Identification and characterization of genomic regions on chromosomes 4 and 8 that control the rate of photosynthesis in rice leaves

PubMed Central

Adachi, Shunsuke; Tsuru, Yukiko; Nito, Naoko; Murata, Kazumasa; Yamamoto, Toshio; Ebitani, Takeshi; Ookawa, Taiichiro; Hirasawa, Tadashi

2011-01-01

DNA marker-assisted selection appears to be a promising strategy for improving rates of leaf photosynthesis in rice. The rate of leaf photosynthesis was significantly higher in a high-yielding indica variety, Habataki, than in the most popular Japanese variety, Koshihikari, at the full heading stage as a result of the higher level of leaf nitrogen at the same rate of application of nitrogen and the higher stomatal conductance even when the respective levels of leaf nitrogen were the same. The higher leaf nitrogen content of Habataki was caused by the greater accumulation of nitrogen by plants. The higher stomatal conductance of Habataki was caused by the higher hydraulic conductance. Using progeny populations and selected lines derived from a cross between Koshihikari and Habataki, it was possible to identify the genomic regions responsible for the rate of photosynthesis within a 2.1 Mb region between RM17459 and RM17552 and within a 1.2 Mb region between RM6999 and RM22529 on the long arm of chromosome 4 and on the short arm of chromosome 8, respectively. The designated region on chromosome 4 of Habataki was responsible for both the increase in the nitrogen content of leaves and hydraulic conductance in the plant by increasing the root surface area. The designated region on chromosome 8 of Habataki was responsible for the increase in hydraulic conductance by increasing the root hydraulic conductivity. The results suggest that it may be possible to improve photosynthesis in rice leaves by marker-assisted selection that focuses on these regions of chromosomes 4 and 8. PMID:21296764

Trade-offs between seed and leaf size (seed-phytomer-leaf theory): functional glue linking regenerative with life history strategies … and taxonomy with ecology?

PubMed

Hodgson, John G; Santini, Bianca A; Montserrat Marti, Gabriel; Royo Pla, Ferran; Jones, Glynis; Bogaard, Amy; Charles, Mike; Font, Xavier; Ater, Mohammed; Taleb, Abdelkader; Poschlod, Peter; Hmimsa, Younes; Palmer, Carol; Wilson, Peter J; Band, Stuart R; Styring, Amy; Diffey, Charlotte; Green, Laura; Nitsch, Erika; Stroud, Elizabeth; Romo-Díez, Angel; de Torres Espuny, Lluis; Warham, Gemma

2017-11-10

While the 'worldwide leaf economics spectrum' (Wright IJ, Reich PB, Westoby M, et al. 2004. The worldwide leaf economics spectrum. Nature : 821-827) defines mineral nutrient relationships in plants, no unifying functional consensus links size attributes. Here, the focus is upon leaf size, a much-studied plant trait that scales positively with habitat quality and components of plant size. The objective is to show that this wide range of relationships is explicable in terms of a seed-phytomer-leaf (SPL) theoretical model defining leaf size in terms of trade-offs involving the size, growth rate and number of the building blocks (phytomers) of which the young shoot is constructed. Functional data for 2400+ species and English and Spanish vegetation surveys were used to explore interrelationships between leaf area, leaf width, canopy height, seed mass and leaf dry matter content (LDMC). Leaf area was a consistent function of canopy height, LDMC and seed mass. Additionally, size traits are partially uncoupled. First, broad laminas help confer competitive exclusion while morphologically large leaves can, through dissection, be functionally small. Secondly, leaf size scales positively with plant size but many of the largest-leaved species are of medium height with basally supported leaves. Thirdly, photosynthetic stems may represent a functionally viable alternative to 'small seeds + large leaves' in disturbed, fertile habitats and 'large seeds + small leaves' in infertile ones. Although key elements defining the juvenile growth phase remain unmeasured, our results broadly support SPL theory in that phytometer and leaf size are a product of the size of the initial shoot meristem (≅ seed mass) and the duration and quality of juvenile growth. These allometrically constrained traits combine to confer ecological specialization on individual species. Equally, they appear conservatively expressed within major taxa. Thus, 'evolutionary canalization' sensu Stebbins (Stebbins GL. 1974. Flowering plants: evolution above the species level . Cambridge, MA: Belknap Press) is perhaps associated with both seed and leaf development, and major taxa appear routinely specialized with respect to ecologically important size-related traits. © The Author 2017. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For Permissions, please email: journals.permissions@oup.com

[Suitability of four stomatal conductance models in agro-pastoral ecotone in North China: A case study for potato and oil sunflower.

PubMed

Huang, Ming Xia; Wang, Jing; Tang, Jian Zhao; Yu, Qiang; Zhang, Jun; Xue, Qing Yu; Chang, Qing; Tan, Mei Xiu

2016-11-18

The suitability of four popular empirical and semi-empirical stomatal conductance models (Jarvis model, Ball-Berry model, Leuning model and Medlyn model) was evaluated based on para-llel observation data of leaf stomatal conductance, leaf net photosynthetic rate and meteorological factors during the vigorous growing period of potato and oil sunflower at Wuchuan experimental station in agro-pastoral ecotone in North China. It was found that there was a significant linear relationship between leaf stomatal conductance and leaf net photosynthetic rate for potato, whereas the linear relationship appeared weaker for oil sunflower. The results of model evaluation showed that Ball-Berry model performed best in simulating leaf stomatal conductance of potato, followed by Leuning model and Medlyn model, while Jarvis model was the last in the performance rating. The root-mean-square error (RMSE) was 0.0331, 0.0371, 0.0456 and 0.0794 mol·m -2 ·s -1 , the normalized root-mean-square error (NRMSE) was 26.8%, 30.0%, 36.9% and 64.3%, and R-squared (R 2 ) was 0.96, 0.61, 0.91 and 0.88 between simulated and observed leaf stomatal conductance of potato for Ball-Berry model, Leuning model, Medlyn model and Jarvis model, respectively. For leaf stomatal conductance of oil sunflower, Jarvis model performed slightly better than Leuning model, Ball-Berry model and Medlyn model. RMSE was 0.2221, 0.2534, 0.2547 and 0.2758 mol·m -2 ·s -1 , NRMSE was 40.3%, 46.0%, 46.2% and 50.1%, and R 2 was 0.38, 0.22, 0.23 and 0.20 between simulated and observed leaf stomatal conductance of oil sunflower for Jarvis model, Leuning model, Ball-Berry model and Medlyn model, respectively. The path analysis was conducted to identify effects of specific meteorological factors on leaf stomatal conductance. The diurnal variation of leaf stomatal conductance was principally affected by vapour pressure saturation deficit for both potato and oil sunflower. The model evaluation suggested that the stomatal conductance models for oil sunflower are to be improved in further research.

Influence of light, temperature and salinity on dissolved organic carbon exudation rates in Zostera marina L.

PubMed Central

2012-01-01

Background Marine angiosperms, seagrasses, are sentinel species of marine ecosystem health and function. Seagrass carbon budgets provide insight on the minimum requirements needed to maintain this valuable resource. Carbon budgets are a balance between C fixation, growth, storage and loss rates, most of which are well characterized. However, relatively few measurements of dissolved organic carbon (DOC) leaf exudation or rhizodeposition rates exist for most seagrass species. Here I evaluate how eelgrass (Zostera marina L.) DOC exudation is affected by a single factor manipulation (light, temperature or salinity). Eelgrass plants were hydroponically exposed to treatments in experimental chambers (separate leaf and rhizome/root compartments) with artificial seawater medium. Regression analysis of changes in the DOC concentration through time was used to calculate DOC exudation rates. Results Exudation rates were similar across all treatments in all experiments. For all experiments, pooled leaf DOC exudation ranged between 0.032 and 0.069 mg C gdw-1 h-1, while rhizodeposition ranged between 0.024 and 0.045 mg C gdw-1 h-1. These rates are consistent with previously published values and provide first-order estimates for mechanistic models. Conclusions Zostera marina carbon losses from either leaf exudation or rhizodeposition account for a small proportion of gross primary production (1.2-4.6%) and appear to be insensitive to short-term (e.g., hours to days) environmental variations in chamber experiments. Based on these preliminary experiments, I suggest that Z. marina DOC exudation may be a passive process and not an active transport process. PMID:22938529

Research on spatial distribution of photosynthetic characteristics of Winter Wheat

NASA Astrophysics Data System (ADS)

Yan, Q. Q.; Zhou, Q. Y.; Zhang, B. Z.; Han, X.; Han, N. N.; Li, S. M.

2018-03-01

In order to explore the spatial distribution of photosynthetic characteristics of winter wheat leaf, the photosynthetic rate on different parts of leaf (leaf base-leaf middle-leaf apex) and that on each canopy (top layer-middle layer-bottom layer) leaf during the whole growth period of winter wheat were measured. The variation of photosynthetic rate with PAR and the spatial distribution of winter wheat leaf during the whole growth periods were analysed. The results showed that the photosynthetic rate of different parts of winter wheat increased with the increase of PAR, which was showed as leaf base>leaf middle>leaf apex. In the same growth period, photosynthetic rate in different parts of the tablet was showed as leaf middle>leaf base>leaf apex. For the different canopy layer of winter wheat, the photosynthetic rate of the top layer leaf was significantly greater than that of the middle layer and lower layer leaf. The photosynthetic rate of the top layer leaf was the largest in the leaf base position. The photosynthetic rate of leaf of the same canopy layer at different growth stages were showed as tasseling stage >grain filling stage > maturation stage.

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).

Stomatal dynamics are limited by leaf hydraulics in ferns and conifers: results from simultaneous measurements of liquid and vapour fluxes in leaves.

PubMed

Martins, Samuel C V; McAdam, Scott A M; Deans, Ross M; DaMatta, Fábio M; Brodribb, Tim J

2016-03-01

Stomatal responsiveness to vapour pressure deficit (VPD) results in continuous regulation of daytime gas-exchange directly influencing leaf water status and carbon gain. Current models can reasonably predict steady-state stomatal conductance (gs ) to changes in VPD but the gs dynamics between steady-states are poorly known. Here, we used a diverse sample of conifers and ferns to show that leaf hydraulic architecture, in particular leaf capacitance, has a major role in determining the gs response time to perturbations in VPD. By using simultaneous measurements of liquid and vapour fluxes into and out of leaves, the in situ fluctuations in leaf water balance were calculated and appeared to be closely tracked by changes in gs thus supporting a passive model of stomatal control. Indeed, good agreement was found between observed and predicted gs when using a hydropassive model based on hydraulic traits. We contend that a simple passive hydraulic control of stomata in response to changes in leaf water status provides for efficient stomatal responses to VPD in ferns and conifers, leading to closure rates as fast or faster than those seen in most angiosperms. © 2015 John Wiley & Sons Ltd.

Non-nodulated bacterial leaf symbiosis promotes the evolutionary success of its host plants in the coffee family (Rubiaceae).

PubMed

Verstraete, Brecht; Janssens, Steven; Rønsted, Nina

2017-08-01

Every plant species on Earth interacts in some way or another with microorganisms and it is well known that certain forms of symbiosis between different organisms can drive evolution. Within some clades of Rubiaceae (coffee family), a specific plant-bacteria interaction exists in which non-pathological endophytes are present in the leaves of their hosts. It is hypothesized that the bacterial endophytes, either alone or by interacting with the host, provide chemical protection against herbivory or pathogens by producing toxic or otherwise advantageous secondary metabolites. If the bacteria indeed have a direct beneficial influence on their hosts, it is reasonable to assume that the endophytes may increase the fitness of their hosts and therefore it is probable that their presence also has an influence on the long-term evolution of the particular plant lineages. In this study, the possible origin in time of non-nodulated bacterial leaf symbiosis in the Vanguerieae tribe of Rubiaceae is elucidated and dissimilarities in evolutionary dynamics between species with endophytes versus species without are investigated. Bacterial leaf symbiosis is shown to have most probably originated in the Late Miocene, a period when the savannah habitat is believed to have expanded on the African continent and herbivore pressure increased. The presence of bacterial leaf endophytes appears to be restricted to Old World lineages so far. Plant lineages with leaf endophytes show a significantly higher speciation rate than plant lineages without endophytes, while there is only a small difference in extinction rate. The transition rate shows that evolving towards having endophytes is twice as fast as evolving towards not having endophytes, suggesting that leaf symbiosis must be beneficial for the host plants. We conclude that the presence of bacterial leaf endophytes may also be an important driver for speciation of host plants. Copyright © 2017 Elsevier Inc. All rights reserved.

Involvement of Abscisic Acid in PSII Photodamage and D1 Protein Turnover for Light-Induced Premature Senescence of Rice Flag Leaves

PubMed Central

Wang, Fubiao; Liu, Jianchao; Chen, Minxue; Zhou, Lujian; Li, Zhaowei; Zhao, Qian; Pan, Gang; Zaidi, Syed-Hassan-Raza; Cheng, Fangmin

2016-01-01

D1 protein in the PSII reaction center is the major target of photodamage, and it exhibits the highest turnover rate among all the thylakoid proteins. In this paper, rice psf (premature senescence of flag leaves) mutant and its wild type were used to investigate the genotype-dependent alteration in PSII photo-damage and D1 protein turnover during leaf senescence and its relation to ABA accumulation in senescent leaves. The symptom and extent of leaf senescence of the psf mutant appeared to be sunlight-dependent under natural field condition. The psf also displayed significantly higher levels of ABA accumulation in senescent leaves than the wild type. However, the premature senescence lesion of psf leaves could be alleviated by shaded treatment, concomitantly with the strikingly suppressed ABA level in the shaded areas of flag leaves. The change in ABA concentration contributed to the regulation of shade-delayed leaf senescence. The participation of ABA in the timing of senescence initiation and in the subsequent rate of leaf senescence was closely associated with PSII photodamage and D1 protein turnover during leaf senescence, in which the transcriptional expression of several key genes (psbA, psbB, psbC and OsFtsH2) involved in D1 protein biosynthesis and PSII repair cycle was seriously suppressed by the significantly increased ABA level. This response resulted in the low rate of D1 protein synthesis and impaired repair recovery in the presence of ABA. The psf showed evidently decreased D1 protein amount in the senescent leaves. Both the inhibition of de novo synthesized D1 protein and the slow rate of proteolytic removal for the photodamaged D1 protein was among the most crucial steps for the linkage between light-dependent leaf senescence and the varying ABA concentration in psf mutant leaves. OsFtsH2 transcriptional expression possibly played an important role in the regulation of D1 protein turnover and PSII repair cycle in relation to ABA mediated leaf senescence. PMID:27532299

Phloem transport velocity varies over time and among vascular bundles during early cucumber seedling development.

PubMed

Savage, Jessica A; Zwieniecki, Maciej A; Holbrook, N Michele

2013-11-01

We use a novel dye-tracing technique to measure in vivo phloem transport velocity in cucumber (Cucumis sativus) plants during early seedling development. We focus on seedlings because of their importance in plant establishment and because they provide a simple source and sink model of phloem transport. The dye-tracing method uses a photodiode to track the movement of a bleach front of fluorescent dye traveling in the phloem from the cotyledons (source) to the roots (sink). During early seedling development, phloem transport velocity in this direction can change 2-fold depending on vascular connectivity and the number of actively growing sinks. Prior to leaf expansion, vascular bundles attached to the first developing leaf demonstrate a decline in basipetal phloem transport that can be alleviated by the leaf's removal. At this stage, seedlings appear carbon limited and phloem transport velocity is correlated with cotyledon area, a pattern that is apparent both during cotyledon expansion and after source area manipulation. When the first leaf transitions to a carbon source, seedling growth rate increases and basipetal phloem transport velocity becomes more stable. Because bundles appear to operate autonomously, transport velocity can differ among vascular bundles. Together, these results demonstrate the dynamic and heterogeneous nature of phloem transport and underline the need for a better understanding of how changes in phloem physiology impact growth and allocation at this critical stage of development.

Betaine synthesis from radioactive precursors in attached, water-stressed barley leaves

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

Hanson, A.D.; Scott, N.A.

1980-08-01

In wilted barley leaves, betaine accumulates at about 200 nanomoles per 10 centimeters leaf per day. Results with /sup 14/C-labeled precursors were qualitatively and quantitatively consistent with de novo synthesis of this betaine from serine via ethanolamine, choline, and betaine aldehyde and indicated that water stress may increase the activities of all steps in this pathway except the last. Doses (I micromole) of each /sup 14/C-labeled precursor were supplied as droplets to the tips of attached, 10-centimeter, second-leaf blades of turgid and wilted plants, and the incorporation of /sup 14/C into betaine was followed. From the rates of betaine labeling,more » estimates were made of the potential capacities (nanomoles per 10 centimeters leaf per day) for the methylation and oxidation steps. Labeling of betaine from absolute value /sup 14/C choline, absolute value /sup 14/C ethanolamine, and absolute value /sup 14/C serine was about 7- to 10-fold greater in leaves wilted for 2 days than in turgid leaves, whereas label from absolute value /sup 14/C betaine aldehyde appeared in betaine at about the same rate in both turgid and wilted leaves. In leaves wilted for 2 days, the potential capacities for converting absolute value /sup 14/C ethanolamine, absolute value /sup 14/C choline, and absolute value /sup 14/C betaine aldehyde to betaine all approached or exceeded the rate of betain accumulation (about 200 nanomoles per 10 centimeters leaf per day); in turgid leaves, only the potential for converting betaine aldehyde to betaine exceeded this rate. The rate of conversion of absolute value /sup 14/C ethanolamine to betaine increased 4-fold after 6 to 10 hours of wilting, which was soon enough to account for the onset of betaine accumulation.« less

Comparative responses of the Savanna grasses Cenchrus ciliaris and Themeda triandra to defoliation.

PubMed

Hodgkinson, K C; Ludlow, M M; Mott, J J; Baruch, Z

1989-04-01

Two perennial tussock grasses of savannas were compared in a glasshouse study to determine why they differed in their ability to withstand frequent, heavy grazing; Cenchrus ciliaris is tolerant and Themeda triandra is intolerant of heavy grazing. Frequent defoliation at weekly intervals for six weeks reduced shoot biomass production over a subsequent 42 day regrowth period compared with previously undefoliated plants (infrequent) in T. triandra, but not in C. ciliaris. Leaf area of T. triandra expanded rapidly following defoliation but high initial relative growth rates of shoots were not sustained after 14 days of regrowth because of reducing light utilising efficiency of leaves. Frequently defoliated plants were slower in rate of leaf area expansion and this was associated with reduced photosynthetic capacity of newly formed leaves, lower allocation of photosynthate to leaves but not lower tiller numbers. T. triandra appears well adapted to a regime where defoliation is sufficiently infrequent to allow carbon to be fixed to replace that used in initial leaf area expansion. In contrast, C. ciliaris is better adapted to frequent defoliation than is T. triandra, because horizontally orientated nodal tillers are produced below the defoliation level. This morphological adaptation resulted in a 10-fold higher leaf area remaining after defoliation compared with similarly defoliated T. triandra, which together with the maintenance of moderate levels of light utilising efficiency, contributed to the higher leaf area and shoot weight throughout the regrowth period.

Dynamic quantification of canopy structure to characterize early plant vigour in wheat genotypes

PubMed Central

Duan, T.; Chapman, S.C.; Holland, E.; Rebetzke, G.J.; Guo, Y.; Zheng, B.

2016-01-01

Early vigour is an important physiological trait to improve establishment, water-use efficiency, and grain yield for wheat. Phenotyping large numbers of lines is challenging due to the fast growth and development of wheat seedlings. Here we developed a new photo-based workflow to monitor dynamically the growth and development of the wheat canopy of two wheat lines with a contrasting early vigour trait. Multiview images were taken using a ‘vegetation stress’ camera at 2 d intervals from emergence to the sixth leaf stage. Point clouds were extracted using the Multi-View Stereo and Structure From Motion (MVS-SFM) algorithm, and segmented into individual organs using the Octree method, with leaf midribs fitted using local polynomial function. Finally, phenotypic parameters were calculated from the reconstructed point cloud including: tiller and leaf number, plant height, Haun index, phyllochron, leaf length, angle, and leaf elongation rate. There was good agreement between the observed and estimated leaf length (RMSE=8.6mm, R 2=0.98, n=322) across both lines. Significant contrasts of phenotyping parameters were observed between the two lines and were consistent with manual observations. The early vigour line had fewer tillers (2.4±0.6) and larger leaves (308.0±38.4mm and 17.1±2.7mm for leaf length and width, respectively). While the phyllochron of both lines was quite similar, the non-vigorous line had a greater Haun index (more leaves on the main stem) on any date, as the vigorous line had slower development of its first two leaves. The workflow presented in this study provides an efficient method to phenotype individual plants using a low-cost camera (an RGB camera is also suitable) and could be applied in phenotyping for applications in both simulation modelling and breeding. The rapidity and accuracy of this novel method can characterize the results of specific selection criteria (e.g. width of leaf three, number of tillers, rate of leaf appearance) that have been or can now be utilized to breed for early leaf growth and tillering in wheat. PMID:27312669

Dynamic quantification of canopy structure to characterize early plant vigour in wheat genotypes.

PubMed

Duan, T; Chapman, S C; Holland, E; Rebetzke, G J; Guo, Y; Zheng, B

2016-08-01

Early vigour is an important physiological trait to improve establishment, water-use efficiency, and grain yield for wheat. Phenotyping large numbers of lines is challenging due to the fast growth and development of wheat seedlings. Here we developed a new photo-based workflow to monitor dynamically the growth and development of the wheat canopy of two wheat lines with a contrasting early vigour trait. Multiview images were taken using a 'vegetation stress' camera at 2 d intervals from emergence to the sixth leaf stage. Point clouds were extracted using the Multi-View Stereo and Structure From Motion (MVS-SFM) algorithm, and segmented into individual organs using the Octree method, with leaf midribs fitted using local polynomial function. Finally, phenotypic parameters were calculated from the reconstructed point cloud including: tiller and leaf number, plant height, Haun index, phyllochron, leaf length, angle, and leaf elongation rate. There was good agreement between the observed and estimated leaf length (RMSE=8.6mm, R (2)=0.98, n=322) across both lines. Significant contrasts of phenotyping parameters were observed between the two lines and were consistent with manual observations. The early vigour line had fewer tillers (2.4±0.6) and larger leaves (308.0±38.4mm and 17.1±2.7mm for leaf length and width, respectively). While the phyllochron of both lines was quite similar, the non-vigorous line had a greater Haun index (more leaves on the main stem) on any date, as the vigorous line had slower development of its first two leaves. The workflow presented in this study provides an efficient method to phenotype individual plants using a low-cost camera (an RGB camera is also suitable) and could be applied in phenotyping for applications in both simulation modelling and breeding. The rapidity and accuracy of this novel method can characterize the results of specific selection criteria (e.g. width of leaf three, number of tillers, rate of leaf appearance) that have been or can now be utilized to breed for early leaf growth and tillering in wheat. © The Author 2016. Published by Oxford University Press on behalf of the Society for Experimental Biology.

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.

Photosynthetic carbon fixation characteristics of fruiting structures of Brassica campestris L

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

Singal, H.R.; Sheoran, I.S.; Singh, R.

1987-04-01

Activities of key enzymes of the Calvin cycle and C/sub 4/ metabolism, rates of CO/sub 2/ fixation, and the initial products of photosynthetic /sup 14/CO/sub 2/ fixation were determined in the podwall, seed coat (fruiting structures), and the subtending leaf (leaf below a receme) of Brassica campestris L. cv Toria. Compared to activities of ribulose-1,5-bisphosphate carboxylase and other Calvin cycle enzymes, e.g. NADP-glyceraldehyde-3-phosphate-dehydrogenase and ribulose-5-phosphate kinase, the activities of phosphoenol pyruvate carboxylase and other enzymes of C/sub 4/ metabolism, viz. NADP-malate dehydrogenase, NADP-malic enzyme, glutamate pyruvate transaminase, and glutamate oxaloacetate transaminase, were generally much higher in seed than in podwallmore » and leaf. Podwall and leaf were comparable to each other. Pulse-chase experiments showed that in seed the major product of /sup 14/CO/sub 2/ assimilation was malate (in short time), whereas in podwall and leaf, the label initially appeared in 3-PGA. With time, the label moved to sucrose. In contrast to legumes, Brassica pods were able to fix net CO/sub 2/ during light. However, respiratory losses were very high during the dark period.« less

Green light drives leaf photosynthesis more efficiently than red light in strong white light: revisiting the enigmatic question of why leaves are green.

PubMed

Terashima, Ichiro; Fujita, Takashi; Inoue, Takeshi; Chow, Wah Soon; Oguchi, Riichi

2009-04-01

The literature and our present examinations indicate that the intra-leaf light absorption profile is in most cases steeper than the photosynthetic capacity profile. In strong white light, therefore, the quantum yield of photosynthesis would be lower in the upper chloroplasts, located near the illuminated surface, than that in the lower chloroplasts. Because green light can penetrate further into the leaf than red or blue light, in strong white light, any additional green light absorbed by the lower chloroplasts would increase leaf photosynthesis to a greater extent than would additional red or blue light. Based on the assessment of effects of the additional monochromatic light on leaf photosynthesis, we developed the differential quantum yield method that quantifies efficiency of any monochromatic light in white light. Application of this method to sunflower leaves clearly showed that, in moderate to strong white light, green light drove photosynthesis more effectively than red light. The green leaf should have a considerable volume of chloroplasts to accommodate the inefficient carboxylation enzyme, Rubisco, and deliver appropriate light to all the chloroplasts. By using chlorophylls that absorb green light weakly, modifying mesophyll structure and adjusting the Rubisco/chlorophyll ratio, the leaf appears to satisfy two somewhat conflicting requirements: to increase the absorptance of photosynthetically active radiation, and to drive photosynthesis efficiently in all the chloroplasts. We also discuss some serious problems that are caused by neglecting these intra-leaf profiles when estimating whole leaf electron transport rates and assessing photoinhibition by fluorescence techniques.

Photosynthetic properties of C4 plants growing in an African savanna/wetland mosaic.

PubMed

Mantlana, K B; Arneth, A; Veenendaal, E M; Wohland, P; Wolski, P; Kolle, O; Wagner, M; Lloyd, J

2008-01-01

Photosynthesis rates and photosynthesis-leaf nutrient relationships were analysed in nine tropical grass and sedge species growing in three different ecosystems: a rain-fed grassland, a seasonal floodplain, and a permanent swamp, located along a hydrological gradient in the Okavango Delta, Botswana. These investigations were conducted during the rainy season, at a time of the year when differences in growth conditions between the sites were relatively uniform. At the permanent swamp, the largest variations were found for area-based leaf nitrogen contents, from 20 mmol m(-2) to 140 mmol m(-2), nitrogen use efficiencies (NUE), from 0.2 mmol (C) mol(-1) (N) s(-1) to 2.0 mmol (C) mol(-1) (N) s(-1), and specific leaf areas (SLA), from 50 cm(2) g(-1) to 400 cm(2) g(-1). For the vegetation growing at the rain-fed grassland, the highest leaf gas exchange rates, high leaf nutrient levels, a low ratio of intercellular to ambient CO(2) concentration, and high carboxylation efficiency were found. Taken together, these observations indicate a very efficient growth strategy that is required for survival and reproduction during the relatively brief period of water availability. The overall lowest values of light-saturated photosynthesis (A(sat)) were observed at the seasonal floodplain; around 25 micromol m(-2) s(-1) and 30 micromol m(-2) s(-1). To place these observations into the broader context of functional leaf trait analysis, relationships of photosynthesis rates, specific leaf area, and foliar nutrient levels were plotted, in the same way as was done for previously published 'scaling relationships' that are based largely on C(3) plants, noting the differences in the analyses between this study and the previous study. The within- and across-species variation in both A(sat) and SLA appeared better predicted by foliar phosphorus content (dry mass or area basis) rather than by foliar nitrogen concentrations, possibly because the availability of phosphorus is even more critical than the availability of nitrogen in the studied relatively oligotrophic ecosystems.

Leaf Dynamics of Panicum maximum under Future Climatic Changes

PubMed Central

Britto de Assis Prado, Carlos Henrique; Haik Guedes de Camargo-Bortolin, Lívia; Castro, Érique; Martinez, Carlos Alberto

2016-01-01

Panicum maximum Jacq. ‘Mombaça’ (C4) was grown in field conditions with sufficient water and nutrients to examine the effects of warming and elevated CO2 concentrations during the winter. Plants were exposed to either the ambient temperature and regular atmospheric CO2 (Control); elevated CO2 (600 ppm, eC); canopy warming (+2°C above regular canopy temperature, eT); or elevated CO2 and canopy warming (eC+eT). The temperatures and CO2 in the field were controlled by temperature free-air controlled enhancement (T-FACE) and mini free-air CO2 enrichment (miniFACE) facilities. The most green, expanding, and expanded leaves and the highest leaf appearance rate (LAR, leaves day-1) and leaf elongation rate (LER, cm day-1) were observed under eT. Leaf area and leaf biomass were higher in the eT and eC+eT treatments. The higher LER and LAR without significant differences in the number of senescent leaves could explain why tillers had higher foliage area and leaf biomass in the eT treatment. The eC treatment had the lowest LER and the fewest expanded and green leaves, similar to Control. The inhibitory effect of eC on foliage development in winter was indicated by the fewer green, expanded, and expanding leaves under eC+eT than eT. The stimulatory and inhibitory effects of the eT and eC treatments, respectively, on foliage raised and lowered, respectively, the foliar nitrogen concentration. The inhibition of foliage by eC was confirmed by the eC treatment having the lowest leaf/stem biomass ratio and by the change in leaf biomass-area relationships from linear or exponential growth to rectangular hyperbolic growth under eC. Besides, eC+eT had a synergist effect, speeding up leaf maturation. Therefore, with sufficient water and nutrients in winter, the inhibitory effect of elevated CO2 on foliage could be partially offset by elevated temperatures and relatively high P. maximum foliage production could be achieved under future climatic change. PMID:26894932

Rumen Bacterial Degradation of Forage Cell Walls Investigated by Electron Microscopy

PubMed Central

Akin, Danny E.; Amos, Henry E.

1975-01-01

The association of rumen bacteria with specific leaf tissues of the forage grass Kentucky-31 tall fescue (Festuca arundinacea Schreb.) during in vitro degradation was investigated by transmission and scanning electron microscopy. Examination of degraded leaf cross-sections revealed differential rates of tissue degradation in that the cell walls of the mesophyll and pholem were degraded prior to those of the outer bundle sheath and epidermis. Rumen bacteria appeared to degrade the mesophyll, in some cases, and phloem without prior attachment to the plant cell walls. The degradation of bundle sheath and epidermal cell walls appeared to be preceded by attachment of bacteria to the plant cell wall. Ultrastructural features apparently involved in the adhesion of large cocci to plant cells were observed by transmission and scanning electron microscopy. The physical association between plant and rumen bacterial cells during degradation apparently varies with tissue types. Bacterial attachment, by extracellular features in some microorganisms, is required prior to degradation of the more resistant tissues. Images PMID:16350017

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 responses of light interception, photosynthesis and fruit yield of cucumber to LED-lighting within the canopy.

PubMed

Trouwborst, Govert; Oosterkamp, Joke; Hogewoning, Sander W; Harbinson, Jeremy; van Ieperen, Wim

2010-03-01

Mathematical models of light attenuation and canopy photosynthesis suggest that crop photosynthesis increases by more uniform vertical irradiance within crops. This would result when a larger proportion of total irradiance is applied within canopies (interlighting) instead of from above (top lighting). These irradiance profiles can be generated by Light Emitting Diodes (LEDs). We investigated the effects of interlighting with LEDs on light interception, on vertical gradients of leaf photosynthetic characteristics and on crop production and development of a greenhouse-grown Cucumis sativus'Samona' crop and analysed the interaction between them. Plants were grown in a greenhouse under low natural irradiance (winter) with supplemental irradiance of 221 micromol photosynthetic photon flux m(-2) s(-1) (20 h per day). In the interlighting treatment, LEDs (80% Red, 20% Blue) supplied 38% of the supplemental irradiance within the canopy with 62% as top lighting by High-Pressure Sodium (HPS)-lamps. The control was 100% top lighting (HPS lamps). We measured horizontal and vertical light extinction as well as leaf photosynthetic characteristics at different leaf layers, and determined total plant production. Leaf mass per area and dry mass allocation to leaves were significantly greater but leaf appearance rate and plant length were smaller in the interlighting treatment. Although leaf photosynthetic characteristics were significantly increased in the lower leaf layers, interlighting did not increase total biomass or fruit production, partly because of a significantly reduced vertical and horizontal light interception caused by extreme leaf curling, likely because of the LED-light spectrum used, and partly because of the relatively low irradiances from above.

Correlated evolution of stem and leaf hydraulic traits in Pereskia (Cactaceae).

PubMed

Edwards, Erika J

2006-01-01

Recent studies have demonstrated significant correlations between stem and leaf hydraulic properties when comparing across species within ecological communities. This implies that these traits are co-evolving, but there have been few studies addressing plant water relations within an explicitly evolutionary framework. This study tests for correlated evolution among a suite of plant water-use traits and environmental parameters in seven species of Pereskia (Cactaceae), using phylogenetically independent contrasts. There were significant evolutionary correlations between leaf-specific xylem hydraulic conductivity, Huber Value, leaf stomatal pore index, leaf venation density and leaf size, but none of these traits appeared to be correlated with environmental water availability; only two water relations traits - mid-day leaf water potentials and photosynthetic water use efficiency - correlated with estimates of moisture regime. In Pereskia, it appears that many stem and leaf hydraulic properties thought to be critical to whole-plant water use have not evolved in response to habitat shifts in water availability. This may be because of the extremely conservative stomatal behavior and particular rooting strategy demonstrated by all Pereskia species investigated. These results highlight the need for a lineage-based approach to understand the relative roles of functional traits in ecological adaptation.

Plant morphological characteristics and resistance to simulated trampling

NASA Astrophysics Data System (ADS)

Sun, Dan; Liddle, Michael J.

1993-07-01

The relationship between responses of plants to trampling and their morphological characteristics was studied in a glasshouse experiment. Thirteen species with four different growth forms were used in this experiment. They were five tussock species. Chloris gayana, Eragrostis tenuifolia, Lolium perenne, Panicum maximum, and Sporobolus elongatus; three prostate grasses, Axonopus compressus, Cynodon dactylon, and Trifolium repens, two herbaceous species, Daucus glochidiatus and Hypochoeris radicata; and three woody species, Acacia macradenia, Acrotriche aggregata, and Sida rhombifolia. These species were subjected to three levels of simulated trampling. For each species, measurements were taken of aboveground biomass, root biomass, leaf length, leaf width, leaf thickness, leaf number, broken leaf number and plant height. Overall, these measurements were greatest in the control plants, moderate in the level of light trampling, and the lowest in the level of heavy trampling. Biomass was used as a basis of the assessment of plant resistance to trampling. Three tussock species, Eragrostis tenuifolia, Lolium perenne, and Sporobolus elongatus had a high resistance. Woody and erect herbaceous plants were more intolerant to trampling. There appear to be two processes involved in the reduction of the plant parameters: direct physical damage with portions of the plants detached, and physiological changes, which slow down vegetative growth rates. Plant height was found to be the most sensitive indicator of trampling damage.

Leaf-associated fungal diversity in acidified streams: insights from combining traditional and molecular approaches.

PubMed

Clivot, Hugues; Cornut, Julien; Chauvet, Eric; Elger, Arnaud; Poupin, Pascal; Guérold, François; Pagnout, Christophe

2014-07-01

We combined microscopic and molecular methods to investigate fungal assemblages on alder leaf litter exposed in the benthic and hyporheic zones of five streams across a gradient of increasing acidification for 4 weeks. The results showed that acidification and elevated Al concentrations strongly depressed sporulating aquatic hyphomycetes diversity in both zones of streams, while fungal diversity assessed by denaturing gradient gel electrophoresis (DGGE) appeared unaffected. Clone library analyses revealed that fungal communities on leaves were dominated by members of Ascomycetes and to a lesser extent by Basidiomycetes and Chytridiomycetes. An important contribution of terrestrial fungi was observed in both zones of the most acidified stream and in the hyporheic zone of the reference circumneutral stream. The highest leaf breakdown rate was observed in the circumneutral stream and occurred in the presence of both the highest diversity of sporulating aquatic hyphomycetes and the highest contribution to clone libraries of sequences affiliated with aquatic hyphomycetes. Both methods underline the major role played by aquatic hyphomycetes in leaf decomposition process. Our findings also bring out new highlights on the identity of leaf-associated fungal communities and their responses to anthropogenic alteration of running water ecosystems. © 2013 Society for Applied Microbiology and John Wiley & Sons Ltd.

The relationship of leaf photosynthetic traits V cmax and Jmax - to leaf nitrogen, leaf phosphorus, and specific leaf area: A meta-analysis and modeling study

DOE PAGES

Walker, Anthony P.; Beckerman, Andrew P.; Gu, Lianhong; ...

2014-07-25

Great uncertainty exists in the global exchange of carbon between the atmosphere and the terrestrial biosphere. An important source of this uncertainty lies in the dependency of photosynthesis on the maximum rate of carboxylation (Vcmax) and the maximum rate of electron transport (Jmax). Understanding and making accurate prediction of C fluxes thus requires accurate characterization of these rates and their relationship with plant nutrient status over large geographic scales. Plant nutrient status is indicated by the traits: leaf nitrogen (N), leaf phosphorus (P), and specific leaf area (SLA). Correlations between Vcmax and Jmax and leaf nitrogen (N) are typically derivedmore » from local to global scales, while correlations with leaf phosphorus (P) and specific leaf area (SLA) have typically been derived at a local scale. Thus, there is no global-scale relationship between Vcmax and Jmax and P or SLA limiting the ability of global-scale carbon flux models do not account for P or SLA. We gathered published data from 24 studies to reveal global relationships of Vcmax and Jmax with leaf N, P, and SLA. Vcmax was strongly related to leaf N, and increasing leaf P substantially increased the sensitivity of Vcmax to leaf N. Jmax was strongly related to Vcmax, and neither leaf N, P, or SLA had a substantial impact on the relationship. Although more data are needed to expand the applicability of the relationship, we show leaf P is a globally important determinant of photosynthetic rates. In a model of photosynthesis, we showed that at high leaf N (3 gm 2), increasing leaf P from 0.05 to 0.22 gm 2 nearly doubled assimilation rates. Lastly, we show that plants may employ a conservative strategy of Jmax to Vcmax coordination that restricts photoinhibition when carboxylation is limiting at the expense of maximizing photosynthetic rates when light is limiting.« less

The relationship of leaf photosynthetic traits V cmax and Jmax - to leaf nitrogen, leaf phosphorus, and specific leaf area: A meta-analysis and modeling study

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

Walker, Anthony P.; Beckerman, Andrew P.; Gu, Lianhong

Great uncertainty exists in the global exchange of carbon between the atmosphere and the terrestrial biosphere. An important source of this uncertainty lies in the dependency of photosynthesis on the maximum rate of carboxylation (Vcmax) and the maximum rate of electron transport (Jmax). Understanding and making accurate prediction of C fluxes thus requires accurate characterization of these rates and their relationship with plant nutrient status over large geographic scales. Plant nutrient status is indicated by the traits: leaf nitrogen (N), leaf phosphorus (P), and specific leaf area (SLA). Correlations between Vcmax and Jmax and leaf nitrogen (N) are typically derivedmore » from local to global scales, while correlations with leaf phosphorus (P) and specific leaf area (SLA) have typically been derived at a local scale. Thus, there is no global-scale relationship between Vcmax and Jmax and P or SLA limiting the ability of global-scale carbon flux models do not account for P or SLA. We gathered published data from 24 studies to reveal global relationships of Vcmax and Jmax with leaf N, P, and SLA. Vcmax was strongly related to leaf N, and increasing leaf P substantially increased the sensitivity of Vcmax to leaf N. Jmax was strongly related to Vcmax, and neither leaf N, P, or SLA had a substantial impact on the relationship. Although more data are needed to expand the applicability of the relationship, we show leaf P is a globally important determinant of photosynthetic rates. In a model of photosynthesis, we showed that at high leaf N (3 gm 2), increasing leaf P from 0.05 to 0.22 gm 2 nearly doubled assimilation rates. Lastly, we show that plants may employ a conservative strategy of Jmax to Vcmax coordination that restricts photoinhibition when carboxylation is limiting at the expense of maximizing photosynthetic rates when light is limiting.« less

Utilization of ammonium as a nitrogen source: effects of ambient acidity on growth and nitrogen accumulation by soybean

NASA Technical Reports Server (NTRS)

Tolley-Henry, L.; Raper, C. D. Jr; Raper CD, J. r. (Principal Investigator)

1986-01-01

Dry matter accumulation of plants utilizing NH4+ as the sole nitrogen source generally is less than that of plants receiving NO3- unless acidity of the root-zone is controlled at a pH of about 6.0. To test the hypothesis that the reduction in growth is a consequence of nitrogen stress within the plant in response to effects of increased acidity during uptake of NH4+ by roots, nonnodulated soybean plants (Glycine max [L.] Merr. cv Ransom) were grown for 24 days in flowing nutrient culture containing 1.0 millimolar NH4+ as the nitrogen source. Acidities of the culture solutions were controlled at pH 6.1, 5.1, and 4.1 +/- 0.1 by automatic additions of 0.01 N H2SO4 or Ca(OH)2. Plants were sampled at intervals of 3 to 4 days for determination of dry matter and nitrogen accumulation. Rates of NH4+ uptake per gram root dry weight were calculated from these data. Net CO2 exchange rates per unit leaf area were measured on attached leaves by infrared gas analysis. When acidity of the culture solution was increased from pH 6.1 to 5.1, dry matter and nitrogen accumulation were reduced by about 40% within 14 days. Net CO2 exchange rates per unit leaf area, however, were not affected, and the decreased growth was associated with a reduction in rates of appearance and expansion of new leaves. The uptake rates of NH4+ per gram root were about 25% lower throughout the 24 days at pH 5.1 than at 6.1. A further increase in solution acidity from pH 5.1 to 4.1 resulted in cessation of net dry matter production and appearance of new leaves within 10 days. Net CO2 exchange rates per unit leaf area declined rapidly until all viable leaves had abscised by 18 days. Uptake rates of NH4+, which were initially about 50% lower at pH 4.1 than at 6.1 continued to decline with time of exposure until net uptake ceased at 10 days. Since these responses also are characteristic of the sequence of responses that occur during onset and progression of a nitrogen stress, they corroborate our hypothesis.

Phenology, growth and physiological adjustments of oil palm (Elaeis guineensis) to sink limitation induced by fruit pruning

PubMed Central

Legros, S.; Mialet-Serra, I.; Caliman, J.-P.; Siregar, F. A.; Clement-Vidal, A.; Fabre, D.; Dingkuhn, M.

2009-01-01

Background and Aims Despite its simple architecture and small phenotypic plasticity, oil palm has complex phenology and source–sink interactions. Phytomers appear in regular succession but their development takes years, involving long lag periods between environmental influences and their effects on sinks. Plant adjustments to resulting source–sink imbalances are poorly understood. This study investigated oil palm adjustments to imbalances caused by severe fruit pruning. Methods An experiment with two treatments (control and complete fruit pruning) during 22 months in 2006–2008) and six replications per treatment was conducted in Indonesia. Phenology, growth of above-ground vegetative and reproductive organs, leaf morphology, inflorescence sex differentiation, dynamics of non-structural carbohydrate reserves and light-saturated net photosynthesis (Amax) were monitored. Key Results Artificial sink limitation by complete fruit pruning accelerated development rate, resulting in higher phytomer, leaf and inflorescence numbers. Leaf size and morphology remained unchanged. Complete fruit pruning also suppressed the abortion of male inflorescences, estimated to be triggered at about 16 months before bunch maturity. The number of female inflorescences increased after an estimated lag of 24–26 months, corresponding to time from sex differentiation to bunch maturity. The most important adjustment process was increased assimilate storage in the stem, attaining nearly 50 % of dry weight in the stem top, mainly as starch, whereas glucose, which in controls was the most abundant non-structural carbohydrate stored in oil palm, decreased. Conclusions The development rate of oil palm is in part controlled by source–sink relationships. Although increased rate of development and proportion of female inflorescences constituted observed adjustments to sink limitation, the low plasticity of plant architecture (constant leaf size, absence of branching) limited compensatory growth. Non-structural carbohydrate storage was thus the main adjustment process. PMID:19748908

Increasing leaf hydraulic conductance with transpiration rate minimizes the water potential drawdown from stem to leaf

PubMed Central

Simonin, Kevin A.; Burns, Emily; Choat, Brendan; Barbour, Margaret M.; Dawson, Todd E.; Franks, Peter J.

2015-01-01

Leaf hydraulic conductance (k leaf) is a central element in the regulation of leaf water balance but the properties of k leaf remain uncertain. Here, the evidence for the following two models for k leaf in well-hydrated plants is evaluated: (i) k leaf is constant or (ii) k leaf increases as transpiration rate (E) increases. The difference between stem and leaf water potential (ΔΨstem–leaf), stomatal conductance (g s), k leaf, and E over a diurnal cycle for three angiosperm and gymnosperm tree species growing in a common garden, and for Helianthus annuus plants grown under sub-ambient, ambient, and elevated atmospheric CO2 concentration were evaluated. Results show that for well-watered plants k leaf is positively dependent on E. Here, this property is termed the dynamic conductance, k leaf(E), which incorporates the inherent k leaf at zero E, which is distinguished as the static conductance, k leaf(0). Growth under different CO2 concentrations maintained the same relationship between k leaf and E, resulting in similar k leaf(0), while operating along different regions of the curve owing to the influence of CO2 on g s. The positive relationship between k leaf and E minimized variation in ΔΨstem–leaf. This enables leaves to minimize variation in Ψleaf and maximize g s and CO2 assimilation rate over the diurnal course of evaporative demand. PMID:25547915

[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.

Occurrence and severity of foliar ozone symptoms on sensitive hardwood species in Shenandoah National Park, VA

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

Hildebrand, E.; Skelly, J.M.

1993-02-01

To assess the extent of foliar symptoms due to ozone on sensitive hardwoods in the Shenandoah National Park in Virginia, three species were sampled and evaluated at sites of differing elevations adjacent to 3 ozone monitors in 1991 and 1992: black cherry, yellow poplar, and white ash. All foliar samples were evaluated to precent of symptomatic leaves on each branch and average precent leaf area affected. The Horsfall-Barratt rating scale was used to estimate the precent leaf area symptomatic. Ozone symptoms were manifested as stipple on the adazial leaf surface. In the preliminary 1991 sampling, 40, 87, and 7% ofmore » black cherry trees sampled were found to be symptomatic at the 3 sites; 63 and 67% of yellow poplar trees sampled were found to be symptomatic at sites 1 and 3, as were 43 and 63% of the white ash at sites 1 and 2 (3 complete sets were not found in 1991). In 1992, the sampling and rating of injury were repeated. Symptoms of ozone injury appeared on 23, 88, and 10% of black cherry, on 17, 7, and 80% of yellow poplar, and 27, 40, and 40% of white ash. Elevation and ozone exposure will be discussed.« less

Gradual and contingent evolutionary emergence of leaf mimicry in butterfly wing patterns.

PubMed

Suzuki, Takao K; Tomita, Shuichiro; Sezutsu, Hideki

2014-11-25

Special resemblance of animals to natural objects such as leaves provides a representative example of evolutionary adaptation. The existence of such sophisticated features challenges our understanding of how complex adaptive phenotypes evolved. Leaf mimicry typically consists of several pattern elements, the spatial arrangement of which generates the leaf venation-like appearance. However, the process by which leaf patterns evolved remains unclear. In this study we show the evolutionary origin and process for the leaf pattern in Kallima (Nymphalidae) butterflies. Using comparative morphological analyses, we reveal that the wing patterns of Kallima and 45 closely related species share the same ground plan, suggesting that the pattern elements of leaf mimicry have been inherited across species with lineage-specific changes of their character states. On the basis of these analyses, phylogenetic comparative methods estimated past states of the pattern elements and enabled reconstruction of the wing patterns of the most recent common ancestor. This analysis shows that the leaf pattern has evolved through several intermediate patterns. Further, we use Bayesian statistical methods to estimate the temporal order of character-state changes in the pattern elements by which leaf mimesis evolved, and show that the pattern elements changed their spatial arrangement (e.g., from a curved line to a straight line) in a stepwise manner and finally establish a close resemblance to a leaf venation-like appearance. Our study provides the first evidence for stepwise and contingent evolution of leaf mimicry.　 Leaf mimicry patterns evolved in a gradual, rather than a sudden, manner from a non-mimetic ancestor. Through a lineage of Kallima butterflies, the leaf patterns evolutionarily originated through temporal accumulation of orchestrated changes in multiple pattern elements.

Distribution of Metabolites between Chloroplast and Cytoplasm during the Induction Phase of Photosynthesis in Leaf Protoplasts 1

PubMed Central

Robinson, Simon P.; Walker, David A.

1980-01-01

A method for rapid separation of the chloroplast and cytoplasmic fractions from isolated leaf protoplasts of wheat and spinach has been used to determine the distribution of 14C-labeled products during photosynthesis. In the dark, CO2 fixation was only 1 to 2% of that in the light and the products were mainly in the cytoplasmic fraction suggesting fixation by phosphoenolpyruvate carboxylase. Label appeared rapidly in the chloroplast fraction following illumination but the amount leveled off after 4 to 5 minutes reflecting the buildup of intermediates to steady state levels. There was only a slight lag before label appeared in the cytoplasmic fraction and it continued to increase at a constant rate reflecting synthesis of neutral products. In the light, the percentage of label in the chloroplast fraction decreased rapidly in the first minute of illumination and was only 10 to 20% in the steady-state. It is suggested that the chloroplast phosphate transporter promotes a rapid transfer of sugar phosphates from the chloroplast to the cytoplasm, even during the induction phase of photosynthesis. PMID:16661305

Plant architecture and prey distribution influence foraging behavior of the predatory mite Phytoseiulus persimilis (Acari: Phytoseiidae).

PubMed

Gontijo, Lessando M; Nechols, James R; Margolies, David C; Cloyd, Raymond A

2012-01-01

The arrangement, number, and size of plant parts may influence predator foraging behavior, either directly, by altering the rate or pattern of predator movement, or, indirectly, by affecting the distribution and abundance of prey. We report on the effects of both plant architecture and prey distribution on foraging by the predatory mite, Phytoseiulus persimilis Athias-Henriot (Acari: Phytoseiidae), on cucumber (Cucumis sativus L.). Plants differed in leaf number (2- or 6-leafed), and there were associated differences in leaf size, plant height, and relative proportions of plant parts; but all had the same total surface area. The prey, the twospotted spider mite Tetranychus urticae Koch (Acari: Tetranychidae), were distributed either on the basal leaf or on all leaves. The effect of plant architecture on predator foraging behavior varied depending on prey distribution. The dimensions of individual plant parts affected time allocated to moving and feeding, but they did not appear to influence the frequency with which predators moved among different plant parts. Overall, P. persimilis moved less, and fed upon prey longer, on 6-leafed plants with prey on all leaves than on plants representing other treatment combinations. Our findings suggest that both plant architecture and pattern of prey distribution should be considered, along with other factors such as herbivore-induced plant volatiles, in augmentative biological control programs.

Thermotolerance and responses to short duration heat stress in tropical and temperate species

NASA Astrophysics Data System (ADS)

Marias, D.; Meinzer, F. C.; Still, C. J.

2017-12-01

Temperature and heat waves are predicted to increase throughout the 21st century in both tropical and temperate regions. Tropical species are vulnerable to heat stress because of the higher radiation load and the narrower distribution of temperatures typically experienced compared to extratropical species. Germinant seedlings are also vulnerable to heat stress because they inhabit the boundary layer close to the soil surface where intense heating occurs. We quantified the effect of leaf age and heat stress duration (45 min, 90 min) on leaf thermotolerance and whole plant physiological responses to heat stress in Coffea arabica (COAR) saplings. We also evaluated leaf thermotolerance and whole plant responses to heat stress of seedlings in two populations each of Pinus ponderosa (PIPO) and Pseudotsuga menziesii (PSME) from contrasting climates. Thermotolerance of detached leaves/needles was evaluated using chlorophyll fluorescence (FV/FM, FO) and electrolyte leakage. After exposure of whole plants to a simulated heat wave in a growth chamber, we monitored FV/FM, photosynthesis (A), stomatal conductance (gs), non-structural carbohydrates (NSCs), and carbon isotope ratios (δ13C). In COAR, thermotolerance and rate of recovery increased with leaf age. Following heat treatment, reductions in A and gs led to reduced intrinsic water use efficiency (iWUE) and increased leaf temperatures. NSC results suggested that starch was converted to sugars for recovery from heat stress and phloem transport was inhibited. Plants failed to flower in both heat stress duration treatments. In PIPO and PSME, heat treatment induced significant reductions in FV/FM and A. NSC results suggested that starch was converted to glucose + fructose to aid recovery from heat-induced damage. Populations from drier sites had greater δ13C values than those from wetter sites, consistent with higher iWUE of populations from drier climates. Thermotolerance and heat stress responses appeared to be phenotypically plastic and representative of the environment in which plants were grown, whereas iWUE appeared to reflect ecotypic differentiation and the climate of origin. Considering leaf age, heat stress duration, methodology, functional type, and climate of origin improves our understanding of physiological responses to short term heat stress.

Carbon dioxide enrichment does not reduce leaf longevity or alter accumulation of carbon reserves in the woodland spring ephemeral Erythronium americanum.

PubMed

Gutjahr, Sylvain; Lapointe, Line

2008-11-01

Woodland spring ephemerals exhibit a relatively short epigeous growth period prior to canopy closure. However, it has been suggested that leaf senescence is induced by a reduction in the carbohydrate sink demand, rather than by changes in light availability. To ascertain whether a potentially higher net carbon (C) assimilation rate could shorten leaf lifespan due to an accelerated rate of storage, Erythronium americanum plants were grown under ambient (400 ppm) and elevated (1100 ppm) CO2 concentrations. During this growth-chamber experiment, plant biomass, bulb starch concentration and cell size, leaf phenology, gas exchange rates and nutrient concentrations were monitored. Plants grown at 1100 ppm CO2 had greater net C assimilation rates than those grown at 400 ppm CO2. However, plant size, final bulb mass, bulb filling rate and timing of leaf senescence did not differ. Erythronium americanum fixed more C under elevated than under ambient CO2 conditions, but produced plants of similar size. The similar bulb growth rates under both CO2 concentrations suggest that the bulb filling rate is dependant on bulb cell elongation rate, rather than on C availability. Elevated CO2 stimulated leaf and bulb respiratory rates; this might reduce feed-back inhibition of photosynthesis and avoid inducing premature leaf senescence.

Differences in Forage-Acquisition and Fungal Enzyme Activity Contribute to Niche Segregation in Panamanian Leaf-Cutting Ants

PubMed Central

Kooij, Pepijn W.; Liberti, Joanito; Giampoudakis, Konstantinos; Schiøtt, Morten; Boomsma, Jacobus J.

2014-01-01

The genera Atta and Acromyrmex are often grouped as leaf-cutting ants for pest management assessments and ecological surveys, although their mature colony sizes and foraging niches may differ substantially. Few studies have addressed such interspecific differences at the same site, which prompted us to conduct a comparative study across six sympatric leaf-cutting ant species in Central Panama. We show that foraging rates during the transition between dry and wet season differ about 60 fold between genera, but are relatively constant across species within genera. These differences appear to match overall differences in colony size, especially when Atta workers that return to their nests without leaves are assumed to carry liquid food. We confirm that Panamanian Atta specialize primarily on tree-leaves whereas Acromyrmex focus on collecting flowers and herbal leaves and that species within genera are similar in these overall foraging strategies. Species within genera tended to be spaced out over the three habitat categories that we distinguished (forest, forest edge, open grassland), but each of these habitats normally had only a single predominant Atta and Acromyrmex species. We measured activities of twelve fungus garden decomposition enzymes, belonging to the amylases, cellulases, hemicellulases, pectinases and proteinases, and show that average enzyme activity per unit of fungal mass in Atta gardens is lower than in Acromyrmex gardens. Expression profiles of fungal enzymes in Atta also appeared to be more specialized than in Acromyrmex, possibly reflecting variation in forage material. Our results suggest that species- and genus-level identities of leaf-cutting ants and habitat-specific foraging profiles may give predictable differences in the expression of fungal genes coding for decomposition enzymes. PMID:24718261

Geographical Variation in the Terpene Composition of the Leaf Oil of Douglas Fir,

DTIC Science & Technology

The two forms of Douglas fir, Pseudotsuga menziesii var. menziesii and var. glauca, differ quite considerably with regard to the monoterpenes of...their leaf oils. Several chemical races, differing quantitatively in certain monoterpenes , appear to exist in each variety and the leaf oil composition seems to be particularly useful in classifying intermediate forms. (Author)

The Role of Native Tree Species on Leaf Breakdown Dynamics of the Invasive Tree of Heaven ( Ailanthus altissima) in an Urban Stream

NASA Astrophysics Data System (ADS)

Swan, C.; Healey, B.

2005-05-01

Anthropogenic disturbance of ecosystem processes is increasingly being explored in urban settings. One profound impact is the striking increase in the distribution of invasive plant species. For example, Tree of Heaven (Ailanthus altissima, TOH), introduced into the U.S. from Asia in 1784, is a successful colonist of recently deforested habitats. As a result, remnant patches in urban ecosystems have become overrun with this tree species, excluding native species via fast growth and allelopathy. While suffering from human-induced degradation, urban streams still support food webs that function to process riparian-derived organic matter (e.g., leaves, wood). The purpose of this study was to (1) estimate leaf litter breakdown of native tree leaves and those of TOH in an urban stream, (2) study the detritivore feeding rate of the same leaf species, and (3) determine if increasing native species richness of leaf litter can alter breakdown of TOH leaves. Field manipulations of leaf pack composition were done in a highly urbanized stream (>30% upstream urban land use) in Baltimore County, Maryland, USA. This was complimented by a series of laboratory feeding experiments employing similar leaf treatments and local shredding invertebrate taxa. Breakdown of TOH alone was extremely rapid, significantly exceeding that of all native tree species employed. Furthermore, mixing TOH with native tree species, red maple and white oak, substantially reduced TOH decay compared to decay of TOH alone. However, supporting laboratory studies showed that TOH was a preferred resource by shredding invertebrates over all native species. Subsequent analysis of the structural integrity of all leaf species revealed that TOH was the least resistant to force, possibly explaining the counterintuitive decrease of TOH decay in mixtures. We interpret this as meaning the stream invertebrates, while preferring to consume TOH, appeared not to influence TOH decay in mixtures with native species. Instead, the relatively tougher nature of native species appeared to slow TOH breakdown by armoring the invasive from the highly-variable flow regime characteristic of urban streams. Therefore, the presence of native tree species in urban riparian zones may be critical to how invasive trees, like TOH, could alter carbon flux in urban streams.

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.

Silicon-Mediated Resistance in a Susceptible Rice Variety to the Rice Leaf Folder, Cnaphalocrocis medinalis Guenée (Lepidoptera: Pyralidae)

PubMed Central

Han, Yongqiang; Lei, Wenbin; Wen, Lizhang; Hou, Maolin

2015-01-01

The rice leaf folder, Cnaphalocrocis medinalis (Guenée), is one of the most destructive rice pests in Asian countries. Rice varieties resistant to the rice leaf folder are generally characterized by high silicon content. In this study, silicon amendment, at 0.16 and 0.32 g Si/kg soil, enhanced resistance of a susceptible rice variety to the rice leaf folder. Silicon addition to rice plants at both the low and high rates significantly extended larval development and reduced larval survival rate and pupation rate in the rice leaf folder. When applied at the high rate, silicon amendment reduced third-instars’ weight gain and pupal weight. Altogether, intrinsic rate of increase, finite rate of increase and net reproduction rate of the rice leaf folder population were all reduced at both the low and high silicon addition rates. Although the third instars consumed more in silicon-amended treatments, C:N ratio in rice leaves was significantly increased and food conversion efficiencies were reduced due to increased silicon concentration in rice leaves. Our results indicate that reduced food quality and food conversion efficiencies resulted from silicon addition account for the enhanced resistance in the susceptible rice variety to the rice leaf folder. PMID:25837635

Inside out: efflux of carbon dioxide from leaves represents more than leaf metabolism.

PubMed

Stutz, Samantha S; Anderson, Jeremiah; Zulick, Rachael; Hanson, David T

2017-05-17

High concentrations of inorganic carbon in the xylem, produced from root, stem, and branch respiration, travel via the transpiration stream and eventually exit the plant through distant tissues as CO2. Unlike previous studies that focused on the efflux of CO2 from roots and woody tissues, we focus on efflux from leaves and the potential effect on leaf respiration measurements. We labeled transported inorganic carbon, spanning reported xylem concentrations, with 13C and then manipulated transpiration rates in the dark in order to vary the rates of inorganic carbon supply to cut leaves from Brassica napus and Populus deltoides. We used tunable diode laser absorbance spectroscopy to directly measure the rate of gross 13CO2 efflux, derived from inorganic carbon supplied from outside of the leaf, relative to gross 12CO2 efflux generated from leaf cells. These experiemnts showed that 13CO2 efflux was dependent upon the rate of inorganic carbon supply to the leaf and the rate of transpiration. Our data show that the gross leaf efflux of xylem-transported CO2 is likely small in the dark when rates of transpiration are low. However, gross leaf efflux of xylem-transported CO2 could approach half the rate of leaf respiration in the light when transpiration rates and branch inorganic carbon concentrations are high, irrespective of the grossly different petiole morphologies in our experiment. © The Author 2017. Published by Oxford University Press on behalf of the Society for Experimental Biology.

Does leaf chemistry differentially affect breakdown in tropical vs temperate streams? Importance of standardized analytical techniques to measure leaf chemistry

Treesearch

Marcelo Ard& #243; n; Catherine M. Pringle; Susan L. Eggert

2009-01-01

Comparisons of the effects of leaf litter chemistry on leaf breakdown rates in tropical vs temperate streams are hindered by incompatibility among studies and across sites of analytical methods used to measure leaf chemistry. We used standardized analytical techniques to measure chemistry and breakdown rate of leaves from common riparian tree species at 2 sites, 1...

How do leaf veins influence the worldwide leaf economic spectrum? Review and synthesis.

PubMed

Sack, Lawren; Scoffoni, Christine; John, Grace P; Poorter, Hendrik; Mason, Chase M; Mendez-Alonzo, Rodrigo; Donovan, Lisa A

2013-10-01

Leaf vein traits are implicated in the determination of gas exchange rates and plant performance. These traits are increasingly considered as causal factors affecting the 'leaf economic spectrum' (LES), which includes the light-saturated rate of photosynthesis, dark respiration, foliar nitrogen concentration, leaf dry mass per area (LMA) and leaf longevity. This article reviews the support for two contrasting hypotheses regarding a key vein trait, vein length per unit leaf area (VLA). Recently, Blonder et al. (2011, 2013) proposed that vein traits, including VLA, can be described as the 'origin' of the LES by structurally determining LMA and leaf thickness, and thereby vein traits would predict LES traits according to specific equations. Careful re-examination of leaf anatomy, published datasets, and a newly compiled global database for diverse species did not support the 'vein origin' hypothesis, and moreover showed that the apparent power of those equations to predict LES traits arose from circularity. This review provides a 'flux trait network' hypothesis for the effects of vein traits on the LES and on plant performance, based on a synthesis of the previous literature. According to this hypothesis, VLA, while virtually independent of LMA, strongly influences hydraulic conductance, and thus stomatal conductance and photosynthetic rate. We also review (i) the specific physiological roles of VLA; (ii) the role of leaf major veins in influencing LES traits; and (iii) the role of VLA in determining photosynthetic rate per leaf dry mass and plant relative growth rate. A clear understanding of leaf vein traits provides a new perspective on plant function independently of the LES and can enhance the ability to explain and predict whole plant performance under dynamic conditions, with applications towards breeding improved crop varieties.

Difference in leaf water use efficiency/photosynthetic nitrogen use efficiency of Bt-cotton and its conventional peer.

PubMed

Guo, Ruqing; Sun, Shucun; Liu, Biao

2016-09-15

This study is to test the effects of Bt gene introduction on the foliar water/nitrogen use efficiency in cotton. We measured leaf stomatal conductance, photosynthetic rate, and transpiration rate under light saturation condition at different stages of a conventional cultivar (zhongmian no. 16) and its counterpart Bt cultivar (zhongmian no. 30) that were cultured on three levels of fertilization, based on which leaf instantaneous water use efficiency was derived. Leaf nitrogen concentration was measured to calculate leaf photosynthetic nitrogen use efficiency, and leaf δ(13)C was used to characterize long term water use efficiency. Bt cultivar was found to have lower stomatal conductance, net photosynthetic rates and transpiration rates, but higher instantaneous and long time water use efficiency. In addition, foliar nitrogen concentration was found to be higher but net photosynthetic rate was lower in the mature leaves of Bt cultivar, which led to lower photosynthetic nitrogen use efficiency. This might result from the significant decrease of photosynthetic rate due to the decrease of stomatal conductance. In conclusion, our findings show that the introduction of Bt gene should significantly increase foliar water use efficiency but decrease leaf nitrogen use efficiency in cotton under no selective pressure.

[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.

Phylogenetic ecology of leaf surface traits in the milkweeds (Asclepias spp.): chemistry, ecophysiology, and insect behavior.

PubMed

Agrawal, Anurag A; Fishbein, Mark; Jetter, Reinhard; Salminen, Juha-Pekka; Goldstein, Jessica B; Freitag, Amy E; Sparks, Jed P

2009-08-01

The leaf surface is the contact point between plants and the environment and plays a crucial role in mediating biotic and abiotic interactions. Here, we took a phylogenetic approach to investigate the function, trade-offs, and evolution of leaf surface traits in the milkweeds (Asclepias). Across 47 species, we found trichome densities of up to 3000 trichomes cm(-2) and epicuticular wax crystals (glaucousness) on 10 species. Glaucous species had a characteristic wax composition dominated by very-long-chain aldehydes. The ancestor of the milkweeds was probably a glaucous species, from which there have been several independent origins of glabrous and pubescent types. Trichomes and wax crystals showed negatively correlated evolution, with both surface types showing an affinity for arid habitats. Pubescent and glaucous milkweeds had a higher maximum photosynthetic rate and lower stomatal density than glabrous species. Pubescent and glaucous leaf surfaces impeded settling behavior of monarch caterpillars and aphids compared with glabrous species, although surface types did not show consistent differentiation in secondary chemistry. We hypothesize that pubescence and glaucousness have evolved as alternative mechanisms with similar functions. The glaucous type, however, appears to be ancestral, lost repeatedly, and never regained; we propose that trichomes are a more evolutionarily titratable strategy.

Phloem Transport Velocity Varies over Time and among Vascular Bundles during Early Cucumber Seedling Development1[C][W][OPEN

PubMed Central

Savage, Jessica A.; Zwieniecki, Maciej A.; Holbrook, N. Michele

2013-01-01

We use a novel dye-tracing technique to measure in vivo phloem transport velocity in cucumber (Cucumis sativus) plants during early seedling development. We focus on seedlings because of their importance in plant establishment and because they provide a simple source and sink model of phloem transport. The dye-tracing method uses a photodiode to track the movement of a bleach front of fluorescent dye traveling in the phloem from the cotyledons (source) to the roots (sink). During early seedling development, phloem transport velocity in this direction can change 2-fold depending on vascular connectivity and the number of actively growing sinks. Prior to leaf expansion, vascular bundles attached to the first developing leaf demonstrate a decline in basipetal phloem transport that can be alleviated by the leaf’s removal. At this stage, seedlings appear carbon limited and phloem transport velocity is correlated with cotyledon area, a pattern that is apparent both during cotyledon expansion and after source area manipulation. When the first leaf transitions to a carbon source, seedling growth rate increases and basipetal phloem transport velocity becomes more stable. Because bundles appear to operate autonomously, transport velocity can differ among vascular bundles. Together, these results demonstrate the dynamic and heterogeneous nature of phloem transport and underline the need for a better understanding of how changes in phloem physiology impact growth and allocation at this critical stage of development. PMID:24072581

Population dynamics of the rubber plantation litter beetle Luprops tristis, in relation to annual cycle of foliage phenology of its host, the para rubber tree, Hevea brasiliensis.

PubMed

Sabu, Thomas K; Vinod, K V

2009-01-01

The population dynamics of the rubber plantation litter beetle, Luprops tristis Fabricius 1801 (Coleoptera: Tenebrionidae) was assessed in relation to the phenology of leaf shedding and defoliation pattern of para rubber trees, Hevea brasiliensis Müll. Arg (Malpighiales: Euphorbiaceae), during a two year study period. The abundance of adults, larvae and pupae per 1m(2) of litter sample was recorded. Post dormancy beetles appeared in leaf litter following annual leaf shedding, whereas larvae, pupae and teneral adults were present after leaf flush. No stages were recorded from plantations following the summer rains until the annual litter fall in the next season. Parental adults peaked at the time of leaf sprouting and tender leaf fall. Larvae and teneral adults peaked at the time of premature fall of green leaves and flowers. Teneral adults of six age classes were recorded and all entered dormancy irrespective of the feeding time available to each age class. Females outnumbered males in the parent generation, while the sex ratio of new generation adults was not biased towards either sex. The phenological stages of rubber trees included leaf fall in late December and early January, leaf sprouting and new leaf production in January and flowering in February. All feeding stages of L. tristis peaked in abundance when premature leaves are most abundant in the leaf litter. Prediction of the timing of appearance of various developmental stages of L. tristis in plantations, invasion into buildings and intensity of population build up in rubber belts is possible by tracking the phenology of leaf fall in rubber plantations, time of return of post dormancy adults and the onset of summer rainfall. Perfect synchrony was recorded between the field return of parental adults with annual leaf shedding, the oviposition phase of parental adults with tender leaf fall at the time of leaf sprouting, and larval and teneral adult stages with premature fall of leaves. Premature leaf availability is suggested as contributing to the reproductive efficiency of parental adults, the survival of early developmental stages and of new generation adults during dormancy.

Population Dynamics of the Rubber Plantation Litter Beetle Luprops tristis, in Relation to Annual Cycle of Foliage Phenology of Its Host, the Para Rubber Tree, Hevea brasiliensis

PubMed Central

Sabu, Thomas K.; Vinod, K.V.

2009-01-01

The population dynamics of the rubber plantation litter beetle, Luprops tristis Fabricius 1801 (Coleoptera: Tenebrionidae) was assessed in relation to the phenology of leaf shedding and defoliation pattern of para rubber trees, Hevea brasiliensis Müll. Arg (Malpighiales: Euphorbiaceae), during a two year study period. The abundance of adults, larvae and pupae per 1m2 of litter sample was recorded. Post dormancy beetles appeared in leaf litter following annual leaf shedding, whereas larvae, pupae and teneral adults were present after leaf flush. No stages were recorded from plantations following the summer rains until the annual litter fall in the next season. Parental adults peaked at the time of leaf sprouting and tender leaf fall. Larvae and teneral adults peaked at the time of premature fall of green leaves and flowers. Teneral adults of six age classes were recorded and all entered dormancy irrespective of the feeding time available to each age class. Females outnumbered males in the parent generation, while the sex ratio of new generation adults was not biased towards either sex. The phenological stages of rubber trees included leaf fall in late December and early January, leaf sprouting and new leaf production in January and flowering in February. All feeding stages of L. tristis peaked in abundance when premature leaves are most abundant in the leaf litter. Prediction of the timing of appearance of various developmental stages of L. tristis in plantations, invasion into buildings and intensity of population build up in rubber belts is possible by tracking the phenology of leaf fall in rubber plantations, time of return of post dormancy adults and the onset of summer rainfall. Perfect synchrony was recorded between the field return of parental adults with annual leaf shedding, the oviposition phase of parental adults with tender leaf fall at the time of leaf sprouting, and larval and teneral adult stages with premature fall of leaves. Premature leaf availability is suggested as contributing to the reproductive efficiency of parental adults, the survival of early developmental stages and of new generation adults during dormancy. PMID:20050775

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

Lincoln, D.E.

Assay procedures for analysis of four groups of allelochemicals in Artemisia tridentata, big sagebrush, were established. Growth of Artemisia under high and low light at three CO/sub 2/ levels demonstrated that this species also undegoes a ''dilution'' of the leaf nitrogen content and is useful as test species for herbivory response to CO/sub 2/ induced effects. The initiial experiment also showed that high irradiance is a necessary growth condition. Plants from a single population of A. Tridentata were grown at the Duke Phytotron in three CO/sub 2/ regimed and fed to two species of grasshoppers. Sagabrush plants grew more andmore » had lower leaf nitrogen contents as CO/sub 2/ concentration increased. However, the plants had on average lowere leaf carbon as well as lower leaf niitrogen contents with elevated CO/sub 2/. The source of the lower leaf nutritional value does not appear to be solely an increase in carbon content. Grasshopper consumption was greater on leaves from elevated future and from reduced historical CO/sub 2/ regimes, compared to the current concentration. The increased consumption of leaves from elevated CO/sub 2/ is in agreement with previous results. Grasshopper consumption was significantly related to leaf allelochemical content, but not to leaf nitrogen content. The consumption difference among CO/sub 2/ regimes appeared to result from allelochemical differences, which in turn may result from genetic variation or from CO/sub 2/ treatments. 17 refs., 2 figs., 4 tabs.« less

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.

Water relation, leaf gas exchange and chlorophyll a fluorescence imaging of soybean leaves infected with Colletotrichum truncatum.

PubMed

Dias, Carla Silva; Araujo, Leonardo; Alves Chaves, Joicy Aparecida; DaMatta, Fábio M; Rodrigues, Fabrício A

2018-06-01

Considering the potential of anthracnose to decrease soybean yield and the need to gain more information regarding its effect on soybean physiology, the present study performed an in-depth analysis of the photosynthetic performance of soybean leaflets challenged with Colletotrichum truncatum by combining chlorophyll a fluorescence images with gas-exchange measurements and photosynthetic pigment pools. There were no significant differences between non-inoculated and inoculated plants in leaf water potential, apparent hydraulic conductance, net CO 2 assimilation rate, stomatal conductance to water vapor and transpiration rate. For internal CO 2 concentration, significant difference between non-inoculated and inoculated plants occurred only at 36 h after inoculation. Reductions in the values of the chlorophyll a fluorescence parameters [initial fluorescence (F 0 ), maximal fluorescence (F m ), maximal photosystem II quantum yield (F v /F m ), quantum yield of regulated energy dissipation (Y(NPQ))] and increases in effective PS II quantum yield (Y(II)), quantum yield of non-regulated energy dissipation Y(NO) and photochemical quenching coefficient (q P ) were noticed on the necrotic vein tissue in contrast to the surrounding leaf tissue. It appears that the impact of the infection by C. truncatum on the photosynthetic performance of the leaflets was minimal considering the preference of the fungus to colonize the veins. Copyright © 2018 Elsevier Masson SAS. All rights reserved.

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

Leaf Relative Water Content Estimated from Leaf Reflectance and Transmittance

NASA Technical Reports Server (NTRS)

Vanderbilt, Vern; Daughtry, Craig; Dahlgren, Robert

2016-01-01

Remotely sensing the water status of plants and the water content of canopies remain long term goals of remote sensing research. In the research we report here, we used optical polarization techniques to monitor the light reflected from the leaf interior, R, as well as the leaf transmittance, T, as the relative water content (RWC) of corn (Zea mays) leaves decreased. Our results show that R and T both change nonlinearly. The result show that the nonlinearities cancel in the ratio R/T, which appears linearly related to RWC for RWC less than 90%. The results suggest that potentially leaf water status and perhaps even canopy water status could be monitored starting from leaf and canopy optical measurements.

Carbon and nitrogen balance of leaf-eating sesarmid crabs ( Neoepisesarma versicolor) offered different food sources

NASA Astrophysics Data System (ADS)

Thongtham, Nalinee; Kristensen, Erik

2005-10-01

Carbon and nitrogen budgets for the leaf-eating crab, Neoepisesarma versicolor, were established for individuals living on pure leaf diets. Crabs were fed fresh (green), senescent (yellow) and partly degraded (brown) leaves of the mangrove tree Rhizophora apiculata. Ingestion, egestion and metabolic loss of carbon and nitrogen were determined from laboratory experiments. In addition, bacterial abundance in various compartments of the crabs' digestive tract was enumerated after dissection of live individuals. Ingestion and egestion rates (in terms of dry weight) were highest, while the assimilation efficiency was poorest for crabs fed on brown leaves. The low assimilation efficiency was more than counteracted by the high ingestion rate providing more carbon for growth than for crabs fed green and yellow leaves. In any case, the results show that all types of leaves can provide adequate carbon while nitrogen was insufficient to support both maintenance (yellow leaves) and growth (green, yellow and brown leaves). Leaf-eating crabs must therefore obtain supplementary nitrogen by other means in order to meet their nitrogen requirement. Three hypotheses were evaluated: (1) crabs supplement their diet with bacteria and benthic microalgae by ingesting own faeces and/or selective grazing at the sediment surface; (2) assimilation of symbiotic nitrogen-fixing bacteria in the crabs' own intestinal system; and (3) nitrogen storage following occasional feeding on animal tissues (e.g. meiofauna and carcasses). It appears that hypothesis 1 is of limited importance for N. versicolor since faeces and sediment can only supply a minor fraction of the missing nitrogen due to physical constraints on the amount of material the crabs can consume. Hypothesis 2 can be ruled out because tests showed no nitrogen fixation activity in the intestinal system of N. versicolor. It is therefore likely that leaf-eating crabs provide most of their nitrogen requirement from intracellular deposits following occasionally ingestion of animal tissue (hypothesis 3).

Can Meristematic Activity Determine Variation in Leaf Size and Elongation Rate among Four Poa Species? A Kinematic Study1

PubMed Central

Fiorani, Fabio; Beemster, Gerrit T.S.; Bultynck, Lieve; Lambers, Hans

2000-01-01

We studied inherent variation in final leaf size among four Poa spp. that live at different elevations. The average final length of leaf 7 of the main stem of the smallest species (Poa alpina) was only one-half that of the largest species (Poa trivialis); it was correlated with leaf elongation rate, but not with the duration of leaf elongation. A faster rate of leaf elongation rate was associated with (a) larger size of the zone of cell expansion, and (b) faster rates of cell production (per cell file) in the meristem, which in turn were due to greater numbers of dividing cells, whereas average cell division rates were very similar for all species (except Poa annua). Also we found that the proliferative fraction equaled 1 throughout the meristem in all species. It was remarkable that rates of cell expansion tended to be somewhat higher in the species with slower growing leaves. We discuss the results by comparing the spatial and material viewpoints, which lead to different interpretations of the role of cell division. Although the presented data do not strictly prove it, they strongly suggest a regulatory role for cell division in determining differences in growth rate among the present four Poa spp. PMID:11027732

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.

Responses of Woody Plant Functional Traits to Nitrogen Addition: A Meta-Analysis of Leaf Economics, Gas Exchange, and Hydraulic Traits.

PubMed

Zhang, Hongxia; Li, Weibin; Adams, Henry D; Wang, Anzhi; Wu, Jiabing; Jin, Changjie; Guan, Dexin; Yuan, Fenghui

2018-01-01

Atmospheric nitrogen (N) deposition has been found to significantly affect plant growth and physiological performance in terrestrial ecosystems. Many individual studies have investigated how N addition influences plant functional traits, however these investigations have usually been limited to a single species, and thereby do not allow derivation of general patterns or underlying mechanisms. We synthesized data from 56 papers and conducted a meta-analysis to assess the general responses of 15 variables related to leaf economics, gas exchange, and hydraulic traits to N addition among 61 woody plant species, primarily from temperate and subtropical regions. Results showed that under N addition, leaf area index (+10.3%), foliar N content (+7.3%), intrinsic water-use efficiency (+3.1%) and net photosynthetic rate (+16.1%) significantly increased, while specific leaf area, stomatal conductance, and transpiration rate did not change. For plant hydraulics, N addition significantly increased vessel diameter (+7.0%), hydraulic conductance in stems/shoots (+6.7%), and water potential corresponding to 50% loss of hydraulic conductivity ( P 50 , +21.5%; i.e., P 50 became less negative), while water potential in leaves (-6.7%) decreased (became more negative). N addition had little effect on vessel density, hydraulic conductance in leaves and roots, or water potential in stems/shoots. N addition had greater effects on gymnosperms than angiosperms and ammonium nitrate fertilization had larger effects than fertilization with urea, and high levels of N addition affected more traits than low levels. Our results demonstrate that N addition has coupled effects on both carbon and water dynamics of woody plants. Increased leaf N, likely fixed in photosynthetic enzymes and pigments leads to higher photosynthesis and water use efficiency, which may increase leaf growth, as reflected in LAI results. These changes appear to have downstream effects on hydraulic function through increases in vessel diameter, which leads to higher hydraulic conductance, but lower water potential and increased vulnerability to embolism. Overall, our results suggest that N addition will shift plant function along a tradeoff between C and hydraulic economies by enhancing C uptake while simultaneously increasing the risk of hydraulic dysfunction.

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.

Effects of cadmium and resource quality on freshwater detritus processing chains: a microcosm approach with two insect species.

PubMed

Campos, Diana; Alves, Artur; Lemos, Marco F L; Correia, António; Soares, Amadeu M V M; Pestana, João L T

2014-07-01

Detritus processing is vital for freshwater ecosystems that depend on the leaf litter from riparian vegetation and is mediated by microorganisms and aquatic invertebrates. Shredder invertebrates transform coarse particulate organic matter into fine particulate organic matter used as food by collector species. Direct and indirect effects of contaminants can impair detritus processing and thus affect the functioning of these ecosystems. Here, we assessed the combined effects of a toxic metal (cadmium) and resource quality (leaf species) on detritus processing and shredder-collector interactions. We considered two types of leaves, alder and eucalyptus that were microbially conditioned under different Cd concentrations in the laboratory. The microbial communities present on leaves were analyzed by Denaturing Gradient Gel Electrophoresis (DGGE), and we also measured microbial respiration rates. Sericostoma vittatum (a caddisfly shredder) and Chironomus riparius (a midge collector) were also exposed to Cd and allowed to consume the corresponding alder or eucalyptus leaves. We evaluated C. riparius growth and leaf mass loss in multispecies microcosms. Cadmium exposure affected leaf conditioning and fungal diversity on both leaf species, as assessed by DGGE. Cadmium exposure also affected the mass loss of alder leaves by reductions in detritivore feeding, and impaired C. riparius growth. Chironomus riparius consumed alder leaf discs in the absence of shredders, but S. vittatum appear to promote C. riparius growth in treatments containing eucalyptus. These results show that indirect effects of contaminants along detritus-processing chains can occur through effects on shredder-collector interactions such as facilitation but they also depend on the nutritional quality of detritus and on sensitivity and feeding plasticity of detritivore species.

Reducing cell wall feruloylation by expression of a fungal ferulic acid esterase in Festuca arundinacea modifies plant growth, leaf morphology and the turnover of cell wall arabinoxylans

PubMed Central

Iyer, Prashanti R.; Buanafina, M. Fernanda; Shearer, Erica A.

2017-01-01

A feature of cell wall arabinoxylan in grasses is the presence of ferulic acid which upon oxidative coupling by the action of peroxidases forms diferuloyl bridges between formerly separated arabinoxylans. Ferulate cross-linking is suspected of playing various roles in different plant processes. Here we investigate the role of cell wall feruloyaltion in two major processes, that of leaf growth and the turnover of cell wall arabinoxylans on leaf senescence in tall fescue using plants in which the level of cell wall ferulates has been reduced by targeted expression of the Aspergillus niger ferulic acid esterase A (FAEA) to the apoplast or Golgi. Analysis of FAE expressing plants showed that all the lines had shorter and narrower leaves compared to control, which may be a consequence of the overall growth rate being lower and occurring earlier in FAE expressing leaves than in controls. Furthermore, the final length of epidermal cells was shorter than controls, indicating that their expansion was curtailed earlier than in control leaves. This may be due to the observations that the deposition of both ether and ester linked monomeric hydroxycinnamic acids and ferulate dimerization stopped earlier in FAE expressing leaves but at a lower level than controls, and hydroxycinnamic acid deposition started to slow down when peroxidase levels increased. It would appear therefore that one of the possible mechanisms for controlling overall leaf morphology such as leaf length and width in grasses, where leaf morphology is highly variable between species, may be the timing of hydroxycinnamic acid deposition in the expanding cell walls as they emerge from cell division into the elongation zone, controlled partially by the onset of peroxidase activity in this region. PMID:28934356

Ethylene Emission and Responsiveness to Applied Ethylene Vary among Poa Species That Inherently Differ in Leaf Elongation Rates1

PubMed Central

Fiorani, Fabio; Bögemann, Gerard M.; Visser, Eric J.W.; Lambers, Hans; Voesenek, Laurentius A.C.J.

2002-01-01

A plant's ability to produce and respond to ethylene is essential for its vegetative growth. We studied whole-shoot ethylene emission and leaf growth responses to applied ethylene in four Poa spp. that differ inherently in leaf elongation rate and whole-plant relative growth rate. Compared with the fast-growing Poa annua and Poa trivialis, the shoots of the slow-growing species Poa alpina and Poa compressa emitted daily 30% to 50% less ethylene, and their leaf elongation rate was more strongly inhibited when ethylene concentration was increased up to 1 μL L−1. To our surprise, however, low ethylene concentrations (0.02–0.03 μL L−1) promoted leaf growth in the two slow-growing species; at the same concentrations, leaf elongation rate of the two fast-growing species was only slightly inhibited. All responses were observed within 20 min after ethylene applications. Although ethylene generally inhibits growth, our results show that in some species, it may actually stimulate growth. Moreover, in the two slow-growing Poa spp., both growth stimulation and inhibition occurred in a narrow ethylene concentration range, and this effect was associated with a much lower ethylene emission. These findings suggest that the regulation of ethylene production rates and perception of the gas may be more crucial during leaf expansion of these species under non-stressful conditions and that endogenous ethylene concentrations are not large enough to saturate leaf growth responses. In the two fast-growing species, a comparatively higher ethylene endogenous concentration may conversely be present and sufficiently high to saturate leaf elongation responses, invariably leading to growth inhibition. PMID:12114591

Effects of two boron sources each applied at three rates to the strawberry cv. midway on soil and leaf boron levels and fruit yields

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

Blatt, C.R.

1982-01-01

Preplant applications of Borate -65 at 0.56, 1.12 and 2.24 kg B/ha were reflected in significant increases in soil and leaf B levels up to one year following boron application. After 2 cropping seasons soil B level did not reflect rate of applied B and Solubor was applied broadcast at 1.12, 2.24 and 4.48 kg B/ha in the spring of the 3rd cropping season. Soil and leaf B levels and leaf marginal necrosis increased compared with control plots at all rates of applied B at full bloom in the 3rd cropping season. Rate of applied B was reflected in significantmore » soil and leaf B increases one year following application. Fruit yields through four cropping seasons were not affected by any source of rate of applied B. A soil B range of 0.15-0.25 ppM and a leaf B range of 20-30 ppm will give optimum crop response from the Midway strawberry.« less

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...

Effect of Solar Ultraviolet-B Radiation during Springtime Ozone Depletion on Photosynthesis and Biomass Production of Antarctic Vascular Plants1

PubMed Central

Xiong, Fusheng S.; Day, Thomas A.

2001-01-01

We assessed the influence of springtime solar UV-B radiation that was naturally enhanced during several days due to ozone depletion on biomass production and photosynthesis of vascular plants along the Antarctic Peninsula. Naturally growing plants of Colobanthus quitensis (Kunth) Bartl. and Deschampsia antarctica Desv. were potted and grown under filters that absorbed or transmitted most solar UV-B. Plants exposed to solar UV-B from mid-October to early January produced 11% to 22% less total, as well as above ground biomass, and 24% to 31% less total leaf area. These growth reductions did not appear to be associated with reductions in photosynthesis per se: Although rates of photosynthetic O2 evolution were reduced on a chlorophyll and a dry-mass basis, on a leaf area basis they were not affected by UV-B exposure. Leaves on plants exposed to UV-B were denser, probably thicker, and had higher concentrations of photosynthetic and UV-B absorbing pigments. We suspect that the development of thicker leaves containing more photosynthetic and screening pigments allowed these plants to maintain their photosynthetic rates per unit leaf area. Exposure to UV-B led to reductions in quantum yield of photosystem II, based on fluorescence measurements of adaxial leaf surfaces, and we suspect that UV-B impaired photosynthesis in the upper mesophyll of leaves. Because the ratio of variable to maximal fluorescence, as well as the initial slope of the photosynthetic light response, were unaffected by UV-B exposure, we suggest that impairments in photosynthesis in the upper mesophyll were associated with light-independent enzymatic, rather than photosystem II, limitations. PMID:11161031

Effect of solar ultraviolet-B radiation during springtime ozone depletion on photosynthesis and biomass production of Antarctic vascular plants.

PubMed

Xiong, F S; Day, T A

2001-02-01

We assessed the influence of springtime solar UV-B radiation that was naturally enhanced during several days due to ozone depletion on biomass production and photosynthesis of vascular plants along the Antarctic Peninsula. Naturally growing plants of Colobanthus quitensis (Kunth) Bartl. and Deschampsia antarctica Desv. were potted and grown under filters that absorbed or transmitted most solar UV-B. Plants exposed to solar UV-B from mid-October to early January produced 11% to 22% less total, as well as above ground biomass, and 24% to 31% less total leaf area. These growth reductions did not appear to be associated with reductions in photosynthesis per se: Although rates of photosynthetic O(2) evolution were reduced on a chlorophyll and a dry-mass basis, on a leaf area basis they were not affected by UV-B exposure. Leaves on plants exposed to UV-B were denser, probably thicker, and had higher concentrations of photosynthetic and UV-B absorbing pigments. We suspect that the development of thicker leaves containing more photosynthetic and screening pigments allowed these plants to maintain their photosynthetic rates per unit leaf area. Exposure to UV-B led to reductions in quantum yield of photosystem II, based on fluorescence measurements of adaxial leaf surfaces, and we suspect that UV-B impaired photosynthesis in the upper mesophyll of leaves. Because the ratio of variable to maximal fluorescence, as well as the initial slope of the photosynthetic light response, were unaffected by UV-B exposure, we suggest that impairments in photosynthesis in the upper mesophyll were associated with light-independent enzymatic, rather than photosystem II, limitations.

Non-linear direct effects of acid rain on leaf photosynthetic rate of terrestrial plants.

PubMed

Dong, Dan; Du, Enzai; Sun, Zhengzhong; Zeng, Xuetong; de Vries, Wim

2017-12-01

Anthropogenic emissions of acid precursors have enhanced global occurrence of acid rain, especially in East Asia. Acid rain directly suppresses leaf function by eroding surface waxes and cuticle and leaching base cations from mesophyll cells, while the simultaneous foliar uptake of nitrates in rainwater may directly benefit leaf photosynthesis and plant growth, suggesting a non-linear direct effect of acid rain. By synthesizing data from literature on acid rain exposure experiments, we assessed the direct effects of acid rain on leaf photosynthesis across 49 terrestrial plants in China. Our results show a non-linear direct effect of acid rain on leaf photosynthetic rate, including a neutral to positive effect above pH 5.0 and a negative effect below that pH level. The acid rain sensitivity of leaf photosynthesis showed no significant difference between herbs and woody species below pH 5.0, but the impacts above that pH level were strongly different, resulting in a significant increase in leaf photosynthetic rate of woody species and an insignificant effect on herbs. Our analysis also indicates a positive effect of the molar ratio of nitric versus sulfuric acid in the acid solution on leaf photosynthetic rate. These findings imply that rainwater acidity and the composition of acids both affect the response of leaf photosynthesis and therefore result in a non-linear direct effect. Copyright © 2017 Elsevier Ltd. All rights reserved.

Leaf Breakdown in a Tropical Stream

NASA Astrophysics Data System (ADS)

Gonçalves, José Francisco, Jr.; França, Juliana S.; Medeiros, Adriana O.; Rosa, Carlos A.; Callisto, Marcos

2006-05-01

The objectives of this study were to investigate leaf breakdown in two reaches of different magnitudes, one of a 3rd (closed riparian vegetation) order and the other of a 4th (open riparian vegetation) order, in a tropical stream and to assess the colonization of invertebrates and microorganisms during the processing of detritus. We observed that the detritus in a reach of 4th order decomposed 2.4 times faster than the detritus in a reach of 3rd order, in which, we observed that nitrate concentration and water velocity were greater. This study showed that the chemical composition of detritus does not appear to be important in evaluating leaf breakdown. However, it was shown to be important to biological colonization. The invertebrate community appeared not to have been structured by the decomposition process, but instead by the degradative ecological succession process. With regards to biological colonization, we observed that the density of bacteria in the initial stages was more important while fungi appeared more in the intermediate and final stages.

Global variability in leaf respiration in relation to climate and leaf traits

NASA Astrophysics Data System (ADS)

Atkin, Owen K.

2015-04-01

Leaf respiration plays a vital role in regulating ecosystem functioning and the Earth's climate. Because of this, it is imperative that that Earth-system, climate and ecosystem-level models be able to accurately predict variations in rates of leaf respiration. In the field of photosynthesis research, the F/vC/B model has enabled modellers to accurately predict variations in photosynthesis through time and space. By contrast, we lack an equivalent biochemical model to predict variations in leaf respiration. Consequently, we need to rely on phenomenological approaches to model variations in respiration across the Earth's surface. Such approaches require that we develop a thorough understanding of how rates of respiration vary among species and whether global environmental gradients play a role in determining variations in leaf respiration. Dealing with these issues requires that data sets be assembled on rates of leaf respiration in biomes across the Earth's surface. In this talk, I will use a newly-assembled global database on leaf respiration and associated traits (including photosynthesis) to highlight variation in leaf respiration (and the balance between respiration and photosynthesis) across global gradients in growth temperature and aridity.

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.

Seasonal variation of leaf traits in two woody species of an urban park

NASA Astrophysics Data System (ADS)

Kim, H.; Ryu, Y.

2013-12-01

Leaf traits are important for understanding physiology of woody plants. Some leaf traits such as maximum carboxylation rate (Vcamx) and maximum electron transport rate (Jmax) are especially crucial parameters for photosynthesis modelling. In this study, we report leaf traits (leaf mass per unit area, leaf carbon and nitrogen contents and C:N, Vcmax, Jmax) of two species (Zelkova serrata and Prunus yedoensis) in the Seoul Forest Park in 2013. From May to July, Vcmax and Jmax show gradual increase. In contrast, N concentration and C:N show the opposite pattern. Also we find that the ratio of Jmax to Vcmax was 1.05, which is substantially lower than many previous studies. We discuss main factors that control seasonal variation of leaf traits and correlation between Vcmax and Jmax.

Modeling light and temperature effects on leaf emergence in wheat and barley

NASA Technical Reports Server (NTRS)

Volk, T.; Bugbee, B.

1991-01-01

Phenological development affects canopy structure, radiation interception, and dry matter production; most crop simulation models therefore incorporate leaf emergence rate as a basic parameter. A recent study examined leaf emergence rate as a function of temperature and daylength among wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.) cultivars. Leaf emergence rate and phyllochron were modeled as functions of temperature alone, daylength alone, and the interaction between temperature and daylength. The resulting equations contained an unwieldy number of constants. Here we simplify by reducing the constants by > 70%, and show leaf emergence rate as a single response surface with temperature and daylength. In addition, we incorporate the effect of photosynthetic photon flux into the model. Generic fits for wheat and barley show cultivar differences less than +/- 5% for wheat and less than +/- 10% for barley. Barley is more sensitive to daylength changes than wheat for common environmental values of daylength, which may be related to the difference in sensitivity to daylength between spring and winter cultivars. Differences in leaf emergence rate between cultivars can be incorporated into the model by means of a single, nondimensional factor for each cultivar.

Humidity does not appear to trigger leaf out in woody plants

NASA Astrophysics Data System (ADS)

Zipf, Lucy; Primack, Richard B.

2017-12-01

In order to anticipate the ecological impacts of climate change and model changes to forests, it is important to understand the factors controlling spring leaf out. Leaf out phenology in woody trees and shrubs is generally considered to be strongly controlled by a combination of spring warming, winter chilling requirement, and photoperiod. However, researchers have recently suggested that temperature-related air humidity, rather than temperature itself, might be the main trigger of the spring leaf-out of woody plants. Here, we sought to examine the relationship between air humidity and leaf-out across a range of humidities and plant functional groups. We did not find any consistent, measurable effect of high humidity advancing leaf-out in the 15 woody shrubs and trees examined in this study, and we did not see progressive patterns of earlier leaf-out in successively higher humidities. Our results indicate that more work must be done on this topic before researchers can properly determine the effect of humidity on the leafing out process for woody species.

Storage nitrogen co-ordinates leaf expansion and photosynthetic capacity in winter oilseed rape

PubMed Central

Liu, Tao; Ren, Tao; White, Philip J; Cong, Rihuan

2018-01-01

Abstract Storage nitrogen (N) is a buffer pool for maintaining leaf growth and synthesizing photosynthetic proteins, but the dynamics of its forms within the life cycle of a single leaf and how it is influenced by N supply remain poorly understood. A field experiment was conducted to estimate the influence of N supply on leaf growth, photosynthetic characteristics, and N partitioning inthe sixth leaf of winter oilseed rape (Brassica napus L.) from emergence through senescence. Storage N content (Nstore) decreased gradually along with leaf expansion. The relative growth rate based on leaf area (RGRa) was positively correlated with Nstore during leaf expansion. The water-soluble protein form of storage N was the main N source for leaf expansion. After the leaves fully expanded, the net photosynthetic rate (An) followed a linear–plateau response to Nstore, with An stabilizing at the highest value above a threshold and declining below the threshold. Non-protein and SDS (detergent)-soluble protein forms of storage N were the main N sources for maintaining photosynthesis. For the leaf N economy, storage N is used for co-ordinating leaf expansion and photosynthetic capacity. N supply can improve Nstore, thereby promoting leaf growth and biomass. PMID:29669007

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.

Salinity stress inhibits bean leaf expansion by reducing turgor, not wall extensibility

NASA Technical Reports Server (NTRS)

Neumann, P. M.; Van Volkenburgh, E.; Cleland, R. E.

1988-01-01

Treatment of bean (Phaseolus vulgaris L.) seedlings with low levels of salinity (50 or 100 millimolar NaCl) decreased the rate of light-induced leaf cell expansion in the primary leaves over a 3 day period. This decrease could be due to a reduction in one or both of the primary cellular growth parameters: wall extensibility and cell turgor. Wall extensibility was assessed by the Instron technique. Salinity did not decrease extensibility and caused small increases relative to the controls after 72 hours. On the other hand, 50 millimolar NaCl caused a significant reduction in leaf bulk turgor at 24 hours; adaptive decreases in leaf osmotic potential (osmotic adjustment) were more than compensated by parallel decreases in xylem tension potential and the leaf apoplastic solute potential, resulting in a decreased leaf water potential. It is concluded that in bean seedlings, mild salinity initially affects leaf growth rate by a decrease in turgor rather than by a reduction in wall extensibility. Moreover, long-term salinization (10 days) resulted in an apparent mechanical adjustment, i.e. an increase in wall extensibility, which may help counteract reductions in turgor and maintain leaf growth rates.

[Effects of simulated warming on the growth, leaf phenology, and leaf traits of Salix eriostachya in sub-alpine timberline ecotone of western Sichuan, China].

PubMed

Xu, Zhen-feng; Hu, Ting-xing; Zhang, Li; Zhang, Yuan-bin; Xian, Jun-ren; Wang, Kai-yun

2009-01-01

By using open-top chamber (OTC), the effects of simulated warming on the growth, leaf phenology, and leaf traits of Salix eriostachya in sub-alpine timberline ecotone of Western Sichuan were studied. The results showed that comparing with the control, the mean air temperature at 1.2 m above the ground throughout S. eriostachya growth season in OTC increased by 2.9 degrees C, while the soil temperature at the depth of 5 cm only increased by 0.4 degrees C. The temperature increase in OTC made S. eriostachya budding advanced and defoliation postponed obviously, and the leaf life-span longer. The leaf and branch growth rates as well as the specific leaf area in OTC increased obviously, whereas the leaf nitrogen concentration decreased significantly. In OTC, the stomata conductance, net photosynthetic rate, photorespiration, and dark respiration rate of S. eriostachya all exhibited an increasing trend. It was suggested that S. eriostachya had stronger capability to adapt to warming, and, under the background of future global climate change, the elevation of S. eriostachya distribution in the timberline ecotone would be likely to ascend.

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.

Three-dimensional patterns of cell division and expansion throughout the development of Arabidopsis thaliana leaves.

PubMed

Kalve, Shweta; Fotschki, Joanna; Beeckman, Tom; Vissenberg, Kris; Beemster, Gerrit T S

2014-12-01

Variations in size and shape of multicellular organs depend on spatio-temporal regulation of cell division and expansion. Here, cell division and expansion rates were quantified relative to the three spatial axes in the first leaf pair of Arabidopsis thaliana. The results show striking differences in expansion rates: the expansion rate in the petiole is higher than in the leaf blade; expansion rates in the lateral direction are higher than longitudinal rates between 5 and 10 days after stratification, but become equal at later stages of leaf blade development; and anticlinal expansion co-occurs with, but is an order of magnitude slower than periclinal expansion. Anticlinal expansion rates also differed greatly between tissues: the highest rates occurred in the spongy mesophyll and the lowest in the epidermis. Cell division rates were higher and continued for longer in the epidermis compared with the palisade mesophyll, causing a larger increase of palisade than epidermal cell area over the course of leaf development. The cellular dynamics underlying the effect of shading on petiole length and leaf thickness were then investigated. Low light reduced leaf expansion rates, which was partly compensated by increased duration of the growth phase. Inversely, shading enhanced expansion rates in the petiole, so that the blade to petiole ratio was reduced by 50%. Low light reduced leaf thickness by inhibiting anticlinal cell expansion rates. This effect on cell expansion was preceded by an effect on cell division, leading to one less layer of palisade cells. The two effects could be uncoupled by shifting plants to contrasting light conditions immediately after germination. This extended kinematic analysis maps the spatial and temporal heterogeneity of cell division and expansion, providing a framework for further research to understand the molecular regulatory mechanisms involved. © The Author 2014. Published by Oxford University Press on behalf of the Society for Experimental Biology. All rights reserved. For permissions, please email: journals.permissions@oup.com.

Leaf Litter Decomposition as a Functional Assessment of a Natural Stream Channel Design Project

NASA Astrophysics Data System (ADS)

Gentry, A.; Word, D.; Carreiro, M.; Jack, J.

2005-05-01

In October 2003, a 965m reach of Wilson Creek (Bernheim Research Forest, Kentucky, USA) was relocated, and meanders and riffle-pool sequences were restored, providing a unique opportunity to measure the re-establishment of post-restoration stream functions. Leaf litter bags were placed across riffles in the restored reach, in an upstream reference site and in two reference streams. Bags were collected for nine months, and mass loss, N dynamics and fungal ergosterol were measured. Daily mass loss rates in the restored and reference riffles in Wilson Creek were faster (k= -0.00759 and k= -0.00855, respectively) than those of the two reference streams (k= -0.00511 and k= -0.00308). This is equivalent to litter mean residence times of 132 days for the restored reach in Wilson, 117 days in the upstream reference site, and 196 and 325 days for the reference streams. It appears that the decay rate in the restored reach is similar to the upstream portion of Wilson Creek, indicating rapid mass loss recovery in the restored reach. We also determined that same-stream reference sites are important for evaluating the restoration of stream functions, because of high decay rate variation among nearby streams within the same watershed.

Functional traits help predict post-disturbance demography of tropical trees.

PubMed

Flores, Olivier; Hérault, Bruno; Delcamp, Matthieu; Garnier, Éric; Gourlet-Fleury, Sylvie

2014-01-01

How tropical tree species respond to disturbance is a central issue of forest ecology, conservation and resource management. We define a hierarchical model to investigate how functional traits measured in control plots relate to the population change rate and to demographic rates for recruitment and mortality after disturbance by logging operations. Population change and demographic rates were quantified on a 12-year period after disturbance and related to seven functional traits measured in control plots. The model was calibrated using a Bayesian Network approach on 53 species surveyed in permanent forest plots (37.5 ha) at Paracou in French Guiana. The network analysis allowed us to highlight both direct and indirect relationships among predictive variables. Overall, 89% of interspecific variability in the population change rate after disturbance were explained by the two demographic rates, the recruitment rate being the most explicative variable. Three direct drivers explained 45% of the variability in recruitment rates, including leaf phosphorus concentration, with a positive effect, and seed size and wood density with negative effects. Mortality rates were explained by interspecific variability in maximum diameter only (25%). Wood density, leaf nitrogen concentration, maximum diameter and seed size were not explained by variables in the analysis and thus appear as independent drivers of post-disturbance demography. Relationships between functional traits and demographic parameters were consistent with results found in undisturbed forests. Functional traits measured in control conditions can thus help predict the fate of tropical tree species after disturbance. Indirect relationships also suggest how different processes interact to mediate species demographic response.

Control of growth of juvenile leaves of Eucalyptus globulus: effects of leaf age.

PubMed

Metcalfe, J C; Davies, W J; Pereira, J S

1991-12-01

Biophysical variables influencing the expansion of plant cells (yield threshold, cell wall extensibility and turgor) were measured in individual Eucalyptus globulus leaves from the time of emergence until cessation of growth. Leaf water relations variables and growth rates were determined as relative humidity was changed on an hourly basis. Yield threshold and cell wall extensibility were estimated from plots of leaf growth rate versus turgor. Cell wall extensibility was also measured by the Instron technique, and yield threshold was determined experimentally both by stress relaxation in a psychrometer chamber and by incubation in a range of polyethylene glycol solutions. Once emerging leaves reached approximately 5 cm(2) in size, increases in leaf area were rapid throughout the expansive phase and varied little between light and dark periods. Both leaf growth rate and turgor were sensitive to changes in humidity, and in the longer term, both yield threshold and cell wall extensibility changed as the leaf aged. Rapidly expanding leaves had a very low yield threshold and high cell wall extensibility, whereas mature leaves had low cell wall extensibility. Yield threshold increased with leaf age.

The light response of mesophyll conductance is controlled by structure across leaf profiles.

PubMed

Théroux-Rancourt, Guillaume; Gilbert, Matthew E

2017-05-01

Mesophyll conductance to CO 2 (g m ) may respond to light either through regulated dynamic mechanisms or due to anatomical and structural factors. At low light, some layers of cells in the leaf cross-section approach photocompensation and contribute minimally to bulk leaf photosynthesis and little to whole leaf g m (g m,leaf ). Thus, the bulk g m,leaf will appear to respond to light despite being based upon cells having an anatomically fixed mesophyll conductance. Such behaviour was observed in species with contrasting leaf structure using the variable J or stable isotope method of measuring g m,leaf . A species with bifacial structure, Arbutus × 'Marina', and an isobilateral species, Triticum durum L., had contrasting responses of g m,leaf upon varying adaxial or abaxial illumination. Anatomical observations, when coupled with the proposed model of g m,leaf to photosynthetic photon flux density (PPFD) response, successfully represented the observed gas exchange data. The theoretical and observed evidence that g m,leaf apparently responds to light has large implications for how g m,leaf values are interpreted, particularly limitation analyses, and indicates the importance of measuring g m under full light saturation. Responses of g m,leaf to the environment should be treated as an emergent property of a distributed 3D structure, and not solely a leaf area-based phenomenon. © 2016 John Wiley & Sons Ltd.

Arrangement Analysis of Leaves Optimized on Photon Flux Density or Photosynthetic Rate

NASA Astrophysics Data System (ADS)

Obara, Shin'ya; Tanno, Itaru

By clarifying a plant evolutive process, useful information may be obtained on engineering. Consequently, an analysis algorithm that investigates the optimal arrangement of plant leaves was developed. In the developed algorithm, the Monte Carlo method is introduced and sunlight is simulated. Moreover, the arrangement optimization of leaves is analyzed using a Genetic Algorithm (GA). The number of light quanta (photon flux density) that reaches leaves, or the average photosynthetic rate of the same was set as the objective function, and leaf models of a dogwood and a ginkgo tree were analyzed. The number of leaf models was set between two to four, and the position of the leaf was expressed in terms of the angle of direction, elevation angle, rotation angle, and the representative length of the branch of a leaf. The chromosome model introduced into GA consists of information concerning the position of the leaf. Based on the analysis results, the characteristics of the leaf of an actual plant could be simulated by ensuring the algorithm had multiple constrained conditions. The optimal arrangement of leaves differs in maximization of the photon flux density, and that of the average value of a photosynthetic rate. Furthermore, the leaf form affecting the optimal arrangement of leave and also having a significant influence also on a photosynthetic rate was shown.

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.

Coordination between leaf and stem traits related to leaf carbon gain and hydraulics across 32 drought-tolerant angiosperms.

PubMed

Ishida, Atsushi; Nakano, Takashi; Yazaki, Kenichi; Matsuki, Sawako; Koike, Nobuya; Lauenstein, Diego L; Shimizu, Michiru; Yamashita, Naoko

2008-05-01

We examined 15 traits in leaves and stems related to leaf C economy and water use for 32 co-existing angiosperms at ridge sites with shallow soil in the Bonin Islands. Across species, stem density was positively correlated to leaf mass per area (LMA), leaf lifespan (LLS), and total phenolics and condensed tannins per unit leaf N (N-based), and negatively correlated to leaf osmotic potential and saturated water content in leaves. LMA and LLS were negatively correlated to photosynthetic parameters, such as area-, mass-, and N-based assimilation rates. Although stem density and leaf osmotic potential were not associated with photosynthetic parameters, they were associated with some parameters of the leaf C economy, such as LMA and LLS. In the principal component (PCA) analysis, the first three axes accounted for 74.4% of total variation. Axis 1, which explained 41.8% of the total variation, was well associated with parameters for leaf C and N economy. Similarly, axis 2, which explained 22.3% of the total variation, was associated with parameters for water use. Axis 3, which explained 10.3% of the total variation, was associated with chemical defense within leaves. Axes 1 and 2 separated functional types relatively well, i.e., creeping trees, ruderal trees, other woody plants, C(3) shrubs and forbs, palms, and CAM plants, indicating that plant functional types were characterized by similar attributes of traits related to leaf C and N economy and water use. In addition, when the plot was extended by two unrelated traits, leaf mass-based assimilation rates and stem density, it also separated these functional types. These data indicate that differences in the functional types with contrasting plant strategies can be attributed to functional integration among leaf C economy, hydraulics, and leaf longevity, and that both leaf mass-based assimilation rates and stem density are key factors reflecting the different functions of plant species.

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.

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.

Are leaf breakdown rates a useful measure of stream integrity along an agricultural landuse gradient?

Treesearch

E.M. Hagen; J.R. Webster; E.F. Benfield

2006-01-01

Biological indicators often are used to assess and manage water quality in anthropogenically altered stream systems. Leaf breakdown has the potential to be a good indicator of stream integrity because it integrates a varietyof biological, chemical, and physical conditions. Red maple (Acer rubrum L.) leaf breakdown rates were measured along a gradient...

Photosynthetic induction and its diffusional, carboxylation and electron transport processes as affected by CO2 partial pressure, temperature, air humidity and blue irradiance.

PubMed

Kaiser, Elias; Kromdijk, Johannes; Harbinson, Jeremy; Heuvelink, Ep; Marcelis, Leo F M

2017-01-01

Plants depend on photosynthesis for growth. In nature, factors such as temperature, humidity, CO 2 partial pressure, and spectrum and intensity of irradiance often fluctuate. Whereas irradiance intensity is most influential and has been studied in detail, understanding of interactions with other factors is lacking. We tested how photosynthetic induction after dark-light transitions was affected by CO 2 partial pressure (20, 40, 80 Pa), leaf temperatures (15·5, 22·8, 30·5 °C), leaf-to-air vapour pressure deficits (VPD leaf-air ; 0·5, 0·8, 1·6, 2·3 kPa) and blue irradiance (0-20 %) in tomato leaves (Solanum lycopersicum). Rates of photosynthetic induction strongly increased with CO 2 partial pressure, due to increased apparent Rubisco activation rates and reduced diffusional limitations. High leaf temperature produced slightly higher induction rates, and increased intrinsic water use efficiency and diffusional limitation. High VPD leaf-air slowed down induction rates and apparent Rubisco activation and (at 2·3 kPa) induced damped stomatal oscillations. Blue irradiance had no effect. Slower apparent Rubisco activation in elevated VPD leaf-air may be explained by low leaf internal CO 2 partial pressure at the beginning of induction. The environmental factors CO 2 partial pressure, temperature and VPD leaf-air had significant impacts on rates of photosynthetic induction, as well as on underlying diffusional, carboxylation and electron transport processes. Furthermore, maximizing Rubisco activation rates would increase photosynthesis by at most 6-8 % in ambient CO 2 partial pressure (across temperatures and humidities), while maximizing rates of stomatal opening would increase photosynthesis by at most 1-3 %. © 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.

First report of leaf rust of blueberry caused by Thekopsora minima in Mexico

USDA-ARS?s Scientific Manuscript database

Blueberry (Vaccinium corymbosum L.) is becoming an important crop in the states of Jalisco and Michoacan in Mexico. As the area under blueberry cultivation increases, new diseases causing severe losses are appearing. Leaf rust is one of the most destructive diseases of blueberry in Mexico. Sori on t...

Genome-wide association mapping of leaf rust response in a durum wheat worldwide germplasm collection

USDA-ARS?s Scientific Manuscript database

Leaf rust (caused by Puccinia triticina Eriks.) is increasingly impacting durum wheat production with the recent appearance of races with virulence to widely grown cultivars in many durum producing areas worldwide. A highly virulent P. triticina race on durum wheat was recently collected in Kansas....

Does leaf chemistry differentially affect breakdown in tropical versus temperate streams? Importance of standardized analytical techniques to measure leaf chemistry

Treesearch

Marcelo Ardon; Catherine M. Pringle; Susan L. Eggert

2009-01-01

Comparisons of the effects of leaf litter chemistry on leaf breakdown rates in tropical vs temperate streams are hindered by incompatibility among studies and across sites of analytical methods used to...

Leaf hydraulics and drought stress: response, recovery and survivorship in four woody temperate plant species.

PubMed

Blackman, Christopher J; Brodribb, Timothy J; Jordan, Gregory J

2009-11-01

Efficient conduction of water inside leaves is essential for leaf function, yet the hydraulic-mediated impact of drought on gas exchange remains poorly understood. Here we examine the decline and subsequent recovery of leaf water potential (Psi(leaf)), leaf hydraulic conductance (K(leaf)), and midday transpiration (E) in four temperate woody species exposed to controlled drought conditions ranging from mild to lethal. During drought the vulnerability of K(leaf) to declining Psi(leaf) varied greatly among the species sampled. Following drought, plants were rewatered and the rate of E and K(leaf) recovery was found to be strongly dependent on the severity of the drought imposed. Gas exchange recovery was strongly correlated with the relatively slow recovery of K(leaf) for three of the four species, indicating conformity to a hydraulic-stomatal limitation model of plant recovery. However, there was also a shift in the sensitivity of stomata to Psi(leaf) suggesting that the plant hormone abscisic acid may be involved in limiting the rate of stomatal reopening. The level of drought tolerance varied among the four species and was correlated with leaf hydraulic vulnerability. These results suggest that species-specific variation in hydraulic properties plays a fundamental role in steering the dynamic response of plants during recovery.

How do leaf hydraulics limit stomatal conductance at high water vapour pressure deficits?

PubMed

Bunce, James A

2006-08-01

A reduction in leaf stomatal conductance (g) with increasing leaf-to-air difference in water vapour pressure (D) is nearly ubiquitous. Ecological comparisons of sensitivity have led to the hypothesis that the reduction in g with increasing D serves to maintain leaf water potentials above those that would cause loss of hydraulic conductance. A reduction in leaf water potential is commonly hypothesized to cause stomatal closure at high D. The importance of these particular hydraulic factors was tested by exposing Abutilon theophrasti, Glycine max, Gossypium hirsutum and Xanthium strumarium to D high enough to reduce g and then decreasing ambient carbon dioxide concentration ([CO2]), and observing the resulting changes in g, transpiration rate and leaf water potential, and their reversibility. Reducing the [CO2] at high D increased g and transpiration rate and lowered leaf water potential. The abnormally high transpiration rates did not result in reductions in hydraulic conductance. Results indicate that low water potential effects on g at high D could be overcome by low [CO2], and that even lower leaf water potentials did not cause a reduction in hydraulic conductance in these well-watered plants. Reduced g at high D in these species resulted primarily from increased stomatal sensitivity to [CO2] at high D, and this increased sensitivity may mediate stomatal responses to leaf hydraulics at high D.

Phytoluminographic Detection of Dynamic Variations in Leaf Gaseous Conductivity 1

PubMed Central

Ellenson, James L.

1985-01-01

Gas exchange and plant luminescence (delayed light emission) of a single red kidney bean leaf undergoing synchronous oscillations in gas exchange were recorded and analyzed. Introduction of 1.1 microliter per liter SO2 during these oscillations produced increases in plant luminescence that, when averaged over a portion of the leaf, oscillated in phase with the gas exchange oscillations. However, examination of a video record of the plant luminescence showed not only that luminescence intensities tended to be localized within discrete areas of the leaf, but that the time-dependence of luminescence intensities within these regions varied considerably from the period, amplitude, and often phase of the overall gas exchange oscillations. The video recording also showed that changes in luminescence intensities appeared to migrate across the leaf in wave-like patterns. These data are interpreted in terms of localized fluctuations in gaseous conductances of the leaf. Images Fig. 3 PMID:16664350

[Effects of Cunninghamia lanceolata-broadleaved tree species mixed leaf litters on active soil organic matter].

PubMed

Wang, Qing-kui; Wang, Si-long; Yu, Xiao-jun; Zhang, Jian; Liu, Yan-xin

2007-06-01

With incubation test, this paper studied the effects of Cunninghamia lanceolata leaf litter and its mixture with the litters of main broadleaved tree species in subtropical China, such as Alnus cremastogyne, Kalopanax septemlobus and Michelia macclurei on active soil organic matter. The results showed that adding leaf litters into soil could significantly increase soil microbial biomass C and N, respiration rate and dissolved organic C, and mixed leaf litters were more effective than C. lanceolata leaf litter in increasing soil dissolved organic C. By the end of the incubation, the increment of soil microbial biomass C and N, respiration rate, and dissolved organic C in treatments C. lanceolata leaf litter and C. lanceolata-broadleaved tree species mixed leaf litters was 49% and 63%, 35% and 75%, 65% and 100%, and 66% and 108%, respectively, compared with control. The addition of leaf litters had no significant effects on soil microbial quotient and microbial biomass C/N ratio.

Steady shear flow properties of Cordia myxa leaf gum as a function of concentration and temperature.

PubMed

Chaharlang, Mahmood; Samavati, Vahid

2015-08-01

The steady shear flow properties of dispersions of Cordia myxa leaf gum (CMLG) were determined as a function of concentration (0.5-2.5%, w/w), and temperature (10-50 °C). The CMLG dispersions exhibited strong shear-thinning behavior at all concentrations and temperatures. The Power-law (Ostwald-Waele's) and Herschel-Bulkley models were employed to characterize flow behavior of CMLG solutions at 0.1-100 s(-1) shear rate. Non-Newtonian shear-thinning behavior was observed at all temperatures and concentrations. While increase in temperature decreased the viscosity and increased the flow behavior indices, adverse effect was obtained by increasing the concentration. The Power-law model was found the best model to describe steady shear flow behavior of CMLG. The pseudoplasticity of CMLG increased markedly with concentration. An Arrhenius-type model was also used to describe the effect of temperature. The activation energy (Ea) appeared in the range of 5.972-18.104 kJ/mol, as concentration increased from 0.5% to 2.5%, at a shear rate of 10 s(-1). Copyright © 2015 Elsevier B.V. All rights reserved.

Photomorphogenesis and photoassimilation in soybean and sorghum grown under broad spectrum or blue-deficient light sources

NASA Technical Reports Server (NTRS)

Britz, S. J.; Sager, J. C.; Knott, W. M. (Principal Investigator)

1990-01-01

The role of blue light in plant growth and development was investigated in soybean (Glycine max [L.] Merr. cv Williams) and sorghum (Sorghum bicolor [L.] Moench. cv Rio) grown under equal photosynthetic photon fluxes (approximately 500 micromoles per square meter per second) from broad spectrum daylight fluorescent or blue-deficient, narrow-band (589 nanometers) low pressure sodium (LPS) lamps. Between 14 and 18 days after sowing, it was possible to relate adaptations in photosynthesis and leaf growth to dry matter accumulation. Soybean development under LPS light was similar in several respects to that of shaded plants, consistent with an important role for blue light photoreceptors in regulation of growth response to irradiance. Thus, soybeans from LPS conditions partitioned relatively more growth to leaves and maintained higher average leaf area ratios (mean LAR) that compensated lower net assimilation rates (mean NAR). Relative growth rates were therefore comparable to plants from daylight fluorescent lamps. Reductions in mean NAR were matched by lower rates of net photosynthesis (A) on an area basis in the major photosynthetic source (first trifoliolate) leaf. Lower A in soybean resulted from reduced leaf dry matter per unit leaf area, but lower A under LPS conditions in sorghum correlated with leaf chlorosis and reduced total nitrogen (not observed in soybean). In spite of a lower A, mean NAR was larger in sorghum from LPS conditions, resulting in significantly greater relative growth rates (mean LAR was approximately equal for both light conditions). Leaf starch accumulation rate was higher for both species and starch content at the end of the dark period was elevated two- and three-fold for sorghum and soybean, respectively, under LPS conditions. Possible relations between starch accumulation, leaf export, and plant growth in response to spectral quality were considered.

Hydraulic conductance as well as nitrogen accumulation plays a role in the higher rate of leaf photosynthesis of the most productive variety of rice in Japan.

PubMed

Taylaran, Renante D; Adachi, Shunsuke; Ookawa, Taiichiro; Usuda, Hideaki; Hirasawa, Tadashi

2011-07-01

An indica variety Takanari is known as one of the most productive rice varieties in Japan and consistently produces 20-30% heavier dry matter during ripening than Japanese commercial varieties in the field. The higher rate of photosynthesis of individual leaves during ripening has been recognized in Takanari. By using pot-grown plants under conditions of minimal mutual shading, it was confirmed that the higher rate of leaf photosynthesis is responsible for the higher dry matter production after heading in Takanari as compared with a japonica variety, Koshihikari. The rate of leaf photosynthesis and shoot dry weight became larger in Takanari after the panicle formation and heading stages, respectively, than in Koshihikari. Roots grew rapidly in the panicle formation stage until heading in Takanari compared with Koshihikari. The higher rate of leaf photosynthesis in Takanari resulted not only from the higher content of leaf nitrogen, which was caused by its elevated capacity for nitrogen accumulation, but also from higher stomatal conductance. When measured under light-saturated conditions, stomatal conductance was already decreased due to the reduction in leaf water potential in Koshihikari even under conditions of a relatively small difference in leaf-air vapour pressure difference. In contrast, the higher stomatal conductance was supported by the maintenance of higher leaf water potential through the higher hydraulic conductance in Takanari with the larger area of root surface. However, no increase in root hydraulic conductivity was expected in Takanari. The larger root surface area of Takanari might be a target trait in future rice breeding for increasing dry matter production.

Spatial and Temporal Relationships of Stomatal Development and Function in a Temperate Forest Canopy

NASA Astrophysics Data System (ADS)

Dow, G.; Richardson, A. D.

2017-12-01

Mechanisms that control stomatal development ultimately constrain leaf physiology by determining the anatomical maximum rate for gas-exchange (gsmax). However, we know comparatively less about how these regulatory processes define stomatal conductance (gs) and photosynthesis or how this information translates between model systems and important crop or native plant species. Here, we test relationships between stomatal development and leaf physiology that have been established in model systems by sampling trees in a mature forest ecosystem. We found that plasticity in gsmax was limited throughout the canopy, despite other changes in leaf structure and function that are driven by environmental gradients in the canopy. However, the ratio between gs and gsmax was predictive of gas flux in the canopy and species-independent. Variation in the gs : gsmax ratio appeared to minimize the energy required to control aperture size via guard cell turgor pressure, thus compensating for the initial over-investment in stomatal production. gsmax also remained a strong predictor of photosynthetic potential and intrinsic water-use efficiency. The temporal relationship between gsmax and these functional leaf traits might depend on long-term adjustments in stomatal development, which was sensitive to increases in atmospheric CO2 in our study. The absence of a spatial response and the presence of a temporal response in stomatal development infers that multiple mechanisms may integrate environmental signaling in the developmental pathway. Collectively, this research helps to define the larger significance of the stomatal mechanisms being identified in model systems.

Frontier mutualism: coevolutionary patterns at the northern range limit of the leaf-cutter ant–fungus symbiosis

PubMed Central

Mueller, Ulrich G.; Mikheyev, Alexander S.; Solomon, Scott E.; Cooper, Michael

2011-01-01

Tropical leaf-cutter ants cultivate the fungus Attamyces bromatificus in a many-to-one, diffuse coevolutionary relationship where ant and fungal partners re-associate frequently over time. To evaluate whether ant–Attamyces coevolution is more specific (tighter) in peripheral populations, we characterized the host-specificities of Attamyces genotypes at their northern, subtropical range limits (southern USA, Mexico and Cuba). Population-genetic patterns of northern Attamyces reveal features that have so far not been observed in the diffusely coevolving, tropical ant–Attamyces associations. These unique features include (i) cases of one-to-one ant–Attamyces specialization that tighten coevolution at the northern frontier; (ii) distributions of genetically identical Attamyces clones over large areas (up to 81 000 km2, approx. the area of Ireland, Austria or Panama); (iii) admixture rates between Attamyces lineages that appear lower in northern than in tropical populations; and (iv) long-distance gene flow of Attamyces across a dispersal barrier for leaf-cutter ants (ocean between mainland North America and Cuba). The latter suggests that Attamyces fungi may occasionally disperse independently of the ants, contrary to the traditional assumption that Attamyces fungi depend entirely on leaf-cutter queens for dispersal. Peripheral populations in Argentina or at mid-elevation sites in the Andes may reveal additional regional variants in ant–Attamyces coevolution. Studies of such populations are most likely to inform models of coextinctions of obligate mutualistic partners that are doubly stressed by habitat marginality and by environmental change. PMID:21389026

The Autophagic Degradation of Chloroplasts via Rubisco-Containing Bodies Is Specifically Linked to Leaf Carbon Status But Not Nitrogen Status in Arabidopsis1[W][OA

PubMed Central

Izumi, Masanori; Wada, Shinya; Makino, Amane; Ishida, Hiroyuki

2010-01-01

Autophagy is an intracellular process facilitating the vacuolar degradation of cytoplasmic components and is important for nutrient recycling during starvation. We previously demonstrated that chloroplasts can be partially mobilized to the vacuole by autophagy via spherical bodies named Rubisco-containing bodies (RCBs). Although chloroplasts contain approximately 80% of total leaf nitrogen and represent a major carbon and nitrogen source for new growth, the relationship between leaf nutrient status and RCB production remains unclear. We examined the effects of nutrient factors on the appearance of RCBs in leaves of transgenic Arabidopsis (Arabidopsis thaliana) expressing stroma-targeted fluorescent proteins. In excised leaves, the appearance of RCBs was suppressed by the presence of metabolic sugars, which were added externally or were produced during photosynthesis in the light. The light-mediated suppression was relieved by the inhibition of photosynthesis. During a diurnal cycle, RCB production was suppressed in leaves excised at the end of the day with high starch content. Starchless mutants phosphoglucomutase and ADP-Glc pyrophosphorylase1 produced a large number of RCBs, while starch-excess mutants starch-excess1 and maltose-excess1 produced fewer RCBs. In nitrogen-limited plants, as leaf carbohydrates were accumulated, RCB production was suppressed. We propose that there exists a close relationship between the degradation of chloroplast proteins via RCBs and leaf carbon but not nitrogen status in autophagy. We also found that the appearance of non-RCB-type autophagic bodies was not suppressed in the light and somewhat responded to nitrogen in excised leaves, unlike RCBs. These results imply that the degradation of chloroplast proteins via RCBs is specifically controlled in autophagy. PMID:20807997

Proteaceae from severely phosphorus-impoverished soils extensively replace phospholipids with galactolipids and sulfolipids during leaf development to achieve a high photosynthetic phosphorus-use-efficiency.

PubMed

Lambers, Hans; Cawthray, Gregory R; Giavalisco, Patrick; Kuo, John; Laliberté, Etienne; Pearse, Stuart J; Scheible, Wolf-Rüdiger; Stitt, Mark; Teste, François; Turner, Benjamin L

2012-12-01

Proteaceae species in south-western Australia occur on severely phosphorus (P)-impoverished soils. They have very low leaf P concentrations, but relatively fast rates of photosynthesis, thus exhibiting extremely high photosynthetic phosphorus-use-efficiency (PPUE). Although the mechanisms underpinning their high PPUE remain unknown, one possibility is that these species may be able to replace phospholipids with nonphospholipids during leaf development, without compromising photosynthesis. For six Proteaceae species, we measured soil and leaf P concentrations and rates of photosynthesis of both young expanding and mature leaves. We also assessed the investment in galactolipids, sulfolipids and phospholipids in young and mature leaves, and compared these results with those on Arabidopsis thaliana, grown under both P-sufficient and P-deficient conditions. In all Proteaceae species, phospholipid levels strongly decreased during leaf development, whereas those of galactolipids and sulfolipids strongly increased. Photosynthetic rates increased from young to mature leaves. This shows that these species extensively replace phospholipids with nonphospholipids during leaf development, without compromising photosynthesis. A considerably less pronounced shift was observed in A. thaliana. Our results clearly show that a low investment in phospholipids, relative to nonphospholipids, offers a partial explanation for a high photosynthetic rate per unit leaf P in Proteaceae adapted to P-impoverished soils. © 2012 The Authors. New Phytologist © 2012 New Phytologist Trust.

Shelters of leaf-tying herbivores decompose faster than leaves damaged by free-living insects: Implications for nutrient turnover in polluted habitats.

PubMed

Kozlov, Mikhail V; Zverev, Vitali; Zvereva, Elena L

2016-10-15

Leaf-eating insects can influence decomposition processes by modifying quality of leaf litter, and this impact can be especially pronounced in habitats where leaf-eating insects reach high densities, for example in heavily polluted areas. We hypothesized that the decomposition rate is faster for shelters of leaf-tying larvae than for leaves damaged by free-living insects, in particular due to the accumulation of larval frass within shelters. We exposed litter bags containing samples of three different compositions (shelters built by moth larvae, leaves damaged by free-living insects and intact leaves of mountain birch, Betula pubescens ssp. czerepanovii) for one year at two heavily polluted sites near the nickel-copper smelter at Monchegorsk in north-western Russia and at two unpolluted sites. The decomposition rate of leaves damaged by free-living insects was 91% of that of undamaged leaves, whereas the mass loss of leaves composing shelters did not differ of that of undamaged leaves. These differences between leaves damaged by different guilds of herbivorous insects were uniform across the study sites, although the decomposition rate in polluted sites was reduced to 77% of that in unpolluted sites. Addition of larval frass to undamaged leaves had no effect on the subsequent decomposition rate. Therefore we suggest that damaged leaves tied by shelter-building larvae decompose faster than untied damaged leaves due to a looser physical structure of the litter, which creates favourable conditions for detritivores and soil decomposers. Thus, while leaf damage by insects per se reduces litter quality and its decomposition rate, structuring of litter by leaf-tying insects counterbalances these negative effects. We conclude that leaf-tying larvae, in contrast to free-living defoliators, do not impose negative effects on nutrient turnover rate even at their high densities, which are frequently observed in heavily polluted sites. Copyright © 2016 Elsevier B.V. All rights reserved.

A study on dosimetric properties of electronic portal imaging device and its use as a quality assurance tool in Volumetric Modulated Arc Therapy

PubMed Central

Sukumar, Prabakar; Padmanaban, Sriram; Jeevanandam, Prakash; Syam Kumar, S.A.; Nagarajan, Vivekanandan

2011-01-01

Aim In this study, the dosimetric properties of the electronic portal imaging device were examined and the quality assurance testing of Volumetric Modulated Arc Therapy was performed. Background RapidArc involves the variable dose rate, leaf speed and the gantry rotation. The imager was studied for the effects like dose, dose rate, field size, leaf speed and sag during gantry rotation. Materials and methods A Varian RapidArc machine equipped with 120 multileaf collimator and amorphous silicon detector was used for the study. The characteristics that are variable in RapidArc treatment were studied for the portal imager. The accuracy of a dynamic multileaf collimator position at different gantry angles and during gantry rotation was examined using the picket fence test. The control of the dose rate and gantry speed was verified using a test field irradiating seven strips of the same dose with different dose rate and gantry speeds. The control over leaf speed during arc was verified by irradiating four strips of different leaf speeds with the same dose in each strip. To verify the results, the RapidArc test procedure was compared with the X-Omat film and verified for a period of 6 weeks using EPID. Results The effect of gantry rotation on leaf accuracy was minimal. The dose in segments showed good agreement with mean deviation of 0.8% for dose rate control and 1.09% for leaf speed control over different gantry speeds. Conclusion The results provided a precise control of gantry speed, dose rate and leaf speeds during RapidArc delivery and were consistent over 6 weeks. PMID:24376989

Remote sensing of forest canopy and leaf biochemical contents

NASA Technical Reports Server (NTRS)

Peterson, David L.; Matson, Pamela A.; Card, Don H.; Aber, John D.; Wessman, Carol; Swanberg, Nancy; Spanner, Michael

1988-01-01

Recent research on the remote sensing of forest leaf and canopy biochemical contents suggests that the shortwave IR region contains this information; laboratory analyses of dry ground leaves have yielded reliable predictive relationships between both leaf nitrogen and lignin with near-IR spectra. Attention is given to the application of these laboratory techniques to a limited set of spectra from fresh, whole leaves of conifer species. The analysis of Airborne Imaging Spectrometer data reveals that total water content variations in deciduous forest canopies appear as overall shifts in the brightness of raw spectra.

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

Interactions among cluster-root investment, leaf phosphorus concentration, and relative growth rate in two Lupinus species.

PubMed

Wang, Xing; Veneklaas, Erik J; Pearse, Stuart J; Lambers, Hans

2015-09-01

Cluster-root (CR) formation is a desirable trait to improve phosphorus (P) acquisition as global P resources are dwindling. CRs in some lupine species are suppressed at higher P status. Whether increased growth rate enhances CR formation due to a "dilution" of leaf P concentration is unknown. We investigated interactive effects of leaf P status and relative growth rate (RGR) on CR formation in two Lupinus species, which differ in their CR biomass investment. Variation in RGR was imposed by varying day length. Lupinus albus and L. pilosus were grown hydroponically with KH2PO4 at a day length of 6, 10, or 14 h. We used a slightly higher P supply at longer day lengths to avoid a decline in leaf P concentration, which would induce CRs. Cluster-root percentage, leaf P concentrations, and RGR were determined at 22, 38, and 52 d after sowing. Lupinus species grown at similar root P availability, but with a faster growth rate, as dependent on day length, showed a greater CR percentage. Because our aim to achieve exactly the same leaf P concentrations at different day lengths was only partially achieved, we carried out a multiple regression analysis. This analysis showed the CR percentage was strongly and negatively correlated with plant P status and only marginally and positively correlated with RGR. The two Lupinus species invariably formed fewer cluster roots at higher leaf P status, irrespective of RGR. Differences in RGR or leaf P concentration cannot explain the species-specific variation in cluster-root investment. © 2015 Botanical Society of America.

A growth analysis of waterlogging damage in mung bean (Phaseolus aureus)

NASA Technical Reports Server (NTRS)

Musgrave, M. E.; Vanhoy, M. A.

1989-01-01

Mung beans (Phaseolus aureus Roxb.) were grown for 2 weeks in gravel-vermiculite soilless mix in a growth chamber and subjected to a 1-week waterlogging period followed by a 1-week recovery period. Sequential harvests were made to determine the time course of effects of waterlogging and subsequent recovery on growth parameters by techniques of growth analysis. Root dry matter was the first to be affected, along with an increase in leaf dry matter and specific leaf weight. After a 1-week waterlogging period, specific leaf weight had more than doubled in the stressed plants. Leaf area declined in relation to the control plants as did the ratio of root dry matter to shoot dry matter. During the recovery period there was an increase in the dry matter allocation to the roots relative to the shoot. Specific leaf weight fell to control levels although the rate of leaf area elaboration did not increase during this time, suggesting a redistribution of stored assimilates from the leaves. Net assimilation rate increased during the waterlogging period, probably due to a restriction in root metabolism and reduced translocation out of the leaf rather than to an increase in photosynthesis. Net assimilation rate of waterlogged plants was severely reduced compared with control plants during the recovery period. Both relative growth rate and leaf area duration declined during the waterlogging period and declined further subsequent to the waterlogging treatment. The results illustrate the interrelationships between root and shoot carbon budgets in mung bean during response to the stress of waterlogging.

Impact of epidermal leaf mining by the aspen leaf miner (Phyllocnistis populiella) on the growth, physiology, and leaf longevity of quaking aspen

Treesearch

Diane Wagner; Linda DeFoliart; Patricia Doak; Jenny Schneiderheinze

2008-01-01

We studied the effect of epidermal mining on aspen growth and physiology during an outbreak of Phyllocnistis populiella in the boreal forest of interior Alaska. Experimental reduction of leaf miner density across two sites and 3 years significantly increased annual apsen growth rates relative to naturally mined controls. Leaf mining damage was...

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 litter decomposition rates increase with rising mean annual temperature in Hawaiian tropical montane wet forests

PubMed Central

Bothwell, Lori D.; Giardina, Christian P.; Litton, Creighton M.

2014-01-01

Decomposing litter in forest ecosystems supplies nutrients to plants, carbon to heterotrophic soil microorganisms and is a large source of CO2 to the atmosphere. Despite its essential role in carbon and nutrient cycling, the temperature sensitivity of leaf litter decay in tropical forest ecosystems remains poorly resolved, especially in tropical montane wet forests where the warming trend may be amplified compared to tropical wet forests at lower elevations. We quantified leaf litter decomposition rates along a highly constrained 5.2 °C mean annual temperature (MAT) gradient in tropical montane wet forests on the Island of Hawaii. Dominant vegetation, substrate type and age, soil moisture, and disturbance history are all nearly constant across this gradient, allowing us to isolate the effect of rising MAT on leaf litter decomposition and nutrient release. Leaf litter decomposition rates were a positive linear function of MAT, causing the residence time of leaf litter on the forest floor to decline by ∼31 days for each 1 °C increase in MAT. Our estimate of the Q10 temperature coefficient for leaf litter decomposition was 2.17, within the commonly reported range for heterotrophic organic matter decomposition (1.5–2.5) across a broad range of ecosystems. The percentage of leaf litter nitrogen (N) remaining after six months declined linearly with increasing MAT from ∼88% of initial N at the coolest site to ∼74% at the warmest site. The lack of net N immobilization during all three litter collection periods at all MAT plots indicates that N was not limiting to leaf litter decomposition, regardless of temperature. These results suggest that leaf litter decay in tropical montane wet forests may be more sensitive to rising MAT than in tropical lowland wet forests, and that increased rates of N release from decomposing litter could delay or prevent progressive N limitation to net primary productivity with climate warming. PMID:25493213

Dry olive leaf extract counteracts L-thyroxine-induced genotoxicity in human peripheral blood leukocytes in vitro.

PubMed

Topalović, Dijana Žukovec; Živković, Lada; Čabarkapa, Andrea; Djelić, Ninoslav; Bajić, Vladan; Dekanski, Dragana; Spremo-Potparević, Biljana

2015-01-01

The thyroid hormones change the rate of basal metabolism, modulating the consumption of oxygen and causing production of reactive oxygen species, which leads to the development of oxidative stress and DNA strand breaks. Olive (Olea europaea L.) leaf contains many potentially bioactive compounds, making it one of the most potent natural antioxidants. The objective of this study was to evaluate the genotoxicity of L-thyroxine and to investigate antioxidative and antigenotoxic potential of the standardized oleuropein-rich dry olive leaf extract (DOLE) against hydrogen peroxide and L-thyroxine-induced DNA damage in human peripheral blood leukocytes by using the comet assay. Various concentrations of the extract were tested with both DNA damage inducers, under two different experimental conditions, pretreatment and posttreatment. Results indicate that L-thyroxine exhibited genotoxic effect and that DOLE displayed protective effect against thyroxine-induced genotoxicity. The number of cells with DNA damage, was significantly reduced, in both pretreated and posttreated samples (P < 0.05). Comparing the beneficial effect of all tested concentrations of DOLE, in both experimental protocols, it appears that extract was more effective in reducing DNA damage in the pretreatment, exhibiting protective role against L-thyroxine effect. This feature of DOLE can be explained by its capacity to act as potent free radical scavenger.

Dry Olive Leaf Extract Counteracts L-Thyroxine-Induced Genotoxicity in Human Peripheral Blood Leukocytes In Vitro

PubMed Central

Žukovec Topalović, Dijana; Živković, Lada; Čabarkapa, Andrea; Djelić, Ninoslav; Bajić, Vladan; Spremo-Potparević, Biljana

2015-01-01

The thyroid hormones change the rate of basal metabolism, modulating the consumption of oxygen and causing production of reactive oxygen species, which leads to the development of oxidative stress and DNA strand breaks. Olive (Olea europaea L.) leaf contains many potentially bioactive compounds, making it one of the most potent natural antioxidants. The objective of this study was to evaluate the genotoxicity of L-thyroxine and to investigate antioxidative and antigenotoxic potential of the standardized oleuropein-rich dry olive leaf extract (DOLE) against hydrogen peroxide and L-thyroxine-induced DNA damage in human peripheral blood leukocytes by using the comet assay. Various concentrations of the extract were tested with both DNA damage inducers, under two different experimental conditions, pretreatment and posttreatment. Results indicate that L-thyroxine exhibited genotoxic effect and that DOLE displayed protective effect against thyroxine-induced genotoxicity. The number of cells with DNA damage, was significantly reduced, in both pretreated and posttreated samples (P < 0.05). Comparing the beneficial effect of all tested concentrations of DOLE, in both experimental protocols, it appears that extract was more effective in reducing DNA damage in the pretreatment, exhibiting protective role against L-thyroxine effect. This feature of DOLE can be explained by its capacity to act as potent free radical scavenger. PMID:25789081

Role of aquaporins in determining transpiration and photosynthesis in water-stressed plants: crop water-use efficiency, growth and yield.

PubMed

Moshelion, Menachem; Halperin, Ofer; Wallach, Rony; Oren, Ram; Way, Danielle A

2015-09-01

The global shortage of fresh water is one of our most severe agricultural problems, leading to dry and saline lands that reduce plant growth and crop yield. Here we review recent work highlighting the molecular mechanisms allowing some plant species and genotypes to maintain productivity under water stress conditions, and suggest molecular modifications to equip plants for greater production in water-limited environments. Aquaporins (AQPs) are thought to be the main transporters of water, small and uncharged solutes, and CO2 through plant cell membranes, thus linking leaf CO2 uptake from the intercellular airspaces to the chloroplast with water loss pathways. AQPs appear to play a role in regulating dynamic changes of root, stem and leaf hydraulic conductivity, especially in response to environmental changes, opening the door to using AQP expression to regulate plant water-use efficiency. We highlight the role of vascular AQPs in regulating leaf hydraulic conductivity and raise questions regarding their role (as well as tonoplast AQPs) in determining the plant isohydric threshold, growth rate, fruit yield production and harvest index. The tissue- or cell-specific expression of AQPs is discussed as a tool to increase yield relative to control plants under both normal and water-stressed conditions. © 2014 John Wiley & Sons Ltd.

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.

[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.

Leaf photosynthetic traits scale with hydraulic conductivity and wood density in Panamanian forest canopy trees.

Treesearch

L.S. Santiago; G. Goldstein; F.C. Meinzer; J.B. Fisher; K. Maehado; D. Woodruff; T. Jones

2004-01-01

We investigated how water transport capacity, wood density and wood anatomy were related to leaf photosynthetic traits in two lowland forests in Panama. Leaf-specific hydraulic conductivity (kL) of upper branches was positively correlated with maximum rates of net CO2, assimilation per unit leaf area (Aarea...

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

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.

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.

Temporal variation of biomass and productivity of Thalassia testudinum (Hydrocharitaceae) in Venezuela, Southern Caribbean.

PubMed

Pérez, Daisy; Guevara, Marcel; Bone, David

2006-06-01

Annual biomass and productivity of Thalassia testudinum were determined during a year at a seagrass bed located in the Parque Nacional Morrocoy, Venezuela. Leaf, rhizome and root biomass were determined monthly, together with short-shoot density, from February 1992 to January 1993, from nine replicated core samples. Productivity was measured using the methodology by Zieman (1974) with minor modifications, and leaf turnover rate was calculated. Leaf biomass values ranged between 101.73 dry g m(-2) in February and 178.11 dry g m(-2) in August. Productivity ranged from 1.69 dry g m(-2) d(-1) in April and October to 3.30 dry g m(-2) d(-1) in July, showing two annual peaks: one in July and one in March. The leaf turnover rate showed the highest value in June (2.41% d(-1)) and the lowest in May (1.23% d(-1)). Sampling time differences in leaf biomass, productivity and turnover rate were statistically significant. Short-shoot density values varied between 811.10 shoots m(-2) in April and 1226.08 shoots m(-2) in December, but the differences were not significant along the year. These results indicated seasonal trends for leaf biomass, productivity and turnover rate of T. testudinum in the Southern Caribbean (latitude 10 degrees N).

The influence of leaf anatomy on the internal light environment and photosynthetic electron transport rate: exploration with a new leaf ray tracing model

PubMed Central

Xiao, Yi; Tholen, Danny; Zhu, Xin-Guang

2016-01-01

Leaf photosynthesis is determined by biochemical properties and anatomical features. Here we developed a three-dimensional leaf model that can be used to evaluate the internal light environment of a leaf and its implications for whole-leaf electron transport rates (J). This model includes (i) the basic components of a leaf, such as the epidermis, palisade and spongy tissues, as well as the physical dimensions and arrangements of cell walls, vacuoles and chloroplasts; and (ii) an efficient forward ray-tracing algorithm, predicting the internal light environment for light of wavelengths between 400 and 2500nm. We studied the influence of leaf anatomy and ambient light on internal light conditions and J. The results show that (i) different chloroplasts can experience drastically different light conditions, even when they are located at the same distance from the leaf surface; (ii) bundle sheath extensions, which are strips of parenchyma, collenchyma or sclerenchyma cells connecting the vascular bundles with the epidermis, can influence photosynthetic light-use efficiency of leaves; and (iii) chloroplast positioning can also influence the light-use efficiency of leaves. Mechanisms underlying leaf internal light heterogeneity and implications of the heterogeneity for photoprotection and for the convexity of the light response curves are discussed. PMID:27702991

Large Drought-induced Variations in Oak Leaf Volatile Organic Compound Emissions during PINOT NOIR 2012

EPA Pesticide Factsheets

Leaf level oak isoprene emissions and co2/H2O exchange in the Ozarks, USABAGeron.csv is the speciated biomass displayed in Figure 1.Biomass Dry Weights.xlsx is used to convert leaf area to dry leaf biomass and is used in Figure 2.Daly Ozarks leaf ISOP.txt and MOFLUX_Isoprene Summary_refined Tcurve data.xlsx are the leaf isoprene emission rate files shown in Figure 2.Harley Aug12_Chris.xls is the leaf isoprene emission rate file shown in Figure 3.Daly Ozarks leaf.txt is the BVOC emissions file used for Figure 7 and Table 4.Drought IS.txt is the review data given in Table 2.Fig4 Aug10 2012 Harley.txt is shown in Figure 4.Fig 5 Aug14 2012 Harley.txt is shown in Figure 5.Daly Ozarks Leaf.txt is used in Fig 7.Drought IS.txt is used in Fig 8.This dataset is associated with the following publication:Geron , C., R. Daly , P. Harley, R. Rasmussen, R. Seco, A. Guenther, T. Karl, and L. Gu. Large Drought-Induced Variations in Oak Leaf Volatile Organic Compound Emissions during PINOT NOIR 2012. CHEMOSPHERE. Elsevier Science Ltd, New York, NY, USA, 146: 8-21, (2016).

Deer predation on leaf miners via leaf abscission

NASA Astrophysics Data System (ADS)

Yamazaki, Kazuo; Sugiura, Shinji

2008-03-01

The evergreen oak Quercus gilva Blume sheds leaves containing mines of the leaf miner Stigmella sp. (Lepidoptera: Nepticulidae) earlier than leaves with no mines in early spring in Nara, central Japan. The eclosion rates of the leaf miner in abscised and retained leaves were compared in the laboratory to clarify the effects of leaf abscission on leaf miner survival in the absence of deer. The leaf miner eclosed successfully from both fallen leaves and leaves retained on trees. However, sika deer ( Cervus nippon centralis Kishida) feed on the fallen mined leaves. Field observations showed that deer consume many fallen leaves under Q. gilva trees, suggesting considerable mortality of leaf miners due to deer predation via leaf abscission. This is a previously unreported relationship between a leaf miner and a mammalian herbivore via leaf abscission.

Genetic and Developmental Basis for Increased Leaf Thickness in the Arabidopsis Cvi Ecotype.

PubMed

Coneva, Viktoriya; Chitwood, Daniel H

2018-01-01

Leaf thickness is a quantitative trait that is associated with the ability of plants to occupy dry, high irradiance environments. Despite its importance, leaf thickness has been difficult to measure reproducibly, which has impeded progress in understanding its genetic basis, and the associated anatomical mechanisms that pattern it. Here, we used a custom-built dual confocal profilometer device to measure leaf thickness in the Arabidopsis Ler × Cvi recombinant inbred line population and found statistical support for four quantitative trait loci (QTL) associated with this trait. We used publically available data for a suite of traits relating to flowering time and growth responses to light quality and show that three of the four leaf thickness QTL coincide with QTL for at least one of these traits. Using time course photography, we quantified the relative growth rate and the pace of rosette leaf initiation in the Ler and Cvi ecotypes. We found that Cvi rosettes grow slower than Ler, both in terms of the rate of leaf initiation and the overall rate of biomass accumulation. Collectively, these data suggest that leaf thickness is tightly linked with physiological status and may present a tradeoff between the ability to withstand stress and rapid vegetative growth. To understand the anatomical basis of leaf thickness, we compared cross-sections of Cvi and Ler leaves and show that Cvi palisade mesophyll cells elongate anisotropically contributing to leaf thickness. Flow cytometry of whole leaves show that endopolyploidy accompanies thicker leaves in Cvi. Overall, our data suggest that mechanistically, an altered schedule of cellular events affecting endopolyploidy and increasing palisade mesophyll cell length contribute to increase of leaf thickness in Cvi. Ultimately, knowledge of the genetic basis and developmental trajectory leaf thickness will inform the mechanisms by which natural selection acts to produce variation in this adaptive trait.

Genetic and Developmental Basis for Increased Leaf Thickness in the Arabidopsis Cvi Ecotype

PubMed Central

Coneva, Viktoriya; Chitwood, Daniel H.

2018-01-01

Leaf thickness is a quantitative trait that is associated with the ability of plants to occupy dry, high irradiance environments. Despite its importance, leaf thickness has been difficult to measure reproducibly, which has impeded progress in understanding its genetic basis, and the associated anatomical mechanisms that pattern it. Here, we used a custom-built dual confocal profilometer device to measure leaf thickness in the Arabidopsis Ler × Cvi recombinant inbred line population and found statistical support for four quantitative trait loci (QTL) associated with this trait. We used publically available data for a suite of traits relating to flowering time and growth responses to light quality and show that three of the four leaf thickness QTL coincide with QTL for at least one of these traits. Using time course photography, we quantified the relative growth rate and the pace of rosette leaf initiation in the Ler and Cvi ecotypes. We found that Cvi rosettes grow slower than Ler, both in terms of the rate of leaf initiation and the overall rate of biomass accumulation. Collectively, these data suggest that leaf thickness is tightly linked with physiological status and may present a tradeoff between the ability to withstand stress and rapid vegetative growth. To understand the anatomical basis of leaf thickness, we compared cross-sections of Cvi and Ler leaves and show that Cvi palisade mesophyll cells elongate anisotropically contributing to leaf thickness. Flow cytometry of whole leaves show that endopolyploidy accompanies thicker leaves in Cvi. Overall, our data suggest that mechanistically, an altered schedule of cellular events affecting endopolyploidy and increasing palisade mesophyll cell length contribute to increase of leaf thickness in Cvi. Ultimately, knowledge of the genetic basis and developmental trajectory leaf thickness will inform the mechanisms by which natural selection acts to produce variation in this adaptive trait. PMID:29593772

Measurement of leaf hydraulic conductance and stomatal conductance and their responses to irradiance and dehydration using the Evaporative Flux Method (EFM).

PubMed

Sack, Lawren; Scoffoni, Christine

2012-12-31

Water is a key resource, and the plant water transport system sets limits on maximum growth and drought tolerance. When plants open their stomata to achieve a high stomatal conductance (gs) to capture CO2 for photosynthesis, water is lost by transpiration(1,2). Water evaporating from the airspaces is replaced from cell walls, in turn drawing water from the xylem of leaf veins, in turn drawing from xylem in the stems and roots. As water is pulled through the system, it experiences hydraulic resistance, creating tension throughout the system and a low leaf water potential (Ψ(leaf)). The leaf itself is a critical bottleneck in the whole plant system, accounting for on average 30% of the plant hydraulic resistance(3). Leaf hydraulic conductance (K(leaf) = 1/ leaf hydraulic resistance) is the ratio of the water flow rate to the water potential gradient across the leaf, and summarizes the behavior of a complex system: water moves through the petiole and through several orders of veins, exits into the bundle sheath and passes through or around mesophyll cells before evaporating into the airspace and being transpired from the stomata. K(leaf) is of strong interest as an important physiological trait to compare species, quantifying the effectiveness of the leaf structure and physiology for water transport, and a key variable to investigate for its relationship to variation in structure (e.g., in leaf venation architecture) and its impacts on photosynthetic gas exchange. Further, K(leaf) responds strongly to the internal and external leaf environment(3). K(leaf) can increase dramatically with irradiance apparently due to changes in the expression and activation of aquaporins, the proteins involved in water transport through membranes(4), and K(leaf) declines strongly during drought, due to cavitation and/or collapse of xylem conduits, and/or loss of permeability in the extra-xylem tissues due to mesophyll and bundle sheath cell shrinkage or aquaporin deactivation(5-10). Because K(leaf) can constrain gs and photosynthetic rate across species in well watered conditions and during drought, and thus limit whole-plant performance they may possibly determine species distributions especially as droughts increase in frequency and severity(11-14). We present a simple method for simultaneous determination of K(leaf) and gs on excised leaves. A transpiring leaf is connected by its petiole to tubing running to a water source on a balance. The loss of water from the balance is recorded to calculate the flow rate through the leaf. When steady state transpiration (E, mmol • m(-2) • s(-1)) is reached, gs is determined by dividing by vapor pressure deficit, and K(leaf) by dividing by the water potential driving force determined using a pressure chamber (K(leaf)= E /- Δψ(leaf), MPa)(15). This method can be used to assess K(leaf) responses to different irradiances and the vulnerability of K(leaf) to dehydration(14,16,17).

Photosynthesis in developing leaf of juveniles and adults of three Mediterranean species with different growth forms.

PubMed

Chondrogiannis, Christos; Grammatikopoulos, George

2016-12-01

Leaf development is influenced by almost all the prevailing environmental conditions as well as from the conditions at the time of bud formation. Furthermore, the growth form of a plant determines the leaf longevity and subsequently the investment in biomass and the internal structure of the mesophyll. Therefore, photosynthetic traits of a growing leaf, though, partly predetermined, should also acclimate to temporal changes during developmental period. In addition, the age of the plant can affect photosynthesis of the growing leaf, yet, in the majority of studies, the age is associated to the size of the plant. To test if the reproductive status of the plant affects the time kinetics of the photosynthetic capacity of a growing leaf and the relative contribution of the plants' growth form to the whole procedure, field measurements were conducted in juveniles (prereproductive individuals) and adults (fully reproductive individuals) of an evergreen sclerophyllous shrub (Nerium oleander), a semi-deciduous dimorphic shrub (Phlomis fruticosa), and a winter deciduous tree with pre-leafing flowering (Cercis siliquastrum). PSII structural and functional integrity was progressively developed in all species, but already completed, only some days after leaf expansion in P. fruticosa. Developing leaf as well as fully developed leaf in adults of C. siliquastrum showed enhanced relative size of the pool of final PSI electron acceptors. Photosynthetic traits between juveniles and adults of P. fruticosa were similar, though the matured leaf of adults exhibited lower transpiration rates and improved water-use efficiency than that of juveniles. Adults of the evergreen shrub attained higher CO 2 assimilation rate than juveniles in matured leaf which can be attributed to higher electron flow devoted to carboxylation, and lower photorespiration rate. The reproductive phase of the plant seemed to be involved in modifications of the PSII and PSI functions of the deciduous tree, in carboxylation and photorespiration traits of the evergreen shrub, and in water conductance efficiency of the semi-deciduous shrub. However, it is interesting, that regardless of the growth form of the plant and the prospective leaf longevity of the developing leaf, adults need to support flowering outmatch juveniles, in terms of photosynthesis.

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.

Tree leaf trade-offs are stronger for sub-canopy trees: leaf traits reveal little about growth rates in canopy trees.

PubMed

Wills, Jarrah; Herbohn, John; Hu, Jing; Sohel, Shawkat; Baynes, Jack; Firn, Jennifer

2018-06-01

Can morphological plant functional traits predict demographic rates (e.g., growth) within plant communities as diverse as tropical forests? This is one of the most important next-step questions in trait-based ecology and particularly for global reforestation efforts. Due to the diversity of tropical tree species and their longevity, it is difficult to predict their performance prior to reforestation efforts. In this study, we investigate if simple leaf traits are predictors of the more complex ecological process of plant growth in regenerating selectively logged natural forest within the Wet Tropics (WTs) bioregion of Australia. This study used a rich historical data set to quantify tree growth within plots located at Danbulla National Park and State Forest on the Atherton Tableland. Leaf traits were collected from trees that have exhibited fast or slow growth over the last ~50 yr of measurement. Leaf traits were found to be poor predictors of tree growth for trees that have entered the canopy; however, for sub-canopy trees, leaf traits had a stronger association with growth rates. Leaf phosphorus concentrations were the strongest predictor of Periodic Annual Increment (PAI) for trees growing within the sub-canopy, with trees with higher leaf phosphorus levels showing a higher PAI. Sub-canopy tree leaves also exhibited stronger trade-offs between leaf traits and adhere to theoretical predictions more so than for canopy trees. We suggest that, in order for leaf traits to be more applicable to reforestation, size dependence of traits and growth relationships need to be more carefully considered, particularly when reforestation practitioners assign mean trait values to tropical tree species from multiple canopy strata. © 2018 by the Ecological Society of America.

Leaf dynamics and profitability in wild strawberries.

PubMed

Jurik, Thomas W; Chabot, Brian F

1986-05-01

Leaf dynamics and carbon gain were evaluated for two species of wild strawberry, Fragaria virginiana and F. vesca. Five populations on sites representing a gradient of successional regrowth near Ithaca, N.Y., U.S.A., were studied for two or three years each. A computer-based model of plant growth and CO 2 exchange combined field studies of leaf biomass dynamics with previously-determined gas exchange rates to estimate carbon balances of leaves and whole plants in different environments.Leaves were produced throughout the growing season, although there was usually a decline in rate of leaf-production in mid-summer. Leaves produced in late spring had the largest area and longest lifespan (except for overwintering leaves produced in the fall). Specific Leaf Weight (SLW) varied little with time of leaf production, but differed greatly among populations; SLW increased with amount of light received in each habitat. The population in the most open habitat had the least seasonal variation in all leaf characters. F. vesca produced lighter, longer-lived leaves than F. virginiana.Simulations showed that age had the largest effect on leaf carbon gain in high-light environments; water stress and temperature had lesser effects. Leaf carbon gain in lowlight environments was relatively unaffected by age and environmental factors other than light. Leaves in high-light environments had the greatest lifetime profit and the greatest ratio of profit to cost. Increasing lifespan by 1/3 increased profit by 80% in low-light leaves and 50% in high-light leaves. Increasing the number of days during which the leaf had the potential to exhibit high photosynthetic rate in response to high light led to little change in profit of low-light leaves while increasing profit of high-light leaves by 49%.

Fluorescent Staining of Tea Pathogenic Fungi in Tea Leaves Using Fluorescein-labeled Lectin

NASA Astrophysics Data System (ADS)

Yamada, Kengo; Yoshida, Katsuyuki; Sonoda, Ryoichi

Fluorochrome-labeled lectin, fluorescein conjugated wheat germ agglutinin (F-WGA) was applied to stain tea pathogenic fungi in tea leaf tissue. Infected leaves were fixed and decolorized with a mixture of ethanol and acetic acid, and cleared with 10% KOH for whole mount before staining with F-WGA. Hyphae of Pestalotiopsis longiseta, Pseudocercospora ocellata, Botrytis cinerea and Colletotrichum theae-sinensis fluoresced brightly in whole mount and sectioned samples of infected leaf tissue. In browned tissue, hyphae did not fluoresce frequently in whole mount sample. Autofluorescence of leaf tissue was strong in browned tissue of sections, it was removed by 10% KOH treatment before staining. Penetration hyphae of C. theae-sinensis in cell wall of trichome and hyphae in basal part of trichome did not fluoresced frequently. In whole mount samples of tea leaf infected with Exobasidium vexans and E. reticulatum, hymenia appeared on leaf surface fluoresced, but hyphae in leaf tissue did not fluoresce. In sectioned samples, hyphae fluoresced brightly when sections were treated with 10% KOH before staining.

Sensitivity of Photosynthesis in a C4 Plant, Maize, to Heat Stress

PubMed Central

Crafts-Brandner, Steven J.; Salvucci, Michael E.

2002-01-01

Our objective was to determine the sensitivity of components of the photosynthetic apparatus of maize (Zea mays), a C4 plant, to high temperature stress. Net photosynthesis (Pn) was inhibited at leaf temperatures above 38°C, and the inhibition was much more severe when the temperature was increased rapidly rather than gradually. Transpiration rate increased progressively with leaf temperature, indicating that inhibition was not associated with stomatal closure. Nonphotochemical fluorescence quenching (qN) increased at leaf temperatures above 30°C, indicating increased thylakoid energization even at temperatures that did not inhibit Pn. Compared with CO2 assimilation, the maximum quantum yield of photosystem II (Fv/Fm) was relatively insensitive to leaf temperatures up to 45°C. The activation state of phosphoenolpyruvate carboxylase decreased marginally at leaf temperatures above 40°C, and the activity of pyruvate phosphate dikinase was insensitive to temperature up to 45°C. The activation state of Rubisco decreased at temperatures exceeding 32.5°C, with nearly complete inactivation at 45°C. Levels of 3-phosphoglyceric acid and ribulose-1,5-bisphosphate decreased and increased, respectively, as leaf temperature increased, consistent with the decrease in Rubisco activation. When leaf temperature was increased gradually, Rubisco activation acclimated in a similar manner as Pn, and acclimation was associated with the expression of a new activase polypeptide. Rates of Pn calculated solely from the kinetics of Rubisco were remarkably similar to measured rates if the calculation included adjustment for temperature effects on Rubisco activation. We conclude that inactivation of Rubisco was the primary constraint on the rate of Pn of maize leaves as leaf temperature increased above 30°C. PMID:12177490

Nutrients stimulate leaf breakdown rates and detritivore biomass: Bottom-up effects via heterotrophic pathways

USGS Publications Warehouse

Greenwood, J.L.; Rosemond, A.D.; Wallace, J.B.; Cross, W.F.; Weyers, H.S.

2007-01-01

Most nutrient enrichment studies in aquatic systems have focused on autotrophic food webs in systems where primary producers dominate the resource base. We tested the heterotrophic response to long-term nutrient enrichment in a forested, headwater stream. Our study design consisted of 2 years of pretreatment data in a reference and treatment stream and 2 years of continuous nitrogen (N) + phosphorus addition to the treatment stream. Studies were conducted with two leaf species that differed in initial C:N, Rhododendron maximum (rhododendron) and Acer rubrum (red maple). We determined the effects of nutrient addition on detrital resources (leaf breakdown rates, litter C:N and microbial activity) and tested whether nutrient enrichment affected macroinvertebrate consumers via increased biomass. Leaf breakdown rates were ca. 1.5 and 3?? faster during the first and second years of enrichment, respectively, in the treatment stream for both leaf types. Microbial respiration rates of both leaf types were 3?? higher with enrichment, and macroinvertebrate biomass associated with leaves increased ca. 2-3?? with enrichment. The mass of N in macroinvertebrate biomass relative to leaves tended to increase with enrichment up to 6?? for red maple and up to 44?? for rhododendron leaves. Lower quality (higher C:N) rhododendron leaves exhibited greater changes in leaf nutrient content and macroinvertebrate response to nutrient enrichment than red maple leaves, suggesting a unique response by different leaf species to nutrient enrichment. Nutrient concentrations used in this study were moderate and equivalent to those in streams draining watersheds with altered land use. Thus, our results suggest that similarly moderate levels of enrichment may affect detrital resource quality and subsequently lead to altered energy and nutrient flow in detrital food webs. ?? 2006 Springer-Verlag.

Enemy release and plant invasion: patterns of defensive traits and leaf damage in Hawaii.

PubMed

Funk, Jennifer L; Throop, Heather L

2010-04-01

Invasive species may be released from consumption by their native herbivores in novel habitats and thereby experience higher fitness relative to native species. However, few studies have examined release from herbivory as a mechanism of invasion in oceanic island systems, which have experienced particularly high loss of native species due to the invasion of non-native animal and plant species. We surveyed putative defensive traits and leaf damage rates in 19 pairs of taxonomically related invasive and native species in Hawaii, representing a broad taxonomic diversity. Leaf damage by insects and pathogens was monitored in both wet and dry seasons. We found that native species had higher leaf damage rates than invasive species, but only during the dry season. However, damage rates across native and invasive species averaged only 2% of leaf area. Native species generally displayed high levels of structural defense (leaf toughness and leaf thickness, but not leaf trichome density) while native and invasive species displayed similar levels of chemical defenses (total phenolics). A defense index, which integrated all putative defense traits, was significantly higher for native species, suggesting that native species may allocate fewer resources to growth and reproduction than do invasive species. Thus, our data support the idea that invasive species allocate fewer resources to defense traits, allowing them to outperform native species through increased growth and reproduction. While strong impacts of herbivores on invasion are not supported by the low damage rates we observed on mature plants, population-level studies that monitor how herbivores influence recruitment, mortality, and competitive outcomes are needed to accurately address how herbivores influence invasion in Hawaii.

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.

Water use in forest canopy black cherry trees and its relationship to leaf gas exchange and environment

Treesearch

B. J. Joyce; K. C. Steiner; J. M. Skelly

1996-01-01

Models of canopy gas exchange are needed to connect leaf-level measurement to higher scales. Because of the correspondence between leaf gas exchange and water use, it may be possible to predict variation in leaf gas exchange at the canopy level by monitoring rates of branch water use.

Hydraulic conductance as well as nitrogen accumulation plays a role in the higher rate of leaf photosynthesis of the most productive variety of rice in Japan

PubMed Central

Taylaran, Renante D.; Adachi, Shunsuke; Ookawa, Taiichiro; Usuda, Hideaki; Hirasawa, Tadashi

2011-01-01

An indica variety Takanari is known as one of the most productive rice varieties in Japan and consistently produces 20–30% heavier dry matter during ripening than Japanese commercial varieties in the field. The higher rate of photosynthesis of individual leaves during ripening has been recognized in Takanari. By using pot-grown plants under conditions of minimal mutual shading, it was confirmed that the higher rate of leaf photosynthesis is responsible for the higher dry matter production after heading in Takanari as compared with a japonica variety, Koshihikari. The rate of leaf photosynthesis and shoot dry weight became larger in Takanari after the panicle formation and heading stages, respectively, than in Koshihikari. Roots grew rapidly in the panicle formation stage until heading in Takanari compared with Koshihikari. The higher rate of leaf photosynthesis in Takanari resulted not only from the higher content of leaf nitrogen, which was caused by its elevated capacity for nitrogen accumulation, but also from higher stomatal conductance. When measured under light-saturated conditions, stomatal conductance was already decreased due to the reduction in leaf water potential in Koshihikari even under conditions of a relatively small difference in leaf–air vapour pressure difference. In contrast, the higher stomatal conductance was supported by the maintenance of higher leaf water potential through the higher hydraulic conductance in Takanari with the larger area of root surface. However, no increase in root hydraulic conductivity was expected in Takanari. The larger root surface area of Takanari might be a target trait in future rice breeding for increasing dry matter production. PMID:21527630

Consumption and utilization of experimentally altered corn by southern armyworm: Iron, nitrogen, and cyclic hydroxamates.

PubMed

Manuwoto, S; Scriber, J M

1985-11-01

The effects of differential leaf water, leaf nitrogen and cyclic hydroxamate (DIMBOA) concentrations in corn seedlings were analyzed for a polyphagous insect, the southern armyworm (Spodoptera eridania Cram.). Six different combinations of nutrients and allelochemicals [DIMBOA = 2,4-dihydroxy-7-methoxy(2H)-benzoxazin-3(4H)-one] were generated using two corn genotypes (WF9 and CI3IA) and three fertility regimes (complete nutrient, Fe-deficient, and N-deficient solutions) in the University Biotron. Poorest larval growth was observed in the low-nitrogen treatments (1.2% and 1.7% leaf N) and was the result of both low consumption rates and high metabolic costs (low efficiency of conversion of digested food, ECD). Fastest growth rates were observed forthe larvae fed leaves from the high-nitrogen treatments (4.6% and 4.4% leaf N). It is noteworthy that these treatments also contained the highest concentration of cyclic hydroxamates, which are generally believed to be the primary defensive chemicals mediating resistance against the European corn borer,Ostrinia nubilalis (Hubner). If these hydroxamates do have any deleterious or costly effects (perhaps accounting for a large portion of metabolic expenditures), the high digestibility of the leaf tissue and the increased consumption rates more than compensate, resulting in rapid growth (growth rate = consumption rate × approximate digestibility × efficiency of conversion of the digested food). These studies illustrate that variation in key nutrients and allelochemicals within a single plant species (Zea mays L.) may have significantly different effects upon various potential leaf-chewing caterpillars, such as these armyworms versus corn borers (which cannot handle the cyclic hydroxamates, even if provided with young nutritious leaf tissues).

Growth and Photosynthetic Responses to Salinity of the Salt-marsh Shrub Atriplex portulacoides

PubMed Central

Redondo-Gómez, Susana; Mateos-Naranjo, Enrique; Davy, Anthony J.; Fernández-Muñoz, Francisco; Castellanos, Eloy M.; Luque, Teresa; Figueroa, M. Enrique

2007-01-01

Background and Aims Atriplex (Halimione) portulacoides is a halophytic, C3 shrub. It is virtually confined to coastal salt marshes, where it often dominates the vegetation. The aim of this study was to investigate its growth responses to salinity and the extent to which these could be explained by photosynthetic physiology. Methods The responses of young plants to salinity in the range 0–700 mol m−3 NaCl were investigated in a glasshouse experiment. The performance of plants was examined using classical growth analysis, measurements of gas exchange (infrared gas analysis), determination of chlorophyll fluorescence characteristics (modulated fluorimeter) and photosynthetic pigment concentrations; total ash, sodium, potassium and nitrogen concentrations, and relative water content were also determined. Key Results Plants accumulated Na+ approximately in proportion to external salinity. Salt stimulated growth up to an external concentration of 200 mol m−3 NaCl and some growth was maintained at higher salinities. The main determinant of growth response to salinity was unit leaf rate. This was itself reflected in rates of CO2 assimilation, which were not affected by 200 mol m−3 but were reduced at higher salinities. Reductions in net photosynthetic rate could be accounted for largely by lower stomatal conductance and intercellular CO2 concentration. Apart from possible effects of osmotic shock at the beginning of the experiment, salinity did not have any adverse effect on photosystem II (PSII). Neither the quantum efficiency of PSII (ΦPSII) nor the chlorophyll fluorescence ratio (Fv/Fm) were reduced by salinity, and lower mid-day values recovered by dawn. Mid-day Fv/Fm was in fact depressed more at low external sodium concentration, by the end of the experiment. Conclusions The growth responses of the hygro-halophyte A. portulacoides to salinity appear largely to depend on changes in its rate of photosynthetic gas exchange. Photosynthesis appears to be limited mainly through stomatal conductance and hence intercellular CO2 concentration, rather than by effects on PSII; moderate salinity might stimulate carboxylation capacity. This is in contrast to more extreme halophytes, for which an ability to maintain leaf area can partially offset declining rates of carbon assimilation at high salinity. PMID:17684026

[Effects of hyposalinity in Thalassia testudinum (Hydrocharitaceae) from Parque Nacional Morrocoy, Venezuela].

PubMed

Pérez, D; Galindo, L

2000-12-01

The year 1996 had a high pluviosity in Morrocoy National Park (western coastal zone, Venezuela) and low salinity in December 1996 affected the seagrass beds, dominated by Thalassia testudinum. Patches without T. testudinum were observed in localities of the park that used to have very dense populations of this plant. Sampling was done at Las Luisas to determine leaf productivity, turnover rate, short shoot density and relative biomass of plant sections, in order to compare with data obtained in September 1996, previous to the event. Green leaves, roots and rhizomes were the most affected parts. Mean green leaf biomass decreased in January and February 1997 to 5% of the plant's total biomass; mean root biomass decreased in March to 40% and mean rhi zome biomass decreased in February to 30%. The density of the active short shoots decreased to a minimum in February, but in April it reached a value similar to that of September 1996. The density of the inactive short shoots decreased to a minimum in March, and they dissappeared in April, matching the increasing density of the active short shoots between these two months. In February 1997, 56% of the inactive short shoots showed evidence of leaf initiation. In January 1997 the leaf productivity and turnover rate values (2.72 +/- 0.35 g/m2/d and 2.15% leaf DW/d) were similar to the annual mean previously determined from Las Luisas (2.35 +/- 0.72 g/m2/d and 1.96% leaf DW/d). Nevertheless, the values of productivity and turnover rate detected at Las Luisas in April 1997 (4.88 +/- 2.14 g/m2/d and 4.66% leaf DW/d) were higher than those values previously reported for this location. In response to the mortality episode, the leaf productivity and turnover rate of T. testudinum increased and the leaf initiation was activated in the inactive short shoots.

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 elevated atmospheric CO2 concentration on leaf dark respiration of Xanthium strumarium in light and in darkness

PubMed Central

Wang, Xianzhong; Lewis, James D.; Tissue, David T.; Seemann, Jeffrey R.; Griffin, Kevin L.

2001-01-01

Leaf dark respiration (R) is an important component of plant carbon balance, but the effects of rising atmospheric CO2 on leaf R during illumination are largely unknown. We studied the effects of elevated CO2 on leaf R in light (RL) and in darkness (RD) in Xanthium strumarium at different developmental stages. Leaf RL was estimated by using the Kok method, whereas leaf RD was measured as the rate of CO2 efflux at zero light. Leaf RL and RD were significantly higher at elevated than at ambient CO2 throughout the growing period. Elevated CO2 increased the ratio of leaf RL to net photosynthesis at saturated light (Amax) when plants were young and also after flowering, but the ratio of leaf RD to Amax was unaffected by CO2 levels. Leaf RN was significantly higher at the beginning but significantly lower at the end of the growing period in elevated CO2-grown plants. The ratio of leaf RL to RD was used to estimate the effect of light on leaf R during the day. We found that light inhibited leaf R at both CO2 concentrations but to a lesser degree for elevated (17–24%) than for ambient (29–35%) CO2-grown plants, presumably because elevated CO2-grown plants had a higher demand for energy and carbon skeletons than ambient CO2-grown plants in light. Our results suggest that using the CO2 efflux rate, determined by shading leaves during the day, as a measure for leaf R is likely to underestimate carbon loss from elevated CO2-grown plants. PMID:11226264

Effects of elevated atmospheric CO2 concentration on leaf dark respiration of Xanthium strumarium in light and in darkness.

PubMed

Wang, X; Lewis, J D; Tissue, D T; Seemann, J R; Griffin, K L

2001-02-27

Leaf dark respiration (R) is an important component of plant carbon balance, but the effects of rising atmospheric CO(2) on leaf R during illumination are largely unknown. We studied the effects of elevated CO(2) on leaf R in light (R(L)) and in darkness (R(D)) in Xanthium strumarium at different developmental stages. Leaf R(L) was estimated by using the Kok method, whereas leaf R(D) was measured as the rate of CO(2) efflux at zero light. Leaf R(L) and R(D) were significantly higher at elevated than at ambient CO(2) throughout the growing period. Elevated CO(2) increased the ratio of leaf R(L) to net photosynthesis at saturated light (A(max)) when plants were young and also after flowering, but the ratio of leaf R(D) to A(max) was unaffected by CO(2) levels. Leaf R(N) was significantly higher at the beginning but significantly lower at the end of the growing period in elevated CO(2)-grown plants. The ratio of leaf R(L) to R(D) was used to estimate the effect of light on leaf R during the day. We found that light inhibited leaf R at both CO(2) concentrations but to a lesser degree for elevated (17-24%) than for ambient (29-35%) CO(2)-grown plants, presumably because elevated CO(2)-grown plants had a higher demand for energy and carbon skeletons than ambient CO(2)-grown plants in light. Our results suggest that using the CO(2) efflux rate, determined by shading leaves during the day, as a measure for leaf R is likely to underestimate carbon loss from elevated CO(2)-grown plants.

Early competition shapes maize whole-plant development in mixed stands

PubMed Central

Evers, Jochem B.

2014-01-01

Mixed cropping is practised widely in developing countries and is gaining increasing interest for sustainable agriculture in developed countries. Plants in intercrops grow differently from plants in single crops, due to interspecific plant interactions, but adaptive plant morphological responses to competition in mixed stands have not been studied in detail. Here the maize (Zea mays) response to mixed cultivation with wheat (Triticum aestivum) is described. Evidence is provided that early responses of maize to the modified light environment in mixed stands propagate throughout maize development, resulting in different phenotypes compared with pure stands. Photosynthetically active radiation (PAR), red:far-red ratio (R:FR), leaf development, and final organ sizes of maize grown in three cultivation systems were compared: pure maize, an intercrop with a small distance (25cm) between maize and wheat plants, and an intercop with a large distance (44cm) between the maize and the wheat. Compared with maize in pure stands, maize in the mixed stands had lower leaf and collar appearance rates, increased blade and sheath lengths at low ranks and smaller sizes at high ranks, increased blade elongation duration, and decreased R:FR and PAR at the plant base during early development. Effects were strongest in the treatment with a short distance between wheat and maize strips. The data suggest a feedback between leaf initiation and leaf emergence at the plant level and coordination between blade and sheath growth at the phytomer level. A conceptual model, based on coordination rules, is proposed to explain the development of the maize plant in pure and mixed stands. PMID:24307719

Soil fauna and leaf species, but not species diversity, affect initial soil erosion in a subtropical forest plantation

NASA Astrophysics Data System (ADS)

Seitz, Steffen; Goebes, Philipp; Assmann, Thorsten; Schuldt, Andreas; Scholten, Thomas

2017-04-01

In subtropical parts of China, high rainfall intensities cause continuous soil losses and thereby provoke severe harms to ecosystems. In woodlands, it is not the tree canopy, but mostly an intact forest floor that provides protection from soil erosion. Although the protective role of leaf litter covers against soil losses is known for a long time, little research has been conducted on the processes involved. For instance, the role of different leaf species and leaf species diversity has been widely disregarded. Furthermore, the impact of soil meso- and macrofauna within the litter layer on soil losses remains unclear. To investigate how leaf litter species and diversity as well as soil meso- and macrofauna affect sediment discharge in a subtropical forest ecosystem, a field experiment was carried out in Xingangshan, Jiangxi Province, PR China (BEF China). A full-factorial random design with 96 micro-scale runoff plots and seven domestic leaf species in three diversity levels and a bare ground feature were established. Erosion was initiated with a rainfall simulator. This study confirms that leaf litter cover generally protects forest soils from water erosion (-82 % sediment discharge on leaf covered plots compared to bare plots) and this protection is gradually removed as the litter layer decomposes. Different leaf species showed variable impacts on sediment discharge and thus erosion control. This effect can be related to different leaf habitus, leaf decomposition rates and food preferences of litter decomposing meso- and macrofauna. In our experiment, runoff plots with leaf litter from Machilus thunbergii in monoculture showed the highest sediment discharge (68.0 g m-2), whereas plots with Cyclobalanopsis glauca in monoculture showed the smallest rates (7.9 g m-2). At the same time, neither leaf species diversity, nor functional diversity showed any significant influence, only a negative trend could be observed. Nevertheless, the protective effect of the leaf litter layer was influenced by the presence (or absence) of soil meso- and macrofauna. Fauna presence increased soil erosion rates significantly by 58 %. It was assumed that this faunal effect arose from arthropods loosening and processing the soil surface as well as fragmenting and decomposing the protecting leaf litter covers. Thus, effects of this fauna group on sediment discharge have to be considered in soil erosion experiments.

Removal of nutrient limitations in forest gaps enhances growth rate and resistance to cavitation in subtropical canopy tree species differing in shade tolerance.

PubMed

Villagra, Mariana; Campanello, Paula I; Montti, Lia; Goldstein, Guillermo

2013-03-01

A 4-year fertilization experiment with nitrogen (N) and phosphorus (P) was carried out in natural gaps of a subtropical forest in northeastern Argentina. Saplings of six dominant canopy species differing in shade tolerance were grown in five control and five N + P fertilized gaps. Hydraulic architectural traits such as wood density, the leaf area to sapwood area ratio (LA : SA), vulnerability to cavitation (P50) and specific and leaf-specific hydraulic conductivity were measured, as well as the relative growth rate, specific leaf area (SLA) and percentage of leaf damage by insect herbivores. Plant growth rates and resistance to drought-induced embolisms increased when nutrient limitations were removed. On average, the P50 of control plants was -1.1 MPa, while the P50 of fertilized plants was -1.6 MPa. Wood density and LA : SA decreased with N + P additions. A trade-off between vulnerability to cavitation and efficiency of water transport was not observed. The relative growth rate was positively related to the total leaf surface area per plant and negatively related to LA : SA, while P50 was positively related to SLA across species and treatments. Plants with higher growth rates and higher total leaf area in fertilized plots were able to avoid hydraulic dysfunction by becoming less vulnerable to cavitation (more negative P50). Two high-light-requiring species exhibited relatively low growth rates due to heavy herbivore damage. Contrary to expectations, shade-tolerant plants with relatively high resistance to hydraulic dysfunction and reduced herbivory damage were able to grow faster. These results suggest that during the initial phase of sapling establishment in gaps, species that were less vulnerable to cavitation and exhibited reduced herbivory damage had faster realized growth rates than less shade-tolerant species with higher potential growth rates. Finally, functional relationships between hydraulic traits and growth rate across species and treatments were maintained regardless of soil nutrient status.

Modeling development and quantitative trait mapping reveal independent genetic modules for leaf size and shape.

PubMed

Baker, Robert L; Leong, Wen Fung; Brock, Marcus T; Markelz, R J Cody; Covington, Michael F; Devisetty, Upendra K; Edwards, Christine E; Maloof, Julin; Welch, Stephen; Weinig, Cynthia

2015-10-01

Improved predictions of fitness and yield may be obtained by characterizing the genetic controls and environmental dependencies of organismal ontogeny. Elucidating the shape of growth curves may reveal novel genetic controls that single-time-point (STP) analyses do not because, in theory, infinite numbers of growth curves can result in the same final measurement. We measured leaf lengths and widths in Brassica rapa recombinant inbred lines (RILs) throughout ontogeny. We modeled leaf growth and allometry as function valued traits (FVT), and examined genetic correlations between these traits and aspects of phenology, physiology, circadian rhythms and fitness. We used RNA-seq to construct a SNP linkage map and mapped trait quantitative trait loci (QTL). We found genetic trade-offs between leaf size and growth rate FVT and uncovered differences in genotypic and QTL correlations involving FVT vs STPs. We identified leaf shape (allometry) as a genetic module independent of length and width and identified selection on FVT parameters of development. Leaf shape is associated with venation features that affect desiccation resistance. The genetic independence of leaf shape from other leaf traits may therefore enable crop optimization in leaf shape without negative effects on traits such as size, growth rate, duration or gas exchange. © 2015 The Authors. New Phytologist © 2015 New Phytologist Trust.

Physiological Effects of Kaolin Applications in Well-irrigated and Water-stressed Walnut and Almond Trees

PubMed Central

ROSATI, A.; METCALF, S. G.; BUCHNER, R. P.; FULTON, A. E.; LAMPINEN, B. D.

2006-01-01

• Background and Aims Kaolin applications have been used to mitigate the negative effects of water and heat stress on plant physiology and productivity with variable results, ranging from increased to decreased yields and photosynthetic rates. The mechanisms of action of kaolin applications are not clear: although the increased albedo reduces leaf temperature and the consequent heat stress, it also reduces the light available for photosynthesis, possibly offsetting benefits of lower temperature. The objective of this study was to investigate which of these effects are prevalent and under which conditions. • Methods A 6 % kaolin suspension was applied on well-irrigated and water-stressed walnut (Juglans regia) and almond (Prunus dulcis) trees. Water status (i.e. stem water potential, Ψs), gas exchange (i.e. light-saturated CO2 assimilation rate, Amax; stomatal conductance, gs), leaf temperature (Tl) and physiological relationships in treated and control trees were then measured and compared. • Key Results In both species, kaolin did not affect the daily course of Ψs whereas it reduced Amax by 1–4 μmol CO2 m–2 s–1 throughout the day in all combinations of species and irrigation treatments. Kaolin did not reduce gs in any situation. Consequently, intercellular CO2 concentration (Ci) was always greater in treated trees than in controls, suggesting that the reduction of Amax with kaolin was not due to stomatal limitations. Kaolin reduced leaf temperature (Tl) by about 1–3 °C and leaf-to-air vapour pressure difference (VPDl) by about 0·1–0·7 kPa. Amax was lower at all values of gs, Tl and VPDl in kaolin-treated trees. Kaolin affected the photosynthetic response to the photosynthetically active radiation (PAR) in almond leaves: kaolin-coated leaves had similar dark respiration rates and light-saturated photosynthesis, but a higher light compensation point and lower apparent quantum yield, while the photosynthetic light-response curve saturated at higher PAR. When these parameters were used to model the photosynthetic response curve to PAR, it was estimated that the kaolin film allowed 63 % of the incident PAR to reach the leaf. • Conclusions The main effect of kaolin application was the reduction, albeit minor, of photosynthesis, which appeared to be related to the shading of the leaves. The reduction in Tl and VPDl with kaolin did not suffice to mitigate the adverse effects of heat and water stress on Amax. PMID:16735404

The influence of leaf anatomy on the internal light environment and photosynthetic electron transport rate: exploration with a new leaf ray tracing model.

PubMed

Xiao, Yi; Tholen, Danny; Zhu, Xin-Guang

2016-11-01

Leaf photosynthesis is determined by biochemical properties and anatomical features. Here we developed a three-dimensional leaf model that can be used to evaluate the internal light environment of a leaf and its implications for whole-leaf electron transport rates (J). This model includes (i) the basic components of a leaf, such as the epidermis, palisade and spongy tissues, as well as the physical dimensions and arrangements of cell walls, vacuoles and chloroplasts; and (ii) an efficient forward ray-tracing algorithm, predicting the internal light environment for light of wavelengths between 400 and 2500nm. We studied the influence of leaf anatomy and ambient light on internal light conditions and J The results show that (i) different chloroplasts can experience drastically different light conditions, even when they are located at the same distance from the leaf surface; (ii) bundle sheath extensions, which are strips of parenchyma, collenchyma or sclerenchyma cells connecting the vascular bundles with the epidermis, can influence photosynthetic light-use efficiency of leaves; and (iii) chloroplast positioning can also influence the light-use efficiency of leaves. Mechanisms underlying leaf internal light heterogeneity and implications of the heterogeneity for photoprotection and for the convexity of the light response curves are discussed. © The Author 2016. Published by Oxford University Press on behalf of the Society for Experimental Biology.

Time-course of programmed cell death during leaf senescence in Eucommia ulmoides.

PubMed

Cao, Jing; Jiang, Feng; Sodmergen; Cui, Keming

2003-02-01

Leaves of Eucommia ulmoidesOliv. harvested between April to November were examined for programmed cell death (PCD) during growth and senescence. Leaves developed in April, becoming fully expanded in late May, remaining unchanged until November when they started to dehisce. Falling leaves retained a green color. Our results showed that (1) mesophyll cells gradually reduced their nuclei from September to November, (2) positive TUNEL signals appeared on the nuclei from August, (3) ladder-like DNA fragmentation occurred in September and October, and (4) a 20-kDa Ca(2+)-dependent DNase appeared in these same months. In fallen leaves, intact mesophyll cell nuclei could not be detected, but a few cells around the vascular bundle had nuclei. Therefore, (1) programmed cell death (PCD) of leaf cells occurred in the leaves of E. ulmoides, (2) the progress of mesophyll cell PCD lasted for more than 2 months, and (3) PCD of leaf cells was asynchronous in natural senescing leaves.

Diurnal depression in leaf hydraulic conductance at ambient and elevated [CO2] and reveals anisohydric water management in field-grown soybean

USDA-ARS?s Scientific Manuscript database

Diurnal cycles of photosynthesis and water use in field-grown soybean (Glycine max) are tied to light intensity and vapor pressure deficit (VPD). At high mid-day VPD, transpiration rates can lead to a decline in leaf water potential ('leaf) if leaf hydraulic conductance (Kleaf) is insufficient to su...

Plant-pathogen interactions: leaf physiology alterations in poplars infected with rust (Melampsora medusae).

PubMed

Gortari, Fermín; Guiamet, Juan José; Graciano, Corina

2018-06-01

Rust produced by Melampsora sp. is considered one of the most relevant diseases in poplar plantations. Growth reduction in poplar plantations takes place because rust, like other pathogens, alters leaf physiology. There is not a complete evaluation of several of the physiological traits that can be affected by rust at leaf level. Therefore, the aim of this work was to evaluate, in an integrative way and in the same pathosystem, which physiological processes are affected when Populus deltoides Bartr. ex Marsh. leaves are infected by rust (Melampsora medusae Thümen). Leaves of two clones with different susceptibility to rust were analyzed. Field and pot experiments were performed, and several physiological traits were measured in healthy and infected leaves. We conclude that rust affects leaf mesophyll integrity, and so water movement in the leaf in liquid phase is affected. As a consequence, gas exchange is reduced, affecting both carbon fixation and transpiration. However, there is an increase in respiration rate, probably due to plant and fungal respiration. The increase in respiration rate is important in the reduction of net photosynthetic rate, but also some damage in the photosynthetic apparatus limits leaf capacity to fix carbon. The decrease in chlorophyll content would start later and seems not to explain the reduction in net photosynthetic rate. Both clones, although they have different susceptibility to rust, are affected in the same physiological mechanisms.

Isotopic composition of transpiration and rates of change in leaf water isotopologue storage in response to environmental variables.

PubMed

Simonin, Kevin A; Roddy, Adam B; Link, Percy; Apodaca, Randy; Tu, Kevin P; Hu, Jia; Dawson, Todd E; Barbour, Margaret M

2013-12-01

During daylight hours, the isotope composition of leaf water generally approximates steady-state leaf water isotope enrichment model predictions. However, until very recently there was little direct confirmation that isotopic steady-state (ISS) transpiration in fact exists. Using isotope ratio infrared spectroscopy (IRIS) and leaf gas exchange systems we evaluated the isotope composition of transpiration and the rate of change in leaf water isotopologue storage (isostorage) when leaves were exposed to variable environments. In doing so, we developed a method for controlling the absolute humidity entering the gas exchange cuvette for a wide range of concentrations without changing the isotope composition of water vapour. The measurement system allowed estimation of (18)O enrichment both at the evaporation site and for bulk leaf water, in the steady state and the non-steady state. We show that non-steady-state effects dominate the transpiration isoflux even when leaves are at physiological steady state. Our results suggest that a variable environment likely prevents ISS transpiration from being achieved and that this effect may be exacerbated by lengthy leaf water turnover times due to high leaf water contents. © 2013 John Wiley & Sons Ltd.

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.

The Use of Leaf Functional Traits for Modeling the Timing and Rate of Canopy Development

NASA Astrophysics Data System (ADS)

Savoy, P.; Mackay, D. S.

2015-12-01

Leaves vary in their habit, with some being short lived and possessing high intrinsic photosynthetic rates and others being long lived with lower photosynthetic capacity. Longer lived leaves will thus tend to cost more to produce and be able to assimilate carbon over a longer period of time. The timing and seasonality of forest canopies is a cost benefit strategy for the exploitation of favorable environmental conditions and avoidance of unfavorable conditions. Because of the selective pressure for plants to gather a return on leaf investment in relation to their leaf habit we propose that there is a relationship between plant functional traits and the timing and rate of canopy development. In a recent study it was shown that errors in predicted canopy dynamics could be reduced via a single parameter (τ) which modified the timing and rate of canopy development (Savoy & Mackay 2015). If τ is related to underlying mechanisms of plant physiology then it should vary predictably. To test this we will first examine the relationship between τ and observable biophysical variables which vary in ecologically meaningful ways. Then we will develop a model based on leaf traits which will regulate the timing and rate at which vegetation reaches peak rates of assimilation. The model will then be tested at eddy covariance sites which span a range environmental conditions. Preliminary results demonstrate a strong relationship (R2 = 0.58) between estimated values of τ and leaf carbon to nitrogen ratio, which is important for representing the costs of leaf construction and nitrogen investment into photosynthetic machinery of leaves. By developing a canopy seasonality model based on plant functional traits and rooted in the framework of leaf economics it is possible to have a more flexible and generalized model. Such a model will be more adept at making predictions under novel environmental conditions than purely correlative empirical models.

A unique approach to demonstrating that apical bud temperature specifically determines leaf initiation rate in the dicot Cucumis sativus.

PubMed

Savvides, Andreas; Dieleman, Janneke A; van Ieperen, Wim; Marcelis, Leo F M

2016-04-01

Leaf initiation rate is largely determined by the apical bud temperature even when apical bud temperature largely deviates from the temperature of other plant organs. We have long known that the rate of leaf initiation (LIR) is highly sensitive to temperature, but previous studies in dicots have not rigorously demonstrated that apical bud temperature controls LIR independent of other plant organs temperature. Many models assume that apical bud and leaf temperature are the same. In some environments, the temperature of the apical bud, where leaf initiation occurs, may differ by several degrees Celsius from the temperature of other plant organs. In a 28-days study, we maintained temperature differences between the apical bud and the rest of the individual Cucumis sativus plants from -7 to +8 °C by enclosing the apical buds in transparent, temperature-controlled, flow-through, spheres. Our results demonstrate that LIR was completely determined by apical bud temperature independent of other plant organs temperature. These results emphasize the need to measure or model apical bud temperatures in dicots to improve the prediction of crop development rates in simulation models.

Influence of light and shoot development stage on leaf photosynthesis and carbohydrate status during the adventitious root formation in cuttings of Corylus avellana L.

PubMed Central

Tombesi, Sergio; Palliotti, Alberto; Poni, Stefano; Farinelli, Daniela

2015-01-01

Adventitious root formation in plant cuttings is influenced by many endogenous and environmental factors. Leaf photosynthesis during rooting of leafy cuttings in hard to root species can contribute to supply carbohydrates to the intensive metabolic processes related to adventious root formation. Light intensity during rooting is artificially kept low to decrease potential cutting desiccation, but can be limiting for photosynthetic activity. Furthermore, leafy cuttings collected from different part of the shoot can have a different ability to fuel adventitious root formation in cutting stem. The aim of this work was to determine the role of leaf photosynthesis on adventitious root formation in hazelnut (Corylus avellana L) (a hard-to-root specie) leafy cuttings and to investigate the possible influence of the shoot developmental stage on cutting rooting and survival in the post-rooting phase. Cutting rooting was closely related to carbohydrate content in cutting stems during the rooting process. Cutting carbohydrate status was positively influenced by leaf photosynthesis during rooting. Non-saturating light exposure of leafy cuttings can contribute to improve photosynthetic activity of leafy cuttings. Collection of cuttings from different part of the mother shoots influenced rooting percentage and this appear related to the different capability to concentrate soluble sugars in the cutting stem during rooting. Adventitious root formation depend on the carbohydrate accumulation at the base of the cutting. Mother shoot developmental stage and leaf photosynthesis appear pivotal factors for adventitious roots formation. PMID:26635821

Biophysical constraints on leaf expansion in a tall conifer.

Treesearch

Fredrick C. Meinzer; Barbara J. Bond; Jennifer A. Karanian

2008-01-01

The physiological mechanisms responsible for reduced extension growth as trees increase in height remain elusive. We evaluated biophysical constraints on leaf expansion in old-growth Douglas-fir (Psuedotsuga menziesii (Mirb.) Franco) trees. Needle elongation rates, plastic and elastic extensibility, bulk leaf water, (L...

Leaf and fine root carbon stocks and turnover are coupled across Arctic ecosystems.

PubMed

Sloan, Victoria L; Fletcher, Benjamin J; Press, Malcolm C; Williams, Mathew; Phoenix, Gareth K

2013-12-01

Estimates of vegetation carbon pools and their turnover rates are central to understanding and modelling ecosystem responses to climate change and their feedbacks to climate. In the Arctic, a region containing globally important stores of soil carbon, and where the most rapid climate change is expected over the coming century, plant communities have on average sixfold more biomass below ground than above ground, but knowledge of the root carbon pool sizes and turnover rates is limited. Here, we show that across eight plant communities, there is a significant positive relationship between leaf and fine root turnover rates (r(2) = 0.68, P < 0.05), and that the turnover rates of both leaf (r(2) = 0.63, P < 0.05) and fine root (r(2) = 0.55, P < 0.05) pools are strongly correlated with leaf area index (LAI, leaf area per unit ground area). This coupling of root and leaf dynamics supports the theory of a whole-plant economics spectrum. We also show that the size of the fine root carbon pool initially increases linearly with increasing LAI, and then levels off at LAI = 1 m(2) m(-2), suggesting a functional balance between investment in leaves and fine roots at the whole community scale. These ecological relationships not only demonstrate close links between above and below-ground plant carbon dynamics but also allow plant carbon pool sizes and their turnover rates to be predicted from the single readily quantifiable (and remotely sensed) parameter of LAI, including the possibility of estimating root data from satellites. © 2013 John Wiley & Sons Ltd.

Leaf miner-induced morphological, physiological and molecular changes in mangrove plant Avicennia marina (Forsk.) Vierh.

PubMed

Chen, Juan; Shen, Zhi-Jun; Lu, Wei-Zhi; Liu, Xiang; Wu, Fei-Hua; Gao, Gui-Feng; Liu, Yi-Ling; Wu, Chun-Sheng; Yan, Chong-Ling; Fan, Hang-Qing; Zhang, Yi-Hui; Zheng, Hai-Lei; Tsai, Chung-Jui

2017-01-31

Avicennia marina (Forsk.) Vierh is a widespread mangrove species along the southeast coasts of China. Recently, the outbreak of herbivorous insect, Phyllocnistis citrella Stainton, a leaf miner, have impacted on the growth of A. marina. Little is reported about the responses of A. marina to leaf miner infection at the biochemical, physiological and molecular levels. Here, we reported the responses of A. marina to leaf miner infection from the aspects of leaf structure, photosynthesis, and antioxidant system and miner responsive genes expression. A. marina leaves attacked by the leaf miner exhibited significant decreases in chlorophyll, carbon and nitrogen contents, as well as a decreased photosynthetic rate. Scanning and transmission electron microscopic observations revealed that the leaf miner only invaded the upper epidermis and destroyed the epidermal cell, which lead to the exposure of salt glands. In addition, the chloroplasts of mined leaves (ML) were swollen and the thylakoids degraded. The maximal net photosynthetic rate, stomatal conductance (Gs), carboxylation efficiency (CE), dark respiration (Rd), light respiration (Rp) and quantum yields (AQE) significantly decreased in the ML, whereas the light saturation point (Lsp), light compensation point (Lcp), water loss and CO2 compensation point (Г) increased in the ML. Moreover, chlorophyll fluorescence features also had been changed by leaf miner attacks. Interestingly, higher generation rate of O2ˉ· and lower antioxidant enzyme expression in the mined portion (MP) were found; on the contrary, higher H2O2 level and higher antioxidant enzyme expression in the non-mined portion (NMP) were revealed, implying that the NMP may be able to sense that the leaf miner attacks had happened in the MP of the A. marina leaf via H2O2 signaling. Besides, the protein expression of glutathione S-transferase (GST) and the glutathione (GSH) content were increased in the ML. In addition, insect resistance-related gene expression such as chitinase 3, RAR1, topless and PIF3 had significantly increased in the ML. Taken together, our data suggest that leaf miners could significantly affect leaf structure, photosynthesis, the antioxidant system and miner responsive gene expression in A. marina leaves.

Variations of leaf longevity in tropical moist forests predicted by a trait-driven carbon optimality model

DOE PAGES

Xu, Xiangtao; Medvigy, David; Wright, Stuart Joseph; ...

2017-07-04

Leaf longevity (LL) varies more than 20-fold in tropical evergreen forests, but it remains unclear how to capture these variations using predictive models. Current theories of LL that are based on carbon optimisation principles are challenging to quantitatively assess because of uncertainty across species in the ‘ageing rate:’ the rate at which leaf photosynthetic capacity declines with age. Here in this paper, we present a meta-analysis of 49 species across temperate and tropical biomes, demonstrating that the ageing rate of photosynthetic capacity is positively correlated with the mass-based carboxylation rate of mature leaves. We assess an improved trait-driven carbon optimalitymore » model with in situLL data for 105 species in two Panamanian forests. Additionally, we show that our model explains over 40% of the cross-species variation in LL under contrasting light environment. Collectively, our results reveal how variation in LL emerges from carbon optimisation constrained by both leaf structural traits and abiotic environment.« less

Variations of leaf longevity in tropical moist forests predicted by a trait-driven carbon optimality model

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

Xu, Xiangtao; Medvigy, David; Wright, Stuart Joseph

Leaf longevity (LL) varies more than 20-fold in tropical evergreen forests, but it remains unclear how to capture these variations using predictive models. Current theories of LL that are based on carbon optimisation principles are challenging to quantitatively assess because of uncertainty across species in the ‘ageing rate:’ the rate at which leaf photosynthetic capacity declines with age. Here in this paper, we present a meta-analysis of 49 species across temperate and tropical biomes, demonstrating that the ageing rate of photosynthetic capacity is positively correlated with the mass-based carboxylation rate of mature leaves. We assess an improved trait-driven carbon optimalitymore » model with in situLL data for 105 species in two Panamanian forests. Additionally, we show that our model explains over 40% of the cross-species variation in LL under contrasting light environment. Collectively, our results reveal how variation in LL emerges from carbon optimisation constrained by both leaf structural traits and abiotic environment.« less

Effects of UV-B radiation on growth, photosynthesis, UV-B-absorbing compounds and NADP-malic enzyme in bean (Phaseolus vulgaris L.) grown under different nitrogen conditions.

PubMed

Pinto, M E; Casati, P; Hsu, T P; Ku, M S; Edwards, G E

1999-02-01

The effects of UV-B radiation on growth, photosynthesis, UV-B-absorbing compounds and NADP-malic enzyme have been examined in different cultivars of Phaseolous vulgaris L. grown under 1 and 12 mM nitrogen. Low nitrogen nutrition reduces chlorophyll and soluble protein contents in the leaves and thus the photosynthesis rate and dry-matter accumulation. Chlorophyll, soluble protein and Rubisco contents and photosynthesis rate are not significantly altered by ambient levels of UV-B radiation (17 microW m-2, 290-320 nm, 4 h/day for one week). Comparative studies show that under high nitrogen, UV-B radiation slightly enhances leaf expansion and dry-matter accumulation in cultivar Pinto, but inhibits these parameters in Vilmorin. These results suggest that the UV-B effect on growth is mediated through leaf expansion, which is particularly sensitive to UV-B, and that Pinto is more tolerant than Vilmorin. The effect of UV-B radiation on UV-B-absorbing compounds and on NADP-malic enzyme (NADP-ME) activity is also examined. Both UV-B radiation and low-nitrogen nutrition enhance the content of UV-B-absorbing compounds, and among the three cultivars used, Pinto exhibits the highest increases and Arroz the lowest. The same trend is observed for the specific activity and content of NADP-ME. On a leaf-area basis, the amount of UV-B-absorbing compounds is highly correlated with the enzyme activity (r2 = 0.83), suggesting that NADP-ME plays a key role in biosynthesis of these compounds. Furthermore, the higher sensitivity of Vilmorin than Pinto to UV-B radiation appears to be related to the activity of NADP-ME and the capacity of the plants to accumulate UV-B-absorbing compounds.

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.

Gynaikothrips uzeli (Thysanoptera: Phlaeothripidae) , New Record From Tartous, Syria

PubMed Central

Yaseen Ali, Ali

2014-01-01

Abstract The weeping fig thrips Gynaikothrips uzeli Zimmermann (Thysanoptera: Phlaeothripidae) is newly recorded for the first time in the leaf galls of the weeping fig tree Ficus benjamina L. (Rosales: Moraceae) in the coastal area of Tartous, Syria. The thrips caused purplish red spots on the leaf surface of the host plant and the leaves curl. G. uzeili appears to be successfully adapted to this area. PMID:25527584

Exploiting the Genetic Diversity of Maize Using a Combined Metabolomic, Enzyme Activity Profiling, and Metabolic Modeling Approach to Link Leaf Physiology to Kernel Yield

PubMed Central

Yesbergenova-Cuny, Zhazira; Simons, Margaret; Chardon, Fabien; Armengaud, Patrick; Quilleré, Isabelle; Cukier, Caroline; Gibon, Yves; Limami, Anis M.; Nicolas, Stéphane; Brulé, Lenaïg; Lea, Peter J.; Maranas, Costas D.; Hirel, Bertrand

2017-01-01

A combined metabolomic, biochemical, fluxomic, and metabolic modeling approach was developed using 19 genetically distant maize (Zea mays) lines from Europe and America. Considerable differences were detected between the lines when leaf metabolic profiles and activities of the main enzymes involved in primary metabolism were compared. During grain filling, the leaf metabolic composition appeared to be a reliable marker, allowing a classification matching the genetic diversity of the lines. During the same period, there was a significant correlation between the genetic distance of the lines and the activities of enzymes involved in carbon metabolism, notably glycolysis. Although large differences were observed in terms of leaf metabolic fluxes, these variations were not tightly linked to the genome structure of the lines. Both correlation studies and metabolic network analyses allowed the description of a maize ideotype with a high grain yield potential. Such an ideotype is characterized by low accumulation of soluble amino acids and carbohydrates in the leaves and high activity of enzymes involved in the C4 photosynthetic pathway and in the biosynthesis of amino acids derived from glutamate. Chlorogenates appear to be important markers that can be used to select for maize lines that produce larger kernels. PMID:28396554

Synthetic Graphene Oxide Leaf for Solar Desalination with Zero Liquid Discharge.

PubMed

Finnerty, Casey; Zhang, Lei; Sedlak, David L; Nelson, Kara L; Mi, Baoxia

2017-10-17

Water vapor generation through sunlight harvesting and heat localization by carbon-based porous thin film materials holds great promise for sustainable, energy-efficient desalination and water treatment. However, the applicability of such materials in a high-salinity environment emphasizing zero-liquid-discharge brine disposal has not been studied. This paper reports the characterization and evaporation performance of a nature-inspired synthetic leaf made of graphene oxide (GO) thin film material, which exhibited broadband light absorption and excellent stability in high-salinity water. Under 0.82-sun illumination (825 W/m 2 ), a GO leaf floating on water generated steam at a rate of 1.1 L per m 2 per hour (LMH) with a light-to-vapor energy conversion efficiency of 54%, while a GO leaf lifted above water in a tree-like configuration generated steam at a rate of 2.0 LMH with an energy efficiency of 78%. The evaporation rate increased with increasing light intensity and decreased with increasing salinity. During a long-term evaporation experiment with a 15 wt % NaCl solution, the GO leaf demonstrated stable performance despite gradual and eventually severe accumulation of salt crystals on the leaf surface. Furthermore, the GO leaf can be easily restored to its pristine condition by simply scraping off salt crystals from its surface and rinsing with water. Therefore, the robust high performance and relatively low fabrication cost of the synthetic GO leaf could potentially unlock a new generation of desalination technology that can be entirely solar-powered and achieve zero liquid discharge.

The influence of leaf size and shape on leaf thermal dynamics: does theory hold up under natural conditions?

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

Leigh, A.; Sevanto, Sanna Annika; Close, J. D.

Laboratory studies on artificial leaves suggest that leaf thermal dynamics are strongly influenced by the two-dimensional size and shape of leaves and associated boundary layer thickness. Hot environments are therefore said to favour selection for small, narrow or dissected leaves. Empirical evidence from real leaves under field conditions is scant and traditionally based on point measurements that do not capture spatial variation in heat load. Here in this study, we used thermal imagery under field conditions to measure the leaf thermal time constant (τ) in summer and the leaf-to-air temperature difference (ΔT) and temperature range across laminae (T range) duringmore » winter, autumn and summer for 68 Proteaceae species. We investigated the influence of leaf area and margin complexity relative to effective leaf width (w e), the latter being a more direct indicator of boundary layer thickness. Normalized difference of margin complexity had no or weak effects on thermal dynamics, but w e strongly predicted τ and ΔT, whereas leaf area influenced T range. Unlike artificial leaves, however, spatial temperature distribution in large leaves appeared to be governed largely by structural variation. Therefore, we agree that small size, specifically we, has adaptive value in hot environments but not with the idea that thermal regulation is the primary evolutionary driver of leaf dissection.« less

The influence of leaf size and shape on leaf thermal dynamics: does theory hold up under natural conditions?

DOE PAGES

Leigh, A.; Sevanto, Sanna Annika; Close, J. D.; ...

2016-11-05

Laboratory studies on artificial leaves suggest that leaf thermal dynamics are strongly influenced by the two-dimensional size and shape of leaves and associated boundary layer thickness. Hot environments are therefore said to favour selection for small, narrow or dissected leaves. Empirical evidence from real leaves under field conditions is scant and traditionally based on point measurements that do not capture spatial variation in heat load. Here in this study, we used thermal imagery under field conditions to measure the leaf thermal time constant (τ) in summer and the leaf-to-air temperature difference (ΔT) and temperature range across laminae (T range) duringmore » winter, autumn and summer for 68 Proteaceae species. We investigated the influence of leaf area and margin complexity relative to effective leaf width (w e), the latter being a more direct indicator of boundary layer thickness. Normalized difference of margin complexity had no or weak effects on thermal dynamics, but w e strongly predicted τ and ΔT, whereas leaf area influenced T range. Unlike artificial leaves, however, spatial temperature distribution in large leaves appeared to be governed largely by structural variation. Therefore, we agree that small size, specifically we, has adaptive value in hot environments but not with the idea that thermal regulation is the primary evolutionary driver of leaf dissection.« less

The Impacts of Phosphorus Deficiency on the Photosynthetic Electron Transport Chain1[OPEN

PubMed Central

2018-01-01

Phosphorus (P) is an essential macronutrient, and P deficiency limits plant productivity. Recent work showed that P deficiency affects electron transport to photosystem I (PSI), but the underlying mechanisms are unknown. Here, we present a comprehensive biological model describing how P deficiency disrupts the photosynthetic machinery and the electron transport chain through a series of sequential events in barley (Hordeum vulgare). P deficiency reduces the orthophosphate concentration in the chloroplast stroma to levels that inhibit ATP synthase activity. Consequently, protons accumulate in the thylakoids and cause lumen acidification, which inhibits linear electron flow. Limited plastoquinol oxidation retards electron transport to the cytochrome b6f complex, yet the electron transfer rate of PSI is increased under steady-state growth light and is limited under high-light conditions. Under P deficiency, the enhanced electron flow through PSI increases the levels of NADPH, whereas ATP production remains restricted and, hence, reduces CO2 fixation. In parallel, lumen acidification activates the energy-dependent quenching component of the nonphotochemical quenching mechanism and prevents the overexcitation of photosystem II and damage to the leaf tissue. Consequently, plants can be severely affected by P deficiency for weeks without displaying any visual leaf symptoms. All of the processes in the photosynthetic machinery influenced by P deficiency appear to be fully reversible and can be restored in less than 60 min after resupply of orthophosphate to the leaf tissue. PMID:29540590

Vasorelaxation induced by common edible tropical plant extracts in isolated rat aorta and mesenteric vascular bed.

PubMed

Runnie, I; Salleh, M N; Mohamed, S; Head, R J; Abeywardena, M Y

2004-06-01

In this study, the vasodilatory actions of nine edible tropical plant extracts were investigated. Ipomoea batatas (sweet potato leaf), Piper betle (betel leaf), Anacardium occidentale (cashew leaf), Gynandropsis gynandra (maman leaf), Carica papaya (papaya leaf), and Mentha arvensis (mint leaf) extracts exhibited more than 50% relaxing effect on aortic ring preparations, while Piper betle and Cymbopogon citratus (lemongrass stalk) showed comparable vasorelaxation on isolated perfused mesenteric artery preparation. The vascular effect on the aortic ring preparations were mainly endothelium-dependent, and mediated by nitric oxide (NO) as supported by the inhibition of action in the presence of N(omega)-nitro-L-arginine (NOLA), an nitric oxide synthase (NOS) inhibitor, or by the removal of endothelium. In contrast, vasodilatory actions in resistance vessels (perfused mesenteric vascular beds) appear to involve several biochemical mediators, including NO, prostanoids, and endothelium-dependent hyperpolarizing factors (EDHFs). Total phenolic contents and antioxidant capacities varied among different extracts and found to be independent of vascular relaxation effects. This study demonstrates that many edible plants common in Asian diets to possess potential health benefits, affording protection at the vascular endothelium level.

A Functional Characterisation of a Wide Range of Cover Crop Species: Growth and Nitrogen Acquisition Rates, Leaf Traits and Ecological Strategies

PubMed Central

Tribouillois, Hélène; Fort, Florian; Cruz, Pablo; Charles, Raphaël; Flores, Olivier; Garnier, Eric; Justes, Eric

2015-01-01

Cover crops can produce ecosystem services during the fallow period, as reducing nitrate leaching and producing green manure. Crop growth rate (CGR) and crop nitrogen acquisition rate (CNR) can be used as two indicators of the ability of cover crops to produce these services in agrosystems. We used leaf functional traits to characterise the growth strategies of 36 cover crops as an approach to assess their ability to grow and acquire N rapidly. We measured specific leaf area (SLA), leaf dry matter content (LDMC), leaf nitrogen content (LNC) and leaf area (LA) and we evaluated their relevance to characterise CGR and CNR. Cover crop species were positioned along the Leaf Economics Spectrum (LES), the SLA-LDMC plane, and the CSR triangle of plant strategies. LA was positively correlated with CGR and CNR, while LDMC was negatively correlated with CNR. All cover crops could be classified as resource-acquisitive species from their relative position on the LES and the SLA-LDMC plane. Most cover crops were located along the Competition/Ruderality axis in the CSR triangle. In particular, Brassicaceae species were classified as very competitive, which was consistent with their high CGR and CNR. Leaf functional traits, especially LA and LDMC, allowed to differentiate some cover crops strategies related to their ability to grow and acquire N. LDMC was lower and LNC was higher in cover crop than in wild species, pointing to an efficient acquisitive syndrome in the former, corresponding to the high resource availability found in agrosystems. Combining several leaf traits explained approximately half of the CGR and CNR variances, which might be considered insufficient to precisely characterise and rank cover crop species for agronomic purposes. We hypothesised that may be the consequence of domestication process, which has reduced the range of plant strategies and modified the leaf trait syndrome in cultivated species. PMID:25789485

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.

VARIABILITY AND CHARACTER ASSOCIATION IN ROSE COLOURED LEADWORT (PLUMBAGO ROSEA Linn.)

PubMed Central

Kurian, Alice; Anitha, C.A.; Nybe, E.V.

2001-01-01

Forty five plumbago rosea accessions collected from different parts of Kerala state were evaluated for variability in morphological and yield related characters and plumbagin content. Highly significant variation was evident for all the characters studied except leaf size indicating wide variability in the accessions. Accessions PR 25 and PR 31 appear to be promising with respect to root yield and high plumbagin content. Character association revelated significant and positive correlation of all the characters except leaf size with yield. Hence, selection of high yielding types could easily be done based on visual characters expressing more vegetative growth but with reduced leaf size. PMID:22557037

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.

Scaling leaf respiration with nitrogen and phosphorus in tropical forests across two continents.

PubMed

Rowland, Lucy; Zaragoza-Castells, Joana; Bloomfield, Keith J; Turnbull, Matthew H; Bonal, Damien; Burban, Benoit; Salinas, Norma; Cosio, Eric; Metcalfe, Daniel J; Ford, Andrew; Phillips, Oliver L; Atkin, Owen K; Meir, Patrick

2017-05-01

Leaf dark respiration (R dark ) represents an important component controlling the carbon balance in tropical forests. Here, we test how nitrogen (N) and phosphorus (P) affect R dark and its relationship with photosynthesis using three widely separated tropical forests which differ in soil fertility. R dark was measured on 431 rainforest canopy trees, from 182 species, in French Guiana, Peru and Australia. The variation in R dark was examined in relation to leaf N and P content, leaf structure and maximum photosynthetic rates at ambient and saturating atmospheric CO 2 concentration. We found that the site with the lowest fertility (French Guiana) exhibited greater rates of R dark per unit leaf N, P and photosynthesis. The data from Australia, for which there were no phylogenetic overlaps with the samples from the South American sites, yielded the most distinct relationships of R dark with the measured leaf traits. Our data indicate that no single universal scaling relationship accounts for variation in R dark across this large biogeographical space. Variability between sites in the absolute rates of R dark and the R dark  : photosynthesis ratio were driven by variations in N- and P-use efficiency, which were related to both taxonomic and environmental variability. © 2016 The Authors. New Phytologist © 2016 New Phytologist Trust.

Autumnal leaf senescence in Miscanthus × giganteus and leaf [N] differ by stand age

PubMed Central

Boersma, Nicholas N.; Dohleman, Frank G.; Miguez, Fernando E.; Heaton, Emily A.

2015-01-01

Poor first winter survival in Miscanthus × giganteus has been anecdotally attributed to incomplete first autumn senescence, but these assessments never paired first-year with older M. × giganteus in side-by-side trials to separate the effect of weather from stand age. Here CO2 assimilation rate (A), photosystem II efficiency (ΦPSII), and leaf N concentration ([N]) were used to directly compare senescence in first, second, and third-year stands of M. × giganteus. Three M. × giganteus fields were planted with eight plots, one field each in 2009, 2010, and 2011. To quantify autumnal leaf senescence of plants within each stand age, photosynthetic and leaf [N] measurements were made twice weekly from early September until a killing frost. Following chilling events (daily temperature averages below 10 °C), photosynthetic rates in first year plants rebounded to a greater degree than those in second- and third-year plants. By the end of the growing season, first-year M. × giganteus had A and ΦPSII rates up to 4 times greater than third-year M. × giganteus, while leaf [N] was up to 2.4 times greater. The increased photosynthetic capability and leaf N status in first-year M. × giganteus suggests that the photosynthetic apparatus was not dismantled before a killing frost, thus potentially limiting nutrient translocation, and may explain why young M. × giganteus stands do not survive winter when older stands do. Because previous senescence research has primarily focused on annual or woody species, our results suggest that M. × giganteus may be an interesting herbaceous perennial system to investigate the interactive effects of plant ageing and nutrient status on senescence and may highlight management strategies that could potentially increase winter survival rates in first-year stands. PMID:25873682

Relative growth rate in phylogenetically related deciduous and evergreen woody species.

PubMed

Antúnez, Isabel; Retamosa, Emilio C; Villar, Rafael

2001-07-01

Relative growth rate (RGR) and other growth parameters were studied in eight pairs of closely related deciduous and evergreen species (within the same genus or family). The main objective of this study was to test the association between leaf turnover rate and RGR, specific leaf area (SLA, leaf area/leaf dry weight) and other growth variables. Plants were grown for 6 months in a greenhouse under favourable water and nutrient conditions. Variation in RGR among the 16 woody species was due mainly to differences in morphological parameters such as leaf area ratio (LAR, whole plant area/whole plant dry weight) and SLA). However, temporal variation in RGR within species was due mainly to variation in net assimilation rate. When phylogeny was not taken into account, analyses showed that deciduous species grew faster than evergreens. In contrast, when phylogeny was taken into account, the data analysis showed that a faster RGR is not consistently associated with the deciduous habit (in five pairs it was, but in the other three it was not). The faster growth of the deciduous trees (in the five positive contrasts) could be explained by their higher LAR and higher SLA relative to evergreens. The lack of differences in RGR between deciduous and evergreens (in three pairs) was due to the higher leaf mass ratio (LMR, leaf dry biomass/total dry biomass) for the evergreens, which offset the higher SLA of the deciduous species, resulting in a similar LAR in both functional groups (LAR=LMR×SLA). Deciduous species had consistently higher SLA than evergreens. We suggest that SLA, more than RGR, could be an important parameter in determining adaptive advantages of deciduous and evergreen species.

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.

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.

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.

An evolutionary perspective on leaf economics: phylogenetics of leaf mass per area in vascular plants

PubMed Central

Flores, Olivier; Garnier, Eric; Wright, Ian J; Reich, Peter B; Pierce, Simon; Dìaz, Sandra; Pakeman, Robin J; Rusch, Graciela M; Bernard-Verdier, Maud; Testi, Baptiste; Bakker, Jan P; Bekker, Renée M; Cerabolini, Bruno E L; Ceriani, Roberta M; Cornu, Guillaume; Cruz, Pablo; Delcamp, Matthieu; Dolezal, Jiri; Eriksson, Ove; Fayolle, Adeline; Freitas, Helena; Golodets, Carly; Gourlet-Fleury, Sylvie; Hodgson, John G; Brusa, Guido; Kleyer, Michael; Kunzmann, Dieter; Lavorel, Sandra; Papanastasis, Vasilios P; Pérez-Harguindeguy, Natalia; Vendramini, Fernanda; Weiher, Evan

2014-01-01

In plant leaves, resource use follows a trade-off between rapid resource capture and conservative storage. This “worldwide leaf economics spectrum” consists of a suite of intercorrelated leaf traits, among which leaf mass per area, LMA, is one of the most fundamental as it indicates the cost of leaf construction and light-interception borne by plants. We conducted a broad-scale analysis of the evolutionary history of LMA across a large dataset of 5401 vascular plant species. The phylogenetic signal in LMA displayed low but significant conservatism, that is, leaf economics tended to be more similar among close relatives than expected by chance alone. Models of trait evolution indicated that LMA evolved under weak stabilizing selection. Moreover, results suggest that different optimal phenotypes evolved among large clades within which extremes tended to be selected against. Conservatism in LMA was strongly related to growth form, as were selection intensity and phenotypic evolutionary rates: woody plants showed higher conservatism in relation to stronger stabilizing selection and lower evolutionary rates compared to herbaceous taxa. The evolutionary history of LMA thus paints different evolutionary trajectories of vascular plant species across clades, revealing the coordination of leaf trait evolution with growth forms in response to varying selection regimes. PMID:25165520

The Influence of Leaf Fall and Organic Carbon Availability on Nitrogen Cycling in a Headwater Stream

NASA Astrophysics Data System (ADS)

Thomas, S. A.; Kristin, A.; Doyle, B.; Goodale, C. L.; Gurwick, N. P.; Lepak, J.; Kulkari, M.; McIntyre, P.; McCalley, C.; Raciti, S.; Simkin, S.; Warren, D.; Weiss, M.

2005-05-01

The study of allochthonous carbon has a long and distinguished history in stream ecology. Despite this legacy, relatively little is known regarding the influence of leaf litter on nutrient dynamics. We conducted 15N-NO3 tracer additions to a headwater stream in upstate New York before and after autumn leaf fall to assess the influence of leaf litter on nitrogen spiraling. In addition, we amended the stream with labile dissolved organic carbon (as acetate) midway through each experiment to examine whether organic carbon availability differentially stimulated nitrogen cycling. Leaf standing stocks increased from 53 to 175 g dry mass m-2 and discharge more than tripled (6 to 20 L s-1) between the pre- and post-leaf fall period. In contrast, nitrate concentration fell from approximately 50 to less then 10 ug L-1. Despite higher discharge, uptake length was shorter following leaf fall under both ambient (250 and 72 m, respectively) and DOC amended (125 and 45 m) conditions. Uptake velocity increased dramatically following leaf fall, despite a slight decline in the areal uptake rate. Dissolved N2 gas samples were also collected to estimate denitrification rates under each experimental condition. The temporal extent of increased nitrogen retention will also be explored.

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...

Interspecific and environmentally induced variation in foliar dark respiration among eighteen southeastern deciduous tree species

Treesearch

Katherine A. Mitchell; Paul V. Bolstad; James M. Vose

1999-01-01

We measured variations in leaf dark respiration rate (Rd) and leaf nitrogen (N) across species, canopy light environment, and elevation for 18 co-occurring deciduous hardwood species in the Southern Appalachian Mountains of Western North Carolina. Our overall objective was to estimate leaf...

Transport and coordination in the coupled soil-root-xylem-phloem leaf system

NASA Astrophysics Data System (ADS)

Huang, C. W.; Katul, G. G.; Pockman, W.; Litvak, M. E.; Domec, J. C.; Palmroth, S.

2016-12-01

In response to varying environmental conditions, stomatal pores act as biological valves that dynamically adjust their size thereby determining the rate of CO2 assimilation and water loss (i.e., transpiration) to the dry atmosphere. Although the significance of this biotic control on gas exchange is rarely disputed, representing parsimoniously all the underlying mechanisms responsible for stomatal kinetics remain a subject of some debate. It has been conjectured that stomatal control in seed plants (i.e., angiosperm and gymnosperm) represents a compromise between biochemical demand for CO2 and prevention of excessive water loss. This view has been amended at the whole-plant level, where xylem hydraulics and sucrose transport efficiency in phloem appear to impose additional constraints on gas exchange. If such additional constraints impact stomatal opening and closure, then seed plants may have evolved coordinated photosynthetic-hydraulic-sugar transporting machinery that confers some competitive advantages in fluctuating environmental conditions. Thus, a stomatal optimization model that explicitly considers xylem hydraulics and maximum sucrose transport is developed to explore this coordination in the leaf-xylem-phloem system. The model is then applied to progressive drought conditions. The main findings from the model calculations are that (1) the predicted stomatal conductance from the conventional stomatal optimization theory at the leaf and the newly proposed models converge, suggesting a tight coordination in the leaf-xylem-phloem system; (2) stomatal control is mainly limited by the water supply function of the soil-xylem hydraulic system especially when the water flux through the transpiration stream is significantly larger than water exchange between xylem and phloem; (3) thus, xylem limitation imposed on the supply function can be used to differentiate species with different water use strategy across the spectrum of isohydric to anisohydric behavior. Keywords: leaf-level gas exchange, stomatal control, sucrose transport in phloem, xylem hydraulics

Antibacterial activity of Litsea cubeba (Lauraceae, May Chang) and its effects on the biological response of common carp Cyprinus carpio challenged with Aeromonas hydrophila.

PubMed

Nguyen, H V; Caruso, D; Lebrun, M; Nguyen, N T; Trinh, T T; Meile, J-C; Chu-Ky, S; Sarter, S

2016-08-01

The aims of this study were to characterize the antibacterial activity and the chemotype of Litsea cubeba leaf essential oil (EO) harvested in North Vietnam and to investigate the biological effects induced by the leaf powder on growth, nonspecific immunity and survival of common carp (Cyprinus carpio) challenged with Aeromonas hydrophila. The EO showed the prevalence of linalool (95%, n = 5). It was bactericidal against the majority of tested strains, with minimum inhibitory concentrations ranging from 0·72 to 2·89 mg ml(-1) (Aer. hydrophila, Edwarsiella tarda, Vibrio furnissii, Vibrio parahaemolyticus, Streptococcus garvieae, Escherichia coli, Salmonella Typhimurium). The fish was fed with 0 (control), 2, 4 and 8% leaf powder supplementation diets for 21 days. Nonspecific immunity parameters (lysozyme, haemolytic and bactericidal activities of plasma) were assessed 21 days after feeding period and before the experimental infection. Weight gain, specific growth rate and feed conversion ratio were improved by supplementation of L. cubeba in a dose-related manner, and a significant difference appeared at the highest dose (8%) when compared to the control. The increase in plasma lysozyme was significant for all the treated groups. Haemolysis activity was higher for the groups fed with 4 and 8% plant powder. Antibacterial activity increased significantly for the 8% dose only. Litsea cubeba leaf powder increased nonspecific immunity of carps in dose-related manner. After infection with Aer. hydrophila, survivals of fish fed with 4 and 8% L. cubeba doses were significantly higher than those fed with 2% dose and the control. A range of 4-8% L. cubeba leaf powder supplementation diet (from specific linalool-rich chemotype) can be used in aquaculture to reduce antibiotic burden and impacts of diseases caused by Aer. hydrophila. © 2016 The Society for Applied Microbiology.

Environmental safety to decomposer invertebrates of azadirachtin (neem) as a systemic insecticide in trees to control emerald ash borer.

PubMed

Kreutzweiser, David; Thompson, Dean; Grimalt, Susana; Chartrand, Derek; Good, Kevin; Scarr, Taylor

2011-09-01

The non-target effects of an azadirachtin-based systemic insecticide used for control of wood-boring insect pests in trees were assessed on litter-dwelling earthworms, leaf-shredding aquatic insects, and microbial communities in terrestrial and aquatic microcosms. The insecticide was injected into the trunks of ash trees at a rate of 0.2 gazadirachtin cm(-1) tree diameter in early summer. At the time of senescence, foliar concentrations in most (65%) leaves where at or below detection (<0.01 mg kg(-1) total azadirachtin) and the average concentration among leaves overall at senescence was 0.19 mg kg(-1). Leaves from the azadirachtin-treated trees at senescence were added to microcosms and responses by test organisms were compared to those in microcosms containing leaves from non-treated ash trees (controls). No significant reductions were detected among earthworm survival, leaf consumption rates, growth rates, or cocoon production, aquatic insect survival and leaf consumption rates, and among terrestrial and aquatic microbial decomposition of leaf material in comparison to controls. In a further set of microcosm tests containing leaves from intentional high-dose trees, the only significant, adverse effect detected was a reduction in microbial decomposition of leaf material, and only at the highest test concentration (∼6 mg kg(-1)). Results indicated no significant adverse effects on litter-dwelling earthworms or leaf-shredding aquatic insects at concentrations up to at least 30 × the expected field concentrations at operational rates, and at 6 × expected field concentrations for adverse effects on microbial decomposition. We conclude that when azadirachtin is used as a systemic insecticide in trees for control of insect pests such as the invasive wood-boring beetle, emerald ash borer, resultant foliar concentrations in senescent leaf material are likely to pose little risk of harm to decomposer invertebrates. Crown Copyright © 2011. Published by Elsevier Inc. All rights reserved.

Electron transport efficiency at opposite leaf sides: effect of vertical distribution of leaf angle, structure, chlorophyll content and species in a forest canopy.

PubMed

Mänd, Pille; Hallik, Lea; Peñuelas, Josep; Kull, Olevi

2013-02-01

We investigated changes in chlorophyll a fluorescence from alternate leaf surfaces to assess the intraleaf light acclimation patterns in combination with natural variations in radiation, leaf angles, leaf mass per area (LMA), chlorophyll content (Chl) and leaf optical parameters. Measurements were conducted on bottom- and top-layer leaves of Tilia cordata Mill. (a shade-tolerant sub-canopy species, sampled at heights of 11 and 16 m) and Populus tremula L. (a light-demanding upper canopy species, sampled at canopy heights of 19 and 26 m). The upper canopy species P. tremula had a six times higher PSII quantum yield (Φ(II)) and ratio of open reaction centres (qP), and a two times higher LMA than T. cordata. These species-specific differences were also present when the leaves of both species were in similar light conditions. Leaf adaxial/abaxial fluorescence ratio was significantly larger in the case of more horizontal leaves. Populus tremula (more vertical leaves), had smaller differences in fluorescence parameters between alternate leaf sides compared with T. cordata (more horizontal leaves). However, optical properties on alternate leaf sides showed a larger difference for P. tremula. Intraspecifically, the measured optical parameters were better correlated with LMA than with leaf Chl. Species-specific differences in leaf anatomy appear to enhance the photosynthetic potential of leaf biochemistry by decreasing the interception of excess light in P. tremula and increasing the light absorptance in T. cordata. Our results indicate that intraleaf light absorption gradient, described here as leaf adaxial/abaxial side ratio of chlorophyll a fluorescence, varies significantly with changes in leaf light environment in a multi-layer multi-species tree canopy. However, this variation cannot be described merely as a simple function of radiation, leaf angle, Chl or LMA, and species-specific differences in light acclimation strategies should also be considered.

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

Improved Satellite-based Crop Yield Mapping by Spatially Explicit Parameterization of Crop Phenology

NASA Astrophysics Data System (ADS)

Jin, Z.; Azzari, G.; Lobell, D. B.

2016-12-01

Field-scale mapping of crop yields with satellite data often relies on the use of crop simulation models. However, these approaches can be hampered by inaccuracies in the simulation of crop phenology. Here we present and test an approach to use dense time series of Landsat 7 and 8 acquisitions data to calibrate various parameters related to crop phenology simulation, such as leaf number and leaf appearance rates. These parameters are then mapped across the Midwestern United States for maize and soybean, and for two different simulation models. We then implement our recently developed Scalable satellite-based Crop Yield Mapper (SCYM) with simulations reflecting the improved phenology parameterizations, and compare to prior estimates based on default phenology routines. Our preliminary results show that the proposed method can effectively alleviate the underestimation of early-season LAI by the default Agricultural Production Systems sIMulator (APSIM), and that spatially explicit parameterization for the phenology model substantially improves the SCYM performance in capturing the spatiotemporal variation in maize and soybean yield. The scheme presented in our study thus preserves the scalability of SCYM, while significantly reducing its uncertainty.

Chronic drought stress reduced but not protected Shantung maple (Acer truncatum Bunge) from adverse effects of ozone (O3) on growth and physiology in the suburb of Beijing, China.

PubMed

Li, Li; Manning, William J; Tong, Lei; Wang, Xiaoke

2015-06-01

A two-year experiment exposing Acer truncatum Bunge seedlings to elevated ozone (O3) concentrations above ambient air (AO) and drought stress (DS) was carried out using open-top chambers (OTCs) in a suburb of Beijing in north China in 2012-2013. The results suggested that AO and DS had both significantly reduced leaf mass area (LMA), stomatal conductance (Gs), light saturated photosynthetic rate (Asat) as well as above and below ground biomass at the end of the experiment. It appeared that while drought stress mitigated the expression of foliar injury, LMA, leaf photosynthetic pigments, height growth and basal diameter, due to limited carbon fixation, the O3 - induced reductions in Asat, Gs and total biomass were enhanced 23.7%. 15.5% and 8.1% respectively. These data suggest that when the whole plant was considered that drought under the conditions of this experiment did not protect the Shantung maple seedlings from the effects of O3. Copyright © 2015 Elsevier Ltd. All rights reserved.

More of the same? In situ leaf and root decomposition rates do not vary between 80 native and nonnative deciduous forest species.

PubMed

Jo, Insu; Fridley, Jason D; Frank, Douglas A

2016-01-01

Invaders often have greater rates of production and produce more labile litter than natives. The increased litter quantity and quality of invaders should increase nutrient cycling through faster litter decomposition. However, the limited number of invasive species that have been included in decomposition studies has hindered the ability to generalize their impacts on decomposition rates. Further, previous decomposition studies have neglected roots. We measured litter traits and decomposition rates of leaves for 42 native and 36 nonnative woody species, and those of fine roots for 23 native and 25 nonnative species that occur in temperate deciduous forests throughout the Eastern USA. Among the leaf and root traits that differed between native and invasive species, only leaf nitrogen was significantly associated with decomposition rate. However, native and nonnative species did not differ systematically in leaf and root decomposition rates. We found that among the parameters measured, litter decomposer activity was driven by litter chemical quality rather than tissue density and structure. Our results indicate that litter decomposition rate per se is not a pathway by which forest woody invasive species affect North American temperate forest soil carbon and nutrient processes. © 2015 The Authors. New Phytologist © 2015 New Phytologist Trust.

Ozone and Botrytis interactions in onion-leaf dieback: open-top chamber studies

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

Wukasch, R.T.; Hofstra, G.

1977-09-01

Paired open-top chambers were used to study interactions between Botrytis spp. and ozone in field-grown onions. Charcoal filters removed 35 to 65% of the ambient ozone, resulting in six-fold reduction of onion leaf dieback and a 28% increase in onion yield compared with unfiltered chambers. Symptoms of leaf injury appeared soon after ozone levels exceeded 294 ..mu..g/m/sup 3/ (0.15 ppm) for 4 hr. Lesions caused by Botrytis were few because no dew formed in the chambers. However, when leaves were wetted with foggers, inoculation with mycelial suspensions of B. sauamosa in late August produced significantly more lesions and leaf diebackmore » in the unfiltered chamber. Botrytis squamosa, B. cinerea, B. allii, and several genera of secondary fungi were isolated from these lesions. Botrytis squamosa was recovered from lesions only, whereas B. cinerea and B. allii were associated more generally with onion leaf tissue regardless of lesions. 25 references, 1 figure, 2 tables.« less

Contribution of flavonoids to the overall radical scavenging activity of olive (Olea europaea L.) leaf polar extracts.

PubMed

Goulas, Vlassios; Papoti, Vassiliki T; Exarchou, Vassiliki; Tsimidou, Maria Z; Gerothanassis, Ioannis P

2010-03-24

The contribution of flavonoids to the overall radical scavenging activity of olive leaf polar extracts, known to be good sources of oleuropein related compounds, was examined. Off line and on line HPLC-DPPH(*) assays were employed, whereas flavonoid content was estimated colorimetrically. Individual flavonoid composition was first assessed by RP-HPLC coupled with diode array and fluorescence detectors and verified by LC-MS detection system. Olive leaf was found a robust source of flavonoids regardless sampling parameters (olive cultivar, leaf age or sampling date). Total flavonoids accounted for the 13-27% of the total radical scavenging activity assessed using the on line protocol. Luteolin 7-O-glucoside was one of the dominant scavengers (8-25%). Taking into consideration frequency of appearance the contribution of luteolin (3-13%) was considered important, too. Our findings support that olive leaf, except for oleuropein and related compounds, is also a stable source of bioactive flavonoids.

Composition and Chemical Variability of Ivoirian Xylopia staudtii Leaf Oil.

PubMed

Yapi, Thierry Acafou; Boti, Jean Brice; Ahibo, Antoine Coffy; Sutour, Sylvain; Bighelli, Ange; Casanova, Joseph; Tomi, Félix

2015-06-01

The chemical composition of a leaf oil sample from Ivoirian Xylopia staudtii Engler & Diels (Annonaceae) has been investigated by a combination of chromatographic [GC(RI)] and spectroscopic (GC-MS, 13C NMR) techniques. Thirty-five components that accounted for 91.8% of the whole composition have been identified. The oil composition was dominated by the furanoguaiadienes furanoguaia-1,4-diene (39.0%) and furanoguaia-1,3-diene(7.5%), and by germacrene D (17.5%). The composition of twelve other leaf oil samples demonstrated qualitative homogeneity, but quantitative variability. Indeed, the contents of the major components varied substantially: furanoguaia-1,4-diene (24.7-51.7%) and germacrene D (5.9-24.8%). The composition of X. staudtii leaf oil is close to that of X. rubescens leaf oil but varied drastically from those of the essential oils isolated from other Xylopia species. 13C NMR spectroscopy appeared as a powerful and complementary tool for analysis of sesquiterpene-rich essential oils.

Caffeine biosynthesis and degradation in tea [Camellia sinensis (L.) O. Kuntze] is under developmental and seasonal regulation.

PubMed

Mohanpuria, Prashant; Kumar, Vinay; Joshi, Robin; Gulati, Ashu; Ahuja, Paramvir Singh; Yadav, Sudesh Kumar

2009-10-01

To study caffeine biosynthesis and degradation, here we monitored caffeine synthase gene expression and caffeine and allantoin content in various tissues of four Camellia sinensis (L.) O. Kuntze cultivars during non-dormant (ND) and dormant (D) growth phases. Caffeine synthase expression as well as caffeine content was found to be higher in commercially utilized tissues like apical bud, 1st leaf, 2nd leaf, young stem, and was lower in old leaf during ND compared to D growth phase. Among fruit parts, fruit coats have higher caffeine synthase expression, caffeine content, and allantoin content. On contrary, allantoin content was found lower in the commercially utilized tissues and higher in old leaf. Results suggested that caffeine synthesis and degradation in tea appears to be under developmental and seasonal regulation.

Increased Ethylene Production during Clinostat Experiments May Cause Leaf Epinasty

PubMed Central

Leather, G. R.; Forrence, L. E.; Abeles, F. B.

1972-01-01

Ethylene production from tomato (Lycopersicum esculentum L. cv. Rutgers) plants based on a clinostat doubled during the first 2 hours of rotation. Carbon dioxide blocked the appearance of leaf epinasty normally associated with plants rotated on a clinostat. These results support the idea that epinasty of clinostated plants was due to increased ethylene production and not to the cancellation of the gravitational pull on auxin transport in the petiole. Images PMID:16657920

Effects of drought on leaf gas exchange in an eastern broadleaf deciduous forest

NASA Astrophysics Data System (ADS)

Roman, D. T.; Brzostek, E. R.; Dragoni, D.; Rahman, A. F.; Novick, K. A.; Phillips, R.

2013-12-01

Understanding plant physiological adaptations to drought is critical for predicting changes in ecosystem productivity that result from climate variability and future climate change. From 2011-2013, southern Indiana experienced a late growing season drought in 2011, a severe early season drought in 2012, and a wet growing season in 2013 characterized by an absence of water stress with frequent precipitation and milder temperatures. The 2012 drought was unique due to the severity and early onset drought conditions (compared to the more frequent late season drought) and was characterized by a Palmer Drought severity index below -4 and precipitation totals from May - July that were 70% less than the long-term (2000 - 2010) mean. During the 2012 drought, an 11% decline in net ecosystem productivity relative to the long-term mean was observed at the AmeriFlux tower in Morgan Monroe State Forest despite a growing season that started ~25 days earlier. Thus, the objective of this study is to evaluate species-specific contributions to the canopy-scale response to inter-annual variability in water stress. We investigated differences between tree species in their response to climate variability using weekly leaf gas exchange and leaf water potential measurements during the growing seasons of 2011-2013. We used this unique dataset, collected at the top of the canopy with a 25 m boom lift, to evaluate changes in leaf water status and maximum assimilation capacity in the drought versus non-drought years. The leaf-level physiology of oak (Quercus) species appears to be less sensitive to drought than other species (tulip poplar [Liriodendron tulipifera], sassafras [Sassafras albidum] and sugar maple [Acer saccharum]). Preliminary data shows mean canopy leaf water potential for oaks was 30.5% more negative in May-July 2012 versus the same time period in 2013. During these same periods the rate of C assimilation in oaks was reduced by only 3%, whereas other species were reduced by closer to 10-20% in the drought year. We then assess how assimilation capacity and leaf water potential relate to marginal water use efficiency across species and years. Given that this region is predicted to experience more water stress over the coming decades, these results will inform predictions as to how species composition will drive ecosystem responses to climate variability.

An artificial solar spectrum substantially alters plant development compared with usual climate room irradiance spectra.

PubMed

Hogewoning, Sander W; Douwstra, Peter; Trouwborst, Govert; van Ieperen, Wim; Harbinson, Jeremy

2010-03-01

Plant responses to the light spectrum under which plants are grown affect their developmental characteristics in a complicated manner. Lamps widely used to provide growth irradiance emit spectra which are very different from natural daylight spectra. Whereas specific responses of plants to a spectrum differing from natural daylight may sometimes be predictable, the overall plant response is generally difficult to predict due to the complicated interaction of the many different responses. So far studies on plant responses to spectra either use no daylight control or, if a natural daylight control is used, it will fluctuate in intensity and spectrum. An artificial solar (AS) spectrum which closely resembles a sunlight spectrum has been engineered, and growth, morphogenesis, and photosynthetic characteristics of cucumber plants grown for 13 d under this spectrum have been compared with their performance under fluorescent tubes (FTs) and a high pressure sodium lamp (HPS). The total dry weight of the AS-grown plants was 2.3 and 1.6 times greater than that of the FT and HPS plants, respectively, and the height of the AS plants was 4-5 times greater. This striking difference appeared to be related to a more efficient light interception by the AS plants, characterized by longer petioles, a greater leaf unfolding rate, and a lower investment in leaf mass relative to leaf area. Photosynthesis per leaf area was not greater for the AS plants. The extreme differences in plant response to the AS spectrum compared with the widely used protected cultivation light sources tested highlights the importance of a more natural spectrum, such as the AS spectrum, if the aim is to produce plants representative of field conditions.

Coordination and transport of water and carbohydrates in the coupled soil-root-xylem-phloem leaf system

NASA Astrophysics Data System (ADS)

Katul, Gabriel; Huang, Cheng-Wei

2017-04-01

In response to varying environmental conditions, stomatal pores act as biological valves that dynamically adjust their size thereby determining the rate of CO2 assimilation and water loss (i.e., transpiration) to the atmosphere. Although the significance of this biotic control on gas exchange is rarely disputed, representing parsimoniously all the underlying mechanisms responsible for stomatal kinetics remain a subject of some debate. It has been conjectured that stomatal control in seed plants (i.e., angiosperm and gymnosperm) represents a compromise between biochemical demand for CO2 and prevention of excessive water loss. This view has been amended at the whole-plant level, where xylem hydraulics and sucrose transport efficiency in phloem appear to impose additional constraints on gas exchange. If such additional constraints impact stomatal opening and closure, then seed plants may have evolved coordinated photosynthetic-hydraulic-sugar transporting machinery that confers some competitive advantages in fluctuating environmental conditions. Thus, a stomatal optimization model that explicitly considers xylem hydraulics and maximum sucrose transport is developed to explore this coordination in the leaf-xylem-phloem system. The model is then applied to progressive drought conditions. The main findings from the model calculations are that (1) the predicted stomatal conductance from the conventional stomatal optimization theory at the leaf and the newly proposed models converge, suggesting a tight coordination in the leaf-xylem-phloem system; (2) stomatal control is mainly limited by the water supply function of the soil-xylem hydraulic system especially when the water flux through the transpiration stream is significantly larger than water exchange between xylem and phloem; (3) thus, xylem limitation imposed on the supply function can be used to differentiate species with different water use strategy across the spectrum of isohydric to anisohydric behavior.

Quantitative trait loci controlling leaf appearance and curd initiation of cauliflower in relation to temperature.

PubMed

Hasan, Yaser; Briggs, William; Matschegewski, Claudia; Ordon, Frank; Stützel, Hartmut; Zetzsche, Holger; Groen, Simon; Uptmoor, Ralf

2016-07-01

QTL regions on chromosomes C06 and C09 are involved in temperature dependent time to curd induction in cauliflower. Temperature is the main environmental factor influencing curding time of cauliflower (Brassica oleracea var. botrytis). Temperatures above 20-22 °C inhibit development towards curding even in many summer cultivars. To identify quantitative trait loci (QTL) controlling curding time and its related traits in a wide range of different temperature regimes from 12 to 27 °C, a doubled haploid (DH) mapping population segregating for curding time was developed and days to curd initiation (DCI), leaf appearance rate (LAR), and final leaf number (FLN) were measured. The population was genotyped with 176 single nucleotide polymorphism (SNP) markers. Composite interval mapping (CIM) revealed repeatedly detected QTL for DCI on C06 and C09. The estimated additive effect increased at high temperatures. Significant QTL × environment interactions (Q × E) for FLN and DCI on C06 and C09 suggest that these hotspot regions have major influences on temperature mediated curd induction. 25 % of the DH lines did not induce curds at temperatures higher than 22 °C. Applying a binary model revealed a QTL with LOD >15 on C06. Nearly all lines carrying the allele of the reliable early maturing parental line (PL) on that locus induced curds at high temperatures while only half of the DH lines carrying the allele of the unreliable PL reached the generative phase during the experiment. Large variation in LAR was observed. QTL for LAR were detected repeatedly in several environments on C01, C04 and C06. Negative correlations between LAR and DCI and QTL co-localizations on C04 and C06 suggest that LAR has also effects on development towards curd induction.

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.

Effects of inert dust on olive (Olea europaea L.) leaf physiological para.

PubMed

Nanos, George D; Ilias, Ilias F

2007-05-01

Cement factories are major pollutants for the surrounding areas. Inert dust deposition has been found to affect photosynthesis, stomatal functioning and productivity. Very few studies have been conducted on the effects of cement kiln dust on the physiology of perennial fruit crops. Our goal was to study some cement dust effects on olive leaf physiology.effects on olive leaf physiology. On Cement kiln dust has been applied periodically since April 2003 onto olive leaves. Cement dust accumulation and various leaf physiological parameters were evaluated early in July 2003. Measurements were also taken on olive trees close to the cement factory. Leaf dry matter content and specific leaf weight increased with leaf age and dust content. Cement dust decreased leaf total chlorophyll content and chlorophyll a/chlorophyll b ratio. As a result, photosynthetic rate and quantum yield decreased. In addition, transpiration rate slightly decreased, stomatal conductance to H2O and CO2 movement decreased, internal CO2 concentration remained constant and leaf temperature increased. The changes in chlorophyll are possibly due to shading and/or photosystem damage. The changes in stomatal functioning were possibly due to dust accumulation between the peltates or othe effects on stomata. Dust (in this case from a cement kiln) seems to cause substantial changes to leaf physiology, possibly leading to reduced olive productivity. Avoidance of air contamination from cement factories by using available technology should be examined together with any possible methodologies to reduce plant tissue contamination from cement dust. Longterm effects of dust (from cement kiln or other sources) on olive leaf, plant productivity and nutritional quality of edible parts could be studied for conclusive results on dust contamination effects to perennial crops.

Within-species patterns challenge our understanding of the causes and consequences of trait variation with implications for trait-based models

NASA Astrophysics Data System (ADS)

Anderegg, L. D.; Berner, L. T.; Badgley, G.; Hillerislambers, J.; Law, B. E.

2017-12-01

Functional traits could facilitate ecological prediction by provide scale-free tools for modeling ecosystem function. Yet much of their utility lies in three key assumptions: 1) that global patterns of trait covariation are the result of universal trade-offs independent of taxonomic scale, so empirical trait-trait relationships can be used to constrain vegetation models 2) that traits respond predictably to environmental gradients and can therefore be reliably quantified to parameterize models and 3) that well sampled traits influence productivity. We use an extensive dataset of within-species leaf trait variation in North American conifers combined with global leaf trait datasets to test these assumptions. We examine traits central to the `leaf economics spectrum', and quantify patterns of trait variation at multiple taxonomic scales. We also test whether site environment explains geographic trait variation within conifers, and ask whether foliar traits explain geographic variation in relative growth rates. We find that most leaf traits vary primarily between rather than within species globally, but that a large fraction of within-PFT trait variation is within-species. We also find that some leaf economics spectrum relationships differ in sign within versus between species, particularly the relationship between leaf lifespan and LMA. In conifers, we find weak and inconsistent relationships between site environment and leaf traits, making it difficult capture within-species leaf trait variation for regional model parameterization. Finally, we find limited relationships between tree relative growth rate and any foliar trait other than leaf lifespan, with leaf traits jointly explaining 42% of within-species growth variation but environmental factors explaining 77% of variation. We suggest that additional traits, particularly whole plant allometry/allocation traits may be better than leaf traits for improving vegetation model performance at smaller taxonomic and spatial scales.

Changes in photosynthesis and leaf characteristics with tree height in five dipterocarp species in a tropical rain forest.

PubMed

Kenzo, Tanaka; Ichie, Tomoaki; Watanabe, Yoko; Yoneda, Reiji; Ninomiya, Ikuo; Koike, Takayoshi

2006-07-01

Variations in leaf photosynthetic, morphological and biochemical properties with increasing plant height from seedlings to emergent trees were investigated in five dipterocarp species in a Malaysian tropical rain forest. Canopy openness increased significantly with tree height. Photosynthetic properties, such as photosynthetic capacity at light saturation, light compensation point, maximum rate of carboxylation and maximum rate of photosynthetic electron transport, all increased significantly with tree height. Leaf morphological and biochemical traits, such as leaf mass per area, palisade layer thickness, nitrogen concentration per unit area, chlorophyll concentration per unit dry mass and chlorophyll to nitrogen ratio, also changed significantly with tree height. Leaf properties had simple and significant relationships with tree height, with few intra- and interspecies differences. Our results therefore suggest that the photosynthetic capacity of dipterocarp trees depends on tree height, and that the trees adapt to the light environment by adjusting their leaf morphological and biochemical properties. These results should aid in developing models that can accurately estimate carbon dioxide flux and biomass production in tropical rain forests.

The first fossil leaf insect: 47 million years of specialized cryptic morphology and behavior

PubMed Central

Wedmann, Sonja; Bradler, Sven; Rust, Jes

2007-01-01

Stick and leaf insects (insect order Phasmatodea) are represented primarily by twig-imitating slender forms. Only a small percentage (≈1%) of extant phasmids belong to the leaf insects (Phylliinae), which exhibit an extreme form of morphological and behavioral leaf mimicry. Fossils of phasmid insects are extremely rare worldwide. Here we report the first fossil leaf insect, Eophyllium messelensis gen. et sp. nov., from 47-million-year-old deposits at Messel in Germany. The new specimen, a male, is exquisitely preserved and displays the same foliaceous appearance as extant male leaf insects. Clearly, an advanced form of extant angiosperm leaf mimicry had already evolved early in the Eocene. We infer that this trait was combined with a special behavior, catalepsy or “adaptive stillness,” enabling Eophyllium to deceive visually oriented predators. Potential predators reported from the Eocene are birds, early primates, and bats. The combination of primitive and derived characters revealed by Eophyllium allows the determination of its exact phylogenetic position and illuminates the evolution of leaf mimicry for this insect group. It provides direct evidence that Phylliinae originated at least 47 Mya. Eophyllium enlarges the known geographical range of Phylliinae, currently restricted to southeast Asia, which is apparently a relict distribution. This fossil leaf insect bears considerable resemblance to extant individuals in size and cryptic morphology, indicating minimal change in 47 million years. This absence of evolutionary change is an outstanding example of morphological and, probably, behavioral stasis. PMID:17197423

The Heterogeneity and Spatial Patterning of Structure and Physiology across the Leaf Surface in Giant Leaves of Alocasia macrorrhiza

PubMed Central

Li, Shuai; Zhang, Yong-Jiang; Sack, Lawren; Scoffoni, Christine; Ishida, Atsushi; Chen, Ya-Jun; Cao, Kun-Fang

2013-01-01

Leaf physiology determines the carbon acquisition of the whole plant, but there can be considerable variation in physiology and carbon acquisition within individual leaves. Alocasia macrorrhiza (L.) Schott is an herbaceous species that can develop very large leaves of up to 1 m in length. However, little is known about the hydraulic and photosynthetic design of such giant leaves. Based on previous studies of smaller leaves, and on the greater surface area for trait variation in large leaves, we hypothesized that A. macrorrhiza leaves would exhibit significant heterogeneity in structure and function. We found evidence of reduced hydraulic supply and demand in the outer leaf regions; leaf mass per area, chlorophyll concentration, and guard cell length decreased, as did stomatal conductance, net photosynthetic rate and quantum efficiency of photosystem II. This heterogeneity in physiology was opposite to that expected from a thinner boundary layer at the leaf edge, which would have led to greater rates of gas exchange. Leaf temperature was 8.8°C higher in the outer than in the central region in the afternoon, consistent with reduced stomatal conductance and transpiration caused by a hydraulic limitation to the outer lamina. The reduced stomatal conductance in the outer regions would explain the observed homogeneous distribution of leaf water potential across the leaf surface. These findings indicate substantial heterogeneity in gas exchange across the leaf surface in large leaves, greater than that reported for smaller-leafed species, though the observed structural differences across the lamina were within the range reported for smaller-leafed species. Future work will determine whether the challenge of transporting water to the outer regions can limit leaf size for plants experiencing drought, and whether the heterogeneity of function across the leaf surface represents a particular disadvantage for large simple leaves that might explain their global rarity, even in resource-rich environments. PMID:23776594

The heterogeneity and spatial patterning of structure and physiology across the leaf surface in giant leaves of Alocasia macrorrhiza.

PubMed

Li, Shuai; Zhang, Yong-Jiang; Sack, Lawren; Scoffoni, Christine; Ishida, Atsushi; Chen, Ya-Jun; Cao, Kun-Fang

2013-01-01

Leaf physiology determines the carbon acquisition of the whole plant, but there can be considerable variation in physiology and carbon acquisition within individual leaves. Alocasia macrorrhiza (L.) Schott is an herbaceous species that can develop very large leaves of up to 1 m in length. However, little is known about the hydraulic and photosynthetic design of such giant leaves. Based on previous studies of smaller leaves, and on the greater surface area for trait variation in large leaves, we hypothesized that A. macrorrhiza leaves would exhibit significant heterogeneity in structure and function. We found evidence of reduced hydraulic supply and demand in the outer leaf regions; leaf mass per area, chlorophyll concentration, and guard cell length decreased, as did stomatal conductance, net photosynthetic rate and quantum efficiency of photosystem II. This heterogeneity in physiology was opposite to that expected from a thinner boundary layer at the leaf edge, which would have led to greater rates of gas exchange. Leaf temperature was 8.8°C higher in the outer than in the central region in the afternoon, consistent with reduced stomatal conductance and transpiration caused by a hydraulic limitation to the outer lamina. The reduced stomatal conductance in the outer regions would explain the observed homogeneous distribution of leaf water potential across the leaf surface. These findings indicate substantial heterogeneity in gas exchange across the leaf surface in large leaves, greater than that reported for smaller-leafed species, though the observed structural differences across the lamina were within the range reported for smaller-leafed species. Future work will determine whether the challenge of transporting water to the outer regions can limit leaf size for plants experiencing drought, and whether the heterogeneity of function across the leaf surface represents a particular disadvantage for large simple leaves that might explain their global rarity, even in resource-rich environments.

Mechanism of Methane Transport from the Rhizosphere to the Atmosphere through Rice Plants 1

PubMed Central

Nouchi, Isamu; Mariko, Shigeru; Aoki, Kazuyuki

1990-01-01

To clarify the mechanisms of methane transport from the rhizosphere into the atmosphere through rice plants (Oryza sativa L.), the methane emission rate was measured from a shoot whose roots had been kept in a culture solution with a high methane concentration or exposed to methane gas in the gas phase by using a cylindrical chamber. No clear correlation was observed between change in the transpiration rate and that in the methane emission rate. Methane was mostly released from the culm, which is an aggregation of leaf sheaths, but not from the leaf blade. Micropores which are different from stomata were newly found at the abaxial epidermis of the leaf sheath by scanning electron microscopy. The measured methane emission rate was much higher than the calculated methane emission rate that would result from transpiration and the methane concentration in the culture solution. Rice roots could absorb methane gas in the gas phase without water uptake. These results suggest that methane dissolved in the soil water surrounding the roots diffuses into the cell-wall water of the root cells, gasifies in the root cortex, and then is mostly released through the micropores in the leaf sheaths. Images Figure 7 PMID:16667719

Contact rate modulates foraging efficiency in leaf cutting ants.

PubMed

Bouchebti, S; Ferrere, S; Vittori, K; Latil, G; Dussutour, A; Fourcassié, V

2015-12-21

Lane segregation is rarely observed in animals that move in bidirectional flows. Consequently, these animals generally experience a high rate of head-on collisions during their journeys. Although these collisions have a cost (each collision induces a delay resulting in a decrease of individual speed), they could also have a benefit by promoting information transfer between individuals. Here we explore the impact of head-on collisions in leaf-cutting ants moving on foraging trails by artificially decreasing the rate of head-on collisions between individuals. We show that head-on collisions do not influence the rate of recruitment in these ants but do influence foraging efficiency, i.e. the proportion of ants returning to the nest with a leaf fragment. Surprisingly, both unladen and laden ants returning to the nest participate in the modulation of foraging efficiency: foraging efficiency decreases when the rate of contacts with both nestbound laden or unladen ants decreases. These results suggest that outgoing ants are able to collect information from inbound ants even when these latter do not carry any leaf fragment and that this information can influence their foraging decisions when reaching the end of the trail.

[Effects of Ginkgo biloba extract in improving episodic memory of patients with mild cognitive impairment: a randomized controlled trial].

PubMed

Zhao, Ming-xing; Dong, Zhen-hua; Yu, Zhong-hai; Xiao, Shi-yuan; Li, Ya-ming

2012-06-01

Mild cognitive impairment is a transitional stage between normal aging and dementia. It is important in terms of recognizing memory loss in older people as well as identifying a group of individuals at high risk of developing dementia and who may benefit from preventive strategies. Ginkgo biloba extract has been shown to possess polyvalent properties, such as anti-oxidation, anti-apoptosis and anti-inflammation. Ginkgo biloba extract appears to have a neuroprotective effect against neurodegenerative diseases. To observe the efficacy of Ginkgo biloba leaf tablet in improving episodic memory of mild cognitive impairment. This is a multicenter, randomized, controlled trial. The authors enrolled generally healthy, ambulatory or ambulatory-aided amnestic subjects with MCI, 60 to 85 years old, who expressed a memory complaint from Huadong Hospital, seven Community Health Centers in Shanghai, and Shanghai First Welfare Institution. A total of 120 MCI patients were randomly assigned to the Ginkgo biloba leaf tablet group (treatment group, 60 cases) and control group (60 cases). The patients in the treatment group took Ginkgo biloba leaf tablets 3 times a day, 19.2 mg each dose. The control group did not receive any intelligence-promoting or vasodilator reflex treatment except some health care. The patients were tested with nonsense picture recognition of the clinical memory scale and the logical memory test based on the Wechsler memory scale before and after treatment. After 6 months of treatment, the scores of the logical memory test and nonsense picture recognition were increased significantly in the treatment group (P<0.01, P<0.05), while the scores of the two tests from the control group had no statistically significant difference (P>0.05). After treatment, the positive rate of nonsense picture recognition was 55.17% in the treatment group, which was significantly higher than that of the control group at 32.73% (P<0.05). The efficacy rate of logical memory was 58.62% in the treatment group, also higher than 38.18% in the control group (P<0.05). Ginkgo biloba leaf tablet showed good efficacy in promoting episodic memory function in MCI patients.

Evaluation of water-use efficiency in foxtail millet (Setaria italica) using visible-near infrared and thermal spectral sensing techniques.

PubMed

Wang, Meng; Ellsworth, Patrick Z; Zhou, Jianfeng; Cousins, Asaph B; Sankaran, Sindhuja

2016-05-15

Water limitations decrease stomatal conductance (g(s)) and, in turn, photosynthetic rate (A(net)), resulting in decreased crop productivity. The current techniques for evaluating these physiological responses are limited to leaf-level measures acquired by measuring leaf-level gas exchange. In this regard, proximal sensing techniques can be a useful tool in studying plant biology as they can be used to acquire plant-level measures in a high-throughput manner. However, to confidently utilize the proximal sensing technique for high-throughput physiological monitoring, it is important to assess the relationship between plant physiological parameters and the sensor data. Therefore, in this study, the application of rapid sensing techniques based on thermal imaging and visual-near infrared spectroscopy for assessing water-use efficiency (WUE) in foxtail millet (Setaria italica (L.) P. Beauv) was evaluated. The visible-near infrared spectral reflectance (350-2500 nm) and thermal (7.5-14 µm) data were collected at regular intervals from well-watered and drought-stressed plants in combination with other leaf physiological parameters (transpiration rate-E, A(net), g(s), leaf carbon isotopic signature-δ(13)C(leaf), WUE). Partial least squares regression (PLSR) analysis was used to predict leaf physiological measures based on the spectral data. The PLSR modeling on the hyperspectral data yielded accurate and precise estimates of leaf E, gs, δ(13)C(leaf), and WUE with coefficient of determination in a range of 0.85-0.91. Additionally, significant differences in average leaf temperatures (~1°C) measured with a thermal camera were observed between well-watered plants and drought-stressed plants. In summary, the visible-near infrared reflectance data, and thermal images can be used as a potential rapid technique for evaluating plant physiological responses such as WUE. Copyright © 2016 Elsevier B.V. All rights reserved.

Disproportionate photosynthetic decline and inverse relationship between constitutive and induced volatile emissions upon feeding of Quercus robur leaves by large larvae of gypsy moth (Lymantria dispar)

PubMed Central

Copolovici, Lucian; Pag, Andreea; Kännaste, Astrid; Bodescu, Adina; Tomescu, Daniel; Copolovici, Dana; Soran, Maria-Loredana; Niinemets, Ülo

2018-01-01

Gypsy moth (Lymantria dispar L., Lymantriinae) is a major pest of pedunculate oak (Quercus robur) forests in Europe, but how its infections scale with foliage physiological characteristics, in particular with photosynthesis rates and emissions of volatile organic compounds has not been studied. Differently from the majority of insect herbivores, large larvae of L. dispar rapidly consume leaf area, and can also bite through tough tissues, including secondary and primary leaf veins. Given the rapid and devastating feeding responses, we hypothesized that infection of Q. robur leaves by L. dispar leads to disproportionate scaling of leaf photosynthesis and constitutive isoprene emissions with damaged leaf area, and to less prominent enhancements of induced volatile release. Leaves with 0% (control) to 50% of leaf area removed by larvae were studied. Across this range of infection severity, all physiological characteristics were quantitatively correlated with the degree of damage, but all these traits changed disproportionately with the degree of damage. The net assimilation rate was reduced by almost 10-fold and constitutive isoprene emissions by more than 7-fold, whereas the emissions of green leaf volatiles, monoterpenes, methyl salicylate and the homoterpene (3E)-4,8-dimethy-1,3,7-nonatriene scaled negatively and almost linearly with net assimilation rate through damage treatments. This study demonstrates that feeding by large insect herbivores disproportionately alters photosynthetic rate and constitutive isoprene emissions. Furthermore, the leaves have a surprisingly large capacity for enhancement of induced emissions even when foliage photosynthetic function is severely impaired. PMID:29367792

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.

Effects of mutations in the Arabidopsis Cold Shock Domain Protein 3 (AtCSP3) gene on leaf cell expansion.

PubMed

Yang, Yongil; Karlson, Dale

2012-08-01

The cold shock domain is among the most evolutionarily conserved nucleic acid binding domains from prokaryotes to higher eukaryotes, including plants. Although eukaryotic cold shock domain proteins have been extensively studied as transcriptional and post-transcriptional regulators during various developmental processes, their functional roles in plants remains poorly understood. In this study, AtCSP3 (At2g17870), which is one of four Arabidopsis thaliana c old s hock domain proteins (AtCSPs), was functionally characterized. Quantitative RT-PCR analysis confirmed high expression of AtCSP3 in reproductive and meristematic tissues. A homozygous atcsp3 loss-of-function mutant exhibits an overall reduced seedling size, stunted and orbicular rosette leaves, reduced petiole length, and curled leaf blades. Palisade mesophyll cells are smaller and more circular in atcsp3 leaves. Cell size analysis indicated that the reduced size of the circular mesophyll cells appears to be generated by a reduction of cell length along the leaf-length axis, resulting in an orbicular leaf shape. It was also determined that leaf cell expansion is impaired for lateral leaf development in the atcsp3 loss-of-function mutant, but leaf cell proliferation is not affected. AtCSP3 loss-of-function resulted in a dramatic reduction of LNG1 transcript, a gene that is involved in two-dimensional leaf polarity regulation. Transient subcellular localization of AtCSP3 in onion epidermal cells confirmed a nucleocytoplasmic localization pattern. Collectively, these data suggest that AtCSP3 is functionally linked to the regulation of leaf length by affecting LNG1 transcript accumulation during leaf development. A putative function of AtCSP3 as an RNA binding protein is also discussed in relation to leaf development.

Spatial patterns of leaf δ13C and its relationship with plant functional groups and environmental factors in China

NASA Astrophysics Data System (ADS)

Li, Mingxu; Peng, Changhui; Wang, Meng; Yang, Yanzheng; Zhang, Kerou; Li, Peng; Yang, Yan; Ni, Jian; Zhu, Qiuan

2017-07-01

The leaf carbon isotope ratio (δ13C) is a useful parameter for predicting a plant's water use efficiency, as an indicator for plant classification, and even in the reconstruction of paleoclimatic environments. In this study, we investigated the spatial pattern of leaf δ13C values and its relationship with plant functional groups and environmental factors throughout China. The high leaf δ13C in the database appeared in central and western China, and the averaged leaf δ13C was -27.15‰, with a range from -21.05‰ to -31.5‰. The order of the averaged δ13C for plant life forms from most positive to most negative was subshrubs > herbs = shrubs > trees > subtrees. Leaf δ13C is also influenced by some environmental factors, such as mean annual precipitation, relative humidity, mean annual temperature, solar hours, and altitude, although the overall influences are still relatively weak, in particular the influence of MAT and altitude. And we further found that plant functional types are dominant factors that regulate the magnitude of leaf δ13C for an individual site, whereas environmental conditions are key to understanding spatial patterns of leaf δ13C when we consider China as a whole. Ultimately, we conducted a multiple regression model of leaf δ13C with environmental factors and mapped the spatial distribution of leaf δ13C in China by using this model. However, this partial least squares model overestimated leaf δ13C for most life forms, especially for deciduous trees, evergreen shrubs, and subtrees, and thus need more improvement in the future.

Chilling Stress—The Key Predisposing Factor for Causing Alternaria alternata Infection and Leading to Cotton (Gossypium hirsutum L.) Leaf Senescence

PubMed Central

Zhao, Jingqing; Li, Sha; Jiang, Tengfei; Liu, Zhi; Zhang, Wenwei; Jian, Guiliang; Qi, Fangjun

2012-01-01

Leaf senescence plays a vital role in nutrient recycling and overall capacity to assimilate carbon dioxide. Cotton premature leaf senescence, often accompanied with unexpected short-term low temperature, has been occurring with an increasing frequency in many cotton-growing areas and causes serious reduction in yield and quality of cotton. The key factors for causing and promoting cotton premature leaf senescence are still unclear. In this case, the relationship between the pre-chilling stress and Alternaria alternata infection for causing cotton leaf senescence was investigated under precisely controlled laboratory conditions with four to five leaves stage cotton plants. The results showed short-term chilling stress could cause a certain degree of physiological impairment to cotton leaves, which could be recovered to normal levels in 2–4 days when the chilling stresses were removed. When these chilling stress injured leaves were further inoculated with A. alternata, the pronounced appearance and development of leaf spot disease, and eventually the pronounced symptoms of leaf senescence, occurred on these cotton leaves. The onset of cotton leaf senescence at this condition was also reflected in various physiological indexes such as irreversible increase in malondialdehyde (MDA) content and electrolyte leakage, irreversible decrease in soluble protein content and chlorophyll content, and irreversible damage in leaves' photosynthesis ability. The presented results demonstrated that chilling stress acted as the key predisposing factor for causing A. alternata infection and leading to cotton leaf senescence. It could be expected that the understanding of the key factors causing and promoting cotton leaf senescence would be helpful for taking appropriate management steps to prevent cotton premature leaf senescence. PMID:22558354

Long-Term Inhibition by Auxin of Leaf Blade Expansion in Bean and Arabidopsis1

PubMed Central

Keller, Christopher P.; Stahlberg, Rainer; Barkawi, Lana S.; Cohen, Jerry D.

2004-01-01

The role of auxin in controlling leaf expansion remains unclear. Experimental increases to normal auxin levels in expanding leaves have shown conflicting results, with both increases and decreases in leaf growth having been measured. Therefore, the effects of both auxin application and adjustment of endogenous leaf auxin levels on midrib elongation and final leaf size (fresh weight and area) were examined in attached primary monofoliate leaves of the common bean (Phaseolus vulgaris) and in early Arabidopsis rosette leaves. Aqueous auxin application inhibited long-term leaf blade elongation. Bean leaves, initially 40 to 50 mm in length, treated once with α-naphthalene acetic acid (1.0 mm), were, after 6 d, approximately 80% the length and weight of controls. When applied at 1.0 and 0.1 mm, α-naphthalene acetic acid significantly inhibited long-term leaf growth. The weak auxin, β-naphthalene acetic acid, was effective at 1.0 mm; and a weak acid control, benzoic acid, was ineffective. Indole-3-acetic acid (1 μm, 10 μm, 0.1 mm, and 1 mm) required daily application to be effective at any concentration. Application of the auxin transport inhibitor, 1-N-naphthylphthalamic acid (1% [w/w] in lanolin), to petioles also inhibited long-term leaf growth. This treatment also was found to lead to a sustained elevation of leaf free indole-3-acetic acid content relative to untreated control leaves. Auxin-induced inhibition of leaf growth appeared not to be mediated by auxin-induced ethylene synthesis because growth inhibition was not rescued by inhibition of ethylene synthesis. Also, petiole treatment of Arabidopsis with 1-N-naphthylphthalamic acid similarly inhibited leaf growth of both wild-type plants and ethylene-insensitive ein4 mutants. PMID:14988474

Structure-Property Characterization of the Crinkle-Leaf Peach Wood Phenotype: A Future Model System for Wood Properties Research?

NASA Astrophysics Data System (ADS)

Wiedenhoeft, Alex C.; Arévalo, Rafael; Ledbetter, Craig; Jakes, Joseph E.

2016-09-01

Nearly 400 million years of evolution and field-testing by the natural world has given humans thousands of wood types, each with unique structure-property relationships to study, exploit, and ideally, to manipulate, but the slow growth of trees makes them a recalcitrant experimental system. Variations in wood features of two genotypes of peach ( Prunus persica L.) trees, wild-type and crinkle-leaf, were examined to elucidate the nature of weak wood in crinkle-leaf trees. Crinkle-leaf is a naturally-occurring mutation in which wood strength is altered in conjunction with an easily observed `crinkling' of the leaves' surface. Trees from three vigor classes (low growth rate, average growth rate, and high growth rate) of each genotype were sampled. No meaningful tendency of dissimilarities among the different vigor classes was found, nor any pattern in features in a genotype-by-vigor analysis. Wild-type trees exhibited longer vessels and fibers, wider rays, and slightly higher specific gravity. Neither cell wall mechanical properties measured with nanoindentation nor cell wall histochemical properties were statistically or observably different between crinkle-leaf and wild-type wood. The crinkle-leaf mutant has the potential to be a useful model system for wood properties investigation and manipulation if it can serve as a field-observable vegetative marker for altered wood properties.

[Effects of root-knot nematodes on cucumber leaf N and P contents, soil pH, and soil enzyme activities].

PubMed

Xu, Hua; Ruan, Wei-Bin; Gao, Yu-Bao; Song, Xiao-Yan; Wei, Yu-Kun

2010-08-01

A pot experiment was conducted to study the effects of inoculation with root-knot nematodes on the cucumber leaf N and P contents, and the rhizospheric and non-rhizospheric soil pH and enzyme activities. The rhizospheric soil pH didn't have a significant decrease until the inoculation rate reached 6000 eggs per plant. With the increase of inoculation rate, the leaf N and P contents, rhizospheric soil peroxidase activity, and rhizospheric and non-rhizospheric soil polyphenol oxidase activity all decreased gradually, rhizospheric soil catalase activity was in adverse, non-rhizospheric soil pH decreased after an initial increase, and non-rhizospheric soil catalase activity had no regular change. After inoculation, rhizospheric soil urease activity decreased significantly, but rhizospheric and non-rhizospheric soil phosphatase activity and non-rhizospheric soil peroxidase activity only had a significant decrease under high inoculation rate. In most cases, there existed significant correlations between rhizospheric soil pH, enzyme activities, and leaf N and P contents; and in some cases, there existed significant correlations between non-rhizospheric soil pH, enzyme activities, and leaf N and P contents.

In Situ Investigation the Photolysis of the PAHs Adsorbed on Mangrove Leaf Surfaces by Synchronous Solid Surface Fluorimetry

PubMed Central

Wang, Ping; Wu, Tun-Hua; Zhang, Yong

2014-01-01

An established synchronous solid surface fluorimetry (S-SSF) was utilized for in situ study the photolysis processes of anthracene (An) and pyrene (Py) adsorbed on the leaf surfaces of Kandelia obovata seedlings (Ko) and Aegiceras corniculata (L.) Blanco seedlings (Ac). Experimental results demonstrated that the photolysis of An and Py adsorbed on the leaf surfaces of two mangrove species under the laboratory conditions, followed first-order kinetics with their photolysis rates in the order of Ac>Ko. In addition, with the same amount of substances, the photolysis rate of An adsorbed on the same mangrove leaf surfaces was much faster than the adsorbed Py. In order to investigate further, the photolysis processes of An and Py in water were also studied for comparison. And the photolysis of An and Py in water also followed first-order kinetics. Moreover, for the same initial amount, the photolysis rate of the PAH in water was faster than that adsorbed on the leaf surfaces of two mangrove species. Therefore, photochemical behaviors of PAHs were dependent not only on their molecular structures but also the physical-chemical properties of the substrates on which they are adsorbed. PMID:24404158

Growth and yield characteristics of 'Waldmann's Green' leaf lettuce under different photon fluxes from metal halide or incandescent + fluorescent radiation

NASA Technical Reports Server (NTRS)

Knight, Sharon L.; Mitchell, Cary A.

1988-01-01

Growth of 'Waldmann's Green' leaf lettuce under metal halide radiation was compared with that under In = Fl at the same photosynthetic photon flux (920 micromol/s/sq m) to evaluate the influence of lamp type on growth. No differences in leaf dry weight, leaf area, relative growth rate or photosynthesis occurred after 8 days of exposure to these radiation treatments for 20 h/day.

Hydraulic properties of rice and the response of gas exchange to water stress.

PubMed

Stiller, Volker; Lafitte, H Renee; Sperry, John S

2003-07-01

We investigated the role of xylem cavitation, plant hydraulic conductance, and root pressure in the response of rice (Oryza sativa) gas exchange to water stress. In the field (Philippines), the percentage loss of xylem conductivity (PLC) from cavitation exceeded 60% in leaves even in watered controls. The PLC versus leaf water potential relationship indicated diurnal refilling of cavitated xylem. The leaf water potential causing 50 PLC (P(50)) was -1.6 MPa and did not differ between upland versus lowland rice varieties. Greenhouse-grown varieties (Utah) were more resistant to cavitation with a 50 PLC of -1.9 MPa but also showed no difference between varieties. Six-day droughts caused concomitant reductions in leaf-specific photosynthetic rate, leaf diffusive conductance, and soil-leaf hydraulic conductance that were associated with cavitation-inducing water potentials and the disappearance of nightly root pressure. The return of root pressure after drought was associated with the complete recovery of leaf diffusive conductance, leaf-specific photosynthetic rate, and soil-leaf hydraulic conductance. Root pressure after the 6-d drought (61.2 +/- 8.8 kPa) was stimulated 7-fold compared with well-watered plants before drought (8.5 +/- 3.8 kPa). The results indicate: (a) that xylem cavitation plays a major role in the reduction of plant hydraulic conductance during drought, and (b) that rice can readily reverse cavitation, possibly aided by nocturnal root pressure.

Physiological and Morphological Responses of Ischaemum rugosum Salisb. (Wrinkled Grass) to Different Nitrogen Rates and Rice Seeding Rates

PubMed Central

Awan, Tahir Hussain; Chauhan, Bhagirath Singh; Cruz, Pompe C. Sta.

2014-01-01

Ischaemum rugosum is a competitive weed in direct-seeded rice systems. Developing integrated weed management strategies that promote the suppression of weeds by crop density, cultivar selection, and nutrition requires better understanding of the extent to which rice interferes with the growth of this weed and how it responds to resource limitation due to rice interference. The growth of I. rugosum was studied when grown with four rice seeding rates (0, 25, 50, and 100 kg ha−1) and four nitrogen (N) rates (0, 50, 100, and 150 kg ha−1). Compared to the weed plants grown alone, weed tiller number was reduced by 63–80%, leaf number by 68–77%, leaf area by 69–77%, leaf biomass by 72–84%, and inflorescence biomass by 81–93% at the rice seeding rates of 25–100 kg ha−1. All these parameters increased with increasing rates of N from 0 to 150 kg ha−1. At weed maturity, I. rugosum plants were 100% taller than rice at 0 kg N ha−1, whereas, with added N, the weeds were only 50% taller than rice. Weed biomass increased by 82–160%, whereas rice biomass increased by 92–229%, with the application of 50–150 kg N ha−1. Added N favored rice biomass production more than it did the weed. Rice interference reduced the height and biomass of I. rugosum, but did not suppress its growth completely. I. rugosum showed the ability to reduce the effects of rice interference by increasing leaf area, leaf weight ratio, and specific leaf area, and by decreasing the root-shoot weight ratio in comparison to the weed plants grown alone. The results suggest that rice crop interference alone may reduce I. rugosum growth but may not provide complete control of this weed. The need for integrated weed management practices to effectively control this weed species is highlighted. PMID:24910995

Physiological and morphological responses of Ischaemum rugosum Salisb. (wrinkled grass) to different nitrogen rates and rice seeding rates.

PubMed

Awan, Tahir Hussain; Chauhan, Bhagirath Singh; Cruz, Pompe C Sta

2014-01-01

Ischaemum rugosum is a competitive weed in direct-seeded rice systems. Developing integrated weed management strategies that promote the suppression of weeds by crop density, cultivar selection, and nutrition requires better understanding of the extent to which rice interferes with the growth of this weed and how it responds to resource limitation due to rice interference. The growth of I. rugosum was studied when grown with four rice seeding rates (0, 25, 50, and 100 kg ha(-1)) and four nitrogen (N) rates (0, 50, 100, and 150 kg ha(-1)). Compared to the weed plants grown alone, weed tiller number was reduced by 63-80%, leaf number by 68-77%, leaf area by 69-77%, leaf biomass by 72-84%, and inflorescence biomass by 81-93% at the rice seeding rates of 25-100 kg ha(-1). All these parameters increased with increasing rates of N from 0 to 150 kg ha(-1). At weed maturity, I. rugosum plants were 100% taller than rice at 0 kg N ha(-1), whereas, with added N, the weeds were only 50% taller than rice. Weed biomass increased by 82-160%, whereas rice biomass increased by 92-229%, with the application of 50-150 kg N ha(-1). Added N favored rice biomass production more than it did the weed. Rice interference reduced the height and biomass of I. rugosum, but did not suppress its growth completely. I. rugosum showed the ability to reduce the effects of rice interference by increasing leaf area, leaf weight ratio, and specific leaf area, and by decreasing the root-shoot weight ratio in comparison to the weed plants grown alone. The results suggest that rice crop interference alone may reduce I. rugosum growth but may not provide complete control of this weed. The need for integrated weed management practices to effectively control this weed species is highlighted.

Increasing shrub abundance and N addition in Arctic tundra affect leaf and root litter decomposition differently

NASA Astrophysics Data System (ADS)

McLaren, J.; van de Weg, M. J.; Shaver, G. R.; Gough, L.

2013-12-01

Changes in global climate have resulted in a ';greening' of the Arctic as the abundance of deciduous shrub species increases. Consequently, not only the living plant community, but also the litter composition changes, which in turn can affect carbon turnover patterns in the Arctic. We examined effects of changing litter composition (both root and leaf litter) on decomposition rates with a litter bag study, and specifically focused on the impact of deciduous shrub Betula nana litter on litter decomposition from two evergreen shrubs (Ledum palustre, and Vaccinium vitis-idaea) and one graminoid (Eriophorum vaginatum) species. Additionally, we investigated how decomposition was affected by nutrient availability by placing the litterbags in an ambient and a fertilized moist acidic tundra environment. Measurements were carried out seasonally over 2 years (after snow melt, mid-growing season, end growing season). We measured litter mass loss over time, as well as the respiration rates (standardized for temperature and moisture) and temperature sensitivity of litter respiration at the time of harvesting the litter bags. For leaves, Betula litter decomposed faster than the other three species, with Eriophorum leaves decomposing the slowest. This pattern was observed for both mass loss and litter respiration rates, although the differences in respiration became smaller over time. Surprisingly, combining Betula with any other species resulted in slower overall weight loss rates than would be predicted based on monoculture weight loss rates. This contrasted with litter respiration at the time of sampling, which showed a positive mixing effect of adding Betula leaf liter to the other species. Apparently, during the first winter months (September - May) Betula litter decomposition is negatively affected by mixing the species and this legacy can still be observed in the total mass loss results later in the year. For root litter there were fewer effects of species identity on root decomposition rates; only Ledum roots decomposed slower than the other three species and the overall root litter respiration rates increased with the duration of the experiment (in contrast to leaf liter respiration). A fertilized environment had no effect on overall weight loss of the leaf or root litter within the time of our study, but leaf and root litter respiration rates were significantly larger at the end of the study in the fertilized tundra.The temperature sensitivity of leaf respiration was significantly lower for leaf litter respiration than root liter respiration after fist snow melt, but this difference disappeared throughout the first growing season and neither was influenced by species composition or fertilization with N+P. Overall, our results suggest that as arctic vegetation shifts towards shrub-dominated tundra, both species composition and seasonally dependent processes will determine effects of changing vegetation types on carbon turnover in arctic ecosystems.

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.

Growth and photosynthesis of Japanese flowering cherry under simulated microgravity conditions

NASA Technical Reports Server (NTRS)

Sugano, Mami; Ino, Yoshio; Nakamura, Teruko

2002-01-01

The photosynthetic rate, the leaf characteristics related to photosynthesis, such as the chlorophyll content, chlorophyll a/b ratio and density of the stomata, the leaf area and the dry weight in seedlings of Japanese flowering cherry grown under normal gravity and simulated microgravity conditions were examined. No significant differences were found in the photosynthetic rates between the two conditions. Moreover, leaf characteristics such as the chlorophyll content, chlorophyll a/b ratio and density of the stomata in the seedlings grown under the simulated microgravity condition were not affected. However, the photosynthetic product of the whole seedling under the simulated microgravity condition increased compared with the control due to its leaf area increase. The results suggest that dynamic gravitational stimulus controls the partitioning of the products of photosynthesis.

Movement of Abscisic Acid into the Apoplast in Response to Water Stress in Xanthium strumarium L.

PubMed

Cornish, K; Zeevaart, J A

1985-07-01

The effect of water stress on the redistribution of abcisic acid (ABA) in mature leaves of Xanthium strumarium L. was investigated using a pressure dehydration technique. In both turgid and stressed leaves, the ABA in the xylem exudate, the ;apoplastic' ABA, increased before ;bulk leaf' stress-induced ABA accumulation began. In the initially turgid leaves, the ABA level remained constant in both the apoplast and the leaf as a whole until wilting symptoms appeared. Following turgor loss, sufficient quantities of ABA moved into the apoplast to stimulate stomatal closure. Thus, the initial increase of apoplastic ABA may be relevant to the rapid stomatal closure seen in stressed leaves before their bulk leaf ABA levels rise.Following recovery from water stress, elevated levels of ABA remained in the apoplast after the bulk leaf contents had returned to their prestress values. This apoplastic ABA may retard stomatal reopening during the initial recovery period.

[Effects of drought stress and subsequent rewatering on major physiological parameters of spring maize during the key growth periods].

PubMed

Cai, Fu; Mi, Na; Ji, Rui Peng; Zhao, Xian Li; Shi, Kui Qiao; Yang, Yang; Zhang, Hui; Zhang, Yu Shu

2017-11-01

For deeply understanding water consumption characteristics and disaster-causing mechanism of spring maize under drought stress, continuous no-water complementing for 40 days and subsequent rewatering treatments were conducted in jointing (T 1 ) and tasseling (T 2 ) stages of spring maize 'Danyu 39'. In the meantime, leaf and root water potential, main variables associated with photosynthesis including net photosynthetic rate (P n ), transpiration rate (T r ), stomatal conduc-tance (g s ), intercellular CO 2 concentration(C i ) and stem flow rate (SF) were dynamically observed and the characteristics of their responses to drought and subsequent rehydration were investigated. The results indicated that leaf and root water potential, both presenting logarithm relationships with soil water content, decreased due to suffering from drought stress in different growth stages and the response of the former lagged behind that of the latter. At the same time, the response of leaf (root) water potential to drought stress in tasseling stage was earlier (later) than in jointing stage. For the response of rewatering, leaf water potential for the treatment T 1 (T 2 ) was (not) able to recover to a certain extent, and could not reach the normal condition, while water potential of root was more responsive and closer to the normal level than that of leaf for the treatment T 1 . Furthermore, P n and T r responded more quickly to the treatment T 2 than to the treatment T 1 . For subsequent rewatering after the treatment T 1 (T 2 ), both P n and T r restored rapidly (slowly) with the former exceeding (returning) and the later being (not) able to reach normal level. Meanwhile, the response of T r was faster than that of P n to the treatment T 1 and they responded simultaneously to the treatment T 2 . The response of g s agreed with P n to drought stress. Change trend of C i for the treatment T 1 (T 2 ) was consistent (opposite) with that of P n . In addition, SFs for various drought treatments and their daily maximums decreased and appeared ahead of time to different extents, respectively. At the same time, the response of SF to drought stress was more sensitive for the treatment T 2 than for T 1 and on a clear day than on a cloudy day, but the sensibility of SF declined after drought reached a certain level. Besides, SFs for both the treatment T 1 and T 2 increased as a result of rewatering after drought and the increase for the treatment T 1 was larger than that for the treatment T 2 .

Growth responses of Phragmites karka - a candidate for second generation biofuel from degraded saline lands

NASA Astrophysics Data System (ADS)

Zaheer Ahmed, Muhammad; Shoukat, Erum; Abideen, Zainul; Aziz, Irfan; Gulzar, Salman; Ajmal Khan, M.

2017-04-01

Global changes like rapidly increasing population, limited fresh water resources, increasing salinity and aridity are the major causes of land degradation. Increasing feed production for bioenergy through direct and indirect land use cause major threat to biodiversity besides competing with food resources. Growing halophytes on saline lands would provide alternate source of energy without compromising food and cash crop farming. Phragmites karkahas recently emerged as a potential bio-fuel crop, which maintains optimal growth at 100 mM NaCl with high ligno-cellulosic biomass. However, temporal and organ specific plant responses under salinity needs to be understood for effective management of degraded saline lands. This study was designed to investigate variation in growth, water relations, ion-flux, damage markers, soluble sugars, stomatal stoichiometry and photosynthetic responses of P. karka to short (0-7 days) and long (15-30 days) term exposure with 0 (control), 100 (moderate) and 300 (high) mM NaCl. A reduced shoot growth ( 45%) during earlier (within 7 days) phase was observed in 300 mM NaCl compared to control and moderate salinity. Reduced leaf elongation rate and leaf senescence from 7th day in 300 mM NaCl (and later in moderate salinity) correspond to increasing hydrogen peroxide and malondialdehyde contents. Leaf turgor loss represents the osmotic effect of NaCl at both concentrations, however turgor recovered completely in moderate salinity within a week. Plant appeared to use both organic solutes (soluble sugars) and ions (Na++K++Cl-) for osmotic adjustment along with improved water use efficiency under saline conditions. Turgor loss in high salinity (300 mM NaCl) was related to increased bulk elastic modulus and decreased hydraulic capacitance which ultimately resulted in low water potential. Leaf Na+ and Cl- accumulation increased earlier (from 7th day) in 300 mM NaCl and later in 100 mM. Higher ion sequestration in different organs was found in the following order: root > senesced leaves > young leaves. Moreover, plants maintained nutrient homeostasis (K+, Ca++, Mg++, NO-) by selective uptake via root and transport towards leaf. Moderate salinity increased instantaneous carboxylation efficiency and water use efficiency with stomatal density and smaller pore size compared to control which supported unchanged photosynthetic rate by protecting light harvesting machinery. Low photosynthetic rate in early phase of higher salinity was related to reduced stomatal conductance, while in later phase (15-30 days) due to decreased carboxylation efficiency, effective quantum yield and Fv/Fm (at noon). In conclusion, organ specific responses to short and long term exposure in moderate salinity ensures successful plant survival, whereas long term exposure tohigh salinitywas toxic for plant growth. It is recommended that P. karka could be grown as a biofuel crop on marginally saline and degraded lands.

Impact of Meloidogyne incognita on Physiological Efficiency of Vitis vinifera.

PubMed

Melakeberhan, H; Ferris, H

1989-01-01

Four-week-old French Colombard plants rooted from green cuttings were inoculated with 0, 1,000, 2,000, 4,000, or 8,000 Meloidogyne incognita second-stage juveniles and maintained at 25 C night and 30 C day. Leaf area and dry weight and the rates of photosynthesis, stomatal conductance, and internal leaf CO concentration were measured at intervals up to 59 days after inoculation. Nematode stress dosage, measured as the product of cumulative number of juveniles and females and their total energy (calories) demand, was up to 3.4 kcal and accounted for up to 15% of the energy assimilated by the plants. There was a decline in the rate of leaf area expansion and leaf, stem, shoot, root (excluding nematode weight), and total plant dry weight with increasing nematode stress. Root weight including nematodes was not affected. Total respiration, plant photosynthesis, energy assimilated into plant tissue and respiration, and gross production efficiency decreased significantly with nematode stress. Photosynthetic rate, transpiration rate, stomatal conductance, and internal CO concentration were not affected. This study demonstrates that the energy demand for growth and reproduction of M. incognita accounts for a significant portion of the total energy entering the plant system. As a result, less energy is partitioned into leaf area expansion which, in turn, affects the energy entering the system and results in decreased productivity of nematode-infected grape vines.

[Compensation effect of cotton growth and development after soil salt content reduction at bud stage].

PubMed

Guo, Wen-Qi; Zhang, Pei-Tong; Li, Chun-Hong; Yin, Jian-Mei; Han, Xiao-Yong

2014-01-01

To elucidate the dynamic characteristics of cotton growth and development after soil salt content reduction (SD) at bud stage and its effect on yield formation, a pot experiment was conducted in which soil salt content was declined from 5 per thousand level to 2 per thousand level at cotton bud stage. The results showed that the plant height, biomass, total fruit branch and fruit node number, boll number, boll mass of cotton plants increased after soil salt content reduction at bud stage. The distribution proportions of biomass in root and boll decreased after soil salt content reduction, however, the distribution proportions of biomass in leaf, main stem and fruit branch were on the rise. The growth rate of cotton plant increased after soil salt content reduction. Plant dry matter accumulation rate of SD cotton exceeded CK cotton at 22 days after soil salt content reduction. The response of different organs of cotton plant were different to soil salt content reduction, the plant height was the earliest, followed by the fruit branch and fruit node formation, and the bud and boll were the latest, which indicated that the compensation effect of cotton growth and development after soil salt content reduction at bud stage firstly appeared on the formation and growth of new leaf, fruit branch and fruit node, and on this basis, gradually brought out yield compensation.

Immobilization and mineralization of N and P by heterotrophic microbes during leaf decomposition

Treesearch

Beth Cheever; Erika Kratzer; Jackson Webster

2012-01-01

According to theory, the rate and stoichiometry of microbial mineralization depend, in part, on nutrient availability. For microbes associated with leaves in streams, nutrients are available from both the water column and the leaf. Therefore, microbial nutrient cycling may change with nutrient availability and during leaf decomposition. We explored spatial and temporal...

Extending the generality of leaf economic design principles in the cycads, an ancient lineage.

PubMed

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

2015-04-01

Cycads are the most ancient lineage of living seed plants, but the design of their leaves has received little study. We tested whether cycad leaves are governed by the same fundamental design principles previously established for ferns, conifers and angiosperms, and characterized the uniqueness of this relict lineage in foliar trait relationships. Leaf structure, photosynthesis, hydraulics and nutrient composition were studied in 33 cycad species from nine genera and three families growing in two botanical gardens. Cycads varied greatly in leaf structure and physiology. Similarly to other lineages, light-saturated photosynthetic rate per mass (Am ) was related negatively to leaf mass per area and positively to foliar concentrations of chlorophyll, nitrogen (N), phosphorus and iron, but unlike angiosperms, leaf photosynthetic rate was not associated with leaf hydraulic conductance. Cycads had lower photosynthetic N use efficiency and higher photosynthetic performance relative to hydraulic capacity compared with other lineages. These findings extend the relationships shown for foliar traits in angiosperms to the cycads. This functional convergence supports the modern synthetic understanding of leaf design, with common constraints operating across lineages, even as they highlight exceptional aspects of the biology of this key relict lineage. © 2015 The Authors. New Phytologist © 2015 New Phytologist Trust.

Effects of invasive European bird cherry (Prunus padus) on leaf litter processing by aquatic invertebrate shredder communities in urban Alaskan streams

USGS Publications Warehouse

Roon, David A.; Wipfli, Mark S.; Wurtz, Tricia L.

2014-01-01

European bird cherry (Prunus padus) (EBC) is an invasive ornamental tree that is spreading rapidly in riparian forests of urban Alaska. To determine how the spread of EBC affects leaf litter processing by aquatic invertebrate shredders, we conducted complementary leaf pack experiments in two streams located in Anchorage, Alaska. The first experiment contrasted invasive EBC with three native tree species—thin-leaf alder (Alnus tenuifolia), paper birch (Betula neoalaskana), and black cottonwood (Populus trichocarpa)—in one reach of Chester Creek; finding that EBC leaf litter broke down significantly faster than birch and cottonwood, but at a similar rate to alder. The second experiment contrasted EBC with alder in four reaches of Campbell and Chester creeks; finding that while EBC leaf litter broke down significantly faster than alder in Chester Creek, EBC broke down at a similar rate to alder in Campbell Creek. Although EBC sometimes supported fewer shredders by both count and mass, shredder communities did not differ significantly between EBC and native plants. Collectively, these data suggest that invasive EBC is not currently exhibiting strong negative impacts on leaf litter processing in these streams, but could if it continues to spread and further displaces native species over time.

Impact of plant shoot architecture on leaf cooling: a coupled heat and mass transfer model

PubMed Central

Bridge, L. J.; Franklin, K. A.; Homer, M. E.

2013-01-01

Plants display a range of striking architectural adaptations when grown at elevated temperatures. In the model plant Arabidopsis thaliana, these include elongation of petioles, and increased petiole and leaf angles from the soil surface. The potential physiological significance of these architectural changes remains speculative. We address this issue computationally by formulating a mathematical model and performing numerical simulations, testing the hypothesis that elongated and elevated plant configurations may reflect a leaf-cooling strategy. This sets in place a new basic model of plant water use and interaction with the surrounding air, which couples heat and mass transfer within a plant to water vapour diffusion in the air, using a transpiration term that depends on saturation, temperature and vapour concentration. A two-dimensional, multi-petiole shoot geometry is considered, with added leaf-blade shape detail. Our simulations show that increased petiole length and angle generally result in enhanced transpiration rates and reduced leaf temperatures in well-watered conditions. Furthermore, our computations also reveal plant configurations for which elongation may result in decreased transpiration rate owing to decreased leaf liquid saturation. We offer further qualitative and quantitative insights into the role of architectural parameters as key determinants of leaf-cooling capacity. PMID:23720538

Global synthesis of the temperature sensitivity of leaf litter breakdown in streams and rivers

Treesearch

Jennifer J. Follstad Shah; John S. Kominoski; Marcelo Ardón; Walter K. Dodds; Mark O. Gessner; Natalie A. Griffiths; Charles P. Hawkins; Sherri L. Johnson; Antoine Lecerf; Carri J. LeRoy; David W. P. Manning; Amy D. Rosemond; Robert L. Sinsabaugh; Christopher M. Swan; Jackson R. Webster; Lydia H. Zeglin

2017-01-01

Streams and rivers are important conduits of terrestrially derived carbon (C) to atmospheric and marine reservoirs. Leaf litter breakdown rates are expected to increase as water temperatures rise in response to climate change. The magnitude of increase in breakdown rates is uncertain, given differences in litter quality and microbial and detritivore community...

Distribution of leaf characteristics in relation to orientation within the canopy of woody species

NASA Astrophysics Data System (ADS)

Escudero, Alfonso; Fernández, José; Cordero, Angel; Mediavilla, Sonia

2013-04-01

Over the last few decades considerable effort has been devoted to research of leaf adaptations to environmental conditions. Many studies have reported strong differences in leaf mass per unit area (LMA) within a single tree depending on the photosynthetic photon flux density (PPFD) incident on different locations in the crown. There are fewer studies, however, of the effects of differences in the timing of light incidence during the day on different crown orientations. Leaves from isolated trees of Quercus suber and Quercus ilex in a cold Mediterranean climate were sampled to analyze differences in LMA and other leaf traits among different crown orientations. Gas-exchange rates, leaf water potentials, leaf temperatures and PPFD incident on leaf surfaces in different crown orientations were also measured throughout one entire summer day for each species. Mean daily PPFD values were similar for the leaves from the eastern and western sides of the canopy. On the western side, PPFD reached maximum values during the afternoon. Maximum leaf temperatures were approximately 10-20% higher on the west side, whereas minimum leaf water potentials were between 10 and 24% higher on the east side. Maximum transpiration rates were approximately 22% greater on the west, because of the greater leaf-to-air vapor pressure deficits (LAVPD). Mean individual leaf area was around 10% larger on the east than on the west side of the trees. In contrast, there were no significant differences in LMA between east and west sides of the crown. Contrary to our expectations, more severe water stress on the west side did not result in increases in LMA, although it was associated with lower individual leaf area. We conclude that increases in LMA measured by other authors along gradients of water stress would be due to differences in light intensity between dry and humid sites.

Silver-Foil Psychrometer for Measuring Leaf Water Potential in situ.

PubMed

Hoffman, G J; Rawlins, S L

1972-09-01

The water potential of leaves in situ can be measured without temperature control with a miniature, single-junction psychrometer constructed from silver foil and attached to the leaf with a silver-impregnated, conductive coating. The temperature of the psychrometer has been found to stay within 0.025 degrees C of the temperature of a simulated leaf when the latter temperature was changing at a rate of 1 degrees C per minute. Leaf water potentials can be measured with a precision of +/- 1 bar, or better.

Effects of acidic precipitation on leaf decomposition rates, microbial biomass, and leaf pack macroinvertebrates in six streams on the Allegheny plateau of West Virginia

Treesearch

Erik S. Engstrom; Sean K. Meegan; Sue A. Perry; William B. Perry

1996-01-01

We studied the effects of acidification on leaf litter decomposition in six headwater streams in the Monongahela National Forest. These streams differed in underlying geology and mean baseflow pH (3.99, 4.24, 6.13, 6.47, 6.59, and 7.52). We placed 10-gram leaf packs of white oak, red maple, and yellow poplar in each stream, and retrieved them after two days, two weeks...

Assessing Quantitative Resistance against Leptosphaeria maculans (Phoma Stem Canker) in Brassica napus (Oilseed Rape) in Young Plants

PubMed Central

Huang, Yong-Ju; Qi, Aiming; King, Graham J.; Fitt, Bruce D. L.

2014-01-01

Quantitative resistance against Leptosphaeria maculans in Brassica napus is difficult to assess in young plants due to the long period of symptomless growth of the pathogen from the appearance of leaf lesions to the appearance of canker symptoms on the stem. By using doubled haploid (DH) lines A30 (susceptible) and C119 (with quantitative resistance), quantitative resistance against L. maculans was assessed in young plants in controlled environments at two stages: stage 1, growth of the pathogen along leaf veins/petioles towards the stem by leaf lamina inoculation; stage 2, growth in stem tissues to produce stem canker symptoms by leaf petiole inoculation. Two types of inoculum (ascospores; conidia) and three assessment methods (extent of visible necrosis; symptomless pathogen growth visualised using the GFP reporter gene; amount of pathogen DNA quantified by PCR) were used. In stage 1 assessments, significant differences were observed between lines A30 and C119 in area of leaf lesions, distance grown along veins/petioles assessed by visible necrosis or by viewing GFP and amount of L. maculans DNA in leaf petioles. In stage 2 assessments, significant differences were observed between lines A30 and C119 in severity of stem canker and amount of L. maculans DNA in stem tissues. GFP-labelled L. maculans spread more quickly from the stem cortex to the stem pith in A30 than in C119. Stem canker symptoms were produced more rapidly by using ascospore inoculum than by using conidial inoculum. These results suggest that quantitative resistance against L. maculans in B. napus can be assessed in young plants in controlled conditions. Development of methods to phenotype quantitative resistance against plant pathogens in young plants in controlled environments will help identification of stable quantitative resistance for control of crop diseases. PMID:24454767

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.

Carbon budget of leaves of the tropical intertidal seagrass Thalassia hemprichii

NASA Astrophysics Data System (ADS)

Chiu, Shih-Han; Huang, Yen-Hsun; Lin, Hsing-Juh

2013-07-01

The question of whether seagrass beds are effective carbon sinks has recently attracted much attention. Leaf production and consumption, and detrital export and decomposition were determined to quantify the carbon budget of leaf production in a southern Taiwan seagrass bed composed of the tropical intertidal seagrass Thalassia hemprichii, which is widely distributed in intertidal zones of the western Pacific. The influence of elevation in the intertidal zone on these processes was also investigated. Leaf production and consumption, and export of leaf detritus showed seasonal variations, with higher rates in the wet season (summer and autumn) and lower rates in the dry season (winter and spring). At the high-elevation site, leaf consumption by fish was significantly higher than that by sea urchins. At the low-elevation site, however, the proportion of leaves consumed by sea urchins was equivalent to that by fish. Leaf detritus decomposed rapidly within the first 9 days, then gradually slowed down, and stabilised after 212 days, at which only 8.7% of dry weight remained in the litterbags. The carbon budget of seagrass leaves demonstrated that 20% of leaf production was grazed by fish and sea urchins and 80% flowed to detritus. This suggests that seagrass leaves are important food sources for inhabiting herbivores. Most of the detritus decomposed (44% of leaf production) or was exported (32% of leaf production), and only 4% of leaf production or 22 g C m-2 yr-1 was stored in this tropical intertidal seagrass bed. Mass balance calculations support this tropical seagrass bed acting as a carbon sink and an outwelling system which exports organic detritus to neighboring coral reefs.

Sympodial bamboo species differ in carbon bio-sequestration and stocks within phytoliths of leaf litters and living leaves.

PubMed

Xiang, Tingting; Ying, Yuqi; Teng, Jiangnan; Huang, Zhangting; Wu, Jiasen; Meng, Cifu; Jiang, Peikun; Tang, Caixian; Li, Jianmin; Zheng, Rong

2016-10-01

Phytolith-occluded carbon (PhytOC) with high resistance against decomposition is an important carbon (C) sink in many ecosystems. This study compared concentrations of phytolith in plants and the PhytOC production of seven sympodial bamboo species in southern China, aiming to provide the information for the managed bamboo plantation and selection of bamboo species to maximize phytolith C sequestration. Leaf litters and living leaves of seven sympodial bamboo species were collected from the field sites. Concentrations of phytoliths, silicon (Si), and PhytOC in leaf litters and living leaves were measured. Carbon sequestration as PhytOC was estimated. There was a considerable variation in the PhytOC concentrations in the leaf litters and living leaves among the seven bamboo species. The mean concentrations of PhytOC ranged from 3.4 to 6.9 g kg(-1) in leaf litters and from 1.6 to 5.9 g kg(-1) in living leaves, with the PhytOC production rates ranging from 5.7 to 52.3 kg e-CO2 ha(-1) year(-1) as leaf litters. Dendrocalamopsis oldhami (Munro) Keng f. had the highest PhytOC production rate. Based on a bio-sequestration rate of 52.3 kg e-CO2 ha(-1) year(-1), we estimated that the current 8 × 10(5) ha of sympodial bamboo stands in China could potentially acquire 4.2 × 10(4) t e-CO2 yearly via phytolith carbon. Furthermore, the seven sympodial bamboo species stored 5.38 × 10(5) t e-CO2 as PhytOC in living leaves and leaf litters in China. It is concluded that sympodial bamboos make a significant contribution to C sequestration and that to maximize the PhytOC accumulation, the bamboo species with the highest PhytOC production rate should be selected for plantation.

Competitive interactions between native and invasive exotic plant species are altered under elevated carbon dioxide.

PubMed

Manea, Anthony; Leishman, Michelle R

2011-03-01

We hypothesized that the greater competitive ability of invasive exotic plants relative to native plants would increase under elevated CO(2) because they typically have traits that confer the ability for fast growth when resources are not limiting and thus are likely to be more responsive to elevated CO(2). A series of competition experiments under ambient and elevated CO(2) glasshouse conditions were conducted to determine an index of relative competition intensity for 14 native-invasive exotic species-pairs. Traits including specific leaf area, leaf mass ratio, leaf area ratio, relative growth rate, net assimilation rate and root weight ratio were measured. Competitive rankings within species-pairs were not affected by CO(2) concentration: invasive exotic species were more competitive in 9 of the 14 species-pairs and native species were more competitive in the remaining 5 species-pairs, regardless of CO(2) concentration. However, there was a significant interaction between plant type and CO(2) treatment due to reduced competitive response of native species under elevated compared with ambient CO(2) conditions. Native species had significantly lower specific leaf area and leaf area ratio under elevated compared with ambient CO(2). We also compared traits of more-competitive with less-competitive species, regardless of plant type, under both CO(2) treatments. More-competitive species had smaller leaf weight ratio and leaf area ratio, and larger relative growth rate and net assimilation rate under both ambient and elevated CO(2) conditions. These results suggest that growth and allocation traits can be useful predictors of the outcome of competitive interactions under both ambient and elevated CO(2) conditions. Under predicted future atmospheric CO(2) conditions, competitive rankings among species may not change substantially, but the relative success of invasive exotic species may be increased. Thus, under future atmospheric CO(2) conditions, the ecological and economic impact of some invasive exotic plants may be even greater than under current conditions.

Arbuscular Mycorrhizal Fungus Species Dependency Governs Better Plant Physiological Characteristics and Leaf Quality of Mulberry (Morus alba L.) Seedlings

PubMed Central

Shi, Song-Mei; Chen, Ke; Gao, Yuan; Liu, Bei; Yang, Xiao-Hong; Huang, Xian-Zhi; Liu, Gui-Xi; Zhu, Li-Quan; He, Xin-Hua

2016-01-01

Understanding the synergic interactions between arbuscular mycorrhizal fungi (AMF) and its host mulberry (Morus alba L.), an important perennial multipurpose plant, has theoretical and practical significance in mulberry plantation, silkworm cultivation, and relevant textile industry. In a greenhouse study, we compared functional distinctions of three genetically different AMF species (Acaulospora scrobiculata, Funneliformis mosseae, and Rhizophagus intraradices) on physiological and growth characteristics as well as leaf quality of 6-month-old mulberry seedlings. Results showed that mulberry was AMF-species dependent, and AMF colonization significantly increased shoot height and taproot length, stem base and taproot diameter, leaf and fibrous root numbers, and shoot and root biomass production. Meanwhile, leaf chlorophyll a or b and carotenoid concentrations, net photosynthetic rate, transpiration rate and stomatal conductance were generally significantly greater, while intercellular CO2 concentration was significantly lower in AMF-inoculated seedlings than in non-AMF-inoculated counterparts. These trends were also generally true for leaf moisture, total nitrogen, all essential amino acids, histidine, proline, soluble protein, sugar, and fatty acid as they were significantly increased under mycorrhization. Among these three tested AMFs, significantly greater effects of AMF on above-mentioned mulberry physiological and growth characteristics ranked as F. mosseae > A. scrobiculata > R. intraradices, whilst on mulberry leaf quality (e.g., nutraceutical values) for better silkworm growth as F. mosseae ≈A. scrobiculata > R. intraradices. In conclusion, our results showed that greater mulberry biomass production, and nutritional quality varied with AMF species or was AMF-species dependent. Such improvements were mainly attributed to AMF-induced positive alterations of mulberry leaf photosynthetic pigments, net photosynthetic rate, transpiration rate, and N-containing compounds (methionine, threonine, histidine, and proline). As a result, application of Funneliformis mosseae or A. scrobiculata in mulberry plantation could be a promising management strategy to promote silkworm cultivation and relevant textile industry. PMID:27446063

Arbuscular Mycorrhizal Fungus Species Dependency Governs Better Plant Physiological Characteristics and Leaf Quality of Mulberry (Morus alba L.) Seedlings.

PubMed

Shi, Song-Mei; Chen, Ke; Gao, Yuan; Liu, Bei; Yang, Xiao-Hong; Huang, Xian-Zhi; Liu, Gui-Xi; Zhu, Li-Quan; He, Xin-Hua

2016-01-01

Understanding the synergic interactions between arbuscular mycorrhizal fungi (AMF) and its host mulberry (Morus alba L.), an important perennial multipurpose plant, has theoretical and practical significance in mulberry plantation, silkworm cultivation, and relevant textile industry. In a greenhouse study, we compared functional distinctions of three genetically different AMF species (Acaulospora scrobiculata, Funneliformis mosseae, and Rhizophagus intraradices) on physiological and growth characteristics as well as leaf quality of 6-month-old mulberry seedlings. Results showed that mulberry was AMF-species dependent, and AMF colonization significantly increased shoot height and taproot length, stem base and taproot diameter, leaf and fibrous root numbers, and shoot and root biomass production. Meanwhile, leaf chlorophyll a or b and carotenoid concentrations, net photosynthetic rate, transpiration rate and stomatal conductance were generally significantly greater, while intercellular CO2 concentration was significantly lower in AMF-inoculated seedlings than in non-AMF-inoculated counterparts. These trends were also generally true for leaf moisture, total nitrogen, all essential amino acids, histidine, proline, soluble protein, sugar, and fatty acid as they were significantly increased under mycorrhization. Among these three tested AMFs, significantly greater effects of AMF on above-mentioned mulberry physiological and growth characteristics ranked as F. mosseae > A. scrobiculata > R. intraradices, whilst on mulberry leaf quality (e.g., nutraceutical values) for better silkworm growth as F. mosseae ≈A. scrobiculata > R. intraradices. In conclusion, our results showed that greater mulberry biomass production, and nutritional quality varied with AMF species or was AMF-species dependent. Such improvements were mainly attributed to AMF-induced positive alterations of mulberry leaf photosynthetic pigments, net photosynthetic rate, transpiration rate, and N-containing compounds (methionine, threonine, histidine, and proline). As a result, application of Funneliformis mosseae or A. scrobiculata in mulberry plantation could be a promising management strategy to promote silkworm cultivation and relevant textile industry.

Weak leaf photosynthesis and nutrient content relationships from tropical vegetation

NASA Astrophysics Data System (ADS)

Domingues, T. F.; Ishida, F. Y.; Feldpaush, T.; Saiz, G.; Grace, J.; Meir, P.; Lloyd, J.

2015-12-01

Evergreen rain forests and savannas are the two major vegetations of tropical land ecosystems, in terms of land area, biomass, biodiversity, biogeochemical cycles and rates of land use change. Mechanistically understanding ecosystem functioning on such ecosystems is still far from complete, but important for generation of future vegetation scenarios in response to global changes. Leaf photosynthetic rates is a key processes usually represented on land surface-atmosphere models, although data from tropical ecosystems is scarce, considering the high biodiversity they contain. As a shortcut, models usually recur to relationships between leaf nutrient concentration and photosynthetic rates. Such strategy is convenient, given the possibility of global datasets on leave nutrients derived from hyperspectral remote sensing data. Given the importance of Nitrogen on enzyme composition, this nutrient is usually used to infer photosynthetic capacity of leaves. Our experience, based on individual measurements on 1809 individual leaves from 428 species of trees and shrubs naturally occurring on tropical forests and savannas from South America, Africa and Australia, indicates that the relationship between leaf nitrogen and its assimilation capacity is weak. Therefore, leaf Nitrogen alone is a poor predictor of photosynthetic rates of tropical vegetation. Phosphorus concentrations from tropical soils are usually low and is often implied that this nutrient limits primary productivity of tropical vegetation. Still, phosphorus (or other nutrients) did not exerted large influence over photosynthetic capacity, although potassium influenced vegetation structure and function. Such results draw attention to the risks of applying universal nitrogen-photosynthesis relationships on biogeochemical models. Moreover, our data suggests that affiliation of plant species within phylogenetic hierarchy is an important aspect in understanding leaf trait variation. The lack of a strong single predictor of leaf photosynthesis indicates that the importance of other factors such as secondary compounds, mesophyll conductance, Rubisco activation state, etc might be more influential than anticipated.

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.

Characterization of a commercial multileaf collimator used for intensity modulated radiation therapy.

PubMed

Low, D A; Sohn, J W; Klein, E E; Markman, J; Mutic, S; Dempsey, J F

2001-05-01

The characteristics of a commercial multileaf collimator (MLC) to deliver static and dynamic multileaf collimation (SMLC and DMLC, respectively) were investigated to determine their influence on intensity modulated radiation therapy (IMRT) treatment planning and quality assurance. The influence of MLC leaf positioning accuracy on sequentially abutted SMLC fields was measured by creating abutting fields with selected gaps and overlaps. These data were also used to measure static leaf positioning precision. The characteristics of high leaf-velocity DMLC delivery were measured with constant velocity leaf sequences starting with an open field and closing a single leaf bank. A range of 1-72 monitor units (MU) was used providing a range of leaf velocities. The field abutment measurements yielded dose errors (as a percentage of the open field max dose) of 16.7+/-0.7% mm(-1) and 12.8+/-0.7% mm(-1) for 6 MV and 18 MV photon beams, respectively. The MLC leaf positioning precision was 0.080+/-0.018 mm (single standard deviation) highlighting the excellent delivery hardware tolerances for the tested beam delivery geometry. The high leaf-velocity DMLC measurements showed delivery artifacts when the leaf sequence and selected monitor units caused the linear accelerator to move the leaves at their maximum velocity while modulating the accelerator dose rate to deliver the desired leaf and MU sequence (termed leaf-velocity limited delivery). According to the vendor, a unique feature to their linear accelerator and MLC is that the dose rate is reduced to provide the correct cm MU(-1) leaf velocity when the delivery is leaf-velocity limited. However, it was found that the system delivered roughly 1 MU per pulse when the delivery was leaf-velocity limited causing dose profiles to exhibit discrete steps rather than a smooth dose gradient. The root mean square difference between the steps and desired linear gradient was less than 3% when more than 4 MU were used. The average dose per MU was greater and less than desired for closing and opening leaf patterns, respectively, when the delivery was leaf-velocity limited. The results indicated that the dose delivery artifacts should be minor for most clinical cases, but limit the assumption of dose linearity when significantly reducing the delivered dose for dosimeter characterization studies or QA measurements.

Leaf surface traits and water storage retention affect photosynthetic responses to leaf surface wetness among wet tropical forest and semiarid savanna plants.

PubMed

Aparecido, Luiza M T; Miller, Gretchen R; Cahill, Anthony T; Moore, Georgianne W

2017-10-01

While it is reasonable to predict that photosynthetic rates are inhibited while leaves are wet, leaf gas exchange measurements during wet conditions are challenging to obtain due to equipment limitations and the complexity of canopy-atmosphere interactions in forested environments. Thus, the objective of this study was to evaluate responses of seven tropical and three semiarid savanna plant species to simulated leaf wetness and test the hypotheses that (i) leaf wetness reduces photosynthetic rates (Anet), (ii) leaf traits explain different responses among species and (iii) leaves from wet environments are better adapted for wet leaf conditions than those from drier environments. The two sites were a tropical rainforest in northern Costa Rica with ~4200 mm annual rainfall and a savanna in central Texas with ~1100 mm. Gas exchange measurements were collected under dry and wet conditions on five sun-exposed leaf replicates from each species. Additional measurements included leaf wetness duration and stomatal density. We found that Anet responses varied greatly among species, but all plants maintained a baseline of activity under wet leaf conditions, suggesting that abaxial leaf Anet was a significant percentage of total leaf Anet for amphistomatous species. Among tropical species, Anet responses immediately after wetting ranged from -31% (Senna alata (L.) Roxb.) to +21% (Zamia skinneri Warsz. Ex. A. Dietr.), while all savanna species declined (up to -48%). After 10 min of drying, most species recovered Anet towards the observed status prior to wetting or surpassed it, with the exception of Quercus stellata Wangenh., a savanna species, which remained 13% below Anet dry. The combination of leaf wetness duration and leaf traits, such as stomatal density, trichomes or wax, most likely influenced Anet responses positively or negatively. There was also overlap between leaf traits and Anet responses of savanna and tropical plants. It is possible that these species converge on a relatively conservative response to wetness, each for divergent purposes (cooling, avoiding stomatal occlusion, or by several unique means of rapid drying). A better understanding of leaf wetness inhibiting photosynthesis is vital for accurate modeling of growth in forested environments; however, species adapted for wet environments may possess compensatory traits that mitigate these effects. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

[Transpiration of Choerospondias axillaris in agro-forestrial system and its affecting factors].

PubMed

Zhao, Ying; Zhang, Bin; Zhao, Huachun; Wang, Mingzhu

2005-11-01

Measurement of transpiration is essential to assess plant water use efficiency. Applying Grainer method, this paper measured the sap flow of Choerospondias axillaries in an agro-forestrial system, aimed to evaluate the effects of intercropping and pruning on the diurnal variation of transpiration, and to relate the transpiration rate with climatic factors. The results showed that the diurnal variation of Choerospondias arillaries transpiration rate appeared in parabola, low in the morning and evening, and high at noon. The transpiration rate was closely related to leaf stomatal conductivity and soil water potential, especially the water potential in 100 cm soil depth (R = 0.737). The transpiration rate of Choerospondias axillaries was increased by about 40% approximately 160% in agro-forestrial system through the changes in regional environment and in the deep soil water use by tree. Correlation analysis and multi-factor successive regression analysis indicated that the transpiration was controlled by ray radiation intensity, air temperature and ground temperature, followed by the difference between saturated and actual vapor pressure and the wind speed. A statistical model for calculating the sap flow rate by micrometeorological factors was also provided.

Leaf gas exchange of understory spruce-fir saplings in relict cloud forests, southern Appalachian Mountains, USA.

PubMed

Reinhardt, Keith; Smith, William K

2008-01-01

The southern Appalachian spruce-fir (Picea rubens Sarg. and Abies fraseri (Pursh) Poir.) forest is found only on high altitude mountain tops that receive copious precipitation ( > 2000 mm year(-1)) and experience frequent cloud immersion. These high-elevation, temperate rain forests are immersed in clouds on approximately 65% of the total growth season days and for 30-40% of a typical summer day, and cloud deposition accounts for up to 50% of their annual water budget. We investigated environmental influences on understory leaf gas exchange and water relations at two sites: Mt. Mitchell, NC (MM; 35 degrees 45'53'' N, 82 degrees 15'53'' W, 2028 m elevation) and Whitetop Mtn., VA (WT; 36 degrees 38'19'' N, 81 degrees 36'19'' W, 1685 m elevation). We hypothesized that the cool, moist and cloudy conditions at these sites exert a strong influence on leaf gas exchange. Maximum photosynthesis (A(max)) varied between 1.6 and 4.0 micromol CO(2) m(-2) s(-1) for both spruce and fir and saturated at irradiances between approximately 200 and 400 micromol m(-2) s(-1) at both sites. Leaf conductance (g) ranged between 0.05 and 0.25 mol m(-2) s(-1) at MM and between 0.15 and 0.40 mol m(-2) s(-1) at WT and was strongly associated with leaf-to-air vapor pressure difference (LAVD). At both sites, g decreased exponentially as LAVD increased, with an 80-90% reduction in g between 0 and 0.5 kPa. Predawn leaf water potentials remained between -0.25 and -0.5 MPa for the entire summer, whereas late afternoon values declined to between -1.25 and -1.75 MPa by late summer. Thus, leaf gas exchange appeared tightly coupled to the response of g to LAVD, which maintained high water status, even at the relatively low LAVD of these cloud forests. Moreover, the cloudy, humid environment of these refugial forests appears to exert a strong influence on tree leaf gas exchange and water relations. Because global climate change is predicted to increase regional cloud ceiling levels, more research on cloud impacts on carbon gain and water relations is needed to predict future impacts on these relict forests.

[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.

Asymmetric effects of native and exotic invasive shrubs on ecology of the West Nile virus vector Culex pipiens (Diptera: Culicidae).

PubMed

Gardner, Allison M; Allan, Brian F; Frisbie, Lauren A; Muturi, Ephantus J

2015-06-16

Exotic invasive plants alter the structure and function of native ecosystems and may influence the distribution and abundance of arthropod disease vectors by modifying habitat quality. This study investigated how invasive plants alter the ecology of Culex pipiens, an important vector of West Nile virus (WNV) in northeastern and midwestern regions of the United States. Field and laboratory experiments were conducted to test the hypothesis that three native leaf species (Rubus allegheniensis, blackberry; Sambucus canadensis, elderberry; and Amelanchier laevis, serviceberry), and three exotic invasive leaf species (Lonicera maackii, Amur honeysuckle; Elaeagnus umbellata, autumn olive; and Rosa multiflora, multiflora rose) alter Cx. pipiens oviposition site selection, emergence rates, development time, and adult body size. The relative abundance of seven bacterial phyla in infusions of the six leaf species also was determined using quantitative real-time polymerase chain reaction to test the hypothesis that variation in emergence, development, and oviposition site selection is correlated to differences in the diversity and abundance of bacteria associated with different leaf species, important determinants of nutrient quality and availability for mosquito larvae. Leaf detritus from invasive honeysuckle and autumn olive yielded significantly higher adult emergence rates compared to detritus from the remaining leaf species and honeysuckle alleviated the negative effects of intraspecific competition on adult emergence. Conversely, leaves of native blackberry acted as an ecological trap, generating high oviposition but low emergence rates. Variation in bacterial flora associated with different leaf species may explain this asymmetrical production of mosquitoes: emergence rates and oviposition rates were positively correlated to bacterial abundance and diversity, respectively. We conclude that the displacement of native understory plant species by certain invasive shrubs may increase production of Cx. pipiens with potential negative repercussions for human and wildlife health. These findings may be relevant to mosquito control and invasive plant management practices in the geographic range of Cx. pipiens. Further, our discovery of a previously unknown ecological trap for an important vector of WNV has the potential to lead to novel alternatives to conventional insecticides in mosquito control by exploiting the apparent "attract-kill" properties of this native plant species.

Boron excess affects photosynthesis and antioxidant apparatus of greenhouse Cucurbita pepo and Cucumis sativus.

PubMed

Landi, Marco; Remorini, Damiano; Pardossi, Alberto; Guidi, Lucia

2013-11-01

This study aimed to evaluate the behavior of zucchini (Cucurbita pepo L.) and cucumber (Cucumis sativus L.) under boron (B) excess. Plants were grown under greenhouse conditions in a sandy soil-peat mixture using a nutrient solution containing 0.2 (control), 10 and 20 mg L(-1) B. Visible symptoms were quantified and leaf B accumulation, gas exchanges, chlorophyll (Chl) a fluorescence, malondialdehyde by-products and antioxidants were investigated 20 days after the beginning of the treatments. Boron toxicity induced oxidative load and leaf necrotic burns coupled with the reduction of leaf growth and biomass accumulation in both species. Boron excess resulted in a decrease of Chl a/b ratio, potential (Fv/Fm) and actual (ΦPSII) PSII quantum efficiency, photosynthetic rate (Pn), stomatal conductance (gs), and transpiration (E) as well. A general stimulation of the antioxidant enzymes ascorbate peroxidase, catalase and superoxide dismutase was observed, and a significant increase in the oxidized form of ascorbate and glutathione was evidenced for treated plants of both species. A difference between the two species was observed: C. pepo appeared to be more sensitive to B stress being damaged at all B concentration. C. sativus grown at 10 mg L(-1) B in nutrient solution showed some down-regulated mechanisms, i.e. increase in Chl b content and a good photochemical PSII efficiency as well as a higher amount of constitutive antioxidant molecules, that, however, are not sufficient to contrast the negative effects of B.

Engineering starch accumulation by manipulation of phosphate metabolism of starch.

PubMed

Weise, Sean E; Aung, Kimberly; Jarou, Zach J; Mehrshahi, Payam; Li, Ziru; Hardy, Anna C; Carr, David J; Sharkey, Thomas D

2012-06-01

A new understanding of leaf starch degradation has emerged in the last 10 years. It has been shown that starch phosphorylation and dephosphorylation are critical components of this process. Glucan, water dikinase (GWD) (and phosphoglucan, water dikinase) adds phosphate to starch, and phosphoglucan phosphatase (SEX4) removes these phosphates. To explore the use of this metabolism to manipulate starch accumulation, Arabidopsis (Arabidopsis thaliana) plants were engineered by introducing RNAi constructs designed to reduce expression of AtGWD and AtSEX4. The timing of starch build-up was altered with ethanol-inducible and senescence-induced gene promoters. Ethanol induction of RNAi lines reduced transcript for AtGWD and AtSEX4 by 50%. The transgenic lines had seven times more starch than wild type at the end of the dark period but similar growth rates and total biomass. Elevated leaf starch content in maize leaves was engineered by making an RNAi construct against a gene in maize that appeared to be homologous to AtGWD. The RNAi construct was expressed using the constitutive ubiquitin promoter. Leaf starch content at the end of a night period in engineered maize plants was 20-fold higher than in untransformed plants with no impact on total plant biomass. We conclude that plants can be engineered to accumulate starch in the leaves with little impact on vegetative biomass. © 2012 The Authors. Plant Biotechnology Journal © 2012 Society for Experimental Biology, Association of Applied Biologists and Blackwell Publishing Ltd.

Resistance of cabbage (Brassica oleracea capitata group) crops to Mamestra brassicae.

PubMed

Cartea, M E; Francisco, M; Lema, M; Soengas, P; Velasco, P

2010-10-01

Twenty-one cabbage (Brassica oleracea capitata group) varieties, including 16 local varieties and five commercial hybrids, were screened for resistance to the moth Mamestra brassicae L. under natural and artificial conditions in northwestern Spain. Resistance was assessed as the proportion of damaged plants and damaged leaves, leaf feeding injury, and number of larvae present. Correlation coefficients among damage traits showed that a visual scale (general appearance rating) should be a useful indicator of resistance. Most local varieties were highly susceptible to M. brassicae, whereas the commercial hybrids tested were resistant in terms of head foliage consumption and number of larvae per plant. Performance of varieties was similar under natural and artificial infestation although some of them performed differently at each year. Three local varieties (MBG-BRS0057, MBG-BRS0074, and MBG-BRS0452) were highly susceptible at both natural and artificial infestation conditions being MBG-BRS0074 the most damaged variety. Two local varieties (MBG-BRS0402 and MBG-BRS0535) and commercial hybrids were identified as resistant or moderately resistant to M. brassicae. Among them, 'Corazón de Buey' and 'Cabeza negra' were the most resistant and produced compact heads. These varieties could be useful sources of resistance to obtain resistant varieties to M. brassicae or as donors of resistance to other Brassica crops. The possible role of leaf traits, head compactness, and leaf glucosinolate content in relation to M. brassicae resistance is discussed.

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

Hauser, H.D.; Walters, K.D.; Berg, V.S.

Plants in the field are frequently exposed to anthropogenic acid precipitation with pH values of 4 and below. For the acid to directly affect leaf tissues, it must pass through the leaf cuticle, but little is known about the permeability of cuticles to protons, of about the effect of different anions on this permeability. We investigated the movement of protons through isolated astomatous leaf cuticles of grapefruit (Citrus x paradisi Macfady.), rough lemon (Citrus limon [L.] Burm. fils cv Ponderosa), and pear (Pyrus communis L.) using hydrochloric, sulfuric, and nitric acids. Cuticles were enzymically isolated from leaves and placed inmore » a diffusion apparatus with pH 4 acid on the morphological outer surface of the cuticle and degassed distilled water on the inner surface. Changes in pH of the solution on the inner surface were used to determine rates of effective permeability of the cuticles to the protons of these acids. Most cuticles exhibited an initial low permeability, lasting hours to days, then after a short transition displayed a significant higher permeability, which persisted until equilibrium was approached. The change in effective permeability appears to be reversible. Effective permeabilities were higher for sulfuric acid than for the others. A model of the movement of protons through the cuticle is presented, proposing that dissociated acid groups in channels within the cutin are first protonated by the acid, accounting for the low initial effective permeability; then protons pass freely through the channels, resulting in a higher effective permeability. 26 refs., 6 figs., 2 tabs.« less

The Impacts of Phosphorus Deficiency on the Photosynthetic Electron Transport Chain.

PubMed

Carstensen, Andreas; Herdean, Andrei; Schmidt, Sidsel Birkelund; Sharma, Anurag; Spetea, Cornelia; Pribil, Mathias; Husted, Søren

2018-05-01

Phosphorus (P) is an essential macronutrient, and P deficiency limits plant productivity. Recent work showed that P deficiency affects electron transport to photosystem I (PSI), but the underlying mechanisms are unknown. Here, we present a comprehensive biological model describing how P deficiency disrupts the photosynthetic machinery and the electron transport chain through a series of sequential events in barley ( Hordeum vulgare ). P deficiency reduces the orthophosphate concentration in the chloroplast stroma to levels that inhibit ATP synthase activity. Consequently, protons accumulate in the thylakoids and cause lumen acidification, which inhibits linear electron flow. Limited plastoquinol oxidation retards electron transport to the cytochrome b 6 f complex, yet the electron transfer rate of PSI is increased under steady-state growth light and is limited under high-light conditions. Under P deficiency, the enhanced electron flow through PSI increases the levels of NADPH, whereas ATP production remains restricted and, hence, reduces CO 2 fixation. In parallel, lumen acidification activates the energy-dependent quenching component of the nonphotochemical quenching mechanism and prevents the overexcitation of photosystem II and damage to the leaf tissue. Consequently, plants can be severely affected by P deficiency for weeks without displaying any visual leaf symptoms. All of the processes in the photosynthetic machinery influenced by P deficiency appear to be fully reversible and can be restored in less than 60 min after resupply of orthophosphate to the leaf tissue. © 2018 American Society of Plant Biologists. All Rights Reserved.

Mechanisms of resistance to sulfur dioxide in the Cucurbitaceae

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

Bressan, R.A.; Wilson, L.G.; Filner, P.

1978-05-01

The relative resistance of four cultivars of the Cucurbitaceae (Cucumis sativus L. cv. National Pickling, and inbred line SC 25; Cucurbita pepo L. cv. Prolific Straightneck Squash, and cv. Small Sugar Pumpkin) to SO/sub 2/ was determined. According to plots of the degree of exposure to SO/sub 2/ (which depends on the SO/sub 2/ concentration and the duration of the exposure), there is an 8-fold difference in resistance to this toxic gas among these cultivars. However, if the degree of injury is plotted as a function of the amount of SO/sub 2/ absorbed, all four cultivars appear similarly sensitive tomore » the gas. We conclude that the principal reason for special and varietal differences in resistance among these cultivars is the relative rate of absorption of the gas. The densities of stomata on the upper and lower surfaces of leaves did not differ sufficiently between cultivars to account for the differences in absorption rates. It remains to be determined whether the differences in rate of SO/sub 2/ absorption reflect differences in stomatal activity. Resistance of individual leaves changes with position on the plant axis (age of the leaf). There exists a gradient of decreasing resistance from the apex downward. This resistance gradient cannot be accounted for by differences in rates of SO/sub 2/ absorption. We infer the existence of a biochemically based, developmentally controlled resistance mechanism which functions after SO/sub 2/ has entered the leaf. Biochemical comparisons of old and young leaves with such differences in resistance should be helpful in determining the biochemistry of SO/sub 2/ toxicity.« less

A Guide to Alaskan Black Spruce Wetland Bryophytes: Species Specific to Delineation for Interior and South Central Regions

DTIC Science & Technology

2008-06-01

rhizoids (hair-like filaments) at the base, all along the stem, or as clusters, and the rhizoids may be dense or sparse, colored or colorless (appearing...colorless rhizoids . They will only be present on the ventral side. The leaf arrangement is called succubous when the forward edge of a leaf (as viewed...camouflaged by rhizoids . Leaves of Blepharostoma trichophyllum. The leaves of Blepharostoma are very small and in three rows, and they look like

A Guide to Alaskan Black Spruce Wetland Bryophytes: Species Specific to Delineation for Interior and South Central Regions

DTIC Science & Technology

2008-01-01

spread far apart, all around the stem or more or less in one flattened plane, etc.) are useful key identifying characters. Stems may bear rhizoids ...hair-like filaments) at the base, all along the stem, or as clusters, and the rhizoids may be dense or sparse, colored or colorless (appearing white...colorless rhizoids . They will only be present on the ventral side. The leaf arrangement is called succubous when the forward edge of a leaf (as

Variation in levels of some leaf enzymes.

PubMed

Downton, J; Slatyer, R O

1971-03-01

Several procedures were compared for efficiency in the extraction of certain leaf enzymes (phosphoenolpyruvate carboxylase, ribulose 1,5-diphosphate carboxylase and malate dehydrogenase) in Atriplex hastata (a "C3" species exhibiting conventional photosynthetic metabolism), and in A. spongiosa (a "C4" species in which the initial photosynthetic products are C4 dicarboxylic acids). Glycolate oxidase was also assayed in some cases, and Atriplex nummularia and Sorghum bicolor were also used as test material. A simple procedure, involving a mortar and pestle grind with carborundum added to the grinding mixture, was found to be as effective as glass bead grind procedures. In addition, it was more rapid and showed less variability with different operations.Using the carborundum grind procedure, sources of variability in enzyme activity in apparently uniform leaves were compared, as were effects of time of day, leaf age and storage procedure. In general, if apparently uniform leaves could be selected, variability in levels of enzyme activity appeared to be relatively small, not exceeding about 12%. Time of day also appeared to be relatively unimportant for the enzymes examined. However, the ontogentic status of the plant was found to be an important source of variability. Leaf age was also a major source of variability where the activity was expressed on a fresh weight basis, but specific activity (i.e. activity expressed on a protein basis) was relatively constant, at least with the range of species and leaf ages examined here.Storage of fresh samples in liquid nitrogen for 24 h, prior to extraction and assay, led to only a small reduction in activity, but substantial changes occurred if storage was in dry ice or in ice and also where extracts were stored in a deep freeze.

Spatial Imaging, Speciation, and Quantification of Selenium in theHyperaccumulator Plants Astragalus bisulcatus and Stanleya pinnata

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

Freeman, J.L.; Zhang, L.H.; Marcus, M.A.

2006-09-01

Astragalus bisulcatus and Stanleya pinnata hyperaccumulate selenium (Se) up to 1% of plant dry weight. In the field, Se was mostly present in the young leaves and reproductive tissues of both hyperaccumulators. Microfocused scanning x-ray fluorescence mapping revealed that Se was hyperaccumulated in trichomes in young leaves of A. bisulcatus. None of 10 other elements tested were accumulated in trichomes. Micro x-ray absorption spectroscopy and liquid chromatography-mass spectrometry showed that Se in trichomes was present in the organic forms methylselenocysteine (MeSeCys; 53%) and {gamma}-glutamyl-MeSeCys (47%). In the young leaf itself, there was 30% inorganic Se (selenate and selenite) in additionmore » to 70% MeSeCys. In young S. pinnata leaves, Se was highly concentrated near the leaf edge and surface in globular structures that were shown by energy-dispersive x-ray microanalysis to be mainly in epidermal cells. Liquid chromatography-mass spectrometry revealed both MeSeCys (88%) and selenocystathionine (12%) inside leaf edges. In contrast, both the Se accumulator Brassica juncea and the nonaccumulator Arabidopsis thaliana accumulated Se in their leaf vascular tissues and mesophyll cells. Se in hyperaccumulators appears to be mobile in both the xylem and phloem because Se-treated S. pinnata was found to be highly toxic to phloem-feeding aphids, and MeSeCys was present in the vascular tissues of a S. pinnata young leaf petiole as well as in guttation fluid. The compartmentation of organic selenocompounds in specific storage areas in the plant periphery appears to be a unique property of Se hyperaccumulators. The high concentration of Se in the plant periphery may contribute to Se tolerance and may also serve as an elemental plant defense mechanism.« less

7 CFR 30.20 - Crude.

Code of Federal Regulations, 2011 CFR

2011-01-01

... AND STANDARDS Classification of Leaf Tobacco Covering Classes, Types and Groups of Grades § 30.20 Crude. A subdegree of maturity, crude leaves usually have the general appearance of being raw and...

7 CFR 30.20 - Crude.

Code of Federal Regulations, 2012 CFR

2012-01-01

... AND STANDARDS Classification of Leaf Tobacco Covering Classes, Types and Groups of Grades § 30.20 Crude. A subdegree of maturity, crude leaves usually have the general appearance of being raw and...

7 CFR 30.20 - Crude.

Code of Federal Regulations, 2013 CFR

2013-01-01

... AND STANDARDS Classification of Leaf Tobacco Covering Classes, Types and Groups of Grades § 30.20 Crude. A subdegree of maturity, crude leaves usually have the general appearance of being raw and...

7 CFR 30.20 - Crude.

Code of Federal Regulations, 2010 CFR

2010-01-01

... AND STANDARDS Classification of Leaf Tobacco Covering Classes, Types and Groups of Grades § 30.20 Crude. A subdegree of maturity, crude leaves usually have the general appearance of being raw and...

7 CFR 30.20 - Crude.

Code of Federal Regulations, 2014 CFR

2014-01-01

... AND STANDARDS Classification of Leaf Tobacco Covering Classes, Types and Groups of Grades § 30.20 Crude. A subdegree of maturity, crude leaves usually have the general appearance of being raw and...

The Properties of Terrestrial Laser System Intensity for Measuring Leaf Geometries: A Case Study with Conference Pear Trees (Pyrus Communis)

PubMed Central

Balduzzi, Mathilde A.F.; Van der Zande, Dimitry; Stuckens, Jan; Verstraeten, Willem W.; Coppin, Pol

2011-01-01

Light Detection and Ranging (LiDAR) technology can be a valuable tool for describing and quantifying vegetation structure. However, because of their size, extraction of leaf geometries remains complicated. In this study, the intensity data produced by the Terrestrial Laser System (TLS) FARO LS880 is corrected for the distance effect and its relationship with the angle of incidence between the laser beam and the surface of the leaf of a Conference Pear tree (Pyrus Commmunis) is established. The results demonstrate that with only intensity, this relationship has a potential for determining the angle of incidence with the leaves surface with a precision of ±5° for an angle of incidence smaller than 60°, whereas it is more variable for an angle of incidence larger than 60°. It appears that TLS beam footprint, leaf curvatures and leaf wrinkles have an impact on the relationship between intensity and angle of incidence, though, this analysis shows that the intensity of scanned leaves has a potential to eliminate ghost points and to improve their meshing. PMID:22319374

Seedling growth strategies in Bauhinia species: comparing lianas and trees.

PubMed

Cai, Zhi-Quan; Poorter, Lourens; Cao, Kun-Fang; Bongers, Frans

2007-10-01

Lianas are expected to differ from trees in their growth strategies. As a result these two groups of woody species will have different spatial distributions: lianas are more common in high light environments. This study determines the differences in growth patterns, biomass allocation and leaf traits in five closely related liana and tree species of the genus Bauhinia. Seedlings of two light-demanding lianas (Bauhinia tenuiflora and B. claviflora), one shade-tolerant liana (B. aurea), and two light-demanding trees (B. purpurea and B. monandra) were grown in a shadehouse at 25% of full sunlight. A range of physiological, morphological and biomass parameters at the leaf and whole plant level were compared among these five species. The two light-demanding liana species had higher relative growth rate (RGR), allocated more biomass to leaf production [higher leaf mass fraction (LMF) and higher leaf area ratio (LAR)] and stem mass fraction (SMF), and less biomass to the roots [root mass fraction (RMF)] than the two tree species. The shade-tolerant liana had the lowest RGR of all five species, and had a higher RMF, lower SMF and similar LMF than the two light-demanding liana species. The two light-demanding lianas had lower photosynthetic rates per unit area (A(area)) and similar photosynthetic rates per unit mass (A(mass)) than the trees. Across species, RGR was positively related to SLA, but not to LAR and A(area). It is concluded that the faster growth of light-demanding lianas compared with light-demanding trees is based on morphological parameters (SLA, LMF and LAR), and cannot be attributed to higher photosynthetic rates at the leaf level. The shade-tolerant liana exhibited a slow-growth strategy, compared with the light-demanding species.

Faster Rubisco Is the Key to Superior Nitrogen-Use Efficiency in NADP-Malic Enzyme Relative to NAD-Malic Enzyme C4 Grasses1

PubMed Central

Ghannoum, Oula; Evans, John R.; Chow, Wah Soon; Andrews, T. John; Conroy, Jann P.; von Caemmerer, Susanne

2005-01-01

In 27 C4 grasses grown under adequate or deficient nitrogen (N) supplies, N-use efficiency at the photosynthetic (assimilation rate per unit leaf N) and whole-plant (dry mass per total leaf N) level was greater in NADP-malic enzyme (ME) than NAD-ME species. This was due to lower N content in NADP-ME than NAD-ME leaves because neither assimilation rates nor plant dry mass differed significantly between the two C4 subtypes. Relative to NAD-ME, NADP-ME leaves had greater in vivo (assimilation rate per Rubisco catalytic sites) and in vitro Rubisco turnover rates (kcat; 3.8 versus 5.7 s−1 at 25°C). The two parameters were linearly related. In 2 NAD-ME (Panicum miliaceum and Panicum coloratum) and 2 NADP-ME (Sorghum bicolor and Cenchrus ciliaris) grasses, 30% of leaf N was allocated to thylakoids and 5% to 9% to amino acids and nitrate. Soluble protein represented a smaller fraction of leaf N in NADP-ME (41%) than in NAD-ME (53%) leaves, of which Rubisco accounted for one-seventh. Soluble protein averaged 7 and 10 g (mmol chlorophyll)−1 in NADP-ME and NAD-ME leaves, respectively. The majority (65%) of leaf N and chlorophyll was found in the mesophyll of NADP-ME and bundle sheath of NAD-ME leaves. The mesophyll-bundle sheath distribution of functional thylakoid complexes (photosystems I and II and cytochrome f) varied among species, with a tendency to be mostly located in the mesophyll. In conclusion, superior N-use efficiency of NADP-ME relative to NAD-ME grasses was achieved with less leaf N, soluble protein, and Rubisco having a faster kcat. PMID:15665246

Seedling Growth Strategies in Bauhinia Species: Comparing Lianas and Trees

PubMed Central

Cai, Zhi-Quan; Poorter, Lourens; Cao, Kun-Fang; Bongers, Frans

2007-01-01

Background and Aims Lianas are expected to differ from trees in their growth strategies. As a result these two groups of woody species will have different spatial distributions: lianas are more common in high light environments. This study determines the differences in growth patterns, biomass allocation and leaf traits in five closely related liana and tree species of the genus Bauhinia. Methods Seedlings of two light-demanding lianas (Bauhinia tenuiflora and B. claviflora), one shade-tolerant liana (B. aurea), and two light-demanding trees (B. purpurea and B. monandra) were grown in a shadehouse at 25 % of full sunlight. A range of physiological, morphological and biomass parameters at the leaf and whole plant level were compared among these five species. Key Results The two light-demanding liana species had higher relative growth rate (RGR), allocated more biomass to leaf production [higher leaf mass fraction (LMF) and higher leaf area ratio (LAR)] and stem mass fraction (SMF), and less biomass to the roots [root mass fraction (RMF)] than the two tree species. The shade-tolerant liana had the lowest RGR of all five species, and had a higher RMF, lower SMF and similar LMF than the two light-demanding liana species. The two light-demanding lianas had lower photosynthetic rates per unit area (Aarea) and similar photosynthetic rates per unit mass (Amass) than the trees. Across species, RGR was positively related to SLA, but not to LAR and Aarea. Conclusions It is concluded that the faster growth of light-demanding lianas compared with light-demanding trees is based on morphological parameters (SLA, LMF and LAR), and cannot be attributed to higher photosynthetic rates at the leaf level. The shade-tolerant liana exhibited a slow-growth strategy, compared with the light-demanding species. PMID:17720978

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...

Controls on mass loss and nitrogen dynamics of oak leaf litter along an urban-rural land-use gradient

Treesearch

Richard V. Pouyat; Margaret M. Carreiro

2003-01-01

Using reciprocal leaf litter transplants, we investigated the effects of contrasting environments (urban vs. rural) and intraspecific variations in oak leaf litter quality on mass loss rates and nitrogen (N) dynamics along an urban-rural gradient in the New York City metropolitan area. Differences in earthworm abundances and temperature had previously been documented...

Effects of nutrient addition on leaf chemistry, morphology, and photosynthetic capacity of three bog shrubs

Treesearch

Jill L. Bubier; Rose Smith; Sari Juutinen; Tim R. Moore; Rakesh Minocha; Stephanie Long; Subash Minocha

2011-01-01

Plants in nutrient-poor environments typically have low foliar nitrogen (N) concentrations, long-lived tissues with leaf traits designed to use nutrients efficiently, and low rates of photosynthesis. We postulated that increasing N availability due to atmospheric deposition would increase photosynthetic capacity, foliar N, and specific leaf area (SLA) of bog shrubs. We...

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...

Diurnal depression in leaf hydraulic conductance at ambient and elevated [CO2] reveals anisohydric water management in field-grown soybean

USDA-ARS?s Scientific Manuscript database

Diurnal cycles of photosynthesis and water use in field-grown soybean (Glycine max) are tied to light intensity and vapor pressure deficit (VPD). At high mid-day VPD, transpiration rates can lead to a decline in leaf water potential if leaf hydraulic conductance is insufficient to supply water to in...

Divergence in Patterns of Leaf Growth Polarity Is Associated with the Expression Divergence of miR396

PubMed Central

2015-01-01

Lateral appendages often show allometric growth with a specific growth polarity along the proximo-distal axis. Studies on leaf growth in model plants have identified a basipetal growth direction with the highest growth rate at the proximal end and progressively lower rates toward the distal end. Although the molecular mechanisms governing such a growth pattern have been studied recently, variation in leaf growth polarity and, therefore, its evolutionary origin remain unknown. By surveying 75 eudicot species, here we report that leaf growth polarity is divergent. Leaf growth in the proximo-distal axis is polar, with more growth arising from either the proximal or the distal end; dispersed with no apparent polarity; or bidirectional, with more growth contributed by the central region and less growth at either end. We further demonstrate that the expression gradient of the miR396-GROWTH-REGULATING FACTOR module strongly correlates with the polarity of leaf growth. Altering the endogenous pattern of miR396 expression in transgenic Arabidopsis thaliana leaves only partially modified the spatial pattern of cell expansion, suggesting that the diverse growth polarities might have evolved via concerted changes in multiple gene regulatory networks. PMID:26410303

Variations in the methane budget over the last two millennia

NASA Astrophysics Data System (ADS)

Derendorp, L.

2012-06-01

Leaf litter is available at the Earth’s surface in large quantities. During the decomposition of leaf litter, volatile compounds can be released into the atmosphere, where they potentially influence local air quality, atmospheric chemistry or the global climate. In this thesis the focus was on the emission of C2-C5 hydrocarbons, molecular hydrogen (H2), carbon monoxide (CO) and methyl chloride (CH3Cl) from leaf litter and the factors that control the emissions were investigated. For different plant species, the emission rates of several C2-C5 hydrocarbons increased with temperature between 20 and 100°C according to the Arrhenius relation. When leaf litter was irradiated with UV, the emission increased linearly with the intensity of the UV. UVB radiation was more efficient in the generation of hydrocarbons from leaf litter than UVA. A simple upscaling showed that C2-C5 hydrocarbon emissions from leaf litter are likely insignificant for their global budgets, but may have a small influence on atmospheric chemistry on the local scale. Senescent and dead plant material releases carbon monoxide (CO), methane and larger hydrocarbons upon heating or irradiation with UV, but emissions of hydrogen (H2) have not been reported. In this study, H2 was released from leaf litter of Sequoiadendron giganteum in detectable amounts at temperatures above 45°C, whereas CO was also emitted at ambient temperature. Leaf litter has been identified as a potentially important source of CH3Cl. However, the factors controlling the emissions are unclear. Laboratory experiments have been performed in which CH3Cl emissions were measured from leaf litter of different plant species. For each investigated plant species, the CH3Cl emission rate strongly increased with temperature according to the Arrhenius relation. However, at constant temperature, large differences between different plants were observed. Therefore, CH3Cl emissions were measured from halophyte leaf litter with a varying chloride content, but no significant correlation between the CH3Cl emission rate and the chloride content of the plant material was observed. A limited set of field experiments was performed in which CH3Cl emissions were measured. Leaf litter emitted CH3Cl, but only in periods with fresh leaf litter fall. Outside these periods, the flux from leaf litter was zero or even slightly negative. The CH3Cl emission rate increased with temperature, but the temperature increase did not follow the Arrhenius relation as was observed in the laboratory experiments. The global importance of leaf litter as a source of CH3Cl was investigated using the global chemistry transport model TM5. Forward simulations with different emission scenarios indicated that at station Trinidad Head (mid-latitudes of North America), a substantial seasonal emission from leaf litter was required to match the measured CH3Cl mixing ratios at this station. Inversions performed with the TM4-4D-Var system indicated that the main CH3Cl sources were located in the Tropics, whereas the mid- and high latitudes were only a minor source. Sensitivity studies performed to investigate the robustness of the optimized emissions indicated that more than 90% of the global net emissions was located in the Tropics.

Performance of a multi leaf collimator system for MR-guided radiation therapy.

PubMed

Cai, Bin; Li, Harold; Yang, Deshan; Rodriguez, Vivian; Curcuru, Austen; Wang, Yuhe; Wen, Jie; Kashani, Rojano; Mutic, Sasa; Green, Olga

2017-12-01

The purpose of this study was to investigate and characterize the performance of a Multi Leaf Collimator (MLC) designed for Cobalt-60 based MR-guided radiation therapy system in a 0.35 T magnetic field. The MLC design and unique assembly features in the ViewRay MRIdian system were first reviewed. The RF cage shielding of MLC motor and cables were evaluated using ACR phantoms with real-time imaging and quantified by signal-to-noise ratio. The dosimetric characterizations, including the leaf transmission, leaf penumbra, tongue-and-groove effect, were investigated using radiosensitive films. The output factor of MLC-defined fields was measured with ionization chambers for both symmetric fields from 2.1 × 2.1 cm 2 to 27.3 × 27.3 cm 2 and asymmetric fields from 10.5 × 10.5 cm 2 to 10.5 × 2.0 cm 2 . Multi leaf collimator (MLC) positional accuracy was assessed by delivering either a picket fence (PF) style pattern on radiochromic films with wire-jig phantom or double and triple-rectangular patterns on ArcCheck-MR (Sun Nuclear, Melbourne, FL, USA) with gamma analysis as the pass/fail indicator. Leaf speed tests were performed to assess the capability of full range leaf travel within manufacture's specifications. Multi leaf collimator plan delivery reproducibility was tested by repeatedly delivering both open fields and fields with irregular shaped segments over 1-month period. Comparable SNRs within 4% were observed for MLC moving and stationary plans on vendor-reconstructed images, and the direct k-space reconstructed images showed that the three SNRs are within 1%. The maximum leaf transmission for all three MLCs was less than 0.35% and the average leakage was 0.153 ± 0.006%, 0.151 ± 0.008%, and 0.159 ± 0.015% for head 1, 2, and 3, respectively. Both the leaf edge and leaf end penumbra showed comparable values within 0.05 cm, and the measured values are within 0.1 cm with TPS values. The leaf edge TG effect indicated 10% underdose and the leaf end TG showed a shifted dose distribution with 0.3 cm offset. The leaf positioning test showed a 0.2 cm accuracy in the PF style test, and a gamma passing rate above 96% was observed with a 3%/2 mm criteria when comparing the measured double/triple-rectangular pattern fluence with TPS calculated fluence. The average leaf speed when executing the test plan fell in a range from 1.86 to 1.95 cm/s. The measured and TPS calculated output factors were within 2% for squared fields and within 3% for rectangular fields. The reproducibility test showed the deviation of output factors were well within 2% for square fields and the gamma passing rate within 1.5% for fields with irregular segments. The Monte Carlo predicted output factors were within 2% compared to TPS values. 15 out of the 16 IMRT plans have gamma passing rate more than 98% compared to the TPS fluence with an average passing rate of 99.1 ± 0.6%. The MRIdian MLC has a good RF noise shielding design, low radiation leakage, good positioning accuracy, comparable TG effect, and can be modeled by an independent Monte Carlo calculation platform. © 2017 American Association of Physicists in Medicine.

Cuticular permeance in relation to wax and cutin development along the growing barley (Hordeum vulgare) leaf.

PubMed

Richardson, Andrew; Wojciechowski, Tobias; Franke, Rochus; Schreiber, Lukas; Kerstiens, Gerhard; Jarvis, Mike; Fricke, Wieland

2007-05-01

The developing leaf three of barley provides an excellent model system for the direct determination of relationships between amounts of waxes and cutin and cuticular permeance. Permeance of the cuticle was assessed via the time-course of uptake of either toluidine blue or (14)C-labelled benzoic acid ([(14)C] BA) along the length of the developing leaf. Toluidine blue uptake only occurred within the region 0-25 mm from the point of leaf insertion (POLI). Resistance--the inverse of permeance--to uptake of [(14)C] BA was determined for four leaf regions and was lowest in the region 10-20 mm above POLI. At 20-30 and 50-60 mm above POLI, it increased by factors of 6 and a further 32, respectively. Above the point of emergence of leaf three from the sheath of leaf two, which was 76-80 mm above POLI, resistance was as high as at 50-60 mm above POLI. GC-FID/MS analyses of wax and cutin showed that: (1) the initial seven fold increase in cuticular resistance coincided with increase in cutin coverage and appearance of waxes; (2) the second, larger and final increase in cuticle resistance was accompanied by an increase in wax coverage, whereas cutin coverage remained unchanged; (3) cutin deposition in barley leaf epidermis occurred in parallel with cell elongation, whereas deposition of significant amounts of wax commenced as cells ceased to elongate.

Estimating the Relative Water Content of Single Leaves from Optical Polarization Measurements

NASA Technical Reports Server (NTRS)

Vanderbilt, Vern; Daughtry, Craig; Dahlgren, Robert

2016-01-01

Remotely sensing the water status of plants and the water content of canopies remain long-term goals of remote sensing research. For monitoring canopy water status, existing approaches such as the Crop Water Stress Index and the Equivalent Water Thickness have limitations. The CWSI does not work well in humid regions, requires estimates of the vapor pressure deficit near the canopy during the remote sensing over-flight and, once stomata close, provides little information regarding the canopy water status. The EWI is based upon the physics of water-light interaction, not plant physiology. In this research, we applied optical polarization techniques to monitor the VISNIR light reflected from the leaf interior, R, as well as the leaf transmittance, T, as the relative water content (RWC) of corn (Zea mays) leaves decreased. Our results show that R and T both changed nonlinearly as each leaf dried, R increasing and T decreasing. Our results tie changes in the VISNIR R and T to leaf physiological changes linking the light scattered out of the drying leaf interior to its relative water content and to changes in leaf cellular structure and pigments. Our results suggest remotely sensing the physiological water status of a single leaf and perhaps of a plant canopy might be possible in the future. However, using our approach to estimate the water status of a leaf does not appear possible at present, because our results display too much variability that we do not yet understand.

Estimating the Relative Water Content of Single Leaves from Optical Polarization Measurements.

NASA Astrophysics Data System (ADS)

Vanderbilt, V. C.; Daughtry, C. S. T.; Dahlgren, R. P.

2016-12-01

Remotely sensing the water status of plants and the water content of canopies remain long term goals of remote sensing research. For monitoring canopy water status, existing approaches such as the Crop Water Stress Index and the Equivalent Water Thickness have limitations. The CWSI does not work well in humid regions, requires estimates of the vapor pressure deficit near the canopy during the remote sensing over-flight and, once stomata close, provides little information regarding the canopy water status. The EWI is based upon the physics of water-light interaction, not plant physiology. In this research, we applied optical polarization techniques to monitor the VIS/NIR light reflected from the leaf interior, R, as well as the leaf transmittance, T, as the relative water content (RWC) of corn (Zea mays) leaves decreased. Our results show that R and T both changed nonlinearly as each leaf dried, R increasing and T decreasing. Our results tie changes in the VIS/NIR R and T to leaf physiological changes - linking the light scattered out of the drying leaf interior to its relative water content and to changes in leaf cellular structure and pigments. Our results suggest remotely sensing the physiological water status of a single leaf - and perhaps of a plant canopy - might be possible in the future. However, using our approach to estimate the water status of a leaf does not appear possible at present, because our results display too much variability that we do not yet understand.

Factors influencing leaf litter decomposition: An intersite decomposition experiment across China

USGS Publications Warehouse

Zhou, G.; Guan, L.; Wei, X.; Tang, X.; Liu, S.; Liu, J.; Zhang, Dongxiao; Yan, J.

2008-01-01

The Long-Term Intersite Decomposition Experiment in China (hereafter referred to as LTIDE-China) was established in 2002 to study how substrate quality and macroclimate factors affect leaf litter decomposition. The LTIDE-China includes a wide variety of natural and managed ecosystems, consisting of 12 forest types (eight regional broadleaf forests, three needle-leaf plantations and one broadleaf plantation) at eight locations across China. Samples of mixed leaf litter from the south subtropical evergreen broadleaf forest in Dinghushan (referred to as the DHS sample) were translocated to all 12 forest types. The leaf litter from each of other 11 forest types was placed in its original forest to enable comparison of decomposition rates of DHS and local litters. The experiment lasted for 30 months, involving collection of litterbags from each site every 3 months. Our results show that annual decomposition rate-constants, as represented by regression fitted k-values, ranged from 0.169 to 1.454/year. Climatic factors control the decomposition rate, in which mean annual temperature and annual actual evapotranspiration are dominant and mean annual precipitation is subordinate. Initial C/N and N/P ratios were demonstrated to be important factors of regulating litter decomposition rate. Decomposition process may apparently be divided into two phases controlled by different factors. In our study, 0.75 years is believed to be the dividing line of the two phases. The fact that decomposition rates of DHS litters were slower than those of local litters may have been resulted from the acclimation of local decomposer communities to extraneous substrate. ?? 2008 Springer Science+Business Media B.V.

Worldwide variation in within-canopy photosynthetic acclimation: differences in temporal and environmental controls among plant functional types

NASA Astrophysics Data System (ADS)

Niinemets, Ülo; Keenan, Trevor

2017-04-01

Major light gradients, characteristically 10- to 50-fold, constitute the most prominent feature of plant canopies. These gradients drive within-canopy variation in foliage structural, chemical and physiological traits. As a key acclimation response to variation in light availability, foliage photosynthetic capacity per area (Aarea) increases with increasing light availability within the canopy, maximizing whole canopy photosynthesis. Recently, a worldwide database including 831 within-canopy gradients with standardized light estimates for 304 species belonging to major vascular plant functional types was constructed and within-canopy variation in photosynthetic acclimation was characterized (Niinemets Ü, Keenan TF, Hallik L (2015) Tansley review. A worldwide analysis of within-canopy variations in leaf structural, chemical and physiological traits across plant functional types. The New Phytologist 205: 973-993). However, the understanding of how within-canopy photosynthetic gradients vary during the growing season and in response to site and stand characteristics is still limited. Here we analyzed temporal, environmental and site (nutrient availability, stand density, ambient CO2 concentration, water availability) sources of variation in within-canopy photosynthetic acclimation in different plant functional types. Variation in key structural (leaf dry mass per unit area, MA), chemical (nitrogen content per dry mass, NM, and area, NA) and physiological (photosynthetic nitrogen use efficiency, EN) photosynthetic capacity per dry mass, Amass and area, Aarea) was examined. The analysis demonstrates major, typically 1.5-2-fold, time-, environment and site-dependent modifications in within-canopy variation in foliage photosynthetic capacity. However, the magnitude and direction of temporal and environmental variations in plasticity significantly varied among functional types. Species with longer leaf life span and low rates of canopy expansion or flush-type canopy formation had lower within canopy plasticity during the growing season and in response to environmental and site modifications than species with high rates of canopy expansion and leaf turnover. The fast canopy-expanding species that grow in highly dynamic light environments, actively modified Aarea by nitrogen reallocation among and partitioning within leaves. In contrast, species with low rate of leaf turnover generally exhibited a passive acclimation response with variation in Aarea primarily determined by light-dependent modifications in leaf structure during leaf growth. Due to limited reacclimation capacity in species with low leaf turnover, within-canopy variation in Aarea decreased with increasing leaf age in these species. Furthermore, the plasticity responded less to modifications in environmental and site characteristics than in species with faster leaf turnover. This analysis concludes that the rate of leaf turnover is the key trait determining the temporal variation and environmental responses of canopy photosynthetic acclimation.

Juvenile Rhus glabra leaves have higher temperatures and lower gas exchange rates than mature leaves when compared in the field during periods of high irradiance.

PubMed

Snider, John L; Choinski, John S; Wise, Robert R

2009-05-01

We sought to test the hypothesis that stomatal development determines the timing of gas exchange competency, which then influences leaf temperature through transpirationally driven leaf cooling. To test this idea, daily patterns of gas exchange and leaflet temperature were obtained from leaves of two distinctively different developmental stages of smooth sumac (Rhus glabra) grown in its native habitat. Juvenile and mature leaves were also sampled for ultrastructural studies of stomatal development. When plants were sampled in May-June, the hypothesis was supported: juvenile leaflets were (for part of the day) from 1.4 to 6.0 degrees C warmer than mature leaflets and as much as 2.0 degrees C above ambient air temperature with lower stomatal conductance and photosynthetic rates than mature leaflets. When measurements were taken from July to October, no significant differences were observed, although mature leaflet gas exchange rates declined to the levels of the juvenile leaves. The gas exchange data were supported by the observations that juvenile leaves had approximately half the number of functional stomata on a leaf surface area basis as did mature leaves. It was concluded that leaf temperature and stage of leaf development in sumac are strongly linked with the higher surface temperatures observed in juvenile leaflets in the early spring possibly being involved in promoting photosynthesis and leaf expansion when air temperatures are cooler.

Changes in hydraulic conductance cause the difference in growth response to short-term salt stress between salt-tolerant and -sensitive black gram (Vigna mungo) varieties.

PubMed

Win, Khin Thuzar; Oo, Aung Zaw; Ookawa, Taiichiro; Kanekatsu, Motoki; Hirasawa, Tadashii

2016-04-01

Black gram (Vigna mungo) is an important crop in Asia, However, most black gram varieties are salt-sensitive. The causes of varietal differences in salt-induced growth reduction between two black gram varieties, 'U-Taung-2' (salt-tolerant; BT) and 'Mut Pe Khaing To' (salt-sensitive; BS), were examined the potential for the first step toward the genetic improvement of salt tolerance. Seedlings grown in vermiculite irrigated with full-strength Hoagland solution were treated with 0mM NaCl (control) or 225 mM NaCl for up to 10 days. In the 225 mM NaCl treatment, plant growth rate, net assimilation rate, mean leaf area, leaf water potential, and leaf photosynthesis were reduced more in BS than in BT plants. Leaf water potential was closely related to leaf photosynthesis, net assimilation rate, and increase in leaf area. In response to salinity stress, hydraulic conductance of the root, stem, and petiole decreased more strongly in BS than in BT plants. The reduction in stem and petiole hydraulic conductance was caused by cavitation, whereas the reduction in root hydraulic conductance in BS plants was caused by a reduction in root surface area and hydraulic conductivity. We conclude that the different reduction in hydraulic conductance is a cause of the differences in the growth response between the two black gram varieties under short-term salt stress. Copyright © 2016 Elsevier GmbH. All rights reserved.

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.

Leaf Fertilizers Affect Survival and Behavior of the Neotropical Stingless Bee Friesella schrottkyi (Meliponini: Apidae: Hymenoptera).

PubMed

Rodrigues, Cleiton G; Krüger, Alexandra P; Barbosa, Wagner F; Guedes, Raul Narciso C

2016-04-11

The ongoing concern about bee decline has largely focused on honey bees and neonicotinoid insecticides, while native pollinators such as Neotropical stingless bees and agrochemicals such as other insecticide groups, pesticides in general, and fertilizers-especially leaf fertilizers-remain neglected as potential contributors to pollination decline. In an effort to explore this knowledge gap, we assessed the lethal and sublethal behavioral impact of heavy metal-containing leaf fertilizers in a native pollinator of ecological importance in the Neotropics: the stingless beeFriesella schrottkyi(Friese). Two leaf fertilizers-copper sulfate (24% Cu) and a micronutrient mix (Arrank L: 5% S, 5% Zn, 3% Mn, 0.6% Cu, 0.5% B, and 0.06% Mo)-were used in oral and contact exposure bioassays. The biopesticide spinosad and water were used as positive and negative controls, respectively. Copper sulfate compromised the survival of stingless bee workers, particularly with oral exposure, although less than spinosad under contact exposure. Sublethal exposure to both leaf fertilizers at their field rates also caused significant effects in exposed workers. Copper sulfate enhanced flight take-off on stingless bee workers, unlike workers exposed to the micronutrient mix. There was no significant effect of leaf fertilizers on the overall activity and walking behavior of worker bees. No significant effect was observed for the respiration rate of worker bees under contact exposure, but workers orally exposed to the micronutrient mix exhibited a reduced respiration rate. Therefore, leaf fertilizers do affectF. schrottkyi, what may also occur with other stingless bees, potentially compromising their pollination activity deserving attention. © The Authors 2016. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Acetylcholine causes rooting in leaf explants of in vitro raised tomato (Lycopersicon esculentum Miller) seedlings.

PubMed

Bamel, Kiran; Gupta, Shrish Chandra; Gupta, Rajendra

2007-05-30

The animal neurotransmitter acetylcholine (ACh) induces rooting and promotes secondary root formation in leaf explants of tomato (Lycopersicon esculentum Miller var. Pusa Ruby), cultured in vitro on Murashige and Skoog's medium. The roots originate from the midrib of leaf explants and resemble taproot. ACh at 10(-5) M was found to be the optimum over a wide range of effective concentrations between 10(-7) and 10(-3) M. The breakdown products, choline and acetate were ineffective even at 10(-3) M concentration. ACh appears to have a natural role in tomato rhizogenesis because exogenous application of neostigmine, an inhibitor of ACh hydrolysis, could mimic the effect of ACh. Neostigmine, if applied in combination with ACh, potentiated the ACh effect.

Leaf energy balance modelling as a tool to infer habitat preference in the early angiosperms.

PubMed

Lee, Alexandra P; Upchurch, Garland; Murchie, Erik H; Lomax, Barry H

2015-03-22

Despite more than a century of research, some key aspects of habitat preference and ecology of the earliest angiosperms remain poorly constrained. Proposed growth ecology has varied from opportunistic weedy species growing in full sun to slow-growing species limited to the shaded understorey of gymnosperm forests. Evidence suggests that the earliest angiosperms possessed low transpiration rates: gas exchange rates for extant basal angiosperms are low, as are the reconstructed gas exchange rates for the oldest known angiosperm leaf fossils. Leaves with low transpirational capacity are vulnerable to overheating in full sun, favouring the hypothesis that early angiosperms were limited to the shaded understorey. Here, modelled leaf temperatures are used to examine the thermal tolerance of some of the earliest angiosperms. Our results indicate that small leaf size could have mitigated the low transpirational cooling capacity of many early angiosperms, enabling many species to survive in full sun. We propose that during the earliest phases of the angiosperm leaf record, angiosperms may not have been limited to the understorey, and that some species were able to compete with ferns and gymnosperms in both shaded and sunny habitats, especially in the absence of competition from more rapidly growing and transpiring advanced lineages of angiosperms.

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.

Seedling growth and biomass allocation in relation to leaf habit and shade tolerance among 10 temperate tree species.

PubMed

Modrzyński, Jerzy; Chmura, Daniel J; Tjoelker, Mark G

2015-08-01

Initial growth of germinated seeds is an important life history stage, critical for establishment and succession in forests. Important questions remain regarding the differences among species in early growth potential arising from shade tolerance. In addition, the role of leaf habit in shaping relationships underlying shade tolerance-related differences in seedling growth remains unresolved. In this study we examined variation in morphological and physiological traits among seedlings of 10 forest tree species of the European temperate zone varying in shade tolerance and leaf habit (broadleaved winter-deciduous species vs needle-leaved conifers) during a 10-week period. Seeds were germinated and grown in a controlled environment simulating an intermediate forest understory light environment to resolve species differences in initial growth and biomass allocation. In the high-resource experimental conditions during the study, seedlings increased biomass allocation to roots at the cost of leaf biomass independent of shade tolerance and leaf habit. Strong correlations between relative growth rate (RGR), net assimilation rate (NAR), leaf area ratio (LAR), specific leaf area (SLA) and leaf mass fraction (LMF) indicate that physiology and biomass allocation were equally important determinants of RGR as plant structure and leaf morphology among these species. Our findings highlight the importance of seed mass- and seed size-related root morphology (specific root length-SRL) for shade tolerance during early ontogeny. Leaf and plant morphology (SLA, LAR) were more successful in explaining variation among species due to leaf habit than shade tolerance. In both broadleaves and conifers, shade-tolerant species had lower SRL and greater allocation of biomass to stems (stem mass fraction). Light-seeded shade-intolerant species with greater SRL had greater RGR in both leaf habit groups. However, the greatest plant mass was accumulated in the group of heavy-seeded shade-tolerant broadleaves. The results of our study suggest that the combinations of plant attributes enhancing growth under high light vary with shade tolerance, but differ between leaf habit groups. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Loblolly pine grown under elevated CO2 affects early instar pine sawfly performance.

PubMed

Williams, R S; Lincoln, D E; Thomas, R B

1994-06-01

Seedlings of loblolly pine Pinus taeda (L.), were grown in open-topped field chambers under three CO 2 regimes: ambient, 150 μl l -1 CO 2 above ambient, and 300 μl l -1 CO 2 above ambient. A fourth, non-chambered ambient treatment was included to assess chamber effects. Needles were used in 96 h feeding trials to determine the performance of young, second instar larvae of loblolly pine's principal leaf herbivore, red-headed pine sawfly, Neodiprion lecontei (Fitch). The relative consumption rate of larvae significantly increased on plants grown under elevated CO 2 , and needles grown in the highest CO 2 regime were consumed 21% more rapidly than needles grown in ambient CO 2 . Both the significant decline in leaf nitrogen content and the substantial increase in leaf starch content contributed to a significant increase in the starch:nitrogen ratio in plants grown in elevated CO 2 . Insect consumption rate was negatively related to leaf nitrogen content and positively related to the starch:nitrogen ratio. Of the four volatile leaf monoterpenes measured, only β-pinene exhibited a significant CO 2 effect and declined in plants grown in elevated CO 2 . Although consumption changed, the relative growth rates of larvae were not different among CO 2 treatments. Despite lower nitrogen consumption rates by larvae feeding on the plants grown in elevated CO 2 , nitrogen accumulation rates were the same for all treatments due to a significant increase in nitrogen utilization efficiency. The ability of this insect to respond at an early, potentially susceptible larval stage to poorer food quality and declining levels of a leaf monoterpene suggest that changes in needle quality within pines in future elevated-CO 2 atmospheres may not especially affect young insects and that tree-feeding sawflies may respond in a manner similar to herb-feeding lepidopterans.

Leaf Assemblages across the Cretaceous-Tertiary Boundary in the Raton Basin, New Mexico and Colorado

NASA Astrophysics Data System (ADS)

Wolfe, Jack A.; Upchurch, Garland R., Jr.

1987-08-01

Analyses of leaf megafossil and dispersed leaf cuticle assemblages indicate that major ecologic disruption and high rates of extinction occurred in plant communities at the Cretaceous-Tertiary boundary in the Raton Basin. In diversity increase, the early Paleocene vegetational sequence mimics normal short-term ecologic succession, but on a far longer time scale. No difference can be detected between latest Cretaceous and early Paleocene temperatures, but precipitation markedly increased at the boundary. Higher survival rate of deciduous versus evergreen taxa supports occurrence of a brief cold interval (<1 year), as predicted in models of an “impact winter.”

Interplay of growth rate and xylem plasticity for optimal coordination of carbon and hydraulic economies in Fraxinus ornus trees.

PubMed

Petit, Giai; Savi, Tadeja; Consolini, Martina; Anfodillo, Tommaso; Nardini, Andrea

2016-11-01

Efficient leaf water supply is fundamental for assimilation processes and tree growth. Renovating the architecture of the xylem transport system requires an increasing carbon investment while growing taller, and any deficiency of carbon availability may result in increasing hydraulic constraints to water flow. Therefore, plants need to coordinate carbon assimilation and biomass allocation to guarantee an efficient and safe long-distance transport system. We tested the hypothesis that reduced branch elongation rates together with carbon-saving adjustments of xylem anatomy hydraulically compensate for the reduction in biomass allocation to xylem. We measured leaf biomass, hydraulic and anatomical properties of wood segments along the main axis of branches in 10 slow growing (SG) and 10 fast growing (FG) Fraxinus ornus L. trees. Branches of SG trees had five times slower branch elongation rate (7 vs 35 cm year -1 ), and produced a higher leaf biomass (P < 0.0001) and thinner xylem rings with fewer but larger vessels (P < 0.0001). On the contrary, we found no differences between SG and FG trees in terms of leaf-specific conductivity (P > 0.05) and xylem safety (Ψ 50 ≈ -3.2 MPa). Slower elongation rate coupled with thinner annual rings and larger vessels allows the reduction of carbon costs associated with growth, while maintaining similar leaf-specific conductivity and xylem safety. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

Influence of vesicular arbuscular mycorrhizae and leaf age on net gas exchange of citrus leaves.

PubMed

Syvertsen, J P; Graham, J H

1990-11-01

The purpose of this study was to test the hypothesis that vesicular arbuscular mycorrhizal (VAM) fungi affect net assimilation of CO(2) (A) of different-aged citrus leaves independent of mineral nutrition effects of mycorrhizae. Citrus aurantium L., sour orange plants were grown for 6 months in a sandy soil low in phosphorus that was either infested with the VAM fungus, Glomus intraradices Schenck & Smith, or fertilized with additional phosphorus and left nonmycorrhizal (NM). Net CO(2) assimilation, stomatal conductance, water use efficiency, and mineral nutrient status for expanding, recently expanded, and mature leaves were evaluated as well as plant size and relative growth rate of leaves. Nutrient status and net gas exchange varied with leaf age. G. intraradices-inoculated plants had well-established colonization (79% of root length) and were comparable in relative growth rate and size at final harvest with NM plants. Leaf mineral concentrations were generally the same for VAM and NM plants except for nitrogen. Although leaf nitrogen was apparently sufficient for high rates of A, VAM plants did have higher nitrogen concentrations than NM at the time of gas exchange measurements. G. intraradices had no effect on A, stomatal conductance, or water use efficiency, irrespective of leaf age. These results show that well-established VAM colonization does not affect net gas exchange of citrus plants that are comparable in size, growth rate, and nutritional status with NM plants.

On the air cleansing efficiency of an extended green wall: a CFD analysis of mechanistic details of transport processes.

PubMed

Joshi, Saumitra V; Ghosh, Sat

2014-11-21

The detrimental impact of rising air pollution levels in urban landscapes has become conspicuous over the last decade, particularly in developing countries. This novel numerical study quantifies the cleansing efficiency of green façades draped with a copiously growing tropical creeper Vernonia elaeagnifolia. Turbulent transport of SO2 to the leaf boundary layer and subsequent diffusion across stomatal pores into the mesophyllic cells is modeled at the micro level, including its ionic dissociation in the leaf׳s interior. A SEM analysis indicates stomatal dimensions and density. Whilst previous studies have used either spatially averaged equations or resistance models, a spatially discretized computational approach is adopted in this study. The resulting concentration distribution is used to calculate the deposition velocity on stomatal pores, which is then extrapolated over the entire façade to yield bulk pollutant removal rates. A deposition velocity of 1.53mms(-1) and 0.72mms(-1) is obtained for open and closed pores respectively, with removal rates equal to 1.11×10(-6)s(-1) and 1.05×10(-6)s(-1) for dry and humid weather respectively. Sensitivity studies on the removal rate are carried out based on humidity, stomatal aperture and leaf temperature. The removal rate dependence on the Leaf Area Index (LAI) is also investigated. It is inferred from simulations that vegetated façades are efficient at mitigation of residual pollution. Copyright © 2014 Elsevier Ltd. All rights reserved.

Gas exchange recovery following natural drought is rapid unless limited by loss of leaf hydraulic conductance: evidence from an evergreen woodland.

PubMed

Skelton, Robert P; Brodribb, Timothy J; McAdam, Scott A M; Mitchell, Patrick J

2017-09-01

Drought can cause major damage to plant communities, but species damage thresholds and postdrought recovery of forest productivity are not yet predictable. We used an El Niño drought event as a natural experiment to test whether postdrought recovery of gas exchange could be predicted by properties of the water transport system, or if metabolism, primarily high abscisic acid concentration, might delay recovery. We monitored detailed physiological responses, including shoot sapflow, leaf gas exchange, leaf water potential and foliar abscisic acid (ABA), during drought and through the subsequent rehydration period for a sample of eight canopy and understory species. Severe drought caused major declines in leaf water potential, elevated foliar ABA concentrations and reduced stomatal conductance and assimilation rates in our eight sample species. Leaf water potential surpassed levels associated with incipient loss of leaf hydraulic conductance in four species. Following heavy rainfall gas exchange in all species, except those trees predicted to have suffered hydraulic impairment, recovered to prestressed rates within 1 d. Recovery of plant gas exchange was rapid and could be predicted by the hydraulic safety margin, providing strong support for leaf vulnerability to water deficit as an index of damage under natural drought conditions. © 2017 The Authors. New Phytologist © 2017 New Phytologist Trust.

Acclimation of Foliar Respiration and Photosynthesis in Response to Experimental Warming in a Temperate Steppe in Northern China

PubMed Central

Chi, Yonggang; Xu, Ming; Shen, Ruichang; Yang, Qingpeng; Huang, Bingru; Wan, Shiqiang

2013-01-01

Background Thermal acclimation of foliar respiration and photosynthesis is critical for projection of changes in carbon exchange of terrestrial ecosystems under global warming. Methodology/Principal Findings A field manipulative experiment was conducted to elevate foliar temperature (T leaf) by 2.07°C in a temperate steppe in northern China. R d/T leaf curves (responses of dark respiration to T leaf), A n/T leaf curves (responses of light-saturated net CO2 assimilation rates to T leaf), responses of biochemical limitations and diffusion limitations in gross CO2 assimilation rates (A g) to T leaf, and foliar nitrogen (N) concentration in Stipa krylovii Roshev. were measured in 2010 (a dry year) and 2011 (a wet year). Significant thermal acclimation of R d to 6-year experimental warming was found. However, A n had a limited ability to acclimate to a warmer climate regime. Thermal acclimation of R d was associated with not only the direct effects of warming, but also the changes in foliar N concentration induced by warming. Conclusions/Significance Warming decreased the temperature sensitivity (Q 10) of the response of R d/A g ratio to T leaf. Our findings may have important implications for improving ecosystem models in simulating carbon cycles and advancing understanding on the interactions between climate change and ecosystem functions. PMID:23457574

A mutation that eliminates bundle sheath extensions reduces leaf hydraulic conductance, stomatal conductance and assimilation rates in tomato (Solanum lycopersicum).

PubMed

Zsögön, Agustin; Negrini, Ana Clarissa Alves; Peres, Lázaro Eustáquio Pereira; Nguyen, Hoa Thi; Ball, Marilyn C

2015-01-01

Bundle sheath extensions (BSEs) are key features of leaf structure whose distribution differs among species and ecosystems. The genetic control of BSE development is unknown, so BSE physiological function has not yet been studied through mutant analysis. We screened a population of ethyl methanesulfonate (EMS)-induced mutants in the genetic background of the tomato (Solanum lycopersicum) model Micro-Tom and found a mutant lacking BSEs. The leaf phenotype of the mutant strongly resembled the tomato mutant obscuravenosa (obv). We confirmed that obv lacks BSEs and that it is not allelic to our induced mutant, which we named obv-2. Leaves lacking BSEs had lower leaf hydraulic conductance and operated with lower stomatal conductance and correspondingly lower assimilation rates than wild-type leaves. This lower level of function occurred despite similarities in vein density, midvein vessel diameter and number, stomatal density, and leaf area between wild-type and mutant leaves, the implication being that the lack of BSEs hindered water dispersal within mutant leaves. Our results comparing near-isogenic lines within a single species confirm the hypothesised role of BSEs in leaf hydraulic function. They further pave the way for a genetic model-based analysis of a common leaf structure with deep ecological consequences. © 2014 The Authors New Phytologist © 2014 New Phytologist Trust.

Tree leaf control on low flow water quality in a small Virginia stream

USGS Publications Warehouse

Slack, K.V.; Feltz, H.R.

1968-01-01

Impaired water quality in a small stream was related to autumn leaf fall from riparian vegetation. Dissolved oxygen and pH decreased, and water color, specific conductance, iron, manganese, and bicarbonate values increased as the rate of leaf fall increased. Similar quality changes occurred in laboratory cultures of tree leaves in filtered stream water, but the five leaf species studied produced widely differing results. Stream quality improved rapidly following channel flushing by storm flow. Organic loading by tree litter can exert significant control on water composition, especially during low flow.

A trait-based trade-off between growth and mortality: evidence from 15 tropical tree species using size-specific relative growth rates

PubMed Central

Philipson, Christopher D; Dent, Daisy H; O’Brien, Michael J; Chamagne, Juliette; Dzulkifli, Dzaeman; Nilus, Reuben; Philips, Sam; Reynolds, Glen; Saner, Philippe; Hector, Andy

2014-01-01

A life-history trade-off between low mortality in the dark and rapid growth in the light is one of the most widely accepted mechanisms underlying plant ecological strategies in tropical forests. Differences in plant functional traits are thought to underlie these distinct ecological strategies; however, very few studies have shown relationships between functional traits and demographic rates within a functional group. We present 8 years of growth and mortality data from saplings of 15 species of Dipterocarpaceae planted into logged-over forest in Malaysian Borneo, and the relationships between these demographic rates and four key functional traits: wood density, specific leaf area (SLA), seed mass, and leaf C:N ratio. Species-specific differences in growth rates were separated from seedling size effects by fitting nonlinear mixed-effects models, to repeated measurements taken on individuals at multiple time points. Mortality data were analyzed using binary logistic regressions in a mixed-effects models framework. Growth increased and mortality decreased with increasing light availability. Species differed in both their growth and mortality rates, yet there was little evidence for a statistical interaction between species and light for either response. There was a positive relationship between growth rate and the predicted probability of mortality regardless of light environment, suggesting that this relationship may be driven by a general trade-off between traits that maximize growth and traits that minimize mortality, rather than through differential species responses to light. Our results indicate that wood density is an important trait that indicates both the ability of species to grow and resistance to mortality, but no other trait was correlated with either growth or mortality. Therefore, the growth mortality trade-off among species of dipterocarp appears to be general in being independent of species crossovers in performance in different light environments. PMID:25478157

How did the swiss cheese plant get its holes?

PubMed

Muir, Christopher D

2013-02-01

Adult leaf fenestration in "Swiss cheese" plants (Monstera Adans.) is an unusual leaf shape trait lacking a convincing evolutionary explanation. Monstera are secondary hemiepiphytes that inhabit the understory of tropical rainforests, where photosynthesis from sunflecks often makes up a large proportion of daily carbon assimilation. Here I present a simple model of leaf-level photosynthesis and whole-plant canopy dynamics in a stochastic light environment. The model demonstrates that leaf fenestration can reduce the variance in plant growth and thereby increase geometric mean fitness. This growth-variance hypothesis also suggests explanations for conspicuous ontogenetic changes in leaf morphology (heteroblasty) in Monstera, as well as the absence of leaf fenestration in co-occurring juvenile tree species. The model provides a testable hypothesis of the adaptive significance of a unique leaf shape and illustrates how variance in growth rate could be an important factor shaping plant morphology and physiology.

Endophytic fungi reduce leaf-cutting ant damage to seedlings

PubMed Central

Bittleston, L. S.; Brockmann, F.; Wcislo, W.; Van Bael, S. A.

2011-01-01

Our study examines how the mutualism between Atta colombica leaf-cutting ants and their cultivated fungus is influenced by the presence of diverse foliar endophytic fungi (endophytes) at high densities in tropical leaf tissues. We conducted laboratory choice trials in which ant colonies chose between Cordia alliodora seedlings with high (Ehigh) or low (Elow) densities of endophytes. The Ehigh seedlings contained 5.5 times higher endophyte content and a greater diversity of fungal morphospecies than the Elow treatment, and endophyte content was not correlated with leaf toughness or thickness. Leaf-cutting ants cut over 2.5 times the leaf area from Elow relative to Ehigh seedlings and had a tendency to recruit more ants to Elow plants. Our findings suggest that leaf-cutting ants may incur costs from cutting and processing leaves with high endophyte loads, which could impact Neotropical forests by causing variable damage rates within plant communities. PMID:20610420

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.

Leaf physiological versus morphological acclimation to high-light exposure at different stages of foliar development in oak.

PubMed

Rodríguez-Calcerrada, J; Reich, P B; Rosenqvist, E; Pardos, J A; Cano, F J; Aranda, I

2008-05-01

We investigated light acclimation in seedlings of the temperate oak Quercus petraea (Matt.) Liebl. and the co-occurring sub-Mediterranean oak Quercus pyrenaica Willd. Seedlings were raised in a greenhouse for 1 year in either 70 (HL) or 5.3% (LL) of ambient irradiance of full sunlight, and, in the following year, subsets of the LL-grown seedlings were transferred to HL either before leaf flushing (LL-HLBF plants) or after full leaf expansion (LL-HLAF plants). Gas exchange, chlorophyll a fluorescence, nitrogen fractions in photosynthetic components and leaf anatomy were examined in leaves of all seedlings 5 months after plants were moved from LL to HL. Differences between species in the acclimation of LL-grown plants to HL were minor. For LL-grown plants in HL, area-based photosynthetic capacity, maximum rate of carboxylation, maximum rate of electron transport and the effective photochemical quantum yield of photosystem II were comparable to those for plants grown solely in HL. A rapid change in nitrogen distribution among photosynthetic components was observed in LL-HLAF plants, which had the highest photosynthetic nitrogen-use efficiency. Increases in mesophyll thickness and dry mass per unit area governed leaf acclimation in LL-HLBF plants, which tended to have less nitrogen in photosynthetic components and a lower assimilation potential per unit of leaf mass or nitrogen than LL-HLAF plants. The data indicate that the phenological state of seedlings modified the acclimatory response of leaf attributes to increased irradiance. Morphological adaptation of leaves of LL-HLBF plants enhanced photosynthetic capacity per unit leaf area, but not per unit leaf dry mass, whereas substantial redistribution of nitrogen among photosynthetic components in leaves of LL-HLAF plants enhanced both mass- and area-based photosynthetic capacity.

Gas exchange and leaf aging in an evergreen oak: causes and consequences for leaf carbon balance and canopy respiration.

PubMed

Rodríguez-Calcerrada, Jesús; Limousin, Jean-Marc; Martin-StPaul, Nicolas K; Jaeger, Carsten; Rambal, Serge

2012-04-01

Leaves of Mediterranean evergreens experience large variations in gas exchange rates over their life span due to aging and seasonally changing environmental conditions. Accounting for the changing respiratory physiology of leaves over time will help improve estimations of leaf and whole-plant carbon balances. Here we examined seasonal variations in light-saturated net CO(2) assimilation (A(max)), dark respiration (R(d)) and the proportional change in R(d) per 10 °C change in temperature (Q(10) of R(d)) in previous-year (PY) and current-year (CY) leaves of the broadleaved evergreen tree Quercus ilex L. A(max) and R(d) were lower in PY than in CY leaves. Differences in nitrogen between cohorts only partly explained such differences, and rates of A(max) and R(d) expressed per unit of leaf nitrogen were still significantly different between cohorts. The decline in A(max) in PY leaves did not result in the depletion of total non-structural carbohydrates, whose concentration was in fact higher in PY than CY leaves. Leaf-level carbon balance modeled from gas exchange data was positive at all ages. Q(10) of R(d) did not differ significantly between leaf cohorts; however, failure to account for distinct R(d) between cohorts misestimated canopy leaf respiration by 13% across dates when scaling up leaf measurements to the canopy. In conclusion, the decline in A(max) in old leaves that are close to or exceed their mean life span does not limit the availability of carbohydrates, which are probably needed to sustain new growth, as well as R(d) and nutrient resorption during senescence. Accounting for leaf age as a source of variation of R(d) improves the estimation of foliar respiratory carbon release at the stand scale.

Anticonvulsant effect of Persea americana Mill (Lauraceae) (Avocado) leaf aqueous extract in mice.

PubMed

Ojewole, John A O; Amabeoku, George J

2006-08-01

Various morphological parts of Persea americana Mill (Lauraceae) (avocado) are widely used in African traditional medicines for the treatment, management and/or control of a variety of human ailments, including childhood convulsions and epilepsy. This study examined the anticonvulsant effect of the plant's leaf aqueous extract (PAE, 50-800 mg/kg i.p.) against pentylenetetrazole (PTZ)-, picrotoxin (PCT)- and bicuculline (BCL)-induced seizures in mice. Phenobarbitone and diazepam were used as reference anticonvulsant drugs for comparison. Like the reference anticonvulsant agents used, Persea americana leaf aqueous extract (PAE, 100-800 mg/kg i.p.) significantly (p < 0.05-0.001) delayed the onset of, and antagonized, pentylenetetrazole (PTZ)-induced seizures. The plant's leaf extract (PAE, 100-800 mg/kg i.p.) also profoundly antagonized picrotoxin (PCT)-induced seizures, but only weakly antagonized bicuculline (BCL)-induced seizures. Although the data obtained in the present study do not provide conclusive evidence, it would appear that 'avocado' leaf aqueous extract (PAE) produces its anticonvulsant effect by enhancing GABAergic neurotransmission and/or action in the brain. The findings of this study indicate that Persea americana leaf aqueous extract possesses an anticonvulsant property, and thus lends pharmacological credence to the suggested ethnomedical uses of the plant in the management of childhood convulsions and epilepsy.

Errors in Measuring Water Potentials of Small Samples Resulting from Water Adsorption by Thermocouple Psychrometer Chambers 1

PubMed Central

Bennett, Jerry M.; Cortes, Peter M.

1985-01-01

The adsorption of water by thermocouple psychrometer assemblies is known to cause errors in the determination of water potential. Experiments were conducted to evaluate the effect of sample size and psychrometer chamber volume on measured water potentials of leaf discs, leaf segments, and sodium chloride solutions. Reasonable agreement was found between soybean (Glycine max L. Merr.) leaf water potentials measured on 5-millimeter radius leaf discs and large leaf segments. Results indicated that while errors due to adsorption may be significant when using small volumes of tissue, if sufficient tissue is used the errors are negligible. Because of the relationship between water potential and volume in plant tissue, the errors due to adsorption were larger with turgid tissue. Large psychrometers which were sealed into the sample chamber with latex tubing appeared to adsorb more water than those sealed with flexible plastic tubing. Estimates are provided of the amounts of water adsorbed by two different psychrometer assemblies and the amount of tissue sufficient for accurate measurements of leaf water potential with these assemblies. It is also demonstrated that water adsorption problems may have generated low water potential values which in prior studies have been attributed to large cut surface area to volume ratios. PMID:16664367

Errors in measuring water potentials of small samples resulting from water adsorption by thermocouple psychrometer chambers.

PubMed

Bennett, J M; Cortes, P M

1985-09-01

The adsorption of water by thermocouple psychrometer assemblies is known to cause errors in the determination of water potential. Experiments were conducted to evaluate the effect of sample size and psychrometer chamber volume on measured water potentials of leaf discs, leaf segments, and sodium chloride solutions. Reasonable agreement was found between soybean (Glycine max L. Merr.) leaf water potentials measured on 5-millimeter radius leaf discs and large leaf segments. Results indicated that while errors due to adsorption may be significant when using small volumes of tissue, if sufficient tissue is used the errors are negligible. Because of the relationship between water potential and volume in plant tissue, the errors due to adsorption were larger with turgid tissue. Large psychrometers which were sealed into the sample chamber with latex tubing appeared to adsorb more water than those sealed with flexible plastic tubing. Estimates are provided of the amounts of water adsorbed by two different psychrometer assemblies and the amount of tissue sufficient for accurate measurements of leaf water potential with these assemblies. It is also demonstrated that water adsorption problems may have generated low water potential values which in prior studies have been attributed to large cut surface area to volume ratios.

Comparative morphology of leaf epidermis in eight populations of Atlas Pistachio (Pistacia atlantica Desf., Anacardiaceae).

PubMed

Belhadj, Safia; Derridj, Arezki; Aigouy, Thierry; Gers, Charles; Gauquelin, Thierry; Mevy, Jean-Philippe

2007-10-01

A comparative analysis was undertaken to conduct a micromorphological study of Pistacia atlantica leaves by comparing different populations grown under different climatic conditions. Leaf epidermis of eight wild populations was investigated under scanning electron microscope. Micromorphological characteristics (epidermis ornament, stomata type, waxes as well as trichomes) of the adaxial and abaxial leaf surfaces were examined. The epidermis ornament varied among populations and leaf surface, the abaxial leaf surface is reticulate with a striate surface. Messaad site shows a smooth uneven surface. The adaxial leaf surface is smooth but several ornamentations can be seen. The leaflet is amphistomatic; the stomata appeared to be slightly sunken. A variety of stomatal types were recorded; actinocytic and anomocytic types are the most frequent. The indumentum consisted of glandular and nonglandular trichomes. Unicellular glandular trichomes are recorded for P. atlantica leaves in this study. Their density is higher in Oued safene site, located at the highest altitude in comparison with the other populations. The wax occurred in all the sites and its pattern varied according to the populations studied, particularly between Berriane and Messaad. The morphological variability exhibited by the eight populations of P. atlantica may be interpreted as relevant to the ecological plasticity and the physiological mechanisms involved are discussed in this report.

Divergence in cryptic leaf colour provides local camouflage in an alpine plant.

PubMed

Niu, Yang; Chen, Zhe; Stevens, Martin; Sun, Hang

2017-10-11

The efficacy of camouflage through background matching is highly environment-dependent, often resulting in intraspecific colour divergence in animals to optimize crypsis in different visual environments. This phenomenon is largely unexplored in plants, although several lines of evidence suggest they do use crypsis to avoid damage by herbivores. Using Corydalis hemidicentra, an alpine plant with cryptic leaf colour, we quantified background matching between leaves and surrounding rocks in five populations based on an approximate model of their butterfly enemy's colour perception. We also investigated the pigment basis of leaf colour variation and the association between feeding risk and camouflage efficacy. We show that plants exhibit remarkable colour divergence between populations, consistent with differences in rock appearances. Leaf colour varies because of a different quantitative combination of two basic pigments-chlorophyll and anthocyanin-plus different air spaces. As expected, leaf colours are better matched against their native backgrounds than against foreign ones in the eyes of the butterfly. Furthermore, improved crypsis tends to be associated with a higher level of feeding risk. These results suggest that divergent cryptic leaf colour may have evolved to optimize local camouflage in various visual environments, extending our understanding of colour evolution and intraspecific phenotype diversity in plants. © 2017 The Author(s).

Temporal development of the barley leaf metabolic response to Pi limitation.

PubMed

Alexova, Ralitza; Nelson, Clark J; Millar, A Harvey

2017-05-01

The response of plants to P i limitation involves interplay between root uptake of P i , adjustment of resource allocation to different plant organs and increased metabolic P i use efficiency. To identify potentially novel, early-responding, metabolic hallmarks of P i limitation in crop plants, we studied the metabolic response of barley leaves over the first 7 d of P i stress, and the relationship of primary metabolites with leaf P i levels and leaf biomass. The abundance of leaf P i , Tyr and shikimate were significantly different between low Pi and control plants 1 h after transfer of the plants to low P i . Combining these data with 15 N metabolic labelling, we show that over the first 48 h of P i limitation, metabolic flux through the N assimilation and aromatic amino acid pathways is increased. We propose that together with a shift in amino acid metabolism in the chloroplast a transient restoration of the energetic and redox state of the leaf is achieved. Correlation analysis of metabolite abundances revealed a central role for major amino acids in P i stress, appearing to modulate partitioning of soluble sugars between amino acid and carboxylate synthesis, thereby limiting leaf biomass accumulation when external P i is low. © 2016 John Wiley & Sons Ltd.

Maple leaf (Acer sp.) extract mediated green process for the functionalization of ZnO powders with silver nanoparticles.

PubMed

Vivekanandhan, Singaravelu; Schreiber, Makoto; Mason, Cynthia; Mohanty, Amar Kumar; Misra, Manjusri

2014-01-01

The functionalization of ZnO powders with silver nanoparticles (AgNPs) through a novel maple leaf extract mediated biological process was demonstrated. Maple leaf extract was found to be a very effective bioreduction agent for the reduction of silver ions. The reduction rate of Ag(+) into Ag(0) was found to be much faster than other previously reported bioreduction rates and was comparable to the reduction rates obtained through chemical means. The functionalization of ZnO particles with silver nanoparticles through maple leaf extract mediated bioreduction of silver was investigated through UV-visible spectrophotometry, transmission electron microscopy (TEM), and X-ray diffraction analysis. It was found that the ZnO particles were coated with silver nanoparticles 5-20 nm in diameter. The photocatalytic ability of the ZnO particles functionalized with silver nanoparticles was found to be significantly improved compared to the photocatalytic ability of the neat ZnO particles. The silver functionalized ZnO particles reached 90% degradation of the dye an hour before the neat ZnO particles. Copyright © 2013 Elsevier B.V. All rights reserved.

Leaf Evolution: Gases, Genes and Geochemistry

PubMed Central

BEERLING, DAVID J.

2005-01-01

• Aims This Botanical Briefing reviews how the integration of palaeontology, geochemistry and developmental biology is providing a new mechanistic framework for interpreting the 40- to 50-million-year gap between the origination of vascular land plants and the advent of large (megaphyll) leaves, a long-standing puzzle in evolutionary biology. • Scope Molecular genetics indicates that the developmental mechanisms required for leaf production in vascular plants were recruited long before the advent of large megaphylls. According to theory, this morphogenetic potential was only realized as the concentration of atmospheric CO2 declined during the late Palaeozoic. Surprisingly, plants effectively policed their own evolution since the decrease in CO2 was brought about as terrestrial floras evolved accelerating the rate of silicate rock weathering and enhancing sedimentary organic carbon burial, both of which are long-term sinks for CO2. • Conclusions The recognition that plant evolution responds to and influences CO2 over millions of years reveals the existence of an intricate web of vegetation feedbacks regulating the long-term carbon cycle. Several of these feedbacks destabilized CO2 and climate during the late Palaeozoic but appear to have quickened the pace of terrestrial plant and animal evolution at that time. PMID:15965270

Leaf evolution: gases, genes and geochemistry.

PubMed

Beerling, David J

2005-09-01

This Botanical Briefing reviews how the integration of palaeontology, geochemistry and developmental biology is providing a new mechanistic framework for interpreting the 40- to 50-million-year gap between the origination of vascular land plants and the advent of large (megaphyll) leaves, a long-standing puzzle in evolutionary biology. Molecular genetics indicates that the developmental mechanisms required for leaf production in vascular plants were recruited long before the advent of large megaphylls. According to theory, this morphogenetic potential was only realized as the concentration of atmospheric CO2 declined during the late Palaeozoic. Surprisingly, plants effectively policed their own evolution since the decrease in CO2 was brought about as terrestrial floras evolved accelerating the rate of silicate rock weathering and enhancing sedimentary organic carbon burial, both of which are long-term sinks for CO2. The recognition that plant evolution responds to and influences CO(2) over millions of years reveals the existence of an intricate web of vegetation feedbacks regulating the long-term carbon cycle. Several of these feedbacks destabilized CO2 and climate during the late Palaeozoic but appear to have quickened the pace of terrestrial plant and animal evolution at that time.

Relationship of host recurrence in fungi to rates of tropical leaf decomposition

Treesearch

Mirna E. Santanaa; JeanD. Lodgeb; Patricia Lebowc

2004-01-01

Here we explore the significance of fungal diversity on ecosystem processes by testing whether microfungal ‘preferences’ for (i.e., host recurrence) different tropical leaf species increases the rate of decomposition. We used pairwise combinations of girradiated litter of five tree species with cultures of two dominant microfungi derived from each plant in a microcosm...

Responses of 1-year-old cottonwood to increasing soil moisture tension

Treesearch

F.T. Bonner

1967-01-01

Cottonwood cuttings planted in sandy loam and clay soils showed a sensitive control of water loss as soil moisture tension increased. Transpiration rates began decreasing at leaf water deficits of 2.5 percent in sandy loam and 4.5 percent in clay. There were no significant differences in rates per unit of leaf area or shoot dry weight between plants grown in the two...

Relationship of host recurrence in fungi to rates of tropical leaf decomposition

Treesearch

Mirna E. Santana; D. Jean Lodge; Patricia Lebow

2005-01-01

Here we explore the significance of fungal diversity on ecosystem processes by testing whether microfungal ‘preferences’ for (i.e., host recurrence) different tropical leaf species increases the rate of decomposition. We used pairwise combinations of [gamma]-irradiated litter of five tree species with cultures of two dominant microfungi derived from each plant in a...

Stimulated Leaf Dark Respiration in Tomato in an Elevated Carbon Dioxide Atmosphere

PubMed Central

Li, Xin; Zhang, Guanqun; Sun, Bo; Zhang, Shuai; Zhang, Yiqing; Liao, Yangwenke; Zhou, Yanhong; Xia, Xiaojian; Shi, Kai; Yu, Jingquan

2013-01-01

It is widely accepted that leaf dark respiration is a determining factor for the growth and maintenance of plant tissues and the carbon cycle. However, the underlying effect and mechanism of elevated CO2 concentrations ([CO2]) on dark respiration remain unclear. In this study, tomato plants grown at elevated [CO2] showed consistently higher leaf dark respiratory rate, as compared with ambient control plants. The increased respiratory capacity was driven by a greater abundance of proteins, carbohydrates, and transcripts involved in pathways of glycolysis carbohydrate metabolism, the tricarboxylic acid cycle, and mitochondrial electron transport energy metabolism. This study provides substantial evidence in support of the concept that leaf dark respiration is increased by elevated [CO2] in tomato plants and suggests that the increased availability of carbohydrates and the increased energy status are involved in the increased rate of dark respiration in response to elevated [CO2]. PMID:24305603

Insights on the development, kinetics, and variation of photoinhibition using chlorophyll fluorescence imaging of a chilled, variegated leaf.

PubMed

Hogewoning, Sander W; Harbinson, Jeremy

2007-01-01

The effect of chilling on photosystem II (PSII) efficiency was studied in the variegated leaves of Calathea makoyana, in order to gain insight into the causes of chilling-induced photoinhibition. Additionally, a relationship was revealed between (chilling) stress and variation in photosynthesis. Chilling treatments (5 degrees C and 10 degrees C) were performed for different durations (1-7 d) under a moderate irradiance (120 micromol m-2 s-1). The individual leaves were divided into a shaded zone and two illuminated, chilled zones. The leaf tip and sometimes the leaf base were not chilled. Measurements of the dark-adapted Fv/Fm were made on the different leaf zones at the end of the chilling treatment, and then for several days thereafter to monitor recovery. Chilling up to 7 d in the dark did not affect PSII efficiency and visual appearance, whereas chilling in the light caused severe photoinhibition, sometimes followed by leaf necrosis. Photoinhibition increased with the duration of the chilling period, whereas, remarkably, chilling temperature had no effect. In the unchilled leaf tip, photoinhibition also occurred, whereas in the unchilled leaf base it did not. Whatever the leaf zone, photoinhibition became permanent if the mean value dropped below 0.4, although chlorosis and necrosis were associated solely with chilled illuminated tissue. Starch accumulated in the unchilled leaf tip, in contrast to the adjacent chilled irradiated zone. This suggests that photoinhibition was due to a secondary effect in the unchilled leaf tip (sink limitation), whereas it was a direct effect of chilling and irradiance in the chilled illuminated zones. The PSII efficiency and its coefficient of variation showed a unique negative linearity across all leaf zones and different tissue types. The slope of this curve was steeper for chilled leaves than it was for healthy, non-stressed leaves, suggesting that the coefficient of variation may be an important tool for assessing stress in leaves.

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.

Leaf economics of evergreen and deciduous tree species along an elevational gradient in a subtropical mountain.

PubMed

Bai, Kundong; He, Chengxin; Wan, Xianchong; Jiang, Debing

2015-06-08

The ecophysiological mechanisms underlying the pattern of bimodal elevational distribution of evergreen tree species remain incompletely understood. Here we used leaf economics spectrum (LES) theory to explain such patterns. We measured leaf economic traits and constructed an LES for the co-existing 19 evergreen and 15 deciduous species growing in evergreen broad-leaved forest at low elevation, beech-mixed forest at middle elevation and hemlock-mixed forest at high elevation in Mao'er Mountain, Guangxi, Southern China (25°50'N, 110°49'E). Leaf economic traits presented low but significant phylogenetic signal, suggesting trait similarity between closely related species. After considering the effects of phylogenetic history, deciduous species in general showed a more acquisitive leaf strategy with a higher ratio of leaf water to dry mass, higher leaf nitrogen and phosphorous contents, higher photosynthetic and respiratory rates and greater photosynthetic nitrogen-use efficiency. In contrast, evergreen species exhibited a more conservative leaf strategy with higher leaf mass per area, greater construction costs and longer leaf life span. With the elevation-induced decreases of temperature and soil fertility, both evergreen and deciduous species showed greater resource conservation, suggesting the increasing importance of environmental filtering to community assembly with increasing elevation. We found close inter-specific correlations between leaf economic traits, suggesting that there are strong genetic constraints limiting the independent evolution of LES traits. Phylogenetic signal increased with decreasing evolutionary rate across leaf economic traits, suggesting that genetic constraints are important for the process of trait evolution. We found a significantly positive relationship between primary axis species score (PASS) distance and phylogenetic distance across species pairs and an increasing average PASS distance between evergreen and deciduous species with increasing elevation, implying that the frequency of distantly related evergreen and deciduous pairs with wide spreading of leaf economic values increases with increasing elevation. Our findings thus suggest that elevation acts as an environmental filter to both select the locally adapted evergreen and deciduous species with sufficient phylogenetic variation and regulate their distribution along the elevational gradient based on their coordinated spreading of phylogenetic divergence and leaf economic variation. Published by Oxford University Press on behalf of the Annals of Botany Company.

Mercury in leaf litter in typical suburban and urban broadleaf forests in China.

PubMed

Niu, Zhenchuan; Zhang, Xiaoshan; Wang, Zhangwei; Ci, Zhijia

2011-01-01

To study the role of leaf litter in the mercury (Hg) cycle in suburban broadleaf forests and the distribution of Hg in urban forests, we collected leaf litter and soil from suburban evergreen and deciduous broadleaf forests and from urban forests in Beijing. The Hg concentrations in leaf litter from the suburban forests varied from 8.3 to 205.0 ng/g, with an average (avg) of (49.7 +/- 36.9) ng/g. The average Hg concentration in evergreen broadleaf forest leaf litter (50.8 + 39.4) ng/g was higher than that in deciduous broadleaf forest leaf litter (25.8 +/- 10.1) ng/g. The estimated Hg fluxes of leaf litter in suburban evergreen and deciduous broadleaf forests were 179.0 and 83.7 mg/(ha x yr), respectively. The Hg concentration in organic horizons (O horizons) ((263.1 +/- 237.2) ng/g) was higher than that in eluvial horizons (A horizons) ((83.9 +/- 52.0) ng/g). These results indicated that leaf litterfall plays an important role in transporting atmospheric mercury to soil in suburban forests. For urban forests in Beijing, the Hg concentrations in leaf litter ranged from 8.8-119.0 (avg 28.1 +/- 16.6) ng/g, with higher concentrations at urban sites than at suburban sites for each tree. The Hg concentrations in surface soil in Beijing were 32.0-25300.0 ng/g and increased from suburban sites to urban sites, with the highest value from Jingshan (JS) Park at the centre of Beijing. Therefore, the distribution of Hg in Beijing urban forests appeared to be strongly influenced by anthropogenic activities.

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.

Leaf-rolling in maize crops: from leaf scoring to canopy-level measurements for phenotyping

PubMed Central

Madec, Simon; Irfan, Kamran; Lopez, Jeremy; Comar, Alexis; Hemmerlé, Matthieu; Dutartre, Dan; Praud, Sebastien; Tixier, Marie Helene

2018-01-01

Abstract Leaf rolling in maize crops is one of the main plant reactions to water stress that can be visually scored in the field. However, leaf-scoring techniques do not meet the high-throughput requirements needed by breeders for efficient phenotyping. Consequently, this study investigated the relationship between leaf-rolling scores and changes in canopy structure that can be determined by high-throughput remote-sensing techniques. Experiments were conducted in 2015 and 2016 on maize genotypes subjected to water stress. Leaf-rolling was scored visually over the whole day around the flowering stage. Concurrent digital hemispherical photographs were taken to evaluate the impact of leaf-rolling on canopy structure using the computed fraction of intercepted diffuse photosynthetically active radiation, FIPARdif. The results showed that leaves started to roll due to water stress around 09:00 h and leaf-rolling reached its maximum around 15:00 h (the photoperiod was about 05:00–20:00 h). In contrast, plants maintained under well-watered conditions did not show any significant rolling during the same day. A canopy-level index of rolling (CLIR) is proposed to quantify the diurnal changes in canopy structure induced by leaf-rolling. It normalizes for the differences in FIPARdif between genotypes observed in the early morning when leaves are unrolled, as well as for yearly effects linked to environmental conditions. Leaf-level rolling score was very strongly correlated with changes in canopy structure as described by the CLIR (r2=0.86, n=370). The daily time course of rolling was characterized using the amplitude of variation, and the rate and the timing of development computed at both the leaf and canopy levels. Results obtained from eight genotypes common between the two years of experiments showed that the amplitude of variation of the CLIR was the more repeatable trait (Spearman coefficient ρ=0.62) as compared to the rate (ρ=0.29) and the timing of development (ρ=0.33). The potential of these findings for the development of a high-throughput method for determining leaf-rolling based on aerial drone observations are considered. PMID:29617837

Leaf angle, tree species, and the functioning of broadleaf deciduous forest ecosystems

NASA Astrophysics Data System (ADS)

McNeil, B. E.; Brzostek, E. R.; Fahey, R. T.; King, C. J.; Flamenco, E. A.; Rescorl, S.; Erazo, D.; Heimerl, T.

2016-12-01

The effects of temperate forests on the global cycles of carbon, water, and energy depends strongly on how individual tree species adjust to the novel environmental conditions of the Anthropocene. Here, we seek to identify and understand ecological variability in one important component of tree canopies, the inclination angles of leaves. Leaf angle has important effects on forest albedo, photosynthesis, and evapotranspiration, but there is relatively little data to constrain the many models that include (or perhaps should include) this essential aspect of canopy architecture. We employ a relatively new technique for using an electronic protractor to measure leaf angles from leveled digital photographs. From a suite of observation platforms (e.g. UAVs, eddy flux towers, old fire towers) in Connecticut, Indiana, Maryland, Michigan, Pennsylvania, and West Virginia, USA, we have measured leaf angles periodically throughout the 2014, 2015, and 2016 growing seasons. Based on over 25,000 measurements taken from 15 tree species, we find highly significant differences in mean leaf angle by canopy position, tree species, location, and observation date. In addition to replicating findings where upper-canopy sun leaves are more vertical than lower-canopy shade leaves, our analysis on sun leaves also finds other ecologically meaningful differences. For instance, we find that the mesic, shade tolerant sugar maple had significantly more horizontal leaf angles than drought-resistant species such as white oak. Species also appear to have unique patterns of leaf angle phenology, with most species tending toward more vertical leaf angles during droughty conditions later in the year. We discuss these empirical results in light of an emerging theoretical framework that positions leaf angle as a functional trait. Like leaf traits such as %N or SLA, we suggest that leaf angle is an essential part of the adaptive resource strategy of each tree species. Finally, by linking our leaf angle data to new observations of spatial and temporal variations in near infrared reflectance measured from UAV, airborne, and satellite sensors, we highlight how species-specific patterns of leaf angle phenology could provide a new mechanism to better constrain model predictions of energy, water, and carbon fluxes from temperate forests.

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.

Growth and stoichiometry of a common aquatic detritivore respond to changes in resource stoichiometry.

PubMed

Fuller, Chris L; Evans-White, Michelle A; Entrekin, Sally A

2015-03-01

Consumer growth determines the quantity of nutrients transferred through food webs. The extent to which leaf composition and consumer physiology interact to constrain consumer production is not well understood. For example, detritivore growth, and thus material transfer, could change with detrital elemental composition. Detrital type and associated microbial biofilms can mediate the amount and rate of detritus consumed and used towards growth. Detritivore body stoichiometry or the threshold elemental ratio, the food ratio resulting in optimal growth, may predict taxon-specific growth response to stoichiometrically-altered detritus. Empirical measures of detritivore growth responses across a range of detrital stoichiometry are rare. We fed a common detritivore, Tipula abdominalis, maple or oak leaves that spanned a gradient of carbon:phosphorus (C:P) to examine how leaf identity and C:P interact to influence growth, consumption, assimilation efficiencies, and post-assimilatory processes. Tipula abdominalis growth and consumption varied with leaf type and stoichiometry. Individuals fed oak grew faster and ate more compared to individuals fed maple. Individuals fed maple grew faster and ate more as leaf C:P decreased. All individuals lost most of the material they assimilated through respiration and excretion regardless of leaf type or leaf stoichiometry. Consumption and growth rates of T. abdominalis increased with maple nutrient enrichment, but not oak, indicating leaf-specific nutrient enrichment affected leaf palatability. Slightly non-homeostatic T. abdominalis C:P was maintained by varied consumption, carbon assimilation, and P excretion. Our study underlines the importance of how detritivore consumption and post-assimilatory processing could influence whole-stream material storage and nutrient cycling in detrital-based ecosystems.

Effects of the fungal endophyte Acremonium coenophialum on nitrogen accumulation and metabolism in tall fescue

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

Lyons, P.C.; Evans, J.J.; Bacon, C.W.

Infection by the fungal endophyte Acremonium coenophialum affected the accumulation of inorganic and organic N in leaf blades and leaf sheaths of KY31 tall fescue (Festuca arundinacea Schreb.) grown under greenhouse conditions. Total soluble amino acid concentrations were increased in either the blade or sheath of the leaf from infected plants. A number of amino acids were significantly increased in the sheath, but only asparagine increased in the blade. Infection resulted in higher sheath NH{sub 4}{sup +} concentrations, whereas NO{sub 3}{sup {minus}} concentrations decreased in both leaf parts. The effects on amino acid, NO{sub 3}{sup {minus}}, and NH{sub 4}{sup +}more » concentrations were dependent upon the level of N fertilization and were usually apparent only at the high rate (10 millimolar) of application. Administration of {sup 14}CO{sub 2} to the leaf blades increased the accumulation of {sup 14}C in their amino acid fraction but not in the sheaths of infected plants. This may indicate that infection increased amino acid synthesis in the blade but that translocation to the sheath, which is the site of fungal colonization, was not affected. Glutamine synthetase activity was greater in leaf blades of infected plants at high and low N rates of fertilization, but nitrate reductase activity was not affected in either part of the leaf. Increased activities of glutamine synthetase together with the other observed changes in N accumulation and metabolism in endophyte-infected tall fescue suggest that NH{sub 4}{sup +} reassimilation could also be affected in the leaf blade.« less

Identification of Candidate Genes Associated with Leaf Senescence in Cultivated Sunflower (Helianthus annuus L.)

PubMed Central

Moschen, Sebastian; Bengoa Luoni, Sofia; Paniego, Norma B.; Hopp, H. Esteban; Dosio, Guillermo A. A.

2014-01-01

Cultivated sunflower (Helianthus annuus L.), an important source of edible vegetable oil, shows rapid onset of senescence, which limits production by reducing photosynthetic capacity under specific growing conditions. Carbon for grain filling depends strongly on light interception by green leaf area, which diminishes during grain filling due to leaf senescence. Transcription factors (TFs) regulate the progression of leaf senescence in plants and have been well explored in model systems, but information for many agronomic crops remains limited. Here, we characterize the expression profiles of a set of putative senescence associated genes (SAGs) identified by a candidate gene approach and sunflower microarray expression studies. We examined a time course of sunflower leaves undergoing natural senescence and used quantitative PCR (qPCR) to measure the expression of 11 candidate genes representing the NAC, WRKY, MYB and NF-Y TF families. In addition, we measured physiological parameters such as chlorophyll, total soluble sugars and nitrogen content. The expression of Ha-NAC01, Ha-NAC03, Ha-NAC04, Ha-NAC05 and Ha-MYB01 TFs increased before the remobilization rate increased and therefore, before the appearance of the first physiological symptoms of senescence, whereas Ha-NAC02 expression decreased. In addition, we also examined the trifurcate feed-forward pathway (involving ORE1, miR164, and ETHYLENE INSENSITIVE 2) previously reported for Arabidopsis. We measured transcription of Ha-NAC01 (the sunflower homolog of ORE1) and Ha-EIN2, along with the levels of miR164, in two leaves from different stem positions, and identified differences in transcription between basal and upper leaves. Interestingly, Ha-NAC01 and Ha-EIN2 transcription profiles showed an earlier up-regulation in upper leaves of plants close to maturity, compared with basal leaves of plants at pre-anthesis stages. These results suggest that the H. annuus TFs characterized in this work could play important roles as potential triggers of leaf senescence and thus can be considered putative candidate genes for senescence in sunflower. PMID:25110882

Identification of candidate genes associated with leaf senescence in cultivated sunflower (Helianthus annuus L.).

PubMed

Moschen, Sebastian; Bengoa Luoni, Sofia; Paniego, Norma B; Hopp, H Esteban; Dosio, Guillermo A A; Fernandez, Paula; Heinz, Ruth A

2014-01-01

Cultivated sunflower (Helianthus annuus L.), an important source of edible vegetable oil, shows rapid onset of senescence, which limits production by reducing photosynthetic capacity under specific growing conditions. Carbon for grain filling depends strongly on light interception by green leaf area, which diminishes during grain filling due to leaf senescence. Transcription factors (TFs) regulate the progression of leaf senescence in plants and have been well explored in model systems, but information for many agronomic crops remains limited. Here, we characterize the expression profiles of a set of putative senescence associated genes (SAGs) identified by a candidate gene approach and sunflower microarray expression studies. We examined a time course of sunflower leaves undergoing natural senescence and used quantitative PCR (qPCR) to measure the expression of 11 candidate genes representing the NAC, WRKY, MYB and NF-Y TF families. In addition, we measured physiological parameters such as chlorophyll, total soluble sugars and nitrogen content. The expression of Ha-NAC01, Ha-NAC03, Ha-NAC04, Ha-NAC05 and Ha-MYB01 TFs increased before the remobilization rate increased and therefore, before the appearance of the first physiological symptoms of senescence, whereas Ha-NAC02 expression decreased. In addition, we also examined the trifurcate feed-forward pathway (involving ORE1, miR164, and ethylene insensitive 2) previously reported for Arabidopsis. We measured transcription of Ha-NAC01 (the sunflower homolog of ORE1) and Ha-EIN2, along with the levels of miR164, in two leaves from different stem positions, and identified differences in transcription between basal and upper leaves. Interestingly, Ha-NAC01 and Ha-EIN2 transcription profiles showed an earlier up-regulation in upper leaves of plants close to maturity, compared with basal leaves of plants at pre-anthesis stages. These results suggest that the H. annuus TFs characterized in this work could play important roles as potential triggers of leaf senescence and thus can be considered putative candidate genes for senescence in sunflower.

The Success of the Horse-Chestnut Leaf-Miner, Cameraria ohridella, in the UK Revealed with Hypothesis-Led Citizen Science

PubMed Central

Pocock, Michael J. O.; Evans, Darren M.

2014-01-01

Citizen science is an increasingly popular way of undertaking research and simultaneously engaging people with science. However, most emphasis of citizen science in environmental science is on long-term monitoring. Here, we demonstrate the opportunities provided by short-term hypothesis-led citizen science. In 2010, we ran the ‘Conker Tree Science’ project, in which over 3500 people in Great Britain provided data at a national scale of an insect (horse-chestnut leaf-mining moth, Cameraria ohridella) undergoing rapid range-expansion. We addressed two hypotheses, and found that (1) the levels of damage caused to leaves of the horse-chestnut tree, Aesculus hippocastanum, and (2) the level of attack by parasitoids of C. ohridella larvae were both greatest where C. ohridella had been present the longest. Specifically there was a rapid rise in leaf damage during the first three years that C. ohridella was present and only a slight rise thereafter, while estimated rates of parasitism (an index of true rates of parasitism) increased from 1.6 to 5.9% when the time C. ohridella had been present in a location increased from 3 to 6 years. We suggest that this increase is due to recruitment of native generalist parasitoids, rather than the adaptation or host-tracking of more specialized parasitoids, as appears to have occurred elsewhere in Europe. Most data collected by participants were accurate, but the counts of parasitoids from participants showed lower concordance with the counts from experts. We statistically modeled this bias and propagated this through our analyses. Bias-corrected estimates of parasitism were lower than those from the raw data, but the trends were similar in magnitude and significance. With appropriate checks for data quality, and statistically correcting for biases where necessary, hypothesis-led citizen science is a potentially powerful tool for carrying out scientific research across large spatial scales while simultaneously engaging many people with science. PMID:24465973

The success of the horse-chestnut leaf-miner, Cameraria ohridella, in the UK revealed with hypothesis-led citizen science.

PubMed

Pocock, Michael J O; Evans, Darren M

2014-01-01

Citizen science is an increasingly popular way of undertaking research and simultaneously engaging people with science. However, most emphasis of citizen science in environmental science is on long-term monitoring. Here, we demonstrate the opportunities provided by short-term hypothesis-led citizen science. In 2010, we ran the 'Conker Tree Science' project, in which over 3500 people in Great Britain provided data at a national scale of an insect (horse-chestnut leaf-mining moth, Cameraria ohridella) undergoing rapid range-expansion. We addressed two hypotheses, and found that (1) the levels of damage caused to leaves of the horse-chestnut tree, Aesculus hippocastanum, and (2) the level of attack by parasitoids of C. ohridella larvae were both greatest where C. ohridella had been present the longest. Specifically there was a rapid rise in leaf damage during the first three years that C. ohridella was present and only a slight rise thereafter, while estimated rates of parasitism (an index of true rates of parasitism) increased from 1.6 to 5.9% when the time C. ohridella had been present in a location increased from 3 to 6 years. We suggest that this increase is due to recruitment of native generalist parasitoids, rather than the adaptation or host-tracking of more specialized parasitoids, as appears to have occurred elsewhere in Europe. Most data collected by participants were accurate, but the counts of parasitoids from participants showed lower concordance with the counts from experts. We statistically modeled this bias and propagated this through our analyses. Bias-corrected estimates of parasitism were lower than those from the raw data, but the trends were similar in magnitude and significance. With appropriate checks for data quality, and statistically correcting for biases where necessary, hypothesis-led citizen science is a potentially powerful tool for carrying out scientific research across large spatial scales while simultaneously engaging many people with science.

Global and local disturbances interact to modify seagrass palatability.

PubMed

Jiménez-Ramos, Rocío; Egea, Luis G; Ortega, María J; Hernández, Ignacio; Vergara, Juan J; Brun, Fernando G

2017-01-01

Global change, such as warming and ocean acidification, and local anthropogenic disturbances, such as eutrophication, can have profound impacts on marine organisms. However, we are far from being able to predict the outcome of multiple interacting disturbances on seagrass communities. Herbivores are key in determining plant community structure and the transfer of energy up the food web. Global and local disturbances may alter the ecological role of herbivory by modifying leaf palatability (i.e. leaf traits) and consequently, the feeding patterns of herbivores. This study evaluates the main and interactive effects of factors related to global change (i.e. elevated temperature, lower pH levels and associated ocean acidification) and local disturbance (i.e. eutrophication through ammonium enrichment) on a broad spectrum of leaf traits using the temperate seagrass Cymodocea nodosa, including structural, nutritional, biomechanical and chemical traits. The effect of these traits on the consumption rates of the generalist herbivore Paracentrotus lividus (purple sea urchin) is evaluated. The three disturbances of warming, low pH level and eutrophication, alone and in combination, increased the consumption rate of seagrass by modifying all leaf traits. Leaf nutritional quality, measured as nitrogen content, was positively correlated to consumption rate. In contrast, a negative correlation was found between feeding decisions by sea urchins and structural, biomechanical and chemical leaf traits. In addition, a notable accomplishment of this work is the identification of phenolic compounds not previously reported for C. nodosa. Our results suggest that global and local disturbances may trigger a major shift in the herbivory of seagrass communities, with important implications for the resilience of seagrass ecosystems.

Variation in Leaf Respiration Rates at Night Correlates with Carbohydrate and Amino Acid Supply1[OPEN

PubMed Central

Lee, Chun Pong; Cheng, Riyan

2017-01-01

Plant respiration can theoretically be fueled by and dependent upon an array of central metabolism components; however, which ones are responsible for the quantitative variation found in respiratory rates is unknown. Here, large-scale screens revealed 2-fold variation in nighttime leaf respiration rate (RN) among mature leaves from an Arabidopsis (Arabidopsis thaliana) natural accession collection grown under common favorable conditions. RN variation was mostly maintained in the absence of genetic variation, which emphasized the low heritability of RN and its plasticity toward relatively small environmental differences within the sampling regime. To pursue metabolic explanations for leaf RN variation, parallel metabolite level profiling and assays of total protein and starch were performed. Within an accession, RN correlated strongly with stored carbon substrates, including starch and dicarboxylic acids, as well as sucrose, major amino acids, shikimate, and salicylic acid. Among different accessions, metabolite-RN correlations were maintained with protein, sucrose, and major amino acids but not stored carbon substrates. A complementary screen of the effect of exogenous metabolites and effectors on leaf RN revealed that (1) RN is stimulated by the uncoupler FCCP and high levels of substrates, demonstrating that both adenylate turnover and substrate supply can limit leaf RN, and (2) inorganic nitrogen did not stimulate RN, consistent with limited nighttime nitrogen assimilation. Simultaneous measurements of RN and protein synthesis revealed that these processes were largely uncorrelated in mature leaves. These results indicate that differences in preceding daytime metabolic activities are the major source of variation in mature leaf RN under favorable controlled conditions. PMID:28615345

Growth and physiological responses of isohydric and anisohydric poplars to drought

DOE PAGES

Attia, Ziv; Domec, Jean-Christophe; Oren, Ram; ...

2015-05-07

Understanding how different plants prioritize carbon gain and drought vulnerability under a variable water supply is important for predicting which trees will maximize woody biomass production under different environmental conditions. Here, Populus balsamifera (BS, isohydric genotype), P. simonii (SI, previously uncharacterized stomatal behaviour), and their cross, P. balsamifera x simonii (BSxSI, anisohydric genotype) were studied to assess the physiological basis for biomass accumulation and water-use efficiency across a range of water availabilities. Under ample water, whole plant stomatal conductance (g s), transpiration (E), and growth rates were higher in anisohydric genotypes (SI and BSxSI) than in isohydric poplars (BS). Undermore » drought, all genotypes regulated the leaf to stem water potential gradient via changes in gs, synchronizing leaf hydraulic conductance (K leaf) and E: isohydric plants reduced K leaf, g s, and E, whereas anisohydric genotypes maintained high K leaf and E, which reduced both leaf and stem water potentials. Nevertheless, SI poplars reduced their plant hydraulic conductance (K plant) during water stress and, unlike, BSxSI plants, recovered rapidly from drought. Low gs of the isohydric BS under drought reduced CO 2 assimilation rates and biomass potential under moderate water stress. While anisohydric genotypes had the fastest growth under ample water and higher photosynthetic rates under increasing water stress, isohydric poplars had higher water-use efficiency. Overall, the results indicate three strategies for how closely related biomass species deal with water stress: survival-isohydric (BS), sensitive-anisohydric (BSxSI), and resilience-anisohydric (SI). Lastly, we discuss implications for woody biomass growth, water-use efficiency, and survival under variable environmental conditions.« less

Leaf area index, leaf mass density, and allometric relationships derived from harvest of blue oaks in a California oak savanna

Treesearch

John F. Karlik; Alistair H. McKay

2002-01-01

Given the key role played by biogenic volatile organic compounds (BVOC) in tropospheric chemistry and regional air quality, it is critical to generate accurate BVOC emission inventories. Because oak species found in California often have high BVOC emission rates, and are often of large stature with corresponding large leaf masses, oaks may be the most important genus...

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...

Expression of Arabidopsis SHN1 in Indian Mulberry (Morus indica L.) Increases Leaf Surface Wax Content and Reduces Post-harvest Water Loss

PubMed Central

Sajeevan, R. S.; Nataraja, Karaba N.; Shivashankara, K. S.; Pallavi, N.; Gurumurthy, D. S.; Shivanna, M. B.

2017-01-01

Mulberry (Morus species) leaf is the sole food for monophagous silkworms, Bombyx mori L. Abiotic stresses such as drought, salinity, and high temperature, significantly decrease mulberry productivity and post-harvest water loss from leaves influence silkworm growth and cocoon yield. Leaf surface properties regulate direct water loss through the cuticular layer. Leaf surface waxes, contribute for cuticular resistance and protect mesophyll cells from desiccation. In this study we attempted to overexpress AtSHN1, a transcription factor associated with epicuticular wax biosynthesis to increase leaf surface wax load in mulberry. Agrobacterium mediated in vitro transformation was carried out using hypocotyl and cotyledonary explants of Indian mulberry (cv. M5). Mulberry transgenic plants expressing AtSHN1 displayed dark green shiny appearance with increased leaf surface wax content. Scanning electron microscopy (SEM) and gas chromatograph–mass spectrometry (GC-MS) analysis showed change in pattern of surface wax deposition and significant change in wax composition in AtSHN1 overexpressors. Increased wax content altered leaf surface properties as there was significant difference in water droplet contact angle and diameter between transgenic and wild type plants. The transgenic plants showed significant improvement in leaf moisture retention capacity even 5 h after harvest and there was slow degradation of total buffer soluble protein in detached leaves compared to wild type. Silkworm bioassay did not indicate any undesirable effects on larval growth and cocoon yield. This study demonstrated that expression of AtSHN1, can increase surface wax load and reduce the post-harvest water loss in mulberry. PMID:28421085

Genome-Wide Association Mapping of Leaf Rust Response in a Durum Wheat Worldwide Germplasm Collection.

PubMed

Aoun, Meriem; Breiland, Matthew; Kathryn Turner, M; Loladze, Alexander; Chao, Shiaoman; Xu, Steven S; Ammar, Karim; Anderson, James A; Kolmer, James A; Acevedo, Maricelis

2016-11-01

Leaf rust (caused by Erikss. []) is increasingly impacting durum wheat ( L. var. ) production with the recent appearance of races with virulence to widely grown cultivars in many durum producing areas worldwide. A highly virulent race on durum wheat was recently detected in Kansas. This race may spread to the northern Great Plains, where most of the US durum wheat is produced. The objective of this study was to identify sources of resistance to several races from the United States and Mexico at seedling stage in the greenhouse and at adult stage in field experiments. Genome-wide association study (GWAS) was used to identify single-nucleotide polymorphism (SNP) markers associated with leaf rust response in a worldwide durum wheat collection of 496 accessions. Thirteen accessions were resistant across all experiments. Association mapping revealed 88 significant SNPs associated with leaf rust response. Of these, 33 SNPs were located on chromosomes 2A and 2B, and 55 SNPs were distributed across all other chromosomes except for 1B and 7B. Twenty markers were associated with leaf rust response at seedling stage, while 68 markers were associated with leaf rust response at adult plant stage. The current study identified a total of 14 previously uncharacterized loci associated with leaf rust response in durum wheat. The discovery of these loci through association mapping (AM) is a significant step in identifying useful sources of resistance that can be used to broaden the relatively narrow leaf rust resistance spectrum in durum wheat germplasm. Copyright © 2016 Crop Science Society of America.

Effects of ammonium sulfate aerosols on vegetation—II. Mode of entry and responses of vegetation

NASA Astrophysics Data System (ADS)

Gmur, Nicholas F.; Evans, Lance S.; Cunningham, Elizabeth A.

These experiments were designed to provide information on the rates of aerosol deposition, mode of entry, and effects of deposition of submicrometer ammonium sulfate aerosols on foliage of Phaseolus vulgaris L. A deposition velocity of 3.2 × 10 3cms-1 was constant during 3-week exposures of plants to aerosol concentrations of 26mg m -3 (i.e. about two orders of magnitude above ambient episode concentrations). Mean deposition rate on foliage was 4.1 × 10 -11 μg cm -2s -1. Visible injury symptoms included leaf chlorosis, necrosis and loss of turgor. Chlorosis was most frequent near leaf margins causing epinasty and near major veins. Internal injury occurred initially in spongy mesophyll cells. Eventually abaxial epidermal and palisade parenchyma cells were injured. These results suggest that submicrometer aerosols enter abaxial stomata and affect more internal cells before affecting leaf surface cells. Exposure to aerosols decreased both abaxial and adaxial leaf resistances markedly. Although visible injury to foliage occurred, no changes in dry mass of roots and shoots or leaf area occurred. These results suggest that for the plant developmental stage studied, while leaf resistances decreased and cellular injury occurred in foliage, these factors were not significantly related to plant growth and development.

Photosynthesis and canopy characteristics in genetically defined families of silver birch (Betula pendula).

PubMed

Wang, T; Tigerstedt, P M; Viherä-Aarnio, A

1995-10-01

Net photosynthetic rates (A) of leaves in upper and lower crown layers (A(upper) and A(lower)), leaf area index (LAI), mean tilt angle (MTA), several leaf characteristics, and volume growth were observed in fast- and slow-growing families of a 14-year-old full-sib and half-sib family progeny test of Betula pendula Roth. Each measure of net photosynthetic rate was calculated after correcting measured net photosynthesis for the effects of environmental variables. The differences in A(upper) and LAI among families were significant. The proportions of the total variance assigned to family for A(upper), A(lower) and LAI were 33.64, 28.93 and 54.99%, respectively. The mean A(upper) and LAI of the fast-growing families were significantly higher than those of the slow-growing families, whereas the mean A(lower) of the fast-growing families was significantly lower than that of the slow-growing families. There were also significant differences among families in leaf size, leaf shape, and the ratios leaf fresh weight/area and leaf dry weight/area. Between 27.55 and 54.55% of the total variance in these characteristics could be assigned to the family effect. Volume growth was positively correlated with A(upper) and LAI, but it was most strongly correlated with A(upper) x LAI.

Divergence in Patterns of Leaf Growth Polarity Is Associated with the Expression Divergence of miR396.

PubMed

Das Gupta, Mainak; Nath, Utpal

2015-10-01

Lateral appendages often show allometric growth with a specific growth polarity along the proximo-distal axis. Studies on leaf growth in model plants have identified a basipetal growth direction with the highest growth rate at the proximal end and progressively lower rates toward the distal end. Although the molecular mechanisms governing such a growth pattern have been studied recently, variation in leaf growth polarity and, therefore, its evolutionary origin remain unknown. By surveying 75 eudicot species, here we report that leaf growth polarity is divergent. Leaf growth in the proximo-distal axis is polar, with more growth arising from either the proximal or the distal end; dispersed with no apparent polarity; or bidirectional, with more growth contributed by the central region and less growth at either end. We further demonstrate that the expression gradient of the miR396-GROWTH-REGULATING FACTOR module strongly correlates with the polarity of leaf growth. Altering the endogenous pattern of miR396 expression in transgenic Arabidopsis thaliana leaves only partially modified the spatial pattern of cell expansion, suggesting that the diverse growth polarities might have evolved via concerted changes in multiple gene regulatory networks. © 2015 American Society of Plant Biologists. All rights reserved.

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.

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.

Movement of Abscisic Acid into the Apoplast in Response to Water Stress in Xanthium strumarium L. 1

PubMed Central

Cornish, Katrina; Zeevaart, Jan A. D.

1985-01-01

The effect of water stress on the redistribution of abcisic acid (ABA) in mature leaves of Xanthium strumarium L. was investigated using a pressure dehydration technique. In both turgid and stressed leaves, the ABA in the xylem exudate, the `apoplastic' ABA, increased before `bulk leaf' stress-induced ABA accumulation began. In the initially turgid leaves, the ABA level remained constant in both the apoplast and the leaf as a whole until wilting symptoms appeared. Following turgor loss, sufficient quantities of ABA moved into the apoplast to stimulate stomatal closure. Thus, the initial increase of apoplastic ABA may be relevant to the rapid stomatal closure seen in stressed leaves before their bulk leaf ABA levels rise. Following recovery from water stress, elevated levels of ABA remained in the apoplast after the bulk leaf contents had returned to their prestress values. This apoplastic ABA may retard stomatal reopening during the initial recovery period. PMID:16664294

Enhanced leaf photosynthesis as a target to increase grain yield: insights from transgenic rice lines with variable Rieske FeS protein content in the cytochrome b6 /f complex.

PubMed

Yamori, Wataru; Kondo, Eri; Sugiura, Daisuke; Terashima, Ichiro; Suzuki, Yuji; Makino, Amane

2016-01-01

Although photosynthesis is the most important source for biomass and grain yield, a lack of correlation between photosynthesis and plant yield among different genotypes of various crop species has been frequently observed. Such observations contribute to the ongoing debate whether enhancing leaf photosynthesis can improve yield potential. Here, transgenic rice plants that contain variable amounts of the Rieske FeS protein in the cytochrome (cyt) b6 /f complex between 10 and 100% of wild-type levels have been used to investigate the effect of reductions of these proteins on photosynthesis, plant growth and yield. Reductions of the cyt b6 /f complex did not affect the electron transport rates through photosystem I but decreased electron transport rates through photosystem II, leading to concomitant decreases in CO2 assimilation rates. There was a strong control of plant growth and grain yield by the rate of leaf photosynthesis, leading to the conclusion that enhancing photosynthesis at the single-leaf level would be a useful target for improving crop productivity and yield both via conventional breeding and biotechnology. The data here also suggest that changing photosynthetic electron transport rates via manipulation of the cyt b6 /f complex could be a potential target for enhancing photosynthetic capacity in higher plants. © 2015 John Wiley & Sons Ltd.

First Report of Leaf Spot Caused by Alternaria tenuissima on Black Chokeberry (Aronia melanocarpa) in Korea.

PubMed

Wee, Jung-In; Park, Jong-Han; Back, Chang-Gi; You, Young-Hyun; Chang, Taehyun

2016-09-01

In July 2015, diseased leaves of black chokeberry ( Aronia melanocarpa ) were observed in Danyang and Gochang, Korea. The symptoms appeared as circular or irregular brown leaf spots, from which Alternaria tenuissima was isolated. The isolates were cultured on potato dextrose agar, and their morphological characteristics were observed under a light microscope. The colonies were whitish to ash colored. The pathogenicity test on healthy black chokeberry leaves produced circular brown spots, in line with the original symptoms. Molecular analyses of the ITS, GPD, RPB2, and TEF genes were conducted to confirm the identity of the pathogen. The phylogeny of the multi-gene sequences indicated that the causal agent was A. tenuissima . This study is the first report of A. tenuissima leaf spot on black chokeberry ( A. melanocarpa ).

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.

Trends in leaf photosynthesis in historical rice varieties developed in the Philippines since 1966.

PubMed

Hubbart, S; Peng, S; Horton, P; Chen, Y; Murchie, E H

2007-01-01

Crop improvement in terms of yield is rarely linked to leaf photosynthesis. However, in certain crop plants such as rice, it is predicted that an increase in photosynthetic rate will be required to support future grain yield potential. In order to understand the relationships between yield improvement and leaf photosynthesis, controlled environment conditions were used to grow 10 varieties which were released from the International Rice Research Institute (IRRI) between 1966 and 1995 and one newly developed line. Two growth light intensities were used: high light (1500 micromol m(-2) s(-1)) and low light (300 micromol m(-2) s(-1)). Gas exchange, leaf protein, chlorophyll, and leaf morphology were measured in the ninth leaf on the main stem. A high level of variation was observed among high light-grown plants for light-saturated photosynthetic rate per unit leaf area (P(max)), stomatal conductance (g), content of ribulose bisphosphate carboxylase-oxygenase (Rubisco), and total leaf protein content. Notably, between 1966 and 1980 there was a decline in P(max), g, leaf protein, chlorophyll, and Rubisco content. Values recovered in those varieties released after 1980. This striking trend coincides with a previous published observation that grain yield in IRRI varieties released prior to 1980 correlated with harvest index whereas that for those released after 1980 correlated with biomass. P(max) showed significant correlations with both g and Rubisco content. Large differences were observed between high light- and low light-grown plants (photoacclimation). The photoacclimation 'range' for P(max) correlated with P(max) in high light-grown plants. It is concluded that (i) leaf photosynthesis may be systematically affected by breeding strategy; (ii) P(max) is a useful target for yield improvements where yield is limited by biomass production rather than partitioning; and (iii) the capacity for photoacclimation is related to high P(max) values.

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.

Biodiversity and ecosystem function in species-poor communities: community structure and leaf litter breakdown in a Pacific island stream

Treesearch

Jonathan P. Benstead; James G. March; Catherine M. Pringle; Katherine C. Ewel; John W. Short

2009-01-01

Pacific island stream communities are species-poor because of the effects of extreme geographic isolation on colonization rates of taxa common to continental regions. The effects of such low species richness on stream ecosystem function are not well understood. Here, we provide data on community structure and leaf litter breakdown rate in a virtually pristine stream on...

Effects of CO2 Concentration on Leaf Photosynthesis and Stomatal Conductance of Potatoes Grown Under Different Irradiance Levels and Photoperiods

NASA Technical Reports Server (NTRS)

Wheeler, R. M.; Fitzpatrick, A. H.; Tibbitts, T. W.

2012-01-01

Potato (Solanum tuberosum L.) cvs. Russet Burbank, Denali, and Norland, were grown in environmental rooms controlled at approx 350 micro mol/mol (ambient during years 1987/1988) and 1000 micro mol/mol (enriched) CO2 concentrations. Plants and electric lamps were arranged to provide two irradiance zones, 400 and 800 micro mol/mol/square m/S PPF and studies were repeated using two photoperiods (12-h light / 12-h dark and continuous light). Leaf photosynthetic rates and leaf stomatal conductance were measured using fully expanded, upper canopy leaves at weekly intervals throughout growth (21 through 84 days after transplanting). Increasing the CO2 from approx 350 to 1000 micro mol/mol under the 12-h photoperiod increased leaf photosynthetic rates by 39% at 400 micro mol/mol/square m/S PPF and 27% at 800 micro mol/mol/square m/S PPF. Increasing the CO2 from approx 350 to 1000 micro mol/mol under continuous light decreased leaf photosynthetic rates by 7% at 400 micro mol/mol/square m/S PPF and 13% at 800 micro mol/mol/square m/S PPF. Increasing the CO2 from approx 350 to 1000 micro mol/mol under the 12-h photoperiod plants decreased stomatal conductance by an average of 26% at 400 micro mol/mol/square m/S PPF and 42% at 800 micro mol/mol/square m/S PPF. Under continuous light, CO2 enrichment resulted in a small increase (2%) of stomatal conductance at 400 micro mol/mol/square m/S PPF, and a small decrease (3%) at 800 micro mol/mol/square m/S PPF. Results indicate that CO2 enrichment under the 12-h photoperiod showed the expected increase in photosynthesis and decrease in stomatal conductance for a C3 species like potato, but the decreases in leaf photosynthetic rates and minimal effect on conductance from CO2 enrichment under continuous light were not expected. The plant leaves under continuous light showed more chlorosis and some rusty flecking versus plants under the 12-h photoperiod, suggesting the continuous light was more stressful on the plants. The increased rates of leaf photosynthesis with increased CO2 concentration paralleled trends in biomass production (published previously) but were not proportional to the biomass yields.

Morphological and biochemical changes in Azadirachta indica from coal combustion fly ash dumping site from a thermal power plant in Delhi, India.

PubMed

Qadir, Sami Ullah; Raja, Vaseem; Siddiqui, Weqar A

2016-07-01

The foliar and biochemical traits of Azadirachta indica A. Juss from fly ash (FA) dumping site in Badarpur thermal power plant (BTPP) New Delhi, India was studied. Three different experimental sites were selected at different distances from the thermal power plant. Ambient suspended particulate matter (SPM) and plant responses such as leaf pigments (chlorophyll a, chlorophyll b, and carotenoids), total chlorophyll, net photosynthetic rate, stomatal index (SI), stomatal conductance (SC), intercellular carbon dioxide concentration [CO2]i, net photosynthetic rate (NPR), nitrogen, nitrate, nitrate reductase activity, proline, protein, reducing sugar and sulphur content were measured. Considerable reduction in pigments (chlorophyll a, chlorophyll b and carotenoids), and total chlorophyll was observed at fly ash dumping site. Fly ash stress revealed the inhibitory effect on Nitrate reductase activity (NRA), Nitrate, soluble protein, and reducing sugar content, whereas stimulatory effect was found for the stomatal index, nitrogen, proline, antioxidants and sulphur content in the leaves. Under fly ash stress, stomatal conductance was low, leading to declining in photosynthetic rate and increase in the internal CO2 concentration of leaf. Single leaf area (SLA), leaf length and leaf width also showed a declining trend from control to the polluted site. Antioxidant enzymes increased in leaves reflecting stress and extenuation of reactive oxygen species (ROS). Copyright © 2016 Elsevier Inc. All rights reserved.

[Effects of soil moisture content and light intensity on the plant growth and leaf physiological characteristics of squash].

PubMed

Du, She-ni; Bai, Gang-shuan; Liang, Yin-li

2011-04-01

A pot experiment with artificial shading was conducted to study the effects of soil moisture content and light intensity on the plant growth and leaf physiological characteristics of squash variety "Jingyingyihao". Under all test soil moisture conditions, 30% shading promoted the growth of "Jingyingyihao", with the highest yield at 70% - 80% soil relative moisture contents. 70% shading inhibited plant growth severely, only flowering and not bearing fruits, no economic yield produced. In all treatments, there was a similar water consumption trend, i. e., both the daily and the total water consumption decreased with increasing shading and decreasing soil moisture content. Among all treatments, 30% shading and 70% - 80% soil relative moisture contents had the highest water use efficiency (2.36 kg mm(-1) hm(-2)) and water output rate (1.57 kg mm(-1) hm(-2)). The net photosynthetic rate, transpiration rate, stomatal conductance, and chlorophyll content of squash leaves decreased with increasing shading, whereas the intercellular CO2 concentration was in adverse. The leaf protective enzyme activity and proline content decreased with increasing shading, and the leaf MAD content decreased in the order of 70% shading, natural radiation, and 30% shading. Under the three light intensities, the change characteristics of squash leaf photosynthesis, protective enzyme activity, and proline and MAD contents differed with the increase of soil relative moisture content.

Adsorption of Pb(II) and Cu(II) by Ginkgo-Leaf-Derived Biochar Produced under Various Carbonization Temperatures and Times.

PubMed

Lee, Myoung-Eun; Park, Jin Hee; Chung, Jae Woo

2017-12-07

Ginkgo trees are common street trees in Korea, and the large amounts of leaves that fall onto the streets annually need to be cleaned and treated. Therefore, fallen gingko leaves have been used as a raw material to produce biochar for the removal of heavy metals from solutions. Gingko-leaf-derived biochar was produced under various carbonization temperatures and times. This study evaluated the physicochemical properties and adsorption characteristics of gingko-leaf-derived biochar samples produced under different carbonization conditions regarding Pb(II) and Cu(II). The biochar samples that were produced at 800 °C for 90 and 120 min contained the highest oxygen- and nitrogen-substituted carbons, which might contribute to a high metal-adsorption rate. The intensity of the phosphate bond was increased with the increasing of the carbonization temperature up to 800 °C and after 90 min of carbonization. The Pb(II) and Cu(II) adsorption capacities were the highest when the gingko-leaf-derived biochar was produced at 800 °C, and the removal rates were 99.2% and 34.2%, respectively. The highest removal rate was achieved when the intensity of the phosphate functional group in the biochar was the highest. Therefore, the gingko-leaf-derived biochar produced at 800 °C for 90 min can be used as an effective bio-adsorbent in the removal of metals from solutions.

Dissolved organic carbon biodegradability from leaf litter leachates of riparian tropical trees

NASA Astrophysics Data System (ADS)

Bastianoni, A.; Montoya, J. V.; Mendez, C.; Paolini, J.

2012-04-01

It is generally assumed that leaf litter with varying chemical composition may show different rates of mass loss, dissolved organic carbon (DOC) release, and DOC biodegradability. Leaf litter is composed of different organic compounds, which may differ in their release rates. Some authors consider leaf litter chemical quality (carbon to nitrogen ratio (C:N) and polyphenolics content) as an indicator of leaf litter mass losses and DOC released into stream water through leaching. In this research, we determined if leachate's DOC biodegradability exhibited a positive relationship with leaf litter chemical quality and leaf litter mass loss due to leaching. In order to test these hypotheses, leaf litter from six riparian tree species (Bambusa vulgaris; Castilla elastica; Artocarpus altilis; Cecropia peltata; Hura crepitans and Ficus maxima), present in the lower reaches of a fifth-order stream in northern Venezuela was collected during the dry season of 2010. To evaluate leaf litter mass loss, air-dried leaves were incubated in Milli-Q water at room temperature in the dark. After 1h, 6h, 1d, 2d, 4d, 8d and 15d, microcosms were removed from the assay to determine remaining mass. DOC biodegradability was measured using 24 h leachates that were added into a 1L glass flask containing 250mL of unfiltered stream water, 4g of stream sediment, and nutrient amendments until all incubations had equal initial DOC concentrations. Biodegradability of DOC was measured at 0, 1, 2, 5 and 7 days as the decrease in DOC concentration through time. Chemical characterization of leaf litter involved the determination of total concentrations of C, N, and poliphenolics. Three replicates were used for all analyses. Initial chemical characterization of leaf litter showed that only two species (C. elastica and A. altilis), had similar C:N ratios (~31). The other four species, showed different C and N contents but presented C:N ratios between 21 and 23. Total polyphenolics content varied greatly among species. Based on the degree of DOC biodegradability, after 1d of incubation, all species could be grouped into three distinct categories (high, intermediate and low). Then, biodegradability of DOC declined steadily until reaching near-constant values at day 7 probably reflecting less availability of labile C compounds. Breakdown rates were not significantly correlated with DOC decay rates (r=-0.580, P =0.228, n=6). However when the remaining DOC and the remaining mass for all species was evaluated, a significant negative correlation was observed (r=-0.567, P =0.014, n=18) contradicting our initial hypothesis. Such results might be a consequence of the presence of secondary metabolites alongside labile DOC in some species leachates which could prevent microbial C consumption. Therefore, the quality of C released by leaching, measured as its biodegradability, does not seem to have a relationship with the amount of C lost by leaching. This could influence the C budget of the riparian ecosystem since the proportion of C consumed by stream microbes is affected by the chemical quality of leaf litter leachates.

Deficiency and toxicity of boron: Alterations in growth, oxidative damage and uptake by citrange orange plants.

PubMed

Shah, Asad; Wu, Xiuwen; Ullah, Abid; Fahad, Shah; Muhammad, Riaz; Yan, Lei; Jiang, Cuncang

2017-11-01

Boron (B) deficiency and toxicity are the major factors that affect plant growth and yield. The present study revealed the effect of B deficiency and toxicity on plant growth, morphology, physiology, and cell structure. A hydroponic culture experiment was conducted with five B levels, B deficient (B0), sufficient (B20, B10, B40) and toxic (B100). Our results show that both B deficient as well as excess level inhibit plant growth. In B deficiency, the major visible symptoms were appeared in roots, while B excess burned the leaf margin of older leaves. The antioxidant enzymes including superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and ascorbate peroxidase (APX) decreased at B deficiency and also decreased up to some extent at B excess, while in sufficient treatments, the higher antioxidant enzymes were found at B20. In addition, the MDA concentration decreased at B deficiency and increased with B concentration. Moreover, the photosynthetic rate, transpiration rate, stomatal conductance, leaf gas exchange and intercellular CO 2 were reduced at both B deficiency as well as excess and higher at sufficient B20 treatment significantly. The chlorophyll and carotenoid content increased at B20 treatment, while decreased at B deficiency and excess. The middle lamellae of cell wall were found thick at B excess and normal at B20. The current study revealed that B deficiency as well as excess concentration affect plant growth and various morpho-physiological processes. Copyright © 2017 Elsevier Inc. All rights reserved.

In vitro propagation, ex vitro rooting and leaf micromorphology of Bauhinia racemosa Lam.: a leguminous tree with medicinal values.

PubMed

Sharma, Udit; Kataria, Vinod; Shekhawat, N S

2017-10-01

A micropropagation system for Bauhinia racemosa Lam. was developed involving axillary shoot proliferation and ex vitro rooting using nodal explants obtained from mature tree. MS medium with 3.0 mg l -1 BA (6-benzyladenine) was optimum for shoot bud induction. For shoot multiplication, mother explants were transferred repeatedly on medium containing low concentration of BA (0.75 mg l -1 ). Number of shoots was increased up to two passages and decreased thereafter. Shoot multiplication was further enhanced on MS medium containing 0.25 mg l -1 each of BA and Kin (Kinetin) with 0.1 mg l -1 of NAA (α-naphthalene acetic acid). Addition of 0.004 mg l -1 TDZ (thidiazuron) increased the rate of shoot multiplication and 21.81 ± 1.26 shoots per culture vessel were obtained. In vitro regenerated shoots were rooted under ex vitro conditions treated with 400 mg l -1 IBA (indole-3-butyric acid) for 7 min on sterile soilrite. After successful hardening in greenhouse, ex vitro rooted plants were transferred to the field conditions with ≈85% of survival rate. Micromorphological changes were observed on leaf surface i.e. development of vein density and trichomes and stomatal appearance, when plants were subjected to environmental conditions. This is the first report on in vitro regeneration of B. racemosa from mature tree.

Organochlorine Turnover in Forest Ecosystems: The Missing Link in the Terrestrial Chlorine Cycle

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

A Leri; S Myneni

Research in the last 20 years has shown that chlorine undergoes transformations between inorganic and organic forms as part of a complex biogeochemical cycle in terrestrial systems. Natural organochlorine production appears to be associated with the decomposition of plant material on the soil surface, though the chlorine cycle budget implies that a proportion of natural organochlorine enters soil through plant litter and atmospheric deposition as well. Organochlorine compounds may form through biotic and abiotic pathways, but the rates and magnitude of production in the field remain undefined. We have performed a time-dependent trace of chlorine concentration through forest ecosystems, revealingmore » distinct fractions of naturally produced organochlorine in plant biomass. Aliphatic organochlorine constitutes an intrinsic component of healthy leaves that persists through senescence and humification of the plant material, making a substantial contribution to the pool of soil organochlorine. Plant leaves also contain soluble aromatic organochlorine compounds that leach from leaf litter during early decay stages. As decay progresses, high concentrations of insoluble aromatic organochlorine accrue in the humus, through de novo production as well as adsorption. The rates of aromatic organochlorine production and degradation vary seasonally and conversely. This study presents the first unambiguous evidence that there exist multiple pools of chlorinated organic matter in the soil environment and that leaf litter deposition makes a significant and refractory contribution to the soil organochlorine pool, providing key insights into the biogeochemical chlorine cycle.« less

Stimulating productivity of hydroponic lettuce in controlled environments with triacontanol

NASA Technical Reports Server (NTRS)

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

1987-01-01

Triacontanol (1-triacontanol) applied as a foliar spray at 10(-7) M to 4-day-old, hydroponically grown leaf lettuce (Lactuca sativa L.) seedlings in a controlled environment increased leaf fresh and dry weight 13% to 20% and root fresh and dry weight 13% to 24% 6 days after application, relative to plants sprayed with water. When applied at 8 as well as 4 days after seeding, triacontanol increased plant fresh and dry weight, leaf area, and mean relative growth rate 12% to 37%. There was no benefit of repeating application of triacontanol in terms of leaf dry weight gain.

Are leaf physiological traits related to leaf water isotopic enrichment in restinga woody species?

PubMed

Rosado, Bruno H P; De Mattos, Eduardo A; Sternberg, Leonel Da S L

2013-09-01

During plant-transpiration, water molecules having the lighter stable isotopes of oxygen and hydrogen evaporate and diffuse at a faster rate through the stomata than molecules having the heavier isotopes, which cause isotopic enrichment of leaf water. Although previous models have assumed that leaf water is well-mixed and isotopically uniform, non-uniform stomatal closure, promoting different enrichments between cells, and different pools of water within leaves, due to morpho-physiological traits, might lead to inaccuracies in isotopic models predicting leaf water enrichment. We evaluate the role of leaf morpho-physiological traits on leaf water isotopic enrichment in woody species occurring in a coastal vegetation of Brazil known as restinga. Hydrogen and oxygen stable isotope values of soil, plant stem and leaf water and leaf traits were measured in six species from restinga vegetation during a drought and a wet period. Leaf water isotopic enrichment relative to stem water was more homogeneous among species during the drought in contrast to the wet period suggesting convergent responses to deal to temporal heterogeneity in water availability. Average leaf water isotopic enrichment relative to stem water during the drought period was highly correlated with relative apoplastic water content. We discuss this observation in the context of current models of leaf water isotopic enrichment as a function of the Péclet effect. We suggest that future studies should include relative apoplastic water content in isotopic models.

Long-distance signaling within Coleus x hybridus leaves; mediated by changes in intra-leaf CO2?

NASA Technical Reports Server (NTRS)

Stahlberg, R.; Van Volkenburgh, E.; Cleland, R. E.

2001-01-01

Rapid long-distance signaling in plants can occur via several mechanisms, including symplastic electric coupling and pressure waves. We show here in variegated Coleus leaves a rapid propagation of electrical signals that appears to be caused by changes in intra-leaf CO2 concentrations. Green leaf cells, when illuminated, undergo a rapid depolarization of their membrane potential (Vm) and an increase in their apoplastic pH (pHa) by a process that requires photosynthesis. This is followed by a slower hyperpolarization of Vm and apoplastic acidification, which do not require photosynthesis. White (chlorophyll-lacking) leaf cells, when in isolated white leaf segments, show only the slow response, but when in mixed (i.e. green and white) segments, the rapid Vm depolarization and increase in pHa propagate over more than 10 mm from the green to the white cells. Similarly, these responses propagate 12-20 mm from illuminated to unilluminated green cells. The fact that the propagation of these responses is eliminated when the leaf air spaces are infiltrated with solution indicates that the signal moves in the apoplast rather than the symplast. A depolarization of the mesophyll cells is induced in the dark by a decrease in apoplastic CO2 but not by an increase in pHa. These results support the hypothesis that the propagating signal for the depolarization of the white mesophyll cells is a photosynthetically induced decrease in the CO2 level of the air spaces throughout the leaf.

Relationships between phenology and the remobilization of nitrogen, phosphorus and potassium in branches of eight Mediterranean evergreens.

PubMed

Milla, R; Castro-Díez, P; Maestro-Martínez, M; Montserrat-Martí, G

2005-10-01

Few studies have examined the effects of plant growth on nutrient remobilization in phenologically contrasting species. Here we evaluated the consequences of above-ground seasonality of growth and leaf shedding on the remobilization of nutrients from branches in eight evergreen Mediterranean phanaerophytes that differ widely in phenology. Vegetative growth, flower bud formation, flowering, fruiting, leaf shedding, and the variations in nitrogen (N), phosphorus (P) and potassium (K) pools in branches throughout the year were monitored in each species. Nitrogen and P remobilization occurred in summer, after vegetative growth and synchronously with leaf shedding. Despite the time-lag between growth and remobilization, the branches that invested more nutrients in vegetative growth also remobilized more nutrients from their old organs. Potassium remobilization peaked in the climatically harshest periods, and appears to be related to osmotic requirements. We conclude that N and P remobilization occurs mainly associated with leaf senescence, which might be triggered by factors such as the replenishment of nutrient reserves in woody organs, the hormonal relations between new and old leaves, or the constraints that summer drought poses on the amount of leaf area per branch in summer.

Leaf age affects the responses of foliar injury and gas exchange to tropospheric ozone in Prunus serotina seedlings.

PubMed

Zhang, Jianwei; Schaub, Marcus; Ferdinand, Jonathan A; Skelly, John M; Steiner, Kim C; Savage, James E

2010-08-01

We investigated the effect of leaf age on the response of net photosynthesis (A), stomatal conductance (g(wv)), foliar injury, and leaf nitrogen concentration (N(L)) to tropospheric ozone (O(3)) on Prunus serotina seedlings grown in open-plots (AA) and open-top chambers, supplied with either carbon-filtered or non-filtered air. We found significant variation in A, g(wv), foliar injury, and N(L) (P < 0.05) among O(3) treatments. Seedlings in AA showed the highest A and g(wv) due to relatively low vapor pressure deficit (VPD). Older leaves showed significantly lower A, g(wv), N(L), and higher foliar injury (P < 0.001) than younger leaves. Leaf age affected the response of A, g(wv), and foliar injury to O(3). Both VPD and N(L) had a strong influence on leaf gas exchange. Foliar O(3)-induced injury appeared when cumulative O(3) uptake reached 8-12 mmol m(-2), depending on soil water availability. The mechanistic assessment of O(3)-induced injury is a valuable approach for a biologically relevant O(3) risk assessment for forest trees. Published by Elsevier Ltd.

Quantitative PCR monitoring of the effect of azoxystrobin treatments on Mycosphaerella graminicola epidemics in the field.

PubMed

Rohel, Eric A; Laurent, Paul; Fraaije, Bart A; Cavelier, Nadine; Hollomon, Derek W

2002-03-01

Quantitative PCR and visual monitoring of Mycosphaerella graminicola epidemics were performed to investigate the effect of curative and preventative applications of azoxystrobin in wheat field crops. A non-systemic protectant and a systemic curative fungicide, chlorothalonil and epoxiconazole, respectively, were used as references. PCR diagnosis detected leaf infection by M graminicola 3 weeks before symptom appearance, thereby allowing a clear distinction between curative and preventative treatments. When applied 1 week after the beginning of infection, azoxystrobin curative activity was intermediate between chlorothalonil (low effect) and epoxiconazole. When applied preventatively, none of the fungicides completely prevented leaf infection. There was some indication that azoxystrobin preventative treatments may delay fungal DNA increase more than epoxiconazole at the beginning of leaf infection. Both curative and preventative treatments increased the time lapse between the earliest PCR detection and the measurement of a 10% necrotic leaf area. Azoxystrobin only slightly decreased the speed of necrotic area increase compared with epoxiconazole. Hence, azoxystrobin activity toward M graminicola mainly resides in lengthening the time lapse between the earliest PCR detection and the measurement of a 10% necrotic leaf area. Information generated in this way is useful for optimal positioning of azoxystrobin treatments on M graminicola.

Tuning Transpiration by Interfacial Solar Absorber-Leaf Engineering.

PubMed

Zhuang, Shendong; Zhou, Lin; Xu, Weichao; Xu, Ning; Hu, Xiaozhen; Li, Xiuqiang; Lv, Guangxin; Zheng, Qinghui; Zhu, Shining; Wang, Zhenlin; Zhu, Jia

2018-02-01

Plant transpiration, a process of water movement through a plant and its evaporation from aerial parts especially leaves, consumes a large component of the total continental precipitation (≈48%) and significantly influences global water distribution and climate. To date, various chemical and/or biological explorations have been made to tune the transpiration but with uncertain environmental risks. In recent years, interfacial solar steam/vapor generation is attracting a lot of attention for achieving high energy transfer efficiency. Various optical and thermal designs at the solar absorber-water interface for potential applications in water purification, seawater desalination, and power generation appear. In this work, the concept of interfacial solar vapor generation is extended to tunable plant transpiration by showing for the first time that the transpiration efficiency can also be enhanced or suppressed through engineering the solar absorber-leaf interface. By tuning the solar absorption of membrane in direct touch with green leaf, surface temperature of green leaf will change accordingly because of photothermal effect, thus the transpiration efficiency as well as temperature and relative humidity in the surrounding environment will be tuned. This tunable transpiration by interfacial absorber-leaf engineering can open an alternative avenue to regulate local atmospheric temperature, humidity, and eventually hydrologic cycle.

Microwave model prediction and verifications for vegetated terrain

NASA Technical Reports Server (NTRS)

Fung, A. K.

1985-01-01

To understand the scattering properties of a deciduous and a coniferous type vegetation scattering models were developed assuming either a disc type leaf or a needle type leaf. The major effort is to calculate the corresponding scattering phase functions and then each of the functions is used in a radiative transfer formulation to compute the scattering intensity and consequently the scattering coefficient. The radiative transfer formulation takes into account the irregular ground surface by including the rough soil surface in the boundary condition. Thus, the scattering model accounts for volume scattering inside the vegetation layer, the surface scattering from the ground and the interaction between scattering from the soil surface and the vegetation volume. The contribution to backscattering by each of the three scattering mechanisms is illustrated along with the effects of each layer or surface parameter. The major difference between the two types of vegetation is that when the incident wavelength is comparable to the size of the leaf there is a peak appearing in the mid angular region of the backscattering curve for the disc type leaf whereas it is a dip in the same region for a needle type leaf.

Major diffusion leaks of clamp-on leaf cuvettes still unaccounted: how erroneous are the estimates of Farquhar et al. model parameters?

PubMed

Rodeghiero, Mirco; Niinemets, Ulo; Cescatti, Alessandro

2007-08-01

Estimates of leaf gas-exchange characteristics using standard clamp-on leaf chambers are prone to errors because of diffusion leaks. While some consideration has been given to CO(2) diffusion leaks, potential water vapour diffusion leaks through chamber gaskets have been neglected. We estimated diffusion leaks of two clamp-on Li-Cor LI-6400 (Li-Cor, Inc., Lincoln, NE, USA) leaf chambers with polymer foam gaskets and enclosing either 2 or 6 cm(2) leaf area, and conducted a sensitivity analysis of the diffusion leak effects on Farquhar et al. photosynthesis model parameters - the maximum carboxylase activity of ribulose 1 x 5-bisphosphate carboxylase/oxygenase (Rubisco) (V(cmax)), capacity for photosynthetic electron transport (J(max)) and non-photorespiratory respiration rate in light (R(d)). In addition, net assimilation rate (A(n)) versus intercellular CO(2) (C(i)) responses were measured in leaves of Mediterranean evergreen species Quercus ilex L. enclosing the whole leaf chamber in a polyvinyl fluoride bag flushed with the exhaust air of leaf chamber, thereby effectively reducing the CO(2) and water vapour gradients between ambient air and leaf chamber. For the empty chambers, average diffusion leak for CO(2), K(CO2), (molar flow rate corresponding to unit CO(2) mole fraction difference) was ca. 0.40 micromol s(-1). K(CO2) increased ca. 50% if a dead leaf was clamped between the leaf chamber. Average diffusion leak for H(2)O was ca. 5- to 10-fold larger than the diffusion leak for CO(2). Sensitivity analyses demonstrated that the consequence of a CO(2) diffusion leak was apparent enhancement of A(n) at high CO(2) mole fraction and reduction at lower CO(2) mole fraction, and overall compression of C(i) range. As the result of these modifications, Farquhar et al. model parameters were overestimated. The degree of overestimation increased in the order of V(cmax) < J(max) < R(d), and was larger for smaller chambers and for leaves with lower photosynthetic capacity, leading to overestimation of all three parameters by 70-290% for 2 cm(2), and by 10-60% for 6 cm(2) chamber. Significant diffusion corrections (5-36%) were even required for leaves with high photosynthetic capacity measured in largest chamber. Water vapour diffusion leaks further enhanced the overestimation of model parameters. For small chambers and low photosynthetic capacities, apparent C(i) was simulated to decrease with increasing A(n) because of simultaneous CO(2) and H(2)O diffusion leaks. Measurements in low photosynthetic capacity Quercus ilex leaves enclosed in 2 cm(2) leaf chamber exhibited negative apparent C(i) values at highest A(n). For the same leaves measured with the entire leaf chamber enclosed in the polyvinyl fluoride bag, C(i) and A(n) increased monotonically. While the measurements without the bag could be corrected for diffusion leaks, the required correction in A(n) and transpiration rates was 100-500%, and there was large uncertainty in Farquhar et al. model parameters derived from 'corrected'A(n)/C(i) response curves because of uncertainties in true diffusion leaks. These data demonstrate that both CO(2) and water vapour diffusion leaks need consideration in measurements with clamp-on leaf cuvettes. As plants in natural environments are often characterized by low photosynthetic capacities, cuvette designs need to be improved for reliable measurements in such species.

Pulvinus activity, leaf movement and leaf water-use efficiency of bush bean (Phaseplus vulgaris L.) in a hot environment.

PubMed

Raeini-Sarjaz, Mahmoud; Chalavi, Vida

2008-11-01

Pulvinus activity of Phaseolus species in response to environmental stimuli plays an essential role in heliotropic leaf movement. The aims of this study were to monitor the continuous daily pulvinus movement and pulvinus temperature, and to evaluate the effects of leaf movements, on a hot day, on instantaneous leaf water-use efficiency (WUEi), leaf gas exchange, and leaf temperature. Potted plants of Phaseolus vulgaris L. var. Provider were grown in Chicot sandy loam soil under well-watered conditions in a greenhouse. When the second trifoliate leaf was completely extended, one plant was selected to measure pulvinus movement using a beta-ray gauging (BRG) meter with a point source of thallium-204 (204Tl). Leaf gas exchange measurements took place on similar leaflets of three plants at an air temperature interval of 33-42 degrees C by a steady-state LI-6200 photosynthesis system. A copper-constantan thermocouple was used to monitor pulvinus temperature. Pulvinus bending followed the daily diurnal rhythm. Significant correlations were found between the leaf-incident angle and the stomatal conductance (R2 = 0.54; P < 0.01), and photosynthesis rate (R2 = 0.84; P < 0.01). With a reduction in leaf-incidence angle and increase in air temperature, WUEi was reduced. During the measurements, leaf temperature remained below air temperature and was a significant function of air temperature (r = 0.92; P < 0.01). In conclusion, pulvinus bending followed both light intensity and air temperature and influenced leaf gas exchange.

Leaf Photosynthesis and Respiration of High CO2-Grown Tobacco Plants Selected for Survival under CO2 Compensation Point Conditions 1

PubMed Central

Delgado, Esteban; Azcón-Bieto, Joaquim; Aranda, Xavier; Palazón, Javier; Medrano, Hipólito

1992-01-01

Four self-pollinated, doubled-haploid tobacco, (Nicotiana tabacum L.) lines (SP422, SP432, SP435, and SP451), selected as haploids by survival in a low CO2 atmosphere, and the parental cv Wisconsin-38 were grown from seed in a growth room kept at high CO2 levels (600-700 parts per million). The selected plants were much larger (especially SP422, SP432, and SP451) than Wisconsin-38 nine weeks after planting. The specific leaf dry weight and the carbon (but not nitrogen and sulfur) content per unit area were also higher in the selected plants. However, the chlorophyll, carotenoid, and alkaloid contents and the chlorophyll a/b ratio varied little. The net CO2 assimilation rate per unit area measured in the growth room at high CO2 was not higher in the selected plants. The CO2 assimilation rate versus intercellular CO2 curve and the CO2 compensation point showed no substantial differences among the different lines, even though these plants were selected for survival under CO2 compensation point conditions. Adult leaf respiration rates were similar when expressed per unit area but were lower in the selected lines when expressed per unit dry weight. Leaf respiration rates were negatively correlated with specific leaf dry weight and with the carbon content per unit area and were positively correlated with nitrogen and sulfur content of the dry matter. The alternative pathway was not involved in respiration in the dark in these leaves. The better carbon economy of tobacco lines selected for low CO2 survival was not apparently related to an improvement of photosynthesis rate but could be related, at least partially, to a significantly reduced respiration (mainly cytochrome pathway) rate per unit carbon. ImagesFigure 1 PMID:16668769

[Effects of postponed basal nitrogen application with reduced nitrogen rate on grain yield and nitrogen use efficiency of south winter wheat].

PubMed

Zhang, Lei; Shao, Yu Hang; Gu, Shi Lu; Hu, Hang; Zhang, Wei Wei; Tian, Zhong Wei; Jiang, Dong; Dai, Ting Bo

2016-12-01

Excessive nitrogen (N) fertilizer application has led to a reduction of nitrogen use efficiency and environmental problems. It was of great significance for high-yield and high-efficiency cultivation to reduce N fertilizer application with modified application strategies. A two-year field experiment was conducted to study effects of different N application rates at basal and seedling application stages on grain yield and nitrogen use efficiency. Taking the conventional nitrogen application practice (240 kg N·hm -2 with application at basal, jointing, and booting stages at ratios of 5:3:2, respectively) as control, a field trial was conducted at different N application rates (240, 180 and 150 kg N·hm -2 , N 240 , N 180 and N 150 , respectively) and different application times [basal (L 0 ), fourth (L 4 ) and sixth leaf stage (L 6 )] to investigate the effects on grain yield and nitrogen use efficiency. The results indicated that grain yield decreased along with reducing the N application rate, but it had no significant difference between N 240 and N 180 while decreased significantly under N 150 . Nitrogen agronomy and recovery efficiency were all highest under N 180 . Among different N application stages, grain yield and nitrogen use efficiency were highest under L 4 . N 180 L 4 had no signifi-cant difference with control in grain yield, but its nitrogen use efficiency was significantly higher. The leaf area index, flag leaf photosynthesis rate, leaf nitrogen content, activity of nitrogen reductase and glutamine synthase in flag leaf, dry matter and N accumulation after jointing of N 180 L 4 had no significant difference with control. In an overall view, postponing basal N fertilizer application at reduced nitrogen rate could maintain high yield and improve nitrogen use efficiency through improving photosynthetic production capacity and promoting nitrogen uptake and assimilation.

Global scale analysis and evaluation of an improved mechanistic representation of plant nitrogen and carbon dynamics in the Community Land Model (CLM)

NASA Astrophysics Data System (ADS)

Ghimire, B.; Riley, W. J.; Koven, C. D.; Randerson, J. T.; Mu, M.; Kattge, J.; Rogers, A.; Reich, P. B.

2014-12-01

In many ecosystems, nitrogen is the most limiting nutrient for plant growth and productivity. However mechanistic representation of nitrogen uptake linked to root traits, and functional nitrogen allocation among different leaf enzymes involved in respiration and photosynthesis is currently lacking in Earth System models. The linkage between nitrogen availability and plant productivity is simplistically represented by potential photosynthesis rates, and is subsequently downregulated depending on nitrogen supply and other nitrogen consumers in the model (e.g., nitrification). This type of potential photosynthesis rate calculation is problematic for several reasons. Firstly, plants do not photosynthesize at potential rates and then downregulate. Secondly, there is considerable subjectivity on the meaning of potential photosynthesis rates. Thirdly, there exists lack of understanding on modeling these potential photosynthesis rates in a changing climate. In addition to model structural issues in representing photosynthesis rates, the role of plant roots in nutrient acquisition have been largely ignored in Earth System models. For example, in CLM4.5, nitrogen uptake is linked to leaf level processes (e.g., primarily productivity) rather than root scale process involved in nitrogen uptake. We present a new plant model for CLM with an improved mechanistic presentation of plant nitrogen uptake based on root scale Michaelis Menten kinetics, and stronger linkages between leaf nitrogen and plant productivity by inferring relationships observed in global databases of plant traits (including the TRY database and several individual studies). We also incorporate improved representation of plant nitrogen leaf allocation, especially in tropical regions where significant over-prediction of plant growth and productivity in CLM4.5 simulations exist. We evaluate our improved global model simulations using the International Land Model Benchmarking (ILAMB) framework. We conclude that mechanistic representation of leaf-level nitrogen allocation and a theoretically consistent treatment of competition with belowground consumers leads to overall improvements in CLM4.5's global carbon cycling predictions.

The electrochemical-proton-gradient-activated states of F0F1 ATPase in plant mitochondria as revealed by detergents.

PubMed

Valerio, M; Diolez, P; Haraux, F

1993-09-01

ATP hydrolysis, triggered by the addition of polyoxyethylene-9-lauryl ether (Lubrol) or lauryldimethylamine oxide (LDAO) to energized plant mitochondria was studied in some details. The membrane disruption was quasi-instantaneous (2-3 s) with both detergents, as shown by the decrease of turbidity and the stopping of respiration. In pea leaf mitochondria, Lubrol triggered ATP hydrolysis in almost the same way as valinomycin plus nigericin, except that the activity was slightly stimulated and became insensitive to carboxyatractyloside. This allowed investigations of ATP hydrolysis without any interference of the ATP/ADP antiporter or the phosphate carrier. Lubrol did not prevent the ATPase from deactivating in pea leaf mitochondria, and did not trigger any ATP hydrolysis in potato tuber mitochondria. At variance with Lubrol, LDAO changed the properties of the F0F1 ATPase. It made the enzyme oligomycin insensitive and froze it in an activated state. The activity was also 5-8-times stimulated in pea leaf mitochondria. Moreover, LDAO revealed an important ATP hydrolase activity when added to energized potato tuber mitochondria. Despite the specific effect of LDAO, the activity triggered by this detergent strongly depended on the energized state of the organelles before detergent addition. From this study, it is concluded that the electrochemical proton gradient is completely necessary to activate the F0F1-ATPase in intact plant mitochondria, as known in chloroplasts and suggested by some reports in animal mitochondria. Moreover, it is suggested that the main difference between the enzymes of pea leaf and potato tuber mitochondria is their rate of deactivation after the collapse of the transmembrane electrochemical potential difference. Finally, when properly used, detergents appear to be a powerful tool to probe the state of the ATPase in intact mitochondria, and maybe in more integrated systems.

The negative effects of cadmium on Bermuda grass growth might be offset by submergence.

PubMed

Tan, Shuduan; Huang, Huang; Zhu, Mingyong; Zhang, Kerong; Xu, Huaqin; Wang, Zhi; Wu, Xiaoling; Zhang, Quanfa

2013-10-01

Revegetation in the water-level-fluctuation zone (WLFZ) could stabilize riverbanks, maintain local biodiversity, and improve reservoir water quality in the Three Gorges Reservoir Region (TGRR). However, submergence and cadmium (Cd) may seriously affect the survival of transplantations. Bermuda grass (Cynodon dactylon) is a stoloniferous and rhizomatous prostrate weed displaying high growth rate. A previous study has demonstrated that Bermuda grass can tolerate deep submergence and Cd stress, respectively. In the present study, we further analyzed physiological responses of Bermuda grass induced by Cd-and-submergence stress. The ultimate goal was to explore the possibility of using Bermuda grass for revegetation in the WLFZ of China's TGRR and other riparian areas. The Cd-and-submergence-treated plants had higher malondialdehyde contents and peroxidase than control, and both increased with the Cd concentration increase. All treated plants catalase activity increased with the experimental duration increases, and their superoxide dismutase also gradually increased with the Cd concentration from 1 day to 15 days. Total biomass of the same Cd-and-submergence plants increased along the experimental duration as well. Plants exposed to Cd-and-submergence stress showed shoot elongation. The heights of all treated plants were taller than those of the control. Leaf chlorophyll contents, maximum leaf length, and soluble sugars contents of all the Cd-and-submergence-treated plants were more than those of the untreated control. Although Cd inhibits plants growth, decreases chlorophyll and biomass content, and with the submergence induced the leaf and shoot elongation, more part of the Cd-and-submergence stress plants appeared in the air, exhibited fast growth with maintenance of leaf color, which guaranteed the plants' photosynthesis, and ensured the total biomass and carbohydrate sustainability, further promoting Cd-and-submergence tolerance. The results imply that the negative effects of cadmium on Bermuda grass growth might be offset by submergence.

Evidence for the presence of a [2Fe-2S] ferredoxin in bean sprouts.

PubMed

Hirasawa, M; Sung, J D; Malkin, R; Zilber, A; Droux, M; Knaff, D B

1988-07-06

An iron-sulfur protein with properties similar to those of ferredoxins found in the leaves of higher plants has been isolated from bean sprouts--a non-photosynthetic plant tissue. The bean sprout protein has a molecular mass of 12.5 kDa and appears to contain a single [2Fe-2S] cluster. The absorbance and circular dichroism spectra of the bean sprout protein resemble those of spinach leaf ferredoxin and the bean sprout protein can replace spinach ferredoxin as an electron donor for NADP+ reduction, nitrite reduction and thioredoxin reduction by spinach leaf enzymes. Although the reduced bean sprout protein (Em = -440 mV) is a slightly stronger reductant than spinach ferredoxin and appears to be less acidic than spinach ferredoxin, the two proteins are similar enough so that the bean sprout protein is recognized by an antibody raised against spinach ferredoxin.

Plant tissue and the color infrared record

NASA Technical Reports Server (NTRS)

Pease, R. W.

1969-01-01

Green plant tissue should not be considered as having a uniguely high near-infrared reflectance but rather a low visual reflectance. Leaf tissue without chloroplasts appears to reflect well both visual and near infrared wavelengths. The sensitometry of color infrared film is such that a spectral imbalance strongly favoring infrared reflection is necessary to yield a red record. It is the absorption of visual light by chlorophyll that creates the imbalance that makes the typical red record for plants possible. Reflectance measurements of leaves that have been chemically blanched or which have gone into natural chloride decline strongly suggests that it is the rise in the visual reflectance that is most important in removing the imbalance and degrading the red CIR record. The role of water in leaves appears to be that of rendering epidermal membranes translucent so that the underlying chlorophyll controls the reflection rather than the leaf surface.

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

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.

A hairy-leaf gene, BLANKET LEAF, of wild Oryza nivara increases photosynthetic water use efficiency in rice.

PubMed

Hamaoka, Norimitsu; Yasui, Hideshi; Yamagata, Yoshiyuki; Inoue, Yoko; Furuya, Naruto; Araki, Takuya; Ueno, Osamu; Yoshimura, Atsushi

2017-12-01

High water use efficiency is essential to water-saving cropping. Morphological traits that affect photosynthetic water use efficiency are not well known. We examined whether leaf hairiness improves photosynthetic water use efficiency in rice. A chromosome segment introgression line (IL-hairy) of wild Oryza nivara (Acc. IRGC105715) with the genetic background of Oryza sativa cultivar 'IR24' had high leaf pubescence (hair). The leaf hairs developed along small vascular bundles. Linkage analysis in BC 5 F 2 and F 3 populations showed that the trait was governed by a single gene, designated BLANKET LEAF (BKL), on chromosome 6. IL-hairy plants had a warmer leaf surface in sunlight, probably due to increased boundary layer resistance. They had a lower transpiration rate under moderate and high light intensities, resulting in higher photosynthetic water use efficiency. Introgression of BKL on chromosome 6 from O. nivara improved photosynthetic water use efficiency in the genetic background of IR24.

Do Aphids Alter Leaf Surface Temperature Patterns During Early Infestation?

PubMed Central

Cahon, Thomas; Caillon, Robin

2018-01-01

Arthropods at the surface of plants live in particular microclimatic conditions that can differ from atmospheric conditions. The temperature of plant leaves can deviate from air temperature, and leaf temperature influences the eco-physiology of small insects. The activity of insects feeding on leaf tissues, may, however, induce changes in leaf surface temperatures, but this effect was only rarely demonstrated. Using thermography analysis of leaf surfaces under controlled environmental conditions, we quantified the impact of presence of apple green aphids on the temperature distribution of apple leaves during early infestation. Aphids induced a slight change in leaf surface temperature patterns after only three days of infestation, mostly due to the effect of aphids on the maximal temperature that can be found at the leaf surface. Aphids may induce stomatal closure, leading to a lower transpiration rate. This effect was local since aphids modified the configuration of the temperature distribution over leaf surfaces. Aphids were positioned at temperatures near the maximal leaf surface temperatures, thus potentially experiencing the thermal changes. The feedback effect of feeding activity by insects on their host plant can be important and should be quantified to better predict the response of phytophagous insects to environmental changes. PMID:29538342

Taxonomy, Traits, and Environment Determine Isoprenoid Emission from an Evergreen Tropical forest.

NASA Astrophysics Data System (ADS)

Taylor, T.; Alves, E. G.; Tota, J.; Oliveira Junior, R. C.; Camargo, P. B. D.; Saleska, S. R.

2016-12-01

Volatile isoprenoid emissions from the leaves of tropical forest trees significantly affects atmospheric chemistry, aerosols, and cloud dynamics, as well as the physiology of the emitting leaves. Emission is associated with plant tolerance to heat and drought stress. Despite a potentially central role of isoprenoid emissions in tropical forest-climate interactions, we have a poor understanding of the relationship between emissions and ecological axes of forest function. We used a custom instrument to quantify leaf isoprenoid emission rates from over 200 leaves and 80 trees at a site in the eastern Brazilian Amazon. We related standardized leaf emission capacity (EC: leaf emission rate at 1000 PAR) to tree taxonomy, height, light environment, wood traits, and leaf traits. Taxonomy was the strongest predictor of EC, and non-emitters could be found throughout the canopy. But we found that environment and leaf carbon economics constrained the upper bound of EC. For example, the relationship between EC and specific leaf area (SLA; fresh leaf area / dry mass) is described by an envelope with a decreasing upper bound on EC as SLA increases (quantile regression: 85th quantile, p<0.01). That result suggests a limitation on emissions related to leaf carbon investment strategies. EC was highest in the mid-canopy, and in leaves growing under less direct light. While inferences of ecosystem emissions focus on environmental conditions in the canopy, our results suggest that sub-canopy leaves are more responsive. This work is allowing us to develop an ecological understanding of isoprenoid emissions from forests, the basis for a predictive model of emissions that depends on both environmental factors and biological emission capacity that is grounded in plant traits and phylogeny.

Cereal Leaf Beetle (Coleoptera: Chrysomelidae) Regional Dispersion and Relationship With Wheat Stand Denseness.

PubMed

Reisig, Dominic D; Bacheler, Jack S; Herbert, D Ames; Heiniger, Ron; Kuhar, Thomas; Malone, Sean; Philips, Chris; Tilley, M Scott

2017-06-01

Cereal leaf beetle, Oulema melanopus L., is a pest of small grains and the literature conflicts on whether it is more abundant in sparse or dense stands of wheat. Our objectives were to determine the impact of stand denseness on cereal leaf beetle abundance and to investigate the regional dispersion of cereal leaf beetles across North Carolina and Virginia. One-hundred twenty fields were sampled across North Carolina and Virginia during 2011 for stand denseness, and cereal leaf beetle eggs, larvae, and adults. Two small-plot wheat experiments were planted in North Carolina using a low and a high seeding rate. Main plots were split, with one receiving a single nitrogen application and one receiving two. Egg density, but not larva or adult density, was positively correlated with stand denseness in the regional survey. Furthermore, regional spatial patterns of aggregation were noted for both stand denseness and egg number. In the small-plot experiments, seeding rate influenced stand denseness, but not nitrogen application. In one experiment, egg densities per unit area were higher in denser wheat, while in the other experiment, egg densities per tiller were lower in denser wheat. Larvae were not influenced by any factor. Overall, there were more cereal leaf beetle eggs in denser wheat stands. Previous observations that sparse stands of wheat are more prone to cereal leaf beetle infestation can be attributed to the fact that sparser stands have fewer tillers, which increases the cereal leaf beetle to tiller ratio compared with denser stands. © The Authors 2017. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Hydrogen isotope composition of leaf wax n-alkanes in Arabidopsis lines with different transpiration rates

NASA Astrophysics Data System (ADS)

Pedentchouk, N.; Lawson, T.; Eley, Y.; McAusland, L.

2012-04-01

Stable isotopic compositions of oxygen and hydrogen are used widely to investigate modern and ancient water cycles. The D/H composition of organic compounds derived from terrestrial plants has recently attracted significant attention as a proxy for palaeohydrology. However, the role of various plant physiological and biochemical factors in controlling the D/H signature of leaf wax lipids in extant plants remains unclear. The focus of this study is to investigate the effect of plant transpiration on the D/H composition of n-alkanes in terrestrial plants. This experiment includes 4 varieties of Arabidopsis thaliana that differ with respect to stomatal density and stomatal geometry. All 4 varieties were grown indoors under identical temperature, relative humidity, light and watering regimes and then sampled for leaf wax and leaf water stable isotopic measurements. During growth, stomatal conductance to carbon dioxide and water vapour were also determined. We found that the plants varied significantly in terms of their transpiration rates. Transpiration rates were significantly higher in Arabidopsis ost1 and ost1-1 varieties (2.4 and 3.2 mmol m-2 s-1, respectively) than in Arabidopsis RbohD and Col-0 (1.5 and 1.4). However, hydrogen isotope measurements of n-alkanes extracted from leaf waxes revealed a very different pattern. Varieties ost1, ost1-1, and RbohD have very similar deltaD values of n-C29 alkane (-125, -128, and -127 per mil), whereas the deltaD value of Col-0 is more negative (-137 per mil). The initial results of this work suggest that plant transpiration is decoupled from the D/H composition of n-alkanes. In other words, physical processes that affect water vapour movement between the plant and its environment apparently cannot account for the stable hydrogen isotope composition of organic compounds that comprise leaf waxes. Additional, perhaps biochemical, processes that affect hydrogen isotope fractionation during photosynthesis might need to be invoked to explain the reason for this decoupling. Our current work that also includes leaf water isotopic measurements will provide further details regarding the role of transpiration in controlling the deltaD values of leaf lipids.

Stomata size and spatial pattern effects on leaf gas exchange - a quantitative assessment of plant evolutionary choices

NASA Astrophysics Data System (ADS)

Or, Dani; Assouline, Shmuel; Aminzadeh, Milad; Haghighi, Erfan; Schymanski, Stan; Lehmann, Peter

2014-05-01

Land plants developed a dynamically gas-permeable layer at their leaf surfaces to allow CO2 uptake for photosynthesis while controlling water vapor loss through numerous adjustable openings (stomata) in the impervious leaf epidermis. Details of stomata structure, density and function may vary greatly among different plant families and respond to local environmental conditions, yet they share basic traits in dynamically controlling gaseous exchange rates by varying stomata apertures. We implement a pore scale gas diffusion model to quantitatively interpret the functionality of different combinations of stomata size and pattern on leaf gas exchange and thermal management based on data from fossil records and contemporary data sets. Considering all available data we draw several general conclusions concerning stomata design considerations: (1) the sizes and densities of stomata in the available fossil record leaves were designed to evaporate at rates in the range 0.75≤e/e0 ≤0.99 (relative to free water evaporation); (2) examination of evaporation curves show that for a given stomata size, the density (jointly defining the leaf evaporating area when fully open) was chosen to enable a high sensitivity in reducing evaporation rate with incremental stomatal closure, nevertheless, results show the design includes safety margins to account for different wind conditions (boundary layer thickness); (3) scaled for mean vapor flux, the size of stomata plays a minor role in the uniformity of leaf thermal field for a given stomata density. These principles enable rationale assessment of plant response to raising CO2, and provide a physical framework for considering the consequences of different stomata patterns (patchy) on leaf gas exchange (and thermal regime). In contrast with present quantitative description of traits and functionality of these dynamic covers in terms of gaseous diffusion resistance (or conductance), where stomata size, density and spatial pattern are lumped into a single effective resistance parameter, the present approach enables derivation of nuanced insights and offers predictive capabilities that link changes in stomata structure and geometrical attributes to quantifying environmental influences and feedbacks on leaf structure and function.

Circadian rhythms constrain leaf and canopy gas exchange in an Amazonian forest

NASA Astrophysics Data System (ADS)

Doughty, Christopher E.; Goulden, Michael L.; Miller, Scott D.; da Rocha, Humberto R.

2006-08-01

We used a controlled-environment leaf gas-exchange system and the micrometeorological technique eddy covariance to determine whether circadian rhythms constrain the rates of leaf and canopy gas exchange in an Amazonian forest over a day. When exposed to continuous and constant light for 20 to 48 hours leaves of eleven of seventeen species reduced their photosynthetic rates and closed their stomata during the normally dark period and resumed active gas exchange during the normally light period. Similarly, the rate of whole-forest CO2 uptake at a predetermined irradiance declined during the late afternoon and early morning and increased during the middle of the day. We attribute these cycles to circadian rhythms that are analogous to ones that have been reported for herbaceous plants in the laboratory. The importance of endogenous gas exchange rhythms presents a previously unrecognized challenge for efforts to both interpret and model land-atmosphere energy and mass exchange.

Trophic level responses differ as climate warms in Ireland

NASA Astrophysics Data System (ADS)

Donnelly, Alison; Yu, Rong; Liu, Lingling

2015-08-01

Effective ecosystem functioning relies on successful species interaction. However, this delicate balance may be disrupted if species do not respond to environmental change at a similar rate. Here we examine trends in the timing of spring phenophases of groups of species occupying three trophic levels as a potential indicator of ecosystem response to climate warming in Ireland. The data sets were of varying length (1976-2009) and from varying locations: (1) timing of leaf unfolding and May Shoot of a range of broadleaf and conifer tree species, (2) first appearance dates of a range of moth species, and (3) first arrival dates of a range of spring migrant birds. All three groups revealed a statistically significant ( P<0.01 and P<0.001) advance in spring phenology that was driven by rising spring temperature ( P<0.05; 0.45 °C /decade). However, the rate of advance was greater for moths (1.8 days/year), followed by birds (0.37 days/year) and trees (0.29 days/year). In addition, the length of time between (1) moth emergence and leaf unfolding and (2) moth emergence and bird arrival decreased significantly ( P<0.05 and P<0.001, respectively), indicating a decrease in the timing between food supply and demand. These differing trophic level response rates demonstrate the potential for a mismatch in the timing of interdependent phenophases as temperatures rise. Even though these data were not specifically collected to examine climate warming impacts, we conclude that such data may be used as an early warning indicator and as a means to monitor the potential for future ecosystem disruption to occur as climate warms.

Trophic level responses differ as climate warms in Ireland.

PubMed

Donnelly, Alison; Yu, Rong; Liu, Lingling

2015-08-01

Effective ecosystem functioning relies on successful species interaction. However, this delicate balance may be disrupted if species do not respond to environmental change at a similar rate. Here we examine trends in the timing of spring phenophases of groups of species occupying three trophic levels as a potential indicator of ecosystem response to climate warming in Ireland. The data sets were of varying length (1976-2009) and from varying locations: (1) timing of leaf unfolding and May Shoot of a range of broadleaf and conifer tree species, (2) first appearance dates of a range of moth species, and (3) first arrival dates of a range of spring migrant birds. All three groups revealed a statistically significant (P<0.01 and P<0.001) advance in spring phenology that was driven by rising spring temperature (P<0.05; 0.45 °C /decade). However, the rate of advance was greater for moths (1.8 days/year), followed by birds (0.37 days/year) and trees (0.29 days/year). In addition, the length of time between (1) moth emergence and leaf unfolding and (2) moth emergence and bird arrival decreased significantly (P<0.05 and P<0.001, respectively), indicating a decrease in the timing between food supply and demand. These differing trophic level response rates demonstrate the potential for a mismatch in the timing of interdependent phenophases as temperatures rise. Even though these data were not specifically collected to examine climate warming impacts, we conclude that such data may be used as an early warning indicator and as a means to monitor the potential for future ecosystem disruption to occur as climate warms.

Effects of harvest on the sustainability and leaf productivity of populations of two palm species in Maya homegardens.

PubMed

Martínez-Ballesté, Andrea; Martorell, Carlos

2015-01-01

Traditional management practices are usually thought to be sustainable. The Maya manage Sabal (Arecaceae) palms in homegardens, using their leaves for thatching. The sustainability of such production systems depends on the long-term persistence of palm populations, whereas resource availability also depends on the number of leaves on individual palms. We examined how leaf harvest affects Sabal yapa and S. mexicana population growth rates (λ) and leaf production, comparing traditional and alternative harvest regimes in terms of sustainability and productivity. Demographic, harvest and leaf production data were recorded for three years in two homegardens. We used general integral projection models linked to leaf-production models to describe population dynamics and productivity. Harvest had no effect on S. yapa's vital rates or on λ, but it changed the growth rate of individuals of S. mexicana, with a negligible impact on λ. Homegardens affected λ values, reflecting the species' ecological affinities. S. mexicana, introduced from mesic forests, required watering and shade; therefore, its population declined rapidly in the homegarden that lacked both water and shade. The λ of the xerophilic S. yapa was slightly larger without watering than with watering. Palms usually compensated for leaf extraction, causing the number of leaves harvested per individual to increase with harvest intensity. Nevertheless, traditional management is relatively mild, allowing standing leaves to accumulate but reducing the homegarden's yield. Apparently, the Maya do not seek to maximize annual production but to ensure the availability of large numbers of leaves in homegardens. These leaves may then be used when the entire roof of a hut needs to be replaced every few years.

Effects of Harvest on the Sustainability and Leaf Productivity of Populations of Two Palm Species in Maya Homegardens

PubMed Central

Martínez-Ballesté, Andrea; Martorell, Carlos

2015-01-01

Traditional management practices are usually thought to be sustainable. The Maya manage Sabal (Arecaceae) palms in homegardens, using their leaves for thatching. The sustainability of such production systems depends on the long-term persistence of palm populations, whereas resource availability also depends on the number of leaves on individual palms. We examined how leaf harvest affects Sabal yapa and S. mexicana population growth rates (λ) and leaf production, comparing traditional and alternative harvest regimes in terms of sustainability and productivity. Demographic, harvest and leaf production data were recorded for three years in two homegardens. We used general integral projection models linked to leaf-production models to describe population dynamics and productivity. Harvest had no effect on S. yapa’s vital rates or on λ, but it changed the growth rate of individuals of S. mexicana, with a negligible impact on λ. Homegardens affected λ values, reflecting the species’ ecological affinities. S. mexicana, introduced from mesic forests, required watering and shade; therefore, its population declined rapidly in the homegarden that lacked both water and shade. The λ of the xerophilic S. yapa was slightly larger without watering than with watering. Palms usually compensated for leaf extraction, causing the number of leaves harvested per individual to increase with harvest intensity. Nevertheless, traditional management is relatively mild, allowing standing leaves to accumulate but reducing the homegarden’s yield. Apparently, the Maya do not seek to maximize annual production but to ensure the availability of large numbers of leaves in homegardens. These leaves may then be used when the entire roof of a hut needs to be replaced every few years. PMID:25803029

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.

Antibacterial, Antibiofilm Effect of Burdock (Arctium lappa L.) Leaf Fraction and Its Efficiency in Meat Preservation.

PubMed

Lou, Zaixiang; Li, Cheng; Kou, Xingran; Yu, Fuhao; Wang, Hongxin; Smith, Gary M; Zhu, Song

2016-08-01

First, the antibacterial, antibiofilm effect and chemical composition of burdock (Arctium lappa L.) leaf fractions were studied. Then, the efficiency of burdock leaf fractions in pork preservation was evaluated. The results showed that burdock leaf fraction significantly inhibited the growth and biofilm development of Escherichia coli and Salmonella Typhimurium. MICs of burdock leaf fractions on E. coli and Salmonella Typhimurium were both 2 mg/ml. At a concentration of 2.0 mg/ml, the inhibition rates of the fraction on growth and development of E. coli and Salmonella Typhimurium biofilms were 78.7 and 69.9%, respectively. During storage, the log CFU per gram of meat samples treated with burdock leaf fractions decreased 2.15, compared with the samples without treatment. The shelf life of pork treated with burdock leaf fractions was extended 6 days compared with the pork without treatment, and the sensory property was obviously improved. Compared with the control group, burdock leaf fraction treatment significantly decreased the total volatile basic nitrogen value and pH of the meat samples. Chemical composition analysis showed that the burdock leaf fraction consisted of chlorogenic acid, caffeic acid, p-coumaric acid, rutin, cynarin, crocin, luteolin, arctiin, and quercetin. As a vegetable with an abundant source, burdock leaf is safe, affordable, and efficient in meat preservation, indicating that burdock leaf fraction is a promising natural preservative for pork.

A comparison of physiological indicators of sublethal cadmium stress in wetland plants

USGS Publications Warehouse

Mendelssohn, I.A.; McKee, K.L.; Kong, T.

2001-01-01

Physiological indices, including photosynthesis, chlorophyll fluorescence, adenylate energy charge (AEC) ratio, and leaf reflectance, were determined for Typha domingensis and Spartina alterniflora in response to increasing concentrations of Cd and compared with the growth responses of these species. Leaf expansion, the live/total ratio of plant aboveground biomass, and the aboveground regrowth rate after the initial harvests were significantly reduced with increasing Cd concentration in the growth medium. Of the four physiological responses measured, only photosynthesis and AEC responded to the Cd treatment before damage was visually apparent. Also, these indices were significantly correlated with leaf expansion rate and live/total ratio in most instances. Except at the end of the experiment, when the most stressed plants began to die, the Fv/Fm ratio was not significantly affected by the Cd treatment. The leaf spectral reflectance parameters showed no significant change during the entire treatment period. The significant correlation between the stress indicators and plant growth supported the findings that photosynthesis and AEC were the most responsive of the indicators tested, however, further research investigating other chlorophyll fluorescence and leaf reflectance parameters may demonstrate as well the value of these indicators in quantifying sublethal stress. ?? 2001 Elsevier Science B.V. All rights reserved.

Ontogenetic patterns of CO sub 2 exchange of Quercus rubra L. leaves during three flushes of shoot growth I. median flush leaves

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

Hanson, P.J.; Isebrands, J.G.; Dickson, R.E.

1988-03-01

Oak (Quercus) seedlings exhibit a pattern of shoot growth known to place demands on carbohydrate and nutrient reserves. This study was designed to determine ontogenetic patterns in CO{sub 2} exchanges properties of red oak leaves, and to determine if individual leaf CO{sub 2} exchange rates (CER) increase in response to the assimilate demand placed on a seedling during flushing. Northern red oak (Q. rubra L.) seedlings were grown in environments favorable for multiple flushes of shoot growth. Measurements of CER on single, attached, median leaves from each flush were made over a range of photosynthetic photon flux densities on plantsmore » at nine stages of seedling development through three flushes of growth. Carbon dioxide exchange rate of red oak leaves increased during leaf development up to and beyond full leaf expansion before decreasing an unusual pattern of photosynthesis during leaf ontogeny. Furthermore, first- and second-flush leaf CER initially decreased and then increased in conjunction with the third flush of shoot growth. These patterns indicate that red oak leaves have a capacity for CER adjustment in response to increase sink demand.« less

Impairment of leaf photosynthesis after insect herbivory or mechanical injury on common milkweed, Asclepias syriaca.

PubMed

Delaney, K J; Haile, F J; Peterson, R K D; Higley, L G

2008-10-01

Insect herbivory has variable consequences on plant physiology, growth, and reproduction. In some plants, herbivory reduces photosynthetic rate (Pn) activity on remaining tissue of injured leaves. We sought to better understand the influence of leaf injury on Pn of common milkweed, Asclepias syriaca (Asclepiadaceae), leaves. Initially, we tested whether Pn reductions occurred after insect herbivory or mechanical injury. We also (1) examined the duration of photosynthetic recovery, (2) compared mechanical injury with insect herbivory, (3) studied the relationship between leaf Pn with leaf injury intensity, and (4) considered uninjured leaf compensatory Pn responses neighboring an injured leaf. Leaf Pn was significantly reduced on mechanically injured or insect-fed leaves in all reported experiments except one, so some factor(s) (cardiac glycoside induction, reproductive investment, and water stress) likely interacts with leaf injury to influence whether Pn impairment occurs. Milkweed tussock moth larval herbivory, Euchaetes egle L. (Arctiidae), impaired leaf Pn more severely than mechanical injury in one experiment. Duration of Pn impairment lasted > 5 d to indicate high leaf Pn sensitivity to injury, but Pn recovery occurred within 13 d in one experiment. The degree of Pn reduction was more severe from E. egle herbivory than similar levels of mechanical tissue removal. Negative linear relationships characterized leaf Pn with percentage tissue loss from single E. egle-fed leaves and mechanically injured leaves and suggested that the signal to trigger leaf Pn impairment on remaining tissue of an injured leaf was amplified by additional tissue loss. Finally, neighboring uninjured leaves to an E. egle-fed leaf had a small (approximately 10%) degree of compensatory Pn to partly offset tissue loss and injured leaf Pn impairment.

Osmotic stress, endogenous abscisic acid and the control of leaf morphology in Hippuris vulgaris L

NASA Technical Reports Server (NTRS)

Goliber, T. E.; Feldman, L. J.

1989-01-01

Previous reports indicate that heterophyllous aquatic plants can be induced to form aerial-type leaves on submerged shoots when they are grown in exogenous abscisic acid (ABA). This study reports on the relationship between osmotic stress (e.g. the situation encountered by a shoot tip when it grows above the water surface), endogenous ABA (as measured by gas chromatography-electron capture detector) and leaf morphology in the heterophyllous aquatic plant, Hippuris vulgaris. Free ABA could not be detected in submerged shoots of H. vulgaris but in aerial shoots ABA occurred at ca. 40 ng (g fr wt)-1. When submerged shoots were osmotically stressed ABA appeared at levels of 26 to 40 ng (g fr wt)-1. These and other data support two main conclusions: (1) Osmotically stressing a submerged shoot causes the appearance of detectable levels of ABA. (2) The rise of ABA in osmotically stressed submerged shoots in turn induces a change in leaf morphology from the submerged to the aerial form. This corroborates the hypothesis that, in the natural environment, ABA levels rise in response to the osmotic stress encountered when a submerged shoot grows up through the water/air interface and that the increased ABA leads to the production of aerial-type leaves.

Response of an invasive liana to simulated herbivory: implications for its biological control

NASA Astrophysics Data System (ADS)

Raghu, S.; Dhileepan, K.; Treviño, M.

2006-05-01

Pre-release evaluation of the efficacy of biological control agents is often not possible in the case of many invasive species targeted for biocontrol. In such circumstances simulating herbivory could yield significant insights into plant response to damage, thereby improving the efficiency of agent prioritisation, increasing the chances of regulating the performance of invasive plants through herbivory and minimising potential risks posed by release of multiple herbivores. We adopted this approach to understand the weaknesses herbivores could exploit, to manage the invasive liana, Macfadyena unguis-cati. We simulated herbivory by damaging the leaves, stem, root and tuber of the plant, in isolation and in combination. We also applied these treatments at multiple frequencies. Plant response in terms of biomass allocation showed that at least two severe defoliation treatments were required to diminish this liana's climbing habit and reduce its allocation to belowground tuber reserves. Belowground damage appears to have negligible effect on the plant's biomass production and tuber damage appears to trigger a compensatory response. Plant response to combinations of different types of damage did not differ significantly to that from leaf damage. This suggests that specialist herbivores in the leaf-feeding guild capable of removing over 50% of the leaf tissue may be desirable in the biological control of this invasive species.

Large drought-induced variations in oak leaf volatile organic compound emissions during PINOT NOIR 2012

DOE PAGES

Geron, Chris; Gu, Lianhong; Daly, Ryan; ...

2015-12-17

Here, leaf-level isoprene and monoterpene emissions were collected and analyzed from five of the most abundant oak (Quercus) species in Central Missouri's Ozarks Region in 2012 during PINOT NOIR (Particle Investigations at a Northern Ozarks Tower – NOx, Oxidants, Isoprene Research). June measurements, prior to the onset of severe drought, showed isoprene emission rates and leaf temperature responses similar to those previously reported in the literature and used in Biogenic Volatile Organic Compound (BVOC) emission models. During the peak of the drought in August, isoprene emission rates were substantially reduced, and response to temperature was dramatically altered, especially for themore » species in the red oak subgenus (Erythrobalanus).« less

Macroecological and macroevolutionary patterns of leaf herbivory across vascular plants.

PubMed

Turcotte, Martin M; Davies, T Jonathan; Thomsen, Christina J M; Johnson, Marc T J

2014-07-22

The consumption of plants by animals underlies important evolutionary and ecological processes in nature. Arthropod herbivory evolved approximately 415 Ma and the ensuing coevolution between plants and herbivores is credited with generating much of the macroscopic diversity on the Earth. In contemporary ecosystems, herbivory provides the major conduit of energy from primary producers to consumers. Here, we show that when averaged across all major lineages of vascular plants, herbivores consume 5.3% of the leaf tissue produced annually by plants, whereas previous estimates are up to 3.8× higher. This result suggests that for many plant species, leaf herbivory may play a smaller role in energy and nutrient flow than currently thought. Comparative analyses of a diverse global sample of 1058 species across 2085 populations reveal that models of stabilizing selection best describe rates of leaf consumption, and that rates vary substantially within and among major plant lineages. A key determinant of this variation is plant growth form, where woody plant species experience 64% higher leaf herbivory than non-woody plants. Higher leaf herbivory in woody species supports a key prediction of the plant apparency theory. Our study provides insight into how a long history of coevolution has shaped the ecological and evolutionary relationships between plants and herbivores. © 2014 The Author(s) Published by the Royal Society. All rights reserved.

A Comparative Study of Proteolytic Mechanisms during Leaf Senescence of Four Genotypes of Winter Oilseed Rape Highlighted Relevant Physiological and Molecular Traits for NRE Improvement

PubMed Central

Girondé, Alexandra; Poret, Marine; Etienne, Philippe; Trouverie, Jacques; Bouchereau, Alain; Le Cahérec, Françoise; Leport, Laurent; Niogret, Marie-Françoise; Avice, Jean-Christophe

2015-01-01

Winter oilseed rape is characterized by a low N use efficiency related to a weak leaf N remobilization efficiency (NRE) at vegetative stages. By investigating the natural genotypic variability of leaf NRE, our goal was to characterize the relevant physiological traits and the main protease classes associated with an efficient proteolysis and high leaf NRE in response to ample or restricted nitrate supply. The degradation rate of soluble proteins and D1 protein (a thylakoid-bound protein) were correlated to N remobilization, except for the genotype Samouraï which showed a low NRE despite high levels of proteolysis. Under restricted nitrate conditions, high levels of soluble protein degradation were associated with serine, cysteine and aspartic proteases at acidic pH. Low leaf NRE was related to a weak proteolysis of both soluble and thylakoid-bound proteins. The results obtained on the genotype Samouraï suggest that the timing between the onset of proteolysis and abscission could be a determinant. The specific involvement of acidic proteases suggests that autophagy and/or senescence-associated vacuoles are implicated in N remobilization under low N conditions. The data revealed that the rate of D1 degradation could be a relevant indicator of leaf NRE and might be used as a tool for plant breeding. PMID:27135221

Plumbing the depths: extracellular water storage in specialized leaf structures and its functional expression in a three-domain pressure -volume relationship.

PubMed

Nguyen, Hoa T; Meir, Patrick; Wolfe, Joe; Mencuccini, Maurizio; Ball, Marilyn C

2017-07-01

A three-domain pressure-volume relationship (PV curve) was studied in relation to leaf anatomical structure during dehydration in the grey mangrove, Avicennia marina. In domain 1, relative water content (RWC) declined 13% with 0.85 MPa decrease in leaf water potential, reflecting a decrease in extracellular water stored primarily in trichomes and petiolar cisternae. In domain 2, RWC decreased by another 12% with a further reduction in leaf water potential to -5.1 MPa, the turgor loss point. Given the osmotic potential at full turgor (-4.2 MPa) and the effective modulus of elasticity (~40 MPa), domain 2 emphasized the role of cell wall elasticity in conserving cellular hydration during leaf water loss. Domain 3 was dominated by osmotic effects and characterized by plasmolysis in most tissues and cell types without cell wall collapse. Extracellular and cellular water storage could support an evaporation rate of 1 mmol m -2 s -1 for up to 54 and 50 min, respectively, before turgor loss was reached. This study emphasized the importance of leaf anatomy for the interpretation of PV curves, and identified extracellular water storage sites that enable transient water use without substantive turgor loss when other factors, such as high soil salinity, constrain rates of water transport. © 2016 John Wiley & Sons Ltd.

First Report of Leaf Spot Caused by Alternaria tenuissima on Black Chokeberry (Aronia melanocarpa) in Korea

PubMed Central

Wee, Jung-In; Park, Jong-Han; Back, Chang-Gi; You, Young-Hyun

2016-01-01

In July 2015, diseased leaves of black chokeberry (Aronia melanocarpa) were observed in Danyang and Gochang, Korea. The symptoms appeared as circular or irregular brown leaf spots, from which Alternaria tenuissima was isolated. The isolates were cultured on potato dextrose agar, and their morphological characteristics were observed under a light microscope. The colonies were whitish to ash colored. The pathogenicity test on healthy black chokeberry leaves produced circular brown spots, in line with the original symptoms. Molecular analyses of the ITS, GPD, RPB2, and TEF genes were conducted to confirm the identity of the pathogen. The phylogeny of the multi-gene sequences indicated that the causal agent was A. tenuissima. This study is the first report of A. tenuissima leaf spot on black chokeberry (A. melanocarpa). PMID:27790070

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.

Nutrient dynamics and decomposition of riparian Arundinaria gigantea (Walt.)Muhl. leaves in southern Illinois

USDA-ARS?s Scientific Manuscript database

Leaf litter quality and quantity can influence soil nutrient dynamics and stream productivity through decomposition and serving as allochthonous stream inputs. Leaf deposition, nitrogen (N)-resorption efficiency and proficiency, and decomposition rates were analyzed in riparian stands of Arundinaria...

Leaf photosynthetic and water-relations responses for 'Valencia' orange trees exposed to oxidant air pollution

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

Olszyk, D.M.; Takemoto, B.K.; Poe, M.

1991-01-01

Leaf responses were measured to test a hypothesis that reduced photosynthetic capacity and/or altered water relations were associated with reductions in yield for 'Valencia' orange trees (Citrus sinensis (L.), Osbeck) exposed to ambient oxidant air pollution. Exposures were continuous for 4 years to three levels of oxidants (in charcoal-filtered, half-filtered, and non-filtered air). Oxidants had no effect on net leaf photosynthetic rates or on photosynthetic pigment concentrations. A single set of measurements indicated that oxidants increased leaf starch concentrations (24%) prior to flowering, suggesting a change in photosynthate allocation. Leaves exposed to oxidants had small, but consistent, changes in watermore » relations over the summer growing season, compared to trees growing in filtered air. Other changes included decreased stomatal conductance (12%) and transpiration (9%) rates, and increased water pressure potentials (5%). While all responses were subtle, their cumulative impact over 4 years indicated that 'Valencia' orange trees were subject to increased ambient oxidant stress.« less

A novel method for routine quality assurance of volumetric-modulated arc therapy.

PubMed

Wang, Qingxin; Dai, Jianrong; Zhang, Ke

2013-10-01

Volumetric-modulated arc therapy (VMAT) is delivered through synchronized variation of gantry angle, dose rate, and multileaf collimator (MLC) leaf positions. The delivery dynamic nature challenges the parameter setting accuracy of linac control system. The purpose of this study was to develop a novel method for routine quality assurance (QA) of VMAT linacs. ArcCheck is a detector array with diodes distributing in spiral pattern on cylindrical surface. Utilizing its features, a QA plan was designed to strictly test all varying parameters during VMAT delivery on an Elekta Synergy linac. In this plan, there are 24 control points. The gantry rotates clockwise from 181° to 179°. The dose rate, gantry speed, and MLC positions cover their ranges commonly used in clinic. The two borders of MLC-shaped field seat over two columns of diodes of ArcCheck when the gantry rotates to the angle specified by each control point. The ratio of dose rate between each of these diodes and the diode closest to the field center is a certain value and sensitive to the MLC positioning error of the leaf crossing the diode. Consequently, the positioning error can be determined by the ratio with the help of a relationship curve. The time when the gantry reaches the angle specified by each control point can be acquired from the virtual inclinometer that is a feature of ArcCheck. The gantry speed between two consecutive control points is then calculated. The aforementioned dose rate is calculated from an acm file that is generated during ArcCheck measurements. This file stores the data measured by each detector in 50 ms updates with each update in a separate row. A computer program was written in MATLAB language to process the data. The program output included MLC positioning errors and the dose rate at each control point as well as the gantry speed between control points. To evaluate this method, this plan was delivered for four consecutive weeks. The actual dose rate and gantry speed were compared with the QA plan specified. Additionally, leaf positioning errors were intentionally introduced to investigate the sensitivity of this method. The relationship curves were established for detecting MLC positioning errors during VMAT delivery. For four consecutive weeks measured, 98.4%, 94.9%, 89.2%, and 91.0% of the leaf positioning errors were within ± 0.5 mm, respectively. For the intentionally introduced leaf positioning systematic errors of -0.5 and +1 mm, the detected leaf positioning errors of 20 Y1 leaf were -0.48 ± 0.14 and 1.02 ± 0.26 mm, respectively. The actual gantry speed and dose rate closely followed the values specified in the VMAT QA plan. This method can assess the accuracy of MLC positions and the dose rate at each control point as well as the gantry speed between control points at the same time. It is efficient and suitable for routine quality assurance of VMAT.

Leaf δ18O of remaining trees is affected by thinning intensity in a semiarid pine forest.

PubMed

Moreno-Gutiérrez, Cristina; Barberá, Gonzalo G; Nicolás, Emilio; DE Luis, Martín; Castillo, Víctor M; Martínez-Fernández, Faustino; Querejeta, José I

2011-06-01

Silvicultural thinning usually improves the water status of remaining trees in water-limited forests. We evaluated the usefulness of a dual stable isotope approach (δ¹³C, δ¹⁸O) for comparing the physiological performance of remaining trees between forest stands subjected to two different thinning intensities (moderate versus heavy) in a 60-year-old Pinus halepensis Mill. plantation in semiarid southeastern Spain. We measured bulk leaf δ¹³C and δ¹⁸O, foliar elemental concentrations, stem water content, stem water δ¹⁸O (δ¹⁸O(stem water)), tree ring widths and leaf gas exchange rates to assess the influence of forest stand density on tree performance. Remaining trees in low-density stands (heavily thinned) showed lower leaf δ¹⁸O, and higher stomatal conductance (g(s)), photosynthetic rate and radial growth than those in moderate-density stands (moderately thinned). By contrast, leaf δ¹³C, intrinsic water-use efficiency, foliar elemental concentrations and δ¹⁸O(stem water) were unaffected by stand density. Lower foliar δ¹⁸O in heavily thinned stands reflected higher g(s) of remaining trees due to decreased inter-tree competition for water, whereas higher photosynthetic rate was largely attributable to reduced stomatal limitation to CO₂ uptake. The dual isotope approach provided insight into the early (12 months) effects of stand density manipulation on the physiological performance of remaining trees. © 2011 Blackwell Publishing Ltd.

Arrhenius equation modeling for the shelf life prediction of tomato paste containing a natural preservative.

PubMed

Jafari, Seid Mahdi; Ganje, Mohammad; Dehnad, Danial; Ghanbari, Vahid; Hajitabar, Javad

2017-12-01

The shelf life of tomato paste with microencapsulated olive leaf extract was compared with that of samples containing a commercial preservative by accelerated shelf life testing. Based on previous studies showing that olive leaf extract as a rich source of phenolic compounds can have antimicrobial properties, application of its encapsulated form to improve the storage stability of tomato paste is proposed here. Regarding total soluble solids, the control and the sample containing 1000 µg g -1 sodium benzoate had the lowest (Q 10  = 1.63) and highest (Q 10  = 1.88) sensitivity to temperature changes respectively; also, the microencapsulated sample containing 1000 µg g -1 encapsulated olive leaf extract (Q 10  = 1.83) followed the sample containing 1000 µg g -1 sodium benzoate in terms of the highest kinetic rates. In the case of consistency, the lowest and highest activation energies (E a ) corresponded to samples containing 1000 µg g -1 non-encapsulated olive leaf extract and 1000 µg g -1 microencapsulated olive leaf extract respectively. Interestingly, samples containing microencapsulated olive leaf extract could maintain the original quality of the tomato paste very well, while those with non-encapsulated olive leaf extract rated the worst performance (among all specimens) in terms of maintaining their quality indices for a long time period. Overall, the shelf life equation was able to predict the consistency index of all tomato paste samples during long-time storage with high precision. © 2017 Society of Chemical Industry. © 2017 Society of Chemical Industry.

The winter-red-leaf syndrome in Pistacia lentiscus: evidence that the anthocyanic phenotype suffers from nitrogen deficiency, low carboxylation efficiency and high risk of photoinhibition.

PubMed

Nikiforou, Constantinos; Nikolopoulos, Dimosthenis; Manetas, Yiannis

2011-12-15

Recent evidence indicates that winter-red leaf phenotypes in the mastic tree (Pistacia lentiscus) are more vulnerable to chronic photoinhibition during the cold season relative to winter-green phenotypes occurring in the same high light environment. This was judged by limitations in the maximum quantum yield of photosystem II (PSII), found in previous studies. In this investigation, we asked whether corresponding limitations in leaf gas exchange and carboxylation reactions could also be manifested. During the cold ("red") season, net CO₂ assimilation rates (A) and stomatal conductances (g(s)) in the red phenotype were considerably lower than in the green phenotype, while leaf internal CO₂ concentration (Ci) was higher. The differences were abolished in the "green" period of the year, the dry summer included. Analysis of A versus Ci curves indicated that CO₂ assimilation during winter in the red phenotype was limited by Rubisco content and/or activity rather than stomatal conductance. Leaf nitrogen levels in the red phenotype were considerably lower during the red-leaf period. Consequently, we suggest that the inherently low leaf nitrogen levels are linked to the low net photosynthetic rates of the red plants through a decrease in Rubisco content. Accordingly, the reduced capacity of the carboxylation reactions to act as photosynthetic electron sinks may explain the corresponding loss of PSII photon trapping efficiency, which cannot be fully alleviated by the screening effect of the accumulated anthocyanins. Copyright © 2011 Elsevier GmbH. All rights reserved.

Water- and nitrogen-dependent alterations in the inheritance mode of transpiration efficiency in winter wheat at the leaf and whole-plant level.

PubMed

Ratajczak, Dominika; Górny, Andrzej G

2012-11-01

The effects of contrasting water and nitrogen (N) supply on the observed inheritance mode of transpiration efficiency (TE) at the flag-leaf and whole-season levels were examined in winter wheat. Major components of the photosynthetic capacity of leaves and the season-integrated efficiency of water use in vegetative and grain mass formation were evaluated in parental lines of various origins and their diallel F(2)-hybrids grown in a factorial experiment under different moisture and N status of the soil. A broad genetic variation was mainly found for the season-long TE measures. The variation range in the leaf photosynthetic indices was usually narrow, but tended to slightly enhance under water and N shortage. Genotype-treatment interaction effects were significant for most characters. No consistency between the leaf- and season-long TE measures was observed. Preponderance of additivity-dependent variance was mainly identified for the season-integrated TE and leaf CO(2) assimilation rate. Soil treatments exhibited considerable influence on the phenotypic expression of gene action for the residual leaf measures. The contribution of non-additive gene effects and degree of dominance tended to increase in water- and N-limited plants, especially for the leaf transpiration rate and stomatal conductance. The results indicate that promise exists to improve the season-integrated TE. However, selection for TE components should be prolonged for later hybrid generations to eliminate the masking of non-additive causes. Such evaluation among families grown under sub-optimal water and nitrogen supply seems to be the most promising strategy in winter wheat.

[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.

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.

Salinity and light interactively affect neotropical mangrove seedlings at the leaf and whole plant levels.

PubMed

López-Hoffman, Laura; Anten, Niels P R; Martínez-Ramos, Miguel; Ackerly, David D

2007-01-01

We have studied the interactive effects of salinity and light on Avicennia germinans mangrove seedlings in greenhouse and field experiments. We hypothesized that net photosynthesis, growth, and survivorship rates should increase more with an increase in light availability for plants growing at low salinity than for those growing at high salinity. This hypothesis was supported by our results for net photosynthesis and growth. Net daily photosynthesis did increase more with increasing light for low-salinity plants than for high-salinity plants. Stomatal conductance, leaf-level transpiration, and internal CO(2) concentrations were lower at high than at low salinity. At high light, the ratio of leaf respiration to assimilation was 2.5 times greater at high than at low salinity. Stomatal limitations and increased respiratory costs may explain why, at high salinity, seedlings did not respond to increased light availability with increased net photosynthesis. Seedling mass and growth rates increased more with increasing light availability at low than at high salinity. Ratios of root mass to leaf mass were higher at high salinity, suggesting that either water or nutrient limitations may have limited seedling growth at high salinity in response to increasing light. The interactive effects of salinity and light on seedling size and growth rates observed in the greenhouse were robust in the field, despite the presence of other factors in the field--such as inundation, nutrient gradients, and herbivory. In the field, seedling survivorship was higher at low than at high salinity and increased with light availability. Interestingly, the positive effect of light on seedling survivorship was stronger at high salinity, indicating that growth and survivorship rates are decoupled. In general, this study demonstrates that environmental effects at the leaf-level also influence whole plant growth in mangroves.

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.

Drought and detritivores determine leaf litter decomposition in calcareous streams of the Ebro catchment (Spain).

PubMed

Monroy, Silvia; Menéndez, Margarita; Basaguren, Ana; Pérez, Javier; Elosegi, Arturo; Pozo, Jesús

2016-12-15

Drought, an important environmental factor affecting the functioning of stream ecosystems, is likely to become more prevalent in the Mediterranean region as a consequence of climate change and enhanced water demand. Drought can have profound impacts on leaf litter decomposition, a key ecosystem process in headwater streams, but there is still limited information on its effects at the regional scale. We measured leaf litter decomposition across a gradient of aridity in the Ebro River basin. We deployed coarse- and fine-mesh bags with alder and oak leaves in 11 Mediterranean calcareous streams spanning a range of over 400km, and determined changes in discharge, water quality, leaf-associated macroinvertebrates, leaf quality and decomposition rates. The study streams were subject to different degrees of drought, specific discharge (Ls -1 km -2 ) ranging from 0.62 to 9.99. One of the streams dried out during the experiment, another one reached residual flow, whereas the rest registered uninterrupted flow but with different degrees of flow variability. Decomposition rates differed among sites, being lowest in the 2 most water-stressed sites, but showed no general correlation with specific discharge. Microbial decomposition rates were not correlated with final nutrient content of litter nor to fungal biomass. Total decomposition rate of alder was positively correlated to the density and biomass of shredders; that of oak was not. Shredder density in alder bags showed a positive relationship with specific discharge during the decomposition experiment. Overall, the results point to a complex pattern of litter decomposition at the regional scale, as drought affects decomposition directly by emersion of bags and indirectly by affecting the functional composition and density of detritivores. Copyright © 2016 The Authors. Published by Elsevier B.V. All rights reserved.

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.

[Characterization of kale (Brassica oberacea var acephala) under thallium stress by in situ attenuated total reflection FTIR].

PubMed

Yao, Yan; Zhang, Ping; Wang, Zhen-Chun; Chen, Yong-Heng

2009-01-01

The experiment was designed based on consumption of carbon dioxide through the photosynthesis of Brassica oberacea var acephala leaf, and the photosynthesis of kale leaf under thallium stress was investigated by in situ attenuated total reflection FTIR (in situ ATR-FTIR). The ATR-FTIR showed that the absorption peaks of leaves had no obvious difference between plants growing in thallium stress soil and plants growing in non-thallium pollution soil, and the strong peaks at 3,380 cm(-1) could be assigned to the absorption of water, carbohydrate, protein or amide; the strong peaks at 2,916 and 2,850 cm(-1) assigned to the absorption of carbohydrate or aliphatic compound; the peaks at 1,640 cm(-1) assigned to the absorption of water. However, as detected by the in situ ATR-FTIR, the double peaks (negative peaks) at 2,360 and 2,340 cm(-1) that are assigned to the absorption of CO2 appeared and became high gradually. It was showed that kale was carrying photosynthesis. At the same time, the carbon dioxide consumption speed of leaf under thallium stress was obviously larger than that of the blank It was expressed that photosynthesis under thallium stress was stronger than the blank All these represented that kale had certain tolerance to the heavy metal thallium. Meanwhile, the carbon dioxide consumption of grown-up leaf was more than that of young leaf whether or not under thallium stress. It was also indicated that the intensity of photosynthesis in grown-up leaf is higher than that in young leaf.

[Comparison study on total flavonoid content and anti-free redical activity of the leaves of bamboo, phyllostachys nigra, and Ginkgo bilabo].

PubMed

Zhang, Ying; Wu, Xiao-qing; Yu, Zuo-yu

2002-04-01

To investigate the differences of total flavonoid (TF) content and antifree radical activity between the-leaves of bamboo and Gingo biloba, as well as their seasonal changes. Spectrophotometery and Chemiluminescence methods were adopted to determine TF and half inhibiting concentration (IC50) on active oxygen free radicals of the leaves of bamboo, phyllostachys nigra (Lodd. ex. Lindl.) Munro, and Ginkgo biloba. Two kinds of leaves were picked in the same plot at the same time monthly. The TF of bamboo leaf varied in the range of 0.67%-1.71% (in dry basis of leaf, below as same) throughout a year, the minimum apparing in June and the maximum in July, then going down obviously, and remaining at a much high lever during November to next April. However, the TF of Ginkgo bilabo leaf varied in 1.48%-2.49% during whole growing period, early April to late November. It ascended with the growth of leaf, reaching the top during June and July, the going down slowly, and finally another peak appeared before defoliation. The average IC50 values on O2-. and .OH of bamboo leaf were at 11.0 micrograms.mL-1 and 5.3 mg.mL-1, and Ginkgo biloba at 19.0 micrograms.mL-1 and 3.6 mg.mL-1, respectively. The TF content and anti-free radical activity the bamboo leaf are comparable with the leaf of ginkgo biloba, which is a kind of potential resources for natural antioxidant and free radical scavenger.

Phytochemical, morphological, and biological investigations of propolis from Central Chile.

PubMed

Valcic, S; Montenegro, G; Mujica, A M; Avila, G; Franzblau, S; Singh, M P; Maiese, W M; Timmermann, B N

1999-01-01

Propolis from central Chile was investigated for its plant origin by microscopical analysis of pollen grains and leaf fragments found in the sample. The pollen grains that appear with significant higher frequency in the sample corresponded to four native and two introduced species, whereas leaf fragments corresponded to four native species. Seventeen phenolic compounds that belong to the phenylpropane, benzaldehyde, dihydrobenzofuran, or benzopyran classes, were isolated from an organic extract that was found to have a moderate growth inhibitory activity against Mycobacterium avium, M. tuberculosis, and two strains of Staphylococcus aureus. The components responsible for activity were determined.

Coupled carbon-water exchange of the Amazon rain forest, I. Model description, parameterization and sensitivity analysis

NASA Astrophysics Data System (ADS)

Simon, E.; Meixner, F. X.; Ganzeveld, L.; Kesselmeier, J.

2005-04-01

Detailed one-dimensional multilayer biosphere-atmosphere models, also referred to as CANVEG models, are used for more than a decade to describe coupled water-carbon exchange between the terrestrial vegetation and the lower atmosphere. Within the present study, a modified CANVEG scheme is described. A generic parameterization and characterization of biophysical properties of Amazon rain forest canopies is inferred using available field measurements of canopy structure, in-canopy profiles of horizontal wind speed and radiation, canopy albedo, soil heat flux and soil respiration, photosynthetic capacity and leaf nitrogen as well as leaf level enclosure measurements made on sunlit and shaded branches of several Amazonian tree species during the wet and dry season. The sensitivity of calculated canopy energy and CO2 fluxes to the uncertainty of individual parameter values is assessed. In the companion paper, the predicted seasonal exchange of energy, CO2, ozone and isoprene is compared to observations.

A bi-modal distribution of leaf area density with a total leaf area index of 6 is inferred from several observations in Amazonia. Predicted light attenuation within the canopy agrees reasonably well with observations made at different field sites. A comparison of predicted and observed canopy albedo shows a high model sensitivity to the leaf optical parameters for near-infrared short-wave radiation (NIR). The predictions agree much better with observations when the leaf reflectance and transmission coefficients for NIR are reduced by 25-40%. Available vertical distributions of photosynthetic capacity and leaf nitrogen concentration suggest a low but significant light acclimation of the rain forest canopy that scales nearly linearly with accumulated leaf area.

Evaluation of the biochemical leaf model, using the enclosure measurements, showed that recommended parameter values describing the photosynthetic light response, have to be optimized. Otherwise, predicted net assimilation is overestimated by 30-50%. Two stomatal models have been tested, which apply a well established semi-empirical relationship between stomatal conductance and net assimilation. Both models differ in the way they describe the influence of humidity on stomatal response. However, they show a very similar performance within the range of observed environmental conditions. The agreement between predicted and observed stomatal conductance rates is reasonable. In general, the leaf level data suggests seasonal physiological changes, which can be reproduced reasonably well by assuming increased stomatal conductance rates during the wet season, and decreased assimilation rates during the dry season.

The sensitivity of the predicted canopy fluxes of energy and CO2 to the parameterization of canopy structure, the leaf optical parameters, and the scaling of photosynthetic parameters is relatively low (1-12%), with respect to parameter uncertainty. In contrast, modifying leaf model parameters within their uncertainty range results in much larger changes of the predicted canopy net fluxes (5-35%).

Coupled carbon-water exchange of the Amazon rain forest, I. Model description, parameterization and sensitivity analysis

NASA Astrophysics Data System (ADS)

Simon, E.; Meixner, F. X.; Ganzeveld, L.; Kesselmeier, J.

2005-09-01

Detailed one-dimensional multilayer biosphere-atmosphere models, also referred to as CANVEG models, are used for more than a decade to describe coupled water-carbon exchange between the terrestrial vegetation and the lower atmosphere. Within the present study, a modified CANVEG scheme is described. A generic parameterization and characterization of biophysical properties of Amazon rain forest canopies is inferred using available field measurements of canopy structure, in-canopy profiles of horizontal wind speed and radiation, canopy albedo, soil heat flux and soil respiration, photosynthetic capacity and leaf nitrogen as well as leaf level enclosure measurements made on sunlit and shaded branches of several Amazonian tree species during the wet and dry season. The sensitivity of calculated canopy energy and CO2 fluxes to the uncertainty of individual parameter values is assessed. In the companion paper, the predicted seasonal exchange of energy, CO2, ozone and isoprene is compared to observations.

A bi-modal distribution of leaf area density with a total leaf area index of 6 is inferred from several observations in Amazonia. Predicted light attenuation within the canopy agrees reasonably well with observations made at different field sites. A comparison of predicted and observed canopy albedo shows a high model sensitivity to the leaf optical parameters for near-infrared short-wave radiation (NIR). The predictions agree much better with observations when the leaf reflectance and transmission coefficients for NIR are reduced by 25-40%. Available vertical distributions of photosynthetic capacity and leaf nitrogen concentration suggest a low but significant light acclimation of the rain forest canopy that scales nearly linearly with accumulated leaf area.

Evaluation of the biochemical leaf model, using the enclosure measurements, showed that recommended parameter values describing the photosynthetic light response, have to be optimized. Otherwise, predicted net assimilation is overestimated by 30-50%. Two stomatal models have been tested, which apply a well established semi-empirical relationship between stomatal conductance and net assimilation. Both models differ in the way they describe the influence of humidity on stomatal response. However, they show a very similar performance within the range of observed environmental conditions. The agreement between predicted and observed stomatal conductance rates is reasonable. In general, the leaf level data suggests seasonal physiological changes, which can be reproduced reasonably well by assuming increased stomatal conductance rates during the wet season, and decreased assimilation rates during the dry season.

The sensitivity of the predicted canopy fluxes of energy and CO2 to the parameterization of canopy structure, the leaf optical parameters, and the scaling of photosynthetic parameters is relatively low (1-12%), with respect to parameter uncertainty. In contrast, modifying leaf model parameters within their uncertainty range results in much larger changes of the predicted canopy net fluxes (5-35%).

Rating poplars for Melampsora leaf rust infection

Treesearch

Ernst J. Schreiner

1959-01-01

Melampsora leaf rust occurs in all countries where poplars are native or where they have been introduced for ornamental use or timber culture. The rust is easily recognized by the bright orange-yellow spore masses on the undersides of the leaves during most of the growing season.

Factors controlling plasticity of leaf morphology in Robinia pseudoacacia: III. biophysical constraints on leaf expansion under long-term water stress

Treesearch

Yanxiang ​Zhang; Maria Alejandra Equiza; Quanshui Zheng; Melvin T. Tyree

2011-01-01

In this article, we measured the relative growth rate (RGR) of leaves of Robinia pseudoacacia seedlings under well-watered and water-stressed conditions (mid-day Ψw = leaf water potential estimated with a pressure bomb of −0.48 and −0.98 MPa, respectively). Pressure–volume (PV) curves were done on growing leaves at 25, 50 and 95% of the mature size...

Inhibitor of striate conditionally suppresses cell proliferation in variegated maize

PubMed Central

Park, Sung Han; Park, Su Hyun; Chin, Hang Gyeong; Cho, Moo Je; Martienssen, Robert A.; Han, Chang-deok

2000-01-01

Since the work done by R.A. Emerson in the 1930s, Inhibitor of striate (Isr) has been recognized as a dose-dependent genetic modifier of variegation in chlorotic leaf striping mutants of maize such as striate2 (sr2). We have shown that Isr specifically inhibits proliferation and differentiation of plastid defective cells in sr2 mutants. Leaf narrowing is due to loss of intermediate veins and ground tissue located at leaf margins, and the few remaining plastid defective cells are of irregular size and aberrant organization. The Isr gene has been cloned by targeted transposon tagging. Isr mRNA is expressed throughout young leaves, but Isr chimeras indicate that the expression of Isr at leaf margins is sufficient to suppress both the lateral expansion of sr2 leaves and the extent of striping. Isr protein appears to encode a chloroplast protein with sequence similarity to a family of bacterial phosphatases involved in carbon catabolite repression or in carbon metabolism. We propose that the action of Isr in nuclear and plastid communication could be triggered by carbon stress. PMID:10783171

Diel time-courses of leaf growth in monocot and dicot species: endogenous rhythms and temperature effects.

PubMed

Poiré, Richard; Wiese-Klinkenberg, Anika; Parent, Boris; Mielewczik, Michael; Schurr, Ulrich; Tardieu, François; Walter, Achim

2010-06-01

Diel (24 h) leaf growth patterns were differently affected by temperature variations and the circadian clock in several plant species. In the monocotyledon Zea mays, leaf elongation rate closely followed changes in temperature. In the dicotyledons Nicotiana tabacum, Ricinus communis, and Flaveria bidentis, the effect of temperature regimes was less obvious and leaf growth exhibited a clear circadian oscillation. These differences were related neither to primary metabolism nor to altered carbohydrate availability for growth. The effect of endogenous rhythms on leaf growth was analysed under continuous light in Arabidopsis thaliana, Ricinus communis, Zea mays, and Oryza sativa. No rhythmic growth was observed under continuous light in the two monocotyledons, while growth rhythmicity persisted in the two dicotyledons. Based on model simulations it is concluded that diel leaf growth patterns in mono- and dicotyledons result from the additive effects of both circadian-clock-controlled processes and responses to environmental changes such as temperature and evaporative demand. Apparently very distinct diel leaf growth behaviour of monocotyledons and dicotyledons can thus be explained by the different degrees to which diel temperature variations affect leaf growth in the two groups of species which, in turn, depends on the extent of the leaf growth control by internal clocks.

Quality improvement by batch vacuum distillation and physicochemical characterization of clove leaf oil in Central Java, Indonesia

NASA Astrophysics Data System (ADS)

Alighiri, D.; Eden, W. T.; Cahyono, E.; Supardi, K. I.

2018-03-01

Clove leaf oil is one of the essential oils which have high economic value and produced in considerable amount in Indonesia. As many as 60% of clove oil produced by Indonesia has exported to many countries in the world. Musuk and Ringinlarik Village, Boyolali District, Central Java Province is one of the areas in Indonesia which became the primary supplier of Indonesian clove leaf oil. Although, the quality of the resulting yield is still low because it uses a simple distillation kettle in the form of the iron plate or used the drum. The clove leaf oil produced by steam distillation from the dry whole leaves of the clove tree. The color of the oil is brownish black and dirty with the odor are fresh distilled, spicy, warm, and terpenic. The specific gravity at 25 °C of 1.529, the refractive index at 20 °C of 1.030, and based on GC-MS analysis, eugenol levels only 68% and caryophyllene is too high, i.e., 20%. The quality of clove leaf oil produced does not meet the specifications of international market standards. This work aimed to improve the quality of Indonesian clove leaf oil. The purifications done in this research was used by batch vacuum distillation with mode operation at vacuum -76 cmHg and reflux ratios 5:1. Clove leaf oil produced by using this method has a better physicochemical characterization, i.e., the appearance that is yellow to pale color with the odor is spicy, woody, warm, and terpenic. The specific gravity at 25 °C of 1.533, the refractive index at 20 °C of 1.038, and eugenol and caryophyllene contents has yielded 80.58% and 10%, respectively. By The enhancement quality of clove leaf oil by batch vacuum distillation, these oil is already meet international standards and income of clove leaf oil grower in Musuk and Ringinlarik Village, Boyolali District, Central Java Province, Indonesia could be increased.

An Evaluation of Frankliniella occidentalis (Thysanoptera: Thripidae) and Frankliniella intonsa (Thysanoptera: Thripidae) Performance on Different Plant Leaves Based on Life History Characteristics

PubMed Central

Li, Wei-Di; Zhang, Peng-Jun; Zhang, Jing-Ming; Zhang, Zhi-Jun; Huang, Fang; Bei, Ya-Wei; Lin, Wen-Cai; Lu, Yao-Bin

2015-01-01

To compare the performance of Frankliniella occidentalis (Pergande) and native Frankliniella intonsa (Trybom) on cucumber and tomato leaves in laboratory, life history characters were investigated, and life tables were constructed using the method of age-stage, two-sex table life. Compared with tomato leaf, there were shorter total preoviposition period (TPOP), higher fecundity, longer female longevity, and higher intrinsic rate of increase (r) of both F. occidentalis and F. intonsa on cucumber leaf. Meanwhile, on cucumber leaf, the shorter TPOP, higher fecundity, longer female longevity, and higher value of r were found on population of F. intonsa but on tomato leaf which were found on population of F. occidentalis. From above, cucumber leaf was the preference to population development of both F. occidentalis and F. intonsa compared with tomato leaf. Nevertheless, on cucumber leaf, population of F. intonsa would grow faster than that of F. occidentalis, which was the opposite on tomato leaf. As to the population development in fields, much more factors would be taken into account, such as pollen, insecticide resistance, and effects of natural enemies etc. PMID:25673049

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.

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.

[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.

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.

Reduction of Cr(VI) to Cr(III) by wetland plants: Potential for in situ heavy metal detoxification

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

Lytle, C.M.; Qian, J.H.; Hansen, D.

1998-10-15

Reduction of heavy metals in situ by plants may be a useful detoxification mechanism for phytoremediation. Using X-ray spectroscopy, the authors show that Eichhornia crassipes (water hyacinth), supplied with Cr(VI) in nutrient culture, accumulated nontoxic Cr(III) in root and shoot tissues. The reduction of Cr(VI) to Cr(III) appeared to occur in the fine lateral roots. The Cr(III) was subsequently translocated to leaf tissues. Extended X-ray absorption fine structure of Cr in leaf and petiole differed when compared to Cr in roots. In roots, Cr(III) was hydrated by water, but in petiole and more so in leaf, a portion of themore » Cr(III) may be bound to oxalate ligands. This suggests that E. crassipes detoxified Cr(VI) upon root uptake and transported a portion of the detoxified Cr to leaf tissues. Cr-rich crystalline structures were observed on the leaf surface. The chemical species of Cr in other plants, collected from wetlands that contained Cr(VI)-contaminated wastewater, was also found to be Cr(III). The authors propose that this plant-based reduction of Cr(VI) by E. crassipes has the potential to be used for the in situ detoxification of Cr(VI)-contaminated wastestreams.« less

Intra-plant variation in cyanogenesis and the continuum of foliar plant defense traits in the rainforest tree Ryparosa kurrangii (Achariaceae).

PubMed

Webber, Bruce L; Woodrow, Ian E

2008-06-01

At the intra-plant level, temporal and spatial variations in plant defense traits can be influenced by resource requirements, defensive priorities and storage opportunities. Across a leaf age gradient, cyanogenic glycoside concentrations in the rainforest understory tree Ryparosa kurrangii B.L. Webber were higher in young expanding leaves than in mature leaves (2.58 and 1.38 mg g(-1), respectively). Moreover, cyanogens, as an effective chemical defense against generalist herbivores, contributed to a defense continuum protecting foliar tissue during leaf development. Chemical (cyanogens and phenolic compounds) and phenological (delayed greening) defense traits protected young leaves, whereas mature leaves were largely protected by physical defense mechanisms (lamina toughness; explained primarily by leaf mass per area). Cyanogen concentration was considerably higher in floral tissue than in foliar tissue and decreased in floral tissue during development. Across contrasting tropical seasons, foliar cyanogenic concentration varied significantly, being highest in the late wet season and lowest during the pre-wet season, the latter coinciding with fruiting and leaf flushing. Cyanogens in R. kurrangii appear to be differentially allocated in a way that maximizes plant fitness but may also act as a store of reduced nitrogen that is remobilized during flowering and leaf flushing.

Ginkgo biloba leaf extract induces DNA damage by inhibiting topoisomerase II activity in human hepatic cells.

PubMed

Zhang, Zhuhong; Chen, Si; Mei, Hu; Xuan, Jiekun; Guo, Xiaoqing; Couch, Letha; Dobrovolsky, Vasily N; Guo, Lei; Mei, Nan

2015-09-30

Ginkgo biloba leaf extract has been shown to increase the incidence in liver tumors in mice in a 2-year bioassay conducted by the National Toxicology Program. In this study, the DNA damaging effects of Ginkgo biloba leaf extract and many of its constituents were evaluated in human hepatic HepG2 cells and the underlying mechanism was determined. A molecular docking study revealed that quercetin, a flavonoid constituent of Ginkgo biloba, showed a higher potential to interact with topoisomerase II (Topo II) than did the other Ginkgo biloba constituents; this in silico prediction was confirmed by using a biochemical assay to study Topo II enzyme inhibition. Moreover, as measured by the Comet assay and the induction of γ-H2A.X, quercetin, followed by keampferol and isorhamnetin, appeared to be the most potent DNA damage inducer in HepG2 cells. In Topo II knockdown cells, DNA damage triggered by Ginkgo biloba leaf extract or quercetin was dramatically decreased, indicating that DNA damage is directly associated with Topo II. DNA damage was also observed when cells were treated with commercially available Ginkgo biloba extract product. Our findings suggest that Ginkgo biloba leaf extract- and quercetin-induced in vitro genotoxicity may be the result of Topo II inhibition.

Ginkgo biloba leaf extract induces DNA damage by inhibiting topoisomerase II activity in human hepatic cells

PubMed Central

Zhang, Zhuhong; Chen, Si; Mei, Hu; Xuan, Jiekun; Guo, Xiaoqing; Couch, Letha; Dobrovolsky, Vasily N.; Guo, Lei; Mei, Nan

2015-01-01

Ginkgo biloba leaf extract has been shown to increase the incidence in liver tumors in mice in a 2-year bioassay conducted by the National Toxicology Program. In this study, the DNA damaging effects of Ginkgo biloba leaf extract and many of its constituents were evaluated in human hepatic HepG2 cells and the underlying mechanism was determined. A molecular docking study revealed that quercetin, a flavonoid constituent of Ginkgo biloba, showed a higher potential to interact with topoisomerase II (Topo II) than did the other Ginkgo biloba constituents; this in silico prediction was confirmed by using a biochemical assay to study Topo II enzyme inhibition. Moreover, as measured by the Comet assay and the induction of γ-H2A.X, quercetin, followed by keampferol and isorhamnetin, appeared to be the most potent DNA damage inducer in HepG2 cells. In Topo II knockdown cells, DNA damage triggered by Ginkgo biloba leaf extract or quercetin was dramatically decreased, indicating that DNA damage is directly associated with Topo II. DNA damage was also observed when cells were treated with commercially available Ginkgo biloba extract product. Our findings suggest that Ginkgo biloba leaf extract- and quercetin-induced in vitro genotoxicity may be the result of Topo II inhibition. PMID:26419945

Identification of a disease complex involving a novel monopartite begomovirus with beta- and alphasatellites associated with okra leaf curl disease in Oman.

PubMed

Akhtar, Sohail; Khan, Akhtar J; Singh, Achuit S; Briddon, Rob W

2014-05-01

Okra leaf curl disease (OLCD) is an important viral disease of okra in tropical and subtropical areas. The disease is caused by begomovirus-satellite complexes. A begomovirus and associated betasatellite and alphasatellite were identified in symptomatic okra plants from Barka, in the Al-Batinah region of Oman. Analysis of the begomovirus sequences showed them to represent a new begomovirus most closely related to cotton leaf curl Gezira virus (CLCuGeV), a begomovirus of African origin. The sequences showed less than 85 % nucleotide sequence identity to CLCuGeV isolates. The name okra leaf curl Oman virus (OLCOMV) is proposed for the new virus. Further analysis revealed that the OLCOMV is a recombinant begomovirus that evolved by the recombination of CLCuGeV isolates with tomato yellow leaf curl virus-Oman (TYLCV-OM). An alpha- and a betasatellite were also identified from the same plant sample, which were also unique when compared to sequences available in the databases. However, although the betasatellite appeared to be of African origin, the alphasatellite was most closely related to alphasatellites originating from South Asia. This is the first report of a begomovirus-satellite complex infecting okra in Oman.

Tuning Transpiration by Interfacial Solar Absorber‐Leaf Engineering

PubMed Central

Zhuang, Shendong; Zhou, Lin; Xu, Weichao; Xu, Ning; Hu, Xiaozhen; Li, Xiuqiang; Lv, Guangxin; Zheng, Qinghui; Zhu, Shining

2017-01-01

Abstract Plant transpiration, a process of water movement through a plant and its evaporation from aerial parts especially leaves, consumes a large component of the total continental precipitation (≈48%) and significantly influences global water distribution and climate. To date, various chemical and/or biological explorations have been made to tune the transpiration but with uncertain environmental risks. In recent years, interfacial solar steam/vapor generation is attracting a lot of attention for achieving high energy transfer efficiency. Various optical and thermal designs at the solar absorber–water interface for potential applications in water purification, seawater desalination, and power generation appear. In this work, the concept of interfacial solar vapor generation is extended to tunable plant transpiration by showing for the first time that the transpiration efficiency can also be enhanced or suppressed through engineering the solar absorber–leaf interface. By tuning the solar absorption of membrane in direct touch with green leaf, surface temperature of green leaf will change accordingly because of photothermal effect, thus the transpiration efficiency as well as temperature and relative humidity in the surrounding environment will be tuned. This tunable transpiration by interfacial absorber‐leaf engineering can open an alternative avenue to regulate local atmospheric temperature, humidity, and eventually hydrologic cycle. PMID:29619300

[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.

Effects of forest management practices in temperate beech forests on bacterial and fungal communities involved in leaf litter degradation.

PubMed

Purahong, Witoon; Kapturska, Danuta; Pecyna, Marek J; Jariyavidyanont, Katalee; Kaunzner, Jennifer; Juncheed, Kantida; Uengwetwanit, Tanaporn; Rudloff, Renate; Schulz, Elke; Hofrichter, Martin; Schloter, Michael; Krüger, Dirk; Buscot, François

2015-05-01

Forest management practices (FMPs) significantly influence important ecological processes and services in Central European forests, such as leaf litter decomposition and nutrient cycling. Changes in leaf litter diversity, and thus, its quality as well as microbial community structure and function induced by different FMPs were hypothesized to be the main drivers causing shifts in decomposition rates and nutrient release in managed forests. In a litterbag experiment lasting 473 days, we aimed to investigate the effects of FMPs (even-aged timber management, selective logging and unmanaged) on bacterial and fungal communities involved in leaf litter degradation over time. Our results showed that microbial communities in leaf litter were strongly influenced by both FMPs and sampling date. The results from nonmetric multidimensional scaling (NMDS) ordination revealed distinct patterns of bacterial and fungal successions over time in leaf litter. We demonstrated that FMPs and sampling dates can influence a range of factors, including leaf litter quality, microbial macronutrients, and pH, which significantly correlate with microbial community successions.

KINETICS OF LEAF TEMPERATURE FLUCTUATION AFFECT ISOPRENE EMISSION FROM RED OAK (QUERCUS RUBRA) LEAVES

EPA Science Inventory

Because the rate of isoprene (2-methyl-1,3-butadiene) emission from plants is highly temperature-dependent, we investigated the natural fluctuations on leaf temperature and the effects of rapid temperature change on isoprene emission of red oak (Quercus rubra L.) leaves at the to...

Structure and vascular tissue expression of duplicated TERMINAL EAR1-like paralogues in poplar.

PubMed

Charon, Céline; Vivancos, Julien; Mazubert, Christelle; Paquet, Nicolas; Pilate, Gilles; Dron, Michel

2010-02-01

TERMINAL EAR1-like (TEL) genes encode putative RNA-binding proteins only found in land plants. Previous studies suggested that they may regulate tissue and organ initiation in Poaceae. Two TEL genes were identified in both Populus trichocarpa and the hybrid aspen Populus tremula x P. alba, named, respectively, PoptrTEL1-2 and PtaTEL1-2. The analysis of the organisation around the PoptrTEL genes in the P. trichocarpa genome and the estimation of the synonymous substitution rate for PtaTEL1-2 genes indicate that the paralogous link between these two Populus TEL genes probably results from the Salicoid large-scale gene-duplication event. Phylogenetic analyses confirmed their orthology link with the other TEL genes. The expression pattern of both PtaTEL genes appeared to be restricted to the mother cells of the plant body: leaf founder cells, leaf primordia, axillary buds and root differentiating tissues, as well as to mother cells of vascular tissues. Most interestingly, PtaTEL1-2 transcripts were found in differentiating cells of secondary xylem and phloem, but probably not in the cambium itself. Taken together, these results indicate specific expression of the TEL genes in differentiating cells controlling tissue and organ development in Populus (and other Angiosperm species).

Water relations of coast redwood planted in the semi-arid climate of southern California.

PubMed

Litvak, Elizaveta; McCarthy, Heather R; Pataki, Diane E

2011-08-01

Trees planted in urban landscapes in southern California are often exposed to an unusual combination of high atmospheric evaporative demand and moist soil conditions caused by irrigation. The water relations of species transplanted into these conditions are uncertain. We investigated the water relations of coast redwood (Sequoia sempervirens) planted in the urbanized semi-arid Los Angeles Basin, where it often experiences leaf chlorosis and senescence. We measured the sap flux (J(O)) and hydraulic properties of irrigated trees at three sites in the Los Angeles region. We observed relatively strong stomatal regulation in response to atmospheric vapour pressure deficit (D; J(O) saturated at D < 1 kPa), and a linear response of J(O) to photosynthetically active radiation. Total tree water use by coast redwood was relatively low, with plot-level transpiration rates below 1 mm d(-1) . There was some evidence of xylem cavitation during the summer, which appeared to be reversed in fall and early winter. We conclude that water stress was not a direct factor in causing leaf chlorosis and senescence as has been proposed. Instead, the relatively strong stomatal control that is adaptive in the native habitat of coast redwood may lead to carbon limitation and other stresses in semi-arid, irrigated habitats. © 2011 Blackwell Publishing Ltd.

Nutrient content of young cassava leaves and assessment of their acceptance as a green vegetable in Nigeria.

PubMed

Awoyinka, A F; Abegunde, V O; Adewusi, S R

1995-01-01

Cassava (Manihot esculenta Crantz) leaves contained a high level of crude protein (29.3-32.4% dry weight) compared to a conventional vegetable, Amaranthus (19.6%). Ash was 4.6-6.4% in cassava leaf samples but 13.1% dry weight in Amaranthus. Dietary fibre was very high in all samples (26.9-39% dry weight) while HCN-potential was low (5.1-12.6 mg/100 g dry weight). Tannin was the highest in IITA red cassava leaves (29.7 mg/g) and the lowest in Amaranthus vegetable. In vitro digestibility was very low in oven dried samples (15.6-22.7%). Blanching increased protein content (except Amaranthus) and in vitro protein digestibility but decreased ash, minerals, dietary fibre and tannin, while HCN-potential was unchanged. Grinding reduced both HCN-potential and tannin by 84 and 71% respectively while oven drying only reduced the HCN content marginally. Preference studies showed that the highest percentage of respondents (25.3%) preferred Amaranthus vegetable, followed by Celosia (17.5%), Talinum (12.4%), garden egg (11.5%), with cassava leaves as the least (0.5%). Organoleptic evaluation rated cassava leaf soup inferior to Amaranthus in terms of appearance, colour and texture but equal in terms of taste and flavour and overall acceptability.

Effects of root-zone acidity on utilization of nitrate and ammonium in tobacco plants

NASA Technical Reports Server (NTRS)

Henry, L. T.; Raper, C. D. Jr; Raper CD, J. r. (Principal Investigator)

1989-01-01

Tobacco (Nicotiana tabacum L., cv. 'Coker 319') plants were grown for 28 days in flowing nutrient culture containing either 1.0 mM NO3- or 1.0 mM NH4+ as the nitrogen source in a complete nutrient solution. Acidities of the solutions were controlled at pH 6.0 or 4.0 for each nitrogen source. Plants were sampled at intervals of 6 to 8 days for determination of dry matter and nitrogen accumulation. Specific rates of NO3- or NH4+ uptake (rate of uptake per unit root mass) were calculated from these data. Net photosynthetic rates per unit leaf area were measured on attached leaves by infrared gas analysis. When NO3- [correction of NO-] was the sole nitrogen source, root growth and nitrogen uptake rate were unaffected by pH of the solution, and photosynthetic activity of leaves and accumulation of dry matter and nitrogen in the whole plant were similar. When NH4+ was the nitrogen source, photosynthetic rate of leaves and accumulation of dry matter and nitrogen in the whole plant were not statistically different from NO3(-) -fed plants when acidity of the solution was controlled at pH 6.0. When acidity for NH4(+) -fed plants was increased to pH 4.0, however, specific rate of NH4+ uptake decreased by about 50% within the first 6 days of treatment. The effect of acidity on root function was associated with a decreased rate of accumulation of nitrogen in shoots that was accompanied by a rapid cessation of leaf development between days 6 and 13. The decline in leaf growth rate of NH4(+) -fed plants at pH 4.0 was followed by reductions in photosynthetic rate per unit leaf area. These responses of NH4(+) -fed plants to increased root-zone acidity are characteristic of the sequence of responses that occur during onset of nitrogen stress.

Trade-offs between light interception and leaf water shedding: a comparison of shade- and sun-adapted species in a subtropical rainforest.

PubMed

Meng, Fengqun; Cao, Rui; Yang, Dongmei; Niklas, Karl J; Sun, Shucun

2014-01-01

Species in high-rainfall regions have two major alternative approaches to quickly drain off water, i.e., increasing leaf inclination angles relative to the horizontal plane, or developing long leaf drip tips. We hypothesized that shade-adapted species will have more pronounced leaf drip tips but not greater inclination angles (which can reduce the ability to intercept light) compared to sun-adapted species and that length of leaf drip tips will be negatively correlated with photosynthetic capacity [characterized by light-saturated net photosynthetic rates (Amax), associated light compensation points (LCP), and light saturation points (LSP)]. We tested this hypothesis by measuring morphological and physiological traits that are associated with light-interception and water shedding for seven shade-adapted shrub species, ten sun-adapted understory shrub species, and 15 sun-adapted tree species in a subtropical Chinese rainforest, where mean annual precipitation is around 1,600 mm. Shade-adapted understory species had lower LMA, Amax, LSP, and LCP compared to understory or canopy sun-adapted species; their leaf and twig inclination angles were significantly smaller and leaf drip tips were significantly longer than those in sun-adapted species. This suggests that shade-adapted understory species tend to develop pronounced leaf drip tips but not large leaf inclination angles to shed water. The length of leaf drip tips was negatively correlated with leaf inclination angles and photosynthetic capacity. These relationships were consistent between ordinary regression and phylogenetic generalized least squares analyses. Our study illustrates the trade-offs between light interception and leaf water shedding and indicates that length of leaf drip tips can be used as an indicator of adaptation to shady conditions and overall photosynthetic performance of shrub species in subtropical rainforests.

Effects of increasing air temperature on leaf phenology and photosynthetic characteristics in cool-temperate deciduous canopy trees.

NASA Astrophysics Data System (ADS)

Muraoka, H.; Nagao, A.; Saitoh, T. M.

2016-12-01

Influences of global warming have been observed or predicted in deciduous forest ecosystems in temperate regions. One of the remarkable changes can be hound in phenology, i.e., seasonality of canopy. Timing and growth rate of leaf expansion (morphological and physiological development), timing and rate of leaf senescence, and timing of leaf fall, and resulting length of photosynthetically active period, are the phenological events that have been focused over wide range of research from single leaf measurements at long-term research sites to satellite remote sensing at continental scales. These phenological changes under global warming have been predicted to influence carbon sequestration as a balance of photosynthesis and respiration. However, we still lack ecophysiological evidence and understandings on such phenological changes, to ask (1) do the phenological changes occur in both leaf morphology and physiology?, (2) does the leaf photosynthetic capacity change by warming?, and (3) do different tree species inhabiting in the same forest respond in a same way?In order to examine these questions, we conducted an open-warming experiments on foliage of matured canopy trees in a cool-temperate deciduous broadleaf forest in central Japan. Warming treatment was made by open-top canopy chambers with 1.5m W x 2m L x 1.8m H. The chamber was made of transparent acrylic boards and vinyl sheet. Three sunlit branches (1-2m) of Quercus crispula (16m height) and one sunlit branch (1m) of Betula ermanii (18m height) were examined at 15m above ground, since 2011 for Quercus and 2013 for Betula. The chambers increased mean daytime air temperature by about 1.5 degreeC.Artificial warming led earlier leaf expansion by about 3 days in Quercus during 2013-2015 and 2 days in Betula, and delayed leaf fall by 2-7 days and 2-3 days in Quercus and Betula, respectively. Quercus leaves showed clear influence of warming: higher seasonal growth, higher capacity and slower senescence of leaf photosynthetic capacity. Although the leaf expansion was stimulated by warming, its relationship with cumulative temperature from spring was consistent with leaves under ambient conditions. Our simple estimation showed that the warming treatment would might increase photosynthetic productivity by 14-21% in Quercus, but not in Betula.

Functional Inactivation of Putative Photosynthetic Electron Acceptor Ferredoxin C2 (FdC2) Induces Delayed Heading Date and Decreased Photosynthetic Rate in Rice

PubMed Central

Ruan, Banpu; Kang, Shujing; He, Lei; Zhang, Sen; Dong, Guojun; Hu, Jiang; Zeng, Dali; Zhang, Guangheng; Gao, Zhenyu; Ren, Deyong; Hu, Xingming; Chen, Guang; Guo, Longbiao; Qian, Qian; Zhu, Li

2015-01-01

Ferredoxin (Fd) protein as unique electron acceptor, involved in a variety of fundamental metabolic and signaling processes, which is indispensable for plant growth. The molecular mechanisms of Fd such as regulation of electron partitioning, impact of photosynthetic rate and involvement in the carbon fixing remain elusive in rice. Here we reported a heading date delay and yellowish leaf 1 (hdy1) mutant derived from Japonica rice cultivar “Nipponbare” subjected to EMS treatment. In the paddy field, the hdy1 mutant appeared at a significantly late heading date and had yellow-green leaves during the whole growth stage. Further investigation indicated that the abnormal phenotype of hdy1 was connected with depressed pigment content and photosynthetic rate. Genetic analysis results showed that the hdy1 mutant phenotype was caused by a single recessive nuclear gene mutation. Map-based cloning revealed that OsHDY1 is located on chromosome 3 and encodes an ortholog of the AtFdC2 gene. Complementation and overexpression, transgenic plants exhibited the mutant phenotype including head date, leaf color and the transcription levels of the FdC2 were completely rescued by transformation with OsHDY1. Real-time PCR revealed that the expression product of OsHDY1 was detected in almost all of the organs except root, whereas highest expression levels were observed in seeding new leaves. The lower expression levels of HDY1 and content of iron were detected in hdy1 than WT’s. The FdC2::GFP was detected in the chloroplasts of rice. Real-time PCR results showed that the expression of many photosynthetic electron transfer related genes in hdy1 were higher than WT. Our results suggest that OsFdC2 plays an important role in photosynthetic rate and development of heading date by regulating electron transfer and chlorophyll content in rice. PMID:26598971

Non-target effects on aquatic decomposer organisms of imidacloprid as a systemic insecticide to control emerald ash borer in riparian trees.

PubMed

Kreutzweiser, David; Good, Kevin; Chartrand, Derek; Scarr, Taylor; Thompson, Dean

2007-11-01

Imidacloprid is effective against emerald ash borer when applied as a systemic insecticide. Following stem or soil injections to trees in riparian areas, imidacloprid residues could be indirectly introduced to aquatic systems via leaf fall or leaching. Either route of exposure may affect non-target, aquatic decomposer organisms. Leaves from ash trees treated with imidacloprid at two field rates and an intentionally-high concentration were added to aquatic microcosms. Leaves from trees treated at the two field rates contained imidacloprid concentrations of 0.8-1.3 ppm, and did not significantly affect leaf-shredding insect survival, microbial respiration or microbial decomposition rates. Insect feeding rates were significantly inhibited at foliar concentrations of 1.3 ppm but not at 0.8 ppm. Leaves from intentionally high-dose trees contained concentrations of about 80 ppm, and resulted in 89-91% mortality of leaf-shredding insects, but no adverse effects on microbial respiration and decomposition rates. Imidacloprid applied directly to aquatic microcosms to simulate leaching from soils was at least 10 times more toxic to aquatic insects than the foliar concentrations, with high mortality at 0.13 ppm and significant feeding inhibition at 0.012 ppm.

Insect herbivory in a mature Eucalyptus woodland canopy depends on leaf phenology but not CO2 enrichment.

PubMed

Gherlenda, Andrew N; Moore, Ben D; Haigh, Anthony M; Johnson, Scott N; Riegler, Markus

2016-10-19

Climate change factors such as elevated atmospheric carbon dioxide concentrations (e[CO 2 ]) and altered rainfall patterns can alter leaf composition and phenology. This may subsequently impact insect herbivory. In sclerophyllous forests insects have developed strategies, such as preferentially feeding on new leaf growth, to overcome physical or foliar nitrogen constraints, and this may shift under climate change. Few studies of insect herbivory at elevated [CO 2 ] have occurred under field conditions and none on mature evergreen trees in a naturally established forest, yet estimates for leaf area loss due to herbivory are required in order to allow accurate predictions of plant productivity in future climates. Here, we assessed herbivory in the upper canopy of mature Eucalyptus tereticornis trees at the nutrient-limited Eucalyptus free-air CO 2 enrichment (EucFACE) experiment during the first 19 months of CO 2 enrichment. The assessment of herbivory extended over two consecutive spring-summer periods, with a first survey during four months of the [CO 2 ] ramp-up phase after which full [CO 2 ] operation was maintained, followed by a second survey period from months 13 to 19. Throughout the first 2 years of EucFACE, young, expanding leaves sustained significantly greater damage from insect herbivory (between 25 and 32 % leaf area loss) compared to old or fully expanded leaves (less than 2 % leaf area loss). This preference of insect herbivores for young expanding leaves combined with discontinuous production of new foliage, which occurred in response to rainfall, resulted in monthly variations in leaf herbivory. In contrast to the significant effects of rainfall-driven leaf phenology, elevated [CO 2 ] had no effect on leaf consumption or preference of insect herbivores for different leaf age classes. In the studied nutrient-limited natural Eucalyptus woodland, herbivory contributes to a significant loss of young foliage. Leaf phenology is a significant factor that determines the level of herbivory experienced in this evergreen sclerophyllous woodland system, and may therefore also influence the population dynamics of insect herbivores. Furthermore, leaf phenology appears more strongly impacted by rainfall patterns than by e[CO 2 ]. e[CO 2 ] responses of herbivores on mature trees may only become apparent after extensive CO 2 fumigation periods.

[Community types, phenology and propagation characteristics of Taxus mairei in north Guangdong].

PubMed

Liao, Wenbo; Zhang, Zhiqian; Chen, Zhiming; Tang, Changgen; Deng, Shifu

2002-07-01

Community types, phenology and propagation characteristics of Taxus mairei in north Guangdong were studied. The results showed that in north Guangdong province, Taxus mairei mainly distributed in the typical ever-green broad-leaf forest of lower and mid-subtropics dispersedly. Terminal bud of Taxus mairei was formed in late October and begun to grow foliages in mid-April, male flower bud was appeared in mid-May and the efflorescence was from late July to late November, female flower bud was formed in late August and the efflorescence was from late October to late January of second year, and the fruit mature period was in early October of second year. Under natural condition, the seed germination needed 2-3 years. Under experimental condition, the germination rate could be up to 82.2%. The effect of cuttage was better by taking mature annual twig and pretreatment by ABT1(100 mg.L-1) from October to November every year, and the rooting rate could be up to 95%.

Colour cues for leaf food selection by long-tailed macaques (Macaca fascicularis) with a new suggestion for the evolution of trichromatic colour vision.

PubMed

Lucas, P W; Darvell, B W; Lee, P K; Yuen, T D; Choong, M F

1998-01-01

Leaf colour, size and toughness were investigated in five plant species important in the diet of Macaca fascicularis in Singapore. Leaf colour and size were examined as potential visual cues for food selection, whereas toughness mirrored fibre content, the inverse of food quality. As leaves matured, they changed colour and toughened. Leaf lightness and yellowness were strongly negatively correlated with toughness, but variation in both the red-green axis of the CIE Lab colour space and leaf size were not. Leaves selected as food by the macaques were distinguished by being very light, yellow to slightly green. Some leaves were dappled with red. The literature suggests that these leaves are relatively rich in protein without being tough and therefore would be sought after by primates. We argue that leaf colour is an important indicator of the nutritive value of leaves. Trichromatic vision is an important advantage in finding those palatable leaves that are dappled red. These would appear dark to dichromatic primates and be deceptive by making leaves look older (lower in quality) than they actually are. This would decrease the perceived window of feeding opportunity for such primates who would be at a disadvantage in trying to find these leaves. It is possible that trichromatic vision in catarrhine primates may have originally evolved for the detection of red coloration in the leaves of shade-tolerant tropical plants, enabling the better exploitation of a food resource.

Investigation of Some Metals in Leaves and Leaf Extracts of Lippia javanica: Its Daily Intake

PubMed Central

Florence, Kunsamala

2017-01-01

Consumption of plant extracts can be a source of essential elements or a route of human exposure to toxicants. Metal concentrations in leaves, leaf brew, and infusion of L. javanica collected from five sites were determined by atomic absorption spectrometry after acid and aqueous extraction. Estimated daily intakes of metals in extracts were compared with recommended dietary allowances. Total metal concentrations in leaves varied with sampling sites (p < 0.05): Mn > Fe > Cu > Cr > Pb for sites SS2–SS5. The highest metal concentrations in leaves were recorded for SS3 (Cu: 15.32 ± 4.53 and Mn: 734.99 ± 105.49), SS5 (Fe: 210.27 ± 17.17), SS2 (Pb: 3.11 ± 0.21), and SS4 (Cr: 4.40 ± 0.75 mg/kg). Leaf infusion appeared to release higher Cu and Mn concentrations in leaves across sites (Cu: 21.65; Mn: 28.01%) than leaf brew (Cu: 11.95; Mn: 19.74%). Lead was not detected in leaf extracts. Estimated dietary intakes of Cr, Cu, Fe, and Mn were below recommended dietary allowances. A 250 ml cup of leaf infusion contributed 0.30–1.18% Cu and 4.46–13.83% Mn to the recommended dietary allowances of these elements per day. Lead did not pose any potential hazard when consumed in tea beverage made from brew and infusion of leaves of L. javanica. PMID:28781598

Mimosa pudica: Electrical and mechanical stimulation of plant movements.

PubMed

Volkov, Alexander G; Foster, Justin C; Ashby, Talitha A; Walker, Ronald K; Johnson, Jon A; Markin, Vladislav S

2010-02-01

Thigmonastic movements in the sensitive plant Mimosa pudica L., associated with fast responses to environmental stimuli, appear to be regulated through electrical and chemical signal transductions. The thigmonastic responses of M. pudica can be considered in three stages: stimulus perception, electrical signal transmission and induction of mechanical, hydrodynamical and biochemical responses. We investigated the mechanical movements of the pinnae and petioles in M. pudica induced by the electrical stimulation of a pulvinus, petiole, secondary pulvinus or pinna by a low electrical voltage and charge. The threshold value was 1.3-1.5 V of applied voltage and 2 to 10 microC of charge for the closing of the pinnules. Both voltage and electrical charge are responsible for the electro-stimulated closing of a leaf. The mechanism behind closing the leaf in M. pudica is discussed. The hydroelastic curvature mechanism closely describes the kinetics of M. pudica leaf movements.

A protocol for the creation of useful geometric shape metrics illustrated with a newly derived geometric measure of leaf circularity.

PubMed

Krieger, Jonathan D

2014-08-01

I present a protocol for creating geometric leaf shape metrics to facilitate widespread application of geometric morphometric methods to leaf shape measurement. • To quantify circularity, I created a novel shape metric in the form of the vector between a circle and a line, termed geometric circularity. Using leaves from 17 fern taxa, I performed a coordinate-point eigenshape analysis to empirically identify patterns of shape covariation. I then compared the geometric circularity metric to the empirically derived shape space and the standard metric, circularity shape factor. • The geometric circularity metric was consistent with empirical patterns of shape covariation and appeared more biologically meaningful than the standard approach, the circularity shape factor. The protocol described here has the potential to make geometric morphometrics more accessible to plant biologists by generalizing the approach to developing synthetic shape metrics based on classic, qualitative shape descriptors.

Nonlinear diffusion and viral spread through the leaf of a plant

NASA Astrophysics Data System (ADS)

Edwards, Maureen P.; Waterhouse, Peter M.; Munoz-Lopez, María Jesús; Anderssen, Robert S.

2016-10-01

The spread of a virus through the leaf of a plant is both spatially and temporally causal in that the present status depends on the past and the spatial spread is compactly supported and progresses outwards. Such spatial spread is known to occur for certain nonlinear diffusion processes. The first compactly supported solution for nonlinear diffusion equations appears to be that of Pattle published in 1959. In that paper, no explanation is given as to how the solution was derived. Here, we show how the solution can be derived using Lie symmetry analysis. This lays a foundation for exploring the behavior of other choices for nonlinear diffusion and exploring the addition of reaction terms which do not eliminate the compactly supported structure. The implications associated with using the reaction-diffusion equation to model the spatial-temporal spread of a virus through the leaf of a plant are discussed.

RADIATION-INDUCED CRINKLED LEAVES IN JUTE

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

Basu, R.K.

1963-01-01

Crinkled leaf chimeras appeared regularly, as phenocopies, in the X/sub 1/ and P/sub 1/ generations of three varieties of Corchorus olitorius L. The S/ sub 1/ populations were devoid of this abnormality. These plants were also characterized by late flowering and reduction in the number of flowers per plant. The frequency of crinaled leaf chimeras increased with increase in dosages of x rays and /sup 23/P beta rays. Inheritance studies revealed no immediate genetic background of these abnormal plants. However, mutations showing crinkled leaves were isolnted in some X/sub 3/ and P/sub 2/ lines and their segregation in later generationsmore » was found to be disturbed. Chromosomal abnormalities during metosis were considered as one of the factors responsible for the disturbed segregation. Crinkled leaf mutations also showed variable manifestation of the mutant characteristic in different years. (auth)« less

X-ray spectromicroscopic investigation of natural organochlorine distribution in weathering plant material

NASA Astrophysics Data System (ADS)

Leri, Alessandra C.; Marcus, Matthew A.; Myneni, Satish C. B.

2007-12-01

Natural organochlorine (Cl org) is ubiquitous in soil humus, but the distribution and cycling of different Cl species during the humification of plant material is poorly understood. Our X-ray spectromicroscopic studies indicate that the distributions of Cl org and inorganic Cl -(Cl inorg) in oak leaf material vary dramatically with decay stage, with the most striking changes occurring at the onset of weathering. In healthy or senescent leaves harvested from trees, Cl inorg occurs in sparsely distributed, highly localized "hotspots" associated with trichomes as well as in diffuse concentration throughout the leaf tissue. The Cl inorg associated with trichomes exists either in H-bonded form or in a solid salt matrix, while the Cl inorg in diffuse areas of lower Cl concentration appears exclusively in H-bonded form. Most solid phase Cl inorg leaches from the leaf tissue during early weathering stages, whereas the H-bonded Cl inorg appears to leach away slowly as degradation progresses, persisting through advanced weathering stages. In unweathered leaves, aromatic and aliphatic Cl org were found in rare but concentrated hotspots. In weathered leaves, by contrast, aromatic Cl org hotspots are prevalent, often coinciding with areas of elevated Fe or Mn concentration. Aromatic Cl org is highly soluble in leaves at early weathering stages and insoluble at more advanced stages. These results, combined with optical microscopy, suggest that fungi play a role in the production of aromatic Cl org in weathering leaf material. Aliphatic Cl org occurs in concentrated hotspots in weathered leaves as well as in diffuse areas of low Cl concentration. The distribution and speciation of Cl in weathering oak leaves depicted by this spectromicroscopic study provides new insight into the formation and cycling of Cl org during the decay of natural organic matter.

Anthracnose Diseases of Eastern Hardwoods

Treesearch

Frederick H. Berry

1985-01-01

Anthracnose diseases of hardwood trees are widespread throughout the Eastern United States. The most common symptom of these diseases is dead areas or blotches on the leaves. Because of the brown and black, scorched appearance of the leaves, the diseases are sometimes called leaf blight.

Psychrometric Field Measurement of Water Potential Changes following Leaf Excision.

PubMed

Savage, M J; Cass, A

1984-01-01

In situ measurement of sudden leaf water potential changes has not been performed under field conditions. A laboratory investigation involving the measurement of leaf water potential prior to and 2 to 200 minutes after excision of citrus leaves (Citrus jambhiri) showed good linear correlation (r = 0.99) between in situ leaf psychrometer and Scholander pressure chamber measurements. Following this, a field investigation was conducted which involved psychrometric measurement prior to petiole excision and 1 minute after excision. Simultaneous pressure chamber measurements were performed on neighboring leaves prior to the time of excision and then on the psychrometer leaf about 2 minutes after excision. These data indicate that within the first 2 minutes after excision, psychrometer and pressure chamber measurements were linearly correlated (r = 0.97). Under high evaporative demand conditions, the rate of water potential decrease was between 250 and 700 kilopascals in the first minute after excision. These results show that the thermocouple psychrometer can be used as a dynamic and nondestructive field technique for monitoring leaf water potential.

Psychrometric Field Measurement of Water Potential Changes following Leaf Excision 1

PubMed Central

Savage, Michael J.; Cass, Alfred

1984-01-01

In situ measurement of sudden leaf water potential changes has not been performed under field conditions. A laboratory investigation involving the measurement of leaf water potential prior to and 2 to 200 minutes after excision of citrus leaves (Citrus jambhiri) showed good linear correlation (r = 0.99) between in situ leaf psychrometer and Scholander pressure chamber measurements. Following this, a field investigation was conducted which involved psychrometric measurement prior to petiole excision and 1 minute after excision. Simultaneous pressure chamber measurements were performed on neighboring leaves prior to the time of excision and then on the psychrometer leaf about 2 minutes after excision. These data indicate that within the first 2 minutes after excision, psychrometer and pressure chamber measurements were linearly correlated (r = 0.97). Under high evaporative demand conditions, the rate of water potential decrease was between 250 and 700 kilopascals in the first minute after excision. These results show that the thermocouple psychrometer can be used as a dynamic and nondestructive field technique for monitoring leaf water potential. PMID:16663394

Comparing intra- and inter-specific effects on litter decomposition in an old-field ecosystem

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

Crutsinger, Greg; Sanders, Dr. Nathan James; Classen, Aimee T

2009-09-01

Plant species can differ in the quantity and quality of leaf litter they produce, and many studies have examined whether plant species diversity affects leaf-litter decomposition and nutrient release. A growing number of studies have indicated that intra-specific variation within plant species can also affect key ecosystem processes. However, the relative importance of intra- versus inter-specific variation for the functioning of ecosystems remains poorly known. Here, we investigate the effects of intra-specific variation in a dominant old-field plant species, tall goldenrod (Solidago altissima), and inter-specific variation among goldenrod species on litter quality, decomposition, and nitrogen (N) release. We found thatmore » the nutrient concentration of leaf litter varied among genotypes, which translated into 50% difference in decomposition rates. Variation among other goldenrod species in decomposition rate was more than twice that of genetic variation within S. altissima. Furthermore, by manipulating litterbags to contain 1, 3, 6, or 9 genotypes, we found that S. altissima genotype identity had much stronger effects than did genotypic diversity on leaf-litter quality, decomposition, and N release. Taken together, these results suggest that the order of ecological importance for controlling leaf-litter decomposition and N release dynamics is plant species identitygenotype identity>genotypic diversity.« less

Regeneration of Solanum nigrum by somatic embryogenesis, involving frog egg-like body, a novel structure.

PubMed

Xu, Kedong; Chang, Yunxia; Liu, Kun; Wang, Feige; Liu, Zhongyuan; Zhang, Ting; Li, Tong; Zhang, Yi; Zhang, Fuli; Zhang, Ju; Wang, Yan; Niu, Wei; Jia, Shuzhao; Xie, Hengchang; Tan, Guangxuan; Li, Chengwei

2014-01-01

A new protocol was established for the regeneration of Solanum nigrum by frog egg-like bodies (FELBs), which are novel somatic embryogenesis (SE) structures induced from the root, stem, and leaf explants. The root, stem, and leaf explants (93.33%, 85.10%, and 100.00%, respectively) were induced to form special embryonic calli on Murashige and Skoog (MS) medium containing 1.0 mg/L 2,4-dichlorophenoxyacetic acid, under dark condition. Further, special embryonic calli from the root, stem, and leaf explants (86.97%, 83.30%, and 99.47%, respectively) were developed into FELBs. Plantlets of FELBs from the three explants were induced in vitro on MS medium supplemented with 5.0 mg/L 6-benzylaminopurine and 0.1 mg/L gibberellic acid, and 100.00% plantlet induction rates were noted. However, plantlet induction in vivo on MS medium supplemented with 20 mg/L thidiazuron showed rates of 38.63%, 15.63%, and 61.30% for the root, stem, and leaf explants, respectively, which were lower than those of the in vitro culture. Morphological and histological analyses of FELBs at different development stages revealed that they are a novel type of SE structure that developed from the mesophyll (leaf) or cortex (stem and root) cells of S. nigrum.

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.

Leaf economic traits from fossils support a weedy habit for early angiosperms.

PubMed

Royer, Dana L; Miller, Ian M; Peppe, Daniel J; Hickey, Leo J

2010-03-01

Many key aspects of early angiosperms are poorly known, including their ecophysiology and associated habitats. Evidence for fast-growing, weedy angiosperms comes from the Early Cretaceous Potomac Group, where angiosperm fossils, some of them putative herbs, are found in riparian depositional settings. However, inferences of growth rate from sedimentology and growth habit are somewhat indirect; also, the geographic extent of a weedy habit in early angiosperms is poorly constrained. Using a power law between petiole width and leaf mass, we estimated the leaf mass per area (LMA) of species from three Albian (110-105 Ma) fossil floras from North America (Winthrop Formation, Patapsco Formation of the Potomac Group, and the Aspen Shale). All LMAs for angiosperm species are low (<125 g/m(2); mean = 76 g/m(2)) but are high for gymnosperm species (>240 g/m(2); mean = 291 g/m(2)). On the basis of extant relationships between LMA and other leaf economic traits such as photosynthetic rate and leaf lifespan, we conclude that these Early Cretaceous landscapes were populated with weedy angiosperms with short-lived leaves (<12 mo). The unrivalled capacity for fast growth observed today in many angiosperms was in place by no later than the Albian and likely played an important role in their subsequent ecological success.

Phosphorous fertilization alleviates drought effects on Alnus cremastogyne by regulating its antioxidant and osmotic potential.

PubMed

Tariq, Akash; Pan, Kaiwen; Olatunji, Olusanya Abiodun; Graciano, Corina; Li, Zilong; Sun, Feng; Zhang, Lin; Wu, Xiaogang; Chen, Wenkai; Song, Dagang; Huang, Dan; Xue, Tan; Zhang, Aiping

2018-04-04

Alnus cremastogyne, a broad-leaved tree endemic to south-western China, has both commercial and restoration importance. However, little is known of its morphological, physiological and biochemical responses to drought and phosphorous (P) application. A randomized experimental design was used to investigate how drought affected A. cremastogyne seedlings, and the role that P applications play in these responses. Drought had significant negative effects on A. cremastogyne growth and metabolism, as revealed by reduced biomass (leaf, shoot and root), leaf area, stem diameter, plant height, photosynthetic rate, leaf relative water content, and photosynthetic pigments, and a weakened antioxidative defence mechanism and high lipid peroxidation level. However, the reduced leaf area and enhanced osmolyte (proline and soluble sugars) accumulation suggests drought avoidance and tolerance strategies in this tree. Applying P significantly improved the leaf relative water content and photosynthetic rate of drought-stressed seedlings, which may reflect increased anti-oxidative enzyme (superoxide dismutase, catalase and peroxidase) activities, osmolyte accumulation, soluble proteins, and decreased lipid peroxidation levels. However, P had only a slight or negligible effect on the well-watered plants. A. cremastogyne is sensitive to drought stress, but P facilitates and improves its metabolism primarily via biochemical and physiological rather than morphological adjustments, regardless of water availability.

A steady-state stomatal model of balanced leaf gas exchange, hydraulics and maximal source-sink flux.

PubMed

Hölttä, Teemu; Lintunen, Anna; Chan, Tommy; Mäkelä, Annikki; Nikinmaa, Eero

2017-07-01

Trees must simultaneously balance their CO2 uptake rate via stomata, photosynthesis, the transport rate of sugars and rate of sugar utilization in sinks while maintaining a favourable water and carbon balance. We demonstrate using a numerical model that it is possible to understand stomatal functioning from the viewpoint of maximizing the simultaneous photosynthetic production, phloem transport and sink sugar utilization rate under the limitation that the transpiration-driven hydrostatic pressure gradient sets for those processes. A key feature in our model is that non-stomatal limitations to photosynthesis increase with decreasing leaf water potential and/or increasing leaf sugar concentration and are thus coupled to stomatal conductance. Maximizing the photosynthetic production rate using a numerical steady-state model leads to stomatal behaviour that is able to reproduce the well-known trends of stomatal behaviour in response to, e.g., light, vapour concentration difference, ambient CO2 concentration, soil water status, sink strength and xylem and phloem hydraulic conductance. We show that our results for stomatal behaviour are very similar to the solutions given by the earlier models of stomatal conductance derived solely from gas exchange considerations. Our modelling results also demonstrate how the 'marginal cost of water' in the unified stomatal conductance model and the optimal stomatal model could be related to plant structural and physiological traits, most importantly, the soil-to-leaf hydraulic conductance and soil moisture. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Species-specific temporal variation in photosynthesis as a moderator of peatland carbon sequestration

NASA Astrophysics Data System (ADS)

Korrensalo, Aino; Alekseychik, Pavel; Hájek, Tomáš; Rinne, Janne; Vesala, Timo; Mehtätalo, Lauri; Mammarella, Ivan; Tuittila, Eeva-Stiina

2017-01-01

In boreal bogs plant species are low in number, but they differ greatly in their growth forms and photosynthetic properties. We assessed how ecosystem carbon (C) sink dynamics were affected by seasonal variations in the photosynthetic rate and leaf area of different species. Photosynthetic properties (light response parameters), leaf area development and areal cover (abundance) of the species were used to quantify species-specific net and gross photosynthesis rates (PN and PG, respectively), which were summed to express ecosystem-level PN and PG. The ecosystem-level PG was compared with a gross primary production (GPP) estimate derived from eddy covariance (EC) measurements.Species areal cover, rather than differences in photosynthetic properties, determined the species with the highest PG of both vascular plants and Sphagna. Species-specific contributions to the ecosystem PG varied over the growing season, which, in turn, determined the seasonal variation in ecosystem PG. The upscaled growing season PG estimate, 230 g C m-2, agreed well with the GPP estimated by the EC (243 g C m-2).Sphagna were superior to vascular plants in ecosystem-level PG throughout the growing season but had a lower PN. PN results indicated that areal cover of the species, together with their differences in photosynthetic parameters, shape the ecosystem-level C balance. Species with low areal cover but high photosynthetic efficiency appear to be potentially important for the ecosystem C sink. Results imply that functional diversity, i.e., the presence of plant groups with different seasonal timing and efficiency of photosynthesis, may increase the stability of C sinks of boreal bogs.