded differently to long-term growth at elevated [O(3)]. The O(3)-sensitive clone, 42E, had reduced individual leaf area when grown at elevated [O(3)] (-32%), while the tolerant clone, 216, had larger mature leaf area at elevated [O(3)] (46%). These results indicate a clear difference between the two clones in their long-term response to elevated [O(3)], which could affect competition between the clones, and result in altered genotypic composition in future atmospheric conditions. Published by Elsevier Ltd.

Pectin Methylesterification Impacts the Relationship between Photosynthesis and Plant Growth1[OPEN

PubMed Central

Kim, Sang-Jin; Renna, Luciana; Brandizzi, Federica

2016-01-01

Photosynthesis occurs in mesophyll cells of specialized organs such as leaves. The rigid cell wall encapsulating photosynthetic cells controls the expansion and distribution of cells within photosynthetic tissues. The relationship between photosynthesis and plant growth is affected by leaf area. However, the underlying genetic mechanisms affecting carbon partitioning to different aspects of leaf growth are not known. To fill this gap, we analyzed Arabidopsis plants with altered levels of pectin methylesterification, which is known to modulate cell wall plasticity and plant growth. Pectin methylesterification levels were varied through manipulation of cotton Golgi-related (CGR) 2 or 3 genes encoding two functionally redundant pectin methyltransferases. Increased levels of methylesterification in a line over-expressing CGR2 (CGR2OX) resulted in highly expanded leaves with enhanced intercellular air spaces; reduced methylesterification in a mutant lacking both CGR-genes 2 and 3 (cgr2/3) resulted in thin but dense leaf mesophyll that limited CO2 diffusion to chloroplasts. Leaf, root, and plant dry weight were enhanced in CGR2OX but decreased in cgr2/3. Differences in growth between wild type and the CGR-mutants can be explained by carbon partitioning but not by variations in area-based photosynthesis. Therefore, photosynthesis drives growth through alterations in carbon partitioning to new leaf area growth and leaf mass per unit leaf area; however, CGR-mediated pectin methylesterification acts as a primary factor in this relationship through modulation of the expansion and positioning of the cells in leaves, which in turn drive carbon partitioning by generating dynamic carbon demands in leaf area growth and leaf mass per unit leaf area. PMID:27208234

Pectin Methylesterification Impacts the Relationship between Photosynthesis and Plant Growth.

PubMed

M Weraduwage, Sarathi; Kim, Sang-Jin; Renna, Luciana; C Anozie, Fransisca; D Sharkey, Thomas; Brandizzi, Federica

2016-06-01

Photosynthesis occurs in mesophyll cells of specialized organs such as leaves. The rigid cell wall encapsulating photosynthetic cells controls the expansion and distribution of cells within photosynthetic tissues. The relationship between photosynthesis and plant growth is affected by leaf area. However, the underlying genetic mechanisms affecting carbon partitioning to different aspects of leaf growth are not known. To fill this gap, we analyzed Arabidopsis plants with altered levels of pectin methylesterification, which is known to modulate cell wall plasticity and plant growth. Pectin methylesterification levels were varied through manipulation of cotton Golgi-related (CGR) 2 or 3 genes encoding two functionally redundant pectin methyltransferases. Increased levels of methylesterification in a line over-expressing CGR2 (CGR2OX) resulted in highly expanded leaves with enhanced intercellular air spaces; reduced methylesterification in a mutant lacking both CGR-genes 2 and 3 (cgr2/3) resulted in thin but dense leaf mesophyll that limited CO2 diffusion to chloroplasts. Leaf, root, and plant dry weight were enhanced in CGR2OX but decreased in cgr2/3. Differences in growth between wild type and the CGR-mutants can be explained by carbon partitioning but not by variations in area-based photosynthesis. Therefore, photosynthesis drives growth through alterations in carbon partitioning to new leaf area growth and leaf mass per unit leaf area; however, CGR-mediated pectin methylesterification acts as a primary factor in this relationship through modulation of the expansion and positioning of the cells in leaves, which in turn drive carbon partitioning by generating dynamic carbon demands in leaf area growth and leaf mass per unit leaf area. © 2016 American Society of Plant Biologists. All Rights Reserved.

Carbohydrate Partitioning and the Capacity of Apparent Nitrogen Fixation of Soybean Plants Grown Outdoors

PubMed Central

Millhollon, Eddie P.; Williams, Larry E.

1986-01-01

Patterns of leaf carbohydrate partitioning and nodule activity in soybean plants grown under natural conditions and the irradiance level required to produce sufficient carbohydrate to obtain maximum rates of apparent N2-fixation (acetylene reduction) were measured. Soybean plants, grown outdoors, maintained constant levels of leaf soluble sugars while leaf starch pools varied diurnally. When root temperature was kept at 25°C and shoot temperature was allowed to vary with ambient temperature, the plants maintained constant rates of apparent N2-fixation and root+nodule respiration. Results from a second experiment, in which the entire plant was kept at 25°C, were similar to those of the first experiment. Shoot carbon exchange rate of plants from the second experiment was light saturated at photosynthetic photon flux densities between 400 and 600 micromoles per square meter per second. When plants were subjected to an extended 40-hour dark period to deplete carbohydrate reserves, apparent N2-fixation was unaffected during the first 10 hours of darkness, decreased rapidly between 10 and 16 hours, and plateaued at one-third the initial level thereafter. After the extended dark period, plants were exposed to photosynthetic photon flux density from 200 to 1000 micromoles per square meter per second for 10 hours. Photosynthetic photon flux densities of 200 micromoles per square meter per second and greater resulted in maximum leaf soluble sugar content and nodule activity. Leaf starch content increased with irradiance levels up to 600 micromoles per square meter per second with no further increase at higher irradiance levels. Results presented here indicate that maximum nodule activity occurs at irradiance levels that do not saturate the plant's photosynthetic apparatus. This response would allow for maximum N2-fixation to occur in a nodulated legume during periods of inclement weather. PMID:16664789

Does initial spacing influence crown and hydraulic architecture of Eucalyptus marginata?

PubMed

Grigg, A H; Macfarlane, C; Evangelista, C; Eamus, D; Adams, M A

2008-05-01

Long-term declines in rainfall in south-western Australia have resulted in increased interest in the hydraulic characteristics of jarrah (Eucalyptus marginata Donn ex Smith) forest established in the region's drinking water catchments on rehabilitated bauxite mining sites. We hypothesized that in jarrah forest established on rehabilitated mine sites: (1) leaf area index (L) is independent of initial tree spacing; and (2) more densely planted trees have less leaf area for the same leaf mass, or the same sapwood area, and have denser sapwood. Initial stand densities ranged from about 600 to 9000 stems ha(-1), and trees were 18 years old at the time of sampling. Leaf area index was unaffected by initial stand density, except in the most sparsely stocked stands where L was 1.2 compared with 2.0-2.5 in stands at other spacings. The ratio of leaf area to sapwood area (A(l):A(s)) was unaffected by tree spacing or tree size and was 0.2 at 1.3 m height and 0.25 at the crown base. There were small increases in sapwood density and decreases in leaf specific area with increased spacing. Tree diameter or basal area was a better predictor of leaf area than sapwood area. At the stand scale, basal area was a good predictor of L (r(2) = 0.98, n = 15) except in the densest stands. We conclude that the hydraulic attributes of this forest type are largely independent of initial tree spacing, thus simplifying parameterization of stand and catchment water balance models.

Impacts of elevated ozone on growth and photosynthesis of Metasequoia glyptostroboides Hu et Cheng.

PubMed

Zhang, Weiwei; Feng, Zhaozhong; Wang, Xiaoke; Niu, Junfeng

2014-09-01

One-year-old Metasequoia glyptostroboides seedlings were exposed to non-filtered ambient air (NF) and elevated ozone (E-O3, NF+60 ppb) in open-top chambers for two years. E-O3 accelerated leaf senescence, as indicated by significant decreases in photosynthetic pigment contents with the elongation of O3 exposure. E-O3 significantly affected gas exchange and carboxylation, inducing reductions in light-saturated photosynthesis (Asat), the maximum activity of Rubisco (Vc,max) and the maximum electron transport rate (Jmax). Chl a/b, Vc,max/Jmax and stomatal limitation (l) were not affected. Stomatal conductance (gs) was significantly decreased by E-O3 in the first year, but remained unchanged in the second year. It can be inferred that the decrease in Asat by E-O3 was mainly attributed to the changes in non-stomatal factors. After two years' exposure, E-O3 caused significant decreases in canopy photosynthesis and leaf mass per area, and a significant increase in the number of branches, but induced slight, not significant decreases in growth and biomass. Therefore, it can be concluded that the carbon accumulation of the species M. glyptostroboides could be negatively affected after long-term exposure to high O3 concentration. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

Penetration of sunlight into a canopy - Explicit models based on vertical and horizontal leaf projections

NASA Technical Reports Server (NTRS)

Otterman, J.; Brakke, T.

1986-01-01

The projections of leaf areas onto a horizontal plane and onto a vertical plane are examined for their utility in characterizing canopies for sunlight penetration (direct beam only) models. These projections exactly specify the penetration if the projections on the principal plane of the normals to the top surfaces of the leaves are in the same quadrant as the sun. Inferring the total leaf area from these projections (and therefore the penetration as a function of the total leaf area) is possible only with a large uncertainty (up to + or - 32 percent) because the projections are a specific measure of the total leaf area only if the leaf angle distribution is known. It is expected that this uncertainty could be reduced to more acceptable levels by making an approximate assessment of whether the zenith angle distribution is that of an extremophile canopy.

Relationships of leaf dark respiration to leaf nitrogen, specific leaf area and leaf life-span: a test across biomes and functional groups.

PubMed

Reich, Peter B; Walters, Michael B; Ellsworth, David S; Vose, James M; Volin, John C; Gresham, Charles; Bowman, William D

1998-05-01

Based on prior evidence of coordinated multiple leaf trait scaling, we hypothesized that variation among species in leaf dark respiration rate (R d ) should scale with variation in traits such as leaf nitrogen (N), leaf life-span, specific leaf area (SLA), and net photosynthetic capacity (A max ). However, it is not known whether such scaling, if it exists, is similar among disparate biomes and plant functional types. We tested this idea by examining the interspecific relationships between R d measured at a standard temperature and leaf life-span, N, SLA and A max for 69 species from four functional groups (forbs, broad-leafed trees and shrubs, and needle-leafed conifers) in six biomes traversing the Americas: alpine tundra/subalpine forest, Colorado; cold temperate forest/grassland, Wisconsin; cool temperate forest, North Carolina; desert/shrubland, New Mexico; subtropical forest, South Carolina; and tropical rain forest, Amazonas, Venezuela. Area-based R d was positively related to area-based leaf N within functional groups and for all species pooled, but not when comparing among species within any site. At all sites, mass-based R d (R d-mass ) decreased sharply with increasing leaf life-span and was positively related to SLA and mass-based A max and leaf N (leaf N mass ). These intra-biome relationships were similar in shape and slope among sites, where in each case we compared species belonging to different plant functional groups. Significant R d-mass -N mass relationships were observed in all functional groups (pooled across sites), but the relationships differed, with higher R d at any given leaf N in functional groups (such as forbs) with higher SLA and shorter leaf life-span. Regardless of biome or functional group, R d-mass was well predicted by all combinations of leaf life-span, N mass and/or SLA (r 2 ≥ 0.79, P < 0.0001). At any given SLA, R d-mass rises with increasing N mass and/or decreasing leaf life-span; and at any level of N mass , R d-mass rises with increasing SLA and/or decreasing leaf life-span. The relationships between R d and leaf traits observed in this study support the idea of a global set of predictable interrelationships between key leaf morphological, chemical and metabolic traits.

Leaf Area Adjustment As an Optimal Drought-Adaptation Strategy

NASA Astrophysics Data System (ADS)

Manzoni, S.; Beyer, F.; Thompson, S. E.; Vico, G.; Weih, M.

2014-12-01

Leaf phenology plays a major role in land-atmosphere mass and energy exchanges. Much work has focused on phenological responses to light and temperature, but less to leaf area changes during dry periods. Because the duration of droughts is expected to increase under future climates in seasonally-dry as well as mesic environments, it is crucial to (i) predict drought-related phenological changes and (ii) to develop physiologically-sound models of leaf area dynamics during dry periods. Several optimization criteria have been proposed to model leaf area adjustment as soil moisture decreases. Some theories are based on the plant carbon (C) balance, hypothesizing that leaf area will decline when instantaneous net photosynthetic rates become negative (equivalent to maximization of cumulative C gain). Other theories draw on hydraulic principles, suggesting that leaf area should adjust to either maintain a constant leaf water potential (isohydric behavior) or to avoid leaf water potentials with negative impacts on photosynthesis (i.e., minimization of water stress). Evergreen leaf phenology is considered as a control case. Merging these theories into a unified framework, we quantify the effect of phenological strategy and climate forcing on the net C gain over the entire growing season. By accounting for the C costs of leaf flushing and the gains stemming from leaf photosynthesis, this metric assesses the effectiveness of different phenological strategies, under different climatic scenarios. Evergreen species are favored only when the dry period is relatively short, as they can exploit most of the growing season, and only incur leaf maintenance costs during the short dry period. In contrast, deciduous species that lower maintenance costs by losing leaves are advantaged under drier climates. Moreover, among drought-deciduous species, isohydric behavior leads to lowest C gains. Losing leaves gradually so as to maintain a net C uptake equal to zero during the driest period in the growing season provides the highest gain. Since these strategies are all defined based on often-modeled quantities, they can be implemented in ecosystem models depending on plant functional type and climate.

Representing winter wheat in the Community Land Model (version 4.5)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lu, Yaqiong; Williams, Ian N.; Bagley, Justin E.

Winter wheat is a staple crop for global food security, and is the dominant vegetation cover for a significant fraction of Earth's croplands. As such, it plays an important role in carbon cycling and land–atmosphere interactions in these key regions. Accurate simulation of winter wheat growth is not only crucial for future yield prediction under a changing climate, but also for accurately predicting the energy and water cycles for winter wheat dominated regions. We modified the winter wheat model in the Community Land Model (CLM) to better simulate winter wheat leaf area index, latent heat flux, net ecosystem exchange ofmore » CO 2, and grain yield. These included schemes to represent vernalization as well as frost tolerance and damage. We calibrated three key parameters (minimum planting temperature, maximum crop growth days, and initial value of leaf carbon allocation coefficient) and modified the grain carbon allocation algorithm for simulations at the US Southern Great Plains ARM site (US-ARM), and validated the model performance at eight additional sites across North America. We found that the new winter wheat model improved the prediction of monthly variation in leaf area index, reduced latent heat flux, and net ecosystem exchange root mean square error (RMSE) by 41 and 35 % during the spring growing season. The model accurately simulated the interannual variation in yield at the US-ARM site, but underestimated yield at sites and in regions (northwestern and southeastern US) with historically greater yields by 35 %.« less

Representing winter wheat in the Community Land Model (version 4.5)

NASA Astrophysics Data System (ADS)

Lu, Yaqiong; Williams, Ian N.; Bagley, Justin E.; Torn, Margaret S.; Kueppers, Lara M.

2017-05-01

Winter wheat is a staple crop for global food security, and is the dominant vegetation cover for a significant fraction of Earth's croplands. As such, it plays an important role in carbon cycling and land-atmosphere interactions in these key regions. Accurate simulation of winter wheat growth is not only crucial for future yield prediction under a changing climate, but also for accurately predicting the energy and water cycles for winter wheat dominated regions. We modified the winter wheat model in the Community Land Model (CLM) to better simulate winter wheat leaf area index, latent heat flux, net ecosystem exchange of CO2, and grain yield. These included schemes to represent vernalization as well as frost tolerance and damage. We calibrated three key parameters (minimum planting temperature, maximum crop growth days, and initial value of leaf carbon allocation coefficient) and modified the grain carbon allocation algorithm for simulations at the US Southern Great Plains ARM site (US-ARM), and validated the model performance at eight additional sites across North America. We found that the new winter wheat model improved the prediction of monthly variation in leaf area index, reduced latent heat flux, and net ecosystem exchange root mean square error (RMSE) by 41 and 35 % during the spring growing season. The model accurately simulated the interannual variation in yield at the US-ARM site, but underestimated yield at sites and in regions (northwestern and southeastern US) with historically greater yields by 35 %.

Representing winter wheat in the Community Land Model (version 4.5)

DOE PAGES

Lu, Yaqiong; Williams, Ian N.; Bagley, Justin E.; ...

2017-05-05

Winter wheat is a staple crop for global food security, and is the dominant vegetation cover for a significant fraction of Earth's croplands. As such, it plays an important role in carbon cycling and land–atmosphere interactions in these key regions. Accurate simulation of winter wheat growth is not only crucial for future yield prediction under a changing climate, but also for accurately predicting the energy and water cycles for winter wheat dominated regions. We modified the winter wheat model in the Community Land Model (CLM) to better simulate winter wheat leaf area index, latent heat flux, net ecosystem exchange ofmore » CO 2, and grain yield. These included schemes to represent vernalization as well as frost tolerance and damage. We calibrated three key parameters (minimum planting temperature, maximum crop growth days, and initial value of leaf carbon allocation coefficient) and modified the grain carbon allocation algorithm for simulations at the US Southern Great Plains ARM site (US-ARM), and validated the model performance at eight additional sites across North America. We found that the new winter wheat model improved the prediction of monthly variation in leaf area index, reduced latent heat flux, and net ecosystem exchange root mean square error (RMSE) by 41 and 35 % during the spring growing season. The model accurately simulated the interannual variation in yield at the US-ARM site, but underestimated yield at sites and in regions (northwestern and southeastern US) with historically greater yields by 35 %.« less

Patient visibility and ICU mortality: a conceptual replication.

PubMed

Lu, Yi; Ossmann, Michelle M; Leaf, David E; Factor, Philip H

2014-01-01

This study reanalyzes the data from a study by Leaf, Homel, and Factor (2010) titled "Relationship between ICU Design and Mortality" by adopting and developing objective visibility measures. Various studies attribute healthcare outcomes (patient falls, satisfaction) to a vague notion of patient room visibility. The study by Leaf and colleagues was the first to draw an independent association between patient mortality and patient room visibility, however "visibility" remains imprecise. The original patient dataset was obtained from Dr. Leaf. The 664 patient sample assigned across 12 rooms at the medical ICU at Columbia University Medical Center was reanalyzed in terms of targeted visibility; the unit of analysis was the room, n = 12. Several computer-based visibility measures of patient rooms were used: patient head visibility, patient room visibility, and field of view to nursing station. Patient head visibility was defined as the percentage of area within the central nursing station from which the patient head could be seen; patient room visibility was defined as the percentage of area within the central nursing station that could see the patient room (average value of all patient room grids); field of view was defined as the maximum viewing angle from the patient head to the central nursing station. Among the sickest patients (those with Acute Physiology and Chronic Health Evaluation II > 30), field of view accounted for 33.5% of the variance in ICU mortality, p = 0.049. Subtle differences in patient room visibility may have important effects on clinical outcomes. Case study, critical care/intensive care, methodology, outcomes.

Satellite derived estimates of forest leaf area index in South-west Western Australia are not tightly coupled to inter-annual variations in rainfall: implications for groundwater decline in a drying climate.

NASA Astrophysics Data System (ADS)

Smettem, Keith; Waring, Richard; Callow, Nik; Wilson, Melissa; Mu, Qiaozhen

2013-04-01

There is increasing concern that widespread forest decline could occur in regions of the world where droughts are predicted to increase in frequency and severity as a result of climate change. Ecological optimality proposes that the long term average canopy size of undisturbed perennial vegetation is tightly coupled to climate. The average annual leaf area index (LAI) is an indicator of canopy cover and the difference between the annual maximum and minimum LAI is an indicator of annual leaf turnover. In this study we analysed satellite-derived estimates of monthly LAI across forested coastal catchments of South-west Western Australia over a 12 year period (2000-2011) that included the driest year on record for the last 60 years. We observed that over the 12 year study period, the spatial pattern of average annual satellite-derived LAI values was linearly related to mean annual rainfall. However, inter-annual changes to LAI in response to changes in annual rainfall were far less than expected from the long-term LAI-rainfall trend. This buffered response was investigated using a physiological growth model and attributed to availability of deep soil moisture and/or groundwater storage. The maintenance of high LAIs may be linked to a long term decline in areal average underground water storage storage and diminished summer flows, with a trend towards more ephemeral flow regimes.

Density-dependent dynamics of a dominant rain forest tree change with juvenile stage and time of masting.

PubMed

Norghauer, Julian M; Newbery, David M

2016-05-01

Although negative density dependence (NDD) can facilitate tree species coexistence in forests, the underlying mechanisms can differ, and rarely are the dynamics of seedlings and saplings studied together. Herein we present and discuss a novel mechanism based on our investigation of NDD predictions for the large, grove-forming ectomycorrhizal mast fruiting tree, Microberlinia bisulcata (Caesalpiniaceae), in an 82.5-ha plot at Korup, Cameroon. We tested whether juvenile density, size, growth and survival decreases with increasing conspecific adult basal area for 3245 'new' seedlings and 540 'old' seedlings (< 75-cm tall) during an approximately 4-year study period (2008-2012) and for 234 'saplings' (≥ 75-cm tall) during an approximately 6-year study period (2008-2014). We found that the respective densities of new seedlings, old seedlings and saplings were positively, not and negatively related to increasing BA. Maximum leaf numbers and heights of old seedlings were negatively correlated with increasing basal areas, as were sapling heights and stem diameters. Whereas survivorship of new seedlings decreased by more than one-half with increasing basal area over its range in 2010-2012, that of old seedlings decreased by almost two-thirds, but only in 2008-2010, and was generally unrelated to conspecific seedling density. In 2010-2012 relative growth rates in new seedlings' heights decreased with increasing basal area, as well as with increasing seedling density, together with increasing leaf numbers, whereas old seedlings' growth was unrelated to either conspecific density or basal area. Saplings of below-average height had reduced survivorship with increasing basal area (probability decreasing from approx. 0.4 to 0.05 over the basal area range tested), but only sapling growth in terms of leaf numbers decreased with increasing basal area. These static and dynamic results indicate that NDD is operating within this system, possibly stabilizing the M. bisulcata population. However, these NDD patterns are unlikely to be caused by symmetric competition or by consumers. Instead, an alternative mechanism for conspecific adult-juvenile negative feedback is proposed, one which involves the interaction between tree phenology and ectomycorrhizal linkages.

Broad Anatomical Variation within a Narrow Wood Density Range—A Study of Twig Wood across 69 Australian Angiosperms

PubMed Central

Ziemińska, Kasia; Westoby, Mark; Wright, Ian J.

2015-01-01

Objectives Just as people with the same weight can have different body builds, woods with the same wood density can have different anatomies. Here, our aim was to assess the magnitude of anatomical variation within a restricted range of wood density and explore its potential ecological implications. Methods Twig wood of 69 angiosperm tree and shrub species was analyzed. Species were selected so that wood density varied within a relatively narrow range (0.38–0.62 g cm-3). Anatomical traits quantified included wood tissue fractions (fibres, axial parenchyma, ray parenchyma, vessels, and conduits with maximum lumen diameter below 15 μm), vessel properties, and pith area. To search for potential ecological correlates of anatomical variation the species were sampled across rainfall and temperature contrasts, and several other ecologically-relevant traits were measured (plant height, leaf area to sapwood area ratio, and modulus of elasticity). Results Despite the limited range in wood density, substantial anatomical variation was observed. Total parenchyma fraction varied from 0.12 to 0.66 and fibre fraction from 0.20 to 0.74, and these two traits were strongly inversely correlated (r = -0.86, P < 0.001). Parenchyma was weakly (0.24 ≤|r|≤ 0.35, P < 0.05) or not associated with vessel properties nor with height, leaf area to sapwood area ratio, and modulus of elasticity (0.24 ≤|r|≤ 0.41, P < 0.05). However, vessel traits were fairly well correlated with height and leaf area to sapwood area ratio (0.47 ≤|r|≤ 0.65, all P < 0.001). Modulus of elasticity was mainly driven by fibre wall plus vessel wall fraction rather than by the parenchyma component. Conclusions Overall, there seem to be at least three axes of variation in xylem, substantially independent of each other: a wood density spectrum, a fibre-parenchyma spectrum, and a vessel area spectrum. The fibre-parenchyma spectrum does not yet have any clear or convincing ecological interpretation. PMID:25906320

Elevated atmospheric CO2 concentration leads to increased whole-plant isoprene emission in hybrid aspen (Populus tremula × Populus tremuloides).

PubMed

Sun, Zhihong; Niinemets, Ülo; Hüve, Katja; Rasulov, Bahtijor; Noe, Steffen M

2013-05-01

Effects of elevated atmospheric [CO2] on plant isoprene emissions are controversial. Relying on leaf-scale measurements, most models simulating isoprene emissions in future higher [CO2] atmospheres suggest reduced emission fluxes. However, combined effects of elevated [CO2] on leaf area growth, net assimilation and isoprene emission rates have rarely been studied on the canopy scale, but stimulation of leaf area growth may largely compensate for possible [CO2] inhibition reported at the leaf scale. This study tests the hypothesis that stimulated leaf area growth leads to increased canopy isoprene emission rates. We studied the dynamics of canopy growth, and net assimilation and isoprene emission rates in hybrid aspen (Populus tremula × Populus tremuloides) grown under 380 and 780 μmol mol(-1) [CO2]. A theoretical framework based on the Chapman-Richards function to model canopy growth and numerically compare the growth dynamics among ambient and elevated atmospheric [CO2]-grown plants was developed. Plants grown under elevated [CO2] had higher C : N ratio, and greater total leaf area, and canopy net assimilation and isoprene emission rates. During ontogeny, these key canopy characteristics developed faster and stabilized earlier under elevated [CO2]. However, on a leaf area basis, foliage physiological traits remained in a transient state over the whole experiment. These results demonstrate that canopy-scale dynamics importantly complements the leaf-scale processes, and that isoprene emissions may actually increase under higher [CO2] as a result of enhanced leaf area production. © 2013 The Authors. New Phytologist © 2013 New Phytologist Trust.

Leaf density explains variation in leaf mass per area in rice between cultivars and nitrogen treatments.

PubMed

Xiong, Dongliang; Wang, Dan; Liu, Xi; Peng, Shaobing; Huang, Jianliang; Li, Yong

2016-05-01

Leaf mass per area (LMA) is an important leaf trait; however, correlations between LMA and leaf anatomical features and photosynthesis have not been fully investigated, especially in cereal crops. The objectives of this study were (a) to investigate the correlations between LMA and leaf anatomical traits; and (b) to clarify the response of LMA to nitrogen supply and its effect on photosynthetic nitrogen use efficiency (PNUE). In the present study, 11 rice varieties were pot grown under sufficient nitrogen (SN) conditions, and four selected rice cultivars were grown under low nitrogen (LN) conditions. Leaf anatomical traits, gas exchange and leaf N content were measured. There was large variation in LMA across selected rice varieties. Regression analysis showed that the variation in LMA was more closely related to leaf density (LD) than to leaf thickness (LT). LMA was positively related to the percentage of mesophyll tissue area (%mesophyll), negatively related to the percentage of epidermis tissue area (%epidermis) and unrelated to the percentage of vascular tissue area (%vascular). The response of LMA to N supplementation was dependent on the variety and was also mainly determined by the response of LD to N. Compared with SN, photosynthesis was significantly decreased under LN, while PNUE was increased. The increase in PNUE was more critical in rice cultivars with a higher LMA under SN supply. Leaf density is the major cause of the variation in LMA across rice varieties and N treatments, and an increase in LMA under high N conditions would aggravate the decrease in PNUE. © The Author 2016. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

A better way of representing stem area index in two-big-leaf models: the application and impact on canopy integration of leaf nitrogen content

NASA Astrophysics Data System (ADS)

Chen, M.; Butler, E. E.; Wythers, K. R.; Kattge, J.; Ricciuto, D. M.; Thornton, P. E.; Atkin, O. K.; Flores-Moreno, H.; Reich, P. B.

2017-12-01

In order to better estimate the carbon budget of the globe, accurately simulating gross primary productivity (GPP) in earth system models is critical. When upscaling leaf level photosynthesis to the canopy, climate models uses different big-leaf schemes. About half of the state-of-the-art earth system models use a "two-big-leaf" scheme that partitions canopies into direct and diffusively illuminated fractions to reduce high bias of GPP simulated by one-big-leaf models. Some two-big-leaf models, such as ACME (identical in this respect to CLM 4.5) add leaf area index (LAI) and stem area index (SAI) together when calculating canopy radiation transfer. This treatment, however, will result in higher fraction of sunlit leaves. It will also lead to an artificial overestimation of canopy nitrogen content. Here we introduce a new algorithm of simulating SAI in a two-big-leaf model. The new algorithm reduced the sunlit leave fraction of the canopy and conserved the nitrogen content from leaf to canopy level. The lower fraction of sunlit leaves reduced global GPP especially in tropical area. Compared to the default model, for the past 100 years (1909-2009), the averaged global annual GPP is lowered by 4.11 PgC year-1 using this new algorithm.

The relationship between leaf rolling and ascorbate-glutathione cycle enzymes in apoplastic and symplastic areas of Ctenanthe setosa subjected to drought stress.

PubMed

Saruhan, Neslihan; Terzi, Rabiye; Saglam, Aykut; Kadioglu, Asim

2009-01-01

The ascorbate-glutathione (ASC-GSH) cycle has an important role in defensive processes against oxidative damage generated by drought stress. In this study, the changes that take place in apoplastic and symplastic ASC-GSH cycle enzymes of the leaf and petiole were investigated under drought stress causing leaf rolling in Ctenanthe setosa (Rose.) Eichler (Marantaceae). Apoplastic and symplastic extractions of leaf and petiole were performed at different visual leaf rolling scores from 1 to 4 (1 is unrolled, 4 is tightly rolled and the others are intermediate forms). Glutathione reductase (GR), a key enzyme in the GSH regeneration cycle, and ascorbate (ASC) were present in apoplastic spaces of the leaf and petiole, whereas dehydroascorbate reductase (DHAR), which uses glutathione as reductant, monodehydroascorbate reductase (MDHAR), which uses NAD(P)H as reductant, and glutathione were absent. GR, DHAR and MDHAR activities increased in the symplastic and apoplastic areas of the leaf. Apoplastic and symplastic ASC and dehydroascorbate (DHA), the oxidized form of ascorbate, rose at all scores except score 4 of symplastic ASC in the leaf. On the other hand, while reduced glutathione (GSH) content was enhanced, oxidized glutathione (GSSG) content decreased in the leaf during rolling. As for the petiole, GR activity increased in the apoplastic area but decreased in the symplastic area. DHAR and MDHAR activities increased throughout all scores, but decreased to the score 1 level at score 4. The ASC content of the apoplast increased during leaf rolling. Conversely, symplastic ASC content increased at score 2, however decreased at the later scores. While the apoplastic DHA content declined, symplastic DHA rose at score 2, but later was down to the level of score 1. While GSH content enhanced during leaf rolling, GSSG content did not change except at score 2. As well, there were good correlations between leaf rolling and ASC-GSH cycle enzyme activities in the leaf (GR and DHAR) and leaf rolling and GSSG. These results showed that in apoplastic and symplastic areas, ASC-GSH cycle enzymes leading ROS detoxification may have a role in controlling leaf rolling.

Leaf traits in parental and hybrid species of Sorbus (Rosaceae).

PubMed

Durkovic, Jaroslav; Kardosová, Monika; Canová, Ingrid; Lagana, Rastislav; Priwitzer, Tibor; Chorvát, Dusan; Cicák, Alojz; Pichler, Viliam

2012-09-01

Knowledge of functional leaf traits can provide important insights into the processes structuring plant communities. In the genus Sorbus, the generation of taxonomic novelty through reticulate evolution that gives rise to new microspecies is believed to be driven primarily by a series of interspecific hybridizations among closely related taxa. We tested hypotheses for dispersion of intermediacy across the leaf traits in Sorbus hybrids and for trait linkages with leaf area and specific leaf area. Here, we measured and compared the whole complex of growth, vascular, and ecophysiological leaf traits among parental (Sorbus aria, Sorbus aucuparia, Sorbus chamaemespilus) and natural hybrid (Sorbus montisalpae, Sorbus zuzanae) species growing under field conditions. A recently developed atomic force microscopy technique, PeakForce quantitative nanomechanical mapping, was used to characterize the topography of cell wall surfaces of tracheary elements and to map the reduced Young's modulus of elasticity. Intermediacy was associated predominantly with leaf growth traits, whereas vascular and ecophysiological traits were mainly parental-like and transgressive phenotypes. Larger-leaf species tended to have lower modulus of elasticity values for midrib tracheary element cell walls. Leaves with a biomass investment related to a higher specific leaf area had a lower density. Leaf area- and length-normalized theoretical hydraulic conductivity was related to leaf thickness. For the whole complex of examined leaf traits, hybrid microspecies were mosaics of parental-like, intermediate, and transgressive phenotypes. The high proportion of transgressive character expressions found in Sorbus hybrids implies that generation of extreme traits through transgressive segregation played a key role in the speciation process.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, X; Yang, F

Purpose: Knowing MLC leaf positioning error over the course of treatment would be valuable for treatment planning, QA design, and patient safety. The objective of the current study was to quantify the MLC positioning accuracy for VMAT delivery of head and neck treatment plans. Methods: A total of 837 MLC log files were collected from 14 head and neck cancer patients undergoing full arc VMAT treatment on one Varian Trilogy machine. The actual and planned leaf gaps were extracted from the retrieved MLC log files. For a given patient, the leaf gap error percentage (LGEP), defined as the ratio ofmore » the actual leaf gap over the planned, was evaluated for each leaf pair at all the gantry angles recorded over the course of the treatment. Statistics describing the distribution of the largest LGEP (LLGEP) of the 60 leaf pairs including the maximum, minimum, mean, Kurtosis, and skewness were evaluated. Results: For the 14 studied patients, their PTV located at tonsil, base of tongue, larynx, supraglottis, nasal cavity, and thyroid gland with volume ranging from 72.0 cm{sup 3} to 602.0 cm{sup 3}. The identified LLGEP differed between patients. It ranged from 183.9% to 457.7% with a mean of 368.6%. For the majority of the patients, the LLGEP distributions peaked at non-zero positions and showed no obvious dependence on gantry rotations. Kurtosis and skewness, with minimum/maximum of 66.6/217.9 and 6.5/12.6, respectively, suggested relatively more peaked while right-skewed leaf error distribution pattern. Conclusion: The results indicate pattern of MLC leaf gap error differs between patients of lesion located at similar anatomic site. Understanding the systemic mechanisms underlying these observed error patterns necessitates examining more patient-specific plan parameters in a large patient cohort setting.« less

Functional traits and plasticity in response to light in seedlings of four Iberian forest tree species.

PubMed

Sánchez-Gómez, David; Valladares, Fernando; Zavala, Miguel A

2006-11-01

We investigated the differential roles of physiological and morphological features on seedling survivorship along an experimental irradiance gradient in four dominant species of cool temperate-Mediterranean forests (Quercus robur L., Quercus pyrenaica Willd., Pinus sylvestris L. and Pinus pinaster Ait.). The lowest photochemical efficiency (F(v)/F(m) in dark-adapted leaves) was reached in deep shade (1% of full sunlight) in all species except Q. robur, which had the lowest photochemical efficiency in both deep shade and 100% of full sunlight. Species differed significantly in their survival in 1% of full sunlight but exhibited similar survivorship in 6, 20 and 100% of full sunlight. Shade-tolerant oaks had lower leaf area ratios, shoot to root ratios, foliage allocation ratios and higher rates of allocation to structural biomass (stem plus thick roots) than shade-intolerant pines. Overall phenotypic plasticity for each species, estimated as the difference between the minimum and the maximum mean values of the ecophysiological variables studied at the various irradiances divided by the maximum mean value of those variables, was inversely correlated with shade tolerance. Observed morphology, allocation and plasticity conformed to a conservative resource-use strategy, although observed differences in specific leaf area, which was higher in shade-tolerant species, supported a carbon gain maximization strategy. Lack of a congruent suite of traits underlying shade tolerance in the studied species provides evidence of adaptation to multiple selective forces. Although the study was based on only four species, the importance of ecophysiological variables as determinants of interspecific differences in survival in limiting light was demonstrated.

Vertical and Horizontal Vegetation Structure across Natural and Modified Habitat Types at Mount Kilimanjaro

PubMed Central

Rutten, Gemma; Ensslin, Andreas; Hemp, Andreas; Fischer, Markus

2015-01-01

In most habitats, vegetation provides the main structure of the environment. This complexity can facilitate biodiversity and ecosystem services. Therefore, measures of vegetation structure can serve as indicators in ecosystem management. However, many structural measures are laborious and require expert knowledge. Here, we used consistent and convenient measures to assess vegetation structure over an exceptionally broad elevation gradient of 866–4550m above sea level at Mount Kilimanjaro, Tanzania. Additionally, we compared (human)-modified habitats, including maize fields, traditionally managed home gardens, grasslands, commercial coffee farms and logged and burned forests with natural habitats along this elevation gradient. We distinguished vertical and horizontal vegetation structure to account for habitat complexity and heterogeneity. Vertical vegetation structure (assessed as number, width and density of vegetation layers, maximum canopy height, leaf area index and vegetation cover) displayed a unimodal elevation pattern, peaking at intermediate elevations in montane forests, whereas horizontal structure (assessed as coefficient of variation of number, width and density of vegetation layers, maximum canopy height, leaf area index and vegetation cover) was lowest at intermediate altitudes. Overall, vertical structure was consistently lower in modified than in natural habitat types, whereas horizontal structure was inconsistently different in modified than in natural habitat types, depending on the specific structural measure and habitat type. Our study shows how vertical and horizontal vegetation structure can be assessed efficiently in various habitat types in tropical mountain regions, and we suggest to apply this as a tool for informing future biodiversity and ecosystem service studies. PMID:26406985

Effects of incandescent radiation on photosynthesis, growth rate and yield of 'Waldmann's Green' leaf lettuce

NASA Technical Reports Server (NTRS)

Knight, S. L.; Mitchell, C. A.

1989-01-01

Effects of different ratios incandescent (ln) to fluorescent (Fl) radiation were tested on growth of 'Waldmann's Green' leaf lettuce (Lactuca sativa L.) in a controlled environment. After 4 days of treatment, dry weight, leaf area, relative growth rate (RGR), net assimilation rate (NAR), leaf area ratio (LAR) and photosynthetic rate (Pn) were greater for plants grown at 84 rather than 16% of total irradiance (82 W m-2) from ln lamps. Although leaf dry weight and area were 12-17% greater at 84% ln after the first 8 days of treatment, there were no differences in RGR or Pn between treatments during the last 4 days. If 84% ln was compared with 50% ln, all cumulative growth parameters, RGR, NAR and Pn were greater for 84% ln during the first 4 days of treatment. However, during the second 4 days, RGR was greater for the 50% ln treatment, resulting in no net difference in leaf dry weight or area between treatments. Shifting from 84 to 50% ln radiation between the first and second 4 days of treatment increased plant dry weight, leaf area, RGR and NAR relative to those under 84% ln for 8 days continuously.

Differences in Leaf Flammability, Leaf Traits and Flammability-Trait Relationships between Native and Exotic Plant Species of Dry Sclerophyll Forest

PubMed Central

Murray, Brad R.; Hardstaff, Lyndle K.; Phillips, Megan L.

2013-01-01

The flammability of plant leaves influences the spread of fire through vegetation. Exotic plants invading native vegetation may increase the spread of bushfires if their leaves are more flammable than native leaves. We compared fresh-leaf and dry-leaf flammability (time to ignition) between 52 native and 27 exotic plant species inhabiting dry sclerophyll forest. We found that mean time to ignition was significantly faster in dry exotic leaves than in dry native leaves. There was no significant native-exotic difference in mean time to ignition for fresh leaves. The significantly higher fresh-leaf water content that was found in exotics, lost in the conversion from a fresh to dry state, suggests that leaf water provides an important buffering effect that leads to equivalent mean time to ignition in fresh exotic and native leaves. Exotic leaves were also significantly wider, longer and broader in area with significantly higher specific leaf area–but not thicker–than native leaves. We examined scaling relationships between leaf flammability and leaf size (leaf width, length, area, specific leaf area and thickness). While exotics occupied the comparatively larger and more flammable end of the leaf size-flammability spectrum in general, leaf flammability was significantly correlated with all measures of leaf size except leaf thickness in both native and exotic species such that larger leaves were faster to ignite. Our findings for increased flammability linked with larger leaf size in exotics demonstrate that exotic plant species have the potential to increase the spread of bushfires in dry sclerophyll forest. PMID:24260169

Evaluation of four methods for estimating leaf area of isolated trees

Treesearch

P.J. Peper; E.G. McPherson

2003-01-01

The accurate modeling of the physiological and functional processes of urban forests requires information on the leaf area of urban tree species. Several non-destructive, indirect leaf area sampling methods have shown good performance for homogenous canopies. These methods have not been evaluated for use in urban settings where trees are typically isolated and...

ESTIMATION OF LEAF AREA INDEX IN OPEN-CANOPY PONDEROSA PINE FORESTS AT DIFFERENT SUCCESSIONAL STAGES AND MANAGEMENT REGIMES IN OREGON. (R828309)

EPA Science Inventory

Abstract

Leaf area and its spatial distribution are key parameters in describing canopy characteristics. They determine radiation regimes and influence mass and energy exchange with the atmosphere. The evaluation of leaf area in conifer stands is particularly challengi...

A Comparison of Simulated and Field-Derived Leaf Area Index (LAI) and Canopy Height Values from Four Forest Complexes in the Southeastern USA

EPA Science Inventory

Vegetative leaf area is a critical input to models that simulate human and ecosystem exposure to atmospheric pollutants. Leaf area index (LAI) can be measured in the field or numerically simulated, but all contain some inherent uncertainty that is passed to the exposure assessmen...

Simulation and Failure Analysis of Car Bumper Made of Pineapple Leaf Fiber Reinforced Composite

NASA Astrophysics Data System (ADS)

Arbintarso, E. S.; Muslim, M.; Rusianto, T.

2018-02-01

The bumper car made of the Pineapple Leaf Fiber Reinforced Composite (PLFRC) is possible to be produced with the advantage of easy to get, and cheap. Pineapple leaf fiber has chosen as a natural fiber, which the maximum of the strength of 368 MPa. The objective of this study was to determine the maximum capability of front car bumpers using Pineapple Leaf Fiber Reinforced Composite materials through the process of simulating stress analysis with Solidworks 2014 software. The aim also to know the distribution of loads that occur on the front car bumper and predict the critical point position on the design of the bumper. The result will use to develop the alternative lightweight, cheap and environmentally friendly materials in general and the development of the use of pineapple fiber for automotive purposes in particular. Simulations and failure analysis have been conducted and showed an increased impact speed in line with increased displacement, strain, and stress that occur on the surface of the bumper. The bumper can withstand collisions at a speed of less than 70 kph.

Assessing atmospheric particulate matter distribution based on Saturation Isothermal Remanent Magnetization of herbaceous and tree leaves in a tropical urban environment.

PubMed

Barima, Yao Sadaiou Sabas; Angaman, Djédoux Maxime; N'gouran, Kobenan Pierre; Koffi, N'guessan Achille; Kardel, Fatemeh; De Cannière, Charles; Samson, Roeland

2014-02-01

Particulate matter (PM) emissions, and the associated human health risks, are likely to continue increasing in urban environments of developing countries like Abidjan (Ivory Cost). This study evaluated the potential of leaves of several herbaceous and tree species as bioindicators of urban particulate matter pollution, and its variation over different land use classes, in a tropical area. Four species well distributed (presence frequencies >90%) over all land use classes, easy to harvest and whose leaves are wide enough to be easily scanned were selected, i.e.: Amaranthus spinosus (Amaranthaceae), Eleusine indica (Poaceae), Panicum maximum (Poaceae) and Ficus benjamina (Moraceae). Leaf sampling of these species was carried out at 3 distances from the road and at 3 height levels. Traffic density was also noted and finally biomagnetic parameters of these leaves were determined. Results showed that Saturation Isothermal Remanent Magnetization (SIRM) of leaves was at least 4 times higher (27.5×10(-6)A) in the vicinity of main roads and industrial areas than in parks and residential areas. The main potential sources of PM pollution were motor vehicles and industries. The slightly hairy leaves of the herbaceous plant A. spinosus and the waxy leaves of the tree F. benjamina showed the highest SIRM (25×10(-6)A). Leaf SIRM increased with distance to road (R(2)>0.40) and declined with sampling height (R(2)=0.17). The distance between 0 and 5m from the road seemed to be the most vulnerable in terms of PM pollution. This study has showed that leaf SIRM of herbaceous and tree species can be used to assess PM exposure in tropical urban environments. © 2013.

Anthropogenic eutrophication affects the body size of Cymodocea nodosa in the North Aegean Sea: A long-term, scale-based approach.

PubMed

Vasileios, Papathanasiou; Sotiris, Orfanidis

2017-12-07

The variation of eleven Cymodocea nodosa metrics was studied along two anthropogenic gradients in the North Aegean Sea, in two separate periods (July 2004 and July 2013). The aim was to specify existing monitoring programs on different kind of human-induced or natural stress for a better decision-making support. Key water variables (N-NO 2 , N-NO 3 , N-NH 4 , P-PO 4 , Chl-a, attenuation coefficient-K, and suspended solids) along with the stress index MALUSI were also estimated in each sampling effort. All metrics (except one) showed significant differences (p<0.05) and highest variation at the meadows scale in both sampling periods. The body size, e.g., CymoSkew, total and maximum leaf length, and leaf area (cm 2 /shoot), rather than the abundance, e.g., shoot density (shoots/m 2 ), leaf area index (m 2 /m 2 ), metrics were related to anthropogenic eutrophication variables represented by N-NH 4 , N-NO 3, N/P and MALUSI. The temporal analysis was restricted to two (2) meadows and water variables that were common between the two periods. PERMANOVA and PCA of common meadows and metrics within nine years showed significant but not consistent differences. While the most impacted studied site of Viamyl remained unchanged, a significant improvement of water quality was observed in the second most impacted meadow of Nea Karvali, which however was reduced to half of its previous area. On the one hand that was the result of combined management practices in nearby aquacultures and lower industrial activities due to the economic crisis. On the contrary, dredging and excess siltation from changes in land catchments and construction of permanent structures may decrease seagrass abundance. Copyright © 2017 Elsevier Ltd. All rights reserved.

Hydraulic Failure Defines the Recovery and Point of Death in Water-Stressed Conifers[OA

PubMed Central

Brodribb, Tim J.; Cochard, Hervé

2009-01-01

This study combines existing hydraulic principles with recently developed methods for probing leaf hydraulic function to determine whether xylem physiology can explain the dynamic response of gas exchange both during drought and in the recovery phase after rewatering. Four conifer species from wet and dry forests were exposed to a range of water stresses by withholding water and then rewatering to observe the recovery process. During both phases midday transpiration and leaf water potential (Ψleaf) were monitored. Stomatal responses to Ψleaf were established for each species and these relationships used to evaluate whether the recovery of gas exchange after drought was limited by postembolism hydraulic repair in leaves. Furthermore, the timing of gas-exchange recovery was used to determine the maximum survivable water stress for each species and this index compared with data for both leaf and stem vulnerability to water-stress-induced dysfunction measured for each species. Recovery of gas exchange after water stress took between 1 and >100 d and during this period all species showed strong 1:1 conformity to a combined hydraulic-stomatal limitation model (r2 = 0.70 across all plants). Gas-exchange recovery time showed two distinct phases, a rapid overnight recovery in plants stressed to <50% loss of leaf hydraulic conductance (Kleaf) and a highly Ψleaf-dependent phase in plants stressed to >50% loss of Kleaf. Maximum recoverable water stress (Ψmin) corresponded to a 95% loss of Kleaf. Thus, we conclude that xylem hydraulics represents a direct limit to the drought tolerance of these conifer species. PMID:19011001

Distribution of Carbon Uptake Capacity of Plant Functional Groups Across the Canopy Gradient in Old-Growth Tropical Wet Forest in Costa Rica

NASA Astrophysics Data System (ADS)

Oberbauer, S. F.; Cruz, H. O.; Ryan, M. G.; Clark, D. B.; Clark, D. A.; Olivas, P.

2004-12-01

Because of the difficulties of accessing leaves within tree crowns, little is known about the photosynthetic capacity of different functional groups within tropical rain forest canopies. To address this deficiency, we measured photosynthetic capacity (Amax) in situ along vertical transects through old-growth forest canopy using a mobile walkup tower at the La Selva Biological Station in Costa Rica. We asked: What groups are responsible for most C-fixation and at what height in the canopy does most C-fixation occur? Photosynthesis (using a LI-COR Li-6400) and total leaf area were measured for all vascular plant species encountered within the tower footprint (4.6 m2). Plants were grouped into trees, palms, ferns, lianas, epiphytes, herbs, Pentaclethra macroloba (the dominant canopy tree), and vines. Amax values differed among functional groups. The ranking of Amax among the groups was trees > P. macroloba > palms > lianas > vines > epiphytes > herbs > ferns. Trees and P. macroloba had the highest photosynthetic rates, but the maximum rates occur at different heights. Amax of P. macroloba increases with canopy height to a maximum 10.3 \\mumol m-2 s-1 at 17.5 m. Amax of trees increases with canopy height (r2 = 0.77) and attains the highest Amax at 32.5 m (10.6 \\mumol m-2 s-1). Palms and lianas presented similar patterns of Amax. However, lianas reach the canopy top whereas palms are shorter and were not observed above 27.5 m. The maximum photosynthetic rates for both groups were: lianas 9.2 \\mumol m-2 s-1 at 27.5 m and palms 9.6 \\mumol m-2 s-1 at 17.5 m. By scaling the functional group Amax values with their leaf area, we estimated that most of the photosynthetic capacity occurs between 17.5 m and 37.5 m and is attributed mainly to trees, followed by P. macroloba and then lianas.

Isolation and expression profiling of GhNAC transcription factor genes in cotton (Gossypium hirsutum L.) during leaf senescence and in response to stresses.

PubMed

Shah, Syed Tariq; Pang, Chaoyou; Fan, Shuli; Song, Meizhen; Arain, Saima; Yu, Shuxun

2013-12-01

NAC (NAM, ATAF, and CUC) is a plant-specific transcription factor family with diverse roles in plant development and stress regulation. In this report, stress-responsive NAC genes (GhNAC8-GhNAC17) isolated from cotton (Gossypium hirsutum L.) were characterised in the context of leaf senescence and stress tolerance. The characterisation of NAC genes during leaf senescence has not yet been reported for cotton. Based on the sequence characterisation, these GhNACs could be classified into three groups belonging to three known NAC sub-families. Their predicted amino acid sequences exhibited similarities to NAC genes from other plant species. Senescent leaves were the sites of maximum expression for all GhNAC genes except GhNAC10 and GhNAC13, which showed maximum expression in fibres, collected from 25 days post anthesis (DPA) plants. The ten GhNAC genes displayed differential expression patterns and levels during natural and induced leaf senescence. Quantitative RT-PCR and promoter analyses suggest that these genes are induced by ABA, ethylene, drought, salinity, cold, heat, and other hormonal treatments. These results support a role for cotton GhNAC genes in transcriptional regulation of leaf senescence, stress tolerance and other developmental stages of cotton. © 2013.

Leaf Optical Properties in Higher Plants: Linking Spectral Characteristics with Plant Stress

NASA Technical Reports Server (NTRS)

Carter, Gregory A.; Knapp, Alan K.

1999-01-01

A number of studies have addressed responses of leaf spectral reflectance, transmittance, or absorptance to physiological stress. Stressors included dehydration, ozone, herbicides, disease, insufficient mycorrhizae and N fertilization, flooding and insects. Species included conifers, grasses, and broadleaved trees. Increased reflectance with maximum responses near 700 nm wavelength occurred in all cases. Varying the chlorophyll content in leaves or pigment extracts can simulate this effect. Thus, common optical responses to stress result from decreases in leaf chlorophyll contents or the capacity of chloroplasts to absorb light. Leaf optic can be quite sensitive to any stressor that alters soil-plant-atmosphere processes.

Interannual Variation in Stand Transpiration is Dependent Upon Tree Species

NASA Astrophysics Data System (ADS)

Ewers, B. E.; Mackay, D. S.; Burrows, S. N.; Ahl, D. E.; Samanta, S.

2003-12-01

In order to successfully predict transpirational water fluxes from forested watersheds, interannual variability in transpiration must be quantified and understood. In a heterogeneous forested landscape in northern Wisconsin, we quantified stand transpiration across four forest cover types representing more than 80 percent of the land area in order to 1) quantify differences in stand transpiration and leaf area over two years and 2) determine the mechanisms governing the changes in transpiration over two years. We measured sap flux in eight trees of each tree species in the four cover types. We found that in northern hardwoods, the leaf area of sugar maple increased between the two measurement years with transpiration per unit ground area increasing even more than could be explained by leaf area. In an aspen stand, tent caterpillars completely defoliated the stand for approximately a month until a new set of leaves flushed out. The new set of leaves resulted in a lower leaf area but the same transpiration per unit leaf area indicating there was no physiological compensation for the lower leaf area. At the same time, balsam fir growing underneath the aspen increased their transpiration rate in response to greater light penetration through the dominant aspen canopy Red pine had a thirty percent change in leaf area within a growing season due to multiple cohorts of leaves and transpiration followed this leaf area dynamic. In a forested wetland, white cedar transpiration was proportional to surface water depth between the two years. Despite the specific tree species' effects on stand transpiration, all species displayed a minimum water potential regulation resulting in a saturating response of transpiration to vapor pressure deficit that did not vary across the two years. This physiological set point will allow future water flux models to explain mechanistically interannual variability in transpiration of this and similar forests.

Effect of weed control treatments on total leaf area of plantation black walnut (Juglans nigra)

Treesearch

Jason Cook; Michael R. Saunders

2013-01-01

Determining total tree leaf area is necessary for describing tree carbon balance, growth efficiency, and other measures used in tree-level and stand-level physiological growth models. We examined the effects of vegetation control methods on the total leaf area of sapling-size plantation black walnut trees using allometric approaches. We found significant differences in...

The bias of a 2D view: Comparing 2D and 3D mesophyll surface area estimates using non-invasive imaging

USDA-ARS?s Scientific Manuscript database

The surface area of the leaf mesophyll exposed to intercellular airspace per leaf area (Sm) is closely associated with CO2 diffusion and photosynthetic rates. Sm is typically estimated from two-dimensional (2D) leaf sections and corrected for the three-dimensional (3D) geometry of mesophyll cells, l...

Effects of grazing on leaf traits and ecosystem functioning in Inner Mongolia grasslands: scaling from species to community

NASA Astrophysics Data System (ADS)

Zheng, S. X.; Ren, H. Y.; Lan, Z. C.; Li, W. H.; Wang, K. B.; Bai, Y. F.

2010-03-01

Understanding the mechanistic links between environmental drivers, human disturbance, plant functional traits, and ecosystem properties is a fundamental aspect of biodiversity-ecosystem functioning research. Recent studies have focused mostly on leaf-level traits or community-level weighted traits to predict species responses to grazing and the consequent change in ecosystem functioning. However, studies of leaf-level traits or community-level weighted traits seldom identify the mechanisms linking grazing impact on leaf traits to ecosystem functioning. Here, using a multi-organization-level approach, we examined the effects of grazing on leaf traits (i.e., leaf area, leaf dry mass and specific leaf area) and ecosystem functioning across six communities of three vegetation types along a soil moisture gradient in the Xilin River Basin of Inner Mongolia grassland, China. Our results showed that the effects of grazing on leaf traits differed substantially when scaling up from leaf-level to species, functional group (i.e., life forms and water ecotype types), and community levels; and they also varied with vegetation type or site conditions. The effects of grazing on leaf traits diminished progressively along the hierarchy of organizational levels in the meadow, whereas the impacts were predominantly negative and the magnitude of the effects increased considerably at higher organizational levels in the typical steppe. Soil water and nutrient availability, functional trade-offs between leaf size and number of leaves per individual, and differentiation in avoidance and tolerance strategies among coexisting species are likely to be responsible for the observed responses of leaf traits to grazing at different levels of organization and among vegetation types. Our findings also demonstrate that, at both the functional group and community levels, standing aboveground biomass increased with leaf area and specific leaf area. Compared with the large changes in leaf traits and standing aboveground biomass, the soil properties were relatively unaffected by grazing. Our study indicates that a multi-organization-level approach provides more robust and comprehensive predictions of the effects of grazing on leaf traits and ecosystem functioning.

Leaf Area Influence on Surface Layer in a Deciduous Forest. Part 2; Detecting Leaf Area and Surface Resistance During Transition Seasons

NASA Technical Reports Server (NTRS)

Sakai, Ricardo K.; Fitzjarrald, David R.; Moore, Kathleen E.; Sicker, John W.; Munger, Willian J.; Goulden, Michael L.; Wofsy, Steven C.

1996-01-01

Temperate deciduous forest exhibit dramatic seasonal changes in surface exchange properties following on the seasonal changes in leaf area index. The canopy resistance to water vapor transport r(sub c) decreased abruptly at leaf emergence in each year but then also continued to decrease slowly during the remaining growing season due to slowly increasing LAI. Canopy resistance and PAR-albedo (albedo from photosynthetically active radiation) began to increase about one month before leaf fall with the diminishment of CO2 gradient above the canopy as well. At this time evaporation begun to be controlled as if the canopy were leafless.

Chemical and mechanical changes during leaf expansion of four woody species of dry Restinga woodland.

PubMed

Schlindwein, C C D; Fett-Neto, A G; Dillenburg, L R

2006-07-01

Young leaves are preferential targets for herbivores, and plants have developed different strategies to protect them. This study aimed to evaluate different leaf attributes of presumed relevance in protection against herbivory in four woody species (Erythroxylum argentinum, Lithrea brasiliensis, Myrciaria cuspidata, and Myrsine umbellata), growing in a dry restinga woodland in southern Brazil. Evaluation of leaf parameters was made through single-point sampling of leaves (leaf mass per area and leaf contents of nitrogen, carbon, and pigments) at three developmental stages and through time-course sampling of expanding leaves (area and strength). Leaves of M. umbellata showed the highest leaf mass per area (LMA), the largest area, and the longest expansion period. On the other extreme, Myrc. cuspidata had the smallest LMA and leaf size, and the shortest expansion period. Similarly to L. brasiliensis, it displayed red young leaves. None of the species showed delayed-greening, which might be related to the high-irradiance growth conditions. Nitrogen contents reduced with leaf maturity and reached the highest values in the young leaves of E. argentinum and Myrc. cuspidata and the lowest in M. umbellata. Each species seems to present a different set of protective attributes during leaf expansion. Myrciaria cuspidata appears to rely mostly on chemical defences to protect its soft leaves, and anthocyanins might play this role at leaf youth, while M. umbellata seems to invest more on mechanical defences, even at early stages of leaf growth, as well as on a low allocation of nitrogen to the leaves. The other species display intermediate characteristics.

Large seasonal swings in leaf area of Amazon rainforests

PubMed Central

Myneni, Ranga B.; Yang, Wenze; Nemani, Ramakrishna R.; Huete, Alfredo R.; Dickinson, Robert E.; Knyazikhin, Yuri; Didan, Kamel; Fu, Rong; Negrón Juárez, Robinson I.; Saatchi, Sasan S.; Hashimoto, Hirofumi; Ichii, Kazuhito; Shabanov, Nikolay V.; Tan, Bin; Ratana, Piyachat; Privette, Jeffrey L.; Morisette, Jeffrey T.; Vermote, Eric F.; Roy, David P.; Wolfe, Robert E.; Friedl, Mark A.; Running, Steven W.; Votava, Petr; El-Saleous, Nazmi; Devadiga, Sadashiva; Su, Yin; Salomonson, Vincent V.

2007-01-01

Despite early speculation to the contrary, all tropical forests studied to date display seasonal variations in the presence of new leaves, flowers, and fruits. Past studies were focused on the timing of phenological events and their cues but not on the accompanying changes in leaf area that regulate vegetation–atmosphere exchanges of energy, momentum, and mass. Here we report, from analysis of 5 years of recent satellite data, seasonal swings in green leaf area of ≈25% in a majority of the Amazon rainforests. This seasonal cycle is timed to the seasonality of solar radiation in a manner that is suggestive of anticipatory and opportunistic patterns of net leaf flushing during the early to mid part of the light-rich dry season and net leaf abscission during the cloudy wet season. These seasonal swings in leaf area may be critical to initiation of the transition from dry to wet season, seasonal carbon balance between photosynthetic gains and respiratory losses, and litterfall nutrient cycling in moist tropical forests. PMID:17360360

Algorithm for retrieving vegetative canopy and leaf parameters from multi- and hyperspectral imagery

NASA Astrophysics Data System (ADS)

Borel, Christoph

2009-05-01

In recent years hyper-spectral data has been used to retrieve information about vegetative canopies such as leaf area index and canopy water content. For the environmental scientist these two parameters are valuable, but there is potentially more information to be gained as high spatial resolution data becomes available. We developed an Amoeba (Nelder-Mead or Simplex) based program to invert a vegetative canopy radiosity model coupled with a leaf (PROSPECT5) reflectance model and modeled for the background reflectance (e.g. soil, water, leaf litter) to a measured reflectance spectrum. The PROSPECT5 leaf model has five parameters: leaf structure parameter Nstru, chlorophyll a+b concentration Cab, carotenoids content Car, equivalent water thickness Cw and dry matter content Cm. The canopy model has two parameters: total leaf area index (LAI) and number of layers. The background reflectance model is either a single reflectance spectrum from a spectral library() derived from a bare area pixel on an image or a linear mixture of soil spectra. We summarize the radiosity model of a layered canopy and give references to the leaf/needle models. The method is then tested on simulated and measured data. We investigate the uniqueness, limitations and accuracy of the retrieved parameters on canopy parameters (low, medium and high leaf area index) spectral resolution (32 to 211 band hyperspectral), sensor noise and initial conditions.

Can biomass responses to warming at plant to ecosystem levels be predicted by leaf-level responses?

NASA Astrophysics Data System (ADS)

Xia, J.; Shao, J.; Zhou, X.; Yan, W.; Lu, M.

2015-12-01

Global warming has the profound impacts on terrestrial C processes from leaf to ecosystem scales, potentially feeding back to climate dynamics. Although numerous studies had investigated the effects of warming on C processes from leaf to plant and ecosystem levels, how leaf-level responses to warming scale up to biomass responses at plant, population, and community levels are largely unknown. In this study, we compiled a dataset from 468 papers at 300 experimental sites and synthesized the warming effects on leaf-level parameters, and plant, population and ecosystem biomass. Our results showed that responses of plant biomass to warming mainly resulted from the changed leaf area rather than the altered photosynthetic capacity. The response of ecosystem biomass to warming was weaker than those of leaf area and plant biomass. However, the scaling functions from responses of leaf area to plant biomass to warming were different in diverse forest types, but functions were similar in non-forested biomes. In addition, it is challenging to scale the biomass responses from plant up to ecosystem. These results indicated that leaf area might be the appropriate index for plant biomass response to warming, and the interspecific competition might hamper the scaling of the warming effects on plant and ecosystem levels, suggesting that the acclimation capacity of plant community should be incorporated into land surface models to improve the prediction of climate-C cycle feedback.

Potassium Starvation Limits Soybean Growth More than the Photosynthetic Processes across CO2 Levels

PubMed Central

Singh, Shardendu K.; Reddy, Vangimalla R.

2017-01-01

Elevated carbon dioxide (eCO2) often enhances plant photosynthesis, growth, and productivity. However, under nutrient-limited conditions the beneficial effects of high CO2 are often diminished. To evaluate the combined effects of potassium (K) deficiency and eCO2 on soybean photosynthesis, growth, biomass partitioning, and yields, plants were grown under controlled environment conditions with an adequate (control, 5.0 mM) and two deficient (0.50 and 0.02 mM) levels of K under ambient CO2 (aCO2; 400 μmol mol−1) and eCO2 (800 μmol mol−1). Results showed that K deficiency limited soybean growth traits more than photosynthetic processes. An ~54% reduction in leaf K concentration under 0.5 mM K vs. the control caused about 45% less leaf area, biomass, and yield without decreasing photosynthetic rate (Pnet). In fact, the steady photochemical quenching, efficiency, and quantum yield of photosystem II, chlorophyll concentration (TChl), and stomatal conductance under 0.5 mM K supported the stable Pnet. Biomass decline was primarily attributed to the reduced plant size and leaf area, and decreased pod numbers and seed yield in K-deficient plants. Under severe K deficiency (0.02 mM K), photosynthetic processes declined concomitantly with growth and productivity. Increased specific leaf weight, biomass partitioning to the leaves, decreased photochemical quenching and TChl, and smaller plant size to reduce the nutrient demands appeared to be the means by which plants adjusted to the severe K starvation. Increased K utilization efficiency indicated the ability of K-deficient plants to better utilize the tissue-available K for biomass accumulation, except under severe K starvation. The enhancement of soybean growth by eCO2 was dependent on the levels of K, leading to a K × CO2 interaction for traits such as leaf area, biomass, and yield. A lack of eCO2-mediated growth and photosynthesis stimulation under severe K deficiency underscored the importance of optimum K fertilization for maximum crop productivity under eCO2. Thus, eCO2 compensated, at least partially, for the reduced soybean growth and seed yield under 0.5 mM K supply, but severe K deficiency completely suppressed the eCO2-enhanced seed yield. PMID:28642785

WE-AB-209-10: Optimizing the Delivery of Sequential Fluence Maps for Efficient VMAT Delivery

DOE Office of Scientific and Technical Information (OSTI.GOV)

Craft, D; Balvert, M

2016-06-15

Purpose: To develop an optimization model and solution approach for computing MLC leaf trajectories and dose rates for high quality matching of a set of optimized fluence maps to be delivered sequentially around a patient in a VMAT treatment. Methods: We formulate the fluence map matching problem as a nonlinear optimization problem where time is discretized but dose rates and leaf positions are continuous variables. For a given allotted time, which is allocated across the fluence maps based on the complexity of each fluence map, the optimization problem searches for the best leaf trajectories and dose rates such that themore » original fluence maps are closely recreated. Constraints include maximum leaf speed, maximum dose rate, and leaf collision avoidance, as well as the constraint that the ending leaf positions for one map are the starting leaf positions for the next map. The resulting model is non-convex but smooth, and therefore we solve it by local searches from a variety of starting positions. We improve solution time by a custom decomposition approach which allows us to decouple the rows of the fluence maps and solve each leaf pair individually. This decomposition also makes the problem easily parallelized. Results: We demonstrate method on a prostate case and a head-and-neck case and show that one can recreate fluence maps to high degree of fidelity in modest total delivery time (minutes). Conclusion: We present a VMAT sequencing method that reproduces optimal fluence maps by searching over a vast number of possible leaf trajectories. By varying the total allotted time given, this approach is the first of its kind to allow users to produce VMAT solutions that span the range of wide-field coarse VMAT deliveries to narrow-field high-MU sliding window-like approaches.« less

Effects of incandescent radiation on photosynthesis, growth rate and yield of 'Waldmann's Green' leaf lettuce

NASA Technical Reports Server (NTRS)

Knight, Sharon L.; Mitchell, Cary A.

1988-01-01

Effects of different ratios of incandescent (ln) to fluorescent (Fl) radiation were tested on growth of 'Waldmann's Green' leaf lettuce in a controlled environment. After 4 days of treatment, dry weight, leaf area, relative growth rate (RGR), net assimilation rate (NAR), leaf area ratio (LAR) and photosynthetic rate (Pn) were greater for plants grown at 84 rather than 16 percent of total irradiance (82 W/sq m) from ln lamps. Although leaf dry weight and area were 12-17 percent greater at 84 percent ln after the first 8 days of treatment, there were no differences in RGR or Pn between treatments during the last 4 days. If 84 percent ln was compared with 50 percent ln, all cumulative growth parameters, RGR, NAR and Pn were greater for 84 percent ln during the first 4 days of treatment. However, during the second 4 days, RGR was greater for the 50 percent ln treatment, resulting in no net difference in leaf dry weight or area between treatments. Shifting from 84 to 50 percent ln radiation between the first and second 4 days of treatment increased plant dry weight, leaf area, RGR and NAR relative to those under 84 percent ln for 8 days continuously.

Comparative evaluation of successive extracts of leaf and stem bark of Albizzia lebbeck for mast cell stabilization activity.

PubMed

Shashidhara, S; Bhandarkar, Anant V; Deepak, M

2008-06-01

Successive chloroform, methanol and water extracts of bark and leaves of Albizzia lebbeck were tested for its in vitro mast cell stabilizing effect against compound 48/80. Methanolic extract of leaf and methanolic and water extracts of bark have shown maximum activity comparable to that of disodium chromoglycate.

Photosynthetic leaf area modulates tiller bud outgrowth in sorghum: Bud outgrowth is sensitive to leaf area

DOE PAGES

Kebrom, Tesfamichael H.; Mullet, John E.

2014-12-12

Shoot branches or tillers develop from axillary buds. The dormancy versus outgrowth fates of buds depends on genetic, environmental and hormonal signals. Defoliation inhibits bud outgrowth indicating the role of leaf-derived metabolic factors such as sucrose in bud outgrowth. In this study, the sensitivity of bud outgrowth to selective defoliation was investigated. At 6 d after planting (6 DAP), the first two leaves of sorghum were fully expanded and the third was partially emerged. Therefore, the leaves were selectively defoliated at 6 DAP and the length of the bud in the first leaf axil was measured at 8 DAP. Budmore » outgrowth was inhibited by defoliation of only 2 cm from the tip of the second leaf blade. The expression of dormancy and sucrose-starvation marker genes was up-regulated and cell cycle and sucrose-inducible genes was down-regulated during the first 24 h postdefoliation of the second leaf.At 48 h, the expression of these genes was similar to controls as the defoliated plant recovers. Our results demonstrate that small changes in photosynthetic leaf area affect the propensity of tiller buds for outgrowth. Therefore, variation in leaf area and photosynthetic activity should be included when integrating sucrose into models of shoot branching.« less

Seedlings of temperate rainforest conifer and angiosperm trees differ in leaf area display.

PubMed

Lusk, Christopher H; Pérez-Millaqueo, Manuel M; Saldaña, Alfredo; Burns, Bruce R; Laughlin, Daniel C; Falster, Daniel S

2012-07-01

The contemporary relegation of conifers mainly to cold or infertile sites has been ascribed to low competitive ability, as a result of the hydraulic inefficiency of tracheids and their seedlings' initial dependence on small foliage areas. Here it is hypothesized that, in temperate rainforests, the larger leaves of angiosperms also reduce self-shading and thus enable display of larger effective foliage areas than the numerous small leaves of conifers. This hypothesis was tested using 3-D modelling of plant architecture and structural equation modelling to compare self-shading and light interception potential of seedlings of six conifers and 12 angiosperm trees from temperate rainforests. The ratio of displayed leaf area to plant mass (LAR(d)) was used to indicate plant light interception potential: LAR(d) is the product of specific leaf area, leaf mass fraction, self-shading and leaf angle. Angiosperm seedlings self-shaded less than conifers, mainly because of differences in leaf number (more than leaf size), and on average their LAR(d) was about twice that of conifers. Although specific leaf area was the most pervasive influence on LAR(d), differences in self-shading also significantly influenced LAR(d) of large seedlings. The ability to deploy foliage in relatively few, large leaves is advantageous in minimizing self-shading and enhancing seedling light interception potential per unit of plant biomass. This study adds significantly to evidence that vegetative traits may be at least as important as reproductive innovations in explaining the success of angiosperms in productive environments where vegetation is structured by light competition.

Seedlings of temperate rainforest conifer and angiosperm trees differ in leaf area display

PubMed Central

Lusk, Christopher H.; Pérez-Millaqueo, Manuel M.; Saldaña, Alfredo; Burns, Bruce R.; Laughlin, Daniel C.; Falster, Daniel S.

2012-01-01

Background and Aims The contemporary relegation of conifers mainly to cold or infertile sites has been ascribed to low competitive ability, as a result of the hydraulic inefficiency of tracheids and their seedlings' initial dependence on small foliage areas. Here it is hypothesized that, in temperate rainforests, the larger leaves of angiosperms also reduce self-shading and thus enable display of larger effective foliage areas than the numerous small leaves of conifers. Methods This hypothesis was tested using 3-D modelling of plant architecture and structural equation modelling to compare self-shading and light interception potential of seedlings of six conifers and 12 angiosperm trees from temperate rainforests. The ratio of displayed leaf area to plant mass (LARd) was used to indicate plant light interception potential: LARd is the product of specific leaf area, leaf mass fraction, self-shading and leaf angle. Results Angiosperm seedlings self-shaded less than conifers, mainly because of differences in leaf number (more than leaf size), and on average their LARd was about twice that of conifers. Although specific leaf area was the most pervasive influence on LARd, differences in self-shading also significantly influenced LARd of large seedlings. Conclusions The ability to deploy foliage in relatively few, large leaves is advantageous in minimizing self-shading and enhancing seedling light interception potential per unit of plant biomass. This study adds significantly to evidence that vegetative traits may be at least as important as reproductive innovations in explaining the success of angiosperms in productive environments where vegetation is structured by light competition. PMID:22585929

[Photosynthetic gas exchange and water utilization of flag leaf of spring wheat with bunch sowing and field plastic mulching below soil on semi-arid rain-fed area.

PubMed

Yang, Wen Xiong; Liu, Na; Liu, Xiao Hua; Zhang, Xue Ting; Wang, Shi Hong; Yuan, Jun Xiu; Zhang, Xu Cheng

2016-07-01

Based on the field experiment which was conducted in Dingxi County of Gansu Province, and involved in the three treatments: (1) plastic mulching on entire land with soil coverage and bunching (PMS), (2) plastic mulching on entire land and bunching (PM), and (3) direct bunching without mulching (CK). The parameters of SPAD values, chlorophyll fluorescence parameters, photosynthetic gas exchange parameters, as well as leaf area index (LAI), yield, evapotranspiration, and water use efficiency in flag leaves of spring wheat were recorded and analyzed from 2012 to 2013 continuously. The results showed that SPAD values of wheat flag leaves increased in PMS by 10.0%-21.5% and 3.2%-21.6% compared to PM and CK in post-flowering stage, respectively. The maximum photochemical efficiency (F v /F m ) , actual photochemical efficiency (Φ PS 2 ) of photosystem 2 (PS2), and photochemical quenching coefficient (q P ) of PMS were higher than those of PM and CK, the maximum increment values were 6.1%, 9.6% and 30.9% as compared with PM, and significant differences were observed in filling stage (P＜0.05). The values of q N in PMS were lowest among the three treatments, and it decreased significantly by 23.8% and 15.4% in heading stage in 2012 and 2013 respectively, as compared with PM. The stoma conductance (g s ) of wheat flag leaves in PMS was higher than that of PM and CK, with significant difference being observed in filling stage, and it increased by 17.1% and 21.1% in 2012 and 2013 respectively, as compared with PM. The transpiration rate (T r ), net photosynthetic rate (P n ), and leaf instantaneous water use efficiency (WUE i ) except heading stage in 2013 of PMS increased by 5.4%-16.7%, 11.2%-23.7%, and 5.6%-7.2%, respectively, as compared with PM, and significant difference of WUE i was observed in flowering stage in 2012. The leaf area index (LAI) of PMS was higher than that of PM and CK, especially, it differed significantly in seasonal drought of 2013. Consequently, the PMS increased the SPAD values in flag leaves of spring wheat, and the capacity of flag leaves for photo energy assimilation and photosynthetic gas exchange were enhanced, caused more photosynthetic energy flowing into photochemical process, as well as decreased the heat dissipation, resulted in the increment of P n and WUE i . Based on the higher P n and LAI, the yield and WUE of PMS increased.

First direct landscape-scale measurement of tropical rain forest Leaf Area Index, a key driver of global primary productivity

Treesearch

David B. Clark; Paulo C. Olivas; Steven F. Oberbauer; Deborah A. Clark; Michael G. Ryan

2008-01-01

Leaf Area Index (leaf area per unit ground area, LAI) is a key driver of forest productivity but has never previously been measured directly at the landscape scale in tropical rain forest (TRF). We used a modular tower and stratified random sampling to harvest all foliage from forest floor to canopy top in 55 vertical transects (4.6 m2) across 500 ha of old growth in...

Internal coordination between hydraulics and stomatal control in leaves.

PubMed

Brodribb, Tim J; Jordan, Gregory J

2008-11-01

The stomatal response to changing leaf-atmospheric vapour pressure gradient (D(l)) is a crucial yet enigmatic process that defines the daily course of leaf gas exchange. Changes in the hydration of epidermal cells are thought to drive this response, mediated by the transpiration rate and hydraulic conductance of the leaf. Here, we examine whether species-specific variation in the sensitivity of leaves to perturbation of D(l) is related to the efficiency of water transport in the leaf (leaf hydraulic conductivity, K(leaf)). We found good correlation between maximum liquid (K(leaf)) and gas phase conductances (g(max)) in leaves, but there was no direct correlation between normalized D(l) sensitivity and K(leaf). The impact of K(leaf) on D(l) sensitivity in our diverse sample of eight species was important only after accounting for the strong relationship between K(leaf) and g(max). Thus, the ratio of g(max)/K(leaf) was strongly correlated with stomatal sensitivity to D(l). This ratio is an index of the degree of hydraulic buffering of the stomata against changes in D(l), and species with high g(max) relative to K(leaf) were the most sensitive to D(l) perturbation. Despite the potentially high adaptive significance of this phenomenon, we found no significant phylogenetic or ecological trend in our species.

The effect of leaf size on the microwave backscattering by corn

NASA Technical Reports Server (NTRS)

Paris, J. F.

1986-01-01

Attema and Ulaby (1978) proposed the cloud model to predict the microwave backscattering properties of vegetation. This paper describes a modification in which the biophysical properties and microwave properties of vegetation are related at the level of the individual scatterer (e.g., the leaf or the stalk) rather than at the level of the aggregated canopy (e.g., the green leaf area index). Assuming that the extinction cross section of an average leaf was proportional to its water content, that a power law relationship existed between the backscattering cross section of an average green corn leaf and its area, and that the backscattering coefficient of the surface was a linear function of its volumetric soil moisture content, it is found that the explicit inclusion of the effects of corn leaf size in the model led to an excellent fit between the observed and predicted backscattering coefficients. Also, an excellent power law relationship existed between the backscattering cross section of a corn leaf and its area.

Determination of coefficient defining leaf area development in different genotypes, plant types and planting densities in peanut (Arachis hypogeae L.).

PubMed

Halilou, Oumarou; Hissene, Halime Mahamat; Clavijo Michelangeli, José A; Hamidou, Falalou; Sinclair, Thomas R; Soltani, Afshin; Mahamane, Saadou; Vadez, Vincent

2016-12-01

Rapid leaf area development may be attractive under a number of cropping conditions to enhance the vigor of crop establishment and allow rapid canopy closure for maximizing light interception and shading of weed competitors. This study was undertaken to determine (1) if parameters describing leaf area development varied among ten peanut ( Arachis hypogeae L.) genotypes grown in field and pot experiments, (2) if these parameters were affected by the planting density, and (3) if these parameters varied between Spanish and Virginia genotypes. Leaf area development was described by two steps: prediction of main stem number of nodes based on phyllochron development and plant leaf area dependent based on main stem node number. There was no genetic variation in the phyllochron measured in the field. However, the phyllochron was much longer for plants grown in pots as compared to the field-grown plants. These results indicated a negative aspect of growing peanut plants in the pots used in this experiment. In contrast to phyllochron, there was no difference in the relationship between plant leaf area and main stem node number between the pot and field experiments. However, there was genetic variation in both the pot and field experiments in the exponential coefficient (PLAPOW) of the power function used to describe leaf area development from node number. This genetic variation was confirmed in another experiment with a larger number of genotypes, although possible G × E interaction for the PLAPOW was found. Sowing density did not affect the power function relating leaf area to main stem node number. There was also no difference in the power function coefficient between Spanish and Virginia genotypes. SSM (Simple Simulation model) reliably predicted leaf canopy development in groundnut. Indeed the leaf area showed a close agreement between predicted and observed values up to 60000 cm 2  m -2 . The slightly higher prediction in India and slightly lower prediction in Niger reflected GxE interactions. Until more understanding is obtained on the possible GxE interaction effects on the canopy development, a generic PLAPOW value of 2.71, no correction for sowing density, and a phyllochron on 53 °C could be used to model canopy development in peanut.

78 FR 72579 - Revisions to the Arizona State Implementation Plan, Maricopa County Area

Federal Register 2010, 2011, 2012, 2013, 2014

2013-12-03

....01 Leaf Blower Use Restrictions 07/02/07 05/25/12 and Training; Leaf Blowers Equipment Sellers... recommend stronger control of emissions from leaf blowers, expanding leaf blowers requirements beyond county employees, control of leaf blowers in vacuum mode, control of leaf blowers on permitted sites, and greater...

A trait-based approach to community assembly: partitioning of species trait values into within- and among-community components.

PubMed

Ackerly, D D; Cornwell, W K

2007-02-01

Plant functional traits vary both along environmental gradients and among species occupying similar conditions, creating a challenge for the synthesis of functional and community ecology. We present a trait-based approach that provides an additive decomposition of species' trait values into alpha and beta components: beta values refer to a species' position along a gradient defined by community-level mean trait values; alpha values are the difference between a species' trait values and the mean of co-occurring taxa. In woody plant communities of coastal California, beta trait values for specific leaf area, leaf size, wood density and maximum height all covary strongly, reflecting species distributions across a gradient of soil moisture availability. Alpha values, on the other hand, are generally not significantly correlated, suggesting several independent axes of differentiation within communities. This trait-based framework provides a novel approach to integrate functional ecology and gradient analysis with community ecology and coexistence theory.

Leaf Mass Area, Leaf Carbon and Nitrogen Content, Barrow, Alaska, 2012-2016

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rogers, Alistair; Ely, Kim; Serbin, Shawn

Carbon, Nitrogen and Leaf Mass Area of leaves sampled from the Barrow Environmental Observatory, Barrow, Alaska. Species measured; Arctophila fulva, Arctagrostis latifolia, Carex aquatilis, Dupontia fisheri, Eriophorum angustifolium, Petasites frigidus, Salix pulchra, Vaccinium vitis-idaea, Salix rotundifolia, Luzula arctica, Saxifraga punctata and Potentilla hyparctica.

Convergent production and tolerance among 107 woody species and divergent production between shrubs and trees.

PubMed

He, Wei-Ming; Sun, Zhen-Kai

2016-02-08

Green leaves face two fundamental challenges (i.e., carbon fixation and stress tolerance) during their lifespan. However, the relationships between leaf production potential and leaf tolerance potential have not been explicitly tested with a broad range of plant species in the same environment. To do so, we conducted a field investigation based on 107 woody plants grown in a common garden and complementary laboratory measurements. The values, as measured by a chlorophyll meter, were significantly related to the direct measurements of chlorophyll content on a leaf area basis. Area-based chlorophyll content was positively correlated with root surface area, whole-plant biomass, leaf mass per area (LMA), and force to punch. Additionally, LMA had a positive correlation with force to punch. Shrubs had a higher leaf chlorophyll content than trees; however, shrubs and trees exhibited a similar leaf lifespan, force to punch, and LMA. These findings suggest that the production potential of leaves and their tolerance to stresses may be convergent in woody species and that the leaf production potential may differ between shrubs and trees. This study highlights the possibility that functional convergence and divergence might be linked to long-term selection pressures and genetic constraints.

Convergent production and tolerance among 107 woody species and divergent production between shrubs and trees

PubMed Central

He, Wei-Ming; Sun, Zhen-Kai

2016-01-01

Green leaves face two fundamental challenges (i.e., carbon fixation and stress tolerance) during their lifespan. However, the relationships between leaf production potential and leaf tolerance potential have not been explicitly tested with a broad range of plant species in the same environment. To do so, we conducted a field investigation based on 107 woody plants grown in a common garden and complementary laboratory measurements. The values, as measured by a chlorophyll meter, were significantly related to the direct measurements of chlorophyll content on a leaf area basis. Area-based chlorophyll content was positively correlated with root surface area, whole-plant biomass, leaf mass per area (LMA), and force to punch. Additionally, LMA had a positive correlation with force to punch. Shrubs had a higher leaf chlorophyll content than trees; however, shrubs and trees exhibited a similar leaf lifespan, force to punch, and LMA. These findings suggest that the production potential of leaves and their tolerance to stresses may be convergent in woody species and that the leaf production potential may differ between shrubs and trees. This study highlights the possibility that functional convergence and divergence might be linked to long-term selection pressures and genetic constraints. PMID:26854019

How vertical patterns in leaf traits shift seasonally and the implications for modeling canopy photosynthesis in a temperate deciduous forest.

PubMed

Coble, Adam P; VanderWall, Brittany; Mau, Alida; Cavaleri, Molly A

2016-09-01

Leaf functional traits are used in modeling forest canopy photosynthesis (Ac) due to strong correlations between photosynthetic capacity, leaf mass per area (LMA) and leaf nitrogen per area (Narea). Vertical distributions of these traits may change over time in temperate deciduous forests as a result of acclimation to light, which may result in seasonal changes in Ac To assess both spatial and temporal variations in key traits, we measured vertical profiles of Narea and LMA from leaf expansion through leaf senescence in a sugar maple (Acer saccharum Marshall) forest. To investigate mechanisms behind coordinated changes in leaf morphology and function, we also measured vertical variation in leaf carbon isotope composition (δ(13)C), predawn turgor pressure, leaf water potential and osmotic potential. Finally, we assessed potential biases in Ac estimations by parameterizing models with and without vertical and seasonal Narea variations following leaf expansion. Our data are consistent with the hypothesis that hydrostatic constraints on leaf morphology drive the vertical increase in LMA with height early in the growing season; however, LMA in the upper canopy continued to increase over time during light acclimation, indicating that light is primarily driving gradients in LMA later in the growing season. Models with no seasonal variation in Narea overestimated Ac by up to 11% early in the growing season, while models with no vertical variation in Narea overestimated Ac by up to 60% throughout the season. According to the multilayer model, the upper 25% of leaf area contributed to over 50% of Ac, but when gradients of intercellular CO2, as estimated from δ(13)C, were accounted for, the upper 25% of leaf area contributed to 26% of total Ac Our results suggest that ignoring vertical variation of key traits can lead to considerable overestimation of Ac. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Impact of elevated temperatures on specific leaf weight, stomatal density, photosynthesis and chlorophyll fluorescence in soybean.

PubMed

Jumrani, Kanchan; Bhatia, Virender Singh; Pandey, Govind Prakash

2017-03-01

High-temperature stress is a major environmental stress and there are limited studies elucidating its impact on soybean (Glycine max L. Merril.). The objectives of present study were to quantify the effect of high temperature on changes in leaf thickness, number of stomata on adaxial and abaxial leaf surfaces, gas exchange, chlorophyll fluorescence parameters and seed yield in soybean. Twelve soybean genotypes were grown at day/night temperatures of 30/22, 34/24, 38/26 and 42/28 °C with an average temperature of 26, 29, 32 and 35 °C, respectively, under greenhouse conditions. One set was also grown under ambient temperature conditions where crop season average maximum, minimum and mean temperatures were 28.0, 22.4 and 25.2 °C, respectively. Significant negative effect of temperature was observed on specific leaf weight (SLW) and leaf thickness. Rate of photosynthesis, stomatal conductance and water use efficiency declined as the growing temperatures increased; whereas, intercellular CO 2 and transpiration rate were increased. With the increase in temperature chlorophyll fluorescence parameters such as Fv/Fm, qP and PhiPSII declined while there was increase in qN. Number of stomata on both abaxial and adaxial surface of leaf increased significantly with increase in temperatures. The rate of photosynthesis, PhiPSII, qP and SPAD values were positively associated with leaf thickness and SLW. This indicated that reduction in photosynthesis and associated parameters appears to be due to structural changes observed at higher temperatures. The average seed yield was maximum (13.2 g/pl) in plants grown under ambient temperature condition and declined by 8, 14, 51 and 65% as the temperature was increased to 30/22, 34/24, 38/26 and 42/28 °C, respectively.

Do the rich always become richer? Characterizing the leaf physiological response of the high-yielding rice cultivar Takanari to free-air CO2 enrichment.

PubMed

Chen, Charles P; Sakai, Hidemitsu; Tokida, Takeshi; Usui, Yasuhiro; Nakamura, Hirofumi; Hasegawa, Toshihiro

2014-02-01

The development of crops which are well suited to growth under future environmental conditions such as higher atmospheric CO2 concentrations ([CO2]) is essential to meeting the challenge of ensuring food security in the face of the growing human population and changing climate. A high-yielding indica rice variety (Oryza sativa L. cv. Takanari) has been recently identified as a potential candidate for such breeding, due to its high productivity in present [CO2]. To test if it could further increase its productivity under elevated [CO2] (eCO2), Takanari was grown in the paddy field under season-long free-air CO2 enrichment (FACE, approximately 200 µmol mol(-1) above ambient [CO2]) and its leaf physiology was compared with the representative japonica variety 'Koshihikari'. Takanari showed consistently higher midday photosynthesis and stomatal conductance than Koshihikari under both ambient and FACE growth conditions over 2 years. Maximum ribulose-1,5-bisphosphate carboxylation and electron transport rates were higher for Takanari at the mid-grain filling stage in both years. Mesophyll conductance was higher in Takanari than in Koshihikari at the late grain-filling stage. In contrast to Koshihikari, Takanari grown under FACE conditions showed no decrease in total leaf nitrogen on an area basis relative to ambient-grown plants. Chl content was higher in Takanari than in Koshihikari at the same leaf nitrogen level. These results indicate that Takanari maintains its superiority over Koshihikari in regards to its leaf-level productivity when grown in elevated [CO2] and it may be a valuable resource for rice breeding programs which seek to increase crop productivity under current and future [CO2].

Wheat plant selection for high yields entailed improvement of leaf anatomical and biochemical traits including tolerance to non-optimal temperature conditions.

PubMed

Brestic, Marian; Zivcak, Marek; Hauptvogel, Pavol; Misheva, Svetlana; Kocheva, Konstantina; Yang, Xinghong; Li, Xiangnan; Allakhverdiev, Suleyman I

2018-05-01

Assessment of photosynthetic traits and temperature tolerance was performed on field-grown modern genotype (MG), and the local landrace (LR) of wheat (Triticum aestivum L.) as well as the wild relative species (Aegilops cylindrica Host.). The comparison was based on measurements of the gas exchange (A/c i , light and temperature response curves), slow and fast chlorophyll fluorescence kinetics, and some growth and leaf parameters. In MG, we observed the highest CO 2 assimilation rate [Formula: see text] electron transport rate (J max ) and maximum carboxylation rate [Formula: see text]. The Aegilops leaves had substantially lower values of all photosynthetic parameters; this fact correlated with its lower biomass production. The mesophyll conductance was almost the same in Aegilops and MG, despite the significant differences in leaf phenotype. In contrary, in LR with a higher dry mass per leaf area, the half mesophyll conductance (g m ) values indicated more limited CO 2 diffusion. In Aegilops, we found much lower carboxylation capacity; this can be attributed mainly to thin leaves and lower Rubisco activity. The difference in CO 2 assimilation rate between MG and others was diminished because of its higher mitochondrial respiration activity indicating more intense metabolism. Assessment of temperature response showed lower temperature optimum and a narrow ecological valence (i.e., the range determining the tolerance limits of a species to an environmental factor) in Aegilops. In addition, analysis of photosynthetic thermostability identified the LR as the most sensitive. Our results support the idea that the selection for high yields was accompanied by the increase of photosynthetic productivity through unintentional improvement of leaf anatomical and biochemical traits including tolerance to non-optimal temperature conditions.

Do the Rich Always Become Richer? Characterizing the Leaf Physiological Response of the High-Yielding Rice Cultivar Takanari to Free-Air CO2 Enrichment

PubMed Central

Chen, Charles P.; Sakai, Hidemitsu; Tokida, Takeshi; Usui, Yasuhiro; Nakamura, Hirofumi; Hasegawa, Toshihiro

2014-01-01

The development of crops which are well suited to growth under future environmental conditions such as higher atmospheric CO2 concentrations ([CO2]) is essential to meeting the challenge of ensuring food security in the face of the growing human population and changing climate. A high-yielding indica rice variety (Oryza sativa L. cv. Takanari) has been recently identified as a potential candidate for such breeding, due to its high productivity in present [CO2]. To test if it could further increase its productivity under elevated [CO2] (eCO2), Takanari was grown in the paddy field under season-long free-air CO2 enrichment (FACE, approximately 200 µmol mol−1 above ambient [CO2]) and its leaf physiology was compared with the representative japonica variety ‘Koshihikari’. Takanari showed consistently higher midday photosynthesis and stomatal conductance than Koshihikari under both ambient and FACE growth conditions over 2 years. Maximum ribulose-1,5-bisphosphate carboxylation and electron transport rates were higher for Takanari at the mid-grain filling stage in both years. Mesophyll conductance was higher in Takanari than in Koshihikari at the late grain-filling stage. In contrast to Koshihikari, Takanari grown under FACE conditions showed no decrease in total leaf nitrogen on an area basis relative to ambient-grown plants. Chl content was higher in Takanari than in Koshihikari at the same leaf nitrogen level. These results indicate that Takanari maintains its superiority over Koshihikari in regards to its leaf-level productivity when grown in elevated [CO2] and it may be a valuable resource for rice breeding programs which seek to increase crop productivity under current and future [CO2]. PMID:24443497

Observing Spring and Fall Phenology in a Deciduous Forest with Aerial Drone Imagery.

PubMed

Klosterman, Stephen; Richardson, Andrew D

2017-12-08

Plant phenology is a sensitive indicator of the effects of global change on terrestrial ecosystems and controls the timing of key ecosystem functions including photosynthesis and transpiration. Aerial drone imagery and photogrammetric techniques promise to advance the study of phenology by enabling the creation of distortion-free orthomosaics of plant canopies at the landscape scale, but with branch-level image resolution. The main goal of this study is to determine the leaf life cycle events corresponding to phenological metrics derived from automated analyses based on color indices calculated from drone imagery. For an oak-dominated, temperate deciduous forest in the northeastern USA, we find that plant area index (PAI) correlates with a canopy greenness index during spring green-up, and a canopy redness index during autumn senescence. Additionally, greenness and redness metrics are significantly correlated with the timing of budburst and leaf expansion on individual trees in spring. However, we note that the specific color index for individual trees must be carefully chosen if new foliage in spring appears red, rather than green-which we observed for some oak trees. In autumn, both decreasing greenness and increasing redness correlate with leaf senescence. Maximum redness indicates the beginning of leaf fall, and the progression of leaf fall correlates with decreasing redness. We also find that cooler air temperature microclimates near a forest edge bordering a wetland advance the onset of senescence. These results demonstrate the use of drones for characterizing the organismic-level variability of phenology in a forested landscape and advance our understanding of which phenophase transitions correspond to color-based metrics derived from digital image analysis.

Observing Spring and Fall Phenology in a Deciduous Forest with Aerial Drone Imagery

PubMed Central

Richardson, Andrew D.

2017-01-01

Plant phenology is a sensitive indicator of the effects of global change on terrestrial ecosystems and controls the timing of key ecosystem functions including photosynthesis and transpiration. Aerial drone imagery and photogrammetric techniques promise to advance the study of phenology by enabling the creation of distortion-free orthomosaics of plant canopies at the landscape scale, but with branch-level image resolution. The main goal of this study is to determine the leaf life cycle events corresponding to phenological metrics derived from automated analyses based on color indices calculated from drone imagery. For an oak-dominated, temperate deciduous forest in the northeastern USA, we find that plant area index (PAI) correlates with a canopy greenness index during spring green-up, and a canopy redness index during autumn senescence. Additionally, greenness and redness metrics are significantly correlated with the timing of budburst and leaf expansion on individual trees in spring. However, we note that the specific color index for individual trees must be carefully chosen if new foliage in spring appears red, rather than green—which we observed for some oak trees. In autumn, both decreasing greenness and increasing redness correlate with leaf senescence. Maximum redness indicates the beginning of leaf fall, and the progression of leaf fall correlates with decreasing redness. We also find that cooler air temperature microclimates near a forest edge bordering a wetland advance the onset of senescence. These results demonstrate the use of drones for characterizing the organismic-level variability of phenology in a forested landscape and advance our understanding of which phenophase transitions correspond to color-based metrics derived from digital image analysis. PMID:29292742

Importance of the method of leaf area measurement to the interpretation of gas exchange of complex shoots

Treesearch

W. K. Smith; A. W. Schoettle; M. Cui

1991-01-01

Net CO(2) uptake in full sunlight, total leaf area (TLA), projected leaf area of detached leaves (PLA), and the silhouette area of attached leaves in their natural orientation to the sun at midday on June 1 (SLA) were measured for sun shoots of six conifer species. Among species, TLA/SLA ranged between 5.2 and 10.0 (x bar = 7.3), TLA/PLA ranged between 2.5 and 2.9 (x...

Leaf area index, biomass carbon and growth rate of radiata pine genetic types and relationships with LiDAR

Treesearch

Peter N. Beets; Stephen Reutebuch; Mark O. Kimberley; Graeme R. Oliver; Stephen H. Pearce; Robert J. McGaughey

2011-01-01

Relationships between discrete-return light detection and ranging (LiDAR) data and radiata pine leaf area index (LAI), stem volume, above ground carbon, and carbon sequestration were developed using 10 plots with directly measured biomass and leaf area data, and 36 plots with modelled carbon data. The plots included a range of genetic types established on north- and...

Estimating individual tree leaf area in loblolly pine plantations using LiDAR-derived measurments of height and crown dimensions

Treesearch

Scott D. Roberts; Thomas J. Dean; David L. Evans; John W. McCombs; Richard L. Harrington; Partick A. Glass

2005-01-01

Accurate estimates of leaf area index (LAI) could provide useful information to forest managers, but due to difficulties in measurement, leaf area is rarely used in decision-making. A reliable approach to remotely estimating LA1 would greatly facilitate its use in forest management. This study investigated the potential for using small-footprint iDAR, a laser-based...

Viewing forests from below: fine root mass declines relative to leaf area in aging lodgepole pine stands.

PubMed

Schoonmaker, A S; Lieffers, V J; Landhäusser, S M

2016-07-01

In the continued quest to explain the decline in productivity and vigor with aging forest stands, the most poorly studied area relates to root system change in time. This paper measures the wood production, root and leaf area (and mass) in a chronosequence of fire-origin lodgepole pine (Pinus contorta Loudon) stands consisting of four age classes (12, 21, 53, and ≥100 years), each replicated ~ five times. Wood productivity was greatest in the 53-year-old stands and then declined in the ≥100-year-old stands. Growth efficiency, the quantity of wood produced per unit leaf mass, steadily declined with age. Leaf mass and fine root mass plateaued between the 53- and ≥100-year-old stands, but leaf area index actually increased in the older stands. An increase in the leaf area index:fine root area ratio supports the idea that older stand are potentially limited by soil resources. Other factors contributing to slower growth in older stands might be lower soil temperatures and increased self-shading due to the clumped nature of crowns. Collectively, the proportionally greater reduction in fine roots in older stands might be the variable that predisposes these forests to be at a potentially greater risk of stress-induced mortality.

Allocation to leaf area and sapwood area affects water relations of co-occurring savanna and forest trees.

PubMed

Gotsch, Sybil G; Geiger, Erika L; Franco, Augusto C; Goldstein, Guillermo; Meinzer, Frederick C; Hoffmann, William A

2010-06-01

Water availability is a principal factor limiting the distribution of closed-canopy forest in the seasonal tropics, suggesting that forest tree species may not be well adapted to cope with seasonal drought. We studied 11 congeneric species pairs, each containing one forest and one savanna species, to test the hypothesis that forest trees have a lower capacity to maintain seasonal homeostasis in water relations relative to savanna species. To quantify this, we measured sap flow, leaf water potential (Psi(L)), stomatal conductance (g (s)), wood density, and Huber value (sapwood area:leaf area) of the 22 study species. We found significant differences in the water relations of these two species types. Leaf area specific hydraulic conductance of the soil/root/leaf pathway (G (t)) was greater for savanna species than forest species. The lower G (t) of forest trees resulted in significantly lower Psi(L) and g (s) in the late dry season relative to savanna trees. The differences in G (t) can be explained by differences in biomass allocation of savanna and forest trees. Savanna species had higher Huber values relative to forest species, conferring greater transport capacity on a leaf area basis. Forest trees have a lower capacity to maintain homeostasis in Psi(L) due to greater allocation to leaf area relative to savanna species. Despite significant differences in water relations, relationships between traits such as wood density and minimum Psi(L) were indistinguishable for the two species groups, indicating that forest and savanna share a common axis of water-use strategies involving multiple traits.

Sensitivity analyses of woody species exposed to air pollution based on ecophysiological measurements.

PubMed

Wen, Dazhi; Kuang, Yuanwen; Zhou, Guoyi

2004-01-01

Air pollution has been of a major problem in the Pearl River Delta of south China, particularly during the last two decades. Emissions of air pollutants from industries have already led to damages in natural communities and environments in a wide range of the Delta area. Leaf parameters such as chlorophyll fluorescence, leaf area (LA), dry weight (DW) and leaf mass per area (LMA) had once been used as specific indexes of environmental stress. This study aims to determine in situ if the daily variation of chlorophyll fluorescence and other ecophysiological parameters in five seedlings of three woody species, Ilex rotunda, Ficus microcarpa and Machilus chinensis, could be used alone or in combination with other measurements for sensitivity indexes to make diagnoses under air pollution stress and, hence, to choose the correct tree species for urban afforestation in the Delta area. Five seedlings of each species were transplanted in pot containers after their acclimation under shadowing conditions. Chlorophyll fluorescence measurements were made in situ by a portable fluorometer (OS-30, Opti-sciences, U.S.A). Ten random samples of leaves were picked from each species for LA measurements by area-meter (CI-203, CID, Inc., U.S.A). DW was determined after the leaf samples were dried to a constant weight at 65 degrees C. LMA was calculated as the ratio of DW/LA. Leaf N content was analyzed according to the Kjeldhal method, and the extraction of pigments was carried out according Lin et al. The daily mean Fv/Fm (Fv is the variable fluorescence and Fm is the maximum fluorescence) analysis showed that Ilex rotunda and Ficus microcarpa were more highly resistant to pollution stress, followed by Machilus chinensis, implying that the efficiency of photosystem II in I. rotunda was less affected by air pollutants than the other two species. Little difference in daily change of Fv/Fm in I. rotunda between the polluted and the clean site was also observed. However, a relatively large variation of Fv/Fm appeared in the other two species, particularly in M. chinensis, suggesting that they were more sensitive to air pollutants than I. rotunda. The mean LA was reduced for all species growing at the polluted site. The mean LMA for all species exceeded the sclerophylly threshold given by Cowling and Campbell and increased for those under pollution stress, which could be explained as one of the acclimation strategies for plants to air pollution stress. Little difference in leaf chlorophyll content was observed in F. microcarpa and M. chinensis, while remarkable differences were found in I. rotunda growing at the polluted and the clean site. Content of leaf carotenoids was largely reduced in I. rotunda growing at the polluted site, but increased in F. microcarpa and M. chinensis, compared with plants growing at the clean site. Plants growing at the clean site had a lower leaf N content than those growing at the polluted site. In addition, species with a higher resistance to pollution stress showed less difference in leaf N content than those sensitive species. Based on Fv/Fm measurements of the three woody species, I. rotunda showed the highest resistance to air pollutants from ceramic industries, followed by F. microcarpa. M. chinensis was the most sensitive species to air pollution, had lowest capacities to cope with the air pollution stress, which was consistent with visual injury symptoms observed in the crown profiles of plants at the polluted site. Fv/Fm, LAM, LA, leaf pigments and N content could be used alone or in combination to diagnose the extent of the physiological injury. The ratio of Fv/Fm, however, was the best and most effective parameter. Tree species which have higher air-pollutant resistance, as diagnosed by such ecophysiological parameters, should be considered first and planted widely for urban afforestation or forest regeneration in areas where the forest was seriously degraded or forest health was markedly effected by the same kind of air pollutants.

Synchrotron X-ray computed laminography of the three-dimensional anatomy of tomato leaves.

PubMed

Verboven, Pieter; Herremans, Els; Helfen, Lukas; Ho, Quang T; Abera, Metadel; Baumbach, Tilo; Wevers, Martine; Nicolaï, Bart M

2015-01-01

Synchrotron radiation computed laminography (SR-CL) is presented as an imaging method for analyzing the three-dimensional (3D) anatomy of leaves. The SR-CL method was used to provide 3D images of 1-mm² samples of intact leaves at a pixel resolution of 750 nm. The method allowed visualization and quantitative analysis of palisade and spongy mesophyll cells, and showed local venation patterns, aspects of xylem vascular structure and stomata. The method failed to image subcellular organelles such as chloroplasts. We constructed 3D computer models of leaves that can provide a basis for calculating gas exchange, light penetration and water and solute transport. The leaf anatomy of two different tomato genotypes grown in saturating light conditions was compared by 3D analysis. Differences were found in calculated values of tissue porosity, cell number density, cell area to volume ratio and cell volume and cell shape distributions of palisade and spongy cell layers. In contrast, the exposed cell area to leaf area ratio in mesophyll, a descriptor that correlates to the maximum rate of photosynthesis in saturated light conditions, was no different between spongy and palisade cells or between genotypes. The use of 3D image processing avoids many of the limitations of anatomical analysis with two-dimensional sections. © 2014 The Authors The Plant Journal © 2014 John Wiley & Sons Ltd.

Applying remote sensing measurements of phenology to southern California vegetation

NASA Astrophysics Data System (ADS)

Willis, K. S.; Gillespie, T. W.

2012-12-01

Monitoring vegetation phenology can be used to assess the impacts of climate change on a localized region. This study aims to determine the most applicable remote sensing method for monitoring phenological changes in the largest urban National Park in the US: the Santa Monica Mountains of southern California. This is achieved by comparing the Normalized Difference Vegetation Index (NDVI), considered applicable to Mediterranean-type ecosystems due to the low amount of greenness present in the vegetation, with relative spectral mixture analysis (RMSA). RMSA is a technique developed to measure temporal changes in green vegetation (GV), nonphotosynthetic vegetation plus litter (NPV), and snow cover designed for the south-central US. This study analyzes areas of natural vegetation in the Santa Monica Mountains using MODIS imagery by comparing GV and NPV indices derived from RMSA with the classic NDVI. The phenological transition dates of focus here include: (1) greenup, the date of onset of photosynthetic activity; (2) maturity, the date at which plant green leaf area is maximum; (3) senescence, the date at which photosynthetic activity and green leaf area begin to rapidly decrease; (4) dormancy, the date at which physiological activity becomes near zero. Overall, this study tests the application of RMSA to a new environment, compares these results to those derived from NDVI, and provides insight regarding the impacts of climate change on southern California phenological cycles.

Error analysis of leaf area estimates made from allometric regression models

NASA Technical Reports Server (NTRS)

Feiveson, A. H.; Chhikara, R. S.

1986-01-01

Biological net productivity, measured in terms of the change in biomass with time, affects global productivity and the quality of life through biochemical and hydrological cycles and by its effect on the overall energy balance. Estimating leaf area for large ecosystems is one of the more important means of monitoring this productivity. For a particular forest plot, the leaf area is often estimated by a two-stage process. In the first stage, known as dimension analysis, a small number of trees are felled so that their areas can be measured as accurately as possible. These leaf areas are then related to non-destructive, easily-measured features such as bole diameter and tree height, by using a regression model. In the second stage, the non-destructive features are measured for all or for a sample of trees in the plots and then used as input into the regression model to estimate the total leaf area. Because both stages of the estimation process are subject to error, it is difficult to evaluate the accuracy of the final plot leaf area estimates. This paper illustrates how a complete error analysis can be made, using an example from a study made on aspen trees in northern Minnesota. The study was a joint effort by NASA and the University of California at Santa Barbara known as COVER (Characterization of Vegetation with Remote Sensing).

Does enemy damage vary across the range of exotic plant species? Evidence from two coastal dune plant species in eastern Australia.

PubMed

Tabassum, Samiya; Leishman, Michelle R

2018-02-01

Release from natural enemies is often cited as a key factor for understanding the success of invasive plant species in novel environments. However, with time invasive species will accumulate native enemies in their invaded range, with factors such as spread distance from the site of introduction, climate and leaf-level traits potentially affecting enemy acquisition rates. However, the influence of such factors is difficult to assess without examining enemy attack across the entire species' range. We tested the significance of factors associated with range expansion (distance from source population and maximum population density), climatic variables (annual temperature and rainfall) and leaf-level traits [specific leaf area (SLA) and foliar nitrogen concentration] in explaining variation in enemy damage across multiple populations of two coastal invasive plants (Gladiolus gueinzii Kunze and Hydrocotyle bonariensis Lam.) along their entire introduced distribution in eastern Australia. We found that for H. bonariensis, amount of foliar damage increased with distance from source population. In contrast, for G. gueinzii, probability and amount of foliar damage decreased with decreasing temperature and increasing rainfall, respectively. Our results show that patterns of enemy attack across species' ranges are complex and cannot be generalised between species or even range edges.

Intraspecific variability in functional traits matters: case study of Scots pine.

PubMed

Laforest-Lapointe, Isabelle; Martínez-Vilalta, Jordi; Retana, Javier

2014-08-01

Although intraspecific trait variability is an important component of species ecological plasticity and niche breadth, its implications for community and functional ecology have not been thoroughly explored. We characterized the intraspecific functional trait variability of Scots pine (Pinus sylvestris) in Catalonia (NE Spain) in order to (1) compare it to the interspecific trait variability of trees in the same region, (2) explore the relationships among functional traits and the relationships between them and stand and climatic variables, and (3) study the role of functional trait variability as a determinant of radial growth. We considered five traits: wood density (WD), maximum tree height (H max), leaf nitrogen content (Nmass), specific leaf area (SLA), and leaf biomass-to-sapwood area ratio (B L:A S). A unique dataset was obtained from the Ecological and Forest Inventory of Catalonia (IEFC), including data from 406 plots. Intraspecific trait variation was substantial for all traits, with coefficients of variation ranging between 8% for WD and 24% for B L:A S. In some cases, correlations among functional traits differed from those reported across species (e.g., H max and WD were positively related, whereas SLA and Nmass were uncorrelated). Overall, our model accounted for 47% of the spatial variability in Scots pine radial growth. Our study emphasizes the hierarchy of factors that determine intraspecific variations in functional traits in Scots pine and their strong association with spatial variability in radial growth. We claim that intraspecific trait variation is an important determinant of responses of plants to changes in climate and other environmental factors, and should be included in predictive models of vegetation dynamics.

Hydraulic Limits on Maximum Plant Transpiration

NASA Astrophysics Data System (ADS)

Manzoni, S.; Vico, G.; Katul, G. G.; Palmroth, S.; Jackson, R. B.; Porporato, A. M.

2011-12-01

Photosynthesis occurs at the expense of water losses through transpiration. As a consequence of this basic carbon-water interaction at the leaf level, plant growth and ecosystem carbon exchanges are tightly coupled to transpiration. In this contribution, the hydraulic constraints that limit transpiration rates under well-watered conditions are examined across plant functional types and climates. The potential water flow through plants is proportional to both xylem hydraulic conductivity (which depends on plant carbon economy) and the difference in water potential between the soil and the atmosphere (the driving force that pulls water from the soil). Differently from previous works, we study how this potential flux changes with the amplitude of the driving force (i.e., we focus on xylem properties and not on stomatal regulation). Xylem hydraulic conductivity decreases as the driving force increases due to cavitation of the tissues. As a result of this negative feedback, more negative leaf (and xylem) water potentials would provide a stronger driving force for water transport, while at the same time limiting xylem hydraulic conductivity due to cavitation. Here, the leaf water potential value that allows an optimum balance between driving force and xylem conductivity is quantified, thus defining the maximum transpiration rate that can be sustained by the soil-to-leaf hydraulic system. To apply the proposed framework at the global scale, a novel database of xylem conductivity and cavitation vulnerability across plant types and biomes is developed. Conductivity and water potential at 50% cavitation are shown to be complementary (in particular between angiosperms and conifers), suggesting a tradeoff between transport efficiency and hydraulic safety. Plants from warmer and drier biomes tend to achieve larger maximum transpiration than plants growing in environments with lower atmospheric water demand. The predicted maximum transpiration and the corresponding leaf water potential compare well with measured peak transpiration and minimum water potentials across plant types and biomes, suggesting that plant water transport system and stomatal regulation co-evolved to meet peak atmospheric demands, thus sustaining carbon uptake while avoiding tissue damage even in such harsh conditions.

Plasticity in the Huber value contributes to homeostasis in leaf water relations of a mallee Eucalypt with variation to groundwater depth.

PubMed

Carter, Jennifer L; White, Donald A

2009-11-01

Information on how vegetation adapts to differences in water supply is critical for predicting vegetation survival, growth and water use, which, in turn, has important impacts on site hydrology. Many field studies assess adaptation to water stress by comparing between disparate sites, which makes it difficult to distinguish between physiological or morphological changes and long-term genetic adaptation. When planting trees into new environments, the phenotypic adaptations of a species to water stress will be of primary interest. This study examined the response to water availability of Eucalyptus kochii ssp. borealis (C. Gardner) D. Nicolle, commonly integrated with agriculture in south-western Australia for environmental and economic benefits. By choosing a site where the groundwater depth varied but where climate and soil type were the same, we were able to isolate tree response to water supply. Tree growth, leaf area and stand water use were much larger for trees over shallow groundwater than for trees over a deep water table below a silcrete hardpan. However, water use on a leaf area basis was similar in trees over deep and shallow groundwater, as were the minimum leaf water potential observed over different seasons and the turgor loss point. We conclude that homeostasis in leaf water use and water relations was maintained through a combination of stomatal control and adjustment of sapwood-to-leaf area ratios (Huber value). Differences in the Huber value with groundwater depth were associated with different sapwood-specific conductivity and water use on a sapwood area basis. Knowledge of the coordination between water supply, leaf area, sapwood area and leaf transpiration rate for different species will be important when predicting stand water use.

Tree ecophysiology research at Taylor Woods

Treesearch

Thomas E. Kolb; Nate G. McDowell

2008-01-01

We summarize the key findings of tree ecophysiology studies performed at Taylor Woods, Fort Valley Experimental Forest, Arizona between 1994 and 2003 that provide unique insight on impacts of long-term stand density management in ponderosa pine forests on tree water relations, leaf gas exchange, radial growth, leaf area-to-sapwood-area ratio, growth efficiency, leaf...

Preliminary application of tapered glass capillary microbeam in MeV-PIXE mapping of longan leaf for elemental concentration distribution analysis

NASA Astrophysics Data System (ADS)

Natyanun, S.; Unai, S.; Yu, L. D.; Tippawan, U.; Pussadee, N.

2017-09-01

This study was aimed at understanding elemental concentration distribution in local longan leaf for how the plant was affected by the environment or agricultural operation. The analysis applied the MeV-microbeam particle induced X-ray emission (PIXE) mapping technique using a home-developed tapered glass capillary microbeam system at Chiang Mai University. The microbeam was 2-MeV proton beam in 130 µm in diameter. The studying interest was in the difference in the elemental concentrations distributed between the leaf midrib and lamina areas. The micro proton beam analyzed the leaf sample across the leaf midrib edge to the leaf lamina area for total 9 data requisition spots. The resulting data were colored to form a 1D-map of the elemental concentration distribution. Seven dominant elements, Al, S, Cl, K, Ca, Sc and Fe, were identified, the first six of which were found having higher concentrations in the midrib area than in the lamina area, while the Fe concentration was in an opposite trend to that of the others.

Gross rainfall amount and maximum rainfall intensity in 60-minute influence on interception loss of shrubs: a 10-year observation in the Tengger Desert.

PubMed

Zhang, Zhi-Shan; Zhao, Yang; Li, Xin-Rong; Huang, Lei; Tan, Hui-Juan

2016-05-17

In water-limited regions, rainfall interception is influenced by rainfall properties and crown characteristics. Rainfall properties, aside from gross rainfall amount and duration (GR and RD), maximum rainfall intensity and rainless gap (RG), within rain events may heavily affect throughfall and interception by plants. From 2004 to 2014 (except for 2007), individual shrubs of Caragana korshinskii and Artemisia ordosica were selected to measure throughfall during 210 rain events. Various rainfall properties were auto-measured and crown characteristics, i.e., height, branch and leaf area index, crown area and volume of two shrubs were also measured. The relative interceptions of C. korshinskii and A. ordosica were 29.1% and 17.1%, respectively. Rainfall properties have more contributions than crown characteristics to throughfall and interception of shrubs. Throughfall and interception of shrubs can be explained by GR, RI60 (maximum rainfall intensities during 60 min), RD and RG in deceasing importance. However, relative throughfall and interception of two shrubs have different responses to rainfall properties and crown characteristics, those of C. korshinskii were closely related to rainfall properties, while those of A. ordosica were more dependent on crown characteristics. We highlight long-term monitoring is very necessary to determine the relationships between throughfall and interception with crown characteristics.

Testing the adaptive plasticity of Iris pumila leaf traits to natural light conditions using phenotypic selection analysis

NASA Astrophysics Data System (ADS)

Tucić, Branka; Tomić, Vladimir; Avramov, Stevan; Pemac, Danijela

1998-12-01

A multivariate selection analysis has been used to test the adaptiveness of several Iris pumila leaf traits that display plasticity to natural light conditions. Siblings of a synthetic population comprising 31 families of two populations from contrasting light habitats were grown at an open dune site and in the understory of a Pinus nigra stand in order to score variation in phenotypic expression of six leaf traits: number of senescent leaves, number of live leaves, leaf length, leaf width, leaf angle, and specific leaf area. The ambient light conditions affected the values of all traits studied except for specific leaf area. In accordance to ecophysiological expectations for an adaptive response to light, both leaf length and width were significantly greater while the angle between sequential leaves was significantly smaller in the woodland understory than at the exposed dune site. The relationship between leaf traits and vegetative fitness (total leaf area) differed across light habitats as predicted by functional hypotheses. The standardized linear selection gradient ( β') for leaf length and width were positive in sign in both environments, but their magnitude for leaf length was higher in the shade than under full sunlight. Since plasticity of leaf length in the woodland shade has been recognized as adaptive, fitness cost of producing plastic change in leaf length was assessed. In both of the available methods used, the two-step and the multivariate regression procedures, a rather high negative association between the fitness value and the plasticity of leaf length was obtained, indicating a cost of plasticity. The selection gradient for leaf angle was weak and significant only in the woodland understory. Genetic correlations between trait expressions in contrasting light environments were negative in sign and low in magnitude, implying a significant genetic variation for plasticity in these leaf traits. Furthermore, leaf length and leaf width were found to be genetically positively coupled, which indicates that there is a potential for these two traits to evolve toward their optimal phenotypic values even faster than would be expected if they were genetically independent.

Herbivory alters plant carbon assimilation, patterns of biomass allocation and nitrogen use efficiency

NASA Astrophysics Data System (ADS)

Peschiutta, María Laura; Scholz, Fabián Gustavo; Goldstein, Guillermo; Bucci, Sandra Janet

2018-01-01

Herbivory can trigger physiological processes resulting in leaf and whole plant functional changes. The effects of chronic infestation by an insect on leaf traits related to carbon and nitrogen economy in three Prunus avium cultivars were assessed. Leaves from non-infested trees (control) and damaged leaves from infested trees were selected. The insect larvae produce skeletonization of the leaves leaving relatively intact the vein network of the eaten leaves and the abaxial epidermal tissue. At the leaf level, nitrogen content per mass (Nmass) and per area (Narea), net photosynthesis per mass (Amass) and per area (Aarea), photosynthetic nitrogen-use efficiency (PNUE), leaf mass per area (LMA) and total leaf phenols content were measured in the three cultivars. All cultivars responded to herbivory in a similar fashion. The Nmass, Amass, and PNUE decreased, while LMA and total content of phenols increased in partially damaged leaves. Increases in herbivore pressure resulted in lower leaf size and total leaf area per plant across cultivars. Despite this, stem cumulative growth tended to increase in infected plants suggesting a change in the patterns of biomass allocation and in resources sequestration elicited by herbivory. A larger N investment in defenses instead of photosynthetic structures may explain the lower PNUE and Amass observed in damaged leaves. Some physiological changes due to herbivory partially compensate for the cost of leaf removal buffering the carbon economy at the whole plant level.

Land use affects the net ecosystem CO2 exchange and its components in mountain grasslands

PubMed Central

Schmitt, M.; Bahn, M.; Wohlfahrt, G.; Tappeiner, U.; Cernusca, A.

2011-01-01

Changes in land use and management have been strongly affecting mountain grassland, however, their effects on the net ecosystem exchange of CO2 (NEE) and its components have not yet been well documented. We analysed chamber-based estimates of NEE, gross primary productivity (GPP), ecosystem respiration (R) and light use efficiency (LUE) of six mountain grasslands differing in land use and management, and thus site fertility, for the growing seasons of 2002 to 2008. The main findings of the study are that: (1) land use and management affected seasonal NEE, GPP and R, which all decreased from managed to unmanaged grasslands; (2) these changes were explained by differences in leaf area index (LAI), biomass and leaf-area-independent changes that were likely related to photosynthetic physiology; (3) diurnal variations of NEE were primarily controlled by photosynthetically active photon flux density and soil and air temperature; seasonal variations were associated with changes in LAI; (4) parameters of light response curves were generally closely related to each other, and the ratio of R at a reference temperature/ maximum GPP was nearly constant across the sites; (5) similarly to our study, maximum GPP and R for other grasslands on the globe decreased with decreasing land use intensity, while their ratio remained remarkably constant. We conclude that decreasing intensity of management and, in particular, abandonment of mountain grassland lead to a decrease in NEE and its component processes. While GPP and R are generally closely coupled during most of the growing season, GPP is more immediately and strongly affected by land management (mowing, grazing) and season. This suggests that management and growing season length, as well as their possible future changes, may play an important role for the annual C balance of mountain grassland. PMID:23293657

Seasonal patterns of leaf photosynthetic and secondary xylem vascular traits in current-year stems of three Sorbus species with contrasting growth habits.

PubMed

Ďurkovič, J; Čaňová, I; Kardošová, M; Kurjak, D

2014-09-01

Seasonal effects of environmental variables on photosynthetic activity and secondary xylem formation provide data to demonstrate how environmental factors together with leaf ageing during the season control tree growth. In this study, we assessed physiological responses in photosynthetic behaviour to seasonal climate changes, and also identified seasonal differences in vascular traits within differentiating secondary xylem tissue from three diploid species of the taxonomically complex genus Sorbus. From sampling day 150, a clear physiological segregation of S. chamaemespilus from S. torminalis and S. aria was evident. The shrubby species S. chamaemespilus could be distinguished by a higher photosynthetic capacity between days 150 and 206. This was reflected in its associations with net CO2 assimilation rate (PN), maximum photochemical efficiency of PSII (F(v)/F(m)), variable-to-initial fluorescence ratio (F(v)/F(0)), potential electron acceptor capacity ('area') in multivariate space, and also its associations with log-transformed vessel area and log-transformed relative conductivity between days 239 and 268. The maximum segregation and differentiation among the examined Sorbus species was on sampling day 206. The largest differences between S. torminalis and S. aria were found on day 115, when the latter species clearly showed closer associations with high values of vessel density and transpiration (E). Sampling day clusters were arranged along an arch-like gradient that reflected the positioning of the entire growing season in multivariate space. This arch-like pattern was most apparent in the case of S. chamaemespilus, but was also observed in S. torminalis and S. aria. © 2014 German Botanical Society and The Royal Botanical Society of the Netherlands.

Leaf phenological characters of main tree species in urban forest of Shenyang.

PubMed

Xu, Sheng; Xu, Wenduo; Chen, Wei; He, Xingyuan; Huang, Yanqing; Wen, Hua

2014-01-01

Plant leaves, as the main photosynthetic organs and the high energy converters among primary producers in terrestrial ecosystems, have attracted significant research attention. Leaf lifespan is an adaptive characteristic formed by plants to obtain the maximum carbon in the long-term adaption process. It determines important functional and structural characteristics exhibited in the environmental adaptation of plants. However, the leaf lifespan and leaf characteristics of urban forests were not studied up to now. By using statistic, linear regression methods and correlation analysis, leaf phenological characters of main tree species in urban forest of Shenyang were observed for five years to obtain the leafing phenology (including leafing start time, end time, and duration), defoliating phenology (including defoliation start time, end time, and duration), and the leaf lifespan of the main tree species. Moreover, the relationships between temperature and leafing phenology, defoliating phenology, and leaf lifespan were analyzed. The timing of leafing differed greatly among species. The early leafing species would have relatively early end of leafing; the longer it took to the end of leafing would have a later time of completed leafing. The timing of defoliation among different species varied significantly, the early defoliation species would have relatively longer duration of defoliation. If the mean temperature rise for 1°C in spring, the time of leafing would experience 5 days earlier in spring. If the mean temperature decline for 1°C, the time of defoliation would experience 3 days delay in autumn. There is significant correlation between leaf longevity and the time of leafing and defoliation. According to correlation analysis and regression analysis, there is significant correlation between temperature and leafing and defoliation phenology. Early leafing species would have a longer life span and consequently have advantage on carbon accumulation compared with later defoliation species.

Experimental manipulation of leaf litter colonization by aquatic invertebrates in a third order tropical stream.

PubMed

Uieda, V S; Carvalho, E M

2015-05-01

Through a manipulative experiment, the colonization of leaf litter by invertebrates was investigated in two sections of a tropical stream (spatial scale) that differed in function of the canopy cover, one with the presence (closed area) and another without riparian vegetation (open area), during one month of the dry and one of the wet season (temporal scale). The work aimed to verify differences related to four variables: season, canopy cover, leaf type and leaf condition. Litter bags containing arboreal and herbaceous leaves (leaf type variable), non-conditioned and preconditioned (leaf condition variable) were placed at the bottom of the stream in each area (canopy cover variable) and season (dry and wet), and removed after 13-day colonization. The analysis of the remaining litter dry mass per leaf bag emphasizes differences related mainly to seasonality, canopy cover and leaf type, although leaf condition was also important when combined with those three factors. Comparing the abundance of invertebrates per treatment, there was a tendency of high predominance of Chironomidae during the dry season and greater taxa diversity and evenness during the wet season, when the water flow increase could alter the availability of microhabitats for local fauna. Even though canopy cover alone was not a significant source of variation in the abundance of invertebrates, the results showed a tendency of a combined effect of canopy cover with seasonality and leaf condition.

Extracting forest canopy structure from spatial information of high resolution optical imagery: tree crown size versus leaf area index

Treesearch

C. Song; M.B. Dickinson

2008-01-01

Leaves are the primary interface where energy, water and carbon exchanges occur between the forest ecosystems and the atmosphere. Leaf area index (LAI) is a measure of the amount of leaf area in a stand, and the tree crown size characterizes how leaves are clumped in the canopy. Both LAI and tree crown size are of essential ecological and management value. There is a...

Field- and Remote Sensing-based Structural Attributes Measured at Multiple Scales Influence the Relationship Between Nitrogen and Reflectance of Forest Canopies

NASA Astrophysics Data System (ADS)

Sullivan, F.; Ollinger, S. V.; Palace, M. W.; Ouimette, A.; Sanders-DeMott, R.; Lepine, L. C.

2017-12-01

The correlation between near-infrared reflectance and forest canopy nitrogen concentration has been demonstrated at varying scales using a range of optical sensors on airborne and satellite platforms. Although the mechanism underpinning the relationship is unclear, at its basis are biologically-driven functional relationships of multiple plant traits that affect canopy chemistry and structure. The link between near-infrared reflectance and canopy nitrogen has been hypothesized to be partially driven by covariation of canopy nitrogen with canopy structure. In this study, we used a combination of airborne LiDAR data and field measured leaf and canopy chemical and structural traits to explore interrelationships between canopy nitrogen, near-infrared reflectance, and canopy structure on plots at Bartlett Experimental Forest in the White Mountain National Forest, New Hampshire. Over each plot, we developed a 1-meter resolution canopy height profile and a 1-meter resolution canopy height model. From canopy height profiles and canopy height models, we calculated a set of metrics describing the plot-level variability, breadth, depth, and arrangement of LiDAR returns. This combination of metrics was used to describe both vertical and horizontal variation in structure. In addition, we developed and measured several field-based metrics of leaf and canopy structure at the plot scale by directly measuring the canopy or by weighting leaf-level metrics by species leaf area contribution. We assessed relationships between leaf and structural metrics, near-infrared reflectance and canopy nitrogen concentration using multiple linear regression and mixed effects modeling. Consistent with our hypothesis, we found moderately strong links between both near-infrared reflectance and canopy nitrogen concentration with LiDAR-derived structural metrics, and we additionally found that leaf-level metrics scaled to the plot level share an important role in canopy reflectance. We suggest that canopy structure has a governing role in canopy reflectance, reducing maximum potential reflectance as structural complexity increases, and therefore also influences the relationship between canopy nitrogen and NIR reflectance.

Microhabitats and canopy cover moderate high summer temperatures in a fragmented Mediterranean landscape.

PubMed

Keppel, Gunnar; Anderson, Sharolyn; Williams, Craig; Kleindorfer, Sonia; O'Connell, Christopher

2017-01-01

Extreme heat events will become more frequent under anthropogenic climate change, especially in Mediterranean ecosystems. Microhabitats can considerably moderate (buffer) the effects of extreme weather events and hence facilitate the persistence of some components of the biodiversity. We investigate the microclimatic moderation provided by two important microhabitats (cavities formed by the leaves of the grass-tree Xanthorrhoea semiplana F.Muell., Xanthorrhoeaceae; and inside the leaf-litter) during the summer of 2015/16 on the Fleurieu Peninsula of South Australia. We placed microsensors inside and outside these microhabitats, as well as above the ground below the forest canopy. Grass-tree and leaf-litter microhabitats significantly buffered against high temperatures and low relative humidity, compared to ground-below-canopy sensors. There was no significant difference between grass-tree and leaf-litter temperatures: in both microhabitats, daily temperature variation was reduced, day temperatures were 1-5°C cooler, night temperatures were 0.5-3°C warmer, and maximum temperatures were up to 14.4°C lower, compared to ground-below-canopy sensors. Grass-tree and leaf-litter microhabitats moderated heat increase at an average rate of 0.24°C temperature per 1°C increase of ambient temperature in the ground-below-canopy microhabitat. The average daily variation in temperature was determined by the type (grass-tree and leaf-litter versus ground-below-canopy) of microhabitat (explaining 67%), the amount of canopy cover and the area of the vegetation fragment (together explaining almost 10% of the variation). Greater canopy cover increased the amount of microclimatic moderation provided, especially in the leaf-litter. Our study highlights the importance of microhabitats in moderating macroclimatic conditions. However, this moderating effect is currently not considered in species distribution modelling under anthropogenic climate change nor in the management of vegetation. This shortcoming will have to be addressed to obtain realistic forecasts of future species distributions and to achieve effective management of biodiversity.

Effects of regulated deficit irrigation during the pre-harvest period on gas exchange, leaf development and crop yield of mature almond trees.

PubMed

Romero, Pascual; Navarro, Josefa Maria; García, Francisco; Botía Ordaz, Pablo

2004-03-01

We investigated the effects of regulated deficit irrigation (RDI) during the pre-harvest period (kernel-filling stage) on water relations, leaf development and crop yield in mature almond (Prunus dulcis (Mill.) D.A. Webb cv. Cartagenera) trees during a 2-year field experiment. Trees were either irrigated at full-crop evapotranspiration (ETc=100%) (well-irrigated control treatment) or subjected to an RDI treatment that consisted of full irrigation for the full season, except from early June to early August (kernel-filling stage), when 20% ETc was applied. The severity of water stress was characterized by measurements of soil water content, predawn leaf water potential (Psipd) and relative water content (RWC). Stomatal conductance (gs), net CO2 assimilation rate (A), transpiration rate (E), leaf abscission, leaf expansion rate and crop yield were also measured. In both years, Psipd and RWC of well-irrigated trees were maintained above -1.0 MPa and 92%, respectively, whereas the corresponding values for trees in the RDI treatment were -2.37 MPa and 82%. Long-term water stress led to a progressive decline in gs, A and E, with significant reductions after 21 days in the RDI treatment. At the time of maximum stress (48 days after commencement of RDI), A, gs and E were 64, 67 and 56% lower than control values, respectively. High correlations between A, E and gs were observed. Plant water status recovered within 15 days after the resumption of irrigation and was associated with recovery of soil water content. A relatively rapid and complete recovery of A and gs was also observed, although the recovery was slower than for Psipd and RWC. Severe water stress during the kernel-filling stage resulted in premature defoliation (caused by increased leaf abscission) and a reduction in leaf growth rate, which decreased tree leaf area. Although kernel yield was correlated with leaf water potential, RDI caused a nonsignificant 7% reduction in kernel yield and had no effect on kernel size. The RDI treatment also improved water-use efficiency because about 30% less irrigation water was applied in the RDI treatment than in the control treatment. We conclude that high-cropping almonds can be successfully grown in semiarid regions in an RDI regime provided that Psipd is maintained above a threshold value of -2 MPa.

Extracting scene feature vectors through modeling, volume 3

NASA Technical Reports Server (NTRS)

Berry, J. K.; Smith, J. A.

1976-01-01

The remote estimation of the leaf area index of winter wheat at Finney County, Kansas was studied. The procedure developed consists of three activities: (1) field measurements; (2) model simulations; and (3) response classifications. The first activity is designed to identify model input parameters and develop a model evaluation data set. A stochastic plant canopy reflectance model is employed to simulate reflectance in the LANDSAT bands as a function of leaf area index for two phenological stages. An atmospheric model is used to translate these surface reflectances into simulated satellite radiance. A divergence classifier determines the relative similarity between model derived spectral responses and those of areas with unknown leaf area index. The unknown areas are assigned the index associated with the closest model response. This research demonstrated that the SRVC canopy reflectance model is appropriate for wheat scenes and that broad categories of leaf area index can be inferred from the procedure developed.

Leaf morphological effects predict effective path length and enrichment of 18O in leaf water of different Eucalyptus species

NASA Astrophysics Data System (ADS)

Kahmen, A.; Merchant, A.; Callister, A.; Dawson, T. E.; Arndt, S. K.

2006-12-01

Stable isotopes have been a valuable tool to study water or carbon fluxes of plants and ecosystems. In particular oxygen isotopes (δ18O) in leaf water or plant organic material are now beginning to be established as a simple and integrative measure for plant - water relations. Current δ18O models, however, are still limited in their application to a broad range of different species and ecosystems. It remains for example unclear, if species-specific effects such as different leaf morphologies need to be included in the models for a precise understanding and prediction of δ18O signals. In a common garden experiment (Currency Creek Arboretum, South Australia), where over 900 different Eucalyptus species are cultivated in four replicates, we tested effects of leaf morphology and anatomy on δ18O signals in leaf water of 25 different species. In particular, we determined for all species enrichment in 18O of mean lamina leaf water above source water (Δ18O) as related to leaf physiology as well as leaf thickness, leaf area, specific leaf area and weight and selected anatomical properties. Our data revealed that diurnal Δ18O in leaf water at steady state was significantly different among the investigated species and with differences up to 10% at midday. Fitting factors (effective path length) of leaf water Δ18O models were also significantly different among the investigated species and were highly affected by species-specific morphological parameters. For example, leaf area explained a high percentage of the differences in effective path length observed among the investigated species. Our data suggest that leaf water δ18O can act as powerful tool to estimate plant - water relations in comparative studies but that additional leaf morphological parameters need to be considered in existing δ18O models for a better interpretation of the observed δ18O signals.

Canopy and seasonal profiles of nitrate reductase in soybeans

DOE Office of Scientific and Technical Information (OSTI.GOV)

Harper, J.E.; Hageman, R.H.

1972-01-01

Nitrate reductase activity of soybeans (Glycine max L. Merr.) was evaluated in soil plots and outdoor hydroponic gravel culture systems throughout the growing season. Nitrate reductase profiles within the plant canopy were also established. Mean activity per gram fresh weight per hour of the entire plant canopy was highest in the seedling stage while total activity (activity per gram fresh weight per hour times the total leaf weight) reached a maximum when plants were in the full bloom to midpod fill stage. Nitrate reductase activity per gram fresh weight per hour was highest in the uppermost leaf just prior tomore » full expansion and declined with leaf positions lower in the canopy. Total nitrate reductase activity per leaf was also highest in the uppermost fully expanded leaf during early growth stages. Maximum total activity shifted to leaf positions lower in the plant canopy with later growth stages. Nitrate reductase activity of soybeans grown in hydroponic systems was significantly higher than activity of adjacent soil grown plants at later growth stages, which suggested that under normal field conditions the potential for nitrate utilization may not be realized. Nitrate reductase activity per gram fresh weight per hour and nitrate content were positively correlated over the growing season with plants grown in either soil or solution culture. Computations based upon the nitrate reductase assay of plants grown in hydroponics indicated that from 1.7 to 1.8 grams N could have been supplied to the plant via the nitrate reductase process. 11 references, 9 figures, 3 tables.« less

Trade-offs between water transport capacity and drought resistance in neotropical canopy liana and tree species.

PubMed

De Guzman, Mark E; Santiago, Louis S; Schnitzer, Stefan A; Álvarez-Cansino, Leonor

2017-10-01

In tropical forest canopies, it is critical for upper shoots to efficiently provide water to leaves for physiological function while safely preventing loss of hydraulic conductivity due to cavitation during periods of soil water deficit or high evaporative demand. We compared hydraulic physiology of upper canopy trees and lianas in a seasonally dry tropical forest to test whether trade-offs between safety and efficiency of water transport shape differences in hydraulic function between these two major tropical woody growth forms. We found that lianas showed greater maximum stem-specific hydraulic conductivity than trees, but lost hydraulic conductivity at less negative water potentials than trees, resulting in a negative correlation and trade-off between safety and efficiency of water transport. Lianas also exhibited greater diurnal changes in leaf water potential than trees. The magnitude of diurnal water potential change was negatively correlated with sapwood capacitance, indicating that lianas are highly reliant on conducting capability to maintain leaf water status, whereas trees relied more on stored water in stems to maintain leaf water status. Leaf nitrogen concentration was related to maximum leaf-specific hydraulic conductivity only for lianas suggesting that greater water transport capacity is more tied to leaf processes in lianas compared to trees. Our results are consistent with a trade-off between safety and efficiency of water transport and may have implications for increasing liana abundance in neotropical forests. © The Author 2016. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Visualizing the ill-posedness of the inversion of a canopy radiative transfer model: A case study for Sentinel-2

NASA Astrophysics Data System (ADS)

Zurita-Milla, R.; Laurent, V. C. E.; van Gijsel, J. A. E.

2015-12-01

Monitoring biophysical and biochemical vegetation variables in space and time is key to understand the earth system. Operational approaches using remote sensing imagery rely on the inversion of radiative transfer models, which describe the interactions between light and vegetation canopies. The inversion required to estimate vegetation variables is, however, an ill-posed problem because of variable compensation effects that can cause different combinations of soil and canopy variables to yield extremely similar spectral responses. In this contribution, we present a novel approach to visualise the ill-posed problem using self-organizing maps (SOM), which are a type of unsupervised neural network. The approach is demonstrated with simulations for Sentinel-2 data (13 bands) made with the Soil-Leaf-Canopy (SLC) radiative transfer model. A look-up table of 100,000 entries was built by randomly sampling 14 SLC model input variables between their minimum and maximum allowed values while using both a dark and a bright soil. The Sentinel-2 spectral simulations were used to train a SOM of 200 × 125 neurons. The training projected similar spectral signatures onto either the same, or contiguous, neuron(s). Tracing back the inputs that generated each spectral signature, we created a 200 × 125 map for each of the SLC variables. The lack of spatial patterns and the variability in these maps indicate ill-posed situations, where similar spectral signatures correspond to different canopy variables. For Sentinel-2, our results showed that leaf area index, crown cover and leaf chlorophyll, water and brown pigment content are less confused in the inversion than variables with noisier maps like fraction of brown canopy area, leaf dry matter content and the PROSPECT mesophyll parameter. This study supports both educational and on-going research activities on inversion algorithms and might be useful to evaluate the uncertainties of retrieved canopy biophysical and biochemical state variables.

Comparing salt tolerance of beet cultivars and their halophytic ancestor: consequences of domestication and breeding programmes

PubMed Central

Rozema, Jelte; Cornelisse, Danny; Zhang, Yuancheng; Li, Hongxiu; Bruning, Bas; Katschnig, Diana; Broekman, Rob; Ji, Bin; van Bodegom, Peter

2015-01-01

Salt tolerance of higher plants is determined by a complex set of traits, the timing and rate of evolution of which are largely unknown. We compared the salt tolerance of cultivars of sugar beet and their ancestor, sea beet, in hydroponic studies and evaluated whether traditional domestication and more recent breeding have changed salt tolerance of the cultivars relative to their ancestor. Our comparison of salt tolerance of crop cultivars is based on values of the relative growth rate (RGR) of the entire plant at various salinity levels. We found considerable salt tolerance of the sea beet and slightly, but significantly, reduced salt tolerance of the sugar beet cultivars. This indicates that traditional domestication by selection for morphological traits such as leaf size, beet shape and size, enhanced productivity, sugar content and palatability slightly affected salt tolerance of sugar beet cultivars. Salt tolerance among four sugar beet cultivars, three of which have been claimed to be salt tolerant, did not differ. We analysed the components of RGR to understand the mechanism of salt tolerance at the whole-plant level. The growth rate reduction at higher salinity was linked with reduced leaf area at the whole-plant level (leaf area ratio) and at the individual leaf level (specific leaf area). The leaf weight fraction was not affected by increased salinity. On the other hand, succulence and leaf thickness and the net assimilation per unit of leaf area (unit leaf rate) increased in response to salt treatment, thus partially counteracting reduced capture of light by lower leaf area. This compensatory mechanism may form part of the salt tolerance mechanism of sea beet and the four studied sugar beet cultivars. Together, our results indicate that domestication of the halophytic ancestor sea beet slightly reduced salt tolerance and that breeding for improved salt tolerance of sugar beet cultivars has not been effective. PMID:25492122

Leaf-on canopy closure in broadleaf deciduous forests predicted during winter

USGS Publications Warehouse

Twedt, Daniel J.; Ayala, Andrea J.; Shickel, Madeline R.

2015-01-01

Forest canopy influences light transmittance, which in turn affects tree regeneration and survival, thereby having an impact on forest composition and habitat conditions for wildlife. Because leaf area is the primary impediment to light penetration, quantitative estimates of canopy closure are normally made during summer. Studies of forest structure and wildlife habitat that occur during winter, when deciduous trees have shed their leaves, may inaccurately estimate canopy closure. We estimated percent canopy closure during both summer (leaf-on) and winter (leaf-off) in broadleaf deciduous forests in Mississippi and Louisiana using gap light analysis of hemispherical photographs that were obtained during repeat visits to the same locations within bottomland and mesic upland hardwood forests and hardwood plantation forests. We used mixed-model linear regression to predict leaf-on canopy closure from measurements of leaf-off canopy closure, basal area, stem density, and tree height. Competing predictive models all included leaf-off canopy closure (relative importance = 0.93), whereas basal area and stem density, more traditional predictors of canopy closure, had relative model importance of ≤ 0.51.

Leaf shrinkage with dehydration: coordination with hydraulic vulnerability and drought tolerance.

PubMed

Scoffoni, Christine; Vuong, Christine; Diep, Steven; Cochard, Hervé; Sack, Lawren

2014-04-01

Leaf shrinkage with dehydration has attracted attention for over 100 years, especially as it becomes visibly extreme during drought. However, little has been known of its correlation with physiology. Computer simulations of the leaf hydraulic system showed that a reduction of hydraulic conductance of the mesophyll pathways outside the xylem would cause a strong decline of leaf hydraulic conductance (K(leaf)). For 14 diverse species, we tested the hypothesis that shrinkage during dehydration (i.e. in whole leaf, cell and airspace thickness, and leaf area) is associated with reduction in K(leaf) at declining leaf water potential (Ψ(leaf)). We tested hypotheses for the linkage of leaf shrinkage with structural and physiological water relations parameters, including modulus of elasticity, osmotic pressure at full turgor, turgor loss point (TLP), and cuticular conductance. Species originating from moist habitats showed substantial shrinkage during dehydration before reaching TLP, in contrast with species originating from dry habitats. Across species, the decline of K(leaf) with mild dehydration (i.e. the initial slope of the K(leaf) versus Ψ(leaf) curve) correlated with the decline of leaf thickness (the slope of the leaf thickness versus Ψ(leaf) curve), as expected based on predictions from computer simulations. Leaf thickness shrinkage before TLP correlated across species with lower modulus of elasticity and with less negative osmotic pressure at full turgor, as did leaf area shrinkage between full turgor and oven desiccation. These findings point to a role for leaf shrinkage in hydraulic decline during mild dehydration, with potential impacts on drought adaptation for cells and leaves, influencing plant ecological distributions.

Drought effect on growth, gas exchange and yield, in two strains of local barley Ardhaoui, under water deficit conditions in southern Tunisia.

PubMed

Thameur, Afwa; Lachiheb, Belgacem; Ferchichi, Ali

2012-12-30

Two local barley strains cv. Ardhaoui originated from Tlalit and Switir, sourthern Tunisia were grown in pots in a glasshouse assay, under well-watered conditions for a month. Plants were then either subjected to water deficit (treatment) or continually well-watered (control). Control pots were irrigated several times each week to maintain soil moisture near field capacity (FC), while stress pots experienced soil drying by withholding irrigation until they reached 50% of FC. Variation in relative water content, leaf area, leaf appearance rate and leaf gas exchange (i.e. net CO(2) assimilation rate (A), transpiration (E), and stomatal conductance (gs)) in response to water deficit was investigated. High leaf relative water content (RWC) was maintained in Tlalit by stomatal closure and a reduction of leaf area. Reduction in leaf area was due to decline in leaf gas exchange during water deficit. Tlalit was found to be drought tolerant and able to maintain higher leaf RWC under drought conditions. Water deficit treatment reduced stomatal conductance by 43% at anthesis. High net CO(2) assimilation rate under water deficit was associated with high RWC (r = 0.998; P < 0.01). Decline in net CO(2) assimilation rate was due mainly to stomatal closure. Significant differences between studied strains in leaf gas exchange parameters were found, which can give some indications on the degree of drought tolerance. Thus, the ability of the low leaf area plants to maintain higher RWC could explain the differences in drought tolerance in studied barley strains. Results showed that Tlalit showed to be more efficient and more productive than Switir. Copyright © 2012 Elsevier Ltd. All rights reserved.

Effect of acid mist and air pollutants on yellow-poplar seedling height and leaf growth

Treesearch

Leon S. Dochinger; Keith F. Jensen; Keith F. Jensen

1985-01-01

One-year-old yellow-poplar seedlings were treated with acid mist at pH 2.5, 3.5, 4.5, and 5.5 either alone or in combination with 0.1 ppm 03, S02, and NO2 or NO2 plus S02. After 4 and 8 weeks of treatment, height, leaf area, and leaf and new shoot weight were determined and growth analysis variables calculated. Height, leaf area, and dry weight decreased with...

Tree ecophysiology research at Taylor Woods (P-53)

Treesearch

Thomas E. Kolb; Nate G. McDowell

2008-01-01

We summarize the key findings of tree ecophysiology studies performed at Taylor Woods, Fort Valley Experimental Forest, Arizona between 1994 and 2003 that provide unique insight on impacts of long-term stand density management in ponderosa pine forests on tree water relations, leaf gas exchange, radial growth, leaf area-to-sapwood-area ratio, growth efficiency, leaf...

Leaf area and net photosynthesis during development of Prunus serotina seedlings

Treesearch

Stephen B. Horsley; Kurt W. Gottschalk

1993-01-01

We used the plastochron index to study the relationship between plant age, leaf age and development, and net photosynthesis of black cherry (Prtmus serotina Ehrh.) seedlings. Leaf area and net photosynthesis were measured on all leaves >=75 mm of plants ranging in age from 7 to 20 plastochrons. Effects of plant developmental stage...

Sapwood area as an estimator of leaf area and foliar weight in cherrybark oak and green ash

Treesearch

James S. Meadows; John D. Hodges

2002-01-01

The relationships between foliar weight/leaf area and four stem dimensions (d.b.h., total stem cross-sectional area, total sapwood area, and current sapwood area at breast height) were investigated in two important bottomland tree species of the Southern United States, cherrybark oak (Quercus falcata var. pagodifolia ...

Temporal relationships between spectral response and agronomic variables of a corn canopy

NASA Technical Reports Server (NTRS)

Kimes, D. S.; Markham, B. L.; Tucker, C. J.; Mcmurtrey, J. E., III

1981-01-01

Attention is given to an experiment in which spectral radiance data collected in three spectral regions are related to corn canopy variables. The study extends the work of Tucker et al. (1979) in that more detailed measurements of corn canopy variables were made using quantitative techniques. Wet and dry green leaf biomass is considered along with the green leaf area index, chlorotic leaf biomass, chlorotic leaf area, and leaf water content. In addition, spectral data were collected with a hand-held radiometer having Landsat-D Thematic Mapper (TM) bands TM3 (0.63-0.69 micrometers), TM4 (0.76-0.90 micrometers), and TM5 (1.55-1.75 micrometers). TM3, TM4, and TM5 seem to be well situated spectrally for making remotely sensed measurements related to chlorophyll concentration, leaf density, and leaf water content.

Leaf area and light use efficiency patterns of Norway spruce under different thinning regimes and age classes

PubMed Central

Gspaltl, Martin; Bauerle, William; Binkley, Dan; Sterba, Hubert

2013-01-01

Silviculture focuses on establishing forest stand conditions that improve the stand increment. Knowledge about the efficiency of an individual tree is essential to be able to establish stand structures that increase tree resource use efficiency and stand level production. Efficiency is often expressed as stem growth per unit leaf area (leaf area efficiency), or per unit of light absorbed (light use efficiency). We tested the hypotheses that: (1) volume increment relates more closely with crown light absorption than leaf area, since one unit of leaf area can receive different amounts of light due to competition with neighboring trees and self-shading, (2) dominant trees use light more efficiently than suppressed trees and (3) thinning increases the efficiency of light use by residual trees, partially accounting for commonly observed increases in post-thinning growth. We investigated eight even-aged Norway spruce (Picea abies (L.) Karst.) stands at Bärnkopf, Austria, spanning three age classes (mature, immature and pole-stage) and two thinning regimes (thinned and unthinned). Individual leaf area was calculated with allometric equations and absorbed photosynthetically active radiation was estimated for each tree using the three-dimensional crown model Maestra. Absorbed photosynthetically active radiation was only a slightly better predictor of volume increment than leaf area. Light use efficiency increased with increasing tree size in all stands, supporting the second hypothesis. At a given tree size, trees from the unthinned plots were more efficient, however, due to generally larger tree sizes in the thinned stands, an average tree from the thinned treatment was superior (not congruent in all plots, thus only partly supporting the third hypothesis). PMID:25540477

Sensitive Indicators of Zonal Stipa Species to Changing Temperature and Precipitation in Inner Mongolia Grassland, China

PubMed Central

Lv, Xiaomin; Zhou, Guangsheng; Wang, Yuhui; Song, Xiliang

2016-01-01

Climate change often induces shifts in plant functional traits. However, knowledge related to sensitivity of different functional traits and sensitive indicator representing plant growth under hydrothermal change remains unclear. Inner Mongolia grassland is predicted to be one of the terrestrial ecosystems which are most vulnerable to climate change. In this study, we analyzed the response of four zonal Stipa species (S. baicalensis, S. grandis, S. breviflora, and S. bungeana) from Inner Mongolia grassland to changing temperature (control, increased 1.5, 2, 4, and 6°C), precipitation (decreased 30 and 15%, control, increased 15 and 30%) and their combined effects via climate control chambers. The relative change of functional traits in the unit of temperature and precipitation change was regarded as sensitivity coefficient and sensitive indicators were examined by pathway analysis. We found that sensitivity of the four Stipa species to changing temperature and precipitation could be ranked as follows: S. bungeana > S. grandis > S. breviflora > S. baicalensis. In particular, changes in leaf area, specific leaf area and root/shoot ratio could account for 86% of the changes in plant biomass in the four Stipa species. Also these three measurements were more sensitive to hydrothermal changes than the other functional traits. These three functional indicators reflected the combination of plant production capacity (leaf area), adaptive strategy (root/shoot ratio), instantaneous environmental effects (specific leaf area), and cumulative environmental effects (leaf area and root/shoot ratio). Thus, leaf area, specific leaf area and root/shoot ratio were chosen as sensitive indicators in response to changing temperature and precipitation for Stipa species. These results could provide the basis for predicting the influence of climate change on Inner Mongolia grassland based on the magnitude of changes in sensitive indicators. PMID:26904048

Size-dependent enhancement of water relations during post-fire resprouting.

PubMed

Schafer, Jennifer L; Breslow, Bradley P; Hollingsworth, Stephanie N; Hohmann, Matthew G; Hoffmann, William A

2014-04-01

In resprouting species, fire-induced topkill causes a reduction in height and leaf area without a comparable reduction in the size of the root system, which should lead to an increase in the efficiency of water transport after fire. However, large plants undergo a greater relative reduction in size, compared with small plants, so we hypothesized that this enhancement in hydraulic efficiency would be greatest among large growth forms. In the ecotone between long-leaf pine (Pinus palustris Mill.) savannas and wetlands, we measured stomatal conductance (gs), mid-day leaf water potential (Ψleaf), leaf-specific whole-plant hydraulic conductance (KL.p), leaf area and height of 10 species covering a range of growth forms in burned and unburned sites. As predicted, KL.p was higher in post-fire resprouts than in unburned plants, and the post-fire increase in KL.p was positively related to plant size. Specifically, large-statured species tended to undergo the greatest relative reductions in leaf area and height, and correspondingly experienced the greatest increases in KL.p. The post-fire increase in KL.p was smaller than expected, however, due to a decrease in absolute root hydraulic conductance (i.e., not scaled to leaf area). The higher KL.p in burned sites was manifested as an increase in gs rather than an increase in Ψleaf. Post-fire increases in gs should promote high rates of photosynthesis for recovery of carbohydrate reserves and aboveground biomass, which is particularly important for large-statured species that require more time to recover their pre-fire size.

Leaf Optical Properties in Higher Plants: Linking Spectral Characteristics to Stress and Chlorophyll Concentration

NASA Technical Reports Server (NTRS)

Carter, Gregory A.; Knapp, Alan K.

2000-01-01

A number of studies have linked responses in leaf spectral reflectance, transmittance or absorptance to physiological stress. A variety of stressors including dehydration, flooding,freezing, ozone, herbicides, competition, disease, insects and deficiencies in ectomycorrhizal development and N fertilization have been imposed on species ranging from grasses to conifers and deciduous trees. In this cases, the maximum difference in reflectance within the 400 - 850 nm wavelength range between control and stressed states occurred as a reflectance increase at wavelength near 700 nm. In studies that included transmittance and absorptance as well as reflectance, maximum differences occurred as increases and decreases, respectively, near 700 nm. This common optical response to stress could be simulated closely by varying the chlorophyll concentrations in senescent leaves of five species. The optical response to stress near 700 nm, as well as corresponding changes in reflectance that occur in the green-yellow spectrum, can be explained by the general tendency of stress to reduce leaf chlorophyll concentration.

Effects of high salinity from desalination brine on growth, photosynthesis, water relations and osmolyte concentrations of seagrass Posidonia australis.

PubMed

Cambridge, M L; Zavala-Perez, A; Cawthray, G R; Mondon, J; Kendrick, G A

2017-02-15

Highly saline brines from desalination plants expose seagrass communities to salt stress. We examined effects of raised salinity (46 and 54psu) compared with seawater controls (37psu) over 6weeks on the seagrass, Posidonia australis, growing in tanks with the aim of separating effects of salinity from other potentially deleterious components of brine and determining appropriate bioindicators. Plants survived exposures of 2-4weeks at 54psu, the maximum salinity of brine released from a nearby desalination plant. Salinity significantly reduced maximum quantum yield of PSII (chlorophyll a fluorescence emissions). Leaf water potential (Ψ w ) and osmotic potential (Ψ π ) were more negative at increased salinity, while turgor pressure (Ψ p ) was unaffected. Leaf concentrations of K + and Ca 2+ decreased, whereas concentrations of sugars (mainly sucrose) and amino acids increased. We recommend leaf osmolarity, ion, sugar and amino acid concentrations as bioindicators for salinity effects, associated with brine released in desalination plant outfalls. Copyright © 2016 Elsevier Ltd. All rights reserved.

Monocot Leaves are Eaten Less than Dicot Leaves in Tropical Lowland Rain Forests: Correlations with Toughness and Leaf Presentation

PubMed Central

Grubb, Peter J.; Jackson, Robyn V.; Barberis, Ignacio M.; Bee, Jennie N.; Coomes, David A.; Dominy, Nathaniel J.; De La Fuente, Marie Ann S.; Lucas, Peter W.; Metcalfe, Daniel J.; Svenning, Jens-Christian; Turner, Ian M.; Vargas, Orlando

2008-01-01

Background and Aims In tropical lowland rain forest (TLRF) the leaves of most monocots differ from those of most dicots in two ways that may reduce attack by herbivores. Firstly, they are tougher. Secondly, the immature leaves are tightly folded or rolled until 50–100 % of their final length. It was hypothesized that (a) losses of leaf area to herbivorous invertebrates are generally greatest during leaf expansion and smaller for monocots than for dicots, and (b) where losses after expansion are appreciable any difference between monocots and dicots then is smaller than that found during expansion. Methods At six sites on four continents, estimates were made of lamina area loss from the four most recently mature leaves of focal monocots and of the nearest dicot shoot. Measurements of leaf mass per unit area, and the concentrations of water and nitrogen were made for many of the species. In Panama, the losses from monocots (palms) and dicots were also measured after placing fully expanded palm leaflets and whole dicot leaves on trails of leaf-cutter ants. Key Results At five of six sites monocots experienced significantly smaller leaf area loss than dicots. The results were not explicable in terms of leaf mass per unit area, or concentrations of water or nitrogen. At only one site was the increase in loss from first to fourth mature leaf significant (also large and the same in monocots and dicots), but the losses sustained during expansion were much smaller in the monocots. In the leaf-cutter ant experiment, losses were much smaller for palms than for dicots. Conclusions The relationship between toughness and herbivory is complex; despite the negative findings of some recent authors for dicots we hypothesize that either greater toughness or late folding can protect monocot leaves against herbivorous insects in tropical lowland rain forest, and that the relative importance varies widely with species. The difficulties of establishing unequivocally the roles of leaf toughness and leaf folding or rolling in a given case are discussed. PMID:18387972

High resolution imaging of subcellular glutathione concentrations by quantitative immunoelectron microscopy in different leaf areas of Arabidopsis

PubMed Central

Koffler, Barbara E.; Bloem, Elke; Zellnig, Günther; Zechmann, Bernd

2013-01-01

Glutathione is an important antioxidant and redox buffer in plants. It fulfills many important roles during plant development, defense and is essential for plant metabolism. Even though the compartment specific roles of glutathione during abiotic and biotic stress situations have been studied in detail there is still great lack of knowledge about subcellular glutathione concentrations within the different leaf areas at different stages of development. In this study a method is described that allows the calculation of compartment specific glutathione concentrations in all cell compartments simultaneously in one experiment by using quantitative immunogold electron microscopy combined with biochemical methods in different leaf areas of Arabidopsis thaliana Col-0 (center of the leaf, leaf apex, leaf base and leaf edge). The volume of subcellular compartments in the mesophyll of Arabidopsis was found to be similar to other plants. Vacuoles covered the largest volume within a mesophyll cell and increased with leaf age (up to 80% in the leaf apex of older leaves). Behind vacuoles, chloroplasts covered the second largest volume (up to 20% in the leaf edge of the younger leaves) followed by nuclei (up to 2.3% in the leaf edge of the younger leaves), mitochondria (up to 1.6% in the leaf apex of the younger leaves), and peroxisomes (up to 0.3% in the leaf apex of the younger leaves). These values together with volumes of the mesophyll determined by stereological methods from light and electron micrographs and global glutathione contents measured with biochemical methods enabled the determination of subcellular glutathione contents in mM. Even though biochemical investigations did not reveal differences in global glutathione contents, compartment specific differences could be observed in some cell compartments within the different leaf areas. Highest concentrations of glutathione were always found in mitochondria, where values in a range between 8.7 mM (in the apex of younger leaves) and 15.1 mM (in the apex of older leaves) were found. The second highest amount of glutathione was found in nuclei (between 5.5 mM and 9.7 mM in the base and the center of younger leaves, respectively) followed by peroxisomes (between 2.6 mM in the edge of younger leaves and 4.8 mM in the base of older leaves, respectively) and the cytosol (2.8 mM in the edge of younger and 4.5 mM in the center of older leaves, respectively). Chloroplasts contained rather low amounts of glutathione (between 1 mM and 1.4 mM). Vacuoles had the lowest concentrations of glutathione (0.01 mM and 0.14 mM) but showed large differences between the different leaf areas. Clear differences in glutathione contents between the different leaf areas could only be found in vacuoles and mitochondria revealing that glutathione in the later cell organelle accumulated with leaf age to concentrations of up to 15 mM and that concentrations of glutathione in vacuoles are quite low in comparison to the other cell compartments. PMID:23265941

Spatial distribution of galls caused by Aculus tetanothrix (Acari: Eriophyoidea) on arctic willows.

PubMed

Kuczyński, Lechosław; Skoracka, Anna

2005-01-01

The distribution of galls caused by Aculus tetanothrix (Acari: Eriophyoidea) on three Salix species was studied. The factors influencing this distribution were analysed, i.e. willow species, study area and shoot length. Spatial pattern of gall distribution within the shoot was also examined. The study was conducted in Russia, Kola Peninsula. Densities of galls caused by A. tetanothrix differed significantly among willow species. Considerably higher gall density was recorded in the White Sea coast than in the Khibiny Mountains. This may be explained by the influence of a milder maritime climate that favors mite occurrence compared to a harsh and variable mountain climate that limits mite abundance. There was no relationship between the gall density and the shoot length. The highest density of galls was recorded on the inner offshoots; within the offshoot, there was a maximum density on the fifth leaf. This pattern was repeatable for all shoots studied, independent of the study area, willow species and length of shoots, suggesting the optimal conditions for A. tetanothrix exist on leaves in the middle part of a shoot. This distribution pattern may be an effect of the trade-off between the costs and benefits resulting from leaf quality and mite movement along the shoot. This hypothesis, however, needs to be tested experimentally.

Leaf trait dissimilarities between Dutch elm hybrids with a contrasting tolerance to Dutch elm disease.

PubMed

Durkovic, Jaroslav; Canová, Ingrid; Lagana, Rastislav; Kucerová, Veronika; Moravcík, Michal; Priwitzer, Tibor; Urban, Josef; Dvorák, Milon; Krajnáková, Jana

2013-02-01

Previous studies have shown that Ophiostoma novo-ulmi, the causative agent of Dutch elm disease (DED), is able to colonize remote areas in infected plants of Ulmus such as the leaf midrib and secondary veins. The objective of this study was to compare the performances in leaf traits between two Dutch elm hybrids 'Groeneveld' and 'Dodoens' which possess a contrasting tolerance to DED. Trait linkages were also tested with leaf mass per area (LMA) and with the reduced Young's modulus of elasticity (MOE) as a result of structural, developmental or functional linkages. Measurements and comparisons were made of leaf growth traits, primary xylem density components, gas exchange variables and chlorophyll a fluorescence yields between mature plants of 'Groeneveld' and 'Dodoens' grown under field conditions. A recently developed atomic force microscopy technique, PeakForce quantitative nanomechanical mapping, was used to reveal nanomechanical properties of the cell walls of tracheary elements such as MOE, adhesion and dissipation. 'Dodoens' had significantly higher values for LMA, leaf tissue thickness variables, tracheary element lumen area (A), relative hydraulic conductivity (RC), gas exchange variables and chlorophyll a fluorescence yields. 'Groeneveld' had stiffer cell walls of tracheary elements, and higher values for water-use efficiency and leaf water potential. Leaves with a large carbon and nutrient investment in LMA tended to have a greater leaf thickness and a higher net photosynthetic rate, but LMA was independent of RC. Significant linkages were also found between the MOE and some vascular traits such as RC, A and the number of tracheary elements per unit area. Strong dissimilarities in leaf trait performances were observed between the examined Dutch elm hybrids. Both hybrids were clearly separated from each other in the multivariate leaf trait space. Leaf growth, vascular and gas exchange traits in the infected plants of 'Dodoens' were unaffected by the DED fungus. 'Dodoens' proved to be a valuable elm germplasm for further breeding strategies.

Seasonal variation of temperature response of respiration in invasive Berberis thunbergii (Japanese barberry) and two co-occurring native understory shrubs in a northeastern US deciduous forest.

PubMed

Xu, Cheng-Yuan; Schuster, W S F; Griffin, Kevin L

2007-10-01

In the understory of a closed forest, plant growth is limited by light availability, and early leafing is proposed to be an important mechanism of plant invasion by providing a spring C "subsidy" when high light is available. However, studies on respiration, another important process determining plant net C gain, are rare in understory invasive plants. In this study, leaf properties and the temperature response of leaf respiration were compared between invasive Berberis thunbergii, an early leafing understory shrub, and two native shrubs, Kalmia latifolia, a broadleaf evergreen and Vaccinium corymbosum, a late-leafing deciduous species, in an oak-dominated deciduous forest. The seasonal trend of the basal respiration rates (R(0)) and the temperature response coefficient (E(0)), were different among the three shrubs and species-specific negative correlations were observed between R(0) and E(0). All three shrubs showed significant correlation between respiration rate on an area basis (20 degrees C) and leaf N on an area basis. The relationship was attributed to the variation of both leaf N on a mass basis and leaf mass per area (LMA) in B. thunbergii, but to LMA only in K. latifolia and V. corymbosum. After modeling leaf respiration throughout 2004, B. thunbergii displayed much higher annual leaf respiration (mass based) than the two native shrubs, indicating a higher cost per unit of biomass investment. Thus, respiratory properties alone were not likely to lead to C balance advantage of B. thunbergii. Future studies on whole plant C budgets and leaf construction cost are needed to address the C balance advantage in early leafing understory shrubs like B. thunbergii.

Plasticity in seedling morphology, biomass allocation and physiology among ten temperate tree species in response to shade is related to shade tolerance and not leaf habit.

PubMed

Chmura, D J; Modrzyński, J; Chmielarz, P; Tjoelker, M G

2017-03-01

Mechanisms of shade tolerance in tree seedlings, and thus growth in shade, may differ by leaf habit and vary with ontogeny following seed germination. To examine early responses of seedlings to shade in relation to morphological, physiological and biomass allocation traits, we compared seedlings of 10 temperate species, varying in their leaf habit (broadleaved versus needle-leaved) and observed tolerance to shade, when growing in two contrasting light treatments - open (about 20% of full sunlight) and shade (about 5% of full sunlight). We analyzed biomass allocation and its response to shade using allometric relationships. We also measured leaf gas exchange rates and leaf N in the two light treatments. Compared to the open treatment, shading significantly increased traits typically associated with high relative growth rate (RGR) - leaf area ratio (LAR), specific leaf area (SLA), and allocation of biomass into leaves, and reduced seedling mass and allocation to roots, and net assimilation rate (NAR). Interestingly, RGR was not affected by light treatment, likely because of morphological and physiological adjustments in shaded plants that offset reductions of in situ net assimilation of carbon in shade. Leaf area-based rates of light-saturated leaf gas exchange differed among species groups, but not between light treatments, as leaf N concentration increased in concert with increased SLA in shade. We found little evidence to support the hypothesis of a increased plasticity of broadleaved species compared to needle-leaved conifers in response to shade. However, an expectation of higher plasticity in shade-intolerant species than in shade-tolerant ones, and in leaf and plant morphology than in biomass allocation was supported across species of contrasting leaf habit. © 2016 German Botanical Society and The Royal Botanical Society of the Netherlands.

Identification and molecular characterization of a new recombinant begomovirus and associated betasatellite DNA infecting Capsicum annuum in India.

PubMed

Bhatt, Bhavin S; Chahwala, Fenisha D; Rathod, Sangeeta; Singh, Achuit K

2016-05-01

Capsicum annuum (Chilli) is a perennial herbaceous plant that is cultivated as an annual crop throughout the world, including India. Chilli leaf curl disease (ChiLCD) is a major biotic constraint, causing major losses in chilli production. During 2014, leaf samples of chilli plants displaying leaf curl disease were collected from the Ahmedabad district of Gujarat, India. These samples were used to isolate, clone and sequence viral genomic DNA and an associated betasatellite DNA molecule. Sequence analysis showed 90.4 % nucleotide sequence identity to the previously reported chilli leaf curl virus-[India:Guntur:2009] (ChiLCV-[IN:Gun:09]. As per ICTV nomenclature rules, ChiLCV-Ahm represents a new species of begomovirus, and we therefore propose the name chilli leaf curl Ahmedabad virus-[India:Ahmedabad:2014] (ChiLCAV-[IN:Ahm:14]). The associated betasatellite DNA showed a maximum of 93.5 % nucleotide sequence identity to a previously reported tomato leaf curl Bangladesh betasatellite and may be named tomato leaf curl Bangladesh betasatellite-[India:Ahmedabad:Chilli:2014].

Leaf Mass Area, Leaf Carbon and Nitrogen Content, Kougarok Road and Teller Road, Seward Peninsula, Alaska, 2016

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shawn Serbin; Alistair Rogers; Kim Ely

Carbon, Nitrogen and Leaf Mass Area of leaves sampled from locations on the Kougarok Rd (transect A) and Teller Rd NGEE Arctic study sites, Seward Peninsula, Alaska. Species include: Alnus viridis spp. fruticosa, Arctostaphylos rubra, Betula glandulosa, Chamerion latifolium, Petasites frigidus, Salix alaxensis, Salix glauca, Salix pulchra, Salix richardsonii and Vaccinium uliginosum.

Structural assessment of the impact of environmental constraints on Arabidopsis thaliana leaf growth: a 3D approach.

PubMed

Wuyts, Nathalie; Massonnet, Catherine; Dauzat, Myriam; Granier, Christine

2012-09-01

Light and soil water content affect leaf surface area expansion through modifications in epidermal cell numbers and area, while effects on leaf thickness and mesophyll cell volumes are far less documented. Here, three-dimensional imaging was applied in a study of Arabidopsis thaliana leaf growth to determine leaf thickness and the cellular organization of mesophyll tissues under moderate soil water deficit and two cumulative light conditions. In contrast to surface area, thickness was highly conserved in response to water deficit under both low and high cumulative light regimes. Unlike epidermal and palisade mesophyll tissues, no reductions in cell number were observed in the spongy mesophyll; cells had rather changed in volume and shape. Furthermore, leaf features of a selection of genotypes affected in leaf functioning were analysed. The low-starch mutant pgm had very thick leaves because of unusually large palisade mesophyll cells, together with high levels of photosynthesis and stomatal conductance. By means of an open stomata mutant and a 9-cis-epoxycarotenoid dioxygenase overexpressor, it was shown that stomatal conductance does not necessarily have a major impact on leaf dimensions and cellular organization, pointing to additional mechanisms for the control of CO(2) diffusion under high and low stomatal conductance, respectively. © 2012 Blackwell Publishing Ltd.

[The analysis of the causes of variability of the relationship between leaf dry mass and area in plants].

PubMed

Vasfilov, S P

2011-01-01

The lamina dry mass: area ratio (LMA - Leaf Mass per Area) is a quite variable trait. Leaf dry mass consists of symplast mass (a set of all leaf protoplasts) and apoplast mass (a set of all cell walls in a leaf). The ratio between symplast and apoplast masses is positively related to any functional trait of leaf calculated per unit of dry mass. The value of this ratio is defined by cells size and their number per unit of leaf area, number of mesophyll cells layers and their differentiation between palisade and spongy ones, and also by density of cells packing. The LMA value is defined by leaf thickness and density. The extent and direction of variability in both leaf traits define the extent and direction of variability in LMA. Negative correlation between leaf thickness and density reduces the level of LMA variability. As a consequence of this correlation the following pattern emerges: the thinner a leaf, the denser it is. Changes in the traits that define the LMA value take place both within a species under the influence of environmental factors and between species that differ in leaf structure and functions. Light is the most powerful environmental factor that influences the LMA, increase in illumination leading to increase in LMA. This effect occurs during leaf growth at the expense of structural changes associated with the reduction of symplast/apoplast mass ratio. Under conditions of intense illumination, LMA may increase due to accumulation of starch. With regard to the majority of leaf functions, the mass of starch may be ascribed to apoplast. Starch accumulation in leaves is observed also under conditions of elevated CO2 concentration in the air. Under high illumination, however, LMA increases also due to increased apoplast contribution to leaf dry mass. Scarce mineral nutrition leads to LMA increase due to lowering of growth zones demands for phothosyntates and, therefore, to increase in starch content of leaves. High level of mineral nutrition during leaf growth period leads to LMA increase at the expense of mesophyll thickening where components of photosynthesis system are located. When additional environmental factors are involved, starch accumulation may be partly responsible for increase in LMA. LMA increase at the expense of starch accumulation, unlike that at the expense of mesophyll thickening, is accompanied by increased leaf density. Under conditions of water deficiency LMA increases, which in mature leaf may be caused by starch accumulation. LMA increase during leaf growth period under conditions of water deficiency is associated with decrease in the symplast/apoplast mass ratio.

[Foliar water use efficiency of Platycladus orientalis sapling under different soil water contents].

PubMed

Zhang, Yong E; Yu, Xin Xiao; Chen, Li Hua; Jia, Guo Dong; Zhao, Na; Li, Han Zhi; Chang, Xiao Min

2017-07-18

The determination of plant foliar water use efficiency will be of great value to improve our understanding about mechanism of plant water consumption and provide important basis of regional forest ecosystem management and maintenance, thus, laboratory controlled experiments were carried out to obtain Platycladus orientalis sapling foliar water use efficiency under five different soil water contents, including instantaneous water use efficiency (WUE gs ) derived from gas exchange and short-term water use efficiency (WUE cp ) caculated using carbon isotope model. The results showed that, controlled by stomatal conductance (g s ), foliar net photosynthesis rate (P n ) and transpiration rate (T r ) increased as soil water content increased, which both reached maximum va-lues at soil water content of 70%-80% field capacity (FC), while WUE gs reached a maximum of 7.26 mmol·m -2 ·s -1 at the lowest soil water content (35%-45% FC). Both δ 13 C of water-soluble leaf and twig phloem material achieved maximum values at the lowest soil water content (35%-45% FC). Besides, δ 13 C values of leaf water-soluble compounds were significantly greater than that of phloem exudates, indicating that there was depletion in 13 C in twig phloem compared with leaf water-soluble compounds and no obvious fractionation in the process of water-soluble material transportation from leaf to twig. Foliar WUE cp also reached a maximum of 7.26 mmol·m -2 ·s -1 at the lowest soil water content (35%-45% FC). There was some difference between foliar WUE gs and WUE cp under the same condition, and the average difference was 0.52 mmol·m -2 ·s -1 . The WUE gs had great space-time variability, by contrast, WUE cp was more representative. It was concluded that P. orientalis sapling adapted to drought condition by increasing water use efficiency and decreasing physiological activity.

Changes in water content and distribution in Quercus ilex leaves during progressive drought assessed by in vivo 1H magnetic resonance imaging

PubMed Central

2010-01-01

Background Drought is a common stressor in many regions of the world and current climatic global circulation models predict further increases in warming and drought in the coming decades in several of these regions, such as the Mediterranean basin. The changes in leaf water content, distribution and dynamics in plant tissues under different soil water availabilities are not well known. In order to fill this gap, in the present report we describe our study withholding the irrigation of the seedlings of Quercus ilex, the dominant tree species in the evergreen forests of many areas of the Mediterranean Basin. We have monitored the gradual changes in water content in the different leaf areas, in vivo and non-invasively, by 1H magnetic resonance imaging (MRI) using proton density weighted (ρw) images and spin-spin relaxation time (T2) maps. Results ρw images showed that the distal leaf area lost water faster than the basal area and that after four weeks of similar losses, the water reduction was greater in leaf veins than in leaf parenchyma areas and also in distal than in basal leaf area. There was a similar tendency in all different areas and tissues, of increasing T2 values during the drought period. This indicates an increase in the dynamics of free water, suggesting a decrease of cell membranes permeability. Conclusions The results indicate a non homogeneous leaf response to stress with a differentiated capacity to mobilize water between its different parts and tissues. This study shows that the MRI technique can be a useful tool to follow non-intrusively the in vivo water content changes in the different parts of the leaves during drought stress. It opens up new possibilities to better characterize the associated physiological changes and provides important information about the different responses of the different leaf areas what should be taken into account when conducting physiological and metabolic drought stress studies in different parts of the leaves during drought stress. PMID:20735815

Changes in water content and distribution in Quercus ilex leaves during progressive drought assessed by in vivo 1H magnetic resonance imaging.

PubMed

Sardans, Jordi; Peñuelas, Josep; Lope-Piedrafita, Silvia

2010-08-24

Drought is a common stressor in many regions of the world and current climatic global circulation models predict further increases in warming and drought in the coming decades in several of these regions, such as the Mediterranean basin. The changes in leaf water content, distribution and dynamics in plant tissues under different soil water availabilities are not well known. In order to fill this gap, in the present report we describe our study withholding the irrigation of the seedlings of Quercus ilex, the dominant tree species in the evergreen forests of many areas of the Mediterranean Basin. We have monitored the gradual changes in water content in the different leaf areas, in vivo and non-invasively, by 1H magnetic resonance imaging (MRI) using proton density weighted (rhow) images and spin-spin relaxation time (T2) maps. Rhow images showed that the distal leaf area lost water faster than the basal area and that after four weeks of similar losses, the water reduction was greater in leaf veins than in leaf parenchyma areas and also in distal than in basal leaf area. There was a similar tendency in all different areas and tissues, of increasing T2 values during the drought period. This indicates an increase in the dynamics of free water, suggesting a decrease of cell membranes permeability. The results indicate a non homogeneous leaf response to stress with a differentiated capacity to mobilize water between its different parts and tissues. This study shows that the MRI technique can be a useful tool to follow non-intrusively the in vivo water content changes in the different parts of the leaves during drought stress. It opens up new possibilities to better characterize the associated physiological changes and provides important information about the different responses of the different leaf areas what should be taken into account when conducting physiological and metabolic drought stress studies in different parts of the leaves during drought stress.

Separating foliar physiology from morphology reveals the relative roles of vertically structured transpiration factors within red maple crowns and limitations of larger scale models

PubMed Central

Bauerle, William L.; Bowden, Joseph D.

2011-01-01

A spatially explicit mechanistic model, MAESTRA, was used to separate key parameters affecting transpiration to provide insights into the most influential parameters for accurate predictions of within-crown and within-canopy transpiration. Once validated among Acer rubrum L. genotypes, model responses to different parameterization scenarios were scaled up to stand transpiration (expressed per unit leaf area) to assess how transpiration might be affected by the spatial distribution of foliage properties. For example, when physiological differences were accounted for, differences in leaf width among A. rubrum L. genotypes resulted in a 25% difference in transpiration. An in silico within-canopy sensitivity analysis was conducted over the range of genotype parameter variation observed and under different climate forcing conditions. The analysis revealed that seven of 16 leaf traits had a ≥5% impact on transpiration predictions. Under sparse foliage conditions, comparisons of the present findings with previous studies were in agreement that parameters such as the maximum Rubisco-limited rate of photosynthesis can explain ∼20% of the variability in predicted transpiration. However, the spatial analysis shows how such parameters can decrease or change in importance below the uppermost canopy layer. Alternatively, model sensitivity to leaf width and minimum stomatal conductance was continuous along a vertical canopy depth profile. Foremost, transpiration sensitivity to an observed range of morphological and physiological parameters is examined and the spatial sensitivity of transpiration model predictions to vertical variations in microclimate and foliage density is identified to reduce the uncertainty of current transpiration predictions. PMID:21617246

Gas exchange and hydraulics in seedlings of Hevea brasiliensis during water stress and recovery.

PubMed

Chen, Jun-Wen; Zhang, Qiang; Li, Xiao-Shuang; Cao, Kun-Fang

2010-07-01

The response of plants to drought has received significant attention, but far less attention has been given to the dynamic response of plants during recovery from drought. Photosynthetic performance and hydraulic capacity were monitored in seedlings of Hevea brasiliensis under water stress and during recovery following rewatering. Leaf water relation, gas exchange rate and hydraulic conductivity decreased gradually after water stress fell below a threshold, whereas instantaneous water use efficiency and osmolytes increased significantly. After 5 days of rewatering, leaf water relation, maximum stomatal conductance (g(s-max)) and plant hydraulic conductivity had recovered to the control levels except for sapwood area-specific hydraulic conductivity, photosynthetic assimilation rate and osmolytes. During the phase of water stress, stomata were almost completely closed before water transport efficiency decreased substantially, and moreover, the leaf hydraulic pathway was more vulnerable to water stress-induced embolism than the stem hydraulic pathway. Meanwhile, g(s-max) was linearly correlated with hydraulic capacity when water stress exceeded a threshold. In addition, a positive relationship was shown to occur between the recovery of g(s-max) and of hydraulic capacity during the phase of rewatering. Our results suggest (i) that stomatal closure effectively reduces the risk of xylem dysfunction in water-stressed plants at the cost of gas exchange, (ii) that the leaf functions as a safety valve to protect the hydraulic pathway from water stress-induced dysfunction to a larger extent than does the stem and (iii) that the full drought recovery of gas exchange is restricted by not only hydraulic factors but also non-hydraulic factors.

Provenance effect on carbon assimilation, photochemistry and leaf morphology in Mediterranean Cistus species under chilling stress.

PubMed

Puglielli, G; Cuevas Román, F J; Catoni, R; Moreno Rojas, J M; Gratani, L; Varone, L

2017-07-01

The potential resilience of shrub species to environmental change deserves attention in those areas threatened by climate change, such as the Mediterranean Basin. We asked if leaves produced under different climate conditions through the winter season to spring can highlight the leaf traits involved in determining potential resilience of three Cistus spp. to changing environmental conditions and to what extent intraspecific differences affect such a response. We analysed carbon assimilation, maximum quantum efficiency of PSII photochemistry (F v /F m ) and leaf morphological control of the photosynthetic process in leaves formed through the winter season into spring in C. creticus subsp. eriocephalus (CE), C. salvifolius (CS) and C. monspeliensis (CM) grown from seed of different provenances under common garden conditions. Intraspecific differences were found in F v /F m for CE and CS. Carbon assimilation-related parameters were not affected by provenance. Moreover, our analysis highlighted that the functional relationships investigated can follow seasonal changes and revealed patterns originating from species-specific differences in LMA arising during the favourable period. Cistus spp. have great ability to modify the structure and function of their leaves in the mid-term in order to cope with changing environmental conditions. The F v /F m response to chilling reveals that susceptibility to photoinhibition is a trait under selection in Cistus species. Concerning carbon assimilation, differing ability to control stomatal opening was highlighted between species. Moreover, seasonal changes of the functional relationships investigated can have predictable consequences on species leaf turnover strategies. © 2017 German Botanical Society and The Royal Botanical Society of the Netherlands.

Relationships between stem diameter, sapwood area, leaf area and transpiration in a young mountain ash forest.

PubMed

Vertessy, R A; Benyon, R G; O'Sullivan, S K; Gribben, P R

1995-09-01

We examined relationships between stem diameter, sapwood area, leaf area and transpiration in a 15-year-old mountain ash (Eucalyptus regnans F. Muell.) forest containing silver wattle (Acacia dealbata Link.) as a suppressed overstory species and mountain hickory (Acacia frigescens J.H. Willis) as an understory species. Stem diameter explained 93% of the variation in leaf area, 96% of the variation in sapwood area and 88% of the variation in mean daily spring transpiration in 19 mountain ash trees. In seven silver wattle trees, stem diameter explained 87% of the variation in sapwood area but was a poor predictor of the other variables. When transpiration measurements from individual trees were scaled up to a plot basis, using stem diameter values for 164 mountain ash trees and 124 silver wattle trees, mean daily spring transpiration rates of the two species were 2.3 and 0.6 mm day(-1), respectively. The leaf area index of the plot was estimated directly by destructive sampling, and indirectly with an LAI-2000 plant canopy analyzer and by hemispherical canopy photography. All three methods gave similar results.

A comparison of hydraulic architecture in three similarly sized woody species differing in their maximum potential height.

PubMed

McCulloh, Katherine A; Johnson, Daniel M; Petitmermet, Joshua; McNellis, Brandon; Meinzer, Frederick C; Lachenbruch, Barbara

2015-07-01

The physiological mechanisms underlying the short maximum height of shrubs are not understood. One possible explanation is that differences in the hydraulic architecture of shrubs compared with co-occurring taller trees prevent the shrubs from growing taller. To explore this hypothesis, we examined various hydraulic parameters, including vessel lumen diameter, hydraulic conductivity and vulnerability to drought-induced embolism, of three co-occurring species that differed in their maximum potential height. We examined one species of shrub, one short-statured tree and one taller tree. We worked with individuals that were approximately the same age and height, which was near the maximum for the shrub species. A number of variables correlated with the maximum potential height of the species. For example, vessel diameter and vulnerability to embolism both increased while wood density declined with maximum potential height. The difference between the pressure causing 50% reduction in hydraulic conductance in the leaves and the midday leaf water potential (the leaf's hydraulic safety margin) was much larger in the shrub than the other two species. In general, trends were consistent with understory shrubs having a more conservative life history strategy than co-occurring taller species. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Correlated variation of floral and leaf traits along a moisture availability gradient.

PubMed

Lambrecht, Susan C; Dawson, Todd E

2007-04-01

Variation in flower size is an important aspect of a plant's life history, yet few studies have shown how flower size varies with environmental conditions and to what extent foliar responses to the environment are correlated with flower size. The objectives of this study were to (1) develop a theoretical framework for linking flower size and leaf size to their costs and benefits, as assessed using foliar stable carbon isotope ratio (delta(13)C) under varying degrees of water limitation, and then (2) examine how variation in flower size within and among species growing along a naturally occurring moisture availability gradient correlates with variation in delta(13)C and leaf size. Five plant species were examined at three sites in Oregon. Intra- and inter-specific patterns of flower size in relation to moisture availability were the same: the ratios of the area of flower display to total leaf area and of individual flower area to leaf area were greater at sites with more soil moisture compared to those sites with less soil moisture. The increase in flower area per unit increase in leaf area was greater at sites with more soil moisture than at sites where water deficit can occur. Values of delta(13)C, an index of water-use efficiency, were greater for plants with larger floral size. The patterns we observed generalize across species, irrespective of overall plant morphology or pollination system. These correlations between flower size, moisture availability, and delta(13)C suggest that water loss from flowers can influence leaf responses to the environment, which in turn may indirectly mediate an effect on flower size.

The importance of hydraulic architecture to the distribution patterns of trees in a central Amazonian forest.

PubMed

Cosme, Luiza H M; Schietti, Juliana; Costa, Flávia R C; Oliveira, Rafael S

2017-07-01

Species distributions and assemblage composition may be the result of trait selection through environmental filters. Here, we ask whether filtering of species at the local scale could be attributed to their hydraulic architectural traits, revealing the basis of hydrological microhabitat partitioning in a Central Amazonian forest. We analyzed the hydraulic characteristics at tissue (anatomical traits, wood specific gravity (WSG)), organ (leaf area, specific leaf area (SLA), leaf area : sapwood area ratio) and whole-plant (height) levels for 28 pairs of congeneric species from 14 genera restricted to either valleys or plateaus of a terra-firme forest in Central Amazonia. On plateaus, species had higher WSG, but lower mean vessel area, mean vessel hydraulic diameter, sapwood area and SLA than in valleys; traits commonly associated with hydraulic safety. Mean vessel hydraulic diameter and mean vessel area increased with height for both habitats, but leaf area and leaf area : sapwood area ratio investments with tree height declined in valley vs plateau species. [Correction added after online publication 29 March 2017: the preceding sentence has been reworded.] Two strategies for either efficiency or safety were detected, based on vessel size or allocation to sapwood. In conclusion, contrasting hydrological conditions act as environmental filters, generating differences in species composition at the local scale. This has important implications for the prediction of species distributions under future climate change scenarios. © 2017 The Authors. New Phytologist © 2017 New Phytologist Trust.

Dynamics of leaf hydraulic conductance with water status: quantification and analysis of species differences under steady state

PubMed Central

Scoffoni, Christine; McKown, Athena D.; Rawls, Michael; Sack, Lawren

2012-01-01

Leaf hydraulic conductance (Kleaf) is a major determinant of photosynthetic rate in well-watered and drought-stressed plants. Previous work assessed the decline of Kleaf with decreasing leaf water potential (Ψleaf), most typically using rehydration kinetics methods, and found that species varied in the shape of their vulnerability curve, and that hydraulic vulnerability correlated with other leaf functional traits and with drought sensitivity. These findings were tested and extended, using a new steady-state evaporative flux method under high irradiance, and the function for the vulnerability curve of each species was determined individually using maximum likelihood for 10 species varying strongly in drought tolerance. Additionally, the ability of excised leaves to recover in Kleaf with rehydration was assessed, and a new theoretical framework was developed to estimate how rehydration of measured leaves may affect estimation of hydraulic parameters. As hypothesized, species differed in their vulnerability function. Drought-tolerant species showed shallow linear declines and more negative Ψleaf at 80% loss of Kleaf (P80), whereas drought-sensitive species showed steeper, non-linear declines, and less negative P80. Across species, the maximum Kleaf was independent of hydraulic vulnerability. Recovery of Kleaf after 1 h rehydration of leaves dehydrated below their turgor loss point occurred only for four of 10 species. Across species without recovery, a more negative P80 correlated with the ability to maintain Kleaf through both dehydration and rehydration. These findings indicate that resistance to Kleaf decline is important not only in maintaining open stomata during the onset of drought, but also in enabling sustained function during drought recovery. PMID:22016424

Leaf photosynthesis and respiration of three bioenergy crops in relation to temperature and leaf nitrogen: how conserved are biochemical model parameters among crop species?

PubMed Central

Archontoulis, S. V.; Yin, X.; Vos, J.; Danalatos, N. G.; Struik, P. C.

2012-01-01

Given the need for parallel increases in food and energy production from crops in the context of global change, crop simulation models and data sets to feed these models with photosynthesis and respiration parameters are increasingly important. This study provides information on photosynthesis and respiration for three energy crops (sunflower, kenaf, and cynara), reviews relevant information for five other crops (wheat, barley, cotton, tobacco, and grape), and assesses how conserved photosynthesis parameters are among crops. Using large data sets and optimization techniques, the C3 leaf photosynthesis model of Farquhar, von Caemmerer, and Berry (FvCB) and an empirical night respiration model for tested energy crops accounting for effects of temperature and leaf nitrogen were parameterized. Instead of the common approach of using information on net photosynthesis response to CO2 at the stomatal cavity (An–Ci), the model was parameterized by analysing the photosynthesis response to incident light intensity (An–Iinc). Convincing evidence is provided that the maximum Rubisco carboxylation rate or the maximum electron transport rate was very similar whether derived from An–Ci or from An–Iinc data sets. Parameters characterizing Rubisco limitation, electron transport limitation, the degree to which light inhibits leaf respiration, night respiration, and the minimum leaf nitrogen required for photosynthesis were then determined. Model predictions were validated against independent sets. Only a few FvCB parameters were conserved among crop species, thus species-specific FvCB model parameters are needed for crop modelling. Therefore, information from readily available but underexplored An–Iinc data should be re-analysed, thereby expanding the potential of combining classical photosynthetic data and the biochemical model. PMID:22021569

An evolutionary attractor model for sapwood cross section in relation to leaf area.

PubMed

Westoby, Mark; Cornwell, William K; Falster, Daniel S

2012-06-21

Sapwood cross-sectional area per unit leaf area (SA:LA) is an influential trait that plants coordinate with physical environment and with other traits. We develop theory for SA:LA and also for root surface area per leaf area (RA:LA) on the premise that plants maximizing the surplus of revenue over costs should have competitive advantage. SA:LA is predicted to increase in water-relations environments that reduce photosynthetic revenue, including low soil water potential, high water vapor pressure deficit (VPD), and low atmospheric CO(2). Because sapwood has costs, SA:LA adjustment does not completely offset difficult water relations. Where sapwood costs are large, as in tall plants, optimal SA:LA may actually decline with (say) high VPD. Large soil-to-root resistance caps the benefits that can be obtained from increasing SA:LA. Where a plant can adjust water-absorbing surface area of root per leaf area (RA:LA) as well as SA:LA, optimal RA:SA is not affected by VPD, CO(2) or plant height. If selection favours increased height more so than increased revenue-minus-cost, then height is predicted to rise substantially under improved water-relations environments such as high-CO(2) atmospheres. Evolutionary-attractor theory for SA:LA and RA:LA complements models that take whole-plant conductivity per leaf area as a parameter. Copyright © 2012 Elsevier Ltd. All rights reserved.

The optimal atmospheric CO2 concentration for the growth of winter wheat (Triticum aestivum).

PubMed

Xu, Ming

2015-07-20

This study examined the optimal atmospheric CO2 concentration of the CO2 fertilization effect on the growth of winter wheat with growth chambers where the CO2 concentration was controlled at 400, 600, 800, 1000, and 1200 ppm respectively. I found that initial increase in atmospheric CO2 concentration dramatically enhanced winter wheat growth through the CO2 fertilization effect. However, this CO2 fertilization effect was substantially compromised with further increase in CO2 concentration, demonstrating an optimal CO2 concentration of 889.6, 909.4, and 894.2 ppm for aboveground, belowground, and total biomass, respectively, and 967.8 ppm for leaf photosynthesis. Also, high CO2 concentrations exceeding the optima not only reduced leaf stomatal density, length and conductance, but also changed the spatial distribution pattern of stomata on leaves. In addition, high CO2 concentration also decreased the maximum carboxylation rate (Vc(max)) and the maximum electron transport rate (J(max)) of leaf photosynthesis. However, the high CO2 concentration had little effect on leaf length and plant height. The optimal CO2 fertilization effect found in this study can be used as an indicator in selecting and breeding new wheat strains in adapting to future high atmospheric CO2 concentrations and climate change. Copyright © 2015. Published by Elsevier GmbH.

Converging patterns of vertical variability in leaf morphology and nitrogen across seven Eucalyptus plantations in Brazil and Hawaii, USA

Treesearch

Adam P. Coble; Alisha Autio; Molly A. Cavaleri; Dan Binkley; Michael G. Ryan

2014-01-01

Across sites in Brazil and Hawaii, LMA and Nmass were strongly correlated with height and shade index, respectively, which may help simplify canopy function modeling of Eucalyptus plantations. Abstract Within tree canopies, leaf mass per area (LMA) and leaf nitrogen per unit area (Narea) commonly increase with height. Previous research has suggested that these patterns...

Taxonomy and remote sensing of leaf mass per area (LMA) in humid tropical forests

Treesearch

Gregory P. Asner; Roberta E. Martin; Raul Tupayachi; Ruth Emerson; Paola Martinez; Felipe Sinca; George V.N. Powell; S. Joseph Wright; Ariel E. Lugo

2011-01-01

Leaf mass per area (LMA) is a trait of central importance to plant physiology and ecosystem function, but LMA patterns in the upper canopies of humid tropical forests have proved elusive due to tall species and high diversity. We collected top-of-canopy leaf samples from 2873 individuals in 57 sites spread across the Neotropics, Australasia, and Caribbean and Pacific...

Branch age and light conditions determine leaf-area-specific conductivity in current shoots of Scots pine.

PubMed

Grönlund, Leila; Hölttä, Teemu; Mäkelä, Annikki

2016-08-01

Shoot size and other shoot properties more or less follow the availability of light, but there is also evidence that the topological position in a tree crown has an influence on shoot development. Whether the hydraulic properties of new shoots are more regulated by the light or the position affects the shoot acclimation to changing light conditions and thereby to changing evaporative demand. We investigated the leaf-area-specific conductivity (and its components sapwood-specific conductivity and Huber value) of the current-year shoots of Scots pine (Pinus sylvestris L.) in relation to light environment and topological position in three different tree classes. The light environment was quantified in terms of simulated transpiration and the topological position was quantified by parent branch age. Sample shoot measurements included length, basal and tip diameter, hydraulic conductivity of the shoot, tracheid area and density, and specific leaf area. In our results, the leaf-area-specific conductivity of new shoots declined with parent branch age and increased with simulated transpiration rate of the shoot. The relation to transpiration demand seemed more decisive, since it gave higher R(2) values than branch age and explained the differences between the tree classes. The trend of leaf-area-specific conductivity with simulated transpiration was closely related to Huber value, whereas the trend of leaf-area-specific conductivity with parent branch age was related to a similar trend in sapwood-specific conductivity. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

MINERAL AND BIOCHEMICAL ANALYSIS OF VARIOUS PARTS OF CISSUS QUADRANGULARIS LINN

PubMed Central

Udayakumar, R.; Sundaran, M.; Krishna, Raghuram

2004-01-01

Ash, minerals and biochemical contents were determined in various parts of root, stem and leaf of Cissus quadrangularis. The maximum ash content was observed in the root. The maximum concentration of carbohydrate and protein in the root and phosphorus, iron, calcium and lipids in the stem were observed. PMID:22557157

Coming of Age: Polarization as a Probe of Plant Canopy Water Status

NASA Astrophysics Data System (ADS)

Vanderbilt, V. C.; Daughtry, C. S. T.; Kupinski, M.; Bradley, C. L.; Dahlgren, R. P.

2015-12-01

We tested the hypothesis that the relative water content (RWC) of the sunlit leaves in a plant canopy may be estimated from polarized canopy imagery. Recently (IGARSS, July 27-31, 2015, Milan, Italy), we reported the results of laboratory polarization measurements of single detached leaves during dry down. We found that RWC was linearly related to the ratio of the reflectance of the interior of the leaf and the leaf transmittance. Here we report application of the laboratory results to estimate RWC for sunlit leaves in a plant canopy. Using a commercial-off-the-shelf (COTS) Nikon 810 camera with Nikkor 300 mm lens and Polaroid type HN-22 linear polarizer, we photographed in the principle plane a plant canopy displaying a gradient of water stress and collected, at each of multiple points along the gradient, two images, one with the polarization filter oriented for maximum scene response and a second with the filter oriented for minimum scene response. We converted the digital values in the two images to reflectance factor with reference to images of a white, flat, horizontal Spectralon surface. We classified the polarization imagery, identifying reflecting leaves, transmitting leaves, other sunlit vegetation and shadows. For each image pair we normalized the leaf internal reflectance by dividing by the cosine of the angle of incidence of the sunlight on the leaf, selected the leaf maximum transmittance in the scene and divided to obtain the ratio reflectance/transmittance, which we compared with leaf RWC. We determined the leaf relative water content by harvesting a section of leaf and immediately placing it in a sealed container in an ice chest. Later in the laboratory the leaf sample was weighed, rehydrated, weighed, dried and again weighed. RWC was determined using the standard formula.Our experimental results support our hypothesis, suggesting that the RWC of sunlit leaves in a plant canopy may be estimated from analysis of polarization imagery collected by a COTS camera system. Unlike remotely sensed estimates of canopy equivalent water thickness, our estimates of the RWC of sunlit canopy leaves provide leaf physiological information. We propose RWC estimates based upon sunlit leaves are more relevant to assessing the water status of a plant canopy than would be RWC estimates based upon large FOV canopy measurements.

SU-E-T-613: Dosimetric Consequences of Systematic MLC Leaf Positioning Errors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kathuria, K; Siebers, J

2014-06-01

Purpose: The purpose of this study is to determine the dosimetric consequences of systematic MLC leaf positioning errors for clinical IMRT patient plans so as to establish detection tolerances for quality assurance programs. Materials and Methods: Dosimetric consequences were simulated by extracting mlc delivery instructions from the TPS, altering the file by the specified error, reloading the delivery instructions into the TPS, recomputing dose, and extracting dose-volume metrics for one head-andneck and one prostate patient. Machine error was simulated by offsetting MLC leaves in Pinnacle in a systematic way. Three different algorithms were followed for these systematic offsets, and aremore » as follows: a systematic sequential one-leaf offset (one leaf offset in one segment per beam), a systematic uniform one-leaf offset (same one leaf offset per segment per beam) and a systematic offset of a given number of leaves picked uniformly at random from a given number of segments (5 out of 10 total). Dose to the PTV and normal tissue was simulated. Results: A systematic 5 mm offset of 1 leaf for all delivery segments of all beams resulted in a maximum PTV D98 deviation of 1%. Results showed very low dose error in all reasonably possible machine configurations, rare or otherwise, which could be simulated. Very low error in dose to PTV and OARs was shown in all possible cases of one leaf per beam per segment being offset (<1%), or that of only one leaf per beam being offset (<.2%). The errors resulting from a high number of adjacent leaves (maximum of 5 out of 60 total leaf-pairs) being simultaneously offset in many (5) of the control points (total 10–18 in all beams) per beam, in both the PTV and the OARs analyzed, were similarly low (<2–3%). Conclusions: The above results show that patient shifts and anatomical changes are the main source of errors in dose delivered, not machine delivery. These two sources of error are “visually complementary” and uncorrelated (albeit not additive in the final error) and one can easily incorporate error resulting from machine delivery in an error model based purely on tumor motion.« less

Coming of Age: Polarization as a Probe of Plant Canopy Water Status

NASA Technical Reports Server (NTRS)

Vanderbilt, Vern C.; Daughtry, Craig S. T.; Kupinski, Meredith; Bradley, Christine Lavella; Dahlgren, Robert P.

2015-01-01

We tested the hypothesis that the relative water content (RWC) of the sunlit leaves in a plant canopy may be estimated from polarized canopy imagery. Recently (IGARSS, July 27-31, 2015, Milan, Italy), we reported the results of laboratory polarization measurements of single detached leaves during dry down. We found that RWC was linearly related to the ratio of the reflectance of the interior of the leaf and the leaf transmittance. Here we report application of the laboratory results to estimate RWC for sunlit leaves in a plant canopy. Using a commercial-off-the-shelf (COTS) Nikon 810 camera with Nikkor 300 mm lens and Polaroid type HN-22 linear polarizer, we photographed in the principle plane a plant canopy displaying a gradient of water stress and collected, at each of multiple points along the gradient, two images, one with the polarization filter oriented for maximum scene response and a second with the filter oriented for minimum scene response. We converted the digital values in the two images to reflectance factor with reference to images of a white, flat, horizontal Spectralon surface. We classified the polarization imagery, identifying reflecting leaves, transmitting leaves, other sunlit vegetation and shadows. For each image pair we normalized the leaf internal reflectance by dividing by the cosine of the angle of incidence of the sunlight on the leaf, selected the leaf maximum transmittance in the scene and divided to obtain the ratio reflectance/transmittance, which we compared with leaf RWC. We determined the leaf relative water content by harvesting a section of leaf and immediately placing it in a sealed container in an ice chest. Later in the laboratory the leaf sample was weighed, rehydrated, weighed, dried and again weighed. RWC was determined using the standard formula. Our experimental results support our hypothesis, suggesting that the RWC of sunlit leaves in a plant canopy may be estimated from analysis of polarization imagery collected by a COTS camera system. Unlike remotely sensed estimates of canopy equivalent water thickness, our estimates of the RWC of sunlit canopy leaves provide leaf physiological information. We propose RWC estimates based upon sunlit leaves are more relevant to assessing the water status of a plant canopy than would be RWC estimates based upon large FOV canopy measurements.

Leaf Shrinkage with Dehydration: Coordination with Hydraulic Vulnerability and Drought Tolerance1[C][W][OPEN

PubMed Central

Scoffoni, Christine; Vuong, Christine; Diep, Steven; Cochard, Hervé; Sack, Lawren

2014-01-01

Leaf shrinkage with dehydration has attracted attention for over 100 years, especially as it becomes visibly extreme during drought. However, little has been known of its correlation with physiology. Computer simulations of the leaf hydraulic system showed that a reduction of hydraulic conductance of the mesophyll pathways outside the xylem would cause a strong decline of leaf hydraulic conductance (Kleaf). For 14 diverse species, we tested the hypothesis that shrinkage during dehydration (i.e. in whole leaf, cell and airspace thickness, and leaf area) is associated with reduction in Kleaf at declining leaf water potential (Ψleaf). We tested hypotheses for the linkage of leaf shrinkage with structural and physiological water relations parameters, including modulus of elasticity, osmotic pressure at full turgor, turgor loss point (TLP), and cuticular conductance. Species originating from moist habitats showed substantial shrinkage during dehydration before reaching TLP, in contrast with species originating from dry habitats. Across species, the decline of Kleaf with mild dehydration (i.e. the initial slope of the Kleaf versus Ψleaf curve) correlated with the decline of leaf thickness (the slope of the leaf thickness versus Ψleaf curve), as expected based on predictions from computer simulations. Leaf thickness shrinkage before TLP correlated across species with lower modulus of elasticity and with less negative osmotic pressure at full turgor, as did leaf area shrinkage between full turgor and oven desiccation. These findings point to a role for leaf shrinkage in hydraulic decline during mild dehydration, with potential impacts on drought adaptation for cells and leaves, influencing plant ecological distributions. PMID:24306532

Leaf Phenological Characters of Main Tree Species in Urban Forest of Shenyang

PubMed Central

Xu, Sheng; Xu, Wenduo; Chen, Wei; He, Xingyuan; Huang, Yanqing; Wen, Hua

2014-01-01

Background Plant leaves, as the main photosynthetic organs and the high energy converters among primary producers in terrestrial ecosystems, have attracted significant research attention. Leaf lifespan is an adaptive characteristic formed by plants to obtain the maximum carbon in the long-term adaption process. It determines important functional and structural characteristics exhibited in the environmental adaptation of plants. However, the leaf lifespan and leaf characteristics of urban forests were not studied up to now. Methods By using statistic, linear regression methods and correlation analysis, leaf phenological characters of main tree species in urban forest of Shenyang were observed for five years to obtain the leafing phenology (including leafing start time, end time, and duration), defoliating phenology (including defoliation start time, end time, and duration), and the leaf lifespan of the main tree species. Moreover, the relationships between temperature and leafing phenology, defoliating phenology, and leaf lifespan were analyzed. Findings The timing of leafing differed greatly among species. The early leafing species would have relatively early end of leafing; the longer it took to the end of leafing would have a later time of completed leafing. The timing of defoliation among different species varied significantly, the early defoliation species would have relatively longer duration of defoliation. If the mean temperature rise for 1°C in spring, the time of leafing would experience 5 days earlier in spring. If the mean temperature decline for 1°C, the time of defoliation would experience 3 days delay in autumn. Interpretation There is significant correlation between leaf longevity and the time of leafing and defoliation. According to correlation analysis and regression analysis, there is significant correlation between temperature and leafing and defoliation phenology. Early leafing species would have a longer life span and consequently have advantage on carbon accumulation compared with later defoliation species. PMID:24963625

Plant size and leaf area influence phenological and reproductive responses to warming in semiarid Mediterranean species.

PubMed

Valencia, Enrique; Méndez, Marcos; Saavedra, Noelia; Maestre, Fernando T

2016-08-01

Changes in vegetative and reproductive phenology rank among the most obvious plant responses to climate change. These responses vary broadly among species, but it is largely unknown whether they are mediated by functional attributes, such as size or foliar traits. Using a manipulative experiment conducted over two growing seasons, we evaluated the responses in reproductive phenology and output of 14 Mediterranean semiarid species belonging to three functional groups (grasses, nitrogen-fixing legumes and forbs) to a ~3°C increase in temperature, and assessed how leaf and size traits influenced them. Overall, warming advanced flowering and fruiting phenology, extended the duration of flowering and reduced the production of flowers and fruits. The observed reduction in flower and fruit production with warming was likely related to the decrease in soil moisture promoted by this treatment. Phenological responses to warming did not vary among functional groups, albeit forbs had an earlier reproductive phenology than legumes and grasses. Larger species with high leaf area, as well as those with small specific leaf area, had an earlier flowering and a longer flowering duration. The effects of warming on plant size and leaf traits were related to those on reproductive phenology and reproductive output. Species that decreased their leaf area under warming advanced more the onset of flowering, while those that increased their vegetative height produced more flowers. Our results advance our understanding of the phenological responses to warming of Mediterranean semiarid species, and highlight the key role of traits such as plant size and leaf area as determinants of such responses.

Coordination of Leaf Photosynthesis, Transpiration, and Structural Traits in Rice and Wild Relatives (Genus Oryza).

PubMed

Giuliani, Rita; Koteyeva, Nuria; Voznesenskaya, Elena; Evans, Marc A; Cousins, Asaph B; Edwards, Gerald E

2013-07-01

The genus Oryza, which includes rice (Oryza sativa and Oryza glaberrima) and wild relatives, is a useful genus to study leaf properties in order to identify structural features that control CO(2) access to chloroplasts, photosynthesis, water use efficiency, and drought tolerance. Traits, 26 structural and 17 functional, associated with photosynthesis and transpiration were quantified on 24 accessions (representatives of 17 species and eight genomes). Hypotheses of associations within, and between, structure, photosynthesis, and transpiration were tested. Two main clusters of positively interrelated leaf traits were identified: in the first cluster were structural features, leaf thickness (Thick(leaf)), mesophyll (M) cell surface area exposed to intercellular air space per unit of leaf surface area (S(mes)), and M cell size; a second group included functional traits, net photosynthetic rate, transpiration rate, M conductance to CO(2) diffusion (g(m)), stomatal conductance to gas diffusion (g(s)), and the g(m)/g(s) ratio.While net photosynthetic rate was positively correlated with gm, neither was significantly linked with any individual structural traits. The results suggest that changes in gm depend on covariations of multiple leaf (S(mes)) and M cell (including cell wall thickness) structural traits. There was an inverse relationship between Thick(leaf) and transpiration rate and a significant positive association between Thick(leaf) and leaf transpiration efficiency. Interestingly, high g(m) together with high g(m)/g(s) and a low S(mes)/g(m) ratio (M resistance to CO(2) diffusion per unit of cell surface area exposed to intercellular air space) appear to be ideal for supporting leaf photosynthesis while preserving water; in addition, thick M cell walls may be beneficial for plant drought tolerance.

Whole organ, venation and epidermal cell morphological variations are correlated in the leaves of Arabidopsis mutants.

PubMed

Pérez-Pérez, José Manuel; Rubio-Díaz, Silvia; Dhondt, Stijn; Hernández-Romero, Diana; Sánchez-Soriano, Joaquín; Beemster, Gerrit T S; Ponce, María Rosa; Micol, José Luis

2011-12-01

Despite the large number of genes known to affect leaf shape or size, we still have a relatively poor understanding of how leaf morphology is established. For example, little is known about how cell division and cell expansion are controlled and coordinated within a growing leaf to eventually develop into a laminar organ of a definite size. To obtain a global perspective of the cellular basis of variations in leaf morphology at the organ, tissue and cell levels, we studied a collection of 111 non-allelic mutants with abnormally shaped and/or sized leaves, which broadly represent the mutational variations in Arabidopsis thaliana leaf morphology not associated with lethality. We used image-processing techniques on these mutants to quantify morphological parameters running the gamut from the palisade mesophyll and epidermal cells to the venation, whole leaf and rosette levels. We found positive correlations between epidermal cell size and leaf area, which is consistent with long-standing Avery's hypothesis that the epidermis drives leaf growth. In addition, venation parameters were positively correlated with leaf area, suggesting that leaf growth and vein patterning share some genetic controls. Positional cloning of the genes affected by the studied mutations will eventually establish functional links between genotypes, molecular functions, cellular parameters and leaf phenotypes. © 2011 Blackwell Publishing Ltd.

Relative importance of habitat filtering and limiting similarity on species assemblages of alpine and subalpine plant communities.

PubMed

Takahashi, Koichi; Tanaka, Saeka

2016-11-01

This study examined how habitat filtering and limiting similarity affect species assemblages of alpine and subalpine plant communities along a slope gradient on Mt. Norikura in central Japan. Plant traits (plant height, individual leaf area, specific leaf area (SLA), leaf linearity, leaf nitrogen and chlorophyll concentrations) and abiotic environmental factors (elevation, slope inclination, ground surface texture, soil water, soil pH, soil nutrient concentrations of NH 4 -N and NO 3 -N) were examined. The metrics of variance, range, kurtosis and the standard deviation of neighbor distance divided by the range of traits present (SDNDr) were calculated for each plant trait to measure trait distribution patterns. Limiting similarity was detected only for chlorophyll concentration. By contrast, habitat filtering was detected for individual leaf area, SLA, leaf linearity, chlorophyll concentration. Abiotic environmental factors were summarized by the principal component analysis (PCA). The first PCA axis positively correlated with elevation and soil pH, and negatively correlated with sand cover, soil water, NH 4 -N and NO 3 -N concentrations. High values of the first PCA axis represent the wind-exposed upper slope with lower soil moisture and nutrient availabilities. Plant traits changed along the first PCA axis. Leaf area, SLA and chlorophyll concentration decreased, and leaf linearity increased with the first PCA axis. This study showed that the species assemblage of alpine and subalpine plants was determined mainly by habitat filtering, indicating that abiotic environmental factors are more important for species assemblage than interspecific competition. Therefore, only species adapting to abiotic environments can distribute to these environments.

Community-weighted mean of leaf traits and divergence of wood traits predict aboveground biomass in secondary subtropical forests.

PubMed

Ali, Arshad; Yan, En-Rong; Chang, Scott X; Cheng, Jun-Yang; Liu, Xiang-Yu

2017-01-01

Subtropical forests are globally important in providing ecological goods and services, but it is not clear whether functional diversity and composition can predict aboveground biomass in such forests. We hypothesized that high aboveground biomass is associated with high functional divergence (FDvar, i.e., niche complementarity) and community-weighted mean (CWM, i.e., mass ratio; communities dominated by a single plant strategy) of trait values. Structural equation modeling was employed to determine the direct and indirect effects of stand age and the residual effects of CWM and FDvar on aboveground biomass across 31 plots in secondary forests in subtropical China. The CWM model accounted for 78, 20, 6 and 2% of the variation in aboveground biomass, nitrogen concentration in young leaf, plant height and specific leaf area of young leaf, respectively. The FDvar model explained 74, 13, 7 and 0% of the variation in aboveground biomass, plant height, twig wood density and nitrogen concentration in young leaf, respectively. The variation in aboveground biomass, CWM of leaf nitrogen concentration and specific leaf area, and FDvar of plant height, twig wood density and nitrogen concentration in young leaf explained by the joint model was 86, 20, 13, 7, 2 and 0%, respectively. Stand age had a strong positive direct effect but low indirect positive effects on aboveground biomass. Aboveground biomass was negatively related to CWM of nitrogen concentration in young leaf, but positively related to CWM of specific leaf area of young leaf and plant height, and FDvar of plant height, twig wood density and nitrogen concentration in young leaf. Leaf and wood economics spectra are decoupled in regulating the functionality of forests, communities with diverse species but high nitrogen conservative and light acquisitive strategies result in high aboveground biomass, and hence, supporting both the mass ratio and niche complementarity hypotheses in secondary subtropical forests. Copyright © 2016 Elsevier B.V. All rights reserved.

Use of Pleurotus eous Strain P-31 Spent Mushroom Compost (SMC) as Soil Conditioner on the Growth and Yield Performance of Capsicum annuum L. and Solanum lycopersicon L. Seedlings under Greenhouse Conditions in Ghana

PubMed Central

Wiafe-Kwagyan, M; Odamtten, G T

2018-01-01

The objective of this study was to investigate the influence of spent mushroom compost of Pleurotus eous strain P-31 on the growth and yield performance of pepper and tomato seedlings under greenhouse conditions. Sandy loam soil was combined with different percentages of SMC to obtain the following combinations (0, 5, 10, 15, 20, 25 and 30) %. Lower concentrations SMC5, SMC10 and SMC15 promoted vegetative growth (plant height, leaf area, chlorophyll content, number of leaves and axillary branches) of the two test plants. Tomato seedlings grown in SMC10 recorded the highest plant height (50.3 ± 7.2cm); leaf area (378.8 ± 1.2cm2); number of floral buds (51) and flowers (28) whereas SMC5 recorded the highest chlorophyll content 34.1 ± 0.9CCI though SMC15 recorded the highest number of leaves (8). Tomato seedlings grown in SMC30 produced both the maximum number of fruits (8) with corresponding high weight (34.2 ± 7.7g). Pepper seedlings grown in lower concentrations (SMC5–15) recorded the highest plant heights (29.8–30.8cm), chlorophyll content (20.3CCI) and leaf area (53.5–66.2 cm2). Although the different combinations of sandy loam soil and SMC did not significantly (p ≥ 0.05) affect the number of axillary branches developed; different combinations significantly (p ≤ 0.05) affected the number of floral bud, flower and fruit, weight of fruits formed and value of each of these increased with increasing percentage of SMC. Pepper seedlings grown on SMC30 recorded the maximum number of floral buds (32.0 ± 3.6), number of flowers (19.4 ± 1.3), number of fruits (10.8 ± 1.2) and weight of fruits (31.9 ± 3.4g). Tomato seedlings raised on SMC100 (spent mushroom compost only) and soil only did not significantly (p ≥ 0.05) differ from each other however, was statistically significant (p ≤ 0.05) from amended sandy loam soil by all criteria investigated. The study shows that SMC provide favourable soil conditioners for the cultivation of fruits, vegetables and foliage crops as it improved growth and yield of tomato and pepper seedlings. PMID:29644023

Allometric relationships predicting foliar biomass and leaf area:sapwood area ratio from tree height in five Costa Rican rain forest species.

PubMed

Calvo-Alvarado, J C; McDowell, N G; Waring, R H

2008-11-01

We developed allometric equations to predict whole-tree leaf area (A(l)), leaf biomass (M(l)) and leaf area to sapwood area ratio (A(l):A(s)) in five rain forest tree species of Costa Rica: Pentaclethra macroloba (Willd.) Kuntze (Fabaceae/Mim), Carapa guianensis Aubl. (Meliaceae), Vochysia ferru-gi-nea Mart. (Vochysiaceae), Virola koshnii Warb. (Myristicaceae) and Tetragastris panamensis (Engl.) Kuntze (Burseraceae). By destructive analyses (n = 11-14 trees per species), we observed strong nonlinear allometric relationships (r(2) > or = 0.9) for predicting A(l) or M(l) from stem diameters or A(s) measured at breast height. Linear relationships were less accurate. In general, A(l):A(s) at breast height increased linearly with tree height except for Penta-clethra, which showed a negative trend. All species, however, showed increased total A(l) with height. The observation that four of the five species increased in A(l):A(s) with height is consistent with hypotheses about trade--offs between morphological and anatomical adaptations that favor efficient water flow through variation in the amount of leaf area supported by sapwood and those imposed by the need to respond quickly to light gaps in the canopy.

Loblolly pine productivity and water relations in response to throughfall reduction and fertilizer application on a poorly drained site in northern Florida

DOE PAGES

Wightman, Maxwell G.; Martin, Timothy A.; Gonzalez-Benecke, Carlos A.; ...

2016-09-26

Loblolly pine ( Pinus taeda L.) forests are of great ecological and economic value in the southeastern United States, where nutrient availability frequently limits productivity. The impact of fertilizer application on the growth and water relations of loblolly pine has been investigated by numerous studies; however, few field experiments have examined the effects of drought. Drought is of particular interest due to the potential for climate change to alter soil water availability. In this study, we investigated the impact of fertilizer application and a 30% reduction in throughfall on loblolly pine productivity, transpiration, hydraulic conductance, and stomatal conductance. The studymore » was installed in a ten-year-old loblolly pine plantation on a somewhat poorly drained site in northern Florida. Throughfall reduction did not impact tree productivity or water relations of the trees. This lack of response was attributed to abundant rainfall and the ability of trees to access the shallow water table at this site. Fertilizer application increased basal area production by 20% and maximum leaf area index by 0.5 m2 m 2, but it did not affect whole-tree hydraulic conductance or the sensitivity of stomatal conductance to vapor pressure deficit. During the spring, when leaf area and vapor pressure deficit were high, the fertilizer-only treatment increased monthly transpiration by 17% when compared to the control. This relationship, furthermore, was not significant during the rest of the year.« less

Leaf Morphology and Ultrastructure Responses to Elevated O3 in Transgenic Bt (cry1Ab/cry1Ac) Rice and Conventional Rice under Fully Open-Air Field Conditions

PubMed Central

Li, Chunyan; Liu, Biao; Li, Chunhua; Zeng, Qing; Hao, Mingzhuo; Han, Zhengmin; Zhu, Jianguo; Li, Xiaogang; Shen, Wenjing

2013-01-01

Background Elevated tropospheric ozone severely affects not only yield but also the morphology, structure and physiological functions of plants. Because of concerns regarding the potential environmental risk of transgenic crops, it is important to monitor changes in transgenic insect-resistant rice under the projected high tropospheric ozone before its commercial release. Methodology/Principal Findings Using a free-air concentration enrichment (FACE) system, we investigated the changes in leaf morphology and leaf ultrastructure of two rice varieties grown in plastic pots, transgenic Bt Shanyou 63 (Bt-SY63, carrying a fusion gene of cry1Ab and cry1Ac) and its non-transgenic counterpart (SY63), in elevated O3 (E-O3) versus ambient O3 (A-O3) after 64-DAS (Days after seeding), 85-DAS and 102-DAS. Our results indicated that E-O3 had no significant effects on leaf length, leaf width, leaf area, stomatal length and stomatal density for both Bt-SY63 and SY63. E-O3 increased the leaf thickness of Bt-SY63, but decreased that of SY63. O3 stress caused early swelling of the thylakoids of chloroplasts, a significant increase in the proportion of total plastoglobule area in the entire cell area (PCAP) and a significant decrease in the proportion of total starch grain area in the entire cell area (SCAP), suggesting that E-O3 accelerated the leaf senescence of the two rice genotypes. Compared with SY63, E-O3 caused early swelling of the thylakoids of chloroplasts and more substantial breakdown of chloroplasts in Bt-SY63. Conclusions/Significance Our results suggest that the incorporation of cry1Ab/Ac into SY63 could induce unintentional changes in some parts of plant morphology and that O3 stress results in greater leaf damage to Bt-SY63 than to SY63, with the former coupled with higher O3 sensitivity in CCAP (the proportions of total chloroplast area in the entire cell area), PCAP and SCAP. This study provides valuable baseline information for the prospective commercial release of transgenic crops under the projected future climate. PMID:24324764

Imaging of fast chlorophyll fluorescence induction curve (OJIP) parameters, applied in a screening study with wild barley (Hordeum spontaneum) genotypes under heat stress.

PubMed

Jedmowski, Christoph; Brüggemann, Wolfgang

2015-10-01

We quantified the influence of heat stress (HS) on PSII by imaging of parameters of the fast chlorophyll fluorescence (CF) induction (OJIP) kinetic of 20 genotypes of wild barley (Hordeum spontaneum) covering a broad geographical spectrum. We developed a standardised screening procedure, allowing a repetitive fluorescence measurement of leaf segments. The impact of HS was quantified by calculating a Heat Resistance Index (HRI), derived from the decrease of the Performance Index (PI) caused by HS treatment and following recovery. For the genotype showing the lowest HRI, reduced maximum quantum yield (φP0) and increased relative variable fluorescence of the O-J phase (K-Peak) were detected after HS, whereas the basal fluorescence (F0) remained stable. An additional feature was a lowered fraction of active (QA-reducing) reaction centres (RCs). The disturbances disappeared after one day of recovery. Spatial heterogeneities of fluorescence parameters were detected, as the negative effect of HS was stronger in the leaf areas close to the leaf tip. The results of this study prove that chlorophyll fluorescence imaging (CFI) is suitable for the detection of HS symptoms and that imaging of JIP-Test parameters should be considered in future screening and phenotyping studies aiming for the characterisation of plant genotypes. Copyright © 2015 Elsevier B.V. All rights reserved.

Highlighting the effects of coumarin on adult plants of Arabidopsis thaliana (L.) Heynh. by an integrated -omic approach.

PubMed

Araniti, Fabrizio; Scognamiglio, Monica; Chambery, Angela; Russo, Rosita; Esposito, Assunta; D'Abrosca, Brigida; Fiorentino, Antonio; Lupini, Antonio; Sunseri, Francesco; Abenavoli, Maria Rosa

2017-06-01

In this study, the effects of the allelochemical coumarin through a metabolomic, proteomic and morpho-physiological approach in Arabidopsis adult plants (25days old) were investigated. Metabolomic analysis evidenced an increment of amino acids and a high accumulation of soluble sugars, after 6days of coumarin treatment. This effect was accompanied by a strong decrease on plant fresh and dry weights, as well as on total protein content. On the contrary, coumarin did not affect leaf number but caused a reduction in leaf area. An alteration of water status was confirmed by a reduction of relative water content and an increase in leaf osmotic potential. Moreover, coumarin impaired plant bio-membranes through an increase of lipid peroxidation and H 2 O 2 content suggesting that coumarin treatment might induce oxidative stress. Coumarin reduced the effective quantum yield of the photosystem II, the energy dissipation in the form of heat, the maximum PSII efficiency, the coefficient of the photochemical quenching and the estimated electron transport rate, while it significantly stimulated the fluorescence emission and the coefficient of the non photochemical quenching. Finally, the proteomic characterization of coumarin-treated plants revealed a down-regulation of the ROS detoxifying proteins, responsible of oxidative damage and consequently of physiological cascade effects. Copyright © 2017 Elsevier GmbH. All rights reserved.

The influence of branch order on optimal leaf vein geometries: Murray's law and area preserving branching.

PubMed

Price, Charles A; Knox, Sarah-Jane C; Brodribb, Tim J

2013-01-01

Models that predict the form of hierarchical branching networks typically invoke optimization based on biomechanical similitude, the minimization of impedance to fluid flow, or construction costs. Unfortunately, due to the small size and high number of vein segments found in real biological networks, complete descriptions of networks needed to evaluate such models are rare. To help address this we report results from the analysis of the branching geometry of 349 leaf vein networks comprising over 1.5 million individual vein segments. In addition to measuring the diameters of individual veins before and after vein bifurcations, we also assign vein orders using the Horton-Strahler ordering algorithm adopted from the study of river networks. Our results demonstrate that across all leaves, both radius tapering and the ratio of daughter to parent branch areas for leaf veins are in strong agreement with the expectation from Murray's law. However, as veins become larger, area ratios shift systematically toward values expected under area-preserving branching. Our work supports the idea that leaf vein networks differentiate roles of leaf support and hydraulic supply between hierarchical orders.

Light-Induced Indeterminacy Alters Shade-Avoiding Tomato Leaf Morphology1[OPEN

PubMed Central

Chitwood, Daniel H.; Kumar, Ravi; Ranjan, Aashish; Pelletier, Julie M.; Townsley, Brad T.; Ichihashi, Yasunori; Martinez, Ciera C.; Zumstein, Kristina; Harada, John J.; Maloof, Julin N.; Sinha, Neelima R.

2015-01-01

Plants sense the foliar shade of competitors and alter their developmental programs through the shade-avoidance response. Internode and petiole elongation, and changes in overall leaf area and leaf mass per area, are the stereotypical architectural responses to foliar shade in the shoot. However, changes in leaf shape and complexity in response to shade remain incompletely, and qualitatively, described. Using a meta-analysis of more than 18,000 previously published leaflet outlines, we demonstrate that shade avoidance alters leaf shape in domesticated tomato (Solanum lycopersicum) and wild relatives. The effects of shade avoidance on leaf shape are subtle with respect to individual traits but are combinatorially strong. We then seek to describe the developmental origins of shade-induced changes in leaf shape by swapping plants between light treatments. Leaf size is light responsive late into development, but patterning events, such as stomatal index, are irrevocably specified earlier. Observing that shade induces increases in shoot apical meristem size, we then describe gene expression changes in early leaf primordia and the meristem using laser microdissection. We find that in leaf primordia, shade avoidance is not mediated through canonical pathways described in mature organs but rather through the expression of KNOTTED1-LIKE HOMEOBOX and other indeterminacy genes, altering known developmental pathways responsible for patterning leaf shape. We also demonstrate that shade-induced changes in leaf primordium gene expression largely do not overlap with those found in successively initiated leaf primordia, providing evidence against classic hypotheses that shaded leaf morphology results from the prolonged production of juvenile leaf types. PMID:26381315

Study on beta-galactosidase enzymatic activity of herbal yogurt.

PubMed

Chowdhury, Banani Ray; Chakraborty, Runu; Raychaudhuri, Utpal

2008-03-01

Different types of herbal yogurts were developed by mixing standardized milk with pretreated herbs, namely tulsi leaf (Ocimum sanctum), pudina leaf (Mentha arvensis) and coriander leaf (Coriandrum sativum), with leaves separately and a 1:1 (v/v) mixture of the strains of lactic starter cultures---Lactobacillus acidophilus (NCIM 2903) and Lactobacillus plantarum (NCIM 2083)-followed by incubation at 40 degrees C for 6 h. The beta-galactosidase enzymatic activity of the abovementioned herbal yogurts was determined and interestingly noted to exhibit higher enzymatic activity compared with the control yogurt (without any herbs). Among all herbal yogurts, tulsi yogurt had the maximum beta-galactosidase activity.

On the Relationship Between Hyperspectral Data and Foliar Nitrogen Content in Closed Canopy Forests

NASA Astrophysics Data System (ADS)

Knyazikhin, Y.; Schull, M.; Lepine, L. C.; Stenberg, P.; Mõttus, M.; Rautiainen, M.; Latorre, P.; Myneni, R.; Kaufmann, R.

2011-12-01

The importance of nitrogen for terrestrial ecosystem carbon dynamics and its climate feedback has been well recognized by the ecological community. Interaction between carbon and nitrogen at leaf level is among the fundamental mechanisms that directly control the dynamics of terrestrial vegetation carbon. This process influences absorption and scattering of solar radiation by foliage, which in turn impacts radiation reflected by the vegetation and measured by satellite sensors. NASA's Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) and ground based data on canopy structure and foliage nitrogen concentration acquired over six sites in Maine, New England, Florida, North Carolina and Washington were analyzed to assess the role of canopy structure, leaf optics and its biochemical constituents in the spectral variation of radiation reflected by the forest. The study sites represent closed canopy forests (LAI~5). Our results suggest: 1. Impact of canopy structure is so strong that it can significantly suppress the sensitivity of hyperspectral data to leaf optics. 2. Forest reflectance spectra in the interval [710, 790 nm] are required to obtain the fraction of the total leaf area that a "sensor sees" in a given direction. For closed canopy forests its retrieval does not require canopy reflectance models, suggesting that canopy reflectance spectra in this interval provide a direct estimate of the leaf area fraction. 3. The leaf area fraction fully explains variation in measured reflectance spectra due to variation in canopy structure. This variable is used to estimate the mean leaf scattering over foliage that the "sensor sees." For example the nadir-viewing AVIRIS sensor accumulates foliage optical properties over 25% of the total foliage area in needle leaf forest and about 50% in broadleaf forest. 4. Leaf surface properties have an impact on forest reflectivity, lowering its sensitivity to leaf absorbing pigments. 5. Variation in foliar nitrogen concentration can explain up to 55% of variation in AVIRIS spectra in the interval between 400 and 900 nm. The remaining factors could be due to (a) impact of leaf surface properties and/or (b) under-sampling of leaf optical properties due to the single view of the AVIRIS sensor. The theory of canopy spectral invariants underlies the separation of leaf scattering from the total canopy reflectance spectrum.

Evidence for shifts to faster growth strategies in the new ranges of invasive alien plants

PubMed Central

Leishman, Michelle R; Cooke, Julia; Richardson, David M; Newman, Jonathan

2014-01-01

Summary Understanding the processes underlying the transition from introduction to naturalization and spread is an important goal of invasion ecology. Release from pests and pathogens in association with capacity for rapid growth is thought to confer an advantage for species in novel regions. We assessed leaf herbivory and leaf-level traits associated with growth strategy in the native and exotic ranges of 13 invasive plant species from 256 populations. Species were native to either the Western Cape region of South Africa, south-western Australia or south-eastern Australia and had been introduced to at least one of the other regions or to New Zealand. We tested for evidence of herbivore release and shifts in leaf traits between native and exotic ranges of the 13 species. Across all species, leaf herbivory, specific leaf area and leaf area were significantly different between native and exotic ranges while there were no significant differences across the 13 species found for leaf mass, assimilation rate, dark respiration or foliar nitrogen. Analysis at the species- and region-level showed that eight out of 13 species had reduced leaf herbivory in at least one exotic region compared to its native range. Six out of 13 species had significantly larger specific leaf area (SLA) in at least one exotic range region and five of those six species experienced reduced leaf herbivory. Increases in SLA were underpinned by increases in leaf area rather than reductions in leaf mass. No species showed differences in the direction of trait shifts from the native range between different exotic regions. This suggests that the driver of selection on these traits in the exotic range is consistent across regions and hence is most likely to be associated with factors linked with introduction to a novel environment, such as release from leaf herbivory, rather than with particular environmental conditions. Synthesis. These results provide evidence that introduction of a plant species into a novel environment commonly results in a reduction in the top-down constraint imposed by herbivores on growth, allowing plants to shift towards a faster growth strategy which may result in an increase in population size and spread and consequently to invasive success. PMID:25558090

Postponing the production of ant domatia as a strategy promoting an escape from flooding in an Amazonian myrmecophyte.

PubMed

Izzo, Thiago J; Fernandez Piedade, Maria Teresa; Dáttilo, Wesley

2018-06-07

Even when adapted to flooding environments, the spatial distribution, growing strategies and anti-herbivore defences of plants face stressful conditions. Here we describe the effects of flooding on carbon allocation on growth, domatia and leaf production, and the herbivory on the myrmecophyte domatia-bearing Tococa coronata Benth. (Melastomataceae) growing along river banks in the Amazon region. In an area of 80 000 m2 of riparian forest along the Juruena River we actively searched for individuals of T. coronata. In each plant we evaluated the size of the plant when producing the first domatium and determined its best predictor: (1) plant total height; (2) size of plants above flood level; or (3) length of time each plant spent underwater. We also compared the herbivory, internode elongation, foliar asymmetry and specific leaf weight between T. coronata individuals growing above and below the maximum flooding level. The distance to the river and the height of the first domatium produced were compared between T. coronata and its sympatric congener, T. bulifera. We found that T. coronata invests in rapid growth in the early ontogenetic stages through an elongation of internodes rather than in constitutive anti-herbivore defences to leaves or domatia to exceed the maximum flooding level. Consequently, its leaf herbivory was higher when compared with those produced above the flooding level. Individuals with leaves above flood levels produce coriaceous leaves and ant-domatias. Thus, flooding seems to trigger changes in growth strategies of the species. Furthermore, T. coronata occurs within the flood level, whereas its congener T. bullifera invariably occurs at sites unreachable by floods. Even in conditions of high stress, T. coronata presents both physiological and adaptive strategies that allow for colonization and establishment within flooded regions. These mechanisms involve an extreme trade-off of postponing adult plant characteristics to rapid growth to escape flooding while minimizing carbon allocation to defence.

Gross rainfall amount and maximum rainfall intensity in 60-minute influence on interception loss of shrubs: a 10-year observation in the Tengger Desert

PubMed Central

Zhang, Zhi-Shan; Zhao, Yang; Li, Xin-Rong; Huang, Lei; Tan, Hui-Juan

2016-01-01

In water-limited regions, rainfall interception is influenced by rainfall properties and crown characteristics. Rainfall properties, aside from gross rainfall amount and duration (GR and RD), maximum rainfall intensity and rainless gap (RG), within rain events may heavily affect throughfall and interception by plants. From 2004 to 2014 (except for 2007), individual shrubs of Caragana korshinskii and Artemisia ordosica were selected to measure throughfall during 210 rain events. Various rainfall properties were auto-measured and crown characteristics, i.e., height, branch and leaf area index, crown area and volume of two shrubs were also measured. The relative interceptions of C. korshinskii and A. ordosica were 29.1% and 17.1%, respectively. Rainfall properties have more contributions than crown characteristics to throughfall and interception of shrubs. Throughfall and interception of shrubs can be explained by GR, RI60 (maximum rainfall intensities during 60 min), RD and RG in deceasing importance. However, relative throughfall and interception of two shrubs have different responses to rainfall properties and crown characteristics, those of C. korshinskii were closely related to rainfall properties, while those of A. ordosica were more dependent on crown characteristics. We highlight long-term monitoring is very necessary to determine the relationships between throughfall and interception with crown characteristics. PMID:27184918

Leaf spring made of fiber-reinforced resin

NASA Technical Reports Server (NTRS)

Hori, J.

1986-01-01

A leaf spring made of a matrix reinforced by at least two types of reinforcing fibers with different Young's modulus is described in this Japanese patent. At least two layers of reinforcing fibers are formed by partially arranging the reinforcing fibers toward the direction of the thickness of the leaf spring. A mixture of different types of reinforced fibers is used at the area of boundary between the two layers of reinforced fibers. The ratio of blending of each type of reinforced fiber is frequently changed to eliminate the parts where discontinuous stress may be applied to the leaf spring. The objective of this invention is to prevent the rapid change in Young's modulus at the boundary area between each layer of reinforced fibers in the leaf spring.

Leaf Movements of Indoor Plants Monitored by Terrestrial LiDAR

PubMed Central

Herrero-Huerta, Mónica; Lindenbergh, Roderik; Gard, Wolfgang

2018-01-01

Plant leaf movement is induced by some combination of different external and internal stimuli. Detailed geometric characterization of such movement is expected to improve understanding of these mechanisms. A metric high-quality, non-invasive and innovative sensor system to analyze plant movement is Terrestrial LiDAR (TLiDAR). This technique has an active sensor and is, therefore, independent of light conditions, able to obtain accurate high spatial and temporal resolution point clouds. In this study, a movement parameterization approach of leaf plants based on TLiDAR is introduced. For this purpose, two Calathea roseopicta plants were scanned in an indoor environment during 2 full-days, 1 day in natural light conditions and the other in darkness. The methodology to estimate leaf movement is based on segmenting individual leaves using an octree-based 3D-grid and monitoring the changes in their orientation by Principal Component Analysis. Additionally, canopy variations of the plant as a whole were characterized by a convex-hull approach. As a result, 9 leaves in plant 1 and 11 leaves in plant 2 were automatically detected with a global accuracy of 93.57 and 87.34%, respectively, compared to a manual detection. Regarding plant 1, in natural light conditions, the displacement average of the leaves between 7.00 a.m. and 12.30 p.m. was 3.67 cm as estimated using so-called deviation maps. The maximum displacement was 7.92 cm. In addition, the orientation changes of each leaf within a day were analyzed. The maximum variation in the vertical angle was 69.6° from 12.30 to 6.00 p.m. In darkness, the displacements were smaller and showed a different orientation pattern. The canopy volume of plant 1 changed more in the morning (4.42 dm3) than in the afternoon (2.57 dm3). The results of plant 2 largely confirmed the results of the first plant and were added to check the robustness of the methodology. The results show how to quantify leaf orientation variation and leaf movements along a day at mm accuracy in different light conditions. This confirms the feasibility of the proposed methodology to robustly analyse leaf movements. PMID:29527217

Measurement of Leaf Mass and Leaf Area of Oaks In A Mediterranean-climate Region For Biogenic Emission Estimation

NASA Astrophysics Data System (ADS)

Karlik, J.

Given the key role played by biogenic volatile organic compounds (BVOC) in tro- pospheric chemistry and regional air quality, it is critical to generate accurate BVOC emission inventories. Because several oak species have high BVOC emission rates, and oak trees are often of large stature with corresponding large leaf masses, oaks may be the most important genus of woody plants for BVOC emissions modeling in the natural landscapes of Mediterranean-climate regions. In California, BVOC emis- sions from oaks may mix with anthropogenic emissions from urban areas, leading to elevated levels of ozone. Data for leaf mass and leaf area for a stand of native blue oaks (Quercus douglasii) were obtained through harvest and leaf removal from 14 trees lo- cated in the Sierra Nevada foothills of central California. Trees ranged in height from 4.2 to 9.9 m, with trunk diameters at breast height of 14 to 85 cm. Mean leaf mass density was 730 g m-2 for the trees and had an overall value of 310 g m-2 for the site. Consideration of the surrounding grassland devoid of trees resulted in a value of about 150 g m-2, less than half of reported values for eastern U.S. oak woodlands, but close to a reported value for oaks found in St. Quercio, Italy. The mean value for leaf area index (LAI) for the trees at this site was 4.4 m2 m-2. LAI for the site was 1.8 m2 m-2, but this value was appropriate for the oak grove only; including the surrounding open grassland resulted in an overall LAI value of 0.9 m2 m-2 or less. A volumetric method worked well for estimating the leaf mass of the oak trees. Among allometric relationships investigated, trunk circumference, mean crown radius, and crown projec- tion were well correlated with leaf mass. Estimated emission of isoprene (mg C m-2 h-1) for the site based these leaf mass data and experimentally determined emission rate was similar to that reported for a Mediterranean oak woodland in France.

Leaf traits in relation to crown development, light interception and growth of elite families of loblolly and slash pine.

PubMed

Chmura, Daniel J; Tjoelker, Mark G

2008-05-01

Crown architecture and size influence leaf area distribution within tree crowns and have large effects on the light environment in forest canopies. The use of selected genotypes in combination with silvicultural treatments that optimize site conditions in forest plantations provide both a challenge and an opportunity to study the biological and environmental determinants of forest growth. We investigated tree growth, crown development and leaf traits of two elite families of loblolly pine (Pinus taeda L.) and one family of slash pine (P. elliottii Mill.) at canopy closure. Two contrasting silvicultural treatments -- repeated fertilization and control of competing vegetation (MI treatment), and a single fertilization and control of competing vegetation treatment (C treatment) -- were applied at two experimental sites in the West Gulf Coastal Plain in Texas and Louisiana. At a common tree size (diameter at breast height), loblolly pine trees had longer and wider crowns, and at the plot-level, intercepted a greater fraction of photosynthetic photon flux than slash pine trees. Leaf-level, light-saturated assimilation rates (A(max)) and both mass- and area-based leaf nitrogen (N) decreased, and specific leaf area (SLA) increased with increasing canopy depth. Leaf-trait gradients were steeper in crowns of loblolly pine trees than of slash pine trees for SLA and leaf N, but not for A(max). There were no species differences in A(max), except in mass-based photosynthesis in upper crowns, but the effect of silvicultural treatment on A(max) differed between sites. Across all crown positions, A(max) was correlated with leaf N, but the relationship differed between sites and treatments. Observed patterns of variation in leaf properties within crowns reflected acclimation to developing light gradients in stands with closing canopies. Tree growth was not directly related to A(max), but there was a strong correlation between tree growth and plot-level light interception in both species. Growth efficiency was unaffected by silvicultural treatment. Thus, when coupled with leaf area and light interception at the crown and canopy levels, A(max) provides insight into family and silvicultural effects on tree growth.

Leaf trait dissimilarities between Dutch elm hybrids with a contrasting tolerance to Dutch elm disease

PubMed Central

Ďurkovič, Jaroslav; Čaňová, Ingrid; Lagaňa, Rastislav; Kučerová, Veronika; Moravčík, Michal; Priwitzer, Tibor; Urban, Josef; Dvořák, Miloň; Krajňáková, Jana

2013-01-01

Background and Aims Previous studies have shown that Ophiostoma novo-ulmi, the causative agent of Dutch elm disease (DED), is able to colonize remote areas in infected plants of Ulmus such as the leaf midrib and secondary veins. The objective of this study was to compare the performances in leaf traits between two Dutch elm hybrids ‘Groeneveld’ and ‘Dodoens’ which possess a contrasting tolerance to DED. Trait linkages were also tested with leaf mass per area (LMA) and with the reduced Young's modulus of elasticity (MOE) as a result of structural, developmental or functional linkages. Methods Measurements and comparisons were made of leaf growth traits, primary xylem density components, gas exchange variables and chlorophyll a fluorescence yields between mature plants of ‘Groeneveld’ and ‘Dodoens’ grown under field conditions. A recently developed atomic force microscopy technique, PeakForce quantitative nanomechanical mapping, was used to reveal nanomechanical properties of the cell walls of tracheary elements such as MOE, adhesion and dissipation. Key Results ‘Dodoens’ had significantly higher values for LMA, leaf tissue thickness variables, tracheary element lumen area (A), relative hydraulic conductivity (RC), gas exchange variables and chlorophyll a fluorescence yields. ‘Groeneveld’ had stiffer cell walls of tracheary elements, and higher values for water-use efficiency and leaf water potential. Leaves with a large carbon and nutrient investment in LMA tended to have a greater leaf thickness and a higher net photosynthetic rate, but LMA was independent of RC. Significant linkages were also found between the MOE and some vascular traits such as RC, A and the number of tracheary elements per unit area. Conclusions Strong dissimilarities in leaf trait performances were observed between the examined Dutch elm hybrids. Both hybrids were clearly separated from each other in the multivariate leaf trait space. Leaf growth, vascular and gas exchange traits in the infected plants of ‘Dodoens’ were unaffected by the DED fungus. ‘Dodoens’ proved to be a valuable elm germplasm for further breeding strategies. PMID:23264236

[Several changes of Indocalamus leaf active ingredients contents].

PubMed

Su, Chun-hua; Liu, Guo-hua; Wang, Fu-sheng; Ding, Yu-long; Xue, Jian-hui

2011-09-01

In this paper, the leaves of Indocalamus herklotsii, Indocalamus decorus, and Indocalamus latifolius were collected from Nanjing in different seasons to study the seasonal changes of the total flavonoids, tea polyphenols, and soluble sugar contents in the leaves. There existed significant differences in the test active ingredients contents among the leaves of the three Indocalamus species. The leaf total flavonoids content of the three Indocalamus species in different seasons ranged in 1.7%-2.7%, being the highest for I. herklotsii and I. decorus in spring and for I. latifolius in winter. The leaf tea polyphenols content varied from 5.5% to 7.6%; and the leaf soluble sugar content was 1.0%-8.5%, with the maximum in spring. Within the three months after leaf unfolding, the active ingredients contents in I. herklotsii and I. decorus leaves increased with leaf age. The optimal period for harvesting Indocalamus leaves was from December to next March. Among the three Indocalamus species, I. latifolius had the highest contents of the three active ingredients in leaves, suggesting that I. latifolius had greater potential value in the utilization of its leaf active ingredients than the other two species.

Dissipation and Residues of Pyrethrins in Leaf Lettuce under Greenhouse and Open Field Conditions.

PubMed

Pan, Lixiang; Feng, Xiaoxiao; Zhang, Hongyan

2017-07-21

Pyrethrins are nowadays widely used for prevention and control of insects in leaf lettuce. However, there is a concern about the pesticide residue in leaf lettuce. A reliable analytical method for determination of pyrethrins (pyrethrin-and П, cinerin І and П, and jasmolin І and П) in leaf lettuce was developed by using gas chromatography-mass spectrometry (GC-MS). Recoveries of pyrethrins in leaf lettuce at three spiking levels were 99.4-104.0% with relative standard deviations of 0.9-3.1% ( n = 5). Evaluation of dissipation and final residues of pyrethrins in leaf lettuce were determined at six different locations, including the open field, as well as under greenhouse conditions. The initial concentration of pyrethrins in greenhouse (0.57 mg/kg) was higher than in open field (0.25 mg/kg) and the half-life for pyrethrins disappearance in field lettuce (0.7 days) was less than that greenhouse lettuce (1.1 days). Factors such as rainfall, solar radiation, wind speed, and crop growth rate are likely to have caused these results. The final residue in leaf lettuce was far below the maximum residue limits (MRLs) (1 mg/kg established by the European Union (EU), Australia, Korea, Japan).

Linkage between canopy water storage and drop size distributions of leaf drips

NASA Astrophysics Data System (ADS)

Nanko, Kazuki; Watanabe, Ai; Hotta, Norifumi; Suzuki, Masakazu

2013-04-01

Differences in drop size distribution (DSD) of leaf drips among tree species have been estimated and physically interpreted to clarify the leaf drip generation process. Leaf drip generation experiments for nine species were conducted in an indoor location without foliage vibration using an automatic mist spray. Broad-leaved species produced a similar DSD among species whose leaves had a matte surface and a second similar DSD among species whose leaves had a coated surface. The matte broad leaves produced a larger and wider range of DSDs than the coated broad leaves. Coated coniferous needles had a wider range of DSDs than the coated broad leaves and different DSDs were observed for different species. The species with shorter dense needles generated a larger DSD. The leaf drip diameter was calculated through the estimation of a state of equilibrium of a hanging drop on the leaves based on physical theory. The calculations indicated that the maximum diameter of leaf drips was determined by the contact angle, and the range of DSDs was determined by the variation in contact length and the contact diameter at the hanging points. The results revealed that leaf drip DSD changed due to variations in leaf hydrophobicity, leaf roughness, leaf geometry and leaf inclination among the different tree species. This study allows the modelization of throughfall DSD. Furthermore, it indicates the possibility of interpreting canopy water processes from canopy water storage to drainage through the contact angle and leaf drip DSD. The part of this study is published in Nanko et al. (2013, Agric. Forest. Meteorol. 169, 74-84).

QTL mapping of flag leaf-related traits in wheat (Triticum aestivum L.).

PubMed

Liu, Kaiye; Xu, Hao; Liu, Gang; Guan, Panfeng; Zhou, Xueyao; Peng, Huiru; Yao, Yingyin; Ni, Zhongfu; Sun, Qixin; Du, Jinkun

2018-04-01

QTL controlling flag leaf length, flag leaf width, flag leaf area and flag leaf angle were mapped in wheat. This study aimed to advance our understanding of the genetic mechanisms underlying morphological traits of the flag leaves of wheat (Triticum aestivum L.). A recombinant inbred line (RIL) population derived from ND3331 and the Tibetan semi-wild wheat Zang1817 was used to identify quantitative trait loci (QTLs) controlling flag leaf length (FLL), flag leaf width (FLW), flag leaf area (FLA), and flag leaf angle (FLANG). Using an available simple sequence repeat genetic linkage map, 23 putative QTLs for FLL, FLW, FLA, and FLANG were detected on chromosomes 1B, 2B, 3A, 3D, 4B, 5A, 6B, 7B, and 7D. Individual QTL explained 4.3-68.52% of the phenotypic variance in different environments. Four QTLs for FLL, two for FLW, four for FLA, and five for FLANG were detected in at least two environments. Positive alleles of 17 QTLs for flag leaf-related traits originated from ND3331 and 6 originated from Zang1817. QTLs with pleiotropic effects or multiple linked QTL were also identified on chromosomes 1B, 4B, and 5A; these are potential target regions for fine-mapping and marker-assisted selection in wheat breeding programs.

Bundle sheath lignification mediates the linkage of leaf hydraulics and venation.

PubMed

Ohtsuka, Akihiro; Sack, Lawren; Taneda, Haruhiko

2018-02-01

The lignification of the leaf vein bundle sheath (BS) has been observed in many species and would reduce conductance from xylem to mesophyll. We hypothesized that lignification of the BS in lower-order veins would provide benefits for water delivery through the vein hierarchy but that the lignification of higher-order veins would limit transport capacity from xylem to mesophyll and leaf hydraulic conductance (K leaf ). We further hypothesized that BS lignification would mediate the relationship of K leaf to vein length per area. We analysed the dependence of K leaf , and its light response, on the lignification of the BS across vein orders for 11 angiosperm tree species. Eight of 11 species had lignin deposits in the BS of the midrib, and two species additionally only in their secondary veins, and for six species up to their minor veins. Species with lignification of minor veins had a lower hydraulic conductance of xylem and outside-xylem pathways and lower K leaf . K leaf could be strongly predicted by vein length per area and highest lignified vein order (R 2  = .69). The light-response of K leaf was statistically independent of BS lignification. The lignification of the BS is an important determinant of species variation in leaf and thus whole plant water transport. © 2017 John Wiley & Sons Ltd.

Vulnerability of native savanna trees and exotic Khaya senegalensis to seasonal drought.

PubMed

Arndt, Stefan K; Sanders, Gregor J; Bristow, Mila; Hutley, Lindsay B; Beringer, Jason; Livesley, Stephen J

2015-07-01

Seasonally dry ecosystems present a challenge to plants to maintain water relations. While native vegetation in seasonally dry ecosystems have evolved specific adaptations to the long dry season, there are risks to introduced exotic species. African mahogany, Khaya senegalensis Desr. (A. Juss.), is an exotic plantation species that has been introduced widely in Asia and northern Australia, but it is unknown if it has the physiological or phenotypic plasticity to cope with the strongly seasonal patterns of water availability in the tropical savanna climate of northern Australia. We investigated the gas exchange and water relations traits and adjustments to seasonal drought in K. senegalensis and native eucalypts (Eucalyptus tetrodonta F. Muell. and Corymbia latifolia F. Muell.) in a savanna ecosystem in northern Australia. The native eucalypts did not exhibit any signs of drought stress after 3 months of no rainfall and probably had access to deeper soil moisture late into the dry season. Leaf water potential, stomatal conductance, transpiration and photosynthesis all remained high in the dry season but osmotic adjustment was not observed. Overstorey leaf area index (LAI) was 0.6 in the native eucalypt savanna and did not change between wet and dry seasons. In contrast, the K. senegalensis plantation in the wet season was characterized by a high water potential, high stomatal conductance and transpiration and a high LAI of 2.4. In the dry season, K. senegalensis experienced mild drought stress with a predawn water potential -0.6 MPa. Overstorey LAI was halved, and stomatal conductance and transpiration drastically reduced, while minimum leaf water potentials did not change (-2 MPa) and no osmotic adjustment occurred. Khaya senegalensis exhibited an isohydric behaviour and also had a lower hydraulic vulnerability to cavitation in leaves, with a P50 of -2.3 MPa. The native eucalypts had twice the maximum leaf hydraulic conductance but a much higher P50 of -1.5 MPa. Khaya senegalensis has evolved in a wet-dry tropical climate in West Africa (600-800 mm) and appears to be well suited to the seasonal savanna climate of northern Australia. The species exhibited a large phenotypic plasticity through leaf area adjustments and conservative isohydric behaviour in the 6 months dry season while operating well above its critical hydraulic threshold. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Environmental control of CO2-assimilation and leaf conductance in Larix decidua Mill. : I. A comparison of contrasting natural environments.

PubMed

Benecke, U; Schulze, E -D; Matyssek, R; Havranek, W M

1981-08-01

CO 2 -assimilation and leaf conductance of Larix decidua Mill. were measured in the field at high (Patscherkofel, Austria) and low (Bayreuth, Germany) elevation in Europe, and outside its natural range along an altitudinal gradient in New Zealand.Phenology of leaf and stem growth showed New Zealand sites to have much longer growing seasons than in Europe, so that the timberline (1,330 m) season was almost twice as long as at the Austrian timberline (1,950 m).The maximum rates of photosynthesis, A max , were similar at all sites after completion of leaf growth, namely 3 to 3.5 μmol m -2 s -1 . Only the sun needles of the Bayreuth tree reached 3.5 to 5 μmol m -2 s -1 . Light response curves for CO 2 -assimilation changed during leaf ontogeny, the slope being less in young than in adult leaves. The temperature optimum for 90% of maximum photosynthesis was at all sites similar between ca. 12-28°C for much of the summer. Only at the cooler high altitude timberline sites were optima lower at ca. 10-16°C in developing needles during early summer.A linear correlation existed between A max and leaf conductance at A max , and this showed no difference between the sites except for sun needles at Bayreuth.Leaf conductance responded strongly to light intensity and this was concurrent with the light response of CO 2 -uptake. A short-term and a long-term effect were differentiated. With increasing age maximum rates of CO 2 -uptake and leaf conductance at A max increased, whereas short-term response during changes in light declined. The stomata became less responsive with increasing age and tended to remain open. The stomatal responses to light have a significant effect on the water use efficiency during diurnal courses. A higher water use efficiency was found for similar atmospheric conditions in spring than in autumn.Stomata responded with progressive closure to declining air humidity in a similar manner under dissimilar climates. Humidity response thus showed insensitivity to habitat differences.From the diurnal course of gas-exchange stomata were more closed at timberline (1,330 m) than at lower elevations but this did not lead to corresponding site differences in CO 2 -exchange suggesting Larix may not be operating at high water use efficiency when air is humid.The main difference between habitats studied was in the time necessary for completion of needle development. Similarity in photosynthesis and leaf conductance existed between sites when tree foliage was compared at the same stage of development. Length of growing season and time requirement for foliar development appear to be a principle factor in the carbon balance of deciduous species. The evergreen habit may be more effective in counterbalancing the effects of cool short summers.

Differences in properties and proteomes of the midribs contribute to the size of the leaf angle in two near-isogenic maize lines.

PubMed

Wang, Ning; Cao, Di; Gong, Fangping; Ku, Lixia; Chen, Yanhui; Wang, Wei

2015-10-14

The midrib of maize leaves provides the primary support for the blade and is largely associated with leaf angle size. To elucidate the role of the midrib in leaf angle formation, the maize line Shen137 (larger leaf angle) and a near isogenic line (NIL, smaller leaf angle) were used in the present study. The results of the analysis showed that both the puncture forces and proximal collenchyma number of the midribs of the first and second leaves above the ear were higher in NIL than in Shen137. Comparative proteomic analysis was performed to reveal protein profile differences in the midribs of the 5th, 10th and 19th newly expanded leaves between Shen137 and NIL. Quantitative analysis of 24 identified midrib proteins indicated that the maximum changes in abundance of 22 proteins between Shen137 and NIL appeared at the 10th leaf stage, of which phosphoglycerate kinase, adenosine kinase, fructose-bisphosphate aldolase and adenylate kinase were implicated in glycometabolism. Thus, glycometabolism might be associated with leaf angle formation and the physical and mechanical properties of the midribs. These results provide insight into the mechanism underlying maize leaf angle formation. Copyright © 2015 Elsevier B.V. All rights reserved.

How to pattern a leaf.

PubMed

Bolduc, N; O'Connor, D; Moon, J; Lewis, M; Hake, S

2012-01-01

Leaf development presents a tremendous resource for tackling the question of patterning in biology. Leaves can be simple or highly dissected. They may have elaborated parts such as the tendrils of a pea leaf or the rolled blade of a carnivorous pitcher plant. Despite the variation in size, shape, and function, all leaves initiate in the same manner: from the flanks of a meristem. The maize leaf is useful for analysis of patterning due to the wealth of mutants and the distinct tissues along the proximal distal axis. The blade is distal, the sheath is proximal, and the ligule forms at the blade/sheath boundary. Establishment of this boundary involves the transcription factors LIGULELESS1 and LIGULELESS2 and the kinase LIGULELESS NARROW. The meristem-specific protein KNOTTED1 (KN1) binds and modulates the lg2 gene. Given the localization of KN1 at the proximal end of the leaf from the time of inception, we hypothesize that KN1 has a role in establishing the very proximal end of the leaf, whereas an auxin maximum guides the growing distal tip.

Mycorrhizal inoculation as a tool for sustainable bio-engineering measures in steep alpine environments? - Results of a three year field experiment

NASA Astrophysics Data System (ADS)

Bast, Alexander; Wilcke, Wolfgang; Lüscher, Peter; Graf, Frank; Gärtner, Holger

2013-04-01

Global warming is anticipated to result in an increase of heavy precipitation events. In vegetation-free, steep Alpine areas intense rain fall events have distinct influences on erosional processes on slopes. These processes and (shallow) mass movements are directly linked with torrential rain falls, and for this lead to high erosion rates in those regions, resulting in an increased natural and socio-economic damage potential. For restoring and managing erosion-prone sites, bioengineering measures as a tool for hazard prevention gain more importance. Due to the rough environmental conditions, and hence, reduced germination capability and sprout vigour, it is difficult to establish a dense cover of pioneer vegetation. Thus, the question is what can be done to give planted saplings within bioengineering projects maximum support, to develop their above- and belowground structures to promote slope stabilization. Green-house and laboratory experiments have shown that mycorrhizal inoculum has a positive impact on plant development and soil structure, e.g. the formation of (stable) aggregates within several months. Based on these promising results, we intended to apply mycorrhizal inoculation in a field-experiment. In May 2010, we established experimental plots at an erosion-prone talus slope (inclination: ~40 - 45 °; elevation 1220 - 1360 m a.s.l.), located in the Eastern Swiss Alps. The slope, consisting of moraine and denudation-derived substrate, shows high geomorphic activity (e.g. debris flows, rill erosion). Two slope areas, 10m wide and 32m long, were stabilized with 1200 plants each. Additionally, mycorrhiza inoculum (INOQ Forst, 40 ml/plant) was added to one of the two areas. Within the stabilized areas, a mixture of eight saplings was planted per running meter in 15 rows. The assortment included four saplings of green alder and two of purple willow, as well as one tree (maple, birch, ash) and shrub species (e.g. guelder rose, honeysuckle). Finally, both areas were hand-seeded with an Alpine seed-mixture. In addition, a third was selected but not treated, reflecting the natural conditions and serving as a control. Next to analysing aboveground whole-plant traits (e.g. plant height, crown diameter, stem thickness) and leaf traits (e.g. specific leaf area, leaf size, leaf dry matter content, nitrogen and potassium analyses), we also focused on belowground properties. Undisturbed soil cores (0-20cm in depth) allow a determination of a aggregate stability coefficient, the aggregate-size development, as well as root traits (e.g. root length density, fine(root)diameter). Linear mixed-effect models and testing a posteriori contrasts permit a comparison between the different treatments. Preliminary results indicate, that four months after stabilization plant mortality was high over the two treatments, but it was significantly less on the inoculated treatment. In general plant and leaf traits are showing, that plant vitality is higher at the mycorrhizal-treated plots. Examination of belowground properties yield surprising results; the non-inoculated treatment is showing higher aggregate stability coefficients and higher root length density, which is in contrast to laboratory results. Our contribution will highlight the results of the entire three year field experiment.

Measuring fraction of intercepted photosynthetically active radiation with a ceptometer: the importance of adopting a universal methodological approach

USDA-ARS?s Scientific Manuscript database

It is desirable to be able to predict above ground biomass production indirectly, without extensive sampling or destructive harvesting. Leaf area index (LAI) is the amount of leaf surface area per ground area and is an important parameter in ecophysiology. As LAI increases, the photosynthetically ...

EPIC-Simulated and MODIS-Derived Leaf Area Index (LAI) Comparisons Across mMltiple Spatial Scales RSAD Oral Poster based session

EPA Science Inventory

Leaf Area Index (LAI) is an important parameter in assessing vegetation structure for characterizing forest canopies over large areas at broad spatial scales using satellite remote sensing data. However, satellite-derived LAI products can be limited by obstructed atmospheric cond...

Long-term impact of Ophiostoma novo-ulmi on leaf traits and transpiration of branches in the Dutch elm hybrid ‘Dodoens’

PubMed Central

Plichta, Roman; Urban, Josef; Gebauer, Roman; Dvořák, Miloň; Ďurkovič, Jaroslav

2016-01-01

To better understand the long-term impact of Ophiostoma novo-ulmi Brasier on leaf physiology in ‘Dodoens’, a Dutch elm disease-tolerant hybrid, measurements of leaf area, leaf dry mass, petiole anatomy, petiole hydraulic conductivity, leaf and branch water potential, and branch sap flow were performed 3 years following an initial artificial inoculation. Although fungal hyphae were detected in fully expanded leaves, neither anatomical nor morphological traits were affected, indicating that there was no impact from the fungal hyphae on the leaves during leaf expansion. In contrast, however, infected trees showed both a lower transpiration rate of branches and a lower sap flow density. The long-term persistence of fungal hyphae inside vessels decreased the xylem hydraulic conductivity, but stomatal regulation of transpiration appeared to be unaffected as the leaf water potential in both infected and non-infected trees was similarly driven by the transpirational demands. Regardless of the fungal infection, leaves with a higher leaf mass per area ratio tended to have a higher leaf area-specific conductivity. Smaller leaves had an increased number of conduits with smaller diameters and thicker cell walls. Such a pattern could increase tolerance towards hydraulic dysfunction. Measurements of water potential and theoretical xylem conductivity revealed that petiole anatomy could predict the maximal transpiration rate. Three years following fungal inoculation, phenotypic expressions for the majority of the examined traits revealed a constitutive nature for their possible role in Dutch elm disease tolerance of ‘Dodoens’ trees. PMID:26843210

Relationships Among Ecologically Important Dimensions of Plant Trait Variation in Seven Neotropical Forests

PubMed Central

Wright, Ian J.; Ackerly, David D.; Bongers, Frans; Harms, Kyle E.; Ibarra-Manriquez, Guillermo; Martinez-Ramos, Miguel; Mazer, Susan J.; Muller-Landau, Helene C.; Paz, Horacio; Pitman, Nigel C. A.; Poorter, Lourens; Silman, Miles R.; Vriesendorp, Corine F.; Webb, Cam O.; Westoby, Mark; Wright, S. Joseph

2007-01-01

Background and Aims When ecologically important plant traits are correlated they may be said to constitute an ecological ‘strategy’ dimension. Through identifying these dimensions and understanding their inter-relationships we gain insight into why particular trait combinations are favoured over others and into the implications of trait differences among species. Here we investigated relationships among several traits, and thus the strategy dimensions they represented, across 2134 woody species from seven Neotropical forests. Methods Six traits were studied: specific leaf area (SLA), the average size of leaves, seed and fruit, typical maximum plant height, and wood density (WD). Trait relationships were quantified across species at each individual forest as well as across the dataset as a whole. ‘Phylogenetic’ analyses were used to test for correlations among evolutionary trait-divergences and to ascertain whether interspecific relationships were biased by strong taxonomic patterning in the traits. Key Results The interspecific and phylogenetic analyses yielded congruent results. Seed and fruit size were expected, and confirmed, to be tightly related. As expected, plant height was correlated with each of seed and fruit size, albeit weakly. Weak support was found for an expected positive relationship between leaf and fruit size. The prediction that SLA and WD would be negatively correlated was not supported. Otherwise the traits were predicted to be largely unrelated, being representatives of putatively independent strategy dimensions. This was indeed the case, although WD was consistently, negatively related to leaf size. Conclusions The dimensions represented by SLA, seed/fruit size and leaf size were essentially independent and thus conveyed largely independent information about plant strategies. To a lesser extent the same was true for plant height and WD. Our tentative explanation for negative WD–leaf size relationships, now also known from other habitats, is that the traits are indirectly linked via plant hydraulics. PMID:16595553

Describing the physiological responses of different rice genotypes to salt stress using sigmoid and piecewise linear functions.

PubMed

Radanielson, Ando M; Angeles, Olivyn; Li, Tao; Ismail, Abdelbagi M; Gaydon, Donald S

2018-05-01

Rice is the staple food for almost half of the world population. In South and South East Asia, about 40% of rice production is from deltaic regions that are vulnerable to salt stress. A quantitative approach was developed for characterizing genotypic variability in biomass production, leaf transpiration rate and leaf net photosynthesis responses to salinity during the vegetative stage, with the aim of developing efficient screening protocols to accelerate breeding varieties adapted to salt-affected areas. Three varieties were evaluated in pots under greenhouse conditions and in the field, with average soil salinity ranging from 2 to 12 dS m -1 . Plant biomass, net photosynthesis rate, leaf transpiration rate and leaf conductance were measured at regular intervals. Crop responses were fitted using a logistic function with three parameters: 1) maximum rate under control conditions (Y max ), 2) salinity level for 50% of reduction (b), and 3) rate of reduction ( a) . Variation in the three parameters correlated significantly with variation in plant biomass production under increasing salinity. Salt stress levels that caused 50% reduction in net leaf photosynthesis and transpiration rates were higher in the tolerant genotype BRRI Dhan47 (16.5 dS m -1 and 14.3 dS m -1 , respectively) than the sensitive genotype IR29 (11.1 dS m -1 and 6.8 dS m -1 ). In BRRI Dhan47, the threshold beyond which growth was significantly reduced was above 5 dS m -1 and the rate of growth reduction beyond this threshold was as low as 4% per unit increase in salinity. This quantitative approach to screening for salinity tolerance in rice offers a means to better understand rice growth under salt stress and, using simulation modelling, can provide an improved tool for varietal characterization.

Global patterns in leaf 13C discrimination and implications for studies of past and future climate

PubMed Central

Diefendorf, Aaron F.; Mueller, Kevin E.; Wing, Scott. L.; Koch, Paul L.; Freeman, Katherine H.

2010-01-01

Fractionation of carbon isotopes by plants during CO2 uptake and fixation (Δleaf) varies with environmental conditions, but quantitative patterns of Δleaf across environmental gradients at the global scale are lacking. This impedes interpretation of variability in ancient terrestrial organic matter, which encodes climatic and ecological signals. To address this problem, we converted 3,310 published leaf δ13C values into mean Δleaf values for 334 woody plant species at 105 locations (yielding 570 species-site combinations) representing a wide range of environmental conditions. Our analyses reveal a strong positive correlation between Δleaf and mean annual precipitation (MAP; R2 = 0.55), mirroring global trends in gross primary production and indicating stomatal constraints on leaf gas-exchange, mediated by water supply, are the dominant control of Δleaf at large spatial scales. Independent of MAP, we show a lesser, negative effect of altitude on Δleaf and minor effects of temperature and latitude. After accounting for these factors, mean Δleaf of evergreen gymnosperms is lower (by 1–2.7‰) than for other woody plant functional types (PFT), likely due to greater leaf-level water-use efficiency. Together, environmental and PFT effects contribute to differences in mean Δleaf of up to 6‰ between biomes. Coupling geologic indicators of ancient precipitation and PFT (or biome) with modern Δleaf patterns has potential to yield more robust reconstructions of atmospheric δ13C values, leading to better constraints on past greenhouse-gas perturbations. Accordingly, we estimate a 4.6‰ decline in the δ13C of atmospheric CO2 at the onset of the Paleocene-Eocene Thermal Maximum, an abrupt global warming event ∼55.8 Ma. PMID:20231481

A Method for Calculating the Area of Zostera marina Leaves from Digital Images with Noise Induced by Humidity Content

PubMed Central

Leal-Ramirez, Cecilia

2014-01-01

Despite the ecological importance of eelgrass, nowadays anthropogenic influences have produced deleterious effects in many meadows worldwide. Transplantation plots are commonly used as a feasible remediation scheme. The characterization of eelgrass biomass and its dynamics is an important input for the assessment of the overall status of both natural and transplanted populations. Particularly, in restoration plots it is desirable to obtain nondestructive assessments of these variables. Allometric models allow the expression of above ground biomass and productivity of eelgrass in terms of leaf area, which provides cost effective and nondestructive assessments. Leaf area in eelgrass can be conveniently obtained by the product of associated length and width. Although these variables can be directly measured on most sampled leaves, digital image methods could be adapted in order to simplify measurements. Nonetheless, since width to length ratios in eelgrass leaves could be even negligible, noise induced by leaf humidity content could produce misidentification of pixels along the peripheral contour of leaves images. In this paper, we present a procedure aimed to produce consistent estimations of eelgrass leaf area in the presence of the aforementioned noise effects. Our results show that digital image procedures can provide reliable, nondestructive estimations of eelgrass leaf area. PMID:24892089

In vitro callus and in vivo leaf extract of Gymnema sylvestre stimulate β-cells regeneration and anti-diabetic activity in Wistar rats.

PubMed

Ahmed, A Bakrudeen Ali; Rao, A S; Rao, M V

2010-11-01

A methanol extract of Gymnema sylvestre leaf and callus showed anti-diabetic activities through regenerating β-cells. Optimum callus was developed under stress conditions of blue light with 2,4-D (1.5 mg/l) and KN (0.5 mg/l), which induced maximum biomass of green compact callus at 45 days, as determined by growth curve analysis. Leaf and optimum callus extracts contains gymnemic acid, which was analyzed using TLC, HPTLC and HPLC methods. The research reported here deals with leaf and callus extracts of G. sylvestre, which significantly increase the weight of the whole body, liver, pancreas and liver glycogen content in alloxan-induced diabetic rats (Wistar rats). The gymnemic acid of leaf and callus extracts significantly increases the regeneration of β-cells in treated rats, when compared with the standard diabetic rats. It could have potential as a pharmaceutical drug for insulin-dependent diabetes mellitus (IDDM). Copyright © 2010 Elsevier GmbH. All rights reserved.

Fast and accurate estimation of the covariance between pairwise maximum likelihood distances.

PubMed

Gil, Manuel

2014-01-01

Pairwise evolutionary distances are a model-based summary statistic for a set of molecular sequences. They represent the leaf-to-leaf path lengths of the underlying phylogenetic tree. Estimates of pairwise distances with overlapping paths covary because of shared mutation events. It is desirable to take these covariance structure into account to increase precision in any process that compares or combines distances. This paper introduces a fast estimator for the covariance of two pairwise maximum likelihood distances, estimated under general Markov models. The estimator is based on a conjecture (going back to Nei & Jin, 1989) which links the covariance to path lengths. It is proven here under a simple symmetric substitution model. A simulation shows that the estimator outperforms previously published ones in terms of the mean squared error.

Fast and accurate estimation of the covariance between pairwise maximum likelihood distances

PubMed Central

2014-01-01

Pairwise evolutionary distances are a model-based summary statistic for a set of molecular sequences. They represent the leaf-to-leaf path lengths of the underlying phylogenetic tree. Estimates of pairwise distances with overlapping paths covary because of shared mutation events. It is desirable to take these covariance structure into account to increase precision in any process that compares or combines distances. This paper introduces a fast estimator for the covariance of two pairwise maximum likelihood distances, estimated under general Markov models. The estimator is based on a conjecture (going back to Nei & Jin, 1989) which links the covariance to path lengths. It is proven here under a simple symmetric substitution model. A simulation shows that the estimator outperforms previously published ones in terms of the mean squared error. PMID:25279263

Optimal balance of water use efficiency and leaf construction cost with a link to the drought threshold of the desert steppe ecotone in northern China.

PubMed

Wei, Haixia; Luo, Tianxiang; Wu, Bo

2016-09-01

In arid environments, a high nitrogen content per leaf area (Narea) induced by drought can enhance water use efficiency (WUE) of photosynthesis, but may also lead to high leaf construction cost (CC). Our aim was to investigate how maximizing Narea could balance WUE and CC in an arid-adapted, widespread species along a rainfall gradient, and how such a process may be related to the drought threshold of the desert-steppe ecotone in northern China. Along rainfall gradients with a moisture index (MI) of 0·17-0·41 in northern China and the northern Tibetan Plateau, we measured leaf traits and stand variables including specific leaf area (SLA), nitrogen content relative to leaf mass and area (Nmass, Narea) and construction cost (CCmass, CCarea), δ(13)C (indicator of WUE), leaf area index (LAI) and foliage N-pool across populations of Artemisia ordosica In samples from northern China, a continuous increase of Narea with decreasing MI was achieved by a higher Nmass and constant SLA (reduced LAI and constant N-pool) in high-rainfall areas (MI > 0·29), but by a lower SLA and Nmass (reduced LAI and N-pool) in low-rainfall areas (MI ≤ 0·29). While δ(13)C, CCmass and CCarea continuously increased with decreasing MI, the low-rainfall group had higher Narea and δ(13)C at a given CCarea, compared with the high-rainfall group. Similar patterns were also found in additional data for the same species in the northern Tibetan Plateau. The observed drought threshold where MI = 0·29 corresponded well to the zonal boundary between typical and desert steppes in northern China. Our data indicated that below a climatic drought threshold, drought-resistant plants tend to maximize their intrinsic WUE through increased Narea at a given CCarea, which suggests a linkage between leaf functional traits and arid vegetation zonation. © The Author 2016. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Optimal balance of water use efficiency and leaf construction cost with a link to the drought threshold of the desert steppe ecotone in northern China

PubMed Central

Wei, Haixia; Luo, Tianxiang; Wu, Bo

2016-01-01

Background and Aims In arid environments, a high nitrogen content per leaf area (Narea) induced by drought can enhance water use efficiency (WUE) of photosynthesis, but may also lead to high leaf construction cost (CC). Our aim was to investigate how maximizing Narea could balance WUE and CC in an arid-adapted, widespread species along a rainfall gradient, and how such a process may be related to the drought threshold of the desert–steppe ecotone in northern China. Methods Along rainfall gradients with a moisture index (MI) of 0·17–0·41 in northern China and the northern Tibetan Plateau, we measured leaf traits and stand variables including specific leaf area (SLA), nitrogen content relative to leaf mass and area (Nmass, Narea) and construction cost (CCmass, CCarea), δ13C (indicator of WUE), leaf area index (LAI) and foliage N-pool across populations of Artemisia ordosica. Key Results In samples from northern China, a continuous increase of Narea with decreasing MI was achieved by a higher Nmass and constant SLA (reduced LAI and constant N-pool) in high-rainfall areas (MI > 0·29), but by a lower SLA and Nmass (reduced LAI and N-pool) in low-rainfall areas (MI ≤ 0·29). While δ13C, CCmass and CCarea continuously increased with decreasing MI, the low-rainfall group had higher Narea and δ13C at a given CCarea, compared with the high-rainfall group. Similar patterns were also found in additional data for the same species in the northern Tibetan Plateau. The observed drought threshold where MI = 0·29 corresponded well to the zonal boundary between typical and desert steppes in northern China. Conclusions Our data indicated that below a climatic drought threshold, drought-resistant plants tend to maximize their intrinsic WUE through increased Narea at a given CCarea, which suggests a linkage between leaf functional traits and arid vegetation zonation. PMID:27443298

[Effects of forest gap size on the architecture of Quercus variablis seedlings on the south slope of Qinling Mountains, west China].

PubMed

Yu, Bi-yun; Zhang, Wen-hui; He, Ting; You, Jian-jian; Li, Gang

2014-12-01

Typical sampling method was conducted to survey the effects of forest gap size on branch architecture, leaf characteristics and their vertical distribution of Quercus variablis seedlings from different size gaps in natural secondary Q. variablis thinning forest, on the south slope of Qinling Mountains. The results showed that gap size significantly affected the diameter, crown area of Q. variablis seedlings. The gap size positively correlated with diameter and negatively correlated with crown area, while it had no significant impact on seedling height, crown length and crown rates. The overall bifurcation ratio, stepwise bifurcation ratio, and ratio of branch diameter followed as large gap > middle gap > small gap > understory. The vertical distribution of first-order branches under different size gaps mainly concentrated at the middle and upper part of trunk, larger diameter first-order branches were mainly distributed at the lower part of trunk, and the angle of first-order branch increased at first and then declined with the increasing seedling height. With the increasing forest gap size, the leaf length, leaf width and average leaf area of seedlings all gradually declined, while the average leaf number per plant and relative total leaf number increased, the leaf length-width ratio kept stable, the relative leaf number was mainly distributed at the middle and upper parts of trunk, the changes of leaf area index was consistent with the change of the relative total number of leaves. There was no significant difference between the diameters of middle gap and large gap seedlings, but the diameter of middle gap seedlings was higher than that of large gap, suggesting the middle gap would benefit the seedlings regeneration and high-quality timber cultivation. To promote the regeneration of Q. variabilis seedlings, and to cultivate high-quality timber, appropriate thinning should be taken to increase the number of middle gaps in the management of Q. variabilis forest.

Effect of Moringa oleifera Lam. leaf powder on the pharmacokinetics of nevirapine in HIV-infected adults: a one sequence cross-over study.

PubMed

Monera-Penduka, Tsitsi G; Maponga, Charles C; Wolfe, Alan R; Wiesner, Lubbe; Morse, Gene D; Nhachi, Charles F B

2017-01-01

Moringa oleifera Lam., an herb commonly consumed by HIV-infected people on antiretroviral therapy, inhibits cytochrome P450 3A4, 1A2 and 2D6 activity in vitro; and may alter the pharmacokinetics (PK) of antiretroviral drugs metabolized via the same pathways. However, in vitro drug interaction activity may not translate to a clinically significant effect. Therefore, the effect of moringa leaf powder on the PK of nevirapine in HIV-infected people was investigated. Adult patients at steady-state dosing with nevirapine were admitted for 12-h intensive PK sampling following a 21-day herbal medicine washout. Blood sampling was repeated after 14 days of nevirapine and moringa (1.85 g leaf powder/day) co-administration. Nevirapine plasma concentrations were determined by liquid chromatography-tandem mass spectrometry. To assess the effect of moringa on nevirapine PK, the change in nevirapine area under the plasma concentration-time curve (AUC) was determined. The mean difference in pre- and post-moringa nevirapine, maximum concentration (C max ) and concentration at 12 h (C 12h ) were also calculated. The PK parameters were compared by assessing the post/pre geometric mean ratios (GMRs) and associated 90% confidence intervals (CIs). Pharmacokinetics analyses were performed on the results from 11 participants for whom complete data were obtained. The post/pre GMRs and associated 90% CIs for nevirapine were 1.07 (1.00-1.14) for the AUC; 1.06 (0.98-1.16) for C max and 1.03 (0.92-1.16) for C 12h . Co-administration of Moringa oleifera Lam. leaf powder at the traditional dose did not significantly alter the steady-state PK of nevirapine. Trial registration number NCT01410058 (ClinicalTrials.gov).

Enhancement of germination, growth, and photosynthesis in soybean by pre-treatment of seeds with magnetic field.

PubMed

Shine, M B; Guruprasad, K N; Anand, Anjali

2011-09-01

Experiments were conducted to study the effect of static magnetic fields on the seeds of soybean (Glycine max (L.) Merr. var: JS-335) by exposing the seeds to different magnetic field strengths from 0 to 300 mT in steps of 50 mT for 30, 60, and 90 min. Treatment with magnetic fields improved germination-related parameters like water uptake, speed of germination, seedling length, fresh weight, dry weight and vigor indices of soybean seeds under laboratory conditions. Improvement over untreated control was 5-42% for speed of germination, 4-73% for seedling length, 9-53% for fresh weight, 5-16% for dry weight, and 3-88% and 4-27% for vigor indices I and II, respectively. Treatment of 200 mT (60 min) and 150 mT (60 min), which were more effective than others in increasing most of the seedling parameters, were further explored for their effect on plant growth, leaf photosynthetic efficiency, and leaf protein content under field conditions. Among different growth parameters, leaf area, and leaf fresh weight showed maximum enhancement (more than twofold) in 1-month-old plants. Polyphasic chlorophyll a fluorescence (OJIP) transients from magnetically treated plants gave a higher fluorescence yield at the J-I-P phase. The total soluble protein map (SDS-polyacrylamide gel) of leaves showed increased intensities of the bands corresponding to a larger subunit (53 KDa) and smaller subunit (14 KDa) of Rubisco in the treated plants. We report here the beneficial effect of pre-sowing magnetic treatment for improving germination parameters and biomass accumulation in soybean. Copyright © 2011 Wiley-Liss, Inc.

Inoculation of hybrid poplar with the endophytic bacterium Enterobacter sp. 638 increases biomass but does not impact leaf level physiology

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rogers, A.; McDonald, K.; Muehlbauer, M. F.

Endophytic bacteria have been shown to provide several advantages to their host, including enhanced growth. Inoculating biofuel species with endophytic bacteria is therefore an attractive option to increase the productivity of biofuel feedstocks. Here, we investigated the effect of inoculating hard wood cuttings of Populus deltoides Bartr. x Populus. nigra L. clone OP367 with Enterobacter sp. 638. After 17 weeks, plants inoculated with Enterobacter sp. 638 had 55% greater total biomass than un-inoculated control plants. Study of gas exchange and fluorescence in developing and mature leaves over a diurnal cycle and over a 5 week measurement campaign revealed no effectsmore » of inoculation on photosynthesis, stomatal conductance, photosynthetic water use efficiency or the maximum and operating efficiency of photosystem II. However, plants inoculated with Enterobacter sp. 638 had a canopy that was 39% larger than control plants indicating that the enhanced growth was fueled by increased leaf area, not by improved physiology. Leaf nitrogen content was determined at two stages over the 5 week measurement period. No effect of Enterobacter sp. 638 on leaf nitrogen content was found indicating that the larger plants were acquiring sufficient nitrogen. Enterobacter sp. 638 lacks the genes for N{sub 2} fixation, therefore the increased availability of nitrogen likely resulted from enhanced nitrogen acquisition by the 84% larger root system. These data show that Enterobacter sp. 638 has the potential to dramatically increase productivity in poplar. If fully realized in the production environment, these results indicate that an increase in the environmental and economic viability of poplar as a biofuel feedstock is possible when inoculated with endophytic bacteria like Enterobacter sp. 638.« less

Physiological and leaf metabolome changes in the xerohalophyte species Atriplex halimus induced by salinity.

PubMed

Bendaly, Alia; Messedi, Dorsaf; Smaoui, Abderrazak; Ksouri, Riadh; Bouchereau, Alain; Abdelly, Chedly

2016-06-01

Atriplex halimus is a xerohalophyte plant, which could be used as cash crops. This plant was integrated in Tunisian government programs the aim of which is to rehabilitate saline areas and desert. To investigate its strategies involved in salt tolerance, A. halimus was grown hydroponically under controlled conditions with increasing salinity. Plants were harvested and analyzed after 60 days of treatment. The biomass of A. halimus increased by moderate salinity and decreased significantly at high salinity compared to control plants at 400 mM. Despite of the large amounts of Na(+) observed in the leaves of Atriplex plants, leaf water contents and leaf succulence kept on increasing in treated plants and decreased over 150 mM NaCl. This confirmed the compartmentation and the efficient contribution of Na(+) in the osmotic adjustment. Analysis of the metabolic profiles showed an accumulation of carbohydrates and amino acids. The leaf tissues preferentially stored proline, α alanine and sucrose. Increasing NaCl levels were also accompanied by a significant accumulation of malate in leaves. Involvement of these solutes in osmotic adjustment was considered low. Nevertheless, they seemed to have an important role in controlling photosynthesis which capacity was enhanced by low salinity and decreased with increasing salinity (evaluated by actual photochemical efficiency of photosystem II and chlorophyll contents). The unchanged maximum photochemical efficiency of photosystem II accompanied by the increase of the non-photochemical quenching, the enhancement of the total antioxidant activity and the decrease of the malondialdehyde contents in leaves showed efficient protection of membranes and photosystem II from photo-oxidative damage. This protection seemed to be attributed to proline and sucrose largely accumulated in leaves treated with salt. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

Quantitative limitations to photosynthesis in K deficient sunflower and their implications on water-use efficiency.

PubMed

Jákli, Bálint; Tavakol, Ershad; Tränkner, Merle; Senbayram, Mehmet; Dittert, Klaus

2017-02-01

Potassium (K) is crucial for crop growth and is strongly related to stress tolerance and water-use efficiency (WUE). A major physiological effect of K deficiency is the inhibition of net CO 2 assimilation (A N ) during photosynthesis. Whether this reduction originates from limitations either to photochemical energy conversion or biochemical CO 2 fixation or from a limitation to CO 2 diffusion through stomata and the leaf mesophyll is debated. In this study, limitations to photosynthetic carbon gain of sunflower (Helianthus annuus L.) under K deficiency and PEG- induced water deficit were quantified and their implications on plant- and leaf-scale WUE (WUE P , WUE L ) were evaluated. Results show that neither maximum quantum use efficiency (F v /F m ) nor in-vivo RubisCo activity were directly affected by K deficiency and that the observed impairment of A N was primarily due to decreased CO 2 mesophyll conductance (g m ). K deficiency additionally impaired leaf area development which, together with reduced A N , resulted in inhibition of plant growth and a reduction of WUE P . Contrastingly, WUE L was not affected by K supply which indicated no inhibition of stomatal control. PEG-stress further impeded A N by stomatal closure and resulted in enhanced WUE L and high oxidative stress. It can be concluded from this study that reduction of g m is a major response of leaves to K deficiency, possibly due to changes in leaf anatomy, which negatively affects A N and contributes to the typical symptoms like oxidative stress, growth inhibition and reduced WUE P . Copyright © 2016 Elsevier GmbH. All rights reserved.

Artificial Leaf Based on Artificial Photosynthesis for Solar Fuel Production

DTIC Science & Technology

2017-06-30

AFRL-AFOSR-JP-TR-2017-0054 Artificial Leaf Based on Artificial Photosynthesis for Solar Fuel Production Mamoru Nango NAGOYA INSTITUTE OF TECHNOLOGY...for Solar Fuel Production 5a.  CONTRACT NUMBER 5b.  GRANT NUMBER FA2386-14-1-4015 5c.  PROGRAM ELEMENT NUMBER 61102F 6. AUTHOR(S) Mamoru Nango 5d...density immobilization of the photoreactants in the nanocavity inside PGP. The maximum production efficiency of formic acid inside the nanocavity was

Terrestrial biosphere models underestimate photosynthetic capacity and CO2 assimilation in the Arctic.

PubMed

Rogers, Alistair; Serbin, Shawn P; Ely, Kim S; Sloan, Victoria L; Wullschleger, Stan D

2017-12-01

Terrestrial biosphere models (TBMs) are highly sensitive to model representation of photosynthesis, in particular the parameters maximum carboxylation rate and maximum electron transport rate at 25°C (V c,max.25 and J max.25 , respectively). Many TBMs do not include representation of Arctic plants, and those that do rely on understanding and parameterization from temperate species. We measured photosynthetic CO 2 response curves and leaf nitrogen (N) content in species representing the dominant vascular plant functional types found on the coastal tundra near Barrow, Alaska. The activation energies associated with the temperature response functions of V c,max and J max were 17% lower than commonly used values. When scaled to 25°C, V c,max.25 and J max.25 were two- to five-fold higher than the values used to parameterize current TBMs. This high photosynthetic capacity was attributable to a high leaf N content and the high fraction of N invested in Rubisco. Leaf-level modeling demonstrated that current parameterization of TBMs resulted in a two-fold underestimation of the capacity for leaf-level CO 2 assimilation in Arctic vegetation. This study highlights the poor representation of Arctic photosynthesis in TBMs, and provides the critical data necessary to improve our ability to project the response of the Arctic to global environmental change. No claim to original US Government works. New Phytologist © 2017 New Phytologist Trust.

Terrestrial biosphere models underestimate photosynthetic capacity and CO 2 assimilation in the Arctic

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rogers, Alistair; Serbin, Shawn P.; Ely, Kim S.

Terrestrial biosphere models (TBMs) are highly sensitive to model representation of photosynthesis, in particular the parameters maximum carboxylation rate and maximum electron transport rate at 25°C (V c,max.25 and J max.25, respectively). Many TBMs do not include representation of Arctic plants, and those that do rely on understanding and parameterization from temperate species. We then measured photosynthetic CO 2 response curves and leaf nitrogen (N) content in species representing the dominant vascular plant functional types found on the coastal tundra near Barrow, Alaska. The activation energies associated with the temperature response functions of Vc,max and Jmax were 17% lower thanmore » commonly used values. When scaled to 25°C, Vc,max.25 and J max.25 were two- to five-fold higher than the values used to parameterize current TBMs. This high photosynthetic capacity was attributable to a high leaf N content and the high fraction of N invested in Rubisco. Leaf-level modeling demonstrated that current parameterization of TBMs resulted in a two-fold underestimation of the capacity for leaf-level CO 2 assimilation in Arctic vegetation. Our study highlights the poor representation of Arctic photosynthesis in TBMs, and provides the critical data necessary to improve our ability to project the response of the Arctic to global environmental change.« less

Terrestrial biosphere models underestimate photosynthetic capacity and CO 2 assimilation in the Arctic

DOE PAGES

Rogers, Alistair; Serbin, Shawn P.; Ely, Kim S.; ...

2017-09-06

Terrestrial biosphere models (TBMs) are highly sensitive to model representation of photosynthesis, in particular the parameters maximum carboxylation rate and maximum electron transport rate at 25°C (V c,max.25 and J max.25, respectively). Many TBMs do not include representation of Arctic plants, and those that do rely on understanding and parameterization from temperate species. We then measured photosynthetic CO 2 response curves and leaf nitrogen (N) content in species representing the dominant vascular plant functional types found on the coastal tundra near Barrow, Alaska. The activation energies associated with the temperature response functions of Vc,max and Jmax were 17% lower thanmore » commonly used values. When scaled to 25°C, Vc,max.25 and J max.25 were two- to five-fold higher than the values used to parameterize current TBMs. This high photosynthetic capacity was attributable to a high leaf N content and the high fraction of N invested in Rubisco. Leaf-level modeling demonstrated that current parameterization of TBMs resulted in a two-fold underestimation of the capacity for leaf-level CO 2 assimilation in Arctic vegetation. Our study highlights the poor representation of Arctic photosynthesis in TBMs, and provides the critical data necessary to improve our ability to project the response of the Arctic to global environmental change.« less

New drought indices from the assimilation of satellite data

NASA Astrophysics Data System (ADS)

Calvet, Jean-Christophe; Barbu, Alina; Fairbairn, David

2016-04-01

The current agricultural drought indicators produced by Meteo-France are derived from digital simulations of soil moisture produced by the SURFEX modelling platform. In the framework of the IMAGINES European project, a research was conducted in order to assess the impact on the monitoring of agricultural droughts of the integration of satellite data into SURFEX. A data assimilation system was implemented to this end. It provides simulations of the biomass and leaf area index of straw cereals and grasslands over France. It is shown that these simulations can be improved through the assimilation of satellite products distributed in near-real-time by the Copernicus Global Land service (http://land.copernicus.eu/global/). Reference in situ observations of the agricultural yields show that using satellite data, a significant correlation between the maximum annual above-ground biomass simulated by SURFEX and the agricultural yield at the scale of administrative units (départements) can be achieved. Without satellite data, very low correlations are observed. It is also shown that new 10-day drought indicators, complementary to soil moisture, can be derived from the leaf area index and from the above-ground biomass of vegetation. These demonstration drought monitoring products for the 2008-2013 period are freely available on the project web site (http://fp7-imagines.eu/) for 45 administrative units for cereals and for 48 administrative units for grasslands.

Physiological, vascular and nanomechanical assessment of hybrid poplar leaf traits in micropropagated plants and plants propagated from root cuttings: A contribution to breeding programs.

PubMed

Ďurkovič, Jaroslav; Husárová, Hana; Javoříková, Lucia; Čaňová, Ingrid; Šuleková, Miriama; Kardošová, Monika; Lukáčik, Ivan; Mamoňová, Miroslava; Lagaňa, Rastislav

2017-09-01

Micropropagated plants experience significant stress from rapid water loss when they are transferred from an in vitro culture to either greenhouse or field conditions. This is caused both by inefficient stomatal control of transpiration and the change to a higher light intensity and lower humidity. Understanding the physiological, vascular and biomechanical processes that allow micropropagated plants to modify their phenotype in response to environmental conditions can help to improve both field performance and plant survival. To identify changes between the hybrid poplar [Populus tremula × (Populus × canescens)] plants propagated from in vitro tissue culture and those from root cuttings, we assessed leaf performance for any differences in leaf growth, photosynthetic and vascular traits, and also nanomechanical properties of the tracheary element cell walls. The micropropagated plants showed significantly higher values for leaf area, leaf length, leaf width and leaf dry mass. The greater leaf area and leaf size dimensions resulted from the higher transpiration rate recorded for this stock type. Also, the micropropagated plants reached higher values for chlorophyll a fluorescence parameters and for the nanomechanical dissipation energy of tracheary element cell walls which may indicate a higher damping capacity within the primary xylem tissue under abiotic stress conditions. The performance of the plants propagated from root cuttings was superior for instantaneous water-use efficiency which signifies a higher acclimation capacity to stressful conditions during a severe drought particularly for this stock type. Similarities were found among the majority of the examined leaf traits for both vegetative plant origins including leaf mass per area, stomatal conductance, net photosynthetic rate, hydraulic axial conductivity, indicators of leaf midrib vascular architecture, as well as for the majority of cell wall nanomechanical traits. This research revealed that there were no drawbacks in the leaf physiological performance which could be attributed to the micropropagated plants of fast growing hybrid poplar. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

Molluscs associated with a subtidal Zostera marina L. bed in southern Spain: Linking seasonal changes of fauna and environmental variables

NASA Astrophysics Data System (ADS)

Rueda, Jose L.; Salas, Carmen

2008-08-01

The temporal variation of the molluscan fauna associated with a deep Zostera marina bed (12-14 m depth) in Cañuelo Bay (southern Spain) has been studied in relation to water, sediment and eelgrass variables. Samples of molluscs from the sediment and the eelgrass (5 replicates per season) were seasonally collected using a quadrat of 25 × 25 cm. The water column was characterized by the temperature and chlorophyll a concentration. The grain size distribution of the sediment and percentage of organic matter (%OM) were also studied. Estimations of the shoot density, leaf/rhizome biomass and Leaf Area Index (LAI) have been obtained for each sample. Statistical analyses have been performed with SYSTAT and PRIMER software. A total of 2396 individuals and 85 species of molluscs were collected. The most dominant species were infaunal bivalves such as Tellina distorta (28.1%), Dosinia lupinus, Tellina fabula and Chamelea gallina. The gastropods Jujubinus striatus (4.6%), Nassarius pygmaeus and Bittium reticulatum were the dominant epifaunal species. The most frequent species was T. distorta (100%), followed by other infaunal bivalves such as T. fabula, Solemya togata or Lucinella divaricata. The most frequent gastropods were J. striatus (95%), followed by B. reticulatum, N. pygmaeus, Nassarius reticulatus, Mitrella minor and Smaragdia viridis. The abundance of molluscs displayed significant maximum values in summer and autumn (above 2500 indiv. m -2) and minimum values in spring (below 1500 indiv. m -2). The abundance of the epifauna was related with leaf biomass, whereas that of the infauna was positively related with %OM. The species richness also followed a significant seasonal variation with maximum values in summer (64 species in all summer samples) and minimum values in autumn (44 in all autumn samples), and was positively related with LAI. In both qualitative and quantitative cluster/MDS, samples (replicates) mainly grouped according to the season, with significantly different groupings according to ANOSIM analyses. The studied eelgrass bed is less dense, with a lower leaf biomass, than other European eelgrass beds occurring at shallower depths; however the species richness values are the highest along Europe. The latter could be due to its geographical location in the Alboran Sea, where a confluence of Atlantic, Mediterranean and African fauna occurs.

Stable annual pattern of water use by Acacia tortilis in Sahelian Africa.

PubMed

Do, Frederic C; Rocheteau, Alain; Diagne, Amadou L; Goudiaby, Venceslas; Granier, André; Lhomme, Jean-Paul

2008-01-01

Water use by mature trees of Acacia tortilis (Forsk.) Hayne ssp. raddiana (Savi) Brenan var. raddiana growing in the northern Sahel was continuously recorded over 4 years. Water use was estimated from xylem sap flow measured by transient heat dissipation. Concurrently, cambial growth, canopy phenology, leaf water potential, climatic conditions and soil water availability (SWA) were monitored. In addition to the variation attributable to interannual variation in rainfall, SWA was increased by irrigation during one wet season. The wet season lasted from July to September, and annual rainfall ranged between 146 and 367 mm. The annual amount and pattern of tree water use were stable from year-to-year despite interannual and seasonal variations in SWA in the upper soil layers. Acacia tortilis transpired readily throughout the year, except for one month during the dry season when defoliation was at a maximum. Maximum water use of about 23 l (dm sapwood area)(-2) day(-1) was recorded at the end of the wet season. While trees retained foliage in the dry season, the decline in water use was modest at around 30%. Variation in predawn leaf water potential indicated that the trees were subject to soil water constraint. The rapid depletion of water in the uppermost soil layers after the wet season implies that there was extensive use of water from deep soil layers. The deep soil profile revealed (1) the existence of living roots at 25 m and (2) that the availability of soil water was low (-1.6 MPa) down to the water table at a depth of 31 m. However, transpiration was recorded at a predawn leaf water potential of -2.0 MPa, indicating that the trees used water from both intermediary soil layers and the water table. During the full canopy stage, mean values of whole-tree hydraulic conductance were similar in the wet and dry seasons. We propose that the stability of water use at the seasonal and annual scales resulted from a combination of features, including an extensive rooting habit related to deep water availability and an effective regulation of canopy conductance. Despite a limited effect on tree water use, irrigation during the wet season sharply increased predawn leaf water potential and cambial growth of trunks and branches.

Family differences in equations for predicting biomass and leaf area in Douglas-fir (Pseudotsuga menziesii var. menziesii).

Treesearch

J.B. St. Clair

1993-01-01

Logarithmic regression equations were developed to predict component biomass and leaf area for an 18-yr-old genetic test of Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco var. menziesii) based on stem diameter or cross-sectional sapwood area. Equations did not differ among open-pollinated families in slope, but intercepts...

Allometric method to estimate leaf area index for row crops

USDA-ARS?s Scientific Manuscript database

Leaf area index (LAI) is critical for predicting plant metabolism, biomass production, evapotranspiration, and greenhouse gas sequestration, but direct LAI measurements are difficult and labor intensive. Several methods are available to measure LAI indirectly or calculate LAI using allometric method...

Palisade cell shape affects the light-induced chloroplast movements and leaf photosynthesis.

PubMed

Gotoh, Eiji; Suetsugu, Noriyuki; Higa, Takeshi; Matsushita, Tomonao; Tsukaya, Hirokazu; Wada, Masamitsu

2018-01-24

Leaf photosynthesis is regulated by multiple factors that help the plant to adapt to fluctuating light conditions. Leaves of sun-light-grown plants are thicker and contain more columnar palisade cells than those of shade-grown plants. Light-induced chloroplast movements are also essential for efficient leaf photosynthesis and facilitate efficient light utilization in leaf cells. Previous studies have demonstrated that leaves of most of the sun-grown plants exhibited no or very weak chloroplast movements and could accomplish efficient photosynthesis under strong light. To examine the relationship between palisade cell shape, chloroplast movement and distribution, and leaf photosynthesis, we used an Arabidopsis thaliana mutant, angustifolia (an), which has thick leaves that contain columnar palisade cells similar to those in the sun-grown plants. In the highly columnar cells of an mutant leaves, chloroplast movements were restricted. Nevertheless, under white light condition (at 120 µmol m -2 s -1 ), the an mutant plants showed higher chlorophyll content per unit leaf area and, thus, higher light absorption by the leaves than the wild type, which resulted in enhanced photosynthesis per unit leaf area. Our findings indicate that coordinated regulation of leaf cell shape and chloroplast movement according to the light conditions is pivotal for efficient leaf photosynthesis.

Sediment deposition and production in SE-Asia seagrass meadows

NASA Astrophysics Data System (ADS)

Gacia, E.; Duarte, C. M.; Marbà, N.; Terrados, J.; Kennedy, H.; Fortes, M. D.; Tri, N. H.

2003-04-01

Seagrass meadows play an important role in the trapping and binding of particles in coastal sediments. Yet seagrass may also contribute to sediment production directly, through the deposition of detritus and also the deposition of the associated mineral particles. This study aims at estimating the contribution of different seagrass species growing across an extensive range of deposition to inorganic (carbonate and non-carbonate) and organic sediment production. Total daily deposition measured with sediment traps varied from 18.8 (±2.0) g DW m -2 d -1 in Silaqui (Philippines) to 681.1 (±102) g DW m -2 d -1 in Bay Tien (Vietnam). These measurements correspond to a single sampling event and represent sedimentation conditions during the dry season in SE-Asia coastal areas. Enhalus acoroides was the most common species in the seagrass meadows visited and, together with Thalassia hemprichii, was present at sites from low to very high deposition. Halodule uninervis and Cymodocea species were present in sites from low to medium deposition. The mineral load in seagrass leaves increased with age, and was high in E. acoroides because it had the largest and long-lived leaves (up to 417 mg calcium carbonate per leaf and 507 mg non-carbonate minerals per leaf) and low in H. uninervis with short-lived leaves (4 mg calcium carbonate per leaf and 2 mg non-carbonate minerals per leaf). In SE-Asia seagrass meadows non-carbonate minerals accumulate at slower rates than the production of calcium carbonate by the epiphytic community, consequently the final loads supported by fully grown leaves were, as average, lower than calcium carbonate loads. Our results show that organic and inorganic production of the seagrasses in SE-Asia represents a small contribution (maximum of 15%) of the materials sedimented on a daily base by the water column during the sampling period. The contribution of the carbonate fraction can be locally significant (i.e. 34% in Silaqui) in areas where the depositional flux is low, but is minor (<1%) in sites were siltation is significant (i.e. Umalagan and all the visited sites in Vietnam).

Quantifying multi-dimensional functional trait spaces of trees: empirical versus theoretical approaches

NASA Astrophysics Data System (ADS)

Ogle, K.; Fell, M.; Barber, J. J.

2016-12-01

Empirical, field studies of plant functional traits have revealed important trade-offs among pairs or triplets of traits, such as the leaf (LES) and wood (WES) economics spectra. Trade-offs include correlations between leaf longevity (LL) vs specific leaf area (SLA), LL vs mass-specific leaf respiration rate (RmL), SLA vs RmL, and resistance to breakage vs wood density. Ordination analyses (e.g., PCA) show groupings of traits that tend to align with different life-history strategies or taxonomic groups. It is unclear, however, what underlies such trade-offs and emergent spectra. Do they arise from inherent physiological constraints on growth, or are they more reflective of environmental filtering? The relative importance of these mechanisms has implications for predicting biogeochemical cycling, which is influenced by trait distributions of the plant community. We address this question using an individual-based model of tree growth (ACGCA) to quantify the theoretical trait space of trees that emerges from physiological constraints. ACGCA's inputs include 32 physiological, anatomical, and allometric traits, many of which are related to the LES and WES. We fit ACGCA to 1.6 million USFS FIA observations of tree diameters and heights to obtain vectors of trait values that produce realistic growth, and we explored the structure of this trait space. No notable correlations emerged among the 496 trait pairs, but stepwise regressions revealed complicated multi-variate structure: e.g., relationships between pairs of traits (e.g., RmL and SLA) are governed by other traits (e.g., LL, radiation-use efficiency [RUE]). We also simulated growth under various canopy gap scenarios that impose varying degrees of environmental filtering to explore the multi-dimensional trait space (hypervolume) of trees that died vs survived. The centroid and volume of the hypervolumes differed among dead and live trees, especially under gap conditions leading to low mortality. Traits most predictive of tree-level mortality were maximum tree height, RUE, xylem conducting area, and branch turn-over rate. We are using these hypervolumes as priors to an emulator that approximates the ACGCA, which we are fitting to the FIA data to quantify species-specific trait spectra and to explore factors giving rise to species differences.

Influences of the Tamarisk Leaf Beetle (Diorhabda carinulata) on the diet of insectivorous birds along the Dolores River in Southwestern Colorado

USGS Publications Warehouse

Puckett, Sarah L.; van Riper, Charles

2014-01-01

We examined the effects of a biologic control agent, the tamarisk leaf beetle (Diorhabda carinulata), on native avifauna in southwestern Colorado, specifically, addressing whether and to what degree birds eat tamarisk leaf beetles. In 2010, we documented avian foraging behavior, characterized the arthropod community, sampled bird diets, and undertook an experiment to determine whether tamarisk leaf beetles are palatable to birds. We observed that tamarisk leaf beetles compose 24.0 percent (95-percent-confidence interval, 19.9-27.4 percent) and 35.4 percent (95-percent-confidence interval, 32.4-45.1 percent) of arthropod abundance and biomass in the study area, respectively. Birds ate few tamarisk leaf beetles, despite a superabundance of D. carinulata in the environment. The frequency of occurrence of tamarisk leaf beetles in bird diets was 2.1 percent (95-percent-confidence interval, 1.3- 2.9 percent) by abundance and 3.4 percent (95-percent-confidence interval, 2.6-4.2 percent) by biomass. Thus, tamarisk leaf beetles probably do not contribute significantly to the diets of birds in areas where biologic control of tamarisk is being applied.

MODIS Measures Total U.S. Leaf Area

NASA Technical Reports Server (NTRS)

2002-01-01

This composite image over the continental United States was produced with data acquired by the Moderate-resolution Imaging Spectroradiometer (MODIS) during the period March 24 - April 8, 2000. The image is a map of the density of the plant canopy covering the ground. It is the first in a series of images over the continental U.S. produced by the MODIS Land Discipline Group (refer to this site June 2 and 5 for the next two images in the series). The image is a MODIS data product called 'Leaf Area Index,' which is produced by radiometrically measuring the visible and near infrared energy reflected by vegetation. The Leaf Area Index provides information on the structure of plant canopy, showing how much surface area is covered by green foliage relative to total land surface area. In this image, dark green pixels indicate areas where more than 80 percent of the land surface is covered by green vegetation, light green pixels show where leaves cover about 10 to 50 percent of the land surface, and brown pixels show virtually no leaf coverage. The more leaf area a plant has, the more sunlight it can absorb for photosynthesis. Leaf Area Index is one of a new suite of measurements that scientists use to understand how the Earth's land surfaces are changing over time. Their goal is to use these measurements to refine computer models well enough to simulate how the land biosphere influences the natural cycles of water, carbon, and energy throughout the Earth system. This image is the first of its kind from the MODIS instrument, which launched in December 1999 aboard the Terra spacecraft. MODIS began acquiring scientific data on February 24, 2000, when it first opened its aperture door. The MODIS instrument and Terra spacecraft are both managed by NASA's Goddard Space Flight Center, Greenbelt, MD. Image courtesy Steven Running, MODIS Land Group Member, University of Montana

Paleohydrologic change across the Paleocene-Eocene Thermal Maximum, Bighorn Basin, WY

NASA Astrophysics Data System (ADS)

Baczynski, A. A.; McInerney, F. A.; Wing, S. L.; Kraus, M. J.

2013-12-01

One of the uncertainties in accurately predicting future climate change involves how the hydrologic cycle will respond to increasing pCO2 and temperature. Quantifying the relationship between carbon cycle perturbations and the hydrologic cycle in the geologic past is crucial to understanding and accurately modeling how anthropogenic carbon emissions will affect future changes in the hydrologic cycle. Records of paleohydrologic response to global warming in the geologic past are rare, particularly for continental interiors, where climate model projections of precipitation are highly uncertain. Here we examine hydrogen isotope ratios of leaf waxes as a tool for reconstructing paleohydrologic change in the continental interior of North America across the Paleocene-Eocene Thermal Maximum (PETM), an abrupt, transient episode of extreme global warming ~56 Ma. New hydrogen isotope measurements of leaf-wax n-alkanes from the southeastern Bighorn Basin, Wyoming record two positive shifts during the PETM. n-Alkane δD values first shift to more positive values just after the onset of the carbon isotope excursion and then again higher up in the body of the carbon isotope excursion, with a return to slightly more negative δD values in between. Paleobotanical, paleopedologic, and isotope data from the same field area have suggested that the Bighorn Basin may have experienced a drier or more seasonally dry climate during the PETM. Mean annual precipitation estimates based on paleosol major oxides, soil wetness assessed using the soil morphology index, and an aridity proxy based on differences in δ18O values of tooth enamel in aridity-sensitive and aridity-insensitive mammals each independently suggest a potential two-phase drying within the PETM interval. Similarly, the hydrogen isotope record could reflect two periods of drying, with a return to slightly wetter conditions in between. However, leaf-wax hydrogen isotope ratios reflect not only source water hydrogen isotope values but also deuterium-enrichment resulting from soil evaporation and transpiration. Interpretation of hydrogen isotope records requires consideration of both of these factors. To examine the potential roles of changes in source water isotopic composition and transpirational D-enrichment, we compare the hydrogen isotope ratios of leaf waxes with the oxygen isotope ratios of tooth enamel from Coryphodon, a large herbivore and an obligate drinker. The Coryphodon tooth enamel δ18O record enables us to constrain shifts in surface water isotope values. Relative humidity of paleoenvironments can then be explored using a modified Craig-Gordon model for transpirational D-enrichment. Preliminary calculations suggest that relative humidity increased during the PETM, contrary to the drying suggested by all other aridity proxies. One possibility is that leaf waxes record only the relative humidity at the time of leaf formation. Therefore, the n-alkane δD record could reflect an increase in seasonality of precipitation, with greater relative humidity during the early growing season. To evaluate the validity of this approach, we will systematically examine the assumptions involved in using hydrogen isotope ratios of leaf waxes as a paleoaridity index to evaluate paleohydrologic changes in the Bighorn Basin during the PETM.

Seasonality of isoprenoid emissions from a primary rainforest in central Amazonia

DOE PAGES

Alves, Eliane G.; Jardine, Kolby; Tota, Julio; ...

2016-03-23

Tropical rainforests are an important source of isoprenoid and other volatile organic compound (VOC) emissions to the atmosphere. The seasonal variation of these compounds is however still poorly understood. In this study, vertical profiles of mixing ratios of isoprene, total monoterpenes and total sesquiterpenes, were measured within and above the canopy, in a primary rainforest in central Amazonia, using a proton transfer reaction – mass spectrometer (PTR-MS). Fluxes of these compounds from the canopy into the atmosphere were estimated from PTR-MS measurements by using an inverse Lagrangian transport model. Measurements were carried out continuously from September 2010 to January 2011,more » encompassing the dry and wet seasons. Mixing ratios were higher during the dry (isoprene – 2.68 ± 0.9 ppbv, total monoterpenes – 0.67 ± 0.3 ppbv; total sesquiterpenes – 0.09 ± 0.07 ppbv) than the wet season (isoprene – 1.66 ± 0.9 ppbv, total monoterpenes – 0.47 ± 0.2 ppbv; total sesquiterpenes – 0.03 ± 0.02 ppbv) for all compounds. Ambient air temperature and photosynthetically active radiation (PAR) behaved similarly. Daytime isoprene and total monoterpene mixing ratios were highest within the canopy, rather than near the ground or above the canopy. By comparison, daytime total sesquiterpene mixing ratios were highest near the ground. Daytime fluxes varied significantly between seasons for all compounds. The maximums for isoprene (2.53 ± 0.5 µmol m -2 h -1) and total monoterpenes (1.77 ± 0.05 µmol m -2 h -1) were observed in the late dry season, whereas the maximum for total sesquiterpenes was found during the dry-to-wet transition season (0.77 ± 0.1 µmol m -2 h -1). These flux estimates suggest that the canopy is the main source of isoprenoids emitted into the atmosphere for all seasons. However, uncertainties in turbulence parameterization near the ground could affect estimates of fluxes that come from the ground. Leaf phenology seemed to be an important driver of seasonal variation of isoprenoid emissions. Although remote sensing observations of changes in leaf area index were used to estimate leaf phenology, MEGAN 2.1 did not fully capture the behavior of seasonal emissions observed in this study. This could be a result of very local effects on the observed emissions, but also suggest that other parameters need to be better determined in biogenic volatile organic compound (BVOC) models. Our results support established findings that seasonality of isoprenoids are driven by seasonal changes in light, temperature and leaf phenology. However, they suggest that leaf phenology and its role on isoprenoid production and emission from tropical plant species needs to be better understood in order to develop mechanistic explanations for seasonal variation in emissions. This also may reduce the uncertainties of model estimates associated with the responses to environmental factors. Therefore, this study strongly encourages long-term measurements of isoprenoid emissions, environmental factors and leaf phenology from leaf to ecosystem scale, with the purpose of improving BVOC model approaches that can characterize seasonality of isoprenoid emissions from tropical rainforests.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alves, Eliane G.; Jardine, Kolby; Tota, Julio

Tropical rainforests are an important source of isoprenoid and other volatile organic compound (VOC) emissions to the atmosphere. The seasonal variation of these compounds is however still poorly understood. In this study, vertical profiles of mixing ratios of isoprene, total monoterpenes and total sesquiterpenes, were measured within and above the canopy, in a primary rainforest in central Amazonia, using a proton transfer reaction – mass spectrometer (PTR-MS). Fluxes of these compounds from the canopy into the atmosphere were estimated from PTR-MS measurements by using an inverse Lagrangian transport model. Measurements were carried out continuously from September 2010 to January 2011,more » encompassing the dry and wet seasons. Mixing ratios were higher during the dry (isoprene – 2.68 ± 0.9 ppbv, total monoterpenes – 0.67 ± 0.3 ppbv; total sesquiterpenes – 0.09 ± 0.07 ppbv) than the wet season (isoprene – 1.66 ± 0.9 ppbv, total monoterpenes – 0.47 ± 0.2 ppbv; total sesquiterpenes – 0.03 ± 0.02 ppbv) for all compounds. Ambient air temperature and photosynthetically active radiation (PAR) behaved similarly. Daytime isoprene and total monoterpene mixing ratios were highest within the canopy, rather than near the ground or above the canopy. By comparison, daytime total sesquiterpene mixing ratios were highest near the ground. Daytime fluxes varied significantly between seasons for all compounds. The maximums for isoprene (2.53 ± 0.5 µmol m -2 h -1) and total monoterpenes (1.77 ± 0.05 µmol m -2 h -1) were observed in the late dry season, whereas the maximum for total sesquiterpenes was found during the dry-to-wet transition season (0.77 ± 0.1 µmol m -2 h -1). These flux estimates suggest that the canopy is the main source of isoprenoids emitted into the atmosphere for all seasons. However, uncertainties in turbulence parameterization near the ground could affect estimates of fluxes that come from the ground. Leaf phenology seemed to be an important driver of seasonal variation of isoprenoid emissions. Although remote sensing observations of changes in leaf area index were used to estimate leaf phenology, MEGAN 2.1 did not fully capture the behavior of seasonal emissions observed in this study. This could be a result of very local effects on the observed emissions, but also suggest that other parameters need to be better determined in biogenic volatile organic compound (BVOC) models. Our results support established findings that seasonality of isoprenoids are driven by seasonal changes in light, temperature and leaf phenology. However, they suggest that leaf phenology and its role on isoprenoid production and emission from tropical plant species needs to be better understood in order to develop mechanistic explanations for seasonal variation in emissions. This also may reduce the uncertainties of model estimates associated with the responses to environmental factors. Therefore, this study strongly encourages long-term measurements of isoprenoid emissions, environmental factors and leaf phenology from leaf to ecosystem scale, with the purpose of improving BVOC model approaches that can characterize seasonality of isoprenoid emissions from tropical rainforests.« less

Seasonality of isoprenoid emissions from a primary rainforest in central Amazonia

NASA Astrophysics Data System (ADS)

Alves, Eliane G.; Jardine, Kolby; Tota, Julio; Jardine, Angela; Yãnez-Serrano, Ana Maria; Karl, Thomas; Tavares, Julia; Nelson, Bruce; Gu, Dasa; Stavrakou, Trissevgeni; Martin, Scot; Artaxo, Paulo; Manzi, Antonio; Guenther, Alex

2016-03-01

Tropical rainforests are an important source of isoprenoid and other volatile organic compound (VOC) emissions to the atmosphere. The seasonal variation of these compounds is however still poorly understood. In this study, vertical profiles of mixing ratios of isoprene, total monoterpenes and total sesquiterpenes, were measured within and above the canopy, in a primary rainforest in central Amazonia, using a proton transfer reaction - mass spectrometer (PTR-MS). Fluxes of these compounds from the canopy into the atmosphere were estimated from PTR-MS measurements by using an inverse Lagrangian transport model. Measurements were carried out continuously from September 2010 to January 2011, encompassing the dry and wet seasons. Mixing ratios were higher during the dry (isoprene - 2.68 ± 0.9 ppbv, total monoterpenes - 0.67 ± 0.3 ppbv; total sesquiterpenes - 0.09 ± 0.07 ppbv) than the wet season (isoprene - 1.66 ± 0.9 ppbv, total monoterpenes - 0.47 ± 0.2 ppbv; total sesquiterpenes - 0.03 ± 0.02 ppbv) for all compounds. Ambient air temperature and photosynthetically active radiation (PAR) behaved similarly. Daytime isoprene and total monoterpene mixing ratios were highest within the canopy, rather than near the ground or above the canopy. By comparison, daytime total sesquiterpene mixing ratios were highest near the ground. Daytime fluxes varied significantly between seasons for all compounds. The maximums for isoprene (2.53 ± 0.5 µmol m-2 h-1) and total monoterpenes (1.77 ± 0.05 µmol m-2 h-1) were observed in the late dry season, whereas the maximum for total sesquiterpenes was found during the dry-to-wet transition season (0.77 ± 0.1 µmol m-2 h-1). These flux estimates suggest that the canopy is the main source of isoprenoids emitted into the atmosphere for all seasons. However, uncertainties in turbulence parameterization near the ground could affect estimates of fluxes that come from the ground. Leaf phenology seemed to be an important driver of seasonal variation of isoprenoid emissions. Although remote sensing observations of changes in leaf area index were used to estimate leaf phenology, MEGAN 2.1 did not fully capture the behavior of seasonal emissions observed in this study. This could be a result of very local effects on the observed emissions, but also suggest that other parameters need to be better determined in biogenic volatile organic compound (BVOC) models. Our results support established findings that seasonality of isoprenoids are driven by seasonal changes in light, temperature and leaf phenology. However, they suggest that leaf phenology and its role on isoprenoid production and emission from tropical plant species needs to be better understood in order to develop mechanistic explanations for seasonal variation in emissions. This also may reduce the uncertainties of model estimates associated with the responses to environmental factors. Therefore, this study strongly encourages long-term measurements of isoprenoid emissions, environmental factors and leaf phenology from leaf to ecosystem scale, with the purpose of improving BVOC model approaches that can characterize seasonality of isoprenoid emissions from tropical rainforests.

Seasonality of isoprenoid emissions from a primary rainforest in central Amazonia

NASA Astrophysics Data System (ADS)

Alves, E. G.; Jardine, K.; Tota, J.; Jardine, A.; Yáñez-Serrano, A. M.; Karl, T.; Tavares, J.; Nelson, B.; Gu, D.; Stavrakou, T.; Martin, S.; Manzi, A.; Guenther, A.

2015-10-01

Tropical rainforests are an important source of isoprenoid and other Volatile Organic Compound (VOC) emissions to the atmosphere. The seasonal variation of these compounds is however still poorly understood. In this study, profiles were collected of the vertical profile of mixing ratios of isoprene, total monoterpenes and total sesquiterpenes, within and above the canopy, in a primary rainforest in central Amazonia, using a Proton Transfer Reaction-Mass Spectrometer (PTR-MS). Fluxes of these compounds from the canopy into the atmosphere were estimated from PTR-MS measurements by using an inverse Lagrangian transport model. Measurements were carried out continuously from September 2010 to January 2011, encompassing the dry and wet seasons. Mixing ratios were higher during the dry (isoprene - 2.68 ± 0.9 ppbv, total monoterpenes - 0.67 ± 0.3 ppbv; total sesquiterpenes - 0.09 ± 0.07 ppbv) than the wet season (isoprene - 1.66 ± 0.9 ppbv, total monoterpenes - 0.47 ± 0.2 ppbv; total sesquiterpenes - 0.03 ± 0.02 ppbv) for all compounds. Ambient air temperature and photosynthetically active radiation (PAR) behaved similarly. Daytime isoprene and total monoterpene mixing ratios were highest within the canopy, rather than near the ground or above the canopy. By comparison, daytime total sesquiterpene mixing ratios were highest near the ground. Daytime fluxes varied significantly between seasons for all compounds. The maximums for isoprene (2.53 ± 0.5 μmol m-2 h-1) and total monoterpenes (1.77 ± 0.05 μmol m-2 h-1) were observed in the late dry season, whereas the maximum for total sesquiterpenes was found during the dry-to-wet transition season (0.77 ± 0.1 μmol m-2 h-1). These flux estimates suggest that the canopy is the main source of isoprenoids to the atmosphere for all seasons. However, uncertainties in turbulence parameterization near the ground could affect estimates of fluxes that come from the ground. Leaf phenology seemed to be an important driver of seasonal variation of isoprenoid emissions. Although remote sensing observations of changes in leaf area index were used to estimate leaf phenology, MEGAN 2.1 did not fully capture the behavior of seasonal emissions observed in this study. This could be a result of very local effects on the observed emissions, but also suggest that other parameters need to be better determined in Biogenic Volatile Organic Compound (BVOC) models. Our results support established findings that seasonality of isoprenoids are driven by seasonal changes in light, temperature and leaf phenology. However, they suggest that leaf phenology and its role on isoprenoid production and emission from tropical plant species needs to be better understood in order to develop mechanistic explanations for seasonal variation in emissions. This also may reduce the uncertainties of model estimates associated with the responses to environmental factors. Therefore, this study strongly encourages long-term measurements of isoprenoid emissions, environmental factors and leaf phenology from leaf to ecosystem scale, with the purpose of improving BVOC model approaches that can characterize seasonality of isoprenoid emissions from tropical rainforests.

The Thermal Infrared Sensor on the Landsat Data Continutiy Mission

USDA-ARS?s Scientific Manuscript database

The REGularized canopy reFLECtance (REGFLEC) modeling tool integrates leaf optics, canopy reflectance, and atmospheric radiative transfer model components, facilitating accurate retrieval of leaf area index (LAI) and leaf chlorophyll content (Cab) directly from at-sensor radiances in green, red and ...

Impact of anatomical traits of maize (Zea mays L.) leaf as affected by nitrogen supply and leaf age on bundle sheath conductance.

PubMed

Retta, Moges; Yin, Xinyou; van der Putten, Peter E L; Cantre, Denis; Berghuijs, Herman N C; Ho, Quang Tri; Verboven, Pieter; Struik, Paul C; Nicolaï, Bart M

2016-11-01

The mechanism of photosynthesis in C 4 crops depends on the archetypal Kranz-anatomy. To examine how the leaf anatomy, as altered by nitrogen supply and leaf age, affects the bundle sheath conductance (g bs ), maize (Zea mays L.) plants were grown under three contrasting nitrogen levels. Combined gas exchange and chlorophyll fluorescence measurements were done on fully grown leaves at two leaf ages. The measured data were analysed using a biochemical model of C 4 photosynthesis to estimate g bs . The leaf microstructure and ultrastructure were quantified using images obtained from micro-computed tomography and microscopy. There was a strong positive correlation between g bs and leaf nitrogen content (LNC) while old leaves had lower g bs than young leaves. Leaf thickness, bundle sheath cell wall thickness and surface area of bundle sheath cells per unit leaf area (S b ) correlated well with g bs although they were not significantly affected by LNC. As a result, the increase of g bs with LNC was little explained by the alteration of leaf anatomy. In contrast, the combined effect of LNC and leaf age on S b was responsible for differences in g bs between young leaves and old leaves. Future investigations should consider changes at the level of plasmodesmata and membranes along the CO 2 leakage pathway to unravel LNC and age effects further. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Modeling canopy-level productivity: is the "big-leaf" simplification acceptable?

NASA Astrophysics Data System (ADS)

Sprintsin, M.; Chen, J. M.

2009-05-01

The "big-leaf" approach to calculating the carbon balance of plant canopies assumes that canopy carbon fluxes have the same relative responses to the environment as any single unshaded leaf in the upper canopy. Widely used light use efficiency models are essentially simplified versions of the big-leaf model. Despite its wide acceptance, subsequent developments in the modeling of leaf photosynthesis and measurements of canopy physiology have brought into question the assumptions behind this approach showing that big leaf approximation is inadequate for simulating canopy photosynthesis because of the additional leaf internal control on carbon assimilation and because of the non-linear response of photosynthesis on leaf nitrogen and absorbed light, and changes in leaf microenvironment with canopy depth. To avoid this problem a sunlit/shaded leaf separation approach, within which the vegetation is treated as two big leaves under different illumination conditions, is gradually replacing the "big-leaf" strategy, for applications at local and regional scales. Such separation is now widely accepted as a more accurate and physiologically based approach for modeling canopy photosynthesis. Here we compare both strategies for Gross Primary Production (GPP) modeling using the Boreal Ecosystem Productivity Simulator (BEPS) at local (tower footprint) scale for different land cover types spread over North America: two broadleaf forests (Harvard, Massachusetts and Missouri Ozark, Missouri); two coniferous forests (Howland, Maine and Old Black Spruce, Saskatchewan); Lost Creek shrubland site (Wisconsin) and Mer Bleue petland (Ontario). BEPS calculates carbon fixation by scaling Farquhar's leaf biochemical model up to canopy level with stomatal conductance estimated by a modified version of the Ball-Woodrow-Berry model. The "big-leaf" approach was parameterized using derived leaf level parameters scaled up to canopy level by means of Leaf Area Index. The influence of sunlit/shaded leaf separation on GPP prediction was evaluated accounting for the degree of the deviation of 3-dimensional leaf spatial distribution from the random case. More specifically, we compared and evaluated the behavior of both models showing the advantages of sunlit/shaded leaf separation strategy over a simplified big-leaf approach. Keywords: canopy photosynthesis, leaf area index, clumping index, remote sensing.

New dimension analyses with error analysis for quaking aspen and black spruce

NASA Technical Reports Server (NTRS)

Woods, K. D.; Botkin, D. B.; Feiveson, A. H.

1987-01-01

Dimension analysis for black spruce in wetland stands and trembling aspen are reported, including new approaches in error analysis. Biomass estimates for sacrificed trees have standard errors of 1 to 3%; standard errors for leaf areas are 10 to 20%. Bole biomass estimation accounts for most of the error for biomass, while estimation of branch characteristics and area/weight ratios accounts for the leaf area error. Error analysis provides insight for cost effective design of future analyses. Predictive equations for biomass and leaf area, with empirically derived estimators of prediction error, are given. Systematic prediction errors for small aspen trees and for leaf area of spruce from different site-types suggest a need for different predictive models within species. Predictive equations are compared with published equations; significant differences may be due to species responses to regional or site differences. Proportional contributions of component biomass in aspen change in ways related to tree size and stand development. Spruce maintains comparatively constant proportions with size, but shows changes corresponding to site. This suggests greater morphological plasticity of aspen and significance for spruce of nutrient conditions.

Losses of leaf area owing to herbivory and early senescence in three tree species along a winter temperature gradient

NASA Astrophysics Data System (ADS)

González-Zurdo, P.; Escudero, A.; Nuñez, R.; Mediavilla, S.

2016-11-01

In temperate climates, evergreen leaves have to survive throughout low temperature winter periods. Freezing and chilling injuries can lead to accelerated senescence of part of the leaf surface, which contributes to a reduction of the lifespan of the photosynthetic machinery and of leaf lifetime carbon gain. Low temperatures are also associated with changes in foliar chemistry and morphology that affect consumption by herbivores. Therefore, the severity of foliar area losses caused by accelerated senescence and herbivory can change along winter temperature gradients. The aim of this study is to analyse such responses in the leaves of three evergreen species ( Quercus ilex, Q. suber and Pinus pinaster) along a climatic gradient. The leaves of all three species presented increased leaf mass per area (LMA) and higher concentrations of structural carbohydrates in cooler areas. Only the two oak species showed visible symptoms of damage caused by herbivory, this being less intense at the coldest sites. The leaves of all three species presented chlorotic and necrotic spots that increased in size with leaf age. The foliar surface affected by chlorosis and necrosis was larger at the sites with the coldest winters. Therefore, the effects of the winter cold on the lifespan of the photosynthetic machinery were contradictory: losses of leaf area due to accelerated senescence increased, but there was a decrease in losses caused by herbivory. The final consequences for carbon assimilation strongly depend on the exact timing of the appearance of the damage resulting from low temperature and grazing by herbivores.

Influence of sewage sludge, as a substrate, in the plasticity of functional characteristics of plants.

PubMed

da Silva, Vicente Elício Porfiro Sales Gonçalves; Buarque, Patrícia Marques Carneiro; Ferreira, Wanessa Nepomuceno; Buarque, Hugo Leonardo de Brito; Silva, Maria Amanda Menezes

2018-04-24

This work aimed to evaluate the effect of sewage sludge application as fertilizer on the plasticity of functional characteristics of species commonly found in the Caatinga. The research was developed in the nursery of the Federal Institute of Education, Science and Technology of Ceará (IFCE), Quixadá campus, located in northeastern Brazil. Three treatments were applied: raw sludge, sanitized sludge, and no manipulation. In each treatment, five species were planted, each with five individuals, totaling 75 individuals, which were tagged, and 4 months after germination, they were destroyed to obtain dry matter content (TMSF) from leaf, stem (TMSC), fine root (TMSRF), and thick root (TMSRG); leaf area; height and diameter of the seedling; and length above and below the ground. The sanitized sludge was responsible for giving higher values for leaf area, height of the seedlings, and diameter and length of stem and root. However, the dry matter content of the fine roots was higher in the treatment without manipulation. At the community level, as TMSRG increased, TMSC also increased, the same occurred between TMSRG and TMSRF, TMSC and TMSRF, and stem length and leaf area. In the treatment without manipulation, there was a positive correlation between leaf area, height and plant diameter, and negative correlation between root length and plant diameter. Thus, it can be concluded that the use of sanitized sludge is a good tool to increase the availability of soil resources, conferring to individuals' greater dry matter content, greater leaf area, and higher height and diameter above the ground.

The narrow-leaf syndrome: a functional and evolutionary approach to the form of fog-harvesting rosette plants.

PubMed

Martorell, Carlos; Ezcurra, Exequiel

2007-04-01

Plants that use fog as an important water-source frequently have a rosette growth habit. The performance of this morphology in relation to fog interception has not been studied. Some first-principles from physics predict that narrow leaves, together with other ancillary traits (large number and high flexibility of leaves, caudices, and/or epiphytism) which constitute the "narrow-leaf syndrome" should increase fog-interception efficiency. This was tested using aluminum models of rosettes that differed in leaf length, width and number and were exposed to artificial fog. The results were validated using seven species of Tillandsia and four species of xerophytic rosettes. The total amount of fog intercepted in rosette plants increased with total leaf area, while narrow leaves maximized interception efficiency (measured as interception per unit area). The number of leaves in the rosettes is physically constrained because wide-leafed plants can only have a few blades. At the limits of this constraint, net fog interception was independent of leaf form, but interception efficiency was maximized by large numbers of narrow leaves. Atmospheric Tillandsia species show the narrow-leaf syndrome. Their fog interception efficiencies were correlated to the ones predicted from aluminum-model data. In the larger xerophytic rosette species, the interception efficiency was greatest in plants showing the narrow-leaf syndrome. The adaptation to fog-harvesting in several narrow-leaved rosettes was tested for evolutionary convergence in 30 xerophytic rosette species using a comparative method. There was a significant evolutionary tendency towards the development of the narrow-leaf syndrome the closer the species grew to areas where fog is frequently available. This study establishes convergence in a very wide group of plants encompassing genera as contrasting as Tillandsia and Agave as a result of their dependence on fog.

Zinc deficiency in field-grown pecan trees: changes in leaf nutrient concentrations and structure.

PubMed

Ojeda-Barrios, Dámaris; Abadía, Javier; Lombardini, Leonardo; Abadía, Anunciación; Vázquez, Saúl

2012-06-01

Zinc (Zn) deficiency is a typical nutritional disorder in pecan trees [Carya illinoinensis (Wangenh.) C. Koch] grown under field conditions in calcareous soils in North America, including northern Mexico and south-western United States. The aim of this study was to assess the morphological and nutritional changes in pecan leaves affected by Zn deficiency as well as the Zn distribution within leaves. Zinc deficiency led to decreases in leaf chlorophyll concentrations, leaf area and trunk cross-sectional area. Zinc deficiency increased significantly the leaf concentrations of K and Ca, and decreased the leaf concentrations of Zn, Fe, Mn and Cu. All nutrient values found in Zn-deficient leaves were within the sufficiency ranges, with the only exception of Zn, which was approximately 44, 11 and 9 µg g(-1) dry weight in Zn-sufficient, moderately and markedly Zn-deficient leaves, respectively. Zinc deficiency led to decreases in leaf thickness, mainly due to a reduction in the thickness of the palisade parenchyma, as well as to increases in stomatal density and size. The localisation of Zn was determined using the fluorophore Zinpyr-1 and ratio-imaging technique. Zinc was mainly localised in the palisade mesophyll area in Zn-sufficient leaves, whereas no signal could be obtained in Zn-deficient leaves. The effects of Zn deficiency on the leaf characteristics of pecan trees include not only decreases in leaf chlorophyll and Zn concentrations, but also a reduction in the thickness of the palisade parenchyma, an increase in stomatal density and pore size and the practical disappearance of Zn leaf pools. These characteristics must be taken into account to design strategies to correct Zn deficiency in pecan tree in the field. Copyright © 2012 Society of Chemical Industry.

Long-term impact of Ophiostoma novo-ulmi on leaf traits and transpiration of branches in the Dutch elm hybrid 'Dodoens'.

PubMed

Plichta, Roman; Urban, Josef; Gebauer, Roman; Dvořák, Miloň; Ďurkovič, Jaroslav

2016-03-01

To better understand the long-term impact of Ophiostoma novo-ulmi Brasier on leaf physiology in 'Dodoens', a Dutch elm disease-tolerant hybrid, measurements of leaf area, leaf dry mass, petiole anatomy, petiole hydraulic conductivity, leaf and branch water potential, and branch sap flow were performed 3 years following an initial artificial inoculation. Although fungal hyphae were detected in fully expanded leaves, neither anatomical nor morphological traits were affected, indicating that there was no impact from the fungal hyphae on the leaves during leaf expansion. In contrast, however, infected trees showed both a lower transpiration rate of branches and a lower sap flow density. The long-term persistence of fungal hyphae inside vessels decreased the xylem hydraulic conductivity, but stomatal regulation of transpiration appeared to be unaffected as the leaf water potential in both infected and non-infected trees was similarly driven by the transpirational demands. Regardless of the fungal infection, leaves with a higher leaf mass per area ratio tended to have a higher leaf area-specific conductivity. Smaller leaves had an increased number of conduits with smaller diameters and thicker cell walls. Such a pattern could increase tolerance towards hydraulic dysfunction. Measurements of water potential and theoretical xylem conductivity revealed that petiole anatomy could predict the maximal transpiration rate. Three years following fungal inoculation, phenotypic expressions for the majority of the examined traits revealed a constitutive nature for their possible role in Dutch elm disease tolerance of 'Dodoens' trees. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Ecophysiological responses of a young blue gum (Eucalyptus globulus) plantation to weed control.

PubMed

Eyles, Alieta; Worledge, Dale; Sands, Peter; Ottenschlaeger, Maria L; Paterson, Steve C; Mendham, Daniel; O'Grady, Anthony P

2012-08-01

Early weed control may improve the growth of forest plantations by influencing soil water and nutrient availability. To understand eucalypt growth responses to weed control, we examined the temporal responses of leaf gas-exchange, leaf nitrogen concentration (N) and water status of 7-month-old Eucalyptus globulus L. trees in a paired-plot field trial. In addition, we monitored the growth, leaf N and water status of the competing vegetation in the weed treatment. By the end of the 11-month experiment, complete weed control (WF treatment) of largely woody competitors increased the basal diameter of E. globulus by 14%. As indicated by pre-dawn water potentials of > - 0.05 MPa, interspecies competition for water resources was minimal at this site. In contrast, competition for N appeared to be the major factor limiting growth. Estimations of total plot leaf N (g m(-2) ground) showed that competing vegetation accounted for up to 70% of the total leaf N at the start of the trial. This value fell to 15% by the end of the trial. Despite increased leaf N(area) in WF trees 5 months after imposition of weed control, the photosynthetic capacity (A(1500)) of E. globulus was unaffected by treatment suggesting that the growth gains from weed control were largely unrelated to changes in leaf-level photosynthesis. Increased nutrient availability brought about by weed control enabled trees to increase investment into leaf-area production. Estimates of whole-tree carbon budget based on direct measurements of dark respiration and A(1500) allowed us to clearly demonstrate the importance of leaf area driving greater productivity following early weed control in a nutrient-limited site.

Tibiofemoral Contact Mechanics with Horizontal Cleavage Tear and Resection of the Medial Meniscus in the Human Knee.

PubMed

Koh, Jason L; Yi, Seung Jin; Ren, Yupeng; Zimmerman, Todd A; Zhang, Li-Qun

2016-11-02

The meniscus is known to increase the contact area and decrease contact pressure in the tibiofemoral compartments of the knee. Radial tears of the meniscal root attachment along with partial resections of the torn meniscal tissue decrease the contact area and increase pressure; however, there is a lack of information on the effects of a horizontal cleavage tear (HCT) and partial leaf meniscectomy of such tears on tibiofemoral contact pressure and contact area. Twelve fresh-frozen human cadaveric knees were tested under 10 conditions: 5 serial conditions of posterior medial meniscectomy (intact meniscus, HCT, repaired HCT, inferior leaf resection, and resection of both inferior and superior leaves), each at 2 knee flexion angles (0° and 60°) under an 800-N axial load. Tekscan sensors (model 4000) were used to measure the contact pressure and contact area. HCT and HCT repair resulted in small changes in the contact area and an increase in contact pressure compared with the intact condition. Resection of the inferior leaf resulted in significantly decreased contact area (to a mean 82.3% of the intact condition at 0° of flexion and 81.8% at 60° of flexion; p < 0.05) and increased peak contact pressure (a mean 36.3% increase at 0° flexion and 43.2% increase at 60° flexion; p < 0.05) in the medial compartment. Further resection of the remaining superior leaf resulted in additional significant decreases in contact area (to a mean 60.1% of the intact condition at 0° of flexion and 49.7% at 60° of flexion; p < 0.05) and increases in peak contact pressure (a mean 79.2% increase at 0° of flexion and 74.9% increase at 60° of flexion; p < 0.05). Resection of meniscal tissue forming the inferior leaf of an HCT resulted in substantially decreased contact area and increased contact pressure. Additional resection of the superior leaf resulted in a further significant decrease in contact area and increase in contact pressure in the medial compartment. Repair or minimal resection of meniscal tissue of an HCT may be preferred to complete leaf resection to maintain knee tibiofemoral contact mechanics. Copyright © 2016 by The Journal of Bone and Joint Surgery, Incorporated.

Leaf Pressure Volume Data in Caxiuana and Tapajos National Forest, Para, Brazil (2011)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Powell, Thomas; Moorcroft, Paul

Pressure volume curve measurements on leaves of canopy trees from the from the Caxiuana and Tapajos National Forests, Para, Brazil. Tapajos samples were harvested from the km 67 forested area, which is adjacent to the decommissioned throughfall exclusion drought experimental plot. Caxiuana samples were harvested from trees growing in the throughfall exclusion plots. Data were collected in 2011. Dataset includes: date of measurement, site ID, plot ID, tree ID (species, tree tag #), leaf area, fresh weight, relative weight, leaf water potential, and leaf water loss. P-V curve parameters (turgor loss point, osmotic potential, and bulk modulus of elasticity) canmore » be found in Powell et al. (2017) Differences in xylem cavitation resistance and leaf hydraulic traits explain differences in drought tolerance among mature Amazon rainforest trees. Global Change Biology.« less

Production, partial purification and characterization of xylanase using Nicotiana tabacum leaf dust as substrate.

PubMed

Acharya, Komal P; Shilpkar, Prateek

2016-03-01

Isolated Bacillus sp. was used in the present study for production of xylanase from Nicotiana tabacum leaf dust. The strain was able to give a maximum of 1.77 Uml⁻¹ xylanase activity under optimized fermentation conditions which was further increased upto 2.77 Uml⁻¹ after extraction and partial purification of enzyme. After partial purification, the enzyme was characterized and it gave the highest xylanase activity at pH 7.0, when 0.2 ml enzyme was incubated with 2.0% substrate (Nicotiana tabacum leaf dust) for 60 min at 60°C. Saccharification study of Nicotiana tabacum leaf dust with partially purified enzyme revealed that 18.4% reducing sugar was released in 20 hrs incubation, and TLC and HPTLC analysis showed that xylose and glucose sugars were obtained after hydrolysis of substrate. FTIR analysis confirmed decomposition of substrate.

Leaf turnover and growth responses of shade-grown saplings of four Shorea rain forest species to a sudden increase in light.

PubMed

Shimizu, Michiru; Ishida, Atsushi; Tange, Takeshi; Yagi, Hisayoshi

2006-04-01

We tested the hypothesis that sapling growth following a sudden increase in solar irradiance is related to recovery from photoinhibition and the balance between rate of production of new leaves and rate of abscision of old leaves. Leaf gas exchange, chlorophyll fluorescence and relative growth rate (RGR) of stem basal area were measured following the sudden exposure of shade-grown (7% of full sunlight) saplings of four Shorea species to full sunlight. Sudden exposure to full sunlight resulted in an immediate and substantial reduction in dark-adapted quantum yield of photosystem II (Fv/Fm), followed by a gradual recovery in all species. Near light-saturated net assimilation rate (A max) and area-based leaf chlorophyll concentration ([Chl area]) also declined immediately after exposure. Eleven days after exposure, A max had recovered to pre-exposure values in all species, whereas [Chl area] had not recovered. Across species, RGR of stem basal area increased with increasing RGR of the number of leaves following exposure to full sunlight. The interspecific variations in RGR of stem basal area suggest that new leaf production is crucial for determining the potential growth of saplings following gap formation.

Fog interception by Sequoia sempervirens (D. Don) crowns decouples physiology from soil water deficit.

PubMed

Simonin, Kevin A; Santiago, Louis S; Dawson, Todd E

2009-07-01

Although crown wetting events can increase plant water status, leaf wetting is thought to negatively affect plant carbon balance by depressing photosynthesis and growth. We investigated the influence of crown fog interception on the water and carbon relations of juvenile and mature Sequoia sempervirens trees. Field observations of mature trees indicated that fog interception increased leaf water potential above that of leaves sheltered from fog. Furthermore, observed increases in leaf water potential exceeded the maximum water potential predicted if soil water was the only available water source. Because field observations were limited to two mature trees, we conducted a greenhouse experiment to investigate how fog interception influences plant water status and photosynthesis. Pre-dawn and midday branchlet water potential, leaf gas exchange and chlorophyll fluorescence were measured on S. sempervirens saplings exposed to increasing soil water deficit, with and without overnight canopy fog interception. Sapling fog interception increased leaf water potential and photosynthesis above the control and soil water deficit treatments despite similar dark-acclimated leaf chlorophyll fluorescence. The field observations and greenhouse experiment show that fog interception represents an overlooked flux into the soil-plant-atmosphere continuum that temporarily, but significantly, decouples leaf-level water and carbon relations from soil water availability.

Fatigue Life Assessment of 65Si7 Leaf Springs: A Comparative Study

PubMed Central

Arora, Vinkel Kumar; Bhushan, Gian; Aggarwal, M. L.

2014-01-01

The experimental fatigue life prediction of leaf springs is a time consuming process. The engineers working in the field of leaf springs always face a challenge to formulate alternate methods of fatigue life assessment. The work presented in this paper provides alternate methods for fatigue life assessment of leaf springs. A 65Si7 light commercial vehicle leaf spring is chosen for this study. The experimental fatigue life and load rate are determined on a full scale leaf spring testing machine. Four alternate methods of fatigue life assessment have been depicted. Firstly by SAE spring design manual approach the fatigue test stroke is established and by the intersection of maximum and initial stress the fatigue life is predicted. The second method constitutes a graphical method based on modified Goodman's criteria. In the third method codes are written in FORTRAN for fatigue life assessment based on analytical technique. The fourth method consists of computer aided engineering tools. The CAD model of the leaf spring has been prepared in solid works and analyzed using ANSYS. Using CAE tools, ideal type of contact and meshing elements have been proposed. The method which provides fatigue life closer to experimental value and consumes less time is suggested. PMID:27379327

Fabrication of Artificial Leaf to Develop Fluid Pump Driven by Surface Tension and Evaporation

NASA Astrophysics Data System (ADS)

Lee, Minki; Lim, Hosub; Lee, Jinkee

2017-11-01

Plants transport water from roots to leaves via xylem through transpiration, which is an evaporation process that occurs at the leaves. During transpiration, negative pressure can be generated by the porous structure of mesophyll cells in the leaves. Here, an artificial leaf mimicking structure using hydrogel, which has a nanoporous structure is fabricated. The cryogel method is used to develop a hierarchy structure on the nano- and microscale in the hydrogel media that is similar to the mesophyll cells and veins of a leaf, respectively. The theoretical model is analyzed to calculate the flow resistance in the artificial leaf, and compare the model with the experimental results. The experiment involves connecting a glass capillary tube at the bottom of the artificial leaf to observe the fluid velocity in the glass capillary tube generated by the negative pressure. The use of silicone oil as fluid instead of water to increase the flow resistance enables the measurement of negative pressure. The negative pressure of the artificial leaf is affected by several variables (e.g., pore size, wettability of the structure). Finally, by decreasing the pore size and increasing the wettability, the maximum negative pressure of the artificial leaf, -7.9 kPa is obtained.