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Sample records for nighttime stomatal conductance

  1. Interspecific variation in nighttime transpiration and stomatal conductance in a mixed New England deciduous forest.

    PubMed

    Daley, Michael J; Phillips, Nathan G

    2006-04-01

    Transpiration is generally assumed to be insignificant at night when stomata close in response to the lack of photosynthetically active radiation. However, there is increasing evidence that the stomata of some species remain open at night, which would allow for nighttime transpiration if there were a sufficient environmental driving force. We examined nighttime water use in co-occurring species in a mixed deciduous stand at Harvard Forest, MA, using whole-tree and leaf-level measurements. Diurnal whole-tree water use was monitored continuously with Granier-style sap flux sensors in paper birch (Betula papyrifera Marsh.), red oak (Quercus rubra L.) and red maple (Acer rubrum L.). An analysis was conducted in which nighttime water flux could be partitioned between refilling of internal water stores and transpiration. Substantial nighttime sap flux was observed in all species and much of this flux was attributed to the refilling of depleted water stores. However, in paper birch, nighttime sap flux frequently exceeded recharge estimates. Over 10% of the total daily sap flux during the growing season was due to transpiration at night in paper birch. Nighttime sap flux was over 8% of the total daily flux in red oak and 2% in red maple; however, this flux was mainly associated with recharge. On nights with elevated vapor pressure deficit, sap flux continued through the night in paper birch, whereas it reached zero during the night in red oak and red maple. Measurements of leaf-level gas exchange on a night with elevated vapor pressure deficit showed stomatal conductance dropping by only 25% in paper birch, while approaching zero in red oak and red maple. The study highlighted differences in ecophysiological controls on sap flux exerted by co-occurring species. Paper birch is a fast-growing, shade-intolerant species with an earlier successional status than red oak and red maple. Risking water loss through nighttime transpiration may provide paper birch with an ecological

  2. Canopy stomatal conductance

    SciTech Connect

    Baldocchi, D.D.; Luxmoore, R.J.; Hatfield, J.L.

    1989-07-14

    Stomata are major conduits for the diffusion of many trace gas species between leaves and the atmosphere. The role of the stomata on controlling gas exchange between the terrestrial biosphere and the atmosphere at the landscape, meso- and global-scales has only recently been recognized. Further advances in modelling large-scale trace gas exchange will depend on our ability to understand and model stomatal mechanics at the scale of the pertinent sub-unit, which is typically that of the canopy. This paper describes two approaches for estimating canopy stomatal conductance. One approach is based on 'bottom-up' scaling. This approach computes canopy stomatal conductance by integrating detailed leaf-level and environmentally-driven, physiological processes with the use of a detailed canopy micrometeorology model. The other approach is based on 'top-down' scaling. It interprets the integrated canopy stomatal conductance from measured fluxes of trace gas exchange. Frameworks for extending these scaling approaches to non-idea conditions are given. 96 refs., 5 figs.

  3. Relating Stomatal Conductance to Leaf Functional Traits

    PubMed Central

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

    2015-01-01

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

  4. Relating Stomatal Conductance to Leaf Functional Traits.

    PubMed

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

    2015-10-12

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

  5. Enhanced Stomatal Conductance by a Spontaneous Arabidopsis Tetraploid, Me-0, Results from Increased Stomatal Size and Greater Stomatal Aperture.

    PubMed

    Monda, Keina; Araki, Hiromitsu; Kuhara, Satoru; Ishigaki, Genki; Akashi, Ryo; Negi, Juntaro; Kojima, Mikiko; Sakakibara, Hitoshi; Takahashi, Sho; Hashimoto-Sugimoto, Mimi; Goto, Nobuharu; Iba, Koh

    2016-03-01

    The rate of gas exchange in plants is regulated mainly by stomatal size and density. Generally, higher densities of smaller stomata are advantageous for gas exchange; however, it is unclear what the effect of an extraordinary change in stomatal size might have on a plant's gas-exchange capacity. We investigated the stomatal responses to CO2 concentration changes among 374 Arabidopsis (Arabidopsis thaliana) ecotypes and discovered that Mechtshausen (Me-0), a natural tetraploid ecotype, has significantly larger stomata and can achieve a high stomatal conductance. We surmised that the cause of the increased stomatal conductance is tetraploidization; however, the stomatal conductance of another tetraploid accession, tetraploid Columbia (Col), was not as high as that in Me-0. One difference between these two accessions was the size of their stomatal apertures. Analyses of abscisic acid sensitivity, ion balance, and gene expression profiles suggested that physiological or genetic factors restrict the stomatal opening in tetraploid Col but not in Me-0. Our results show that Me-0 overcomes the handicap of stomatal opening that is typical for tetraploids and achieves higher stomatal conductance compared with the closely related tetraploid Col on account of larger stomatal apertures. This study provides evidence for whether larger stomatal size in tetraploids of higher plants can improve stomatal conductance. PMID:26754665

  6. Effects of stomatal development on stomatal conductance and on stomatal limitation of photosynthesis in Syringa oblata and Euonymus japonicus Thunb.

    PubMed

    Wu, Bing-Jie; Chow, Wah Soon; Liu, Yu-Jun; Shi, Lei; Jiang, Chuang-Dao

    2014-12-01

    During leaf development, the increase in stomatal conductance cannot meet photosynthetic demand for CO2, thus leading to stomatal limitation of photosynthesis (Ls). Considering the crucial influences of stomatal development on stomatal conductance, we speculated whether stomatal development limits photosynthesis to some extent. To test this hypothesis, stomatal development, stomatal conductance and photosynthesis were carefully studied in both Syringa oblata (normal greening species) and Euonymus japonicus Thunb (delayed greening species). Our results show that the size of stomata increased gradually with leaf expansion, resulting in increased stomatal conductance up to the time of full leaf expansion. During this process, photosynthesis also increased steadily. Compared to that in S. oblata, the development of chloroplasts in E. japonicus Thunb was obviously delayed, leading to a delay in the improvement of photosynthetic capacity. Further analysis revealed that before full leaf expansion, stomatal limitation increased rapidly in both S. oblata and E. japonicus Thunb; after full leaf expansion, stomatal limitation continually increased in E. japonicus Thunb. Accordingly, we suggested that the enhancement of photosynthetic capacity is the main factor leading to stomatal limitation during leaf development but that stomatal development can alleviate stomatal limitation with the increase of photosynthesis by controlling gas exchange. PMID:25443830

  7. Effects of stomatal development on stomatal conductance and on stomatal limitation of photosynthesis in Syringa oblata and Euonymus japonicus Thunb.

    PubMed

    Wu, Bing-Jie; Chow, Wah Soon; Liu, Yu-Jun; Shi, Lei; Jiang, Chuang-Dao

    2014-12-01

    During leaf development, the increase in stomatal conductance cannot meet photosynthetic demand for CO2, thus leading to stomatal limitation of photosynthesis (Ls). Considering the crucial influences of stomatal development on stomatal conductance, we speculated whether stomatal development limits photosynthesis to some extent. To test this hypothesis, stomatal development, stomatal conductance and photosynthesis were carefully studied in both Syringa oblata (normal greening species) and Euonymus japonicus Thunb (delayed greening species). Our results show that the size of stomata increased gradually with leaf expansion, resulting in increased stomatal conductance up to the time of full leaf expansion. During this process, photosynthesis also increased steadily. Compared to that in S. oblata, the development of chloroplasts in E. japonicus Thunb was obviously delayed, leading to a delay in the improvement of photosynthetic capacity. Further analysis revealed that before full leaf expansion, stomatal limitation increased rapidly in both S. oblata and E. japonicus Thunb; after full leaf expansion, stomatal limitation continually increased in E. japonicus Thunb. Accordingly, we suggested that the enhancement of photosynthetic capacity is the main factor leading to stomatal limitation during leaf development but that stomatal development can alleviate stomatal limitation with the increase of photosynthesis by controlling gas exchange.

  8. Nutrient and water addition effects on day- and night-time conductance and transpiration in a C3 desert annual.

    PubMed

    Ludwig, Fulco; Jewitt, Rebecca A; Donovan, Lisa A

    2006-06-01

    Recent research has shown that many C3 plant species have significant stomatal opening and transpire water at night even in desert habitats. Day-time stomatal regulation is expected to maximize carbon gain and prevent runaway cavitation, but little is known about the effect of soil resource availability on night-time stomatal conductance (g) and transpiration (E). Water (low and high) and nutrients (low and high) were applied factorially during the growing season to naturally occurring seedlings of the annual Helianthus anomalus. Plant height and biomass were greatest in the treatment where both water and nutrients were added, confirming resource limitations in this habitat. Plants from all treatments showed significant night-time g (approximately 0.07 mol m(-2) s(-1)) and E (approximately 1.5 mol m(-2) s(-1)). In July, water and nutrient additions had few effects on day- or night-time gas exchange. In August, however, plants in the nutrient addition treatments had lower day-time photosynthesis, g and E, paralleled by lower night-time g and E. Lower predawn water potentials and higher integrated photosynthetic water-use efficiency suggests that the nutrient addition indirectly induced a mild water stress. Thus, soil resources can affect night-time g and E in a manner parallel to day-time, although additional factors may also be involved.

  9. Nocturnal and daytime stomatal conductance respond to root-zone temperature in ‘Shiraz’ grapevines

    PubMed Central

    Rogiers, Suzy Y.; Clarke, Simon J.

    2013-01-01

    Background and Aims Daytime root-zone temperature may be a significant factor regulating water flux through plants. Water flux can also occur during the night but nocturnal stomatal response to environmental drivers such as root-zone temperature remains largely unknown. Methods Here nocturnal and daytime leaf gas exchange was quantified in ‘Shiraz’ grapevines (Vitis vinifera) exposed to three root-zone temperatures from budburst to fruit-set, for a total of 8 weeks in spring. Key Results Despite lower stomatal density, night-time stomatal conductance and transpiration rates were greater for plants grown in warm root-zones. Elevated root-zone temperature resulted in higher daytime stomatal conductance, transpiration and net assimilation rates across a range of leaf-to-air vapour pressure deficits, air temperatures and light levels. Intrinsic water-use efficiency was, however, lowest in those plants with warm root-zones. CO2 response curves of foliar gas exchange indicated that the maximum rate of electron transport and the maximum rate of Rubisco activity did not differ between the root-zone treatments, and therefore it was likely that the lower photosynthesis in cool root-zones was predominantly the result of a stomatal limitation. One week after discontinuation of the temperature treatments, gas exchange was similar between the plants, indicating a reversible physiological response to soil temperature. Conclusions In this anisohydric grapevine variety both night-time and daytime stomatal conductance were responsive to root-zone temperature. Because nocturnal transpiration has implications for overall plant water status, predictive climate change models using stomatal conductance will need to factor in this root-zone variable. PMID:23293018

  10. Smaller, faster stomata: scaling of stomatal size, rate of response, and stomatal conductance

    PubMed Central

    Franks, Peter J.

    2013-01-01

    Maximum and minimum stomatal conductance, as well as stomatal size and rate of response, are known to vary widely across plant species, but the functional relationship between these static and dynamic stomatal properties is unknown. The objective of this study was to test three hypotheses: (i) operating stomatal conductance under standard conditions (g op) correlates with minimum stomatal conductance prior to morning light [g min(dawn)]; (ii) stomatal size (S) is negatively correlated with g op and the maximum rate of stomatal opening in response to light, (dg/dt)max; and (iii) g op correlates negatively with instantaneous water-use efficiency (WUE) despite positive correlations with maximum rate of carboxylation (Vc max) and light-saturated rate of electron transport (J max). Using five closely related species of the genus Banksia, the above variables were measured, and it was found that all three hypotheses were supported by the results. Overall, this indicates that leaves built for higher rates of gas exchange have smaller stomata and faster dynamic characteristics. With the aid of a stomatal control model, it is demonstrated that higher g op can potentially expose plants to larger tissue water potential gradients, and that faster stomatal response times can help offset this risk. PMID:23264516

  11. Pore size regulates operating stomatal conductance, while stomatal densities drive the partitioning of conductance between leaf sides

    PubMed Central

    Fanourakis, Dimitrios; Giday, Habtamu; Milla, Rubén; Pieruschka, Roland; Kjaer, Katrine H.; Bolger, Marie; Vasilevski, Aleksandar; Nunes-Nesi, Adriano; Fiorani, Fabio; Ottosen, Carl-Otto

    2015-01-01

    Background and Aims Leaf gas exchange is influenced by stomatal size, density, distribution between the leaf adaxial and abaxial sides, as well as by pore dimensions. This study aims to quantify which of these traits mainly underlie genetic differences in operating stomatal conductance (gs) and addresses possible links between anatomical traits and regulation of pore width. Methods Stomatal responsiveness to desiccation, gs-related anatomical traits of each leaf side and estimated gs (based on these traits) were determined for 54 introgression lines (ILs) generated by introgressing segments of Solanum pennelli into the S. lycopersicum ‘M82’. A quantitative trait locus (QTL) analysis for stomatal traits was also performed. Key Results A wide genetic variation in stomatal responsiveness to desiccation was observed, a large part of which was explained by stomatal length. Operating gs ranged over a factor of five between ILs. The pore area per stomatal area varied 8-fold among ILs (2–16 %), and was the main determinant of differences in operating gs between ILs. Operating gs was primarily positioned on the abaxial surface (60–83 %), due to higher abaxial stomatal density and, secondarily, to larger abaxial pore area. An analysis revealed 64 QTLs for stomatal traits in the ILs, most of which were in the direction of S. pennellii. Conclusions The data indicate that operating and maximum gs of non-stressed leaves maintained under stable conditions deviate considerably (by 45–91 %), because stomatal size inadequately reflects operating pore area (R2 = 0·46). Furthermore, it was found that variation between ILs in both stomatal sensitivity to desiccation and operating gs is associated with features of individual stoma. In contrast, genotypic variation in gs partitioning depends on the distribution of stomata between the leaf adaxial and abaxial epidermis. PMID:25538116

  12. Enhanced Stomatal Conductance by a Spontaneous Arabidopsis Tetraploid, Me-0, Results from Increased Stomatal Size and Greater Stomatal Aperture1[OPEN

    PubMed Central

    Monda, Keina; Araki, Hiromitsu; Kuhara, Satoru; Ishigaki, Genki; Akashi, Ryo; Negi, Juntaro; Kojima, Mikiko; Sakakibara, Hitoshi; Takahashi, Sho; Hashimoto-Sugimoto, Mimi; Goto, Nobuharu; Iba, Koh

    2016-01-01

    The rate of gas exchange in plants is regulated mainly by stomatal size and density. Generally, higher densities of smaller stomata are advantageous for gas exchange; however, it is unclear what the effect of an extraordinary change in stomatal size might have on a plant’s gas-exchange capacity. We investigated the stomatal responses to CO2 concentration changes among 374 Arabidopsis (Arabidopsis thaliana) ecotypes and discovered that Mechtshausen (Me-0), a natural tetraploid ecotype, has significantly larger stomata and can achieve a high stomatal conductance. We surmised that the cause of the increased stomatal conductance is tetraploidization; however, the stomatal conductance of another tetraploid accession, tetraploid Columbia (Col), was not as high as that in Me-0. One difference between these two accessions was the size of their stomatal apertures. Analyses of abscisic acid sensitivity, ion balance, and gene expression profiles suggested that physiological or genetic factors restrict the stomatal opening in tetraploid Col but not in Me-0. Our results show that Me-0 overcomes the handicap of stomatal opening that is typical for tetraploids and achieves higher stomatal conductance compared with the closely related tetraploid Col on account of larger stomatal apertures. This study provides evidence for whether larger stomatal size in tetraploids of higher plants can improve stomatal conductance. PMID:26754665

  13. Regulation of stomatal conductance and transpiration in forest canopies.

    PubMed

    Whitehead, David

    1998-01-01

    Processes regulating stomatal conductance, g(s), and transpiration, E, from forest canopies are reviewed. The first section deals with the response of g(s) to environmental variables. Phenomenological models have been used to interpret field data and predict diurnal and seasonal variability in g(s), but models that couple stomatal conductance to photosynthesis at the leaf scale are now being used more widely. The vertical distribution of foliar nitrogen concentration is helpful for scaling these processes from leaves to canopies, and the analysis of data from many studies has led to the emergence of simplified, general relationships for estimating evaporation and carbon uptake by forests at stand and regional scales. Evidence for the regulation of stomatal conductance by hydraulic and chemical signals is presented in the second section. Rapid and reversible changes in g(s) following a perturbation to the water potential gradient in the flow pathway suggest that stomata respond directly to hydrostatic signals. Other evidence supports the contention that signals are transmitted by abscisic acid (ABA), possibly originating in the roots. For large woody plants, the short-term responses of stomata are probably brought about by hydraulic signals that affect g(s) by triggering the release of ABA in the leaves. Tardieu and Davies (1993) developed an interactive model that incorporates hydraulic and chemical effects to describe the response of stomata to soil drying and evaporative demand. In the third section, evidence is presented that short-term changes in g(s) are linked closely to the hydraulic properties of the conducting system to minimize loss of hydraulic conductivity through xylem by cavitation. Examples of homeostatic mechanisms that operate to ensure the long-term balance between evaporative demand and the potential hydraulic conductivity of trees growing in different environments are described. Two hypotheses are examined: (1) height growth in trees is limited

  14. Helianthus Nighttime Conductance and Transpiration Respond to Soil Water But Not Nutrient Availability1[W][OA

    PubMed Central

    Howard, Ava R.; Donovan, Lisa A.

    2007-01-01

    We investigated the response of Helianthus species nighttime conductance (gnight) and transpiration (Enight) to soil nutrient and water limitations in nine greenhouse studies. The studies primarily used wild Helianthus annuus, but also included a commercial and early domesticate of H. annuus and three additional wild species (Helianthus petiolaris Nutt., Helianthus deserticola Heiser, and Helianthus anomalus Blake). Well-watered plants of all species showed substantial gnight (0.023–0.225 mol m−2 s−1) and Enight (0.29–2.46 mmol m−2 s−1) measured as instantaneous gas exchange. Based on the potential for transpiration to increase mass flow of mobile nutrients to roots, we hypothesized that gnight and Enight would increase under limiting soil nutrients but found no evidence of responses in all six studies testing this. Based on known daytime responses to water limitation, we hypothesized that gnight and Enight would decrease when soil water availability was limited, and results from all four studies testing this supported our hypothesis. We also established that stomatal conductance at night was on average 5 times greater than cuticular conductance. Additionally, gnight and Enight varied nocturnally and across plant reproductive stages while remaining relatively constant as leaves aged. Our results further the ability to predict conditions under which nighttime water loss will be biologically significant and demonstrate that for Helianthus, gnight can be regulated. PMID:17142487

  15. Impact of the representation of stomatal conductance on model projections of heatwave intensity

    NASA Astrophysics Data System (ADS)

    Kala, Jatin; de Kauwe, Martin G.; Pitman, Andy J.; Medlyn, Belinda E.; Wang, Ying-Ping; Lorenz, Ruth; Perkins-Kirkpatrick, Sarah E.

    2016-03-01

    Stomatal conductance links plant water use and carbon uptake, and is a critical process for the land surface component of climate models. However, stomatal conductance schemes commonly assume that all vegetation with the same photosynthetic pathway use identical plant water use strategies whereas observations indicate otherwise. Here, we implement a new stomatal scheme derived from optimal stomatal theory and constrained by a recent global synthesis of stomatal conductance measurements from 314 species, across 56 field sites. Using this new stomatal scheme, within a global climate model, subtantially increases the intensity of future heatwaves across Northern Eurasia. This indicates that our climate model has previously been under-predicting heatwave intensity. Our results have widespread implications for other climate models, many of which do not account for differences in stomatal water-use across different plant functional types, and hence, are also likely under projecting heatwave intensity in the future.

  16. Impact of the representation of stomatal conductance on model projections of heatwave intensity.

    PubMed

    Kala, Jatin; De Kauwe, Martin G; Pitman, Andy J; Medlyn, Belinda E; Wang, Ying-Ping; Lorenz, Ruth; Perkins-Kirkpatrick, Sarah E

    2016-01-01

    Stomatal conductance links plant water use and carbon uptake, and is a critical process for the land surface component of climate models. However, stomatal conductance schemes commonly assume that all vegetation with the same photosynthetic pathway use identical plant water use strategies whereas observations indicate otherwise. Here, we implement a new stomatal scheme derived from optimal stomatal theory and constrained by a recent global synthesis of stomatal conductance measurements from 314 species, across 56 field sites. Using this new stomatal scheme, within a global climate model, subtantially increases the intensity of future heatwaves across Northern Eurasia. This indicates that our climate model has previously been under-predicting heatwave intensity. Our results have widespread implications for other climate models, many of which do not account for differences in stomatal water-use across different plant functional types, and hence, are also likely under projecting heatwave intensity in the future. PMID:26996244

  17. Impact of the representation of stomatal conductance on model projections of heatwave intensity

    PubMed Central

    Kala, Jatin; De Kauwe, Martin G.; Pitman, Andy J.; Medlyn, Belinda E.; Wang, Ying-Ping; Lorenz, Ruth; Perkins-Kirkpatrick, Sarah E.

    2016-01-01

    Stomatal conductance links plant water use and carbon uptake, and is a critical process for the land surface component of climate models. However, stomatal conductance schemes commonly assume that all vegetation with the same photosynthetic pathway use identical plant water use strategies whereas observations indicate otherwise. Here, we implement a new stomatal scheme derived from optimal stomatal theory and constrained by a recent global synthesis of stomatal conductance measurements from 314 species, across 56 field sites. Using this new stomatal scheme, within a global climate model, subtantially increases the intensity of future heatwaves across Northern Eurasia. This indicates that our climate model has previously been under-predicting heatwave intensity. Our results have widespread implications for other climate models, many of which do not account for differences in stomatal water-use across different plant functional types, and hence, are also likely under projecting heatwave intensity in the future. PMID:26996244

  18. Plasticity in maximum stomatal conductance constrained by negative correlation between stomatal size and density: an analysis using Eucalyptus globulus.

    PubMed

    Franks, Peter J; Drake, Paul L; Beerling, David J

    2009-12-01

    Maximum stomatal conductance to water vapour and CO2 (gwmax, gcmax, respectively), which are set at the time of leaf maturity, are determined predominantly by stomatal size (S) and density (D). In theory, many combinations of S and D yield the same gwmax and gcmax, so there is no inherent correlation between S and D, or between S, D and maximum stomatal conductance. However, using basic equations for gas diffusion through stomata of different sizes, we show that a negative correlation between S and D offers several advantages, including plasticity in gwmax and gcmax with minimal change in epidermal area allocation to stomata. Examination of the relationship between S and D in Eucalyptus globulus seedlings and coppice shoots growing in the field under high and low rainfall revealed a strong negative relationship between S and D, whereby S decreased with increasing D according to a negative power function. The results provide evidence that plasticity in maximum stomatal conductance may be constrained by a negative S versus D relationship, with higher maximum stomatal conductance characterized by smaller S and higher D, and a tendency to minimize change in epidermal space allocation to stomata as S and D vary.

  19. CO2 Sensing and CO2 Regulation of Stomatal Conductance: Advances and Open Questions.

    PubMed

    Engineer, Cawas B; Hashimoto-Sugimoto, Mimi; Negi, Juntaro; Israelsson-Nordström, Maria; Azoulay-Shemer, Tamar; Rappel, Wouter-Jan; Iba, Koh; Schroeder, Julian I

    2016-01-01

    Guard cells form epidermal stomatal gas-exchange valves in plants and regulate the aperture of stomatal pores in response to changes in the carbon dioxide (CO2) concentration ([CO2]) in leaves. Moreover, the development of stomata is repressed by elevated CO2 in diverse plant species. Evidence suggests that plants can sense [CO2] changes via guard cells and via mesophyll tissues in mediating stomatal movements. We review new discoveries and open questions on mechanisms mediating CO2-regulated stomatal movements and CO2 modulation of stomatal development, which together function in the CO2 regulation of stomatal conductance and gas exchange in plants. Research in this area is timely in light of the necessity of selecting and developing crop cultivars that perform better in a shifting climate. PMID:26482956

  20. Tree-Level Hydrodynamic Approach for Improved Stomatal Conductance Parameterization

    NASA Astrophysics Data System (ADS)

    Mirfenderesgi, G.; Bohrer, G.; Matheny, A. M.; Ivanov, V. Y.

    2014-12-01

    The land-surface models do not mechanistically resolve hydrodynamic processes within the tree. The Finite-Elements Tree-Crown Hydrodynamics model version 2 (FETCH2) is based on the pervious FETCH model approach, but with finite difference numerics, and simplified single-beam conduit system. FETCH2 simulates water flow through the tree as a simplified system of porous media conduits. It explicitly resolves spatiotemporal hydraulic stresses throughout the tree's vertical extent that cannot be easily represented using other stomatal-conductance models. Empirical equations relate water potential at the stem to stomata conductance at leaves connected to the stem (through unresolved branches) at that height. While highly simplified, this approach bring some realism to the simulation of stomata conductance because the stomata can respond to stem water potential, rather than an assumed direct relationship with soil moisture, as is currently the case in almost all models. By enabling mechanistic simulation of hydrological traits, such as xylem conductivity, conductive area per DBH, vertical distribution of leaf area and maximal and minimal water content in the xylem, and their effect of the dynamics of water flow in the tree system, the FETCH2 modeling system enhanced our understanding of the role of hydraulic limitations on an experimental forest plot short-term water stresses that lead to tradeoffs between water and light availability for transpiring leaves in forest ecosystems. FETCH2 is particularly suitable to resolve the effects of structural differences between tree and species and size groups, and the consequences of differences in hydraulic strategies of different species. We leverage on a large dataset of sap flow from 60 trees of 4 species at our experimental plot at the University of Michigan Biological Station. Comparison of the sap flow and transpiration patterns in this site and an undisturbed control site shows significant difference in hydraulic strategies

  1. ENVIRONMENTAL STRESS AND GENETICS INFLUENCE NIGHTTIME LEAF CONDUCTANCE IN THE C4 GRASS DISTICHLIS SPICATA

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Growing awareness of nighttime leaf conductance (gnight) in many species, as well as genetic variation in gnight within several species, has raised questions about how genetic variation and environmental stress interact to influence the magnitude of gnight. The objective of this study was to invest...

  2. Ozone exposure causes a decoupling of conductance and photosynthesis: implications for the Ball-Berry stomatal conductance model.

    PubMed

    Lombardozzi, Danica; Sparks, Jed P; Bonan, Gordon; Levis, Samuel

    2012-07-01

    Industrialization has significantly altered atmospheric chemistry by increasing concentrations of chemicals such as nitrogen oxides (NO( x )) and volatile organic carbon, which react in the presence of sunlight to produce tropospheric ozone (O(3)). Ozone is a powerful oxidant that causes both visual and physiological damage to plants, impairing the ability of the plant to control processes like photosynthesis and transpiration. Damage to photosynthesis and stomatal conductance does not always occur at the same rate, which generates a problem when using the Ball-Berry model to predict stomatal conductance because the calculations directly rely on photosynthesis rates. The goals of this work were to develop a modeling framework to modify Ball-Berry stomatal conductance predictions independently of photosynthesis and to test the framework using experimental data. After exposure to elevated O(3) in open-top chambers, photosynthesis and stomatal conductance in tulip poplar changed at different rates through time. We were able to accurately model observed photosynthetic and stomatal conductance responses to chronic O(3) exposure in a Ball-Berry framework by adjusting stomatal conductance in addition to photosynthesis. This led to a significant improvement in the modeled ability to predict both photosynthesis and stomatal conductance responses to O(3).

  3. Genetic variation in circadian regulation of nocturnal stomatal conductance enhances carbon assimilation and growth.

    PubMed

    Resco de Dios, Víctor; Loik, Michael E; Smith, Renee; Aspinwall, Michael J; Tissue, David T

    2016-01-01

    Circadian resonance, whereby a plant's endogenous rhythms are tuned to match environmental cues, has been repeatedly shown to be adaptive, although the underlying mechanisms remain elusive. Concomitantly, the adaptive value of nocturnal transpiration in C3 plants remains unknown because it occurs without carbon assimilation. These seemingly unrelated processes are interconnected because circadian regulation drives temporal patterns in nocturnal stomatal conductance, with maximum values occurring immediately before dawn for many species. We grew individuals of six Eucalyptus camaldulensis genotypes in naturally lit glasshouses and measured sunset, predawn and midday leaf gas exchange and whole-plant biomass production. We tested whether sunrise anticipation by the circadian clock and subsequent increases in genotype predawn stomatal conductance led to rapid stomatal opening upon illumination, ultimately affecting genotype differences in carbon assimilation and growth. We observed faster stomatal responses to light inputs at sunrise in genotypes with higher predawn stomatal conductance. Moreover, early morning and midday stomatal conductance and carbon assimilation, leaf area and total plant biomass were all positively correlated with predawn stomatal conductance across genotypes. Our results lead to the novel hypothesis that genotypic variation in the circadian-regulated capacity to anticipate sunrise could be an important factor underlying intraspecific variation in tree growth. PMID:26147129

  4. Genetic variation in circadian regulation of nocturnal stomatal conductance enhances carbon assimilation and growth.

    PubMed

    Resco de Dios, Víctor; Loik, Michael E; Smith, Renee; Aspinwall, Michael J; Tissue, David T

    2016-01-01

    Circadian resonance, whereby a plant's endogenous rhythms are tuned to match environmental cues, has been repeatedly shown to be adaptive, although the underlying mechanisms remain elusive. Concomitantly, the adaptive value of nocturnal transpiration in C3 plants remains unknown because it occurs without carbon assimilation. These seemingly unrelated processes are interconnected because circadian regulation drives temporal patterns in nocturnal stomatal conductance, with maximum values occurring immediately before dawn for many species. We grew individuals of six Eucalyptus camaldulensis genotypes in naturally lit glasshouses and measured sunset, predawn and midday leaf gas exchange and whole-plant biomass production. We tested whether sunrise anticipation by the circadian clock and subsequent increases in genotype predawn stomatal conductance led to rapid stomatal opening upon illumination, ultimately affecting genotype differences in carbon assimilation and growth. We observed faster stomatal responses to light inputs at sunrise in genotypes with higher predawn stomatal conductance. Moreover, early morning and midday stomatal conductance and carbon assimilation, leaf area and total plant biomass were all positively correlated with predawn stomatal conductance across genotypes. Our results lead to the novel hypothesis that genotypic variation in the circadian-regulated capacity to anticipate sunrise could be an important factor underlying intraspecific variation in tree growth.

  5. Predicting photosynthesis and transpiration responses to ozone: decoupling modeled photosynthesis and stomatal conductance

    NASA Astrophysics Data System (ADS)

    Lombardozzi, D.; Levis, S.; Bonan, G.; Sparks, J. P.

    2012-08-01

    Plants exchange greenhouse gases carbon dioxide and water with the atmosphere through the processes of photosynthesis and transpiration, making them essential in climate regulation. Carbon dioxide and water exchange are typically coupled through the control of stomatal conductance, and the parameterization in many models often predict conductance based on photosynthesis values. Some environmental conditions, like exposure to high ozone (O3) concentrations, alter photosynthesis independent of stomatal conductance, so models that couple these processes cannot accurately predict both. The goals of this study were to test direct and indirect photosynthesis and stomatal conductance modifications based on O3 damage to tulip poplar (Liriodendron tulipifera) in a coupled Farquhar/Ball-Berry model. The same modifications were then tested in the Community Land Model (CLM) to determine the impacts on gross primary productivity (GPP) and transpiration at a constant O3 concentration of 100 parts per billion (ppb). Modifying the Vcmax parameter and directly modifying stomatal conductance best predicts photosynthesis and stomatal conductance responses to chronic O3 over a range of environmental conditions. On a global scale, directly modifying conductance reduces the effect of O3 on both transpiration and GPP compared to indirectly modifying conductance, particularly in the tropics. The results of this study suggest that independently modifying stomatal conductance can improve the ability of models to predict hydrologic cycling, and therefore improve future climate predictions.

  6. A Coupled Model of Photosynthesis, Stomatal Conductance and Transpiration for a Rose Leaf (Rosa hybrida L.)

    PubMed Central

    KIM, SOO‐HYUNG; LIETH, J. HEINRICH

    2003-01-01

    The following three models were combined to predict simultaneously photosynthesis, stomatal conductance, transpiration and leaf temperature of a rose leaf: the biochemical model of photosynthesis of Farquhar, von Caemmerer and Berry (1980, Planta 149: 78–90), the stomatal conductance model of Ball, Woodrow and Berry (In: Biggens J, ed. Progress in photosynthesis research. The Netherlands: Martinus Nijhoff Publishers), and an energy balance model. The photosynthetic parameters: maximum carboxylation rate, potential rate of electron transport and rate of triose phosphate utilization, and their temperature dependence were determined using gas exchange data of fully expanded, young, sunlit leaves. The stomatal conductance model was calibrated independently. Prediction of net photosynthesis by the coupled model agreed well with the validation data, but the model tended to underestimate rates of stomatal conductance and transpiration. The coupled model developed in this study can be used to assist growers making environmental control decisions in glasshouse production. PMID:12730065

  7. A test of an optimal stomatal conductance scheme within the CABLE land surface model

    NASA Astrophysics Data System (ADS)

    De Kauwe, M. G.; Kala, J.; Lin, Y.-S.; Pitman, A. J.; Medlyn, B. E.; Duursma, R. A.; Abramowitz, G.; Wang, Y.-P.; Miralles, D. G.

    2015-02-01

    Stomatal conductance (gs) affects the fluxes of carbon, energy and water between the vegetated land surface and the atmosphere. We test an implementation of an optimal stomatal conductance model within the Community Atmosphere Biosphere Land Exchange (CABLE) land surface model (LSM). In common with many LSMs, CABLE does not differentiate between gs model parameters in relation to plant functional type (PFT), but instead only in relation to photosynthetic pathway. We constrained the key model parameter "g1", which represents plant water use strategy, by PFT, based on a global synthesis of stomatal behaviour. As proof of concept, we also demonstrate that the g1 parameter can be estimated using two long-term average (1960-1990) bioclimatic variables: (i) temperature and (ii) an indirect estimate of annual plant water availability. The new stomatal model, in conjunction with PFT parameterisations, resulted in a large reduction in annual fluxes of transpiration (~ 30% compared to the standard CABLE simulations) across evergreen needleleaf, tundra and C4 grass regions. Differences in other regions of the globe were typically small. Model performance against upscaled data products was not degraded, but did not noticeably reduce existing model-data biases. We identified assumptions relating to the coupling of the vegetation to the atmosphere and the parameterisation of the minimum stomatal conductance as areas requiring further investigation in both CABLE and potentially other LSMs. We conclude that optimisation theory can yield a simple and tractable approach to predicting stomatal conductance in LSMs.

  8. A test of an optimal stomatal conductance scheme within the CABLE Land Surface Model

    NASA Astrophysics Data System (ADS)

    De Kauwe, M. G.; Kala, J.; Lin, Y.-S.; Pitman, A. J.; Medlyn, B. E.; Duursma, R. A.; Abramowitz, G.; Wang, Y.-P.; Miralles, D. G.

    2014-10-01

    Stomatal conductance (gs) affects the fluxes of carbon, energy and water between the vegetated land surface and the atmosphere. We test an implementation of an optimal stomatal conductance model within the Community Atmosphere Biosphere Land Exchange (CABLE) land surface model (LSM). In common with many LSMs, CABLE does not differentiate between gs model parameters in relation to plant functional type (PFT), but instead only in relation to photosynthetic pathway. We therefore constrained the key model parameter "g1" which represents a plants water use strategy by PFT based on a global synthesis of stomatal behaviour. As proof of concept, we also demonstrate that the g1 parameter can be estimated using two long-term average (1960-1990) bioclimatic variables: (i) temperature and (ii) an indirect estimate of annual plant water availability. The new stomatal models in conjunction with PFT parameterisations resulted in a large reduction in annual fluxes of transpiration (~ 30% compared to the standard CABLE simulations) across evergreen needleleaf, tundra and C4 grass regions. Differences in other regions of the globe were typically small. Model performance when compared to upscaled data products was not degraded, though the new stomatal conductance scheme did not noticeably change existing model-data biases. We conclude that optimisation theory can yield a simple and tractable approach to predicting stomatal conductance in LSMs.

  9. Modelling stomatal conductance in Acacia caven: A two way approach to understand vapor fluxes

    NASA Astrophysics Data System (ADS)

    Raab, N.; Meza, F. J.

    2012-12-01

    Evapotranspiration fluxes from semi arid ecosystems show a strong interannual variability and dependence on water availability. Usually this variable is regarded as very small but at local scale could substantially affect water balance at basin level. Climate Change scenarios for these regions are a source of concern as they project an increase in temperature, leading to a greater atmospheric water demand. In addition, precipitation is expected to decrease, increasing pressure for this kind of ecosystems. At a plant level, a rise on the actual atmospheric CO2 concentration is expected to improve photosynthetic performance and water use efficiency. However, as stomatal conductance is the main pathway for water vapor flux, from the leaf to the atmosphere, and CO2 entrance to the substomatal cavity, a larger control of the stomatal opening, due to a severe water control lost from the plant, could lead to shortages in net assimilation, jeopardizing the behavior of Semi Arid ecosystems as natural carbon sinks. Stoma is also one of the main lock of the soil-plant-water continuum, thus finally controlling the rate of soil water depletion. Its modeling presents a key role in determining future groundwater availability and net ecosystem exchange. There are several approaches for stomatal conductance modeling, from mechanistic models, based on the physiological functioning of the stomata, to empirical models where the stomatal behavior is correlated with environmental conditions. We modeled stomatal conductance for a Chilean typical Mediterranean Savannanh, dominated by Acacia caven, comparing two different empirical approaches. We used a Shuttleworth and Wallace model for sparse canopies combined with an inversion of the Penman-Monteith equation. This model allowed us to link stomatal conductance to evapotranspiration. The second approach was based on a multiplicative model for stomatal conductance based on environmental limitation, following Jarvis's model

  10. The temperature sensitivity of guard cell respiration CO- segregates with stomatal conductances in a F2 population of pima cotton

    SciTech Connect

    Lu, Zhenmin; Quinones, M.A.; Zeiger, E. )

    1993-05-01

    Stomatal conductances in lines of Pima cotton selected for higher yields and heat resistance increase as a function of selection. Lines with contrasting rates of stomatal conductances also have contrasting rates of guard cell respiration and proton pumping. In this work, we studied stomatal conductances and guard cell respiration rates in a F2 population of a cross between S-6, a heat-resistant, high yielding line, and B368, a heat sensitive primitive cotton. F2 plants were grown in a greenhouse (temperature=30[degrees]C at noon) and a growth chamber (12 h light, 40[degrees]C/12 h dark 28[degrees]C). conductances were 3-fold higher at 40[degrees]C than at 25[degrees]C in greenhouse-grown plants and 4-fold higher in growth chamber-grown plants. The range of stomatal conductances in segregating F2 plants increased sharply with temperature, indicating that the genetic differences between the parental populations are better expressed at high temperature. Respiration rates of guard cells measured in mechanically isolated, enzymatically cleaned epidermis, co-segregated with stomatal conductances. Plants with high stomatal conductances had high rates of guard cell respiration. The slope of guard cell respiration as a function of temperature increased linearly with stomatal conductances. The co-segregation of rates of guard cell respiration and stomatal conductances indicates that both properties are under genetic control, and that guard cell respiration is a component of the sensory transduction of the stomatal response to temperature.

  11. Variation in photosynthesis and stomatal conductance in an ozone-stressed Ponderosa pine stand: light response

    SciTech Connect

    Cooyne, P.I,; Bingham, G.E.

    1982-06-01

    The seasonal course (May to October 1977) of gross photosynthesis (from /sup 14/CO/sub 2/ uptake and stomatal conductance) in a stand of ponderosa pine (Pinus ponderosa Laws.) in the San Bernardino National Forest was characterized as a function of light. Nine sapling trees, classified for comparative studies into three chronic injury classes (slight, moderate, severe) had experienced oxidant fumigations from California's South Coast Air Basin for approximately 18 years, since their establishment following fire. The CO/sub 2/-transfer pathway was partitioned into its stomatal and residual (mesophyll, carboxylation, excitation) resistance components, for conditions of light saturation and 20/sup 0/C. Light-saturated gross photosynthetic rates and photochemical conversion efficiencies were highest in the current-year needles and decreased with increasing needle age and oxidant injury. Maximum stomatal conductance and stomatal sensitivity to increasing light during stomatal opening followed a trend similar to that of photosynthesis, except for current-year needles, where conductance parameters were highest in the severely injured trees. This higher conductance may contribute to observed differential ozone sensitivity in ponderosa pine. Premature senesence and abscission of the 1-year (severely injured trees) and 2-year (slight to moderate injury) needles occurred at about the time CO/sub 2/ uptake dropped to 10 percent of the potential for current needles of slightly injured trees without foliar injury symptoms. The ratio of the stomatal CO/sub 2/ resistance to the total CO/sub 2/ resistance decreased with increasing oxidant injury and needle age, suggesting that loss of photosynthetic capacity was primarily related to the loss of chloroplast function rather than to increased resistance of CO/sub 2/ diffusion through the stomata.

  12. Thermal infrared imaging of the temporal variability in stomatal conductance for fruit trees

    NASA Astrophysics Data System (ADS)

    Struthers, Raymond; Ivanova, Anna; Tits, Laurent; Swennen, Rony; Coppin, Pol

    2015-07-01

    Repeated measurements using thermal infrared remote sensing were used to characterize the change in canopy temperature over time and factors that influenced this change on 'Conference' pear trees (Pyrus communis L.). Three different types of sensors were used, a leaf porometer to measure leaf stomatal conductance, a thermal infrared camera to measure the canopy temperature and a meteorological sensor to measure weather variables. Stomatal conductance of water stressed pear was significantly lower than in the control group 9 days after stress began. This decrease in stomatal conductance reduced transpiration, reducing evaporative cooling that increased canopy temperature. Using thermal infrared imaging with wavelengths between 7.5 and13 μm, the first significant difference was measured 18 days after stress began. A second order derivative described the average rate of change of the difference between the stress treatment and control group. The average rate of change for stomatal conductance was 0.06 (mmol m-2 s-1) and for canopy temperature was -0.04 (°C) with respect to days. Thermal infrared remote sensing and data analysis presented in this study demonstrated that the differences in canopy temperatures between the water stress and control treatment due to stomata regulation can be validated.

  13. On estimating canopy photosynthesis and stomatal conductance in a deciduous forest with clumped foliage.

    PubMed

    Baldocchi, Dennis D.; Hutchison, Boyd A.

    1986-12-01

    The foliage in a fully-leafed deciduous forest canopy is clumped. Consequently, theory indicates that the probability of beam penetration will be estimated more accurately with a model based on the negative binomial distribution than with a model based on the Poisson distribution, incorporating an assumption of a spherical leaf inclination angle distribution. Flux densities of photosynthetically active radiation (PAR) were measured in and above a deciduous forest canopy and were computed with the canopy radiative transfer models based on the negative binomial and Poisson distributions. These radiation values were used to compute canopy photosynthesis and stomatal conductance. Canopy photosynthesis and stomatal conductance, based on the negative binomial model, overestimated values computed from measured PAR profiles by 8 and 9%. respectively. The canopy photosynthesis and stomatal conductance values computed with the spherical Poisson model under-estimated measured values by 17 and 10%, respectively. Thus, the negative binomial radiative transfer model improves estimates of canopy photosynthesis and, to a lesser extent, stomatal conductance, inside a deciduous forest.

  14. Changing Stomatal Conductance in Response to Anthropogenic Climate Change: a Model-Data Comparison

    NASA Astrophysics Data System (ADS)

    Purcell, C.; Batke, S.; Caballero, R.; McElwain, J.

    2015-12-01

    Understanding the response of stomatal conductance to increasing anthropogenic CO2 is of critical importance for the evaluation of the global hydrological cycle, and has implications for future climate change, particularly flood and risk. Via physiological and morphological changes in leaf structure, stomatal conductance has been shown to decrease under elevated CO2 conditions, stimulating higher vegetation water use efficiency and water retention within the land system. However, an assessment of how the simulation of changing stomatal conductance in an Earth System Model compares with observational data under varying CO2 concentrations (Free Air CO2 Enrichment - FACE - studies) has not yet been conducted, and is crucial for considering the significance of the issue of flooding for global policy making. Here we utilise the Community Land Model, Version 4.5 (CLM4.5), performing climate simulations over a range of atmospheric CO2 concentrations from 350ppm to 700ppm (50ppm increments), and compare the model data with results from a conclusive set of FACE studies (350ppm - 700ppm range). We show general agreement between the climate model and FACE data with regards to decreasing stomatal conductance in response to increasing CO2 concentration. However the magnitudes of the conductance changes differ, spatially within the model, and across species in the FACE studies. We show how the model can be used to assess global stomatal conductance changes on spatial scales where FACE cannot (ie. most FACE studies are located across the 30°- 60° latitude belt). This is useful for understanding the role of groundwater retention and potential flood risk at regional scales across the globe. Additionally the model demonstrates seasonal-spatial changes in stomatal conductance in response to CO2 forcing. Such seasonal changes are generally absent throughout FACE studies, as measurement is predominantly tasked during summer months. Our results reiterate the importance of climate

  15. Surface Geometry and Stomatal Conductance Effects on Evaporation From Aquatic Macrophytes

    NASA Astrophysics Data System (ADS)

    Anderson, Michael G.; Idso, Sherwood B.

    1987-06-01

    Evaporative water loss rates of several floating and emergent aquatic macrophytes were studied over a 4-year period through comparison of daily evaporative water losses from similar-sized vegetated (E) and open water (E0) surfaces. Two species with planate floating leaves (water fern and water lily) yielded E/E0 values of 0.90 for one and four growing seasons, respectively, and displayed stomatal regulation of potential evaporation. Water hyacinths grown in ponds with different diameters exhibited E/E0 ratios which decreased with increasing pond diameter for both short (0.06-0.36 m) and tall (0.63-0.81 m) plants, producing high linear correlations with amount of peripheral vegetative surface area. The latter relationships suggested an E/E0 value less than unity for a relatively extensive canopy of short water hyacinths and a value of the order of 1.4 for a tall canopy possessing similar two-dimensional surface area characteristics. The latter results were also demonstrated in a separate study utilizing polyurethane foam to insulate the peripheral exposure of tall water hyacinth canopies from advective energy. Finally, simultaneous stomatal conductance and daily E/E0 measurements on cattail and water hyacinth canopies with identical tank diameters indicated that although the mean stomatal conductance of the peripheral exposure of the cattail canopy was 72% less than that of the water hyacinth canopy, its total evaporative water loss was nearly equivalent, due to its greater height. Reducing the surface area of the peripheral cattail exposure by the fractional amount suggested by the stomatal conductance measurements harmonized its surface geometry-evaporation relationship with that of the water hyacinth canopy and once again demonstrated the reality of stomatal control of potential evaporation.

  16. Effects of carbonyl sulfide (COS) and carbonic anhydrase on stomatal conductance

    NASA Astrophysics Data System (ADS)

    Yakir, D.; Stimler, K.; Berry, J. A.

    2011-12-01

    The potential use of COS as tracer of the gross, one-way, CO2 flux into plants is based on its co-diffusion with CO2 into leaves without outflux stimulated research on COS-CO2 interactions during leaf gas exchange. We carried out gas exchange measurements of COS and CO2 in 22 plant species representing deciduous and evergreen trees, grasses, and shrubs, under a range of light intensities and ambient COS concentrations, using mid IR laser spectroscopy. A narrow range in the normalized ratio of the net uptake rates of COS (As) and CO2 (Ac; As/Ac*[CO2]/[COS]) was observed, with a mean value of 1.61±0.26. These results reflect the dominance of stomatal conductance over both COS and CO2 uptake, imposing a relatively constant ratio between the two fluxes (except under low light conditions when CO2, but not COS, metabolism is light limited). A relatively constant ratio under common ambient conditions will facilitate the application of COS as a tracer of gross photosynthesis from leaf to global scales. However, its effect on stomatal conductance may require a special attention. Increasing COS concentrations between 250 and 2800 pmol mol-1 (enveloping atmospheric levels) seems to stimulate stomatal conductance. We examined the stimulation of conductance by COS in a range of species and show that there is a large variation with some species showing almost no response while others are highly responsive (up to doubling stomatal conductance). Using C3 and C4 plants with antisense lines abolishing carbonic anhydrase activity, we show that the activity of this enzyme is essential for both the uptake of COS and the enhancement of stomatal conductance by COS. Since carbonic anhydrase catalyzes the conversion of COS to CO2 and H2S it seems likely that the stomata are responding to H2S produced in the mesophyll. In all natural species examined the uptake of COS and CO2 were highly correlated, and there was no relationship between the sensitivity of stomata and the rate of COS uptake

  17. Co-ordination of hydraulic and stomatal conductances across light qualities in cucumber leaves.

    PubMed

    Savvides, Andreas; Fanourakis, Dimitrios; van Ieperen, Wim

    2012-02-01

    Long-term effects of light quality on leaf hydraulic conductance (K(leaf)) and stomatal conductance (g(s)) were studied in cucumber, and their joint impact on leaf photosynthesis in response to osmotic-induced water stress was assessed. Plants were grown under low intensity monochromatic red (R, 640 nm), blue (B, 420 nm) or combined red and blue (R:B, 70:30) light. K(leaf) and g(s) were much lower in leaves that developed without blue light. Differences in g(s) were caused by differences in stomatal aperture and stomatal density, of which the latter was largely due to differences in epidermal cell size and hardly due to stomatal development. Net photosynthesis (A(N)) was lowest in R-, intermediate in B-, and highest in RB- grown leaves. The low A(N) in R-grown leaves correlated with a low leaf internal CO(2) concentration and reduced PSII operating efficiency. In response to osmotic stress, all leaves showed similar degrees of stomatal closure, but the reduction in A(N) was larger in R- than in B- and RB-grown leaves. This was probably due to damage of the photosynthetic apparatus, which only occurred in R-grown leaves. The present study shows the co-ordination of K(leaf) and g(s) across different light qualities, while the presence of blue in the light spectrum seems to drive both K(leaf) and g(s) towards high, sun-type leaf values, as was previously reported for maximal photosynthetic capacity and leaf morphology. The present results suggest the involvement of blue light receptors in the usually harmonized development of leaf characteristics related to water relations and photosynthesis under different light environments.

  18. Optimal stomatal conductance in relation to photosynthesis in climatically contrasting Eucalyptus species under drought.

    PubMed

    Héroult, Arnaud; Lin, Yan-Shih; Bourne, Aimee; Medlyn, Belinda E; Ellsworth, David S

    2013-02-01

    Models of stomatal conductance (g(s)) are based on coupling between g(s) and CO(2) assimilation (A(net)), and it is often assumed that the slope of this relationship ('g(1) ') is constant across species. However, if different plant species have adapted to different access costs of water, then there will be differences in g(1) among species. We hypothesized that g(1) should vary among species adapted to different climates, and tested the theory and its linkage to plant hydraulics using four Eucalyptus species from different climatic origins in a common garden. Optimal stomatal theory predicts that species from sub-humid zones have a lower marginal water cost of C gain, hence lower g(1) than humid-zone species. In agreement with the theory that g(1) is related to tissue carbon costs for water supply, we found a relationship between wood density and g(1) across Eucalyptus species of contrasting climatic origins. There were significant reductions in the parameter g(1) during drought in humid but not sub-humid species, with the latter group maintaining g(1) in drought. There are strong differences in stomatal behaviour among related tree species in agreement with optimal stomatal theory, and these differences are consistent with the economics involved in water uptake and transport for carbon gain. PMID:22762345

  19. Stomatal conductance of lettuce grown under or exposed to different light qualities

    NASA Technical Reports Server (NTRS)

    Kim, Hyeon-Hye; Goins, Gregory D.; Wheeler, Raymond M.; Sager, John C.

    2004-01-01

    BACKGROUND AND AIMS: The objective of this research was to examine the effects of differences in light spectrum on the stomatal conductance (Gs) and dry matter production of lettuce plants grown under a day/night cycle with different spectra, and also the effects on Gs of short-term exposure to different spectra. METHODS: Lettuce (Lactuca sativa) plants were grown with 6 h dark and 18 h light under four different spectra, red-blue (RB), red-blue-green (RBG), green (GF) and white (CWF), and Gs and plant growth were measured. KEY RESULTS AND CONCLUSIONS: Conductance of plants grown for 23 d under CWF rose rapidly on illumination to a maximum in the middle of the light period, then decreased again before the dark period when it was minimal. However, the maximum was smaller in plants grown under RB, RGB and GF. This demonstrates that spectral quality during growth affects the diurnal pattern of stomatal conductance. Although Gs was smaller in plants grown under RGB than CWF, dry mass accumulation was greater, suggesting that Gs did not limit carbon assimilation under these spectral conditions. Temporarily changing the spectral quality of the plants grown for 23 d under CWF, affected stomatal responses reversibly, confirming studies on epidermal strips. This study provides new information showing that Gs is responsive to spectral quality during growth and, in the short-term, is not directly coupled to dry matter accumulation.

  20. Electrical signaling, stomatal conductance, ABA and Ethylene content in avocado trees in response to root hypoxia

    PubMed Central

    Gurovich, Luis; Schaffer, Bruce; García, Nicolás; Iturriaga, Rodrigo

    2009-01-01

    Avocado (Persea americana Mill.) trees are among the most sensitive of fruit tree species to root hypoxia as a result of flooded or poorly drained soil. Similar to drought stress, an early physiological response to root hypoxia in avocado is a reduction of stomatal conductance. It has been previously determined in avocado trees that an extracellular electrical signal between the base of stem and leaves is produced and related to reductions in stomatal conductance in response to drought stress. The current study was designed to determine if changes in the extracellular electrical potential between the base of the stem and leaves in avocado trees could also be detected in response to short-term (min) or long-term (days) root hypoxia, and if these signals could be related to stomatal conductance (gs), root and leaf ABA and ACC concentrations, ethylene emission from leaves and leaf abscission. In contrast to previous observations for drought-stressed trees, short-term or long-term root hypoxia did not stimulate an electrical potential difference between the base of the stem and leaves. Short-term hypoxia did not result in a significant decrease in gs compared with plants in the control treatment, and no differences in ABA concentration were found between plants subjected to hypoxia and control plants. Long-term hypoxia in the root zone resulted in a significant decrease in gs, increased leaf ethylene and increased leaf abscission. The results indicate that for avocado trees exposed to root hypoxia, electrical signals do not appear to be the primary root-to-shoot communication mechanism involved in signaling for stomatal closure as a result of hypoxia in the root zone. PMID:19649181

  1. Electrical signaling, stomatal conductance, ABA and ethylene content in avocado trees in response to root hypoxia.

    PubMed

    Gil, Pilar M; Gurovich, Luis; Schaffer, Bruce; García, Nicolás; Iturriaga, Rodrigo

    2009-02-01

    Avocado (Persea americana Mill.) trees are among the most sensitive of fruit tree species to root hypoxia as a result of flooded or poorly drained soil. Similar to drought stress, an early physiological response to root hypoxia in avocado is a reduction of stomatal conductance. It has been previously determined in avocado trees that an extracellular electrical signal between the base of stem and leaves is produced and related to reductions in stomatal conductance in response to drought stress. The current study was designed to determine if changes in the extracellular electrical potential between the base of the stem and leaves in avocado trees could also be detected in response to short-term (min) or long-term (days) root hypoxia, and if these signals could be related to stomatal conductance (gs), root and leaf ABA and ACC concentrations, ethylene emission from leaves and leaf abscission. In contrast to previous observations for drought-stressed trees, short-term or long-term root hypoxia did not stimulate an electrical potential difference between the base of the stem and leaves. Short-term hypoxia did not result in a significant decrease in gs compared with plants in the control treatment, and no differences in ABA concentration were found between plants subjected to hypoxia and control plants. Long-term hypoxia in the root zone resulted in a significant decrease in gs, increased leaf ethylene and increased leaf abscission. The results indicate that for avocado trees exposed to root hypoxia, electrical signals do not appear to be the primary root-to-shoot communication mechanism involved in signaling for stomatal closure as a result of hypoxia in the root zone.

  2. A Modeling Approach to Quantify the Effects of Stomatal Behavior and Mesophyll Conductance on Leaf Water Use Efficiency

    PubMed Central

    Moualeu-Ngangue, Dany P.; Chen, Tsu-Wei; Stützel, Hartmut

    2016-01-01

    Water use efficiency (WUE) is considered as a determinant of yield under stress and a component of crop drought resistance. Stomatal behavior regulates both transpiration rate and net assimilation and has been suggested to be crucial for improving crop WUE. In this work, a dynamic model was used to examine the impact of dynamic properties of stomata on WUE. The model includes sub-models of stomatal conductance dynamics, solute accumulation in the mesophyll, mesophyll water content, and water flow to the mesophyll. Using the instantaneous value of stomatal conductance, photosynthesis, and transpiration rate were simulated using a biochemical model and Penman-Monteith equation, respectively. The model was parameterized for a cucumber leaf and model outputs were evaluated using climatic data. Our simulations revealed that WUE was higher on a cloudy than a sunny day. Fast stomatal reaction to light decreased WUE during the period of increasing light (e.g., in the morning) by up to 10.2% and increased WUE during the period of decreasing light (afternoon) by up to 6.25%. Sensitivity of daily WUE to stomatal parameters and mesophyll conductance to CO2 was tested for sunny and cloudy days. Increasing mesophyll conductance to CO2 was more likely to increase WUE for all climatic conditions (up to 5.5% on the sunny day) than modifications of stomatal reaction speed to light and maximum stomatal conductance. PMID:27379150

  3. A Modeling Approach to Quantify the Effects of Stomatal Behavior and Mesophyll Conductance on Leaf Water Use Efficiency.

    PubMed

    Moualeu-Ngangue, Dany P; Chen, Tsu-Wei; Stützel, Hartmut

    2016-01-01

    Water use efficiency (WUE) is considered as a determinant of yield under stress and a component of crop drought resistance. Stomatal behavior regulates both transpiration rate and net assimilation and has been suggested to be crucial for improving crop WUE. In this work, a dynamic model was used to examine the impact of dynamic properties of stomata on WUE. The model includes sub-models of stomatal conductance dynamics, solute accumulation in the mesophyll, mesophyll water content, and water flow to the mesophyll. Using the instantaneous value of stomatal conductance, photosynthesis, and transpiration rate were simulated using a biochemical model and Penman-Monteith equation, respectively. The model was parameterized for a cucumber leaf and model outputs were evaluated using climatic data. Our simulations revealed that WUE was higher on a cloudy than a sunny day. Fast stomatal reaction to light decreased WUE during the period of increasing light (e.g., in the morning) by up to 10.2% and increased WUE during the period of decreasing light (afternoon) by up to 6.25%. Sensitivity of daily WUE to stomatal parameters and mesophyll conductance to CO2 was tested for sunny and cloudy days. Increasing mesophyll conductance to CO2 was more likely to increase WUE for all climatic conditions (up to 5.5% on the sunny day) than modifications of stomatal reaction speed to light and maximum stomatal conductance. PMID:27379150

  4. Effects of CO2 on stomatal conductance: do stomata open at very high CO2 concentrations?

    NASA Technical Reports Server (NTRS)

    Wheeler, R. M.; Mackowiak, C. L.; Yorio, N. C.; Sager, J. C.

    1999-01-01

    Potato and wheat plants were grown for 50 d at 400, 1000 and 10000 micromoles mol-1 carbon dioxide (CO2). and sweetpotato and soybean were grown at 1000 micromoles mol-1 CO2 in controlled environment chambers to study stomatal conductance and plant water use. Lighting was provided with fluorescent lamps as a 12 h photoperiod with 300 micromoles m-2 s-1 PAR. Mid-day stomatal conductances for potato were greatest at 400 and 10000 micromoles mol-1 and least at 1000 micromoles mol-1 CO2. Mid-day conductances for wheat were greatest at 400 micromoles mol-1 and least at 1000 and 10000 micromoles mol-1 CO2. Mid-dark period conductances for potato were significantly greater at 10000 micromoles mol-1 than at 400 or 1000 micromoles mol-1, whereas dark conductance for wheat was similar in all CO2 treatments. Temporarily changing the CO2 concentration from the native 1000 micromoles mol-1 to 400 micromoles mol-1 increased mid-day conductance for all species, while temporarily changing from 1000 to 10000 micromoles mol-1 also increased conductance for potato and sweetpotato. Temporarily changing the dark period CO2 from 1000 to 10000 micromoles mol-1 increased conductance for potato, soybean and sweetpotato. In all cases, the stomatal responses were reversible, i.e. conductances returned to original rates following temporary changes in CO2 concentration. Canopy water use for potato was greatest at 10000, intermediate at 400, and least at 1000 micromoles mol-1 CO2, whereas canopy water use for wheat was greatest at 400 and similar at 1000 and 10000 micromoles mol-1 CO2. Elevated CO2 treatments (i.e. 1000 and 10000 micromoles mol-1) resulted in increased plant biomass for both wheat and potato relative to 400 micromoles mol-1, and no injurious effects were apparent from the 10000 micromoles mol-1 treatment. Results indicate that super-elevated CO2 (i.e. 10000 micromoles mol-1) can increase stomatal conductance in some species, particularly during the dark period, resulting in

  5. CO2-induced decrease of canopy stomatal conductance of mature conifer and broadleaved trees

    NASA Astrophysics Data System (ADS)

    Tor-ngern, P.; Oren, R.; Ward, E. J.; Palmroth, S.; McCarthy, H. R.; domec, J.

    2013-12-01

    Together with canopy leaf area, mean canopy stomatal conductance (GS) controls forest-atmosphere exchanges of energy and mass. Expectations for stomatal response to elevated atmospheric [CO2] (CO2E) based on seedling studies range from large decreases of conductance in foliage of broadleaved species to little or no response in conifers. These responses are not directly translatable to forest canopies, and their underlying mechanisms are ill-defined. The uncertainty of canopy-scale stomatal response to CO2E reduces confidence in modeled predictions of future forest productivity and carbon sequestration, and of partitioning of net radiation between latent and sensible heat flux. Thus, debates on the potential effects of CO2E-induced stomatal closure continue. We used a Free-Air CO2 Enrichment (FACE) experiment in a 27-year-old, 25 m tall forest, to generate a whole-canopy CO2-response and test whether canopy-scale GS response to CO2E of widely distributed, fast growing shade-intolerant species, Pinus taeda (L.) and co-occurring broadleaved species dominated by Liquidambar styraciflua (L.), was indirectly affected by slow changes such as hydraulic adjustments and canopy development, as opposed to quickly responding to CO2 concentrations in the leaf-internal air space. Our results show indirect CO2E-induced reductions of GS of 10% and 30%, respectively, and no signs of a direct stomatal response even as CO2E was pushed to 685 μmol mol-1 (~1.8 of ambient). Modeling the effect of CO2E on the water, energy and carbon cycles of forests must consider slow-response indirect mechanisms producing large variation in the reduction of GS, such as the previously observed inconsistent CO2E effect on canopy leaf area and plant hydraulics. Moreover, the new generation of CO2E studies in forests must allow indirect effects caused by, e.g., hydraulic adjustments and canopy development, to play out. Such acclimation will be particularly prolonged in slowly developing ecosystems, such

  6. Stomatal responses to changes in vapor pressure deficit reflect tissue-specific differences in hydraulic conductance.

    PubMed

    Ocheltree, T W; Nippert, J B; Prasad, P V V

    2014-01-01

    The vapor pressure deficit (D) of the atmosphere can negatively affect plant growth as plants reduce stomatal conductance to water vapor (g(wv)) in response to increasing D, limiting the ability of plants to assimilate carbon. The sensitivity of g(wv) to changes in D varies among species and has been correlated with the hydraulic conductance of leaves (K(leaf) ), but the hydraulic conductance of other tissues has also been implicated in plant responses to changing D. Among the 19 grass species, we found that K(leaf) was correlated with the hydraulic conductance of large longitudinal veins (K(lv), r(2) = 0.81), but was not related to K(root) (r(2) = 0.01). Stomatal sensitivity to D was correlated with K(leaf) relative to total leaf area (r(2) = 0.50), and did not differ between C3 and C4 species. Transpiration (E) increased in response to D, but 8 of the 19 plants showed a decline in E at high D, indicative of an 'apparent feedforward' response. For these individuals, E began to decline at lower values of D in plants with low K(root) (r(2) = 0.72). These results show the significance of both leaf and root hydraulic conductance as drivers of plant responses to evaporative demand.

  7. Carbonyl sulfide (COS) as a tracer for canopy photosynthesis, transpiration and stomatal conductance: potential and limitations.

    PubMed

    Wohlfahrt, Georg; Brilli, Federico; Hörtnagl, Lukas; Xu, Xiaobin; Bingemer, Heinz; Hansel, Armin; Loreto, Francesco

    2012-04-01

    The theoretical basis for the link between the leaf exchange of carbonyl sulfide (COS), carbon dioxide (CO(2)) and water vapour (H(2)O) and the assumptions that need to be made in order to use COS as a tracer for canopy net photosynthesis, transpiration and stomatal conductance, are reviewed. The ratios of COS to CO(2) and H(2)O deposition velocities used to this end are shown to vary with the ratio of the internal to ambient CO(2) and H(2)O mole fractions and the relative limitations by boundary layer, stomatal and internal conductance for COS. It is suggested that these deposition velocity ratios exhibit considerable variability, a finding that challenges current parameterizations, which treat these as vegetation-specific constants. COS is shown to represent a better tracer for CO(2) than H(2)O. Using COS as a tracer for stomatal conductance is hampered by our present poor understanding of the leaf internal conductance to COS. Estimating canopy level CO(2) and H(2)O fluxes requires disentangling leaf COS exchange from other ecosystem sources/sinks of COS. We conclude that future priorities for COS research should be to improve the quantitative understanding of the variability in the ratios of COS to CO(2) and H(2)O deposition velocities and the controlling factors, and to develop operational methods for disentangling ecosystem COS exchange into contributions by leaves and other sources/sinks. To this end, integrated studies, which concurrently quantify the ecosystem-scale CO(2), H(2)O and COS exchange and the corresponding component fluxes, are urgently needed.

  8. Stomatal conductance and not stomatal density determines the long-term reduction in leaf transpiration of poplar in elevated CO2.

    PubMed

    Tricker, Penny J; Trewin, Harriet; Kull, Olevi; Clarkson, Graham J J; Eensalu, Eve; Tallis, Matthew J; Colella, Alessio; Doncaster, C Patrick; Sabatti, Maurizio; Taylor, Gail

    2005-05-01

    Using a free-air CO2 enrichment (FACE) experiment, poplar trees (Populus x euramericana clone I214) were exposed to either ambient or elevated [CO2] from planting, for a 5-year period during canopy development, closure, coppice and re-growth. In each year, measurements were taken of stomatal density (SD, number mm(-2)) and stomatal index (SI, the proportion of epidermal cells forming stomata). In year 5, measurements were also taken of leaf stomatal conductance (gs, micromol m(-2) s(-1)), photosynthetic CO2 fixation (A, mmol m(-2) s(-1)), instantaneous water-use efficiency (A/E) and the ratio of intercellular to atmospheric CO2 (Ci:Ca). Elevated [CO2] caused reductions in SI in the first year, and in SD in the first 2 years, when the canopy was largely open. In following years, when the canopy had closed, elevated [CO2] had no detectable effects on stomatal numbers or index. In contrast, even after 5 years of exposure to elevated [CO2], gs was reduced, A/E was stimulated, and Ci:Ca was reduced relative to ambient [CO2]. These outcomes from the long-term realistic field conditions of this forest FACE experiment suggest that stomatal numbers (SD and SI) had no role in determining the improved instantaneous leaf-level efficiency of water use under elevated [CO2]. We propose that altered cuticular development during canopy closure may partially explain the changing response of stomata to elevated [CO2], although the mechanism for this remains obscure.

  9. Role of leaf hydraulic conductance in the regulation of stomatal conductance in almond and olive in response to water stress.

    PubMed

    Hernandez-Santana, Virginia; Rodriguez-Dominguez, Celia M; Fernández, J Enrique; Diaz-Espejo, Antonio

    2016-06-01

    The decrease of stomatal conductance (gs) is one of the prime responses to water shortage and the main determinant of yield limitation in fruit trees. Understanding the mechanisms related to stomatal closure in response to imposed water stress is crucial for correct irrigation management. The loss of leaf hydraulic functioning is considered as one of the major factors triggering stomatal closure. Thus, we conducted an experiment to quantify the dehydration response of leaf hydraulic conductance (Kleaf) and its impact on gs in two Mediterranean fruit tree species, one deciduous (almond) and one evergreen (olive). Our hypothesis was that a higher Kleaf would be associated with a higher gs and that the reduction in Kleaf would predict the reduction in gs in both species. We measured Kleaf in olive and almond during a cycle of irrigation withholding. We also compared the results of two methods to measure Kleaf: dynamic rehydration kinetics and evaporative flux methods. In addition, determined gs, leaf water potential (Ψleaf), vein density, photosynthetic capacity and turgor loss point. Results showed that gs was higher in almond than in olive and so was Kleaf (Kmax = 4.70 and 3.42 mmol s(-1) MPa(-1) m(-2), in almond and olive, respectively) for Ψleaf > -1.2 MPa. At greater water stress levels than -1.2 MPa, however, Kleaf decreased exponentially, being similar for both species, while gs was still higher in almond than in olive. We conclude that although the Kleaf decrease with increasing water stress does not drive unequivocally the gs response to water stress, Kleaf is the variable most strongly related to the gs response to water stress, especially in olive. Other variables such as the increase in abscisic acid (ABA) may be playing an important role in gs regulation, although in our study the gs-ABA relationship did not show a clear pattern. PMID:26846979

  10. Role of leaf hydraulic conductance in the regulation of stomatal conductance in almond and olive in response to water stress.

    PubMed

    Hernandez-Santana, Virginia; Rodriguez-Dominguez, Celia M; Fernández, J Enrique; Diaz-Espejo, Antonio

    2016-06-01

    The decrease of stomatal conductance (gs) is one of the prime responses to water shortage and the main determinant of yield limitation in fruit trees. Understanding the mechanisms related to stomatal closure in response to imposed water stress is crucial for correct irrigation management. The loss of leaf hydraulic functioning is considered as one of the major factors triggering stomatal closure. Thus, we conducted an experiment to quantify the dehydration response of leaf hydraulic conductance (Kleaf) and its impact on gs in two Mediterranean fruit tree species, one deciduous (almond) and one evergreen (olive). Our hypothesis was that a higher Kleaf would be associated with a higher gs and that the reduction in Kleaf would predict the reduction in gs in both species. We measured Kleaf in olive and almond during a cycle of irrigation withholding. We also compared the results of two methods to measure Kleaf: dynamic rehydration kinetics and evaporative flux methods. In addition, determined gs, leaf water potential (Ψleaf), vein density, photosynthetic capacity and turgor loss point. Results showed that gs was higher in almond than in olive and so was Kleaf (Kmax = 4.70 and 3.42 mmol s(-1) MPa(-1) m(-2), in almond and olive, respectively) for Ψleaf > -1.2 MPa. At greater water stress levels than -1.2 MPa, however, Kleaf decreased exponentially, being similar for both species, while gs was still higher in almond than in olive. We conclude that although the Kleaf decrease with increasing water stress does not drive unequivocally the gs response to water stress, Kleaf is the variable most strongly related to the gs response to water stress, especially in olive. Other variables such as the increase in abscisic acid (ABA) may be playing an important role in gs regulation, although in our study the gs-ABA relationship did not show a clear pattern.

  11. Effects of soil temperature on parameters of a coupled photosynthesis-stomatal conductance model.

    PubMed

    Cai, Tiebo; Dang, Qing-Lai

    2002-08-01

    To examine the effects of soil temperature on a coupled photosynthesis-stomatal conductance model, seedlings of trembling aspen (Populus tremuloides Michx.), jack pine (Pinus banksiana Lamb.), black spruce (Picea Mariana (Mill.) B.S.P.) and white spruce (Picea glauca (Moench) Voss) were exposed to soil temperatures ranging from 5 to 35 degrees C for 4 months. Light and CO(2) response curves of foliar gas exchange were measured for model parameterization. The effects of soil temperature on four key model parameters, V(cmax) (maximum rate of carboxylation), J(max) (maximum rate of electron transport), alpha (energy conversion efficiency or quantum efficiency of electron transport) and R(d) (daytime dark respiration), were modeled using two third-order polynomial equations and a modified Arrhenius equation. In all species, V(cmax) and J(max) increased with soil temperature up to an optimum, and then decreased with further increases in soil temperature. In the conifers, alpha showed a similar response to soil temperature as V(cmax) and J(max), but soil temperature had no significant effect on alpha in aspen. Soil temperature had no significant effect on R(d) in any species. The three equations described the relationships between soil temperature and the model parameters reasonably well, but performed best for V(cmax) and worst for alpha. No significant relationships were identified between soil temperature and the parameters of the stomatal conductance model. PMID:12184971

  12. Continent-Wide Decrease of Stomatal Conductance in Vegetation During Large Droughts of the Recent Decade

    NASA Astrophysics Data System (ADS)

    Peters, W.; van der Velde, I.; Miller, J. B.; Schaefer, K. M.; Tans, P. P.; Vaughn, B. H.; White, J. W. C.; van der Molen, M. K.

    2015-12-01

    Severe droughts in the Northern Hemisphere caused widespread decline of agricultural yield, reduction of forest carbon uptake, and increased CO₂ growth rates in the atmosphere during the past decade. Plants respond to droughts by partially closing their stomata to limit their evaporative water loss, at the expense of carbon uptake by photosynthesis. Here we present new evidence on this drought response of terrestrial vegetation derived from year-to-year changes in the 13C/12C stable isotope ratio in atmospheric CO2. Observations from more than 50,000 flask samples from the NOAA Global Greenhouse Gas Reference Network suggest a strong decrease in stomatal conductance in vegetation that is highly correlated (see green line in the figure) with reductions of net carbon uptake over the Northern Hemisphere. This correlation is driven by severe drought conditions over areas several million km2 in size in Europe (2003, 2006), Russia (2010), and the United States (2002). This spatially integrated vegetation drought response at this scale can not be measured from laboratory experiments or field studies and the atmosphere thus offers a unique perspective on large-scale vegetation drought dynamics. A widely used stomatal conductance parameterization used in our study as well as many current climate models underestimate this observed decrease in carbon and water exchange during droughts (black and blue lines in the figure). The global δ13C record could provide a new opportunity to improve interannual drought dynamics in coupled vegetation-atmosphere models for CO2.

  13. Effects of Carbonyl Sulfide and Carbonic Anhydrase on Stomatal Conductance1[OA

    PubMed Central

    Stimler, Keren; Berry, Joseph A.; Yakir, Dan

    2012-01-01

    The potential use of carbonyl sulfide (COS) as tracer of CO2 flux into the land biosphere stimulated research on COS interactions with leaves during gas exchange. We carried out leaf gas-exchange measurements of COS and CO2 in 22 plant species representing deciduous and evergreen trees, grasses, and shrubs, under a range of light intensities, using mid-infrared laser spectroscopy. A narrow range in the normalized ratio of the net uptake rates of COS (As) and CO2 (Ac), leaf relative uptake (As/Ac × [CO2]/[COS]), was observed, with a mean value of 1.61 ± 0.26, which is advantageous to the use of COS in photosynthesis research. Notably, increasing COS concentrations between 250 and 2,800 pmol mol−1 (enveloping atmospheric levels) enhanced stomatal conductance (gs) to a variable extent in most plants examined (up to a normalized enhancement factor [ fe = (gs-max − gs-min)/gs-min] of 1). This enhancement was completely abolished in carbonic anhydrase (CA)-deficient antisense lines of both C3 and C4 plants. We suggest that the stomatal response is mediated by CA and may involve hydrogen sulfide formed in the reaction of COS and water with CA. In all species examined, the uptake rates of COS and CO2 were highly correlated, but there was no relationship between the sensitivity of stomata to COS and the rate of COS uptake (or, by inference, hydrogen sulfide production). The basis for the observed stomatal sensitivity and its variations is still to be determined. PMID:22106096

  14. Environmental control of stomatal conductance in forest trees of the Great Smoky Mountains National Park.

    PubMed

    Patterson, M C; Samuelson, L; Somers, G; Mays, A

    2000-11-01

    To determine if stomatal conductance (g(s)) of forest trees could be predicted from measures of leaf microclimate, diurnal variability in in situ g(s) was measured in black cherry (Prunus serotina), red maple (Acer rubrum), and northern red oak (Quercus rubra). Relative to overstory trees, understory saplings exhibited little diurnal variability in g(s) and ozone uptake. Depending on species and site, up to 30% of diurnal and seasonal variation in g(s )of overstory trees was explained by photosynthetically active radiation and vapor pressure deficit. Daily maximum g(s) was significantly related to soil moisture in overstory northern red oak and black cherry (R(2) ranged from 33 to 65%). Although g(s) was not fully predicted using instantaneous measures of leaf microclimate, ozone uptake of large forest trees was reduced by low soil moisture. PMID:15092837

  15. Photosynthesis and stomatal conductance related to reflectance on the canopy scale

    NASA Technical Reports Server (NTRS)

    Verma, S. B.; Sellers, P. J.; Walthall, C. L.; Hall, F. G.; Kim, J.; Goetz, S. J.

    1993-01-01

    Field measurements of carbon dioxide and water vapor fluxes were analyzed in conjunction with reflectances obtained from a helicopter-mounted Modular Multiband Radiometer at a grassland study site during the First International Satellite Land Surface Climatology Project Field Experiment. These measurements are representative of the canopy scale and were made over a range of meteorological and soil moisture conditions during different stages in the annual life cycle of the prairie vegetation, and thus provide a good basis for investigating hpotheses/relationships potentially useful in remote sensing applications. We tested the hypothesis (Sellers, 1987) that the simple ratio vegetation index should be near-linearly related to the derivatives of the unstressed canopy stomatal conductance and the unstressed canopy photosynthesis with respect to photosynthetically active radiation. Even though there is some scatter in our data, the results seem to support this hypothesis.

  16. Stomatal response of an anisohydric grapevine cultivar to evaporative demand, available soil moisture and abscisic acid.

    PubMed

    Rogiers, Suzy Y; Greer, Dennis H; Hatfield, Jo M; Hutton, Ron J; Clarke, Simon J; Hutchinson, Paul A; Somers, Anthony

    2012-03-01

    Stomatal responsiveness to evaporative demand (air vapour pressure deficit (VPD)) ranges widely between species and cultivars, and mechanisms for stomatal control in response to VPD remain obscure. The interaction of irrigation and soil moisture with VPD on stomatal conductance is particularly difficult to predict, but nevertheless is critical to instantaneous transpiration and vulnerability to desiccation. Stomatal sensitivity to VPD and soil moisture was investigated in Semillon, an anisohydric Vitis vinifera L. variety whose leaf water potential (Ψ(l)) is frequently lower than that of other grapevine varieties grown under similar conditions in the warm grape-growing regions of Australia. A survey of Semillon vines across seven vineyards revealed that, regardless of irrigation treatment, midday Ψ(l) was dependent on not only soil moisture but VPD at the time of measurement. Predawn Ψ(l) was more closely correlated to not only soil moisture in dry vineyards but to night-time VPD in drip-irrigated vineyards, with incomplete rehydration during high night-time VPD. Daytime stomatal conductance was low only under severe plant water deficits, induced by extremes in dry soil. Stomatal response to VPD was inconsistent across irrigation regime; however, in an unirrigated vineyard, stomatal sensitivity to VPD-the magnitude of stomatal response to VPD-was heightened under dry soils. It was also found that stomatal sensitivity was proportional to the magnitude of stomatal conductance at a reference VPD of 1kPa. Exogenous abscisic acid (ABA) applied to roots of Semillon vines growing in a hydroponic system induced stomatal closure and, in field vines, petiole xylem sap ABA concentrations rose throughout the morning and were higher in vines with low Ψ(l). These data indicate that despite high stomatal conductance of this anisohydric variety when grown in medium to high soil moisture, increased concentrations of ABA as a result of very limited soil moisture may augment

  17. Hydraulic conductance and water potential gradients in squash leaves showing mycorrhiza-induced increases in stomatal conductance.

    PubMed

    Augé, Robert M; Toler, Heather D; Sams, Carl E; Nasim, Ghazala

    2008-03-01

    Stomatal conductance (gs) and transpiration rates vary widely across plant species. Leaf hydraulic conductance (k leaf) tends to change with g (s), to maintain hydraulic homeostasis and prevent wide and potentially harmful fluctuations in transpiration-induced water potential gradients across the leaf (Delta Psi leaf). Because arbuscular mycorrhizal (AM) symbiosis often increases gs in the plant host, we tested whether the symbiosis affects leaf hydraulic homeostasis. Specifically, we tested whether k leaf changes with gs to maintain Delta Psi leaf or whether Delta Psi leaf differs when gs differs in AM and non-AM plants. Colonization of squash plants with Glomus intraradices resulted in increased gs relative to non-AM controls, by an average of 27% under amply watered, unstressed conditions. Stomatal conductance was similar in AM and non-AM plants with exposure to NaCl stress. Across all AM and NaCl treatments, k leaf did change in synchrony with gs (positive correlation of gs and k leaf), corroborating leaf tendency toward hydraulic homeostasis under varying rates of transpirational water loss. However, k leaf did not increase in AM plants to compensate for the higher gs of unstressed AM plants relative to non-AM plants. Consequently, Delta Psi leaf did tend to be higher in AM leaves. A trend toward slightly higher Delta Psi leaf has been observed recently in more highly evolved plant taxa having higher productivity. Higher Delta Psi leaf in leaves of mycorrhizal plants would therefore be consistent with the higher rates of gas exchange that often accompany mycorrhizal symbiosis and that are presumed to be necessary to supply the carbon needs of the fungal symbiont.

  18. The Effect of Drought on Stomatal Conductance in the Biosphere 2 Rainforest

    NASA Astrophysics Data System (ADS)

    Gay, J. D.; Van Haren, J. L. M.

    2015-12-01

    Drought is a major climate change concern for the Earth's rainforests; however little is currently known about how these forests and individual plants will respond to water stress. At the individual level, the ability of plants to regulate their stomatal conductance is an important preservation mechanism that helps to cool leaves, regulate water loss, and uptake carbon dioxide. At the ecosystem level, transpiration in rainforests is a major contributor to the positive feedback loop that returns moisture to the atmosphere for continued precipitation cycles. Nearly 60% of atmospheric moisture in the Amazon rain forests has been traced back to origins of transpiration from its plants. In relation to current climatic conditions, stomatal conductance rates are highly variable across rainforest species and environmental conditions. It is still unknown to what extent these rates will decrease at leaf and forest level in response to periods of drought. The University of Arizona's Biosphere 2 (B2) served as the study site for a simulated 4-week long drought because of its ability to mimic the micrometeorology of an Amazonian rainforest. Three species of plants were chosen at various levels in the canopy: Clitoria racemosa, Cissus sicyoides, and Hibiscus elatus. These plants were selected based on their relative abundance and distribution in the B2 forest. It was revealed that two out of the three species exhibited decreases in H20 efflux at each elevation, while one species (C. racemosa) proved much more resistant, at each elevation, to H20 loss. These results may be useful for future integrative modeling of how individual leaf level responses extend to entire ecosystem scales. It will be important to better understand how rainforests conserve, recycle, and lose water to gauge their response to warming climate, and increased periods of drought in the tropics.

  19. Stomatal Conductance and Sulfur Uptake of Five Clones of Populus tremuloides Exposed to Sulfur Dioxide 1

    PubMed Central

    Kimmerer, Thomas W.; Kozlowski, T. T.

    1981-01-01

    Plants of five clones of Populus tremuloides Michx. were exposed to 0, 0.2 or 0.5 microliter per liter SO2 for 8 hours in controlled environment chambers. In the absence of the pollutant, two pollution-resistant clones maintained consistently lower daytime diffusive conductance (LDC) than did a highly susceptible clone or two moderately resistant clones. Differences in LDC among the latter three clones were not significant. At 0.2 microliter per liter SO2, LDC decreased in the susceptible clone after 8 hours fumigation while the LDC of the other clones was not affected. Fumigation with 0.5 microliter per liter SO2 decreased LDC of all five clones during the fumigation. Rates of recovery following fumigation varied with the clone, but the LDC of all clones had returned to control values by the beginning of the night following fumigation. Night LDC was higher in the susceptible clone than in the other clones. Fumigation for 16 hours (14 hours day + 2 hours night) with 0.4 microliter per liter SO2 decreased night LDC by half. Sulfur uptake studies generally confirmed the results of the conductance measurements. The results show that stomatal conductance is important in determining relative susceptibility of the clones to pollution stress. PMID:16661807

  20. Insights about Stomatal Behavior and Surface Conductance from Globally Distributed Ecosystem Scale Observations (FLUXNET)

    NASA Astrophysics Data System (ADS)

    Williams, C. A.

    2014-12-01

    Surface conductance acts as a key linkage between terrestrial water and carbon balances and strongly influences land surface response to and feedback on the near surface environment (temperature and humidity). Theory suggests optimal stomatal behavior that maximizes carbon gain while minimizing water loss. This is often examined by analysis of Water Use Efficiency (CO2 uptake / H2O loss) from observations of assimilation and transpiration, though is more formally tested with examination of the marginal water cost of plant carbon gain (dE/dA). Plant species and forms are known to vary in their water use habits, with some forms being relatively conservative (e.g trees) and others exhibiting more profligate behavior (e.g. grasses, crops), likely relating to plant hydraulics. Under drought conditions such relations remain little studied though one might expect profligate users to transition toward a more conservative strategy. Globally-distributed observations of ecosystem scale water and carbon fluxes and associated environmental conditions from FLUXNET provide an emerging opportunity to examine the above relationships and theory in hopes of improving ability to characterize surface conductance. This presentation will seek to review recent findings and offer new analysis and synthesis perspectives on plant water use strategies and carbon gain with implications for energy balance, runoff, the Budyko hypothesis.

  1. Implementation of an optimal stomatal conductance model in the Australian Community Climate Earth Systems Simulator (ACCESS1.3b)

    NASA Astrophysics Data System (ADS)

    Kala, J.; De Kauwe, M. G.; Pitman, A. J.; Lorenz, R.; Medlyn, B. E.; Wang, Y.-P.; Lin, Y.-S.; Abramowitz, G.

    2015-07-01

    We implement a new stomatal conductance model, based on the optimality approach, within the Community Atmosphere Biosphere Land Exchange (CABLE) land surface model. Coupled land-atmosphere simulations are then performed using CABLE within the Australian Community Climate and Earth Systems Simulator (ACCESS) with prescribed sea surface temperatures. As in most land surface models, the default stomatal conductance scheme only accounts for differences in model parameters in relation to the photosynthetic pathway, but not in relation to plant functional types. The new scheme allows model parameters to vary by plant functional type, based on a global synthesis of observations of stomatal conductance under different climate regimes over a wide range of species. We show that the new scheme reduces the latent heat flux from the land surface over the boreal forests during the Northern Hemisphere summer by 0.5 to 1.0 mm day-1. This leads to warmer daily maximum and minimum temperatures by up to 1.0 °C and warmer extreme maximum temperatures by up to 1.5 °C. These changes generally improve the climate model's climatology and improve existing biases by 10-20 %. The change in the surface energy balance also affects net primary productivity and the terrestrial carbon balance. We conclude that the improvements in the global climate model which result from the new stomatal scheme, constrained by a global synthesis of experimental data, provide a valuable advance in the long-term development of the ACCESS modelling system.

  2. Maximal stomatal conductance to water and plasticity in stomatal traits differ between native and invasive introduced lineages of Phragmites australis in North America

    PubMed Central

    Douhovnikoff, V.; Taylor, S. H.; Hazelton, E. L. G.; Smith, C. M.; O'Brien, J.

    2016-01-01

    The fitness costs of reproduction by clonal growth can include a limited ability to adapt to environmental and temporal heterogeneity. Paradoxically, some facultatively clonal species are not only able to survive, but colonize, thrive and expand in heterogeneous environments. This is likely due to the capacity for acclimation (sensu stricto) that compensates for the fitness costs and complements the ecological advantages of clonality. Introduced Phragmites australis demonstrates great phenotypic plasticity in response to temperature, nutrient availability, geographic gradient, water depths, habitat fertility, atmospheric CO2, interspecific competition and intraspecific competition for light. However, no in situ comparative subspecies studies have explored the difference in plasticity between the non-invasive native lineage and the highly invasive introduced lineage. Clonality of the native and introduced lineages makes it possible to control for genetic variation, making P. australis a unique system for the comparative study of plasticity. Using previously identified clonal genotypes, we investigated differences in their phenotypic plasticity through measurements of the lengths and densities of stomata on both the abaxial (lower) and adaxial (upper) surfaces of leaves, and synthesized these measurements to estimate impacts on maximum stomatal conductance to water (gwmax). Results demonstrated that at three marsh sites, invasive lineages have consistently greater gwmax than their native congeners, as a result of greater stomatal densities and smaller stomata. Our analysis also suggests that phenotypic plasticity, determined as within-genotype variation in gwmax, of the invasive lineage is similar to, or exceeds, that shown by the native lineage. PMID:26819257

  3. Maximal stomatal conductance to water and plasticity in stomatal traits differ between native and invasive introduced lineages of Phragmites australis in North America.

    PubMed

    Douhovnikoff, V; Taylor, S H; Hazelton, E L G; Smith, C M; O'Brien, J

    2016-01-27

    The fitness costs of reproduction by clonal growth can include a limited ability to adapt to environmental and temporal heterogeneity. Paradoxically, some facultatively clonal species are not only able to survive, but colonize, thrive and expand in heterogeneous environments. This is likely due to the capacity for acclimation (sensu stricto) that compensates for the fitness costs and complements the ecological advantages of clonality. Introduced Phragmites australis demonstrates great phenotypic plasticity in response to temperature, nutrient availability, geographic gradient, water depths, habitat fertility, atmospheric CO2, interspecific competition and intraspecific competition for light. However, no in situ comparative subspecies studies have explored the difference in plasticity between the non-invasive native lineage and the highly invasive introduced lineage. Clonality of the native and introduced lineages makes it possible to control for genetic variation, making P. australis a unique system for the comparative study of plasticity. Using previously identified clonal genotypes, we investigated differences in their phenotypic plasticity through measurements of the lengths and densities of stomata on both the abaxial (lower) and adaxial (upper) surfaces of leaves, and synthesized these measurements to estimate impacts on maximum stomatal conductance to water (gwmax). Results demonstrated that at three marsh sites, invasive lineages have consistently greater gwmax than their native congeners, as a result of greater stomatal densities and smaller stomata. Our analysis also suggests that phenotypic plasticity, determined as within-genotype variation in gwmax, of the invasive lineage is similar to, or exceeds, that shown by the native lineage.

  4. Maximal stomatal conductance to water and plasticity in stomatal traits differ between native and invasive introduced lineages of Phragmites australis in North America.

    PubMed

    Douhovnikoff, V; Taylor, S H; Hazelton, E L G; Smith, C M; O'Brien, J

    2016-01-01

    The fitness costs of reproduction by clonal growth can include a limited ability to adapt to environmental and temporal heterogeneity. Paradoxically, some facultatively clonal species are not only able to survive, but colonize, thrive and expand in heterogeneous environments. This is likely due to the capacity for acclimation (sensu stricto) that compensates for the fitness costs and complements the ecological advantages of clonality. Introduced Phragmites australis demonstrates great phenotypic plasticity in response to temperature, nutrient availability, geographic gradient, water depths, habitat fertility, atmospheric CO2, interspecific competition and intraspecific competition for light. However, no in situ comparative subspecies studies have explored the difference in plasticity between the non-invasive native lineage and the highly invasive introduced lineage. Clonality of the native and introduced lineages makes it possible to control for genetic variation, making P. australis a unique system for the comparative study of plasticity. Using previously identified clonal genotypes, we investigated differences in their phenotypic plasticity through measurements of the lengths and densities of stomata on both the abaxial (lower) and adaxial (upper) surfaces of leaves, and synthesized these measurements to estimate impacts on maximum stomatal conductance to water (gwmax). Results demonstrated that at three marsh sites, invasive lineages have consistently greater gwmax than their native congeners, as a result of greater stomatal densities and smaller stomata. Our analysis also suggests that phenotypic plasticity, determined as within-genotype variation in gwmax, of the invasive lineage is similar to, or exceeds, that shown by the native lineage. PMID:26819257

  5. High precision and continuous measurements of mesophyll and stomatal conductance to CO2 diffusion during photosynthesis using QCL

    NASA Astrophysics Data System (ADS)

    Kodama, N.; Wada, R.; Nakayama, T.; Takemura, K.; Takahashi, K.; Hanba, Y. T.; Matsumi, Y.

    2011-12-01

    The diffusion of CO2 within leaves during photosynthesis can be an important limiting factor for productivity. Mesophyll conductance had been thought to be infinite or constant over the time. Recent studies, however, have revealed that mesophyll conductance is altered by growth environment,and may respond rapidly to some environmental variables such as light and CO2 concentration. Mesophyll conductance has been suggested to be dependent on leaf anatomical and morphological structures, and aquaporin have been proven to play an important role in CO2 transport across cell membranes. In this study we used transgenic Eucalyptus overexpressing radish aquaporin PIP2 to investigate the effect of aquaporin on mesophyll conductance. We hypothesized that stomatal and mesophyll conductance may respond differently to environmental alterations. A mid-infrared laser absorption spectrometer (QCL; Aerodyne research Inc.) was coupled to a photosynthesis system to allow simultaneous measurement of exchange of CO2 and its isotopologues.We found that mesophyll conductance responded more rapidly to alteration of the light intensity compared to stomatal conductance, regardless of aquaporin expression. However, mesophyll conductance was higher in the leaves with higher aquaporin content. The mesophyll response was completed within 5 minutes, considerably faster than the stomatal response to the same perturbation.

  6. Scale effects on the controls on mountain grassland leaf stomatal and ecosystem surface conductance to water vapour

    NASA Astrophysics Data System (ADS)

    Haslwanter, Alois; Hammerle, Albin; Wohlfahrt, Georg

    2010-05-01

    Stomata are the major pathway by which plants exert control on the exchange of trace gases and water vapour with the aerial environment and thus provide a key link between the functioning of terrestrial ecosystems and the state and composition of the atmosphere. Understanding the nature of this control, i.e. how stomatal conductance differs between plant species and ecosystems and how it varies in response to external and internal forcings, is key to predicting feedbacks plants may be providing to changing climatic conditions. Despite a long history of research on stomatal functioning, a fully mechanistic understanding of how stomata function in response to biotic and abiotic controls is still elusive which has led to the development of a large number of (semi-)empirical models of varying complexity. Two of the most widely used models go back to Jarvis (1976) and Ball, Woodrow and Berry (1987), termed J-model and BWB-model, respectively, in the following. The J-model simulates stomatal conductance as some maximal value attenuated by a series of multiplicative functions which are bound between zero and unity, while the BWB-model predicts stomatal conductance as a linear function of photosynthesis, relative humidity and carbon dioxide concentration in the leaf boundary layer. Both models were developed for the prediction of leaf-scale stomatal conductance to water vapour, but have been applied for simulating ecosystem-scale surface conductance as well. The objective of the present paper is to compare leaf- and ecosystem-scale conductances to water vapour and to assess the respective controls using the two above-mentioned models as analysis frameworks. To this end leaf-level stomatal conductance has been measured by means of leaf-gas exchange methods and ecosystem-scale surface conductance by inverting eddy covariance evapotranspiration estimates at a mountain grassland site in Austria. Our major findings are that the proportionality parameter in the BWB-model is

  7. Root hydraulic conductivity and adjustments in stomatal conductance: hydraulic strategy in response to salt stress in a halotolerant species.

    PubMed

    Vitali, Victoria; Bellati, Jorge; Soto, Gabriela; Ayub, Nicolás D; Amodeo, Gabriela

    2015-11-24

    Recent advances at the molecular level are introducing a new scenario that needs to be integrated into the analysis of plant hydraulic properties. Although it is not yet clear to what extent this scenario alters the current proposal for the hydraulic circuit models, it introduces new insights when studying plants that are able to easily overcome water restrictions. In this context, our aim was to explore water adjustments in a halotolerant model (Beta vulgaris) by studying the coordination between the root in terms of root hydraulic conductivity (Lpr) and the shoot as reflected in the stomatal conductance (gs). The root water pathways were also analysed in terms of root suberization (apoplastic barrier) and aquaporin transcript levels (cell-to-cell pathway). Beta vulgaris showed the ability to rapidly lose (4 h) and gain (24 h) turgor when submitted to salt stress (200 mM). The reduction profile observed in Lpr and gs was consistent with a coupled process. The tuning of the root water flow involved small variations in the studied aquaporin's transcripts before anatomical modifications occurred. Exploring Lpr enhancement after halting the stress contributed to show not only a different profile in restoring Lpr but also the capacity to uncouple Lpr from gs. Beta vulgaris root plays a key role and can anticipate water loss before the aerial water status is affected.

  8. Root hydraulic conductivity and adjustments in stomatal conductance: hydraulic strategy in response to salt stress in a halotolerant species.

    PubMed

    Vitali, Victoria; Bellati, Jorge; Soto, Gabriela; Ayub, Nicolás D; Amodeo, Gabriela

    2015-01-01

    Recent advances at the molecular level are introducing a new scenario that needs to be integrated into the analysis of plant hydraulic properties. Although it is not yet clear to what extent this scenario alters the current proposal for the hydraulic circuit models, it introduces new insights when studying plants that are able to easily overcome water restrictions. In this context, our aim was to explore water adjustments in a halotolerant model (Beta vulgaris) by studying the coordination between the root in terms of root hydraulic conductivity (Lpr) and the shoot as reflected in the stomatal conductance (gs). The root water pathways were also analysed in terms of root suberization (apoplastic barrier) and aquaporin transcript levels (cell-to-cell pathway). Beta vulgaris showed the ability to rapidly lose (4 h) and gain (24 h) turgor when submitted to salt stress (200 mM). The reduction profile observed in Lpr and gs was consistent with a coupled process. The tuning of the root water flow involved small variations in the studied aquaporin's transcripts before anatomical modifications occurred. Exploring Lpr enhancement after halting the stress contributed to show not only a different profile in restoring Lpr but also the capacity to uncouple Lpr from gs. Beta vulgaris root plays a key role and can anticipate water loss before the aerial water status is affected. PMID:26602985

  9. Root hydraulic conductivity and adjustments in stomatal conductance: hydraulic strategy in response to salt stress in a halotolerant species

    PubMed Central

    Vitali, Victoria; Bellati, Jorge; Soto, Gabriela; Ayub, Nicolás D.; Amodeo, Gabriela

    2015-01-01

    Recent advances at the molecular level are introducing a new scenario that needs to be integrated into the analysis of plant hydraulic properties. Although it is not yet clear to what extent this scenario alters the current proposal for the hydraulic circuit models, it introduces new insights when studying plants that are able to easily overcome water restrictions. In this context, our aim was to explore water adjustments in a halotolerant model (Beta vulgaris) by studying the coordination between the root in terms of root hydraulic conductivity (Lpr) and the shoot as reflected in the stomatal conductance (gs). The root water pathways were also analysed in terms of root suberization (apoplastic barrier) and aquaporin transcript levels (cell-to-cell pathway). Beta vulgaris showed the ability to rapidly lose (4 h) and gain (24 h) turgor when submitted to salt stress (200 mM). The reduction profile observed in Lpr and gs was consistent with a coupled process. The tuning of the root water flow involved small variations in the studied aquaporin's transcripts before anatomical modifications occurred. Exploring Lpr enhancement after halting the stress contributed to show not only a different profile in restoring Lpr but also the capacity to uncouple Lpr from gs. Beta vulgaris root plays a key role and can anticipate water loss before the aerial water status is affected. PMID:26602985

  10. Stomata-controlled nighttime COS fluxes in a boreal forest: implications for the use of COS as a GPP tracer

    NASA Astrophysics Data System (ADS)

    Kooijmans, Linda M. J.; Maseyk, Kadmiel; Seibt, Ulli; Vesala, Timo; Mammarella, Ivan; Baker, Ian T.; Franchin, Alessandro; Kolari, Pasi; Sun, Wu; Keskinen, Helmi; Levula, Janne; Chen, Huilin

    2016-04-01

    Carbonyl Sulfide (COS) is a promising new tracer that can be used to partition the Net Ecosystem Exchange into gross primary production (GPP) and respiration. COS and CO2 vegetation fluxes are closely related as these gases share the same diffusion pathway into stomata. This close coupling is the fundamental principle for the use of COS as tracer for GPP. Nonetheless, in contrast to CO2 , the uptake of COS by vegetation is not light-dependent, and therefore the vegetative uptake of COS can continue during the night as long as stomata are open. Nighttime stomatal conductance is observed in a variety of studies, and also nighttime depletion of COS concentrations is reported several times but it is not confirmed with field measurements that the depletion of COS in the night is indeed driven by stomatal opening. In the summer of 2015 a campaign took place at the SMEAR II site in Hyytiälä, Finland to provide better constrained COS flux data for boreal forests using a combination of COS measurements, i.e. atmospheric profile concentrations up to 125 m, eddy-covariance fluxes and soil chamber fluxes, and collocated measurements of stomatal conductance and 222Radon. A high correlation between concentrations of 222Radon and COS implies that the radon-tracer method is a valuable tool to derive nighttime ecosystem COS fluxes. We find that soils contribute to 17% of the total ecosystem COS flux during nighttime in the peak growing season. Nighttime ecosystem COS fluxes show a correlation with stomatal conductance (R2 = 0.3), indicating that nighttime COS fluxes are primarily driven by vegetation. The COS vegetation fluxes will be compared with calculated fluxes from the Simple Biosphere model. Furthermore, the nighttime vegetative COS uptake covers a substantial fraction (25%) of the daily maximum COS uptake by vegetation. Accurate quantification of nighttime COS uptake is required to be able to use COS as a useful tracer for GPP.

  11. Does low stomatal conductance or photosynthetic capacity enhance growth at elevated CO2 in Arabidopsis?

    PubMed

    Easlon, Hsien Ming; Carlisle, Eli; McKay, John K; Bloom, Arnold J

    2015-03-01

    The objective of this study was to determine if low stomatal conductance (g) increases growth, nitrate (NO3 (-)) assimilation, and nitrogen (N) utilization at elevated CO2 concentration. Four Arabidopsis (Arabidopsis thaliana) near isogenic lines (NILs) differing in g were grown at ambient and elevated CO2 concentration under low and high NO3 (-) supply as the sole source of N. Although g varied by 32% among NILs at elevated CO2, leaf intercellular CO2 concentration varied by only 4% and genotype had no effect on shoot NO3 (-) concentration in any treatment. Low-g NILs showed the greatest CO2 growth increase under N limitation but had the lowest CO2 growth enhancement under N-sufficient conditions. NILs with the highest and lowest g had similar rates of shoot NO3 (-) assimilation following N deprivation at elevated CO2 concentration. After 5 d of N deprivation, the lowest g NIL had 27% lower maximum carboxylation rate and 23% lower photosynthetic electron transport compared with the highest g NIL. These results suggest that increased growth of low-g NILs under N limitation most likely resulted from more conservative N investment in photosynthetic biochemistry rather than from low g. PMID:25583923

  12. Photosynthesis and stomatal conductance related to reflectance on the canopy scale

    SciTech Connect

    Verma, S.B.; Kim, J. ); Sellers, P.J.; Hall, F.G.; Goetz, S.J. ); Walthall, C.L. )

    1993-04-01

    Field measurements of carbon dioxide and water vapor fluxes were analyzed in conjunction with reflectances obtained from a helicopter-mounted Modular Multiband Radiometer (MMR) at a grassland study site during the First ISLSCP (International Satellite Land Surface Climatology Project) Field Experiment (FIFE). These measurements are representative of the canopy scale and were made over a range of meteorological and soil moisture conditions during different stages in the annual life cycle of the prairie vegetation, and thus provide a good basis for investigating hypotheses/relationships potentially useful in remote sensing applications. The authors tested the hypothesis (Sellers, 1987) that the simple ratio vegetation index (SR) should be near-linearly related to the derivatives of the unstressed canopy stomatal conductance (g[sub c]*) and the unstressed canopy photosynthesis (P[sub c]*) with respect to photosynthetically active radiation (PAR). Even though there is some scatter in the data, the results seem to support this hypothesis. Further investigation, however, is needed before such relationships can be employed in satellite remote sensing applications.

  13. Does low stomatal conductance or photosynthetic capacity enhance growth at elevated CO2 in Arabidopsis?

    PubMed

    Easlon, Hsien Ming; Carlisle, Eli; McKay, John K; Bloom, Arnold J

    2015-03-01

    The objective of this study was to determine if low stomatal conductance (g) increases growth, nitrate (NO3 (-)) assimilation, and nitrogen (N) utilization at elevated CO2 concentration. Four Arabidopsis (Arabidopsis thaliana) near isogenic lines (NILs) differing in g were grown at ambient and elevated CO2 concentration under low and high NO3 (-) supply as the sole source of N. Although g varied by 32% among NILs at elevated CO2, leaf intercellular CO2 concentration varied by only 4% and genotype had no effect on shoot NO3 (-) concentration in any treatment. Low-g NILs showed the greatest CO2 growth increase under N limitation but had the lowest CO2 growth enhancement under N-sufficient conditions. NILs with the highest and lowest g had similar rates of shoot NO3 (-) assimilation following N deprivation at elevated CO2 concentration. After 5 d of N deprivation, the lowest g NIL had 27% lower maximum carboxylation rate and 23% lower photosynthetic electron transport compared with the highest g NIL. These results suggest that increased growth of low-g NILs under N limitation most likely resulted from more conservative N investment in photosynthetic biochemistry rather than from low g.

  14. Epidemiology and etiology of denture stomatitis.

    PubMed

    Gendreau, Linda; Loewy, Zvi G

    2011-06-01

    Denture stomatitis, a common disorder affecting denture wearers, is characterized as inflammation and erythema of the oral mucosal areas covered by the denture. Despite its commonality, the etiology of denture stomatitis is not completely understood. A search of the literature was conducted in the PubMed electronic database (through November 2009) to identify relevant articles for inclusion in a review updating information on the epidemiology and etiology of denture stomatitis and the potential role of denture materials in this disorder. Epidemiological studies report prevalence of denture stomatitis among denture wearers to range from 15% to over 70%. Studies have been conducted among various population samples, and this appears to influence prevalence rates. In general, where reported, incidence of denture stomatitis is higher among elderly denture users and among women. Etiological factors include poor denture hygiene, continual and nighttime wearing of removable dentures, accumulation of denture plaque, and bacterial and yeast contamination of denture surface. In addition, poor-fitting dentures can increase mucosal trauma. All of these factors appear to increase the ability of Candida albicans to colonize both the denture and oral mucosal surfaces, where it acts as an opportunistic pathogen. Antifungal treatment can eradicate C. albicans contamination and relieve stomatitis symptoms, but unless dentures are decontaminated and their cleanliness maintained, stomatitis will recur when antifungal therapy is discontinued. New developments related to denture materials are focusing on means to reduce development of adherent biofilms. These may have value in reducing bacterial and yeast colonization, and could lead to reductions in denture stomatitis with appropriate denture hygiene.

  15. Photosynthesis and stomatal conductance of potato leaves-effects of leaf age, irradiance, and leaf water potential.

    PubMed

    Vos, J; Oyarzún, P J

    1987-01-01

    Potatoes (Solanum tuberosum L., cv. Bintje) were grown in a naturally lit glasshouse. Laboratory measurements on leaves at three insertion levels showed a decline with leaf age in photosynthetic capacity and in stomatal conductance at near saturating irradiance. Conductance declined somewhat more with age than photosynthesis, resulting in a smaller internal CO2 concentration in older relative to younger leaves. Leaves with different insertion number behaved similarly. The changes in photosynthesis rate and in nitrogen content with leaf age were closely correlated. When PAR exceeded circa 100 W m(-2) the rate of photosynthesis and stomatal conductance changed proportionally as indicated by a constant internal CO2 concentration. The photosynthesis-irradiance data were fitted to an asymptotic exponential model. The parameters of the model are AMAX, the rate of photosynthesis at infinite irradiance, and EFF, the slope at low light levels. AMAX declined strongly with leaf age, as did EFF, but to a smaller extent. During drought stress photosynthetic capacity declined directly with decreasing water potential (range -0.6 to -1.1 MPa). Initially, stomatal conductance declined faster than photosynthetic capacity.

  16. Modeling stomatal conductance in the earth system: linking leaf water-use efficiency and water transport along the soil-plant-atmosphere continuum

    NASA Astrophysics Data System (ADS)

    Bonan, G. B.; Williams, M.; Fisher, R. A.; Oleson, K. W.

    2014-09-01

    The Ball-Berry stomatal conductance model is commonly used in earth system models to simulate biotic regulation of evapotranspiration. However, the dependence of stomatal conductance (gs) on vapor pressure deficit (Ds) and soil moisture must be empirically parameterized. We evaluated the Ball-Berry model used in the Community Land Model version 4.5 (CLM4.5) and an alternative stomatal conductance model that links leaf gas exchange, plant hydraulic constraints, and the soil-plant-atmosphere continuum (SPA). The SPA model simulates stomatal conductance numerically by (1) optimizing photosynthetic carbon gain per unit water loss while (2) constraining stomatal opening to prevent leaf water potential from dropping below a critical minimum. We evaluated two optimization algorithms: intrinsic water-use efficiency (ΔAn /Δgs, the marginal carbon gain of stomatal opening) and water-use efficiency (ΔAn /ΔEl, the marginal carbon gain of transpiration water loss). We implemented the stomatal models in a multi-layer plant canopy model to resolve profiles of gas exchange, leaf water potential, and plant hydraulics within the canopy, and evaluated the simulations using leaf analyses, eddy covariance fluxes at six forest sites, and parameter sensitivity analyses. The primary differences among stomatal models relate to soil moisture stress and vapor pressure deficit responses. Without soil moisture stress, the performance of the SPA stomatal model was comparable to or slightly better than the CLM Ball-Berry model in flux tower simulations, but was significantly better than the CLM Ball-Berry model when there was soil moisture stress. Functional dependence of gs on soil moisture emerged from water flow along the soil-to-leaf pathway rather than being imposed a priori, as in the CLM Ball-Berry model. Similar functional dependence of gs on Ds emerged from the ΔAn/ΔEl optimization, but not the ΔAn /gs optimization. Two parameters (stomatal efficiency and root hydraulic

  17. Detecting the Differences in Responses of Stomatal Conductance to Moisture Stresses between Deciduous Shrubs and Artemisia Subshrubs

    PubMed Central

    Gao, Qiong; Yu, Mei; Zhou, Chan

    2013-01-01

    Shrubs and subshrubs can tolerate wider ranges of moisture stresses in both soil and air than other plant life forms, and thus represent greater nonlinearity and uncertainty in ecosystem physiology. The objectives of this paper are to model shrub/subshrub stomatal conductance by synthesizing the field leaf gas exchanges data of 24 species in China, in order to detect the differences between deciduous shrubs and Artemisia subshrubs in their responses of stomatal conductance to changes in the moisture stresses. We revised a model of stomatal conductance by incorporating the tradeoff between xylem hydraulic efficiency and cavitation loss risk. We then fit the model at the three hierarchical levels: global (pooling all data as a single group), three functional groups (deciduous non-legume shrubs, deciduous legume shrubs, and subshrubs in Artemisia genus), and individual observations (species × sites). Bayesian inference with Markov Chain Monte Carlo method was applied to obtain the model parameters at the three levels. We found that the model at the level of functional groups is a significant improvement over that at the global level, indicating the significant differences in the stomatal behavior among the three functional groups. The differences in tolerance and sensitivities to changes in moisture stresses are the most evident between the shrubs and the subshrubs: The two shrub groups can tolerate much higher soil water stress than the subshrubs. The analysis at the observation level is also a significant improvement over that at the functional group level, indicating great variations within each group. Our analysis offered a clue for the equivocal issue of shrub encroachment into grasslands: While the invasion by the shrubs may be irreversible, the dominance of subshrubs, due to their lower resistance and tolerance to moisture stresses, may be put down by appropriate grassland management. PMID:24386351

  18. Phototropins but not cryptochromes mediate the blue light-specific promotion of stomatal conductance, while both enhance photosynthesis and transpiration under full sunlight.

    PubMed

    Boccalandro, Hernán E; Giordano, Carla V; Ploschuk, Edmundo L; Piccoli, Patricia N; Bottini, Rubén; Casal, Jorge J

    2012-03-01

    Leaf epidermal peels of Arabidopsis (Arabidopsis thaliana) mutants lacking either phototropins 1 and 2 (phot1 and phot2) or cryptochromes 1 and 2 (cry1 and cry2) exposed to a background of red light show severely impaired stomatal opening responses to blue light. Since phot and cry are UV-A/blue light photoreceptors, they may be involved in the perception of the blue light-specific signal that induces the aperture of the stomatal pores. In leaf epidermal peels, the blue light-specific effect saturates at low irradiances; therefore, it is considered to operate mainly under the low irradiance of dawn, dusk, or deep canopies. Conversely, we show that both phot1 phot2 and cry1 cry2 have reduced stomatal conductance, transpiration, and photosynthesis, particularly under the high irradiance of full sunlight at midday. These mutants show compromised responses of stomatal conductance to irradiance. However, the effects of phot and cry on photosynthesis were largely nonstomatic. While the stomatal conductance phenotype of phot1 phot2 was blue light specific, cry1 cry2 showed reduced stomatal conductance not only in response to blue light, but also in response to red light. The levels of abscisic acid were elevated in cry1 cry2. We conclude that considering their effects at high irradiances cry and phot are critical for the control of transpiration and photosynthesis rates in the field. The effects of cry on stomatal conductance are largely indirect and involve the control of abscisic acid levels.

  19. Is optimality in stomatal conductance an endogenous process or an emergent property arising from interactions with the environment?

    NASA Astrophysics Data System (ADS)

    Resco de Dios, Victor; Gessler, Arthur; Ferrio, Juan Pedro; Bahn, Michael; Milcu, Alexandru; Tissue, David; Voltas, Jordi; Roy, Jacques

    2016-04-01

    Plants are sessile and poikilothermic organisms that need to respond and adjust promptly to an ever-changing environment. Over a single 24 h period, a plant may experience the same level of variation in radiation as in its entire life-time and, in some climates, the oscillation in day-night temperature and vapor pressure deficit might be of similar magnitude to that experienced across a full year. Plants need to maintain a positive C balance without depleting soil water reserves in the face of such a diverse environment, and feedbacks between assimilation (A) and water losses (E) are thought to have evolved to optimize stomatal conductance (gs). In short, the optimal conductance hypothesis proposes that cross-talks between A and stomatal conductance gs lead to a constant marginal water use (λ) during a day, such that A is maximized and E minimized. The biological mechanism by which biochemical processes would feedback gs remains unknown, but multiple studies have shown empirical support for this hypothesis, leading to its current consideration of theory by many. Here we test whether optimal stomatal conductance is an endogenous property, that is, driven solely by factors internal to the plant, and in the absence of environmental fluctuations. After 5 days of entrainment, where monoculture canopies of bean and of cotton were subjected to the average environmental conditions of an August sunny day in Montpellier (at the CNRS European Ecotron, FR), we kept temperature, relative humidity and photosynthetically active radiation constant for 48 h at the values observed at noon. During this period, we monitored leaf gas exchange continuously every two minutes, and canopy gas exchange every 15 minutes. We observed a periodic oscillation in λ, showing a 24 h period, and consistent with a circadian regulation of water use efficiency. Hourly variations in λ could thus not be explained by the optimal stomatal hypothesis. Moreover, the pattern of variation (of maximal water

  20. Nighttime transpiration is highly variable within a tallgrass prairie community

    NASA Astrophysics Data System (ADS)

    O'Keefe, K.; Nippert, J. B.

    2014-12-01

    Nighttime transpiration may have significant consequences on plant functioning and earth-atmosphere water fluxes, yet little is known about how this process can vary among species or with environmental changes, particularly in grassland ecosystems. We measured leaf-level nighttime transpiration and daytime photosynthetic rates, as well as whole-plant sap flow rates on eight grass, forb and shrub species in a Kansas tallgrass prairie. Measurements were made periodically across a single growing season (May-August 2014) on three C4 grasses (Andropogon gerardii, Sorghastrum nutans and Panicum virgatum), two C3 forbs (Vernonia baldwinii and Solidago canidensis), and three C3 shrubs (Cornus drummondii, Rhus glabra and Amorpha canescens). At the leaf level, nighttime transpiration rates varied among species and across the growing season. Nighttime transpiration was greater in the three grass species compared to the forbs and shrubs early in the growing season. As the growing season progressed, nighttime transpiration increased and then decreased in all species. These results are consistent with patterns of decreasing daytime stomatal conductance and photosynthetic rates as the growing season became hotter and drier. Nighttime sap flow rates also varied among species and typically accounted for over 10% of total daily water flux at the whole-plant level. These results show that nighttime transpiration is species specific and variable at a small spatial scale. Nighttime transpiration can therefore be a significant portion of a plant water budget in a tallgrass prairie, is highly variable within a community, and is dynamic in response to changing environmental conditions. Forecasts of future ecosystem responses to a changing climate must account for plant water use and loss at night.

  1. Interannual consistency in canopy stomatal conductance control of leaf water potential across seven tree species.

    PubMed

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

    2007-01-01

    We investigated interannual variability of canopy transpiration per unit ground area (E (C)) and per unit leaf area (E (L)) across seven tree species in northern Wisconsin over two years. These species have previously been shown to be sufficient to upscale stand-level transpiration to the landscape level during one growing season. Our objective was to test whether a simple plant hydraulic model could capture interannual variation in transpiration. Three species, wetland balsam fir (Abies balsamea (L.) Mill), basswood (Tilia Americana L.) and speckled alder (Alnus rugosa (DuRoi) Spreng), had no change in E (C) or E (L) between 2000 and 2001. Red pine (Pinus resinosa Ait) had a 57 and 19% increase in E (C) and E (L), respectively, and sugar maple (Acer saccharum Marsh) had an 83 and 41% increase in E (C) and E (L), respectively, from 2000 to 2001. Quaking aspen (Populus tremuloides Michx) had a 50 and 21% decrease in E (C) and E (L), respectively, from 2000 to 2001 in response to complete defoliation by forest tent caterpillar (Malascoma distria Hüber) and subsequent lower total leaf area index of the reflushed foliage. White cedar (Thuja occidentalis L.) had a 20% decrease in both E (C) and E (L) caused by lowered surface water in wetlands in 2001 because of lower precipitation and wetland flow management. Upland A. balsamea increased E (L) and E (C) by 55 and 53%, respectively, as a result of release from light competition of the defoliated, overstory P. tremuloides. We hypothesized that regardless of different drivers of interannual variability in E (C) and E (L), minimum leaf water potential would be regulated at the same value. Minimum midday water potentials were consistent over the two years within each of the seven species despite large changes in transpiration between years. This regulation was independently verified by the exponential saturation between daily E (C) and vapor pressure deficit (D) and the tradeoff between a reference canopy stomatal

  2. Tree level hydrodynamic approach for resolving aboveground water storage and stomatal conductance and modeling the effects of tree hydraulic strategy

    NASA Astrophysics Data System (ADS)

    Mirfenderesgi, Golnazalsadat; Bohrer, Gil; Matheny, Ashley M.; Fatichi, Simone; Moraes Frasson, Renato Prata; Schäfer, Karina V. R.

    2016-07-01

    The finite difference ecosystem-scale tree crown hydrodynamics model version 2 (FETCH2) is a tree-scale hydrodynamic model of transpiration. The FETCH2 model employs a finite difference numerical methodology and a simplified single-beam conduit system to explicitly resolve xylem water potentials throughout the vertical extent of a tree. Empirical equations relate water potential within the stem to stomatal conductance of the leaves at each height throughout the crown. While highly simplified, this approach brings additional realism to the simulation of transpiration by linking stomatal responses to stem water potential rather than directly to soil moisture, as is currently the case in the majority of land surface models. FETCH2 accounts for plant hydraulic traits, such as the degree of anisohydric/isohydric response of stomata, maximal xylem conductivity, vertical distribution of leaf area, and maximal and minimal xylem water content. We used FETCH2 along with sap flow and eddy covariance data sets collected from a mixed plot of two genera (oak/pine) in Silas Little Experimental Forest, NJ, USA, to conduct an analysis of the intergeneric variation of hydraulic strategies and their effects on diurnal and seasonal transpiration dynamics. We define these strategies through the parameters that describe the genus level transpiration and xylem conductivity responses to changes in stem water potential. Our evaluation revealed that FETCH2 considerably improved the simulation of ecosystem transpiration and latent heat flux in comparison to more conventional models. A virtual experiment showed that the model was able to capture the effect of hydraulic strategies such as isohydric/anisohydric behavior on stomatal conductance under different soil-water availability conditions.

  3. Environmental controls on saltcedar (Tamarix spp.) transpiration and stomatal conductance and implications for determining evapotranspiration by remote sensing

    NASA Astrophysics Data System (ADS)

    Nagler, P. L.; Glenn, E. P.; morino, K.

    2012-12-01

    Saltcedar is an introduced, salt-tolerant shrub that now dominates many flow-regulated western U.S. rivers. Saltcedar control programs have been implemented to salvage water and to allow the return of native vegetation to infested rivers. However, there is much debate about how much water saltcedar actually uses and the range of ecohydrological niches it occupies. Ground methods for measuring riparian zone ET have improved and there is considerable interest in developing remote sensing methods for saltcedar to conduct wide-area monitoring of water use. Both thermal band and vegetation index methods have been used to estimate riparian ET. However, several problems present themselves in applying existing remote sensing methods to riparian corridors. First, many riparian corridors are narrow and are surrounded by arid uplands, hence they cannot be treated as energetically closed systems, an assumption of thermal band methods that calculate ET as a residual in the surface energy balance. Second, contrary to the assumption that riparian phreatophytes typically grow under unstressed conditions since they are rooted into groundwater, we find that saltcedar stands are under substantial degrees of apparent moisture stress, exhibiting midday depression of transpiration and stomatal conductance, and decreases in stomatal conductance over the growing season as depth to groundwater increases. Furthermore, the degree of stress is site-specific, depending on local soil texture, salinity of the groundwater and distance from the river. This violates a key assumption of vegetation index methods for estimating ET. The implications of these findings for arid-zone riparian ecohydrology and for remote sensing methods that assume either a constant daily evaporative fraction or rate of stomatal conductance will be discussed using saltcedar stands measured in the Cibola NWR on the lower Colorado River as a case study. Daily rates of saltcedar transpiration ranged from 1.6-3.0 mm/m2 leaf

  4. Modeling stomatal conductance in the Earth system: linking leaf water-use efficiency and water transport along the soil-plant-atmosphere continuum

    NASA Astrophysics Data System (ADS)

    Bonan, G. B.; Williams, M.; Fisher, R. A.; Oleson, K. W.

    2014-05-01

    The empirical Ball-Berry stomatal conductance model is commonly used in Earth system models to simulate biotic regulation of evapotranspiration. However, the dependence of stomatal conductance (gs) on vapor pressure deficit (Ds) and soil moisture must both be empirically parameterized. We evaluated the Ball-Berry model used in the Community Land Model version 4.5 (CLM4.5) and an alternative stomatal conductance model that links leaf gas exchange, plant hydraulic constraints, and the soil-plant-atmosphere continuum (SPA) to numerically optimize photosynthetic carbon gain per unit water loss while preventing leaf water potential dropping below a critical minimum level. We evaluated two alternative optimization algorithms: intrinsic water-use efficiency (Δ An/Δ gs, the marginal carbon gain of stomatal opening) and water-use efficiency (Δ An/Δ El, the marginal carbon gain of water loss). We implemented the stomatal models in a multi-layer plant canopy model, to resolve profiles of gas exchange, leaf water potential, and plant hydraulics within the canopy, and evaluated the simulations using: (1) leaf analyses; (2) canopy net radiation, sensible heat flux, latent heat flux, and gross primary production at six AmeriFlux sites spanning 51 site-years; and (3) parameter sensitivity analyses. Without soil moisture stress, the performance of the SPA stomatal conductance model was generally comparable to or somewhat better than the Ball-Berry model in flux tower simulations, but was significantly better than the Ball-Berry model when there was soil moisture stress. Functional dependence of gs on soil moisture emerged from the physiological theory linking leaf water-use efficiency and water flow to and from the leaf along the soil-to-leaf pathway rather than being imposed a priori, as in the Ball-Berry model. Similar functional dependence of gs on Ds emerged from the water-use efficiency optimization. Sensitivity analyses showed that two parameters (stomatal efficiency and

  5. Microclimatological and Physiological Controls of Stomatal Conductance and Transpiration of Co-Occurring Seedlings with Varying Shade Tolerance

    NASA Astrophysics Data System (ADS)

    Siegert, C. M.; Levia, D. F.

    2010-12-01

    Forest ecosystems provide a significant portion of fresh water to the hydrologic cycle through transpiration, the majority of which is supplied by saplings and mature trees. However, a smaller, yet measurable, proportion is also supplied by seedlings. The contribution of seedlings is dependent upon physiological characteristics of the species, whose range of habitat is ultimately controlled by microclimate. The objectives of this study were to (1) observe meteorological conditions of two forest microlimates and (2) assess the intra- and interspecific stomatal conductance and transpiration responses of naturally occurring seedlings of varying shade tolerance. Naturally established seedlings in a deciduous forest understory and an adjacent clearing were monitored throughout the 2008 growing season in southeastern Pennsylvania (39°49'N, 75°43'W). Clear spatial and temporal trends of stomatal conductance and transpiration were observed throughout this study. The understory microclimate conditions overall had a lower degree of variability and had consistently lower mean quantum flux density, air temperature, vapor pressure deficit, volumetric water content, and soil temperature than the clearing plot. Shade tolerant understory seedlings (Fagus grandifolia Ehrh. (American beech) and Prunus serotina L. (black cherry)) had significantly lower mean monthly rates of water loss (p = 0.05) than shade intolerant clearing seedlings (P. serotina and Liriodendron tulipifera L. (yellow poplar)). Additionally, water loss by shade grown P. serotina was significantly lower (p = 0.05) than by sun grown P. serotina. Significant intraspecific responses (p = 0.05) were also observed on a monthly basis, with the exception of L. tulipifera. These findings indicate that physiological differences, specifically shade tolerance, play an important role in determining rates of stomatal conductance and transpiration in tree seedlings. To a lesser degree, microclimate variability was also shown

  6. 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

  7. Non-hydraulic signals from maize roots in drying soil: inhibition of leaf elongation but not stomatal conductance.

    PubMed

    Saab, I N; Sharp, R E

    1989-11-01

    Conditions of soil drying and plant growth that lead to non-hydraulic inhibition of leaf elongation and stomatal conductance in maize (Zea mays L.) were investigated using plants grown with their root systems divided between two containers. The soil in one container was allowed to dry while the other container was kept well-watered. Soil drying resulted in a maximum 35% inhibition of leaf elongation rate which occurred during the light hours, with no measurable decline in leaf water potential (ψw). Leaf area was 15% less than in control plants after 18 d of soil drying. The inhibition of elongation was observed only when the soil ψw declined to below that of the leaves and, thus, the drying soil no longer contributed to transpiration. However, midday root ψw in the dry container (-0.29 MPa) remained much higher than that of the surrounding soil (-1.0 MPa) after 15 d of drying, indicating that the roots in drying soil were rehydrated in the dark.To prove that the inhibition of leaf elongation was not caused by undetectable changes in leaf water status as a result of loss of half the watergathering capacity, one-half of the root system of control plants was excised. This treatment had no effect on leaf elongation or stomatal conductance. The inhibition of leaf elongation was also not explained by reductions in nutrient supply.Soil drying had no effect on stomatal conductance despite variations in the rate or extent of soild drying, light, humidity or nutrition. The results indicate that non-hydraulic inhibition of leaf elongation may act to conserve water as the soil dries before the occurrence of shoot water deficits. PMID:24201770

  8. Midday stomatal conductance is more related to stem rather than leaf water status in subtropical deciduous and evergreen broadleaf trees.

    PubMed

    Zhang, Yong-Jiang; Meinzer, Frederick C; Qi, Jin-Hua; Goldstein, Guillermo; Cao, Kun-Fang

    2013-01-01

    Midday depressions in stomatal conductance (g(s) ) and photosynthesis are common in plants. The aim of this study was to understand the hydraulic determinants of midday g(s) , the coordination between leaf and stem hydraulics and whether regulation of midday g(s) differed between deciduous and evergreen broadleaf tree species in a subtropical cloud forest of Southwest (SW) China. We investigated leaf and stem hydraulics, midday leaf and stem water potentials, as well as midday g(s) of co-occurring deciduous and evergreen tree species. Midday g(s) was correlated positively with midday stem water potential across both groups of species, but not with midday leaf water potential. Species with higher stem hydraulic conductivity and greater daily reliance on stem hydraulic capacitance were able to maintain higher stem water potential and higher g(s) at midday. Deciduous species exhibited significantly higher stem hydraulic conductivity, greater reliance on stem capacitance, higher stem water potential and g(s) at midday than evergreen species. Our results suggest that midday g(s) is more associated with midday stem than with leaf water status, and that the functional significance of stomatal regulation in these broadleaf tree species is probably for preventing stem xylem dysfunction.

  9. Implementation of an optimal stomatal conductance scheme in the Australian Community Climate Earth Systems Simulator (ACCESS1.3b)

    NASA Astrophysics Data System (ADS)

    Kala, J.; De Kauwe, M. G.; Pitman, A. J.; Lorenz, R.; Medlyn, B. E.; Wang, Y.-P.; Lin, Y.-S.; Abramowitz, G.

    2015-12-01

    We implement a new stomatal conductance scheme, based on the optimality approach, within the Community Atmosphere Biosphere Land Exchange (CABLEv2.0.1) land surface model. Coupled land-atmosphere simulations are then performed using CABLEv2.0.1 within the Australian Community Climate and Earth Systems Simulator (ACCESSv1.3b) with prescribed sea surface temperatures. As in most land surface models, the default stomatal conductance scheme only accounts for differences in model parameters in relation to the photosynthetic pathway but not in relation to plant functional types. The new scheme allows model parameters to vary by plant functional type, based on a global synthesis of observations of stomatal conductance under different climate regimes over a wide range of species. We show that the new scheme reduces the latent heat flux from the land surface over the boreal forests during the Northern Hemisphere summer by 0.5-1.0 mm day-1. This leads to warmer daily maximum and minimum temperatures by up to 1.0 °C and warmer extreme maximum temperatures by up to 1.5 °C. These changes generally improve the climate model's climatology of warm extremes and improve existing biases by 10-20 %. The bias in minimum temperatures is however degraded but, overall, this is outweighed by the improvement in maximum temperatures as there is a net improvement in the diurnal temperature range in this region. In other regions such as parts of South and North America where ACCESSv1.3b has known large positive biases in both maximum and minimum temperatures (~ 5 to 10 °C), the new scheme degrades this bias by up to 1 °C. We conclude that, although several large biases remain in ACCESSv1.3b for temperature extremes, the improvements in the global climate model over large parts of the boreal forests during the Northern Hemisphere summer which result from the new stomatal scheme, constrained by a global synthesis of experimental data, provide a valuable advance in the long-term development

  10. Ecophysiological parameters for a coupled photosynthesis and stomatal conductance model derived from eddy covariance measurements in Asia

    NASA Astrophysics Data System (ADS)

    Ueyama, M.; Ichii, K.; Kobayashi, H.; Alberto, M. C. R.; Bret-Harte, M. S.; Edgar, C.; Euskirchen, E. S.; Harazono, Y.; Hirano, T.; Hirata, R.; Ide, R.; Kosugi, Y.; Machimura, T.; Mizoguchi, Y.; Ohta, T.; Ono, K.; Saigusa, N.; Saitoh, T. M.; Takagi, K.; Takanashi, S.; Zhang, Y.

    2015-12-01

    For better understanding carbon and water vapor fluxes in Asia, ecophysiological parameters of a coupled photosynthesis and stomatal conductance big-leaf model (Farquhar et al., 1980; Ball and Berry, 1987) were inversely estimated using micrometeorological data at 48 sites in Asia. The data covered various ecosystems of arctic tundra, boreal, temperate, and tropical forests, grasslands, and croplands. We applied a global optimization method; shuffled complex evolution (SCE-UA) method (Duan et al., 1993). First stomatal conductance parameters (m and b in the Ball-Berry model) were optimized for evapotranspiration, and then photosynthetic parameters (maximum carboxylation rate at 25oC; Vcmax25) were optimized for gross primarily productivity (GPP). The canopy-scale parameters were then downscaled into the leaf-scale using a two-leaf radiative transfer models and leaf area index (LAI) by MODIS. In the presentation, we will show the spatial variability of the ecophysiological parameters in terms of environmental gradients, and ecosystem types. Implications and limitations of the synthesis will be discussed. References Ball and Berry, 1987: Progress in Photosynthesis Research, pp 221-224. Duan et al., 1993: J. Optimization Theory and Applications, 76, 501-521. Farquhar et al., 1980: Planta, 149, 78-90.

  11. Photocontrol of the Functional Coupling between Photosynthesis and Stomatal Conductance in the Intact Leaf : Blue Light and Par-Dependent Photosystems in Guard Cells.

    PubMed

    Zeiger, E; Field, C

    1982-08-01

    The photocontrol of the functional coupling between photosynthesis and stomatal conductance in the leaf was investigated in gas exchange experiments using monochromatic light provided by lasers. Net photosynthesis and stomatal conductance were measured in attached leaves of Malva parviflora L. as a function of photon irradiance at 457.9 and 640.0 nanometers.Photosynthetic rates and quantum yields of photosynthesis were higher under red light than under blue, on an absorbed or incident basis.Stomatal conductance was higher under blue than under red light at all intensities. Based on a calculated apparent photon efficiency of conductance, blue and red light had similar effects on conductance at intensities higher than 0.02 millimoles per square meter per second, but blue light was several-fold more efficient at very low photon irradiances. Red light had no effect on conductance at photon irradiances below 0.02 millimoles per square meter per second. These observations support the hypothesis that stomatal conductance is modulated by two photosystems: a blue light-dependent one, driving stomatal opening at low light intensities and a photosynthetically active radiation (PAR)-dependent one operating at higher irradiances.When low intensity blue light was used to illuminate a leaf already irradiated with high intensity, 640 nanometers light, the leaf exhibited substantial increases in stomatal conductance. Net photosynthesis changed only slightly. Additional far-red light increased net photosynthesis without affecting stomatal conductance. These observations indicate that under conditions where the PAR-dependent system is driven by high intensity red light, the blue light-dependent system has an additive effect on stomatal conductance.The wavelength dependence of photosynthesis and stomatal conductance demonstrates that these processes are not obligatorily coupled and can be controlled by light, independent of prevailing levels of intercellular CO(2). The blue light

  12. Evapotranspiration partitioning, stomatal conductance, and components of the water balance: A special case of a desert ecosystem in China

    NASA Astrophysics Data System (ADS)

    Zhao, Wenzhi; Liu, Bing; Chang, Xuexiang; Yang, Qiyue; Yang, Yuting; Liu, Zhiling; Cleverly, James; Eamus, Derek

    2016-07-01

    Partitioning evapotranspiration (ET) into its components reveals details of the processes that underlie ecosystem hydrologic budgets and their feedback to the water cycle. We measured rates of actual evapotranspiration (ETa), canopy transpiration (Tc), soil evaporation (Eg), canopy-intercepted precipitation (EI), and patterns of stomatal conductance of the desert shrub Calligonum mongolicum in northern China to determine the water balance of this ecosystem. The ETa was 251 ± 8 mm during the growing period, while EI, Tc, and Eg accounted for 3.2%, 63.9%, and 31.3%, respectively, of total water use (256 ± 4 mm) during the growing period. In this unique ecosystem, groundwater was the main water source for plant transpiration and soil evaporation, Tc and exceeded 60% of the total annual water used by desert plants. ET was not sensitive to air temperature in this unique desert ecosystem. Partitioning ET into its components improves our understanding of the mechanisms that underlie adaptation of desert shrubs, especially the role of stomatal regulation of Tc as a determinant of ecosystem water balance.

  13. Leaf hydraulic conductance, measured in situ, declines and recovers daily: leaf hydraulics, water potential and stomatal conductance in four temperate and three tropical tree species.

    PubMed

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

    2009-07-01

    Adequate leaf hydraulic conductance (Kleaf) is critical for preventing transpiration-induced desiccation and subsequent stomatal closure that would restrict carbon gain. A few studies have reported midday depression of Kleaf (or petiole conductivity) and its subsequent recovery in situ, but the extent to which this phenomenon is universal is not known. The objectives of this study were to measure Kleaf, using a rehydration kinetics method, (1) in the laboratory (under controlled conditions) across a range of water potentials to construct vulnerability curves (VC) and (2) over the course of the day in the field along with leaf water potential and stomatal conductance (gs). Two broadleaf (one evergreen, Arbutus menziesii Pursh., and one deciduous, Quercus garryana Dougl.) and two coniferous species (Pinus ponderosa Dougl. and Pseudotsuga menziesii [Mirbel]) were chosen as representative of different plant types. In addition, Kleaf in the laboratory and leaf water potential in the field were measured for three tropical evergreen species (Protium panamense (Rose), Tachigalia versicolor Standley and L.O. Williams and Vochysia ferruginea Mart) to predict their daily changes in field Kleaf in situ. It was hypothesized that in the field, leaves would close their stomata at water potential thresholds at which Kleaf begins to decline sharply in laboratory-generated VC, thus preventing substantial losses of Kleaf. The temperate species showed a 15-66% decline in Kleaf by midday, before stomatal closure. Although there were substantial midday declines in Kleaf, recovery was nearly complete by late afternoon. Stomatal conductance began to decrease in Pseudotsuga, Pinus and Quercus once Kleaf began to decline; however, there was no detectable reduction in gs in Arbutus. Predicted Kleaf in the tropical species, based on laboratory-generated VC, decreased by 74% of maximum Kleaf in Tachigalia, but only 22-32% in Vochysia and Protium. The results presented here, from the previous

  14. Scaling up stomatal conductance from leaf to canopy using a dual-leaf model for estimating crop evapotranspiration.

    PubMed

    Ding, Risheng; Kang, Shaozhong; Du, Taisheng; Hao, Xinmei; Zhang, Yanqun

    2014-01-01

    The dual-source Shuttleworth-Wallace model has been widely used to estimate and partition crop evapotranspiration (λET). Canopy stomatal conductance (Gsc), an essential parameter of the model, is often calculated by scaling up leaf stomatal conductance, considering the canopy as one single leaf in a so-called "big-leaf" model. However, Gsc can be overestimated or underestimated depending on leaf area index level in the big-leaf model, due to a non-linear stomatal response to light. A dual-leaf model, scaling up Gsc from leaf to canopy, was developed in this study. The non-linear stomata-light relationship was incorporated by dividing the canopy into sunlit and shaded fractions and calculating each fraction separately according to absorbed irradiances. The model includes: (1) the absorbed irradiance, determined by separately integrating the sunlit and shaded leaves with consideration of both beam and diffuse radiation; (2) leaf area for the sunlit and shaded fractions; and (3) a leaf conductance model that accounts for the response of stomata to PAR, vapor pressure deficit and available soil water. In contrast to the significant errors of Gsc in the big-leaf model, the predicted Gsc using the dual-leaf model had a high degree of data-model agreement; the slope of the linear regression between daytime predictions and measurements was 1.01 (R2 = 0.98), with RMSE of 0.6120 mm s-1 for four clear-sky days in different growth stages. The estimates of half-hourly λET using the dual-source dual-leaf model (DSDL) agreed well with measurements and the error was within 5% during two growing seasons of maize with differing hydrometeorological and management strategies. Moreover, the estimates of soil evaporation using the DSDL model closely matched actual measurements. Our results indicate that the DSDL model can produce more accurate estimation of Gsc and λET, compared to the big-leaf model, and thus is an effective alternative approach for estimating and partitioning

  15. Scaling up stomatal conductance from leaf to canopy using a dual-leaf model for estimating crop evapotranspiration.

    PubMed

    Ding, Risheng; Kang, Shaozhong; Du, Taisheng; Hao, Xinmei; Zhang, Yanqun

    2014-01-01

    The dual-source Shuttleworth-Wallace model has been widely used to estimate and partition crop evapotranspiration (λET). Canopy stomatal conductance (Gsc), an essential parameter of the model, is often calculated by scaling up leaf stomatal conductance, considering the canopy as one single leaf in a so-called "big-leaf" model. However, Gsc can be overestimated or underestimated depending on leaf area index level in the big-leaf model, due to a non-linear stomatal response to light. A dual-leaf model, scaling up Gsc from leaf to canopy, was developed in this study. The non-linear stomata-light relationship was incorporated by dividing the canopy into sunlit and shaded fractions and calculating each fraction separately according to absorbed irradiances. The model includes: (1) the absorbed irradiance, determined by separately integrating the sunlit and shaded leaves with consideration of both beam and diffuse radiation; (2) leaf area for the sunlit and shaded fractions; and (3) a leaf conductance model that accounts for the response of stomata to PAR, vapor pressure deficit and available soil water. In contrast to the significant errors of Gsc in the big-leaf model, the predicted Gsc using the dual-leaf model had a high degree of data-model agreement; the slope of the linear regression between daytime predictions and measurements was 1.01 (R2 = 0.98), with RMSE of 0.6120 mm s-1 for four clear-sky days in different growth stages. The estimates of half-hourly λET using the dual-source dual-leaf model (DSDL) agreed well with measurements and the error was within 5% during two growing seasons of maize with differing hydrometeorological and management strategies. Moreover, the estimates of soil evaporation using the DSDL model closely matched actual measurements. Our results indicate that the DSDL model can produce more accurate estimation of Gsc and λET, compared to the big-leaf model, and thus is an effective alternative approach for estimating and partitioning λET.

  16. Scaling Up Stomatal Conductance from Leaf to Canopy Using a Dual-Leaf Model for Estimating Crop Evapotranspiration

    PubMed Central

    Ding, Risheng; Kang, Shaozhong; Du, Taisheng; Hao, Xinmei; Zhang, Yanqun

    2014-01-01

    The dual-source Shuttleworth-Wallace model has been widely used to estimate and partition crop evapotranspiration (λET). Canopy stomatal conductance (Gsc), an essential parameter of the model, is often calculated by scaling up leaf stomatal conductance, considering the canopy as one single leaf in a so-called “big-leaf” model. However, Gsc can be overestimated or underestimated depending on leaf area index level in the big-leaf model, due to a non-linear stomatal response to light. A dual-leaf model, scaling up Gsc from leaf to canopy, was developed in this study. The non-linear stomata-light relationship was incorporated by dividing the canopy into sunlit and shaded fractions and calculating each fraction separately according to absorbed irradiances. The model includes: (1) the absorbed irradiance, determined by separately integrating the sunlit and shaded leaves with consideration of both beam and diffuse radiation; (2) leaf area for the sunlit and shaded fractions; and (3) a leaf conductance model that accounts for the response of stomata to PAR, vapor pressure deficit and available soil water. In contrast to the significant errors of Gsc in the big-leaf model, the predicted Gsc using the dual-leaf model had a high degree of data-model agreement; the slope of the linear regression between daytime predictions and measurements was 1.01 (R2 = 0.98), with RMSE of 0.6120 mm s−1 for four clear-sky days in different growth stages. The estimates of half-hourly λET using the dual-source dual-leaf model (DSDL) agreed well with measurements and the error was within 5% during two growing seasons of maize with differing hydrometeorological and management strategies. Moreover, the estimates of soil evaporation using the DSDL model closely matched actual measurements. Our results indicate that the DSDL model can produce more accurate estimation of Gsc and λET, compared to the big-leaf model, and thus is an effective alternative approach for estimating and

  17. CO2 enrichment modulates ammonium nutrition in tomato adjusting carbon and nitrogen metabolism to stomatal conductance.

    PubMed

    Vega-Mas, Izargi; Marino, Daniel; Sánchez-Zabala, Joseba; González-Murua, Carmen; Estavillo, Jose María; González-Moro, María Begoña

    2015-12-01

    Ammonium (NH4(+)) toxicity typically occurs in plants exposed to high environmental NH4(+) concentration. NH4(+) assimilating capacity may act as a biochemical mechanism avoiding its toxic accumulation but requires a fine tuning between nitrogen assimilating enzymes and carbon anaplerotic routes. In this work, we hypothesized that extra C supply, exposing tomato plants cv. Agora Hybrid F1 to elevated atmospheric CO2, could improve photosynthetic process and thus ameliorate NH4(+) assimilation and tolerance. Plants were grown under nitrate (NO3(-)) or NH4(+) as N source (5-15mM), under two atmospheric CO2 levels, 400 and 800ppm. Growth and gas exchange parameters, (15)N isotopic signature, C and N metabolites and enzymatic activities were determined. Plants under 7.5mM N equally grew independently of the N source, while higher ammonium supply resulted toxic for growth. However, specific stomatal closure occurred in 7.5mM NH4(+)-fed plants under elevated CO2 improving water use efficiency (WUE) but compromising plant N status. Elevated CO2 annulled the induction of TCA anaplerotic enzymes observed at non-toxic NH4(+) nutrition under ambient CO2. Finally, CO2 enrichment benefited tomato growth under both nutritions, and although it did not alleviate tomato NH4(+) tolerance it did differentially regulate plant metabolism in N-source and -dose dependent manner. PMID:26706056

  18. CO2 enrichment modulates ammonium nutrition in tomato adjusting carbon and nitrogen metabolism to stomatal conductance.

    PubMed

    Vega-Mas, Izargi; Marino, Daniel; Sánchez-Zabala, Joseba; González-Murua, Carmen; Estavillo, Jose María; González-Moro, María Begoña

    2015-12-01

    Ammonium (NH4(+)) toxicity typically occurs in plants exposed to high environmental NH4(+) concentration. NH4(+) assimilating capacity may act as a biochemical mechanism avoiding its toxic accumulation but requires a fine tuning between nitrogen assimilating enzymes and carbon anaplerotic routes. In this work, we hypothesized that extra C supply, exposing tomato plants cv. Agora Hybrid F1 to elevated atmospheric CO2, could improve photosynthetic process and thus ameliorate NH4(+) assimilation and tolerance. Plants were grown under nitrate (NO3(-)) or NH4(+) as N source (5-15mM), under two atmospheric CO2 levels, 400 and 800ppm. Growth and gas exchange parameters, (15)N isotopic signature, C and N metabolites and enzymatic activities were determined. Plants under 7.5mM N equally grew independently of the N source, while higher ammonium supply resulted toxic for growth. However, specific stomatal closure occurred in 7.5mM NH4(+)-fed plants under elevated CO2 improving water use efficiency (WUE) but compromising plant N status. Elevated CO2 annulled the induction of TCA anaplerotic enzymes observed at non-toxic NH4(+) nutrition under ambient CO2. Finally, CO2 enrichment benefited tomato growth under both nutritions, and although it did not alleviate tomato NH4(+) tolerance it did differentially regulate plant metabolism in N-source and -dose dependent manner.

  19. Stomatal and mesophyll conductances to CO2 are the main limitations to photosynthesis in sugar beet (Beta vulgaris) plants grown with excess zinc.

    PubMed

    Sagardoy, R; Vázquez, S; Florez-Sarasa, I D; Albacete, A; Ribas-Carbó, M; Flexas, J; Abadía, J; Morales, F

    2010-07-01

    *The effects of zinc (Zn) toxicity on photosynthesis and respiration were investigated in sugar beet (Beta vulgaris) plants grown hydroponically with 1.2, 100 and 300 microM Zn. *A photosynthesis limitation analysis was used to assess the stomatal, mesophyll, photochemical and biochemical contributions to the reduced photosynthesis observed under Zn toxicity. *The main limitation to photosynthesis was attributable to stomata, with stomatal conductances decreasing by 76% under Zn excess and stomata being unable to respond to physiological and chemical stimuli. The effects of excess Zn on photochemistry were minor. Scanning electron microscopy showed morphological changes in stomata and mesophyll tissue. Stomatal size and density were smaller, and stomatal slits were sealed in plants grown under high Zn. Moreover, the mesophyll conductance to CO(2) decreased by 48% under Zn excess, despite a marked increase in carbonic anhydrase activity. Respiration, including that through both cytochrome and alternative pathways, was doubled by high Zn. *It can be concluded that, in sugar beet plants grown in the presence of excess Zn, photosynthesis is impaired due to a depletion of CO(2) at the Rubisco carboxylation site, as a consequence of major decreases in stomatal and mesophyll conductances to CO(2).

  20. Contribution of PsbS Function and Stomatal Conductance to Foliar Temperature in Higher Plants

    PubMed Central

    Kulasek, Milena; Bernacki, Maciej Jerzy; Ciszak, Kamil; Witoń, Damian; Karpiński, Stanisław

    2016-01-01

    Natural capacity has evolved in higher plants to absorb and harness excessive light energy. In basic models, the majority of absorbed photon energy is radiated back as fluorescence and heat. For years the proton sensor protein PsbS was considered to play a critical role in non-photochemical quenching (NPQ) of light absorbed by PSII antennae and in its dissipation as heat. However, the significance of PsbS in regulating heat emission from a whole leaf has never been verified before by direct measurement of foliar temperature under changing light intensity. To test its validity, we here investigated the foliar temperature changes on increasing and decreasing light intensity conditions (foliar temperature dynamics) using a high resolution thermal camera and a powerful adjustable light-emitting diode (LED) light source. First, we showed that light-dependent foliar temperature dynamics is correlated with Chl content in leaves of various plant species. Secondly, we compared the foliar temperature dynamics in Arabidopsis thaliana wild type, the PsbS null mutant npq4-1 and a PsbS-overexpressing transgenic line under different transpiration conditions with or without a photosynthesis inhibitor. We found no direct correlations between the NPQ level and the foliar temperature dynamics. Rather, differences in foliar temperature dynamics are primarily affected by stomatal aperture, and rapid foliar temperature increase during irradiation depends on the water status of the leaf. We conclude that PsbS is not directly involved in regulation of foliar temperature dynamics during excessive light energy episodes. PMID:27273581

  1. Anisohydric but isohydrodynamic: seasonally constant plant water potential gradient explained by a stomatal control mechanism incorporating variable plant hydraulic conductance.

    PubMed

    Franks, Peter J; Drake, Paul L; Froend, Ray H

    2007-01-01

    Isohydric and anisohydric regulations of plant water status have been observed over several decades of field, glasshouse and laboratory studies, yet the functional significance and mechanism of both remain obscure. We studied the seasonal trends in plant water status and hydraulic properties in a natural stand of Eucalyptus gomphocephala through cycles of varying environmental moisture (rainfall, groundwater depth, evaporative demand) in order to test for isohydry and to provide physiological information for the mechanistic interpretation of seasonal trends in plant water status. Over a 16 month period of monitoring, spanning two summers, midday leaf water potential (psi(leaf)) correlated with predawn psi(leaf), which was correlated with water table depth below ground level, which in turn was correlated with total monthly rainfall. Eucalyptus gomphocephala was therefore not seasonally isohydric. Despite strong stomatal down-regulation of transpiration rate in response to increasing evaporative demand, this was insufficient to prevent midday psi(leaf) from falling to levels below -2 MPa in the driest month, well into the region likely to induce xylem air embolisms, based on xylem vulnerability curves obtained in the study. However, even though midday psi(leaf) varied by over 1.2 MPa across seasons, the hydrodynamic (transpiration-induced) water potential gradient from roots to shoots (delta psi(plant)), measured as the difference between predawn and midday psi(leaf), was relatively constant across seasons, averaging 0.67 MPa. This unusual pattern of hydraulic regulation, referred to here as isohydrodynamic, is explained by a hydromechanical stomatal control model where plant hydraulic conductance is dependent on transpiration rate.

  2. Optimizing stomatal conductance for maximum carbon gain under water stress: A meta-analysis across plant functional types and climates

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Stomatal responses to environmental variables, in particular atmospheric CO2 concentration and soil water status, are needed for quantifying the controls on carbon and water exchanges between plants and the atmosphere. Building on previous leaf-scale gas exchange models and stomatal optimality theor...

  3. Daytime and nighttime wind differentially affects hydraulic properties and thigmomorphogenic response of poplar saplings.

    PubMed

    Huang, Ping; Wan, Xianchong; Lieffers, Victor J

    2016-05-01

    This study tested how wind in daytime and nighttime affects hydraulic properties and thigmomorphogenic response of poplar saplings. It shows that wind in daytime interrupted water balance of poplar plants by aggravating cavitation in the stem xylem under high xylem tension in the daytime, reducing water potential in midday and hence reducing gas exchange, including stomatal conductance and CO2 assimilation. The wind blowing in daytime significantly reduced plant growth, including height, diameter, leaf size, leaf area, root and whole biomass, whereas wind blowing in nighttime only caused a reduction in radial and height growth at the early stage compared with the control but decreased height:diameter ratios. In summary, the interaction between wind loading and xylem tension exerted a negative impact on water balance, gas exchanges and growth of poplar plants, and wind in nighttime caused only a small thigmomorphogenic response. PMID:26541407

  4. Drought tolerance, xylem sap abscisic acid and stomatal conductance during soil drying: a comparison of canopy trees of three temperate deciduous angiosperms.

    PubMed

    Loewenstein, Nancy J.; Pallardy, Stephen G.

    1998-07-01

    Patterns of water relations, xylem sap abscisic acid concentration ([ABA]) and stomatal aperture were characterized and compared in drought-sensitive black walnut (Juglans nigra L.), less drought-sensitive sugar maple (Acer saccharum Marsh.) and drought-tolerant white oak (Quercus alba L.) trees co-occurring in a second-growth forest in Missouri, USA. There were strong correlations among reduction in predawn leaf water potential, increased xylem sap [ABA] and stomatal closure in all species. Stomatal conductance was more closely correlated with xylem sap ABA concentration than with ABA flux or xylem sap pH and cation concentrations. In isohydric black walnut, increased concentrations of ABA in the xylem sap appeared to be primarily of root origin, causing stomatal closure in response to soil drying. In anisohydric sugar maple and white oak, however, there were reductions in midday leaf water potential associated with stomatal closure, making it uncertain whether drought-induced xylem sap ABA was of leaf or root origin. The role of root-originated xylem sap ABA in these species as a signal to the shoot of the water status of the roots is, therefore, less certain.

  5. Photosynthetic Induction State of Leaves in a Soybean Canopy in Relation to Light Regulation of Ribulose-1-5-Bisphosphate Carboxylase and Stomatal Conductance 1

    PubMed Central

    Pearcy, Robert W.; Seemann, Jeffrey R.

    1990-01-01

    Photosynthetic induction state, stomatal conductance and light regulation of ribulose-1,5-bisphosphate carboxylase (rubisco) were examined for leaves in a mature, closed soybean (Glycine max) canopy (leaf area index approximately 5) with the objective to determine the extent to which these factors may be limiting the capacity to respond to light transients during sunflecks. When sampled along a vertical gradient, leaves near the bottom of the canopy had lower rubisco contents and chlorophyll a/b ratios as compared with upper leaves. Leaves sampled at midcanopy showed a wide variation in photosynthetic induction state (ratio of the photosynthetic rate achieved after 1 minute exposure to high light to the steady-state assimilation rate achieved after 20 minutes exposure). Both photosynthetic induction state and the initial rubisco activity varied in parallel with stomatal conductance. By contrast there was no correlation between total rubisco activity and stomatal conductance. The results indicate that induction state, as determined by the light regulation of both rubisco activity and stomatal conductance, is an important limitation to the ability of leaves in a soybean canopy to respond to light transients that occur during sunflecks. PMID:16667758

  6. Decoupling the Influence of Leaf and Root Hydraulic Conductances on Stomatal Conductance and its Sensitivity to Vapor Pressure Deficit as Soil Dries in a Drained Loblolly Pine Plantation

    NASA Astrophysics Data System (ADS)

    Domec, J.; Noormets, A.; King, J. S.; McNulty, S. G.; Sun, G.; Gavazzi, M. J.; Boggs, J. L.

    2008-12-01

    The conversion of wetlands to intensively managed forest lands in eastern North Carolina is widespread and the consequences on plant hydraulic properties and water balances are not well studied. Precipitation and soil moisture in North America will be modified in the future and forest trees in the US will be challenged by warmer temperature, higher leaf-to-air water vapor pressure deficit (D), and more frequent summer droughts. Many studies have examined the relationships between whole tree hydraulic conductance (Ktree) and stomatal conductance (gs), but Ktree remains an ill-defined quantity because it depends on a series of resistances, mainly controlled by the conductance in roots (Kroot) and leaves (Kleaf). To explain the variation in Ktree, we characterized Kroot and Kleaf and how they responded to environmental drivers such as soil moisture availability and D. In addition, the role of dynamic variations in Kroot and Kleaf in mediating stomatal control of transpiration and its response to D was studied. The 2007 summer drought was used as a means to challenge the hydraulic system, allowing testing how broadly predictions about its behaviour hold outside the range of typical conditions. Roots and leaves were the weakest points in the whole tree hydraulic system, and contributed for more than 75% of the total tree hydraulic resistance. Effects of drought on Ktree altered the partitioning of the resistance between roots and leaves and as soil moisture declined below 50% relative extractable water (REW), Kroot declined faster than Kleaf and became the dominant hydraulic fuse regulating Ktree. Although Ktree depended on soil moisture, its dynamics was tempered by current-year needle elongation that increased significantly Kleaf during the dry months when REW was below 50%. To maintain the integrity of the xylem hydraulic continuum from roots to leaves, stomata were highly responsive in coordinating transpiration with dynamic variation in Ktree. Daily maximum gs and

  7. Control of Photosynthesis and Stomatal Conductance in Ricinus communis L. (Castor Bean) by Leaf to Air Vapor Pressure Deficit.

    PubMed

    Dai, Z; Edwards, G E; Ku, M S

    1992-08-01

    Castor bean (Ricinus communis L.) has a high photosynthetic capacity under high humidity and a pronounced sensitivity of photosynthesis to high water vapor pressure deficit (VPD). The sensitivity of photosynthesis to varying VPD was analyzed by measuring CO(2) assimilation, stomatal conductance (g(s)), quantum yield of photosystem II (phi(II)), and nonphotochemical quenching of chlorophyll fluorescence (q(N)) under different VPD. Under both medium (1000) and high (1800 micromoles quanta per square meter per second) light intensities, CO(2) assimilation decreased as the VPD between the leaf and the air around the leaf increased. The g(s) initially dropped rapidly with increasing VPD and then showed a slower decrease above a VPD of 10 to 20 millibars. Over a temperature range from 20 to 40 degrees C, CO(2) assimilation and g(s) were inhibited by high VPD (20 millibars). However, the rate of transpiration increased with increasing temperature at either low or high VPD due to an increase in g(s). The relative inhibition of photosynthesis under photorespiring (atmospheric levels of CO(2) and O(2)) versus nonphotorespiring (700 microbars CO(2) and 2% O(2)) conditions was greater under high VPD (30 millibars) than under low VPD (3 millibars). Also, with increasing light intensity the relative inhibition of photosynthesis by O(2) increased under high VPD, but decreased under low VPD. The effect of high VPD on photosynthesis under various conditions could not be totally accounted for by the decrease in the intercellular CO(2) in the leaf (C(i)) where C(i) was estimated from gas exchange measurements. However, estimates of C(i) from measurements of phi(II) and q(N) suggest that the decrease in photosynthesis and increase in photorespiration under high VPD can be totally accounted for by stomatal closure and a decrease in C(i). The results also suggest that nonuniform closure of stomata may occur in well-watered plants under high VPD, causing overestimates in the calculation

  8. Stomatal and mesophyll conductances to CO₂ in different plant groups: underrated factors for predicting leaf photosynthesis responses to climate change?

    PubMed

    Flexas, Jaume; Carriquí, Marc; Coopman, Rafael E; Gago, Jorge; Galmés, Jeroni; Martorell, Sebastià; Morales, Fermín; Diaz-Espejo, Antonio

    2014-09-01

    The climate change conditions predicted for the end of the current century are expected to have an impact on the performance of plants under natural conditions. The variables which are foreseen to have a larger effect are increased CO2 concentration and temperature. Although it is generally considered CO2 assimilation rate could be increased by the increasing levels of CO2, it has been reported in previous studies that acclimation to high CO2 results in reductions of physiological parameters involved in photosynthesis, like the maximum carboxylation rate (Vc,max), stomatal conductance (gs) and mesophyll conductance to CO2 (gm). On the one hand, most of the previous modeling efforts have neglected the potential role played by the acclimation of gm to high CO2 and temperature. On the other hand, the effect of climate change on plant clades other than angiosperms, like ferns, has received little attention, and there are no studies evaluating the potential impact of increasing CO2 and temperature on these species. In this study we predicted responses of several representative species among angiosperms, gymnosperms and ferns to increasing CO2 and temperature. Our results show that species with lower photosynthetic capacity - such as some ferns and gymnosperms - would be proportionally more favored under these foreseen environmental conditions. The main reason for this difference is the lower diffusion limitation imposed by gs and gm in plants having high capacity for photosynthesis among the angiosperms, which reduces the positive effect of increasing CO2. However, this apparent advantage of low-diffusion species would be canceled if the two conductances - gs and gm - acclimate and are down regulated to high CO2, which is basically unknown, especially for gymnosperms and ferns. Hence, for a better understanding of different plant responses to future climate, studies are urged in which the actual photosynthetic response/acclimation to increased CO2 and temperature of

  9. Sugarcane for water-limited environments. Variation in stomatal conductance and its genetic correlation with crop productivity.

    PubMed

    Basnayake, J; Jackson, P A; Inman-Bamber, N G; Lakshmanan, P

    2015-07-01

    Stomatal conductance (g(s)) and canopy temperature have been used to estimate plant water status in many crops. The behaviour of g(s) in sugarcane indicates that the internal leaf water status is controlled by regular opening and closing of stomata. A large number of g(s) measurements obtained across varying moisture regimes, locations, and crop cycles with a diverse sugarcane germplasm composed of introgression, and commercial clones indicated that there is a high genetic variation for g(s) that can be exploited in a breeding programme. Regardless of the environmental influences on the expression of this trait, moderate heritability was observed across 51 sets of individual measurements made on replicated trials over 3 years. The clone×water status interaction (G×E) variation was smaller than the clone (G) variation on many occasions. A wide range of genetic correlations (r(g)= -0.29 to 0.94) between g(s) and yield were observed across test environments in all three different production regions used. Canopy conductance (g(c)) based on g(s) and leaf area index (LAI) showed a stronger genetic correlation than the g(s) with cane yield (tonnes of cane per hectare; TCH) at 12 months (mature crop). The regression analysis of input weather data for the duration of measurements showed that the predicted values of r(g) correlated with the maximum temperature (r=0.47) during the measurements and less with other environmental variables. These results confirm that the g(c) could have potential as a criterion for early-stage selection of clones in sugarcane breeding programmes.

  10. Sugarcane for water-limited environments. Variation in stomatal conductance and its genetic correlation with crop productivity.

    PubMed

    Basnayake, J; Jackson, P A; Inman-Bamber, N G; Lakshmanan, P

    2015-07-01

    Stomatal conductance (g(s)) and canopy temperature have been used to estimate plant water status in many crops. The behaviour of g(s) in sugarcane indicates that the internal leaf water status is controlled by regular opening and closing of stomata. A large number of g(s) measurements obtained across varying moisture regimes, locations, and crop cycles with a diverse sugarcane germplasm composed of introgression, and commercial clones indicated that there is a high genetic variation for g(s) that can be exploited in a breeding programme. Regardless of the environmental influences on the expression of this trait, moderate heritability was observed across 51 sets of individual measurements made on replicated trials over 3 years. The clone×water status interaction (G×E) variation was smaller than the clone (G) variation on many occasions. A wide range of genetic correlations (r(g)= -0.29 to 0.94) between g(s) and yield were observed across test environments in all three different production regions used. Canopy conductance (g(c)) based on g(s) and leaf area index (LAI) showed a stronger genetic correlation than the g(s) with cane yield (tonnes of cane per hectare; TCH) at 12 months (mature crop). The regression analysis of input weather data for the duration of measurements showed that the predicted values of r(g) correlated with the maximum temperature (r=0.47) during the measurements and less with other environmental variables. These results confirm that the g(c) could have potential as a criterion for early-stage selection of clones in sugarcane breeding programmes. PMID:25948709

  11. [Water recharge through nighttime stem sap flow of Schima superba in Guangzhou region of Guangdong Province, South China: affecting factors and contribution to transpiration].

    PubMed

    Zhou, Cui-Ming; Zhao, Ping; Ni, Guang-Yan; Wang, Quan; Zeng, Xiao-Ping; Zhu, Li-Wei; Cai, Xi-An

    2012-07-01

    To understand the nighttime water recharge of tree through its sap flow is beneficial to the precise estimation of total transpiration and canopy stomatal conductance, and to the further understanding of the time lag between canopy transpiration and stem sap flow. By using Granier's thermal dissipation probe, this paper measured the stem sap flow of Schima superba, and synchronously measured the main environmental factors including air temperature, relative humidity, photosynthetically active radiation, and soil moisture content, and also analyzed the water recharge through nighttime stem flow of S. superba at daily and seasonal scales. The sap flow density of S. superba was lower at night than at daytime, and the nighttime sap flow density had a larger variation in dry season than in wet season. The water recharge at night generally started from sunset when radiation was approaching zero, and lasted up to midnight (18:00-22:00). No significant difference was observed in the nighttime water recharge among seasons, and no significant correlations were found between the nighttime water recharge and environmental factors, but the nighttime water recharge was well regressed with the diameter at breast height, tree height, tree canopy size, stem biomass, and canopy biomass, suggesting that tree form features and biomass could better explain the nighttime water recharge. The contribution of nighttime water recharge to the total transpiration varied significantly with seasons, and was obviously higher in dry season than in wet season. PMID:23173445

  12. [Water recharge through nighttime stem sap flow of Schima superba in Guangzhou region of Guangdong Province, South China: affecting factors and contribution to transpiration].

    PubMed

    Zhou, Cui-Ming; Zhao, Ping; Ni, Guang-Yan; Wang, Quan; Zeng, Xiao-Ping; Zhu, Li-Wei; Cai, Xi-An

    2012-07-01

    To understand the nighttime water recharge of tree through its sap flow is beneficial to the precise estimation of total transpiration and canopy stomatal conductance, and to the further understanding of the time lag between canopy transpiration and stem sap flow. By using Granier's thermal dissipation probe, this paper measured the stem sap flow of Schima superba, and synchronously measured the main environmental factors including air temperature, relative humidity, photosynthetically active radiation, and soil moisture content, and also analyzed the water recharge through nighttime stem flow of S. superba at daily and seasonal scales. The sap flow density of S. superba was lower at night than at daytime, and the nighttime sap flow density had a larger variation in dry season than in wet season. The water recharge at night generally started from sunset when radiation was approaching zero, and lasted up to midnight (18:00-22:00). No significant difference was observed in the nighttime water recharge among seasons, and no significant correlations were found between the nighttime water recharge and environmental factors, but the nighttime water recharge was well regressed with the diameter at breast height, tree height, tree canopy size, stem biomass, and canopy biomass, suggesting that tree form features and biomass could better explain the nighttime water recharge. The contribution of nighttime water recharge to the total transpiration varied significantly with seasons, and was obviously higher in dry season than in wet season.

  13. Evaluating stomatal ozone fluxes in WRF-Chem: Comparing ozone uptake in Mediterranean ecosystems

    NASA Astrophysics Data System (ADS)

    Rydsaa, J. H.; Stordal, F.; Gerosa, G.; Finco, A.; Hodnebrog, Ø.

    2016-10-01

    The development of modelling tools for estimating stomatal uptake of surface ozone in vegetation is important for the assessment of potential damage induced due to both current and future near surface ozone concentrations. In this study, we investigate the skill in estimating ozone uptake in plants by the Weather Research and Forecasting model coupled with chemistry (WRF-Chem) V3.6.1, with the Wesely dry deposition scheme. To validate the stomatal uptake of ozone, the model simulations were compared with field measurements of three types of Mediterranean vegetation, over seven different periods representing various meteorological conditions. Some systematic biases in modelled ozone fluxes are revealed; the lack of an explicit and time varying dependency on plants' water availability results in overestimated daytime ozone stomatal fluxes particularly in dry periods. The optimal temperature in the temperature response function is likely too low for the woody species tested here. Also, too low nighttime stomatal conductance leads to underestimation of ozone uptake during night. We demonstrate that modelled stomatal ozone flux is improved by accounting for vapor pressure deficit in the ambient air. Based on the results of the overall comparison to measured fluxes, we propose that additional improvements to the stomatal conductance parameterization should be implemented before applying the modelling system for estimating ozone doses and potential damage to vegetation.

  14. Seasonal trend of photosynthetic parameters and stomatal conductance of blue oak (Quercus douglasii) under prolonged summer drought and high temperature

    SciTech Connect

    Xu, L; Baldocchi, DD

    2003-09-01

    OAK-B135 Understanding seasonal changes in photosynthetic parameters and stomatal conductance is crucial for modeling long-term carbon uptake and energy fluxes of ecosystems. Gas exchange measurements of CO{sub 2} and light response curves on blue oak leaves (Quercus douglasii H. & A.) were conducted weekly throughout the growing season to study the seasonality of photosynthetic capacity (V{sub cmax}) and Ball-Berry slope (m) under prolonged summer drought and high temperature. A leaf photosynthetic model was used to determine V{sub cmax}. There was a pronounced seasonal pattern in V{sub cmax}. The maximum value of V{sub cmax}, 127 {micro}molm{sup -2} s{sup -1},was reached shortly after leaf expansion in early summer, when air temperature was moderate and soil water availability was high. Thereafter, V{sub cmax} declined as the soil water profile became depleted and the trees experienced extreme air temperatures, exceeding 40 C. The decline in V{sub cmax} was gradual in midsummer, however, despite extremely low predawn leaf water potentials ({Psi}{sub pd}, {approx} -4.0 MPa). Overall, temporal changes in V{sub cmax} were well correlated with changes in leaf nitrogen content. During spring leaf development, high rates of leaf dark respiration (R{sub d}, 5-6 {micro}mol m{sup -2} s{sup -1}) were observed. Once a leaf reached maturity, R{sub d} remained low, around 0.5 {micro}mol m{sup -2} s{sup -1}. In contrast to the strong seasonality of V{sub cmax}, m and marginal water cost per unit carbon gain ({partial_derivative}E/{partial_derivative}A) were relatively constant over the season, even when leaf {Psi}{sub pd} dropped to -6.8 MPa. The constancy of {partial_derivative}E/{partial_derivative}A suggests that stomata behaved optimally under severe water-stress conditions. We discuss the implications of our findings in the context of modeling carbon and water vapor exchange between ecosystems and the atmosphere.

  15. Expression of ABA synthesis and metabolism genes under different irrigation strategies and atmospheric VPDs is associated with stomatal conductance in grapevine (Vitis vinifera L. cv Cabernet Sauvignon).

    PubMed

    Speirs, Jim; Binney, Allan; Collins, Marisa; Edwards, Everard; Loveys, Brian

    2013-04-01

    The influence of different levels of irrigation and of variation in atmospheric vapour pressure deficit (VPD) on the synthesis, metabolism, and transport of abscisic acid (ABA) and the effects on stomatal conductance were examined in field-grown Cabernet Sauvignon grapevines. Xylem sap, leaf tissue, and root tissue were collected at regular intervals during two seasons in conjunction with measurements of leaf water potential (Ψleaf) and stomatal conductance (gs). The different irrigation levels significantly altered the Ψleaf and gs of the vines across both seasons. ABA abundance in the xylem sap was correlated with gs. The expression of genes associated with ABA synthesis, NCED1 and NCED2, was higher in the roots than in the leaves throughout and highest in the roots in mid January, a time when soil moisture declined and VPD was at its highest. Their expression in roots was also inversely related to the levels of irrigation and correlated with ABA abundance in the roots, xylem sap, and leaves. Three genes encoding ABA 8'-hydroxylases were isolated and their identities confirmed by expression in yeast cells. The expression of one of these, Hyd1, was elevated in leaves when VPD was below 2.0-2.5 kPa and minimal at higher VPD levels. The results provide evidence that ABA plays an important role in linking stomatal response to soil moisture status and that changes in ABA catabolism at or near its site of action allows optimization of gas exchange to current environmental conditions. PMID:23630325

  16. A Negative Hydraulic Message from Oxygen-Deficient Roots of Tomato Plants? (Influence of Soil Flooding on Leaf Water Potential, Leaf Expansion, and Synchrony between Stomatal Conductance and Root Hydraulic Conductivity).

    PubMed

    Else, M. A.; Davies, W. J.; Malone, M.; Jackson, M. B.

    1995-11-01

    Four to 10 h of soil flooding delayed and suppressed the normal daily increase in root hydraulic conductance (Lp) in tomato (Lycopersicon esculentum Mill. cv Ailsa Craig) plants. The resulting short-term loss of synchrony between Lp and stomatal conductance decreased leaf water potential ([psi]L) relative to well-drained plants within 2 h. A decrease in [psi]L persisted for 8 h and was mirrored by decreased leaf thickness measured using linear displacement transducers. After 10 h of flooding, further closing of stomata and re-convergence of Lp in flooded and well-drained roots returned [psi]L to control values. In the second photoperiod, Lp in flooded plants exceeded that in well-drained plants in association with much increased Lp and decreased stomatal conductance. Pneumatic balancing pressure applied to roots of intact flooded plants to prevent temporary loss of [psi]L in the 1st d did not modify the patterns of stomatal closure or leaf expansion. Thus, the magnitude of the early negative hydraulic message was neither sufficient nor necessary to promote stomatal closure and inhibit leaf growth in flooded tomato plants. Chemical messages are presumed to be responsible for these early responses to soil flooding.

  17. Enhanced Photosynthesis and Growth in atquac1 Knockout Mutants Are Due to Altered Organic Acid Accumulation and an Increase in Both Stomatal and Mesophyll Conductance.

    PubMed

    Medeiros, David B; Martins, Samuel C V; Cavalcanti, João Henrique F; Daloso, Danilo M; Martinoia, Enrico; Nunes-Nesi, Adriano; DaMatta, Fábio M; Fernie, Alisdair R; Araújo, Wagner L

    2016-01-01

    Stomata control the exchange of CO2 and water vapor in land plants. Thus, whereas a constant supply of CO2 is required to maintain adequate rates of photosynthesis, the accompanying water losses must be tightly regulated to prevent dehydration and undesired metabolic changes. Accordingly, the uptake or release of ions and metabolites from guard cells is necessary to achieve normal stomatal function. The AtQUAC1, an R-type anion channel responsible for the release of malate from guard cells, is essential for efficient stomatal closure. Here, we demonstrate that mutant plants lacking AtQUAC1 accumulated higher levels of malate and fumarate. These mutant plants not only display slower stomatal closure in response to increased CO2 concentration and dark but are also characterized by improved mesophyll conductance. These responses were accompanied by increases in both photosynthesis and respiration rates, without affecting the activity of photosynthetic and respiratory enzymes and the expression of other transporter genes in guard cells, which ultimately led to improved growth. Collectively, our results highlight that the transport of organic acids plays a key role in plant cell metabolism and demonstrate that AtQUAC1 reduce diffusive limitations to photosynthesis, which, at least partially, explain the observed increments in growth under well-watered conditions.

  18. Enhanced Photosynthesis and Growth in atquac1 Knockout Mutants Are Due to Altered Organic Acid Accumulation and an Increase in Both Stomatal and Mesophyll Conductance.

    PubMed

    Medeiros, David B; Martins, Samuel C V; Cavalcanti, João Henrique F; Daloso, Danilo M; Martinoia, Enrico; Nunes-Nesi, Adriano; DaMatta, Fábio M; Fernie, Alisdair R; Araújo, Wagner L

    2016-01-01

    Stomata control the exchange of CO2 and water vapor in land plants. Thus, whereas a constant supply of CO2 is required to maintain adequate rates of photosynthesis, the accompanying water losses must be tightly regulated to prevent dehydration and undesired metabolic changes. Accordingly, the uptake or release of ions and metabolites from guard cells is necessary to achieve normal stomatal function. The AtQUAC1, an R-type anion channel responsible for the release of malate from guard cells, is essential for efficient stomatal closure. Here, we demonstrate that mutant plants lacking AtQUAC1 accumulated higher levels of malate and fumarate. These mutant plants not only display slower stomatal closure in response to increased CO2 concentration and dark but are also characterized by improved mesophyll conductance. These responses were accompanied by increases in both photosynthesis and respiration rates, without affecting the activity of photosynthetic and respiratory enzymes and the expression of other transporter genes in guard cells, which ultimately led to improved growth. Collectively, our results highlight that the transport of organic acids plays a key role in plant cell metabolism and demonstrate that AtQUAC1 reduce diffusive limitations to photosynthesis, which, at least partially, explain the observed increments in growth under well-watered conditions. PMID:26542441

  19. Decreased photosynthesis in the erect panicle 3 (ep3) mutant of rice is associated with reduced stomatal conductance and attenuated guard cell development

    PubMed Central

    Yu, Hongyang; Murchie, Erik H.; González-Carranza, Zinnia H.; Pyke, Kevin A.; Roberts, Jeremy A.

    2015-01-01

    The ERECT PANICLE 3 gene of rice encodes a peptide that exhibits more than 50% sequence identity with the Arabidopsis F-box protein HAWAIIAN SKIRT (HWS). Ectopic expression of the Os02g15950 coding sequence, driven by the HWS (At3g61950) promoter, rescued the hws-1 flower phenotype in Arabidopsis confirming that EP3 is a functional orthologue of HWS. In addition to displaying an erect inflorescence phenotype, loss-of-function mutants of Os02g15950 exhibited a decrease in leaf photosynthetic capacity and stomatal conductance. Analysis of a range of physiological and anatomical features related to leaf photosynthesis revealed no alteration in Rubisco content and no notable changes in mesophyll size or arrangement. However, both ep3 mutant plants and transgenic lines that have a T-DNA insertion within the Os02g15950 (EP3) gene exhibit smaller stomatal guard cells compared with their wild-type controls. This anatomical characteristic may account for the observed decrease in leaf photosynthesis and provides evidence that EP3 plays a role in regulating stomatal guard cell development. PMID:25582452

  20. Decreased photosynthesis in the erect panicle 3 (ep3) mutant of rice is associated with reduced stomatal conductance and attenuated guard cell development.

    PubMed

    Yu, Hongyang; Murchie, Erik H; González-Carranza, Zinnia H; Pyke, Kevin A; Roberts, Jeremy A

    2015-03-01

    The ERECT PANICLE 3 gene of rice encodes a peptide that exhibits more than 50% sequence identity with the Arabidopsis F-box protein HAWAIIAN SKIRT (HWS). Ectopic expression of the Os02g15950 coding sequence, driven by the HWS (At3g61950) promoter, rescued the hws-1 flower phenotype in Arabidopsis confirming that EP3 is a functional orthologue of HWS. In addition to displaying an erect inflorescence phenotype, loss-of-function mutants of Os02g15950 exhibited a decrease in leaf photosynthetic capacity and stomatal conductance. Analysis of a range of physiological and anatomical features related to leaf photosynthesis revealed no alteration in Rubisco content and no notable changes in mesophyll size or arrangement. However, both ep3 mutant plants and transgenic lines that have a T-DNA insertion within the Os02g15950 (EP3) gene exhibit smaller stomatal guard cells compared with their wild-type controls. This anatomical characteristic may account for the observed decrease in leaf photosynthesis and provides evidence that EP3 plays a role in regulating stomatal guard cell development.

  1. Responses of foliar photosynthetic electron transport, pigment stoichiometry, and stomatal conductance to interacting environmental factors in a mixed species forest canopy.

    PubMed

    Niinemets; Bilger; Kull; Tenhunen

    1999-11-01

    We studied limitations caused by variations in leaf temperature and soil water availability on photosynthetic electron transport rates calculated from foliar chlorophyll fluorescence analysis (U) in a natural deciduous forest canopy composed of shade-intolerant Populus tremula L. and shade-tolerant Tilia cordata Mill. In both species, there was a positive linear relationship between light-saturated U (Umax) per unit leaf area and mean seasonal integrated daily quantum flux density (Ss, mol per square m per day). Acclimation of leaf dry mass per area and nitrogen per area to growth irradiance largely accounted for this positive scaling. However, the slopes of the Umax versus Ss relationships were greater on days when leaf temperature was high than on days when leaf temperature was low. Overall, Umax varied 2.5-fold across a temperature range of 20-30 degrees C. Maximum stomatal conductance (Gmax) also scaled positively with Ss. Although Gmax observed during daily time courses, and stomatal conductances during Umax measurements declined in response to seasonally decreasing soil water contents, was insensitive to prolonged water stress, and was not strongly correlated with stomatal conductances during its estimation. These results suggest that photorespiration was an important electron sink when intercellular CO2 concentration was low because of closed stomata. Given that xanthophyll cycle pool size (VAZ, sum of violaxanthin, antheraxanthin, and zeaxanthin) may play an important role in dissipation of excess excitation energy, the response of VAZ to fluctuating light and temperature provided another possible explanation for the stable Umax. Xanthophyll cycle carotenoids per total leaf chlorophyll (VAZ/Chl) scaled positively with integrated light and negatively with daily minimum air temperature, whereas the correlation between VAZ/Chl and irradiance was best with integrated light averaged over 3 days preceding foliar sampling. We conclude that the potential capacity

  2. Factors affecting stomatal uptake of ozone by different canopies and a comparison between dose and exposure.

    PubMed

    Zhang, Leiming; Vet, Robert; Brook, Jeffrey R; Legge, Allan H

    2006-10-15

    Measured ozone (O(3)) and carbon dioxide (CO(2)) concentrations and fluxes over five different canopies (mixed coniferous-deciduous forest, deciduous forest, corn, soybean and pasture) in the eastern USA were analyzed to investigate the stomatal uptake of O(3). It was found that the ambient O(3) concentration levels had little effect on stomatal conductance. However, the accumulated stomatal uptake of O(3), upon reaching a threshold value on any given day, appears to reduce the rate of further O(3) uptake substantially. This may explain why the maximum O(3) deposition velocity often appeared in the early morning hours over some forest canopies. Substantially reduced CO(2) fluxes over wet canopies compared to dry canopies suggest that stomata were likely partially or totally blocked by water droplets or films when canopies were wet. By using a big-leaf dry deposition model, measured O(3) fluxes were separated into stomatal and non-stomatal portions. It was estimated that stomatal uptake contributed 55-75% of the total daytime O(3) fluxes and 40-60% of the total daytime plus nighttime fluxes, depending on canopy type. This suggests that about half of the total O(3) flux occurred through the non-stomatal pathway. At three locations (deciduous forest, corn and soybean sites), O(3) concentrations of 30-60 ppb and of 60-85 ppb contributed equally to the accumulated stomatal fluxes, while at the other two locations (mixed coniferous-deciduous forest and pasture sites), concentrations of 30-60 ppb contributed twice as much as those from 60 to 85 ppb.

  3. Observations and models of emissions of volatile terpenoid compounds from needles of ponderosa pine trees growing in situ: control by light, temperature and stomatal conductance

    SciTech Connect

    Harley, Peter; Eller, Allyson; Guenther, Alex; Monson, Russell K.

    2014-07-12

    Terpenoid emissions from ponderosa pine (Pinus ponderosa subsp. scopulorum) were measured in Colorado, USA over two growing seasons to evaluate the role of incident light, needle temperature and stomatal conductance in controlling emissions of 2-methyl-3-buten-2-ol (MBO) and several monoterpenes. MBO was the dominant daylight terpenoid emission, comprising on average 87% of the total flux, and diurnal variations were largely determined by light and temperature. During daytime, oxygenated monoterpenes (especially linalool) comprised up to 75% of the total monoterpenoid flux from needles. A significant fraction of monoterpenoid emissions was light dependent and 13CO2 labeling studies confirmed de novo production. Thus, modeling of monoterpenoid emissions required a hybrid model in which a significant fraction of emissions was dependent on both light and temperature, while the remainder was dependent on temperature alone. Experiments in which stomata were forced to close using abscisic acid demonstrated that MBO and a large fraction of the monoterpene flux, presumably linalool, could be limited at the scale of seconds to minutes by stomatal conductance. Using a previously published model of terpenoid emissions which explicitly accounts for the physico-chemical properties of emitted compounds, we are able to simulate these observed stomatal effects, whether induced through experimentation or arising under naturally fluctuation conditions of temperature and light. This study shows unequivocally that, under naturally occurring field conditions, de novo light dependent monoterpenes can comprise a large fraction of emissions. Differences between the monoterpene composition of ambient air and needle emissions imply a significant non-needle emission source enriched in Δ-3-carene.

  4. Observations and models of emissions of volatile terpenoid compounds from needles of ponderosa pine trees growing in situ: control by light, temperature and stomatal conductance.

    PubMed

    Harley, Peter; Eller, Allyson; Guenther, Alex; Monson, Russell K

    2014-09-01

    Terpenoid emissions from ponderosa pine (Pinus ponderosa subsp. scopulorum) were measured in Colorado, USA over two growing seasons to evaluate the role of incident light, needle temperature, and stomatal conductance in controlling emissions of 2-methyl-3-buten-2-ol (MBO) and several monoterpenes. MBO was the dominant daylight terpenoid emission, comprising on average 87% of the total flux, and diurnal variations were largely determined by light and temperature. During daytime, oxygenated monoterpenes (especially linalool) comprised up to 75% of the total monoterpenoid flux from needles. A significant fraction of monoterpenoid emissions was dependent on light and 13CO2 labeling studies confirmed de novo production. Thus, modeling of monoterpenoid emissions required a hybrid model in which a significant fraction of emissions was dependent on both light and temperature, while the remainder was dependent on temperature alone. Experiments in which stomata were forced to close using abscisic acid demonstrated that MBO and a large fraction of the monoterpene flux, presumably linalool, could be limited at the scale of seconds to minutes by stomatal conductance. Using a previously published model of terpenoid emissions, which explicitly accounts for the physicochemical properties of emitted compounds, we were able to simulate these observed stomatal effects, whether induced experimentally or arising under naturally fluctuation conditions of temperature and light. This study shows unequivocally that, under naturally occurring field conditions, de novo light-dependent monoterpenes comprise a significant fraction of emissions in ponderosa pine. Differences between the monoterpene composition of ambient air and needle emissions imply a significant non-needle emission source enriched in Δ-3-carene.

  5. Canopy stomatal conductance following drought, disturbance, and death in an upland oak/pine forest of the new jersey pine barrens, USA.

    PubMed

    Schäfer, Karina Vera Rosa

    2011-01-01

    Stomatal conductance controls carbon and water fluxes in forest ecosystems. Therefore, its accurate characterization in land-surface flux models is necessary. Sap-flux scaled canopy conductance was used to evaluate the effect of drought, disturbance, and mortality of three oak species (Quercus prinus, Q. velutina, and Q. coccinea) in an upland oak/pine stand in the New Jersey Pine Barrens from 2005 to 2008. Canopy conductance (G(C)) was analyzed by performing boundary line analysis and selecting for the highest value under a given light condition. Regressing G(C) with the driving force vapor pressure deficit (VPD) resulted in reference canopy conductance at 1 kPa VPD (G(Cref)). Predictably, drought in 2006 caused G(Cref) to decline. Q. prinusG(Cref) was least affected, followed by Q. coccinea, with Q. velutina having the highest reductions in G(Cref). A defoliation event in 2007 caused G(Cref) to increase due to reduced leaf area and a possible increase in water availability. In Q. prinus, G(Cref) quadrupled, while doubling in Q. velutina, and increasing by 50% in Q. coccinea. Tree mortality in 2008 led to higher G(Cref) in the remaining Q. prinus but not in Q. velutina or Q. coccinea. Comparing light response curves of canopy conductance (G(Cref)) and stomatal conductance (g(S)) derived from gas-exchange measurements showed marked differences in behavior. Canopy G(Cref) failed to saturate under ambient light conditions whereas leaf-level g(S) saturated at 1,200 μmol m(-2) s(-1). The results presented here emphasize the differential responses of leaf and canopy-level conductance to saturating light conditions and the effects of various disturbances (drought, defoliation, and mortality) on the carbon and water balance of an oak-dominated forest. PMID:22639580

  6. Canopy Stomatal Conductance Following Drought, Disturbance, and Death in an Upland Oak/Pine Forest of the New Jersey Pine Barrens, USA

    PubMed Central

    Schäfer, Karina Vera Rosa

    2011-01-01

    Stomatal conductance controls carbon and water fluxes in forest ecosystems. Therefore, its accurate characterization in land-surface flux models is necessary. Sap-flux scaled canopy conductance was used to evaluate the effect of drought, disturbance, and mortality of three oak species (Quercus prinus, Q. velutina, and Q. coccinea) in an upland oak/pine stand in the New Jersey Pine Barrens from 2005 to 2008. Canopy conductance (GC) was analyzed by performing boundary line analysis and selecting for the highest value under a given light condition. Regressing GC with the driving force vapor pressure deficit (VPD) resulted in reference canopy conductance at 1 kPa VPD (GCref). Predictably, drought in 2006 caused GCref to decline. Q. prinus GCref was least affected, followed by Q. coccinea, with Q. velutina having the highest reductions in GCref. A defoliation event in 2007 caused GCref to increase due to reduced leaf area and a possible increase in water availability. In Q. prinus, GCref quadrupled, while doubling in Q. velutina, and increasing by 50% in Q. coccinea. Tree mortality in 2008 led to higher GCref in the remaining Q. prinus but not in Q. velutina or Q. coccinea. Comparing light response curves of canopy conductance (GCref) and stomatal conductance (gS) derived from gas-exchange measurements showed marked differences in behavior. Canopy GCref failed to saturate under ambient light conditions whereas leaf-level gS saturated at 1,200 μmol m−2 s−1. The results presented here emphasize the differential responses of leaf and canopy-level conductance to saturating light conditions and the effects of various disturbances (drought, defoliation, and mortality) on the carbon and water balance of an oak-dominated forest. PMID:22639580

  7. Canopy stomatal conductance following drought, disturbance, and death in an upland oak/pine forest of the new jersey pine barrens, USA.

    PubMed

    Schäfer, Karina Vera Rosa

    2011-01-01

    Stomatal conductance controls carbon and water fluxes in forest ecosystems. Therefore, its accurate characterization in land-surface flux models is necessary. Sap-flux scaled canopy conductance was used to evaluate the effect of drought, disturbance, and mortality of three oak species (Quercus prinus, Q. velutina, and Q. coccinea) in an upland oak/pine stand in the New Jersey Pine Barrens from 2005 to 2008. Canopy conductance (G(C)) was analyzed by performing boundary line analysis and selecting for the highest value under a given light condition. Regressing G(C) with the driving force vapor pressure deficit (VPD) resulted in reference canopy conductance at 1 kPa VPD (G(Cref)). Predictably, drought in 2006 caused G(Cref) to decline. Q. prinusG(Cref) was least affected, followed by Q. coccinea, with Q. velutina having the highest reductions in G(Cref). A defoliation event in 2007 caused G(Cref) to increase due to reduced leaf area and a possible increase in water availability. In Q. prinus, G(Cref) quadrupled, while doubling in Q. velutina, and increasing by 50% in Q. coccinea. Tree mortality in 2008 led to higher G(Cref) in the remaining Q. prinus but not in Q. velutina or Q. coccinea. Comparing light response curves of canopy conductance (G(Cref)) and stomatal conductance (g(S)) derived from gas-exchange measurements showed marked differences in behavior. Canopy G(Cref) failed to saturate under ambient light conditions whereas leaf-level g(S) saturated at 1,200 μmol m(-2) s(-1). The results presented here emphasize the differential responses of leaf and canopy-level conductance to saturating light conditions and the effects of various disturbances (drought, defoliation, and mortality) on the carbon and water balance of an oak-dominated forest.

  8. Surface vapor conductance derived from the ETRHEQ: Dependence on environmental variables and similarity to Oren's stomatal stress model for vapor pressure deficit

    NASA Astrophysics Data System (ADS)

    Salvucci, G.; Rigden, A. J.

    2015-12-01

    Daily time series of evapotranspiration and surface conductance to water vapor were estimated using the ETRHEQ method (Evapotranspiration from Relative Humidity at Equilibrium). ETRHEQ has been previously compared with ameriflux site-level measurements of ET at daily and seasonal time scales, with watershed water balance estimates, and with various benchmark ET data sets. The ETRHEQ method uses meteorological data collected at common weather stations and estimates the surface conductance by minimizing the vertical variance of the calculated relative humidity profile averaged over the day. The key advantage of the ETRHEQ method is that it does not require knowledge of the surface state (soil moisture, stomatal conductance, leaf are index, etc.) or site-specific calibration. The daily estimates of conductance from 229 weather stations for 53 years were analyzed for dependence on environmental variables known to impact stomatal conductance and soil diffusivity: surface temperature, surface vapor pressure deficit, solar radiation, antecedent precipitation (as a surrogate for soil moisture), and a seasonal vegetation greenness index. At each site the summertime (JJAS) conductance values estimated from ETRHEQ were fitted to a multiplicate Jarvis-type stress model. Functional dependence was not proscribed, but instead fitted using flexible piecewise-linear splines. The resulting stress functions reproduce the time series of conductance across a wide range of ecosystems and climates. The VPD stress term resembles that proposed by Oren (i.e., 1-m*log(VPD) ), with VPD measured in kilopascals. The equivalent value of m derived from our spline-fits at each station varied over a remarkably small range of 0.58 to 0.62, in agreement with Oren's original analysis based on leaf and tree-level measurements.

  9. Using modern plant trait relationships between observed and theoretical maximum stomatal conductance and vein density to examine patterns of plant macroevolution.

    PubMed

    McElwain, Jennifer C; Yiotis, Charilaos; Lawson, Tracy

    2016-01-01

    Understanding the drivers of geological-scale patterns in plant macroevolution is limited by a hesitancy to use measurable traits of fossils to infer palaeoecophysiological function. Here, scaling relationships between morphological traits including maximum theoretical stomatal conductance (gmax ) and leaf vein density (Dv ) and physiological measurements including operational stomatal conductance (gop ), saturated (Asat ) and maximum (Amax ) assimilation rates were investigated for 18 extant taxa in order to improve understanding of angiosperm diversification in the Cretaceous. Our study demonstrated significant relationships between gop , gmax and Dv that together can be used to estimate gas exchange and the photosynthetic capacities of fossils. We showed that acquisition of high gmax in angiosperms conferred a competitive advantage over gymnosperms by increasing the dynamic range (plasticity) of their gas exchange and expanding their ecophysiological niche space. We suggest that species with a high gmax (> 1400 mmol m(-2) s(-1) ) would have been capable of maintaining a high Amax as the atmospheric CO2 declined through the Cretaceous, whereas gymnosperms with a low gmax would experience severe photosynthetic penalty. Expansion of the ecophysiological niche space in angiosperms, afforded by coordinated evolution of high gmax , Dv and increased plasticity in gop , adds further functional insights into the mechanisms driving angiosperm speciation.

  10. Effects of different representations of stomatal conductance response to humidity across the African continent under warmer CO2-enriched climate conditions

    NASA Astrophysics Data System (ADS)

    Sato, Hisashi; Kumagai, Tomo'omi; Takahashi, Atsuhiro; Katul, Gabriel G.

    2015-05-01

    General circulation models (GCMs) forecast higher global vapor pressure deficit (VPD) but unchanged global relative humidity (RH) in future climates. A literature survey revealed that 50% of Earth system models and land surface models embedded within GCMs employ RH as an atmospheric aridity index when describing stomatal conductance (gs), whereas the remaining 50% employ VPD. The consequences of using RH or VPD in gs models for water cycling and vegetation productivity in future climates on large spatial and temporal scales remain to be explored. Process-based global dynamic vegetation model runs, changes in the hydrological cycle, and concomitant vegetation productivity for the 21st century projected climate were conducted by altering only gs responses to VPD or RH and not changing any other formulations. In the simulations of the African continent under a 21st century warming trend, both stomatal functions of VPD and RH resulted in similar geographic patterns in gross primary production (GPP). However, continental total GPP was larger for the VPD response than that for the RH response. Transpiration rates were lower, resulting in a 13% increase in water-use efficiency for the VPD response compared with its RH counterpart.

  11. Using modern plant trait relationships between observed and theoretical maximum stomatal conductance and vein density to examine patterns of plant macroevolution.

    PubMed

    McElwain, Jennifer C; Yiotis, Charilaos; Lawson, Tracy

    2016-01-01

    Understanding the drivers of geological-scale patterns in plant macroevolution is limited by a hesitancy to use measurable traits of fossils to infer palaeoecophysiological function. Here, scaling relationships between morphological traits including maximum theoretical stomatal conductance (gmax ) and leaf vein density (Dv ) and physiological measurements including operational stomatal conductance (gop ), saturated (Asat ) and maximum (Amax ) assimilation rates were investigated for 18 extant taxa in order to improve understanding of angiosperm diversification in the Cretaceous. Our study demonstrated significant relationships between gop , gmax and Dv that together can be used to estimate gas exchange and the photosynthetic capacities of fossils. We showed that acquisition of high gmax in angiosperms conferred a competitive advantage over gymnosperms by increasing the dynamic range (plasticity) of their gas exchange and expanding their ecophysiological niche space. We suggest that species with a high gmax (> 1400 mmol m(-2) s(-1) ) would have been capable of maintaining a high Amax as the atmospheric CO2 declined through the Cretaceous, whereas gymnosperms with a low gmax would experience severe photosynthetic penalty. Expansion of the ecophysiological niche space in angiosperms, afforded by coordinated evolution of high gmax , Dv and increased plasticity in gop , adds further functional insights into the mechanisms driving angiosperm speciation. PMID:26230251

  12. Modeling daily gas exchange of a Douglas-fir forest: comparison of three stomatal conductance models with and without a soil water stress function.

    PubMed

    Van Wijk, M. T.; Dekker, S. C.; Bouten, W.; Bosveld, F. C.; Kohsiek, W.; Kramer, K.; Mohren, G. M. J.

    2000-01-01

    Modeling stomatal conductance is a key element in predicting tree growth and water use at the stand scale. We compared three commonly used models of stomatal conductance, the Jarvis-Loustau, Ball-Berry and Leuning models, for their suitability for incorporating soil water stress into their formulation, and for their performance in modeling forest ecosystem fluxes. We optimized the parameters of each of the three models with sap flow and soil water content data. The optimized Ball-Berry model showed clear relationships with air temperature and soil water content, whereas the optimized Leuning and Jarvis-Loustau models only showed a relationship with soil water content. We conclude that use of relative humidity instead of vapor pressure deficit, as in the Ball-Berry model, is not suitable for modeling daily gas exchange in Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) in the Speulderbos forest near the village of Garderen, The Netherlands. Based on the calculated responses to soil water content, we linked a model of forest growth, FORGRO, with a model of soil water, SWIF, to obtain a forest water-balance model that satisfactorily simulated carbon and water (transpiration) fluxes and soil water contents in the Douglas-fir forest for 1995.

  13. How well do stomatal conductance models perform on closing plant carbon budgets? A test using seedlings grown under current and elevated air temperatures

    NASA Astrophysics Data System (ADS)

    Way, Danielle A.; Oren, Ram; Kim, Hyun-Seok; Katul, Gabriel G.

    2011-12-01

    Future carbon and water fluxes within terrestrial ecosystems will be determined by how stomatal conductance (gs) responds to rising atmospheric CO2and air temperatures. While both short- and long-term CO2 effects on gs have been repeatedly studied, there are few studies on how gs acclimates to higher air temperatures. Six gs models were parameterized using leaf gas exchange data from black spruce (Picea mariana) seedlings grown from seed at ambient (22/16°C day/night) or elevated (30/24°C) air temperatures. Model performance was independently assessed by how well carbon gain from each model reproduced estimated carbon costs to close the seedlings' seasonal carbon budgets, a `long-term' indicator of success. A model holding a constant intercellular to ambient CO2ratio and the Ball-Berry model (based on stomatal responses to relative humidity) could not close the carbon balance for either treatment, while the Jarvis-Oren model (based on stomatal responses to vapor pressure deficit,D) and a model assuming a constant gs each closed the carbon balance for one treatment. Two models, both based on gs responses to D, performed best overall, estimating carbon uptake within 10% of carbon costs for both treatments: the Leuning model and a linear optimization model that maximizes carbon gain per unit water loss. Since gsresponses in the optimization model are not a priori assumed, this approach can be used in modeling land-atmosphere exchange of CO2 and water in future climates.

  14. How well do stomatal conductance models perform on closing plant carbon budgets? A test using seedlings grown under current and elevated air temperatures

    NASA Astrophysics Data System (ADS)

    Way, D.; Oren, R.; Kim, H.; Katul, G. G.

    2011-12-01

    Future carbon and water fluxes within terrestrial ecosystems will be determined by how stomatal conductance (gs) responds to rising atmospheric CO2 and air temperatures. While both short- and long-term CO2 effects on gs have been repeatedly studied, there are few studies on how gs acclimates to higher air temperatures. Six gs models were parameterized using leaf gas exchange data from black spruce (Picea mariana) seedlings grown from seed at ambient (22/16 °C day/night) or elevated (30/24 °C) temperatures. Model performance was independently assessed by how well carbon gain from each model reproduced estimated carbon costs to close the seedlings' seasonal carbon budgets, an indicator of the model success at time scales commensurate with biomass changes. A model holding a constant intercellular to ambient CO2 concentration ratio and the Ball-Berry model (based on stomatal responses to relative humidity) could not close the carbon balance for either treatment, while a so-called Jarvis-Oren model (based on stomatal responses to vapor pressure deficit, D) and a model assuming a constant gs each closed the carbon balance for one temperature treatment. Two models, both based on gs responses to D, performed best overall, estimating carbon uptake within 10% of carbon costs for both treatments: the Leuning model (a semi-empirical model that links gs to photosynthetic rates) and a linear optimization model that maximizes carbon gain per unit water loss. Since gs responses in the linear optimization model are not a priori assumed, this approach may be advantageous in modeling gs responses to temperature, especially in future climates.

  15. 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

  16. Uptake of NO, NO 2 and O 3 by sunflower ( Helianthus annuus L.) and tobacco plants ( Nicotiana tabacum L.): dependence on stomatal conductivity

    NASA Astrophysics Data System (ADS)

    Neubert, A.; Kley, D.; Wildt, J.; Segschneider, H. J.; Förstel, H.

    The uptake of NO, NO 2 and O 3 by sunflowers ( Helianthus annuus L. var. giganteus) and tobacco plants ( Nicotiana tabacum L. var. Bel W3), using concentrations representative for moderately polluted air, has been determined by gas exchange experiments. Conductivities for these trace gases were measured at different light fluxes ranging from 820 μEm -2s -1 to darkness. The conductivities to water vapor and the trace gases are highly correlated. It is concluded that the uptake of NO, NO 2 and O 3 by sunflowers and tobacco plants is linearly dependent on stomatal opening. While the uptake of NO is limited by the mesophyll resistance, the uptake of NO 2 is only by diffusion through the stomata. Loss processes by deposition to the leaf surfaces are more pronounced for O 3 than for NO and NO 2.

  17. Effects of Diffuse Light on Radiation Use Efficiency of Two Anthurium Cultivars Depend on the Response of Stomatal Conductance to Dynamic Light Intensity

    PubMed Central

    Li, Tao; Kromdijk, Johannes; Heuvelink, Ep; van Noort, F. R.; Kaiser, Elias; Marcelis, Leo F. M.

    2016-01-01

    The stimulating effect of diffuse light on radiation use efficiency (RUE) of crops is often explained by the more homogeneous spatial light distribution, while rarely considering differences in temporal light distribution at leaf level. This study investigated whether diffuse light effects on crop RUE can be explained by dynamic responses of leaf photosynthesis to temporal changes of photosynthetic photon flux density (PPFD). Two Anthurium andreanum cultivars (‘Pink Champion’ and ‘Royal Champion’) were grown in two glasshouses covered by clear (control) and diffuse glass, with similar light transmission. On clear days, diffusing the light resulted in less temporal fluctuations of PPFD. Stomatal conductance (gs) varied strongly in response to transient PPFD in ‘Royal Champion,’ whereas it remained relatively constant in ‘Pink Champion.’ Instantaneous net leaf photosynthesis (Pn) in both cultivars approached steady state Pn in diffuse light treatment. In control treatment this only occurred in ‘Pink Champion.’ These cultivar differences were reflected by a higher RUE (8%) in ‘Royal Champion’ in diffuse light treatment compared with control, whereas no effect on RUE was observed in ‘Pink Champion.’ We conclude that the stimulating effect of diffuse light on RUE depends on the stomatal response to temporal PPFD fluctuations, which response is cultivar dependent. PMID:26870071

  18. Effects of Diffuse Light on Radiation Use Efficiency of Two Anthurium Cultivars Depend on the Response of Stomatal Conductance to Dynamic Light Intensity.

    PubMed

    Li, Tao; Kromdijk, Johannes; Heuvelink, Ep; van Noort, F R; Kaiser, Elias; Marcelis, Leo F M

    2016-01-01

    The stimulating effect of diffuse light on radiation use efficiency (RUE) of crops is often explained by the more homogeneous spatial light distribution, while rarely considering differences in temporal light distribution at leaf level. This study investigated whether diffuse light effects on crop RUE can be explained by dynamic responses of leaf photosynthesis to temporal changes of photosynthetic photon flux density (PPFD). Two Anthurium andreanum cultivars ('Pink Champion' and 'Royal Champion') were grown in two glasshouses covered by clear (control) and diffuse glass, with similar light transmission. On clear days, diffusing the light resulted in less temporal fluctuations of PPFD. Stomatal conductance (g s) varied strongly in response to transient PPFD in 'Royal Champion,' whereas it remained relatively constant in 'Pink Champion.' Instantaneous net leaf photosynthesis (P n) in both cultivars approached steady state P n in diffuse light treatment. In control treatment this only occurred in 'Pink Champion.' These cultivar differences were reflected by a higher RUE (8%) in 'Royal Champion' in diffuse light treatment compared with control, whereas no effect on RUE was observed in 'Pink Champion.' We conclude that the stimulating effect of diffuse light on RUE depends on the stomatal response to temporal PPFD fluctuations, which response is cultivar dependent.

  19. Regulation of photosynthesis and stomatal and mesophyll conductance under water stress and recovery in olive trees: correlation with gene expression of carbonic anhydrase and aquaporins.

    PubMed

    Perez-Martin, Alfonso; Michelazzo, Chiara; Torres-Ruiz, Jose M; Flexas, Jaume; Fernández, José E; Sebastiani, Luca; Diaz-Espejo, Antonio

    2014-07-01

    The hypothesis that aquaporins and carbonic anhydrase (CA) are involved in the regulation of stomatal (g s) and mesophyll (g m) conductance to CO2 was tested in a short-term water-stress and recovery experiment in 5-year-old olive plants (Olea europaea) growing outdoors. The evolution of leaf gas exchange, chlorophyll fluorescence, and plant water status, and a quantitative analysis of photosynthesis limitations, were followed during water stress and recovery. These variables were correlated with gene expression of the aquaporins OePIP1.1 and OePIP2.1, and stromal CA. At mild stress and at the beginning of the recovery period, stomatal limitations prevailed, while the decline in g m accounted for up to 60% of photosynthesis limitations under severe water stress. However, g m was restored to control values shortly after rewatering, facilitating the recovery of the photosynthetic rate. CA was downregulated during water stress and upregulated after recovery. The use of structural equation modelling allowed us to conclude that both OePIP1.1 and OePIP2.1 expression could explain most of the variations observed for g s and g m. CA expression also had a small but significant effect on g m in olive under water-stress conditions. PMID:24799563

  20. Regulation of photosynthesis and stomatal and mesophyll conductance under water stress and recovery in olive trees: correlation with gene expression of carbonic anhydrase and aquaporins

    PubMed Central

    Perez-Martin, Alfonso; Michelazzo, Chiara; Torres-Ruiz, Jose M.; Flexas, Jaume; Fernández, José E.; Sebastiani, Luca; Diaz-Espejo, Antonio

    2014-01-01

    The hypothesis that aquaporins and carbonic anhydrase (CA) are involved in the regulation of stomatal (g s) and mesophyll (g m) conductance to CO2 was tested in a short-term water-stress and recovery experiment in 5-year-old olive plants (Olea europaea) growing outdoors. The evolution of leaf gas exchange, chlorophyll fluorescence, and plant water status, and a quantitative analysis of photosynthesis limitations, were followed during water stress and recovery. These variables were correlated with gene expression of the aquaporins OePIP1.1 and OePIP2.1, and stromal CA. At mild stress and at the beginning of the recovery period, stomatal limitations prevailed, while the decline in g m accounted for up to 60% of photosynthesis limitations under severe water stress. However, g m was restored to control values shortly after rewatering, facilitating the recovery of the photosynthetic rate. CA was downregulated during water stress and upregulated after recovery. The use of structural equation modelling allowed us to conclude that both OePIP1.1 and OePIP2.1 expression could explain most of the variations observed for g s and g m. CA expression also had a small but significant effect on g m in olive under water-stress conditions. PMID:24799563

  1. Water deficit in field-grown Gossypium hirsutum primarily limits net photosynthesis by decreasing stomatal conductance, increasing photorespiration, and increasing the ratio of dark respiration to gross photosynthesis.

    PubMed

    Chastain, Daryl R; Snider, John L; Collins, Guy D; Perry, Calvin D; Whitaker, Jared; Byrd, Seth A

    2014-11-01

    Much effort has been expended to improve irrigation efficiency and drought tolerance of agronomic crops; however, a clear understanding of the physiological mechanisms that interact to decrease source strength and drive yield loss has not been attained. To elucidate the underlying mechanisms contributing to inhibition of net carbon assimilation under drought stress, three cultivars of Gossypium hirsutum were grown in the field under contrasting irrigation regimes during the 2012 and 2013 growing season near Camilla, Georgia, USA. Physiological measurements were conducted on three sample dates during each growing season (providing a broad range of plant water status) and included, predawn and midday leaf water potential (ΨPD and ΨMD), gross and net photosynthesis, dark respiration, photorespiration, and chlorophyll a fluorescence. End-of-season lint yield was also determined. ΨPD ranged from -0.31 to -0.95MPa, and ΨMD ranged from -1.02 to -2.67MPa, depending upon irrigation regime and sample date. G. hirsutum responded to water deficit by decreasing stomatal conductance, increasing photorespiration, and increasing the ratio of dark respiration to gross photosynthesis, thereby limiting PN and decreasing lint yield (lint yield declines observed during the 2012 growing season only). Conversely, even extreme water deficit, causing a 54% decline in PN, did not negatively affect actual quantum yield, maximum quantum yield, or photosynthetic electron transport. It is concluded that PN is primarily limited in drought-stressed G. hirsutum by decreased stomatal conductance, along with increases in respiratory and photorespiratory carbon losses, not inhibition or down-regulation of electron transport through photosystem II. It is further concluded that ΨPD is a reliable indicator of drought stress and the need for irrigation in field-grown cotton.

  2. Water deficit in field-grown Gossypium hirsutum primarily limits net photosynthesis by decreasing stomatal conductance, increasing photorespiration, and increasing the ratio of dark respiration to gross photosynthesis.

    PubMed

    Chastain, Daryl R; Snider, John L; Collins, Guy D; Perry, Calvin D; Whitaker, Jared; Byrd, Seth A

    2014-11-01

    Much effort has been expended to improve irrigation efficiency and drought tolerance of agronomic crops; however, a clear understanding of the physiological mechanisms that interact to decrease source strength and drive yield loss has not been attained. To elucidate the underlying mechanisms contributing to inhibition of net carbon assimilation under drought stress, three cultivars of Gossypium hirsutum were grown in the field under contrasting irrigation regimes during the 2012 and 2013 growing season near Camilla, Georgia, USA. Physiological measurements were conducted on three sample dates during each growing season (providing a broad range of plant water status) and included, predawn and midday leaf water potential (ΨPD and ΨMD), gross and net photosynthesis, dark respiration, photorespiration, and chlorophyll a fluorescence. End-of-season lint yield was also determined. ΨPD ranged from -0.31 to -0.95MPa, and ΨMD ranged from -1.02 to -2.67MPa, depending upon irrigation regime and sample date. G. hirsutum responded to water deficit by decreasing stomatal conductance, increasing photorespiration, and increasing the ratio of dark respiration to gross photosynthesis, thereby limiting PN and decreasing lint yield (lint yield declines observed during the 2012 growing season only). Conversely, even extreme water deficit, causing a 54% decline in PN, did not negatively affect actual quantum yield, maximum quantum yield, or photosynthetic electron transport. It is concluded that PN is primarily limited in drought-stressed G. hirsutum by decreased stomatal conductance, along with increases in respiratory and photorespiratory carbon losses, not inhibition or down-regulation of electron transport through photosystem II. It is further concluded that ΨPD is a reliable indicator of drought stress and the need for irrigation in field-grown cotton. PMID:25151126

  3. Inverse Estimation of Parameters for a Coupled Photosynthesis and Stomatal Conductance Model Using Eddy Covariance Measurements at a Black Spruce Forest in Alaska

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    For better understanding high-latitude carbon and water cycles, parameters of a coupled photosynthesis and stomatal conductance big-leaf model (Farquhar et al., 1980; Ball and Berry, 1987; Baldocchi, 1994) were inversely estimated using gross primary productivity (GPP) and evapotranspiration by eddy covariance measurements at a black spruce forest in interior Alaska (Iwata et al., 2012; Ueyama et al., 2014). We developed a sequential optimization method based on a global optimization technique; shuffled complex evolution (SCE-UA) method (Duan et al., 1993). First, photosynthetic parameters (maximum carboxylation and maximum electron transfer rate at 25oC; Vcmax25 and Jmax25) were optimized for GPP, and then stomatal conductance parameters (m and b in the Ball-Berry model) were optimized for evapotranspiration. Based on our optimization, Vcmax25, Jmax25, and m varied seasonally, but b value was almost constant throughout seasons. Vcmax25 and Jmax25 were higher in summer months than other months, which related to understory leaf area index. m was higher in winter months than other months, but did not significantly change throughout the growing season. Our results indicated that simulations using constant ecophysiological parameters could underestimate photosynthesis and evapotranspiration of high-latitude ecosystems. References Ball and Berry, 1987: Progress in Photosynthesis Research, pp 221-224. Baldocchi, 1994: Tree Physiol., 14, 1069-1079. Duan et al., 1993: J. Optimization Theory and Applications, 76, 501-521. Farquhar et al., 1980: Planta, 149, 78-90. Iwata et al., 2012: Agric. For. Meteorol., 161, 107-115. Ueyama et al., 2014: Global Change Biol., 20, 1161-1173.

  4. Soil nitrogen limitation does not impact nighttime water loss in Populus.

    PubMed

    Howard, Ava R; Donovan, Lisa A

    2010-01-01

    Nighttime transpirational water loss from C(3) trees occurs without carbon gain and is both common and substantial. However, the magnitude of this water loss varies and a better understanding of the environmental factors driving this variation is needed. We investigated the response of nighttime conductance (g(night)) and transpiration (E(night)) to soil nitrogen limitation. We used instantaneous gas exchange measurements in greenhouse studies of Populus angustifolia James (narrowleaf cottonwood) and Populus balsamifera L. spp. trichocarpa (Torr. & A. Gray ex Hook.) Brayshaw (black cottonwood). g(night) for sufficiently watered plants ranged from 0.045 to 0.308 mol m(-2) s(-1) for P. balsamifera and 0.037 to 0.188 mol m(-2) s(-1) for P. angustifolia, which was much larger than minimum leaf conductance (g(min); up to 0.005 mol m(-2) s(-1) in the dark). Long-term nitrogen limitation sufficient to substantially reduce biomass did not affect g(night) or E(night) when potentially confounding water stress effects were eliminated. We conclude that nighttime water loss from two Populus species is large and although it is under stomatal control is not regulated at night in response to soil nitrogen availability.

  5. Stomatal Conductance, Plant Species Distribution, and an Exploration of Rhizosphere Microbes and Mycorrhizae at a Deliberately Leakimg Experimental Carbon Sequestration Field (ZERT)

    NASA Astrophysics Data System (ADS)

    Sharma, B.; Apple, M. E.; Morales, S.; Zhou, X.; Holben, B.; Olson, J.; Prince, J.; Dobeck, L.; Cunningham, A. B.; Spangler, L.

    2010-12-01

    One measure to reduce atmospheric CO2 is to sequester it in deep geological formations. Rapid surface detection of any CO2 leakage is crucial. CO2 leakage rapidly affects vegetation above sequestration fields. Plant responses to high CO2 are valuable tools in surface detection of leaking CO2. The Zero Emission Research Technology (ZERT) site in Bozeman, MT is an experimental field for surface detection of CO2 where 0.15 ton/day of CO2 was released (7/19- 8/15/2010) from a 100m horizontal injection well, HIW, 1.5 m underground with deliberate leaks of CO2 at intervals, and from a vertical injector, VI, (6/3-6/24/2010). The vegetation includes Taraxacum officinale (Dandelion), Dactylis glomerata (Orchard Grass), and other herbaceous plants. We collected soil and roots 1, 3 and 5 m from the VI to determine the responses of mycorrhizal fungi and rhizosphere microbes to high CO2. Mycorrhizal fungi obtain C from root exudates, increase N and P availability, and reduce desiccation, while prokaryotic rhizosphere microbes fix atmospheric N and will be examined for abundance and expression of carbon and nitrogen cycling genes. We are quantifying mycorrhizal colonization and the proportion of spores, hyphae, and arbuscules in vesicular-arbuscular mycorrhizae (VAM) in cleared and stained roots. Stomatal conductance is an important measure of CO2 uptake and water loss via transpiration. We used a porometer (5-40°C, 0-90% RH, Decagon) to measure stomatal conductivity in dandelion and orchard grass at 1, 3, and 5 m from the VI and along a transect perpendicular to the HIW. Dandelion conductance was highest close to the VI and almost consistently higher close to hot spots (circular regions with maximum CO2 and leaf dieback) at the HIW, with 23.2 mmol/m2/s proximal to the hot spot, and 10.8 mmol/m2/s distally. Average conductance in grass (50.3 mmol/m2/s) was higher than in dandelion, but grass did not have high conductance near hot spots. Stomata generally close at elevated CO2

  6. An Integrated View of Whole-Tree Hydraulic Architecture. Does Stomatal or Hydraulic Conductance Determine Whole Tree Transpiration?

    PubMed

    Rodríguez-Gamir, Juan; Primo-Millo, Eduardo; Forner-Giner, María Ángeles

    2016-01-01

    Hydraulic conductance exerts a strong influence on many aspects of plant physiology, namely: transpiration, CO2 assimilation, growth, productivity or stress response. However we lack full understanding of the contribution of root or shoot water transport capacity to the total water balance, something which is difficult to study in trees. Here we tested the hypothesis that whole plant hydraulic conductance modulates plant transpiration using two different seedlings of citrus rootstocks, Poncirus trifoliata (L.) Raf. and Cleopatra mandarin (Citrus reshni Hort ex Tan.). The two genotypes presented important differences in their root or shoot hydraulic conductance contribution to whole plant hydraulic conductance but, even so, water balance proved highly dependent on whole plant conductance. Further, we propose there is a possible equilibrium between root and shoot hydraulic conductance, similar to that between shoot and root biomass production, which could be related with xylem anatomy.

  7. An Integrated View of Whole-Tree Hydraulic Architecture. Does Stomatal or Hydraulic Conductance Determine Whole Tree Transpiration?

    PubMed Central

    Rodríguez-Gamir, Juan; Primo-Millo, Eduardo; Forner-Giner, María Ángeles

    2016-01-01

    Hydraulic conductance exerts a strong influence on many aspects of plant physiology, namely: transpiration, CO2 assimilation, growth, productivity or stress response. However we lack full understanding of the contribution of root or shoot water transport capacity to the total water balance, something which is difficult to study in trees. Here we tested the hypothesis that whole plant hydraulic conductance modulates plant transpiration using two different seedlings of citrus rootstocks, Poncirus trifoliata (L.) Raf. and Cleopatra mandarin (Citrus reshni Hort ex Tan.). The two genotypes presented important differences in their root or shoot hydraulic conductance contribution to whole plant hydraulic conductance but, even so, water balance proved highly dependent on whole plant conductance. Further, we propose there is a possible equilibrium between root and shoot hydraulic conductance, similar to that between shoot and root biomass production, which could be related with xylem anatomy. PMID:27223695

  8. Effects of Salinity on Stomatal Conductance, Photosynthetic Capacity, and Carbon Isotope Discrimination of Salt-Tolerant (Gossypium hirsutum L.) and Salt-Sensitive (Phaseolus vulgaris L.) C3 Non-Halophytes

    PubMed Central

    Brugnoli, Enrico; Lauteri, Marco

    1991-01-01

    The effects of salinity on growth, stomatal conductance, photosynthetic capacity, and carbon isotope discrimination (Δ) of Gossypium hirsutum L. and Phaseolus vulgaris L. were evaluated. Plants were grown at different NaCl concentrations from 10 days old until mature reproductive structures were formed. Plant growth and leaf area development were strongly reduced by salinity, in both cotton and bean. Stomatal conductance also was reduced by salinity. The Δ always declined with increasing external salinity concentration, indicating that stomatal limitation of photosynthesis was increased. In cotton plant dry matter, Δ correlated with the ratio of intercellular to atmospheric CO2 partial pressures (pl/pa) calculated by gas exchange. This correlation was not clear in bean plants, although Δ showed a more pronounced salt induced decline in bean than in cotton. Possible effects of heterogeneity of stomatal aperture and consequent overestimation of pl as determined from gas exchange could explain these results. Significant differences of Δ between leaf and seed material were observed in cotton and bean. This suggests different patterns of carbon allocation between leaves and seeds. The photon yield of O2 evolution determined at rate-limiting photosynthetic photon flux density was insensitive to salinity in both species analyzed. The light- and CO2-saturated rate of CO2 uptake and O2 evolution showed a salt induced decline in both species. Possible explanations of this observation are discussed. O2 hypersensitivity was observed in salt stressed cotton plants. These results clearly demonstrate that the effect of salinity on assimilation rate was mostly due to the reduction of stomatal conductance, and that calculation of pl may be overestimated in salt stressed plants, because of heterogeneity of stomatal aperture over the leaf surface. PMID:16668029

  9. Nighttime IR Ejecta

    NASA Technical Reports Server (NTRS)

    2004-01-01

    [figure removed for brevity, see original site]

    Today's crater is slightly older than one shown yesterday. The ballistically emplaced ejecta is now a uniform gray tone in this nighttime IR image. With time dust will cover young surfaces and control the IR image tone. This crater is located east of Huygens Crater.

    Image information: IR instrument. Latitude -10.6, Longitude 64.3 East (295.7 West). 100 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  10. Towards an improved and more flexible representation of water stress in coupled photosynthesis-stomatal conductance models; implications for simulated land surface fluxes and variables at various spatiotemporal scales

    NASA Astrophysics Data System (ADS)

    Egea, G.; Verhoef, A.; Vidale, P. L.; Black, E.; Van den Hoof, C.

    2012-04-01

    Coupled photosynthesis-stomatal conductance (A-gs) models are commonly used in ecosystem models to represent the exchange rate of CO2 and H2O between vegetation and the atmosphere. The ways these models account for water stress differ greatly among modelling schemes. This study provides insight into the impact of contrasting model configurations of water stress on the simulated leaf-level values of net photosynthesis (A), stomatal conductance (gs), the functional relationship among them and their ratio, the intrinsic water use efficiency (A/gs), as soil dries. A simple, yet versatile, normalized soil moisture dependent function was used to account for the effects of water stress on gs, on mesophyll conductance (gm ) and on the biochemical capacity (Egea et al., 2011). Model output was compared to leaf-level values obtained from the literature. The sensitivity analyses emphasized the necessity to combine both stomatal and non-stomatal limitations of A in coupled A-gs models to accurately capture the observed functional relationships A vs. gs and A/gs vs. gs in response to drought. Accounting for water stress in coupled A-gs models by imposing either stomatal or biochemical limitations of A, as commonly practiced in most ecosystem models, failed to reproduce the observed functional relationship between key leaf gas exchange attributes. A quantitative limitation analysis revealed that the general pattern of C3 photosynthetic response to water stress can be represented in coupled A-gs models by imposing the highest limitation strength to mesophyll conductance, then to stomatal conductance and finally to the biochemical capacity. This more realistic representation of soil water stress on the simulated leaf-level values of A and gs was embedded in the JULES (Joint UK Land Environment Simulator; Best et al., 2011), model and tested for a number of vegetation types, for which driving and flux verification data were available. These simulations provide an insight into the

  11. Arbuscular mycorrhizal symbiosis alters stomatal conductance of host plants more under drought than under amply watered conditions: a meta-analysis.

    PubMed

    Augé, Robert M; Toler, Heather D; Saxton, Arnold M

    2015-01-01

    Stomata regulate rates of carbon assimilation and water loss. Arbuscular mycorrhizal (AM) symbioses often modify stomatal behavior and therefore play pivotal roles in plant productivity. The size of the AM effect on stomatal conductance to water vapor (g s ) has varied widely, has not always been apparent, and is unpredictable. We conducted a meta-analysis of 460 studies to determine the size of the AM effect under ample watering and drought and to examine how experimental conditions have influenced the AM effect. Across all host and symbiont combinations under all soil moisture conditions, AM plants have shown 24 % higher g s than nonmycorrhizal (NM) controls. The promotion of g s has been over twice as great during moderate drought than under amply watered conditions. The AM influence on g s has been even more pronounced under severe drought, with over four times the promotion observed with ample water. Members of the Claroideoglomeraceae, Glomeraceae, and other AM families stimulated g s by about the same average amount. Colonization by native AM fungi has produced the largest promotion. Among single-AM symbionts, Glomus deserticola, Claroideoglomus etunicatum, and Funneliformis mosseae have had the largest average effects on g s across studies. Dicotyledonous hosts, especially legumes, have been slightly more responsive to AM symbiosis than monocotyledonous hosts, and C3 plants have shown over twice the AM-induced promotion of C4 plants. The extent of root colonization is important, with heavily colonized plants showing ×10 the g s promotion of lightly colonized plants. AM promotion of g s has been larger in growth chambers and in the field than in greenhouse studies, almost ×3 as large when plants were grown under high light than low light, and ×2.5 as large in purely mineral soils than in soils having an organic component. When AM plants have been compared with NM controls given NM pot culture, they have shown only half the promotion of g s as NM plants

  12. Allelic variation in the vacuolar TPK1 channel affects its calcium dependence and may impact on stomatal conductance.

    PubMed

    Hartley, Tom N; Maathuis, Frans J M

    2016-01-01

    Natural variation can be exploited to identify allelic variants of proteins. In this study, patch clamp was used to determine transport properties of two AtTPK1 alleles from Landsberg and Kas-2 ecotypes. No difference in conductance or ion selectivity was observed but the Kas version of TPK1 showed different Ca(2+) dependence in its open probability compared to Ler. Leaves from Kas showed lower rates of water loss than those of Ler, in either the absence or presence of ABA, an observation that is consistent with higher TPK1 channel activity at comparable cytoplasmic Ca(2+) concentrations. A model that explains the results is presented. PMID:26765783

  13. Nighttime sporadic-E.

    NASA Technical Reports Server (NTRS)

    Beer, T.; Moorcroft, D. R.

    1972-01-01

    At night, internal atmospheric gravity waves are able to induce drift instabilities in the ionospheric plasma. Nighttime constant height type sporadic-E(Esc) may then be explained as an effect due to the combined effect of ionization movement due to the wind shear mechanism and due to the cross-field gradient drifts. This combined concept provides a qualitative explanation of the rocket observed nighttime electron density profiles, of the speeds of the Esc irregularities and of the variations of Esc with latitude and electric field strength.-

  14. Nighttime in dreams.

    PubMed

    Schredl, Michael; Knoth, Inga Sophia

    2012-04-01

    Based on the continuity hypothesis of dreaming, a study was designed to examine whether time of day within the dream was related to dream emotions. A sample of 1,612 dreams reported by 444 participants was analyzed. As predicted, dream scenarios set at nighttime were associated with less positive and more negative emotions compared to dream scenarios set at other times of the day. In order to pursue this line of research, it would be fruitful to study the dreams of persons with specific nighttime fears.

  15. Drought tolerance, xylem sap abscisic acid and stomatal conductance during soil drying: a comparison of young plants of four temperate deciduous angiosperms.

    PubMed

    Loewenstein, Nancy J.; Pallardy, Stephen G.

    1998-07-01

    Patterns of water relations, xylem sap abscisic acid (ABA) concentration ([ABA]) and stomatal aperture were compared in drought-sensitive black walnut (Juglans nigra L.) and black willow (Salix nigra Marsh.), less drought-sensitive sugar maple (Acer saccharum Marsh.) and drought-tolerant white oak (Quercus alba L.). Strong correlations among reduction in predawn water potential, increase in xylem sap [ABA] and stomatal closure were observed in all species. Stomatal response was more highly correlated with xylem [ABA] than with ABA flux. Xylem sap pH and ion concentrations appeared not to play a major role in the stomatal response of these species. Stomata were more sensitive to relative changes in [ABA] in drought-sensitive black walnut and black willow than in sugar maple and white oak. In the early stages of drought, increased [ABA] in the xylem sap of black walnut and black willow was probably of root origin and provided a signal to the shoot of the water status of the roots. In sugar maple and white oak, leaf water potential declined with the onset of stomatal closure, so that stomatal closure also may have occurred in response to the change in leaf water potential.

  16. Using combined measurements for comparison of light induction of stomatal conductance, electron transport rate and CO2 fixation in woody and fern species adapted to different light regimes.

    PubMed

    Wong, Shau-Lian; Chen, Chung-Wei; Huang, Hsien-Wen; Weng, Jen-Hsien

    2012-05-01

    We aimed to understand the relation of photosynthetic rate (A) with g(s) and electron transport rate (ETR) in species of great taxonomic range and light adaptation capability during photosynthetic light induction. We studied three woody species (Alnus formosana, Ardisia crenata and Ardisia cornudentata) and four fern species (Pyrrosia lingus, Asplenium antiquum, Diplazium donianum and Archangiopteris somai) with different light adaptation capabilities. Pot-grown materials received 100 and/or 10% sunlight according to their light adaptation capabilities. At least 4 months after light acclimation, CO(2) and H(2)O exchange and chlorophyll fluorescence were measured simultaneously by equipment in the laboratory. In plants adapted or acclimated to low light, dark-adapted leaves exposed to 500 or 2000 µmol m(-2) s(-1) photosynthetic photon flux (PPF) for 30 min showed low gross photosynthetic rate (P(g)) and short time required to reach 90% of maximum P(g) (). At the initiation of illumination, two broad-leaved understory shrubs and the four ferns, especially ferns adapted to heavy shade, showed higher stomatal conductance (g(s)) than pioneer tree species; materials with higher g(s) had short at both 500 and 2000 µmol m(-2) s(-1) PPF. With 500 or 2000 µmol m(-2) s(-1) PPF, the g(s) for the three woody species increased from 2 to 30 min after the start of illumination, but little change in the g(s) of the four ferns. Thus, P(g) and g(s) were not correlated for all material measured at the same PPF and induction time. However, P(g) was positively correlated with ETR, even though CO(2) assimilation may be influenced by stomatal, biochemical and photoinhibitory limitations. In addition, was closely related to time required to reach 90% maximal ETR for all materials and with two levels of PPF combined. Thus, ETR is a good indicator for estimating the light induction of photosynthetic rate of species, across a wide taxonomic range and light adaptation and acclimation

  17. Separating active and passive influences on stomatal control of transpiration.

    PubMed

    McAdam, Scott A M; Brodribb, Timothy J

    2014-04-01

    Motivated by studies suggesting that the stomata of ferns and lycophytes do not conform to the standard active abscisic acid (ABA) -mediated stomatal control model, we examined stomatal behavior in a conifer species (Metasequoia glyptostroboides) that is phylogenetically midway between the fern and angiosperm clades. Similar to ferns, daytime stomatal closure in response to moderate water stress seemed to be a passive hydraulic process in M. glyptostroboides immediately alleviated by rehydrating excised shoots. Only after prolonged exposure to more extreme water stress did active ABA-mediated stomatal closure become important, because foliar ABA production was triggered after leaf turgor loss. The influence of foliar ABA on stomatal conductance and stomatal aperture was highly predictable and additive with the passive hydraulic influence. M. glyptostroboides thus occupies a stomatal behavior type intermediate between the passively controlled ferns and the characteristic ABA-dependent stomatal closure described in angiosperm herbs. These results highlight the importance of considering phylogeny as a major determinant of stomatal behavior.

  18. Instantaneous-to-daily GPP upscaling schemes based on a coupled photosynthesis-stomatal conductance model: correcting the overestimation of GPP by directly using daily average meteorological inputs.

    PubMed

    Wang, Fumin; Gonsamo, Alemu; Chen, Jing M; Black, T Andrew; Zhou, Bin

    2014-11-01

    Daily canopy photosynthesis is usually temporally upscaled from instantaneous (i.e., seconds) photosynthesis rate. The nonlinear response of photosynthesis to meteorological variables makes the temporal scaling a significant challenge. In this study, two temporal upscaling schemes of daily photosynthesis, the integrated daily model (IDM) and the segmented daily model (SDM), are presented by considering the diurnal variations of meteorological variables based on a coupled photosynthesis-stomatal conductance model. The two models, as well as a simple average daily model (SADM) with daily average meteorological inputs, were validated using the tower-derived gross primary production (GPP) to assess their abilities in simulating daily photosynthesis. The results showed IDM closely followed the seasonal trend of the tower-derived GPP with an average RMSE of 1.63 g C m(-2) day(-1), and an average Nash-Sutcliffe model efficiency coefficient (E) of 0.87. SDM performed similarly to IDM in GPP simulation but decreased the computation time by >66%. SADM overestimated daily GPP by about 15% during the growing season compared to IDM. Both IDM and SDM greatly decreased the overestimation by SADM, and improved the simulation of daily GPP by reducing the RMSE by 34 and 30%, respectively. The results indicated that IDM and SDM are useful temporal upscaling approaches, and both are superior to SADM in daily GPP simulation because they take into account the diurnally varying responses of photosynthesis to meteorological variables. SDM is computationally more efficient, and therefore more suitable for long-term and large-scale GPP simulations.

  19. Wheat cultivars selected for high Fv /Fm under heat stress maintain high photosynthesis, total chlorophyll, stomatal conductance, transpiration and dry matter.

    PubMed

    Sharma, Dew Kumari; Andersen, Sven Bode; Ottosen, Carl-Otto; Rosenqvist, Eva

    2015-02-01

    The chlorophyll fluorescence parameter Fv /Fm reflects the maximum quantum efficiency of photosystem II (PSII) photochemistry and has been widely used for early stress detection in plants. Previously, we have used a three-tiered approach of phenotyping by Fv /Fm to identify naturally existing genetic variation for tolerance to severe heat stress (3 days at 40°C in controlled conditions) in wheat (Triticum aestivum L.). Here we investigated the performance of the previously selected cultivars (high and low group based on Fv /Fm value) in terms of growth and photosynthetic traits under moderate heat stress (1 week at 36/30°C day/night temperature in greenhouse) closer to natural heat waves in North-Western Europe. Dry matter accumulation after 7 days of heat stress was positively correlated to Fv /Fm . The high Fv /Fm group maintained significantly higher total chlorophyll and net photosynthetic rate (PN ) than the low group, accompanied by higher stomatal conductance (gs ), transpiration rate (E) and evaporative cooling of the leaf (ΔT). The difference in PN between the groups was not caused by differences in PSII capacity or gs as the variation in Fv /Fm and intracellular CO2 (Ci ) was non-significant under the given heat stress. This study validated that our three-tiered approach of phenotyping by Fv /Fm performed under increasing severity of heat was successful in identifying wheat cultivars differing in photosynthesis under moderate and agronomically more relevant heat stress. The identified cultivars may serve as a valuable resource for further studies to understand the physiological mechanisms underlying the genetic variability in heat sensitivity of photosynthesis.

  20. The evolution of the role of ABA in the regulation of water-use efficiency: From biochemical mechanisms to stomatal conductance.

    PubMed

    Negin, Boaz; Moshelion, Menachem

    2016-10-01

    Abscisic acid is found in a wide variety of organisms. In the plant kingdom, ABA's role in mediating responses to abiotic stress has been conserved and enhanced throughout evolution. The emergence of plants to terrestrial environments required the development of mechanisms to cope with ongoing and severe abiotic stress such as drought and rapid changes in humidity and temperature. The common understanding is that terrestrial plants evolved strategies ranging from desiccation-tolerance mechanisms (mosses) to drought tolerance (CAM plants), to better exploit different ecological niches. In between these divergent water regulation strategies, ABA plays a significant role in managing plants' adaptation to new environments by optimizing water-use efficiency (WUE) under particular environmental conditions. ABA plays some very different roles in the regulation of WUE. ABA's role in the regulation of guard cells and transpiration has yielded a wide variety of WUE-regulation mechanisms, ranging from no sensitivity (ferns) to low sensitivity (anisohydric behavior) to hypersensitivity to ABA (isohydric behavior and putatively CAM plants). ABA also plays a role in the regulation of non-stomatal, biochemical mechanisms of WUE regulation. In angiosperms, this includes the control of osmotic adjustment and morphological changes, including changes in leaf size, stomatal density, stomatal size and root development. Under severe stress, ABA also appears to initiate leaf senescence via transcriptional regulation, to directly inhibit photosynthesis. PMID:27593466

  1. The evolution of the role of ABA in the regulation of water-use efficiency: From biochemical mechanisms to stomatal conductance.

    PubMed

    Negin, Boaz; Moshelion, Menachem

    2016-10-01

    Abscisic acid is found in a wide variety of organisms. In the plant kingdom, ABA's role in mediating responses to abiotic stress has been conserved and enhanced throughout evolution. The emergence of plants to terrestrial environments required the development of mechanisms to cope with ongoing and severe abiotic stress such as drought and rapid changes in humidity and temperature. The common understanding is that terrestrial plants evolved strategies ranging from desiccation-tolerance mechanisms (mosses) to drought tolerance (CAM plants), to better exploit different ecological niches. In between these divergent water regulation strategies, ABA plays a significant role in managing plants' adaptation to new environments by optimizing water-use efficiency (WUE) under particular environmental conditions. ABA plays some very different roles in the regulation of WUE. ABA's role in the regulation of guard cells and transpiration has yielded a wide variety of WUE-regulation mechanisms, ranging from no sensitivity (ferns) to low sensitivity (anisohydric behavior) to hypersensitivity to ABA (isohydric behavior and putatively CAM plants). ABA also plays a role in the regulation of non-stomatal, biochemical mechanisms of WUE regulation. In angiosperms, this includes the control of osmotic adjustment and morphological changes, including changes in leaf size, stomatal density, stomatal size and root development. Under severe stress, ABA also appears to initiate leaf senescence via transcriptional regulation, to directly inhibit photosynthesis.

  2. VLF nighttime data analysis

    NASA Astrophysics Data System (ADS)

    1991-03-01

    This paper documents a very low frequency/low frequency (VLF/LF) Data Analysis task by the Naval Ocean Systems Center to improve the modeling of the nighttime ionosphere when making propagation predictions with the Long Wave Propagation Capability (LWPC) computer program. The task utilizes an extensive database of VLF measured data recorded during the 1985 to 1986 trips of the merchant ship GTS Callaghan in the North Atlantic area. By constraining the Callaghan data to those periods when both the ship and the distant transmitters were in time zones consistent with all-nighttime propagation, and by eliminating data from trips outside the principal area of interest, an aggregated set of recorded data was assembled for each frequency of concern. Four frequencies were examined: 16.0, 19.0, 21.4 and 24.0 kHz. Recorded data sets were graphed as signal vs. distance plots, computing distance from the transmitter for each ship's location. The LWPC program was then utilized to compute signal vs. distance along a typical path in the same ocean area, and the predicted and recorded data were compared. By changing the LWPC parameters different propagation predictions were compared with the recorded data until a best fit was obtained.

  3. Nighttime solar cell

    SciTech Connect

    Parise, R.J.

    1998-07-01

    Currently photovoltaic (PV) cells convert solar energy into electrical energy at an efficiency of about 18%, with the maximum conversion rate taking place around noon on a cloudless day. In many applications, the PV cells are utilized to recharge a stand-by battery pack that provides electrical energy at night or on cloudy days. Increasing the utilization of the panel array area by producing electrical power at night will reduce the amount of required electrical energy storage for a given array size and increase system reliability. Thermoelectric generators (TEG) are solid state devices that convert thermal energy into electrical energy. Using the nighttime sky, or deep space, with an effective temperature of 3.5 K as a cold sink, the TEG presented here can produce electrical power at night. The hot junction is supplied energy by the ambient air temperature or some other warm temperature source. The cold junction of the TEG is insulated from the surroundings by a vacuum cell, improving its overall effectiveness. Combining the TEG with the PV cell, a unique solid state device is developed that converts electromagnetic radiant energy into usable electrical energy. The thermoelectric-photovoltaic (TEPV) cell, or the Nighttime Solar Cell, is a direct energy conversion device that produces electrical energy both at night and during the day.

  4. Woody clockworks: circadian regulation of night-time water use in Eucalyptus globulus.

    PubMed

    Resco de Dios, Víctor; Díaz-Sierra, Rubén; Goulden, Michael L; Barton, Craig V M; Boer, Matthias M; Gessler, Arthur; Ferrio, Juan Pedro; Pfautsch, Sebastian; Tissue, David T

    2013-11-01

    The role of the circadian clock in controlling the metabolism of entire trees has seldom been considered. We tested whether the clock influences nocturnal whole-tree water use. Whole-tree chambers allowed the control of environmental variables (temperature, relative humidity). Night-time stomatal conductance (gs ) and sap flow (Q) were monitored in 6- to 8-m-tall Eucalyptus globulus trees during nights when environmental variables were kept constant, and also when conditions varied with time. Artificial neural networks were used to quantify the relative importance of circadian regulation of gs and Q. Under a constant environment, gs and Q declined from 0 to 6 h after dusk, but increased from 6 to 12 h after dusk. While the initial decline could be attributed to multiple processes, the subsequent increase is most consistent with circadian regulation of gs and Q. We conclude that endogenous regulation of gs is an important driver of night-time Q under natural environmental variability. The proportion of nocturnal Q variation associated with circadian regulation (23-56%) was comparable to that attributed to vapor pressure deficit variation (25-58%). This study contributes to our understanding of the linkages between molecular and cellular processes related to circadian regulation, and whole-tree processes related to ecosystem gas exchange in the field. PMID:23795820

  5. Woody clockworks: circadian regulation of night-time water use in Eucalyptus globulus.

    PubMed

    Resco de Dios, Víctor; Díaz-Sierra, Rubén; Goulden, Michael L; Barton, Craig V M; Boer, Matthias M; Gessler, Arthur; Ferrio, Juan Pedro; Pfautsch, Sebastian; Tissue, David T

    2013-11-01

    The role of the circadian clock in controlling the metabolism of entire trees has seldom been considered. We tested whether the clock influences nocturnal whole-tree water use. Whole-tree chambers allowed the control of environmental variables (temperature, relative humidity). Night-time stomatal conductance (gs ) and sap flow (Q) were monitored in 6- to 8-m-tall Eucalyptus globulus trees during nights when environmental variables were kept constant, and also when conditions varied with time. Artificial neural networks were used to quantify the relative importance of circadian regulation of gs and Q. Under a constant environment, gs and Q declined from 0 to 6 h after dusk, but increased from 6 to 12 h after dusk. While the initial decline could be attributed to multiple processes, the subsequent increase is most consistent with circadian regulation of gs and Q. We conclude that endogenous regulation of gs is an important driver of night-time Q under natural environmental variability. The proportion of nocturnal Q variation associated with circadian regulation (23-56%) was comparable to that attributed to vapor pressure deficit variation (25-58%). This study contributes to our understanding of the linkages between molecular and cellular processes related to circadian regulation, and whole-tree processes related to ecosystem gas exchange in the field.

  6. A New mouthwash for Chemotherapy Induced Stomatitis

    PubMed Central

    Miranzadeh, Sedigheh; Adib-Hajbaghery, Mohsen; Soleymanpoor, Leyla; Ehsani, Majid

    2014-01-01

    Background: Stomatitis is a disturbing side-effect of chemotherapy that disturbs patients and causes difficulties in patient’s drinking, eating and talking, and may results in infection and bleeding. Objectives: This study aimed to investigate the effect of Yarrow distillate in the treatment of chemotherapy-induced stomatitis. Patients and Methods: This randomized controlled trial study was conducted during 2013. The study population consisted of all cancer patients with chemotherapy-induced oral stomatitis referred to Shahid Beheshti Medical Center, Kashan, Iran. The data collection instrument had two-part; a demographic part and another part recording the severity of the stomatitis at the first, seventh, and 14th days of the intervention based on a WHO criteria checklist in 2005. In this study, 56 patients diagnosed with cancer were randomly assigned into control and experimental groups in similar blocks according to their stomatitis severity. The experimental group gargled 15 mL of a routine solution mixed with Yarrow distillate 4 times a day for 14 days while the control group gargled 15 mL of routine solution. The severity of stomatitis was assessed at the beginning of the intervention, and then after 7 and 14 days of the study. Data were analyzed using chi-square and Fisher exact test, Mann-Whitney U, Kruskal-Wallis, and Friedman tests using SPSS 11.5 software. Results: At first, the median score of stomatitis in the experimental group was 2.50 that significantly reduced to 1 and 0 in days 7 and 14 of the intervention, respectively (P value < 0.001). However, in the control group, the median score of stomatitis was 2.50, which significantly increased to 3 in days 7 and 14 (P value < 0.001). Conclusions: Yarrow distillate-contained solution reduced stomatitis severity more than the routine solution. Therefore, we suggest using it in patients with chemotherapy-induced stomatitis. PMID:25699281

  7. Suppression of nighttime sap flux with lower stem photosynthesis in Eucalyptus trees

    NASA Astrophysics Data System (ADS)

    Gao, Jianguo; Zhou, Juan; Sun, Zhenwei; Niu, Junfeng; Zhou, Cuiming; Gu, Daxing; Huang, Yuqing; Zhao, Ping

    2016-04-01

    It is widely accepted that substantial nighttime sap flux ( J s,n) or transpiration ( E) occurs in most plants, but the physiological implications are poorly known. It has been hypothesized that J s,n or E serves to enhance nitrogen uptake or deliver oxygen; however, no clear evidence is currently available. In this study, sap flux ( J s) in Eucalyptus grandis × urophylla with apparent stem photosynthesis was measured, including control trees which were covered by aluminum foil (approximately 1/3 of tree height) to block stem photosynthesis. We hypothesized that the nighttime water flux would be suppressed in trees with lower stem photosynthesis. The results showed that the green tissue degraded after 3 months, demonstrating a decrease in stem photosynthesis. The daytime J s decreased by 21.47 %, while J s,n decreased by 12.03 % in covered trees as compared to that of control, and the difference was statistically significant ( P < 0.01). The linear quantile regression model showed that J s,n decreased for a given daytime transpiration water loss, indicating that J s,n was suppressed by lower stem photosynthesis in covered trees. Predawn ( ψ pd) of covered trees was marginally higher than that of control while lower at predawn stomatal conductance ( g s), indicating a suppressed water flux in covered trees. There was no difference in leaf carbon content and δ13C between the two groups, while leaf nitrogen content and δ15N were significantly higher in covered trees than that of the control ( P < 0.05), indicating that J s,n was not used for nitrogen uptake. These results suggest that J s,n may act as an oxygen pathway since green tissue has a higher respiration or oxygen demand than non-green tissue. Thus, this study demonstrated the physiological implications of J s,n and the possible benefits of nighttime water use or E by the tree.

  8. Suppression of nighttime sap flux with lower stem photosynthesis in Eucalyptus trees.

    PubMed

    Gao, Jianguo; Zhou, Juan; Sun, Zhenwei; Niu, Junfeng; Zhou, Cuiming; Gu, Daxing; Huang, Yuqing; Zhao, Ping

    2016-04-01

    It is widely accepted that substantial nighttime sap flux (J s,n) or transpiration (E) occurs in most plants, but the physiological implications are poorly known. It has been hypothesized that J s,n or E serves to enhance nitrogen uptake or deliver oxygen; however, no clear evidence is currently available. In this study, sap flux (J s) in Eucalyptus grandis × urophylla with apparent stem photosynthesis was measured, including control trees which were covered by aluminum foil (approximately 1/3 of tree height) to block stem photosynthesis. We hypothesized that the nighttime water flux would be suppressed in trees with lower stem photosynthesis. The results showed that the green tissue degraded after 3 months, demonstrating a decrease in stem photosynthesis. The daytime J s decreased by 21.47%, while J s,n decreased by 12.03% in covered trees as compared to that of control, and the difference was statistically significant (P < 0.01). The linear quantile regression model showed that J s,n decreased for a given daytime transpiration water loss, indicating that J s,n was suppressed by lower stem photosynthesis in covered trees. Predawn (ψ pd) of covered trees was marginally higher than that of control while lower at predawn stomatal conductance (g s), indicating a suppressed water flux in covered trees. There was no difference in leaf carbon content and δ(13)C between the two groups, while leaf nitrogen content and δ(15)N were significantly higher in covered trees than that of the control (P < 0.05), indicating that J s,n was not used for nitrogen uptake. These results suggest that J s,n may act as an oxygen pathway since green tissue has a higher respiration or oxygen demand than non-green tissue. Thus, this study demonstrated the physiological implications of J s,n and the possible benefits of nighttime water use or E by the tree.

  9. Nighttime Temperatures on Ganymede

    NASA Technical Reports Server (NTRS)

    1997-01-01

    This infrared image of Jupiter's moon Ganymede, showing heat radiation from its surface at a wavelength of about 60 microns (millionths of a meter), provides the best view yet of nighttime temperatures on this hemisphere of Ganymede. Temperatures, derived from the brightness of the infrared radiation, can be determined from the colors by reference to the scale at the bottom of the image.

    The image, taken by NASA's Galileo spacecraft, shows most of Ganymede's nighttime hemisphere, centered on longitude 180 degrees, with north at the top. Irregular, diagonal dark stripes result from missing data, and are not real. Part of Ganymede's illuminated crescent, warmed by the late afternoon sun and appearing pink in this representation (indicating temperatures near 110 Kelvin (-260 F), is visible in the lower left, but most of the part of Ganymede that is seen here is in darkness, glowing only because it retains some heat from the previous day. Jupiter appears in the background behind Ganymede in the upper right part of the image. Although it is nighttime on this part of Jupiter, the planet remains much warmer at night than Ganymede does, with temperatures near 140 Kelvin (- 207 F), because Jupiter's atmosphere is too dense to cool down significantly during the night, and is also warmed by heat that flows up from Jupiter's interior. The coldest parts of Ganymede that are visible (appearing dark blue) are near the north and south poles, and have temperatures below 80 Kelvin (-315 F), while parts of the equator remain at temperatures up to 100 K (-279 F) through the night, and appear in bright blue and purple colors. This same side of Ganymede was seen in full sunlight on Galileo's first orbit around Jupiter, and similar measurements showed that noontime temperatures at the equator reached 150 K (-190 F), which is 90 degrees (Fahrenheit) warmer than the night-time temperatures seen here.

    The image was taken with Galileo's PPR (Photopolarimeter-Radiometer) instrument on

  10. Low carbon dioxide concentrations can reverse stomatal closure during water stress

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Leaf water potentials below threshold values result in reduced stomatal conductance. Stomatal closure at low leaf water potentials may serve to protect against cavitation of xylem. Possible control of stomatal conductance by leaf water potential or hydraulic conductance was tested by drying the root...

  11. Recurrent aphthous stomatitis

    PubMed Central

    Preeti, L; Magesh, KT; Rajkumar, K; Karthik, Raghavendhar

    2011-01-01

    Recurrent aphthous ulcers are common painful mucosal conditions affecting the oral cavity. Despite their high prevalence, etiopathogenesis remains unclear. This review article summarizes the clinical presentation, diagnostic criteria, and recent trends in the management of recurrent apthous stomatitis. PMID:22144824

  12. Phylogenetic and ecological patterns in nighttime transpiration among five members of the genus Rubus co-occurring in western Oregon.

    PubMed

    McNellis, Brandon; Howard, Ava R

    2015-09-01

    Nighttime transpiration is a substantial portion of ecosystem water budgets, but few studies compare water use of closely related co-occurring species in a phylogenetic context. Nighttime transpiration can range up to 69% of daytime rates and vary between species, ecosystem, and functional type. We examined leaf-level daytime and nighttime gas exchange of five species of the genus Rubus co-occurring in the Pacific Northwest of western North America in a greenhouse common garden. Contrary to expectations, nighttime transpiration was not correlated to daytime water use. Nighttime transpiration showed pronounced phylogenetic signals, but the proportion of variation explained by different phylogenetic groupings varied across datasets. Leaf osmotic water potential, water potential at turgor loss point, stomatal size, and specific leaf area were correlated with phylogeny but did not readily explain variation in nighttime transpiration. Patterns in interspecific variation as well as a disconnect between rates of daytime and nighttime transpiration suggest that variation in nighttime water use may be at least partly driven by genetic factors independent of those that control daytime water use. Future work with co-occurring congeneric systems is needed to establish the generality of these results and may help determine the mechanism driving interspecific variation in nighttime water use.

  13. Phylogenetic and ecological patterns in nighttime transpiration among five members of the genus Rubus co-occurring in western Oregon

    PubMed Central

    McNellis, Brandon; Howard, Ava R

    2015-01-01

    Nighttime transpiration is a substantial portion of ecosystem water budgets, but few studies compare water use of closely related co-occurring species in a phylogenetic context. Nighttime transpiration can range up to 69% of daytime rates and vary between species, ecosystem, and functional type. We examined leaf-level daytime and nighttime gas exchange of five species of the genus Rubus co-occurring in the Pacific Northwest of western North America in a greenhouse common garden. Contrary to expectations, nighttime transpiration was not correlated to daytime water use. Nighttime transpiration showed pronounced phylogenetic signals, but the proportion of variation explained by different phylogenetic groupings varied across datasets. Leaf osmotic water potential, water potential at turgor loss point, stomatal size, and specific leaf area were correlated with phylogeny but did not readily explain variation in nighttime transpiration. Patterns in interspecific variation as well as a disconnect between rates of daytime and nighttime transpiration suggest that variation in nighttime water use may be at least partly driven by genetic factors independent of those that control daytime water use. Future work with co-occurring congeneric systems is needed to establish the generality of these results and may help determine the mechanism driving interspecific variation in nighttime water use. PMID:26380686

  14. Optimal stomatal behaviour under stochastic rainfall.

    PubMed

    Lu, Yaojie; Duursma, Remko A; Medlyn, Belinda E

    2016-04-01

    Vegetation CO2 uptake is always accompanied by water loss. The balance in this gas exchange is controlled by the stomata, through which CO2 and water vapour diffuse between the leaf and the atmosphere. The optimal stomatal behaviour theory proposes that vegetation should optimise its stomatal behaviour such that, for given water availability, photosynthesis is maximised. In this paper, we optimise stomatal conductance as a function of soil water content for the maximum expected value of photosynthesis rate. This optimisation process is considered under stochastic rainfall. The optimal solution is largely shaped by two constraints: the risks of soil water exhaustion and surface runoff, which results in an inverse S-shaped curve of stomatal conductance along the soil water gradient. We derive the optimal functional relationship between stomatal conductance and soil water content under varying rainfall frequency, mean annual precipitation and atmospheric CO2 concentration. Comparisons with large-scale observational data show that the model is able to broadly capture responses of photosynthesis, transpiration, and water use efficiency along rainfall gradients, although notable discrepancies suggest additional factors are important in shaping these responses. Our work provides a theoretical framework for analysing the vegetation gas exchange under environmental change. PMID:26796317

  15. Steady-state chlorophyll fluorescence (Fs) measurements as a tool to follow variations of net CO2 assimilation and stomatal conductance during water-stress in C3 plants.

    PubMed

    Flexas, Jaume; Escalona, José Mariano; Evain, Sebastian; Gulías, Javier; Moya, Ismaël; Osmond, Charles Barry; Medrano, Hipólito

    2002-02-01

    Water stress experiments were performed with grapevines (Vitis vinifera L.) and other C3 plants in the field, in potted plants in the laboratory, and with detached leaves. It was found that, in all cases, the ratio of steady state chlorophyll fluorescence (Fs) normalized to dark-adapted intrinsic fluorescence (Fo) inversely correlated with non-photochemical quenching (NPQ). Also, at high irradiance, the ratio Fs/Fo was positively correlated with CO2 assimilation in air, with electron transport rate calculated from fluorescence, and with stomatal conductance, but no clear correlation was observed with qP. The significance of these relationships is discussed. The ratio Fs/Fo, measured with a portable instrument (PAM-2000) or with a remote sensing FIPAM system, provides a good method for the early detection of water stress, and may become a useful guide to irrigation requirements.

  16. Drought induces alterations in the stomatal development program in Populus.

    PubMed

    Hamanishi, Erin T; Thomas, Barb R; Campbell, Malcolm M

    2012-08-01

    Much is known about the physiological control of stomatal aperture as a means by which plants adjust to water availability. By contrast, the role played by the modulation of stomatal development to limit water loss has received much less attention. The control of stomatal development in response to water deprivation in the genus Populus is explored here. Drought induced declines in stomatal conductance as well as an alteration in stomatal development in two genotypes of Populus balsamifera. Leaves that developed under water-deficit conditions had lower stomatal indices than leaves that developed under well-watered conditions. Transcript abundance of genes that could hypothetically underpin drought-responsive changes in stomatal development was examined, in two genotypes, across six time points, under two conditions, well-watered and with water deficit. Populus homologues of STOMAGEN, ERECTA (ER), STOMATA DENSITY AND DISTRIBUTION 1 (SDD1), and FAMA had variable transcript abundance patterns congruent with their role in the modulation of stomatal development in response to drought. Conversely, there was no significant variation in transcript abundance between genotypes or treatments for the Populus homologues of YODA (YDA) and TOO MANY MOUTHS (TMM). The findings highlight the role that could be played by stomatal development during leaf expansion as a longer term means by which to limit water loss from leaves. Moreover, the results point to the key roles played by the regulation of the homologues of STOMAGEN, ER, SDD1, and FAMA in the control of this response in poplar.

  17. Determinants of water circulation in a woody bamboo species: afternoon use and night-time recharge of culm water storage.

    PubMed

    Yang, Shi-Jian; Zhang, Yong-Jiang; Goldstein, Guillermo; Sun, Mei; Ma, Ren-Yi; Cao, Kun-Fang

    2015-09-01

    To understand water-use strategies of woody bamboo species, sap flux density (Fd) in the culms of a woody bamboo (Bambusa vulgaris Schrader ex Wendland) was monitored using the thermal dissipation method. The daytime and night-time Fd were analyzed in the dry and rainy seasons. Additionally, diurnal changes in root pressure, culm circumference, and stomatal conductance (gs) were investigated to characterize the mechanisms used to maintain diurnal water balance of woody bamboos. Both in the dry and rainy seasons, daytime Fd responded to vapor pressure deficit (VPD) in an exponential fashion, with a fast initial increase in Fd when VPD increased from 0 to 1 kPa. The Fd and gs started to increase very fast as light intensity and VPD increased in the morning, but they decreased sharply once the maximum value was achieved. The Fd response of this woody bamboo to VPD was much faster than that of representative trees and palms growing in the same study site, suggesting its fast sap flow and stomatal responses to changes in ambient environmental factors. The Fd in the lower and higher culm positions started to increase at the same time in the morning, but the Fd in the higher culm position was higher than that of the lower culm in the afternoon. Consistently, distinct decreases in its culm circumference in the afternoon were detected. Therefore, unlike trees, water storage of bamboo culms was not used for its transpiration in the morning but in the afternoon. Nocturnal sap flow of this woody bamboo was also detected and related to root pressure. We conclude that this bamboo has fast sap flow/stomatal responses to irradiance and evaporative demands, and it uses substantial water storage for transpiration in the afternoon, while root pressure appears to be a mechanism resulting in culm water storage recharge during the night. PMID:26232783

  18. Urban legends: recurrent aphthous stomatitis.

    PubMed

    Baccaglini, L; Lalla, R V; Bruce, A J; Sartori-Valinotti, J C; Latortue, M C; Carrozzo, M; Rogers, R S

    2011-11-01

    Recurrent aphthous stomatitis (RAS) is the most common idiopathic intraoral ulcerative disease in the USA. Aphthae typically occur in apparently healthy individuals, although an association with certain systemic diseases has been reported. Despite the unclear etiopathogenesis, new drug trials are continuously conducted in an attempt to reduce pain and dysfunction. We investigated four controversial topics: (1) Is complex aphthosis a mild form of Behçet's disease (BD)? (2) Is periodic fever, aphthous stomatitis, pharyngitis, and adenitis (PFAPA) syndrome a distinct medical entity? (3) Is RAS associated with other systemic diseases [e.g., celiac disease (CD) and B12 deficiency]? (4) Are there any new RAS treatments? Results from extensive literature searches, including a systematic review of RAS trials, suggested the following: (1) Complex aphthosis is not a mild form of BD in North America or Western Europe; (2) Diagnostic criteria for PFAPA have low specificity and the characteristics of the oral ulcers warrant further studies; (3) Oral ulcers may be associated with CD; however, these ulcers may not be RAS; RAS is rarely associated with B12 deficiency; nevertheless, B12 treatment may be beneficial, via mechanisms that warrant further study; (4) Thirty-three controlled trials published in the past 6 years reported some effectiveness, although potential for bias was high.

  19. Effects of atmospheric VPD, plant canopies, and low-water years on leaf stomatal conductance and photosynthetic water use efficiency in fifteen potential crop species for use in arid environments

    NASA Astrophysics Data System (ADS)

    Lue, A.; Jasoni, R. L.; Arnone, J.

    2011-12-01

    When evaluating the potential for growing alternative crop species in arid environments, high vapor pressure deficits (VPDs) that could potentially inhibit crop productivity by limiting stomatal conductance and CO2 uptake must be considered. The objective of this study was to quantify the effects of VPD and irrigation levels on leaf stomatal conductance (gs) and photosynthetic water use efficiency (PWUE) for a range of alternative crop species for aridland agriculture. We evaluated fifteen alternative crops in a field trial in the northern Nevada Walker River Basin. Plots of each species were subjected to two irrigation treatments, 4 and 2 acre-feet per growing season, to simulate normal-year and dry-year irrigation levels. We quantified gs and photosynthesis (A) under decreasing relative humidity (RH) (increasing VPDs) in 10% increments, from about 75% to 2%. About seventeen leaves per species were measured throughout the 2010 growing season over eleven days of samplings. Canopy air temperature and RH were logged in experimental plots to calculate diel and seasonal patterns in canopy VPD. Volumetric water content was also collected to quantify the effects of irrigation treatments on soil moisture and leaf gas exchange. Species varied in their gs and PWUE responses to increasing VPD. Stomatal conductance (gs) of leaves of all species generally increased initially as RH was lowered but then decreased at differing rates as RH dropped further. Average gs (across all measurement VPDs), maximum gs, maximum PWUE, and corresponding VPDs differed among species and between irrigation treatments. Some species (Medicago sativa, Leymus racemosus) showed higher gs across the range of measurement VPDs than other species (Bothrichloa ischaemum, Sorghastrum nutans), while some species exhibited maximum gs and maximum PWUE at higher VPDs (Erograstis tef, Calamovilfa longifolia) than other species (Leymus cinereus, Sorghastrum nutans). These results suggest that some species may

  20. Stomatal Development in Arabidopsis

    PubMed Central

    Pillitteri, Lynn Jo; Dong, Juan

    2013-01-01

    Stomata consist of two guard cells that function as turgor-operated valves that regulate gas exchange in plants. In Arabidopsis, a dedicated cell lineage is initiated and undergoes a series of cell divisions and cell-state transitions to produce a stoma. A set of basic helix-loop-helix (bHLH) transcription factors regulates the transition and differentiation events through the lineage, while the placement of stomata relative to each other is controlled by intercellular signaling via peptide ligands, transmembrane receptors, and mitogen-activated protein kinase (MAPK) modules. Some genes involved in regulating stomatal differentiation or density are also involved in hormonal and environmental stress responses, which may provide a link between modulation of stomatal development or function in response to changes in the environment. Premitotic polarlylocalized proteins provide an added layer of regulation, which can be addressed more thoroughly with the identification of additional proteins in this pathway. Linking the networks that control stomatal development promises to bring advances to our understanding of signal transduction, cell polarity, and cell-fate specification in plants. PMID:23864836

  1. Generalized hydromechanical model for stomatal responses to hydraulic perturbations.

    PubMed

    Kwon, H W; Choi, M Y

    2014-01-01

    Stomata respond in a common pattern to various hydraulic perturbations on any part of the 'soil-plant-air' system: initial transient 'wrong-way' responses and final stationary 'right-way' responses. In order to describe this pattern on the basis of statistical physics, we propose a simple model where turgor pressure of a cell is taken to be a power function of its volume, and obtain results in qualitative agreement with experimental data for responses to a variety of hydraulic perturbations: Firstly, stationary stomatal conductance as a function of the vapor pressure deficit divides into three regimes characterized by sensitivities of the stomatal conductance and the transpiration rate with respect to vapor pressure deficit; secondly, for every hydraulic perturbation, the initial transient 'wrong-way' responses always appear; thirdly, on condition that water is supplied insufficiently, stomatal oscillations are often observed; finally, stomatal responses following leaf excision exhibit, after the initial transient wrong-way responses, slow relaxation to stomatal closing. In particular, comparison of areoles having different numbers of stomata demonstrates that areoles with small numbers of stomata tend to provoke lack of water in the soil as well as in the plant. In addition, our model also describes well dependence of the stomatal conductance on temperature. It may be extended further to describe stomatal responses to other environmental factors such as carbon dioxide, light, and temperature.

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

    PubMed

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

    2016-04-01

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

  3. Zeaxanthin concentrations co-segregate with the magnitude of the blue light response of adaxial guard cells and leaf stomatal conductances in an F2 population of pima cotton

    SciTech Connect

    Quinones, M.A.; Lu Zhenmin; Zeiger, E. )

    1993-05-01

    A blue light (BL) response of adaxial (AD) guard cells was investigated in two cotton lines with contrasting rates of stomatal conductances (g). This response is expressed as an enhancement of the red light-induced chlorophyll a fluorescence quenching by BL, and has an action spectrum indicative of a carotenoid photoreceptor. Ad guard cell from the high g, advanced line Pima S-6 have a higher carotenoid content and a larger BL response than those from the low g, primitive cotton, B368. In a growth chamber-grown F2 population of a cross between the two lines (n=30), g of individual plants segregated over a range exceeding the average g of the parental populations. Carotenoid content and the BL response of ad guard cell also segregated. There was a positive, strong correlation (r=0.71) between leaf g and the magnitude of the BL response of ad guard cells, indicating that both parameters are under genetic control, and that the BL response of guard cells contributes to the modulation of g. The concentration of all xanthopylls and [beta]-carotene in the ad guard cells correlated poorly with the BL response, except for zeaxanthin (r=0.71). In all green systems, xanthophylls are located inside the chloroplast which suggests that zeaxanthin functions in these organelle as a blue light photoreceptor for cotton guard cells.

  4. Optimal stomatal behaviour around the world

    DOE PAGES

    Lin, Yan-Shih; Medlyn, Belinda E.; Duursma, Remko A.; Prentice, I. Colin; Wang, Han; Baig, Sofia; Eamus, Derek; de Dios, Victor Resco; Mitchell, Patrick; Ellsworth, David S.; et al

    2015-03-02

    Stomatal conductance (gs) is a key land-surface attribute as it links transpiration, the dominant component of global land evapotranspiration, and photosynthesis, the driving force of the global carbon cycle. Despite the pivotal role of gs in predictions of global water and carbon cycle changes, a global-scale database and an associated globally applicable model of gs that allow predictions of stomatal behaviour are lacking. Here, we present a database of globally distributed gs obtained in the field for a wide range of plant functional types (PFTs) and biomes. We find that stomatal behaviour differs among PFTs according to their marginal carbonmore » cost of water use, as predicted by the theory underpinning the optimal stomatal model1 and the leaf and wood economics spectrum2,3. We also demonstrate a global relationship with climate. In conclusion, these findings provide a robust theoretical framework for understanding and predicting the behaviour of gs across biomes and across PFTs that can be applied to regional, continental and global-scale modelling of ecosystem productivity, energy balance and ecohydrological processes in a future changing climate.« less

  5. Optimal stomatal behaviour around the world

    SciTech Connect

    Lin, Yan-Shih; Medlyn, Belinda E.; Duursma, Remko A.; Prentice, I. Colin; Wang, Han; Baig, Sofia; Eamus, Derek; de Dios, Victor Resco; Mitchell, Patrick; Ellsworth, David S.; de Beeck, Maarten Op; Wallin, Göran; Uddling, Johan; Tarvainen, Lasse; Linderson, Maj-Lena; Cernusak, Lucas A.; Nippert, Jesse B.; Ocheltree, Troy W.; Tissue, David T.; Martin-StPaul, Nicolas K.; Rogers, Alistair; Warren, Jeff M.; De Angelis, Paolo; Hikosaka, Kouki; Han, Qingmin; Onoda, Yusuke; Gimeno, Teresa E.; Barton, Craig V. M.; Bennie, Jonathan; Bonal, Damien; Bosc, Alexandre; Löw, Markus; Macinins-Ng, Cate; Rey, Ana; Rowland, Lucy; Setterfield, Samantha A.; Tausz-Posch, Sabine; Zaragoza-Castells, Joana; Broadmeadow, Mark S. J.; Drake, John E.; Freeman, Michael; Ghannoum, Oula; Hutley, Lindsay B.; Kelly, Jeff W.; Kikuzawa, Kihachiro; Kolari, Pasi; Koyama, Kohei; Limousin, Jean-Marc; Meir, Patrick; Lola da Costa, Antonio C.; Mikkelsen, Teis N.; Salinas, Norma; Sun, Wei; Wingate, Lisa

    2015-03-02

    Stomatal conductance (gs) is a key land-surface attribute as it links transpiration, the dominant component of global land evapotranspiration, and photosynthesis, the driving force of the global carbon cycle. Despite the pivotal role of gs in predictions of global water and carbon cycle changes, a global-scale database and an associated globally applicable model of gs that allow predictions of stomatal behaviour are lacking. Here, we present a database of globally distributed gs obtained in the field for a wide range of plant functional types (PFTs) and biomes. We find that stomatal behaviour differs among PFTs according to their marginal carbon cost of water use, as predicted by the theory underpinning the optimal stomatal model1 and the leaf and wood economics spectrum2,3. We also demonstrate a global relationship with climate. In conclusion, these findings provide a robust theoretical framework for understanding and predicting the behaviour of gs across biomes and across PFTs that can be applied to regional, continental and global-scale modelling of ecosystem productivity, energy balance and ecohydrological processes in a future changing climate.

  6. Effects of exogenous 5-aminolevulinic acid on photosynthesis, stomatal conductance, transpiration rate, and PIP gene expression of tomato seedlings subject to salinity stress.

    PubMed

    Zhao, Y Y; Yan, F; Hu, L P; Zhou, X T; Zou, Z R; Cui, L R

    2015-01-01

    The effects of exogenous 5-aminolevulinic acid (ALA) on photosynthesis, plant growth, and the expression of two aquaporin genes in tomato seedlings under control and salinity conditions were investigated. Exogenous ALA application significantly improved net photosynthetic rate (Pn), total chlorophyll content, and plant biomass accumulation of tomato seedlings under salinity stress. As revealed by real-time PCR analyses, after treatment with ALA alone, expression of both LePIP1 and LePIP2 in the two tomato cultivars was up-regulated at 2 h and subsequently decreased to normal levels. Under salinity stress, transcript levels of LePIP1 in both leaves and roots of salt-sensitive cultivars (cv. Zhongza No.9) increased significantly and were considerably higher than in cultivars exposed to ALA alone. In contrast, the expression levels of LePIP1 and LePIP2 in cvs. Jinpeng No.1 cultivars were slightly lower under salinity stress than under ALA treatment. In addition, transcript levels of both LePIP1 and LePIP2 in the roots of Jinpeng No. 1 cultivars were considerably lower than those in the roots of Zhongza No. 9 cultivars under salinity stress, regardless of ALA supplementation, implying that Jinpeng No. 1 cultivars had a better capacity to maintain membrane intrinsic protein stability. Further, ALA application distinctly counteracted the up- or down-regulation of LePIP1 and LePIP2 in both cultivars under salinity stress, in accordance with the improvements instomatal conductance, transpiration rate, and Pn of tomato leaves. The results presented here indicate that ALA controls aquaporin expression, thus, presumably ALA regulates water homeostasis and enhances salt tolerance of tomato seedlings. PMID:26125845

  7. Effects of exogenous 5-aminolevulinic acid on photosynthesis, stomatal conductance, transpiration rate, and PIP gene expression of tomato seedlings subject to salinity stress.

    PubMed

    Zhao, Y Y; Yan, F; Hu, L P; Zhou, X T; Zou, Z R; Cui, L R

    2015-06-11

    The effects of exogenous 5-aminolevulinic acid (ALA) on photosynthesis, plant growth, and the expression of two aquaporin genes in tomato seedlings under control and salinity conditions were investigated. Exogenous ALA application significantly improved net photosynthetic rate (Pn), total chlorophyll content, and plant biomass accumulation of tomato seedlings under salinity stress. As revealed by real-time PCR analyses, after treatment with ALA alone, expression of both LePIP1 and LePIP2 in the two tomato cultivars was up-regulated at 2 h and subsequently decreased to normal levels. Under salinity stress, transcript levels of LePIP1 in both leaves and roots of salt-sensitive cultivars (cv. Zhongza No.9) increased significantly and were considerably higher than in cultivars exposed to ALA alone. In contrast, the expression levels of LePIP1 and LePIP2 in cvs. Jinpeng No.1 cultivars were slightly lower under salinity stress than under ALA treatment. In addition, transcript levels of both LePIP1 and LePIP2 in the roots of Jinpeng No. 1 cultivars were considerably lower than those in the roots of Zhongza No. 9 cultivars under salinity stress, regardless of ALA supplementation, implying that Jinpeng No. 1 cultivars had a better capacity to maintain membrane intrinsic protein stability. Further, ALA application distinctly counteracted the up- or down-regulation of LePIP1 and LePIP2 in both cultivars under salinity stress, in accordance with the improvements instomatal conductance, transpiration rate, and Pn of tomato leaves. The results presented here indicate that ALA controls aquaporin expression, thus, presumably ALA regulates water homeostasis and enhances salt tolerance of tomato seedlings.

  8. Dry season foliar fog uptake, reverse sapflow, and nighttime transpiration in the tropical montane cloud forests of Mexico

    NASA Astrophysics Data System (ADS)

    Gotsch, S. G.; Asbjornsen, H.; Holwerda, F.; Goldsmith, G. R.; Dawson, T. E.

    2010-12-01

    Dry season fog is a ubiquitous feature of seasonal tropical cloud forests. Although cloud forests receive generous inputs of yearly precipitation, rainfall occurs primarily in the wet season. In the tropical montane forests of Veracruz Mexico, 80% of rainfall occurs in the wet season while fog occurs primarily in the dry season. Since dry-season fog occurs during months when precipitation is low or absent, this meteorological phenomenon may be important in alleviating dry-season water stress either directly through foliar fog uptake, or indirectly through a reduction in transpiration causing relaxation in xylem water tension. We determined the importance of fog on the water relations of a dominant tropical montane forest tree in La Cortadura Reserve in Veracruz, Mexico by using micrometeorological data and by measuring sap flow, leaf water potential and stomatal conductance throughout the canopies of three mature oak trees. Although the relative humidity is generally high in this habitat, in the dry season, humidity is lower and at times can be as low as 20% which causes high vapor pressure deficit and evaporative demand. We also screened sap flow data to detect periods of nighttime transpiration. Reverse sap flow occurred frequently in this site during periods of fog/drizzle. Foliar fog uptake occurred 30% of the time in the dry season although this reverse flow is likely insignificant in the water balance of cloud forest trees. Furthermore we detected low, but positive, flow rates flow at night. Finally, we conducted diurnal courses of leaf water potential and stomatal conductance at the end of the dry season to determine whether these trees were undergoing water stress. Results/Conclusions We found that reverse sap flow is a common phenomena in the dry season, indicating foliar fog uptake. Although the addition of fog to whole-tree water balance may be minimal, high dry season leaf water potential may indicate the importance of fog in reducing the negative

  9. Recurrent Aphthous Stomatitis

    PubMed Central

    Akintoye, Sunday O.; Greenberg, Martin S.

    2014-01-01

    Recurrent Aphthous Stomatitis (RAS) is the most common ulcerative disease affecting the oral mucosa. It occurs mostly in healthy individuals and has atypical clinical presentation in immunocompromised individuals. The etiology of RAS is still unknown, but several local, systemic, immunologic, genetic, allergic, nutritional, and microbial factors, as well as immunosuppressive drugs, have been proposed as causative agents. Clinical management of RAS is based on severity of symptoms, frequency, size and number of lesions using topical and systemic therapies. The goals of therapy are to decrease pain and ulcer size, promote healing and decrease frequency of recurrence. PMID:24655523

  10. The energy balance of the nighttime thermosphere

    NASA Technical Reports Server (NTRS)

    Glenar, D. A.

    1977-01-01

    The discrepancy between the input from the day hemisphere and the observed loss rates is discussed in terms of ion-neutral processes and gravity wave inputs. There has been considerable speculation as to the energy balance of the thermosphere and in particular about the fraction of the total energy input supplied by ultraviolet radiation. The problem is considerably simplified by considering the energy balance of the nighttime hemisphere alone. Sunrise and sunset vapor trail measurements provide data on the wind systems at the terminator boundary, and temperature measurements provide information on the vertical energy conduction. North-south winds from high latitude vapor trail measurements provide a measure of the energy input from auroral processes.

  11. Stomatal characteristics of riparian poplar species in a semi-arid environment.

    PubMed

    Pearce, David W; Millard, Sandra; Bray, Douglas F; Rood, Stewart B

    2006-02-01

    Several native poplar species meet at the margins of their natural distributions in southern Alberta, Canada. In this semi-arid area, poplars are obligate riparian species but they occupy several intergrading ecoregions. Populus deltoides Bartr. ex Marsh predominates in the warmest and driest eastern prairie ecoregions; P. balsamifera L. occupies the cooler and wetter western parkland and montane ecoregions; and P. angustifolia James and hybrids between the species occur in the intermediate grassland ecoregions. We investigated stomatal characteristics of these poplars in 51 genotypes collected across the range of ecoregions and grown in a semi-arid common garden. Stomatal length differed among genotypes within species but did not differ among species, ranging from 19 to 22 microm. Total stomatal densities (adaxial plus abaxial) differed among genotypes within species but were similar among species (290-420 stomata mm(-2)). Single-surface stomatal densities differed among species and consequently, the ratio of adaxial:abaxial stomatal density also differed, ranging from 0.94 for P. deltoides to 0.27 for P. balsamifera, with intermediate stomatal density ratios in P. angustifolia and hybrids. In a subsequent study of a subset of the same genotypes, stomatal density was correlated with stomatal conductance (r2 = 0.75) and the conductance ratios differed among species in the same manner as the stomatal density ratios. We conclude that: (1) diverse poplar genotypes respond similarly to a semi-arid environment by producing comparatively small and dense stomata; (2) differences in stomatal density underlie differences in stomatal conductance and differences among species in stomatal density ratio or conductance ratio may reflect adaptation to climatic differences among ecoregions; and (3) there is substantial variation in stomatal characteristics within and among species and hybrids in this area that could be useful for the selection and breeding of poplars adapted to

  12. Ozone-induced stomatal sluggishness changes carbon and water balance of temperate deciduous forests.

    PubMed

    Hoshika, Yasutomo; Katata, Genki; Deushi, Makoto; Watanabe, Makoto; Koike, Takayoshi; Paoletti, Elena

    2015-01-01

    Tropospheric ozone concentrations have increased by 60-100% in the Northern Hemisphere since the 19(th) century. The phytotoxic nature of ozone can impair forest productivity. In addition, ozone affects stomatal functions, by both favoring stomatal closure and impairing stomatal control. Ozone-induced stomatal sluggishness, i.e., a delay in stomatal responses to fluctuating stimuli, has the potential to change the carbon and water balance of forests. This effect has to be included in models for ozone risk assessment. Here we examine the effects of ozone-induced stomatal sluggishness on carbon assimilation and transpiration of temperate deciduous forests in the Northern Hemisphere in 2006-2009 by combining a detailed multi-layer land surface model and a global atmospheric chemistry model. An analysis of results by ozone FACE (Free-Air Controlled Exposure) experiments suggested that ozone-induced stomatal sluggishness can be incorporated into modelling based on a simple parameter (gmin, minimum stomatal conductance) which is used in the coupled photosynthesis-stomatal model. Our simulation showed that ozone can decrease water use efficiency, i.e., the ratio of net CO2 assimilation to transpiration, of temperate deciduous forests up to 20% when ozone-induced stomatal sluggishness is considered, and up to only 5% when the stomatal sluggishness is neglected. PMID:25943276

  13. Ozone-induced stomatal sluggishness changes carbon and water balance of temperate deciduous forests

    NASA Astrophysics Data System (ADS)

    Hoshika, Yasutomo; Katata, Genki; Deushi, Makoto; Watanabe, Makoto; Koike, Takayoshi; Paoletti, Elena

    2015-05-01

    Tropospheric ozone concentrations have increased by 60-100% in the Northern Hemisphere since the 19th century. The phytotoxic nature of ozone can impair forest productivity. In addition, ozone affects stomatal functions, by both favoring stomatal closure and impairing stomatal control. Ozone-induced stomatal sluggishness, i.e., a delay in stomatal responses to fluctuating stimuli, has the potential to change the carbon and water balance of forests. This effect has to be included in models for ozone risk assessment. Here we examine the effects of ozone-induced stomatal sluggishness on carbon assimilation and transpiration of temperate deciduous forests in the Northern Hemisphere in 2006-2009 by combining a detailed multi-layer land surface model and a global atmospheric chemistry model. An analysis of results by ozone FACE (Free-Air Controlled Exposure) experiments suggested that ozone-induced stomatal sluggishness can be incorporated into modelling based on a simple parameter (gmin, minimum stomatal conductance) which is used in the coupled photosynthesis-stomatal model. Our simulation showed that ozone can decrease water use efficiency, i.e., the ratio of net CO2 assimilation to transpiration, of temperate deciduous forests up to 20% when ozone-induced stomatal sluggishness is considered, and up to only 5% when the stomatal sluggishness is neglected.

  14. Ozone-induced stomatal sluggishness changes carbon and water balance of temperate deciduous forests.

    PubMed

    Hoshika, Yasutomo; Katata, Genki; Deushi, Makoto; Watanabe, Makoto; Koike, Takayoshi; Paoletti, Elena

    2015-05-06

    Tropospheric ozone concentrations have increased by 60-100% in the Northern Hemisphere since the 19(th) century. The phytotoxic nature of ozone can impair forest productivity. In addition, ozone affects stomatal functions, by both favoring stomatal closure and impairing stomatal control. Ozone-induced stomatal sluggishness, i.e., a delay in stomatal responses to fluctuating stimuli, has the potential to change the carbon and water balance of forests. This effect has to be included in models for ozone risk assessment. Here we examine the effects of ozone-induced stomatal sluggishness on carbon assimilation and transpiration of temperate deciduous forests in the Northern Hemisphere in 2006-2009 by combining a detailed multi-layer land surface model and a global atmospheric chemistry model. An analysis of results by ozone FACE (Free-Air Controlled Exposure) experiments suggested that ozone-induced stomatal sluggishness can be incorporated into modelling based on a simple parameter (gmin, minimum stomatal conductance) which is used in the coupled photosynthesis-stomatal model. Our simulation showed that ozone can decrease water use efficiency, i.e., the ratio of net CO2 assimilation to transpiration, of temperate deciduous forests up to 20% when ozone-induced stomatal sluggishness is considered, and up to only 5% when the stomatal sluggishness is neglected.

  15. Observations on the Stomatal Control of NO2 Exchange.

    NASA Astrophysics Data System (ADS)

    Kesselmeier, J.; Chaparro-Suarez, I. G.; Meixner, F. X.

    2005-12-01

    Nitrogen oxides play a central role in tropospheric chemistry especially in the formation of tropospheric ozone, acid rain and hydroxyl radical as well as in CH4 and CO oxidation processes. NO2 can be assimilated and emitted by the plant leaves as well. We investigated the impact of the stomatal regulation with four tree species (Betula pendula, Fagus sylvatica, Quercus ilex und Pinus sylvestris) by exposure of leaves to the hormone abscisic acid inducing stomatal closure. The results showed that the NO2 uptake was strongly dependent on stomatal aperture. The uptake correlated linearly with stomatal (leaf) conductance in case of all four tree species investigated. In contrast an NO2 emission was observed with beech in the dark when stomata were basically closed.

  16. A new stomatal paradigm for earth system models? (Invited)

    NASA Astrophysics Data System (ADS)

    Bonan, G. B.; Williams, M. D.; Fisher, R. A.; Oleson, K. W.; Lombardozzi, D.

    2013-12-01

    The land component of climate, and now earth system, models has simulated stomatal conductance since the introduction in the mid-1980s of the so-called second generation models that explicitly represented plant canopies. These second generation models used the Jarvis-style stomatal conductance model, which empirically relates stomatal conductance to photosynthetically active radiation, temperature, vapor pressure deficit, CO2 concentration, and other factors. Subsequent models of stomatal conductance were developed from a more mechanistic understanding of stomatal physiology, particularly that stomata are regulated so as to maximize net CO2 assimilation (An) and minimize water loss during transpiration (E). This concept is embodied in the Ball-Berry stomatal conductance model, which relates stomatal conductance (gs) to net assimilation (An), scaled by the ratio of leaf surface relative humidity to leaf surface CO2 concentration, or the Leuning variant which replaces relative humidity with a vapor pressure deficit term. This coupled gs-An model has been widely used in climate and earth system models since the mid-1990s. An alternative approach models stomatal conductance by directly optimizing water use efficiency, defined as the ratio An/gs or An/E. Conceptual developments over the past several years have shown that the Ball-Berry style model can be derived from optimization theory. However, an explicit optimization model has not been tested in an earth system model. We compare the Ball-Berry model with an explicit optimization model, both implemented in a new plant canopy parameterization developed for the Community Land Model, the land component of the Community Earth System Model. The optimization model is from the Soil-Plant-Atmosphere (SPA) model, which integrates plant and soil hydraulics, carbon assimilation, and gas diffusion. The canopy parameterization is multi-layer and resolves profiles of radiation, temperature, vapor pressure, leaf water stress

  17. [Stomatal response of spring wheat and related affecting factors under different irrigation treatment].

    PubMed

    Cheng, Xue-Feng; Zhang, Feng-Yun; Chai, Shou-Xi

    2010-01-01

    Taking three spring wheat cultivars as test materials, a field experiment was conducted to study the effects of different irrigation treatments on the stomatal conductance of the cultivars during their growth period, with the relationships between the stomatal conductance and the environmental factors analyzed. On the basis of winter irrigation with 1800 m3 x hm(-2) of water, three irrigation treatments, i. e., irrigating three times (T1), two times (T2), and once (T3) during spring wheat growth period, were installed, with 1050 m3 x hm(-2) of irrigation water each time. All irrigation treatments had greater effects on the stomatal conductance, which was decreased with the decreasing times of irrigation, and varied with the cultivars. From jointing stage to florescence, the stomatal conductance in all treatments had the same variation trend, i. e., decreased after an initial increase, and reached the peak at heading stage. After florescence, difference occurred among the treatments. In treatment T1, the stomatal conductance of all test cultivars increased after an initial decrease; in treatment T2, the variation patterns of stomatal conductance differed with cultivars; while in treatment T3, the conductance of all cultivars decreased all along. Among the environmental factors, relative atmospheric humidity had the greatest effects on the stomatal conductance, and their correlation coefficient in treatments T2 and T3 reached significant (0.82) and very significant (0.92* *), respectively. The stomatal regulation mechanism of spring wheat adapting to water deficit in Hexi corridor was of feedback manner.

  18. Protein phosphorylation in stomatal movement

    PubMed Central

    Zhang, Tong; Chen, Sixue; Harmon, Alice C

    2014-01-01

    As research progresses on how guard cells perceive and transduce environmental cues to regulate stomatal movement, plant biologists are discovering key roles of protein phosphorylation. Early research efforts focused on characterization of ion channels and transporters in guard cell hormonal signaling. Subsequent genetic studies identified mutants of kinases and phosphatases that are defective in regulating guard cell ion channel activities, and recently proteins regulated by phosphorylation have been identified. Here we review the essential role of protein phosphorylation in ABA-induced stomatal closure and in blue light-induced stomatal opening. We also highlight evidence for the cross-talk between different pathways, which is mediated by protein phosphorylation. PMID:25482764

  19. Modelling stomatal ozone flux across Europe.

    PubMed

    Emberson, L D; Ashmore, M R; Cambridge, H M; Simpson, D; Tuovinen, J P

    2000-09-01

    A model has been developed to estimate stomatal ozone flux across Europe for a number of important species. An initial application of this model is illustrated for two species, wheat and beech. The model calculates ozone flux using European Monitoring and Evaluation Programme (EMEP) model ozone concentrations in combination with estimates of the atmospheric, boundary layer and stomatal resistances to ozone transfer. The model simulates the effect of phenology, irradiance, temperature, vapour pressure deficit and soil moisture deficit on stomatal conductance. These species-specific microclimatic parameters are derived from meteorological data provided by the Norwegian Meteorological Institute (DNMI), together with detailed land-use and soil type maps assembled at the Stockholm Environment Institute (SEI). Modelled fluxes are presented as mean monthly flux maps and compared with maps describing equivalent values of AOT40 (accumulated exposure over threshold of 40 ppb or nl l(-1)), highlighting the spatial differences between these two indices. In many cases high ozone fluxes were modelled in association with only moderate AOT40 values. The factors most important in limiting ozone uptake under the model assumptions were vapour pressure deficit (VPD), soil moisture deficit (for Mediterranean regions in particular) and phenology. The limiting effect of VPD on ozone uptake was especially apparent, since high VPDs resulting in stomatal closure tended to co-occur with high ozone concentrations. Although further work is needed to link the ozone uptake and deposition model components, and to validate the model with field measurements, the present results give a clear indication of the possible implications of adopting a flux-based approach for future policy evaluation.

  20. Effects of experimental warming on stomatal traits in leaves of maize (Zea may L.)

    PubMed Central

    Zheng, Yunpu; Xu, Ming; Hou, Ruixing; Shen, Ruichang; Qiu, Shuai; Ouyang, Zhu

    2013-01-01

    We examined the warming effects on the stomatal frequency, stomatal aperture size and shape, and their spatial distribution pattern of maize (Zea may L.) leaves using a light microscope, an electron scanning microscope, and geostatistic techniques. A field manipulative experiment was conducted to elevate canopy temperature by 2.08°C, on average. We found that experimental warming had little effect on stomatal density, but significantly increased stomatal index due to the reduction in the number of epidermal cells under the warming treatment. Warming also significantly decreased stomatal aperture length and increased stomatal aperture width. As a result, warming significantly increased the average stomatal aperture area and stomatal aperture circumference. In addition, warming dramatically changed the stomatal spatial distribution pattern with a substantial increase in the average nearest neighbor distance between stomata on both adaxial and abaxial surfaces. The spatial distribution pattern of stomata was scale dependent with regular patterns at small scales and random patterns at larger scales on both leaf surfaces. Warming caused the stomatal distribution to become more regular on both leaf surfaces with smaller L(t) values (Ripley's K-function, L(t) is an expectation of zero for any value of t) in the warming plots than the control plots. PMID:24101997

  1. Stomatal closure is induced by hydraulic signals and maintained by ABA in drought-stressed grapevine

    PubMed Central

    Tombesi, Sergio; Nardini, Andrea; Frioni, Tommaso; Soccolini, Marta; Zadra, Claudia; Farinelli, Daniela; Poni, Stefano; Palliotti, Alberto

    2015-01-01

    Water saving under drought stress is assured by stomatal closure driven by active (ABA-mediated) and/or passive (hydraulic-mediated) mechanisms. There is currently no comprehensive model nor any general consensus about the actual contribution and relative importance of each of the above factors in modulating stomatal closure in planta. In the present study, we assessed the contribution of passive (hydraulic) vs active (ABA mediated) mechanisms of stomatal closure in V. vinifera plants facing drought stress. Leaf gas exchange decreased progressively to zero during drought, and embolism-induced loss of hydraulic conductance in petioles peaked to ~50% in correspondence with strong daily limitation of stomatal conductance. Foliar ABA significantly increased only after complete stomatal closure had already occurred. Rewatering plants after complete stomatal closure and after foliar ABA reached maximum values did not induced stomatal re-opening, despite embolism recovery and water potential rise. Our data suggest that in grapevine stomatal conductance is primarily regulated by passive hydraulic mechanisms. Foliar ABA apparently limits leaf gas exchange over long-term, also preventing recovery of stomatal aperture upon rewatering, suggesting the occurrence of a mechanism of long-term down-regulation of transpiration to favor embolism repair and preserve water under conditions of fluctuating water availability and repeated drought events. PMID:26207993

  2. Stomatal malfunctioning under low VPD conditions: induced by alterations in stomatal morphology and leaf anatomy or in the ABA signaling?

    PubMed

    Aliniaeifard, Sasan; Malcolm Matamoros, Priscila; van Meeteren, Uulke

    2014-12-01

    Exposing plants to low VPD reduces leaf capacity to maintain adequate water status thereafter. To find the impact of VPD on functioning of stomata, stomatal morphology and leaf anatomy, fava bean plants were grown at low (L, 0.23 kPa) or moderate (M, 1.17 kPa) VPDs and some plants that developed their leaves at moderate VPD were then transferred for 4 days to low VPD (M→L). Part of the M→L-plants were sprayed with ABA (abscisic acid) during exposure to L. L-plants showed bigger stomata, larger pore area, thinner leaves and less spongy cells compared with M-plants. Stomatal morphology (except aperture) and leaf anatomy of the M→L-plants were almost similar to the M-plants, while their transpiration rate and stomatal conductance were identical to that of L-plants. The stomatal response to ABA was lost in L-plants, but also after 1-day exposure of M-plants to low VPD. The level of foliar ABA sharply decreased within 1-day exposure to L, while the level of ABA-GE (ABA-glucose ester) was not affected. Spraying ABA during the exposure to L prevented loss of stomatal closing response thereafter. The effect of low VPD was largely depending on exposure time: the stomatal responsiveness to ABA was lost after 1-day exposure to low VPD, while the responsiveness to desiccation was gradually lost during 4-day exposure to low VPD. Leaf anatomical and stomatal morphological alterations due to low VPD were not the main cause of loss of stomatal closure response to closing stimuli.

  3. Stomatal malfunctioning under low VPD conditions: induced by alterations in stomatal morphology and leaf anatomy or in the ABA signaling?

    PubMed

    Aliniaeifard, Sasan; Malcolm Matamoros, Priscila; van Meeteren, Uulke

    2014-12-01

    Exposing plants to low VPD reduces leaf capacity to maintain adequate water status thereafter. To find the impact of VPD on functioning of stomata, stomatal morphology and leaf anatomy, fava bean plants were grown at low (L, 0.23 kPa) or moderate (M, 1.17 kPa) VPDs and some plants that developed their leaves at moderate VPD were then transferred for 4 days to low VPD (M→L). Part of the M→L-plants were sprayed with ABA (abscisic acid) during exposure to L. L-plants showed bigger stomata, larger pore area, thinner leaves and less spongy cells compared with M-plants. Stomatal morphology (except aperture) and leaf anatomy of the M→L-plants were almost similar to the M-plants, while their transpiration rate and stomatal conductance were identical to that of L-plants. The stomatal response to ABA was lost in L-plants, but also after 1-day exposure of M-plants to low VPD. The level of foliar ABA sharply decreased within 1-day exposure to L, while the level of ABA-GE (ABA-glucose ester) was not affected. Spraying ABA during the exposure to L prevented loss of stomatal closing response thereafter. The effect of low VPD was largely depending on exposure time: the stomatal responsiveness to ABA was lost after 1-day exposure to low VPD, while the responsiveness to desiccation was gradually lost during 4-day exposure to low VPD. Leaf anatomical and stomatal morphological alterations due to low VPD were not the main cause of loss of stomatal closure response to closing stimuli. PMID:24773210

  4. Ozone-induced stomatal sluggishness develops progressively in Siebold's beech (Fagus crenata).

    PubMed

    Hoshika, Yasutomo; Watanabe, Makoto; Inada, Naoki; Koike, Takayoshi

    2012-07-01

    We investigated the effects of ozone and leaf senescence on steady-state stomatal conductance and stomatal response to light variation. Measurements were carried out in a free-air ozone exposure experiment on a representative deciduous broadleaved tree species in Japan (Fagus crenata). Both steady-state and dynamic stomatal response to light variation varied intrinsically with season due to leaf senescence. Ozone induced the decrease in steady-state leaf gas exchange and the sluggish stomatal closure progressively. These findings suggest that ozone reduces the ability of plants to adapt to a fluctuating light environment under natural conditions, and therefore impairs plant growth and ability to control water loss.

  5. Tighten Teens' Nighttime Driving Restrictions: CDC

    MedlinePlus

    ... https://medlineplus.gov/news/fullstory_160130.html Tighten Teens' Nighttime Driving Restrictions: CDC Midnight cutoff is too ... THURSDAY, July 28, 2016 (HealthDay News) -- Getting U.S. teens out of the driver's seat before midnight would ...

  6. Quantifying stomatal and non-stomatal limitations to carbon assimilation resulting from leaf aging and drought in mature deciduous tree species.

    PubMed

    Wilson, Kell B.; Baldocchi, Dennis D.; Hanson, Paul J.

    2000-06-01

    Gas exchange techniques were used to investigate light-saturated carbon assimilation and its stomatal and non-stomatal limitations over two seasons in mature trees of five species in a closed deciduous forest. Stomatal and non-stomatal contributions to decreases in assimilation resulting from leaf age and drought were quantified relative to the maximum rates obtained early in the season at optimal soil water contents. Although carbon assimilation, stomatal conductance and photosynthetic capacity (V(cmax)) decreased with leaf age, decreases in V(cmax) accounted for about 75% of the leaf-age related reduction in light-saturated assimilation rates, with a secondary role for stomatal conductance (around 25%). However, when considered independently from leaf age, the drought response was dominated by stomatal limitations, accounting for about 75% of the total limitation. Some of the analytical difficulties associated with computing limitation partitioning are discussed, including path dependence, patchy stomatal closure and diffusion in the mesophyll. Although these considerations may introduce errors in our estimates, our analysis establishes some reasonable boundaries on relative limitations and shows differences between drought and non-drought years. Estimating seasonal limitations under natural conditions, as shown in this study, provides a useful basis for comparing limitation processes between years and species.

  7. Daytime nap controls toddlers’ nighttime sleep

    PubMed Central

    Nakagawa, Machiko; Ohta, Hidenobu; Nagaoki, Yuko; Shimabukuro, Rinshu; Asaka, Yoko; Takahashi, Noriko; Nakazawa, Takayo; Kaneshi, Yousuke; Morioka, Keita; Oishi, Yoshihisa; Azami, Yuriko; Ikeuchi, Mari; Takahashi, Mari; Hirata, Michio; Ozawa, Miwa; Cho, Kazutoshi; Kusakawa, Isao; Yoda, Hitoshi

    2016-01-01

    Previous studies have demonstrated that afternoon naps can have a negative effect on subsequent nighttime sleep in children. These studies have mainly been based on sleep questionnaires completed by parents. To investigate the effect of napping on such aspects of sleep quality, we performed a study in which child activity and sleep levels were recorded using actigraphy. The parents were asked to attach actigraphy units to their child’s waist by an adjustable elastic belt and complete a sleep diary for 7 consecutive days. 50 healthy young toddlers of approximately 1.5 years of age were recruited. There was a significant negative correlation between nap duration and both nighttime sleep duration and sleep onset time, suggesting that long nap sleep induces short nighttime sleep duration and late sleep onset time. We also found a significant negative correlation between nap timing and nighttime sleep duration and also a significant positive correlation between nap timing and sleep onset time, suggesting that naps in the late afternoon also lead to short nighttime sleep duration and late sleep onset. Our findings suggest that duration-controlled naps starting early in the afternoon can induce a longer nighttime sleep in full-term infants of approximately 1.5 years of age. PMID:27277329

  8. Modelled hydraulic redistribution by sunflower (Helianthus annuus L.) matches observed data only after including night-time transpiration.

    PubMed

    Neumann, Rebecca B; Cardon, Zoe G; Teshera-Levye, Jennifer; Rockwell, Fulton E; Zwieniecki, Maciej A; Holbrook, N Michele

    2014-04-01

    The movement of water from moist to dry soil layers through the root systems of plants, referred to as hydraulic redistribution (HR), occurs throughout the world and is thought to influence carbon and water budgets and ecosystem functioning. The realized hydrologic, biogeochemical and ecological consequences of HR depend on the amount of redistributed water, whereas the ability to assess these impacts requires models that correctly capture HR magnitude and timing. Using several soil types and two ecotypes of sunflower (Helianthus annuus L.) in split-pot experiments, we examined how well the widely used HR modelling formulation developed by Ryel et al. matched experimental determination of HR across a range of water potential driving gradients. H. annuus carries out extensive night-time transpiration, and although over the last decade it has become more widely recognized that night-time transpiration occurs in multiple species and many ecosystems, the original Ryel et al. formulation does not include the effect of night-time transpiration on HR. We developed and added a representation of night-time transpiration into the formulation, and only then was the model able to capture the dynamics and magnitude of HR we observed as soils dried and night-time stomatal behaviour changed, both influencing HR.

  9. The relationship between daytime and nighttime food intake in an obese night-eater.

    PubMed

    Aronoff, N J; Geliebter, A; Hashim, S A; Zammit, G K

    1994-03-01

    Some obese individuals consume food during awakenings from nighttime sleep. Three studies were conducted on a 28-year-old morbidly obese male with chronic sleeping complaints and insignificant weight loss, despite self-reported daily caloric restriction: I. For 3 mo, the subject recorded food intake for 24-h periods. Mean daytime intake was 1286 kcal +/- 386 (SD), and mean nighttime intake was 1036 kcal +/- 487 (SD). Caloric values of daytime and nighttime intake were negatively correlated, r = -0.22, df= 82, p < .05. II. Seven consecutive 24-h food intake recordings were obtained with an automated formula dispenser when the subject was an inpatient on a metabolic ward and received ad libitum formula as his sole food source. Mean daytime intake was 1245 +/- 662 (SD), and mean nighttime intake was 231 +/- 236 (SD). There was a non-significant negative correlation between daytime and nighttime intake, r = -0.32, df = 5, NS. III. The subject underwent polysomnographic studies on 2 non-consecutive nights, following the administration of either a low (600 kcal) or high (1800 kcal) daytime caloric condition. The subject, upon awakening from nighttime sleep, could eat from a platter of sandwich quarters placed at his bedside. The addition of 1200 kcal to daytime intake decreased nighttime intake by 654 kcal, or by 55% of the additional calories delivered during the day. The three studies (I, II, and III) show that daytime food intake can be negatively correlated with nighttime intake, and that daytime intake can influence nighttime intake in a documented obese night-eater.

  10. Balancing Water Uptake and Loss through the Coordinated Regulation of Stomatal and Root Development.

    PubMed

    Hepworth, Christopher; Turner, Carla; Landim, Marcela Guimaraes; Cameron, Duncan; Gray, Julie E

    2016-01-01

    Root development is influenced by nutrient and water availabilities. Plants are able to adjust many attributes of their root in response to environmental signals including the size and shape of the primary root, lateral roots and root hairs. Here we investigated the response of roots to changes in the levels of leaf transpiration associated with altered stomatal frequency. We found that plants with high stomatal density and conductance produce a larger rooting area and as a result have enhanced phosphate uptake capacity whereas plants with low stomatal conductance produce a smaller root. Manipulating the growth environment of plants indicated that enhanced root growth is most likely a result of an increased demand for water rather than phosphate. Plants manipulated to have an increase or reduction in root hair growth show a reduction or increase respectively, in stomatal conductance and density. Our results demonstrate that plants can balance their water uptake and loss through coordinated regulation of both stomatal and root development. PMID:27275842

  11. Balancing Water Uptake and Loss through the Coordinated Regulation of Stomatal and Root Development

    PubMed Central

    Hepworth, Christopher; Turner, Carla; Landim, Marcela Guimaraes; Cameron, Duncan; Gray, Julie E.

    2016-01-01

    Root development is influenced by nutrient and water availabilities. Plants are able to adjust many attributes of their root in response to environmental signals including the size and shape of the primary root, lateral roots and root hairs. Here we investigated the response of roots to changes in the levels of leaf transpiration associated with altered stomatal frequency. We found that plants with high stomatal density and conductance produce a larger rooting area and as a result have enhanced phosphate uptake capacity whereas plants with low stomatal conductance produce a smaller root. Manipulating the growth environment of plants indicated that enhanced root growth is most likely a result of an increased demand for water rather than phosphate. Plants manipulated to have an increase or reduction in root hair growth show a reduction or increase respectively, in stomatal conductance and density. Our results demonstrate that plants can balance their water uptake and loss through coordinated regulation of both stomatal and root development. PMID:27275842

  12. Stomatal factors and vulnerability of stem xylem to cavitation in poplars.

    PubMed

    Arango-Velez, Adriana; Zwiazek, Janusz J; Thomas, Barb R; Tyree, Melvin T

    2011-10-01

    The relationships between the vulnerability of stem xylem to cavitation, stomatal conductance, stomatal density, and leaf and stem water potential were examined in six hybrid poplar (P38P38, Walker, Okanese, Northwest, Assiniboine and Berlin) and balsam poplar (Populus balsamifera) clones. Stem xylem cavitation resistance was examined with the Cavitron technique in well-watered plants grown in the greenhouse. To investigate stomatal responses to drought, plants were subjected to drought stress by withholding watering for 5 (mild drought) and 7 (severe drought) days and to stress recovery by rewatering severely stressed plants for 30 min and 2 days. The clones varied in stomatal sensitivity to drought and vulnerability to stem xylem cavitation. P38P38 reduced stomatal conductance in response to mild stress while the balsam poplar clone maintained high leaf stomatal conductance under more severe drought stress conditions. Differences between the severely stressed clones were also observed in leaf water potentials with no or relatively small decreases in Assiniboine, P38P38, Okanese and Walker. Vulnerability to drought-induced stem xylem embolism revealed that balsam poplar and Northwest clones reached loss of conductivity at lower stem water potentials compared with the remaining clones. There was a strong link between stem xylem resistance to cavitation and stomatal responsiveness to drought stress in balsam poplar and P38P38. However, the differences in stomatal responsiveness to mild drought suggest that other drought-resistant strategies may also play a key role in some clones of poplars exposed to drought stress.

  13. Blue Light Induces a Distinct Starch Degradation Pathway in Guard Cells for Stomatal Opening.

    PubMed

    Horrer, Daniel; Flütsch, Sabrina; Pazmino, Diana; Matthews, Jack S A; Thalmann, Matthias; Nigro, Arianna; Leonhardt, Nathalie; Lawson, Tracy; Santelia, Diana

    2016-02-01

    Stomatal pores form a crucial interface between the leaf mesophyll and the atmosphere, controlling water and carbon balance in plants [1]. Major advances have been made in understanding the regulatory networks and ion fluxes in the guard cells surrounding the stomatal pore [2]. However, our knowledge on the role of carbon metabolism in these cells is still fragmentary [3-5]. In particular, the contribution of starch in stomatal opening remains elusive [6]. Here, we used Arabidopsis thaliana as a model plant to provide the first quantitative analysis of starch turnover in guard cells of intact leaves during the diurnal cycle. Starch is present in guard cells at the end of night, unlike in the rest of the leaf, but is rapidly degraded within 30 min of light. This process is critical for the rapidity of stomatal opening and biomass production. We exploited Arabidopsis molecular genetics to define the mechanism and regulation of guard cell starch metabolism, showing it to be mediated by a previously uncharacterized pathway. This involves the synergistic action of β-amylase 1 (BAM1) and α-amylase 3 (AMY3)-enzymes that are normally not required for nighttime starch degradation in other leaf tissues. This pathway is under the control of the phototropin-dependent blue-light signaling cascade and correlated with the activity of the plasma membrane H(+)-ATPase. Our results show that guard cell starch degradation has an important role in plant growth by driving stomatal responses to light.

  14. Separating Active and Passive Influences on Stomatal Control of Transpiration[OPEN

    PubMed Central

    McAdam, Scott A.M.; Brodribb, Timothy J.

    2014-01-01

    Motivated by studies suggesting that the stomata of ferns and lycophytes do not conform to the standard active abscisic acid (ABA) -mediated stomatal control model, we examined stomatal behavior in a conifer species (Metasequoia glyptostroboides) that is phylogenetically midway between the fern and angiosperm clades. Similar to ferns, daytime stomatal closure in response to moderate water stress seemed to be a passive hydraulic process in M. glyptostroboides immediately alleviated by rehydrating excised shoots. Only after prolonged exposure to more extreme water stress did active ABA-mediated stomatal closure become important, because foliar ABA production was triggered after leaf turgor loss. The influence of foliar ABA on stomatal conductance and stomatal aperture was highly predictable and additive with the passive hydraulic influence. M. glyptostroboides thus occupies a stomatal behavior type intermediate between the passively controlled ferns and the characteristic ABA-dependent stomatal closure described in angiosperm herbs. These results highlight the importance of considering phylogeny as a major determinant of stomatal behavior. PMID:24488969

  15. Circadian Rhythms in Stomatal Responsiveness to Red and Blue Light.

    PubMed Central

    Gorton, H. L.; Williams, W. E.; Assmann, S. M.

    1993-01-01

    Stomata of many plants have circadian rhythms in responsiveness to environmental cues as well as circadian rhythms in aperture. Stomatal responses to red light and blue light are mediated by photosynthetic photoreceptors; responses to blue light are additionally controlled by a specific blue-light photoreceptor. This paper describes circadian rhythmic aspects of stomatal responsiveness to red and blue light in Vicia faba. Plants were exposed to a repeated light:dark regime of 1.5:2.5 h for a total of 48 h, and because the plants could not entrain to this short light:dark cycle, circadian rhythms were able to "free run" as if in continuous light. The rhythm in the stomatal conductance established during the 1.5-h light periods was caused both by a rhythm in sensitivity to light and by a rhythm in the stomatal conductance established during the preceding 2.5-h dark periods. Both rhythms peaked during the middle of the subjective day. Although the stomatal response to blue light is greater than the response to red light at all times of day, there was no discernible difference in period, phase, or amplitude of the rhythm in sensitivity to the two light qualities. We observed no circadian rhythmicity in net carbon assimilation with the 1.5:2.5 h light regime for either red or blue light. In continuous white light, small rhythmic changes in photosynthetic assimilation were observed, but at relatively high light levels, and these appeared to be attributable largely to changes in internal CO2 availability governed by stomatal conductance. PMID:12231947

  16. Gas valves, forests and global change: a commentary on Jarvis (1976) 'The interpretation of the variations in leaf water potential and stomatal conductance found in canopies in the field'.

    PubMed

    Beerling, David J

    2015-04-19

    Microscopic turgor-operated gas valves on leaf surfaces-stomata-facilitate gas exchange between the plant and the atmosphere, and respond to multiple environmental and endogenous cues. Collectively, stomatal activities affect everything from the productivity of forests, grasslands and crops to biophysical feedbacks between land surface vegetation and climate. In 1976, plant physiologist Paul Jarvis reported an empirical model describing stomatal responses to key environmental and plant conditions that predicted the flux of water vapour from leaves into the surrounding atmosphere. Subsequent theoretical advances, building on this earlier approach, established the current paradigm for capturing the physiological behaviour of stomata that became incorporated into sophisticated models of land carbon cycling. However, these models struggle to accurately predict observed trends in the physiological responses of Northern Hemisphere forests to recent atmospheric CO2 increases, highlighting the need for improved representation of the role of stomata in regulating forest-climate interactions. Bridging this gap between observations and theory as atmospheric CO2 rises and climate change accelerates creates challenging opportunities for the next generation of physiologists to advance planetary ecology and climate science. This commentary was written to celebrate the 350th anniversary of the journal Philosophical Transactions of the Royal Society. PMID:25750234

  17. Gas valves, forests and global change: a commentary on Jarvis (1976) 'The interpretation of the variations in leaf water potential and stomatal conductance found in canopies in the field'.

    PubMed

    Beerling, David J

    2015-04-19

    Microscopic turgor-operated gas valves on leaf surfaces-stomata-facilitate gas exchange between the plant and the atmosphere, and respond to multiple environmental and endogenous cues. Collectively, stomatal activities affect everything from the productivity of forests, grasslands and crops to biophysical feedbacks between land surface vegetation and climate. In 1976, plant physiologist Paul Jarvis reported an empirical model describing stomatal responses to key environmental and plant conditions that predicted the flux of water vapour from leaves into the surrounding atmosphere. Subsequent theoretical advances, building on this earlier approach, established the current paradigm for capturing the physiological behaviour of stomata that became incorporated into sophisticated models of land carbon cycling. However, these models struggle to accurately predict observed trends in the physiological responses of Northern Hemisphere forests to recent atmospheric CO2 increases, highlighting the need for improved representation of the role of stomata in regulating forest-climate interactions. Bridging this gap between observations and theory as atmospheric CO2 rises and climate change accelerates creates challenging opportunities for the next generation of physiologists to advance planetary ecology and climate science. This commentary was written to celebrate the 350th anniversary of the journal Philosophical Transactions of the Royal Society.

  18. Gas valves, forests and global change: a commentary on Jarvis (1976) ‘The interpretation of the variations in leaf water potential and stomatal conductance found in canopies in the field’

    PubMed Central

    Beerling, David J.

    2015-01-01

    Microscopic turgor-operated gas valves on leaf surfaces—stomata—facilitate gas exchange between the plant and the atmosphere, and respond to multiple environmental and endogenous cues. Collectively, stomatal activities affect everything from the productivity of forests, grasslands and crops to biophysical feedbacks between land surface vegetation and climate. In 1976, plant physiologist Paul Jarvis reported an empirical model describing stomatal responses to key environmental and plant conditions that predicted the flux of water vapour from leaves into the surrounding atmosphere. Subsequent theoretical advances, building on this earlier approach, established the current paradigm for capturing the physiological behaviour of stomata that became incorporated into sophisticated models of land carbon cycling. However, these models struggle to accurately predict observed trends in the physiological responses of Northern Hemisphere forests to recent atmospheric CO2 increases, highlighting the need for improved representation of the role of stomata in regulating forest–climate interactions. Bridging this gap between observations and theory as atmospheric CO2 rises and climate change accelerates creates challenging opportunities for the next generation of physiologists to advance planetary ecology and climate science. This commentary was written to celebrate the 350th anniversary of the journal Philosophical Transactions of the Royal Society. PMID:25750234

  19. Brassinosteroids tailor stomatal production to different environments.

    PubMed

    Gudesblat, Gustavo E; Betti, Camilla; Russinova, Eugenia

    2012-12-01

    Two recent reports show that brassinosteroids control stomata production by regulating the GSK3-like kinase BIN2-mediated phosphorylation of two different stomatal signalling components resulting in opposite stomatal phenotypes. We discuss how these two mechanisms might differentially control stomatal generation under diverse growth conditions. PMID:23022359

  20. Brassinosteroids tailor stomatal production to different environments.

    PubMed

    Gudesblat, Gustavo E; Betti, Camilla; Russinova, Eugenia

    2012-12-01

    Two recent reports show that brassinosteroids control stomata production by regulating the GSK3-like kinase BIN2-mediated phosphorylation of two different stomatal signalling components resulting in opposite stomatal phenotypes. We discuss how these two mechanisms might differentially control stomatal generation under diverse growth conditions.

  1. Increasing water-use efficiency directly through genetic manipulation of stomatal density.

    PubMed

    Franks, Peter J; W Doheny-Adams, Timothy; Britton-Harper, Zoe J; Gray, Julie E

    2015-07-01

    Improvement in crop water-use efficiency (WUE) is a critical priority for regions facing increased drought or diminished groundwater resources. Despite new tools for the manipulation of stomatal development, the engineering of plants with high WUE remains a challenge. We used Arabidopsis epidermal patterning factor (EPF) mutants exhibiting altered stomatal density to test whether WUE could be improved directly by manipulation of the genes controlling stomatal density. Specifically, we tested whether constitutive overexpression of EPF2 reduced stomatal density and maximum stomatal conductance (gw(max) ) sufficiently to increase WUE. We found that a reduction in gw(max) via reduced stomatal density in EPF2-overexpressing plants (EPF2OE) increased both instantaneous and long-term WUE without altering significantly the photosynthetic capacity. Conversely, plants lacking both EPF1 and EPF2 expression (epf1epf2) exhibited higher stomatal density, higher gw(max) and lower instantaneous WUE, as well as lower (but not significantly so) long-term WUE. Targeted genetic modification of stomatal conductance, such as in EPF2OE, is a viable approach for the engineering of higher WUE in crops, particularly in future high-carbon-dioxide (CO2 ) atmospheres. PMID:25754246

  2. Light-Induced Stomatal Opening Is Affected by the Guard Cell Protein Kinase APK1b

    PubMed Central

    Elhaddad, Nagat S.; Hunt, Lee; Sloan, Jennifer; Gray, Julie E.

    2014-01-01

    Guard cells allow land plants to survive under restricted or fluctuating water availability. They control the exchange of gases between the external environment and the interior of the plant by regulating the aperture of stomatal pores in response to environmental stimuli such as light intensity, and are important regulators of plant productivity. Their turgor driven movements are under the control of a signalling network that is not yet fully characterised. A reporter gene fusion confirmed that the Arabidopsis APK1b protein kinase gene is predominantly expressed in guard cells. Infrared gas analysis and stomatal aperture measurements indicated that plants lacking APK1b are impaired in their ability to open their stomata on exposure to light, but retain the ability to adjust their stomatal apertures in response to darkness, abscisic acid or lack of carbon dioxide. Stomatal opening was not specifically impaired in response to either red or blue light as both of these stimuli caused some increase in stomatal conductance. Consistent with the reduction in maximum stomatal conductance, the relative water content of plants lacking APK1b was significantly increased under both well-watered and drought conditions. We conclude that APK1b is required for full stomatal opening in the light but is not required for stomatal closure. PMID:24828466

  3. Light-induced stomatal opening is affected by the guard cell protein kinase APK1b.

    PubMed

    Elhaddad, Nagat S; Hunt, Lee; Sloan, Jennifer; Gray, Julie E

    2014-01-01

    Guard cells allow land plants to survive under restricted or fluctuating water availability. They control the exchange of gases between the external environment and the interior of the plant by regulating the aperture of stomatal pores in response to environmental stimuli such as light intensity, and are important regulators of plant productivity. Their turgor driven movements are under the control of a signalling network that is not yet fully characterised. A reporter gene fusion confirmed that the Arabidopsis APK1b protein kinase gene is predominantly expressed in guard cells. Infrared gas analysis and stomatal aperture measurements indicated that plants lacking APK1b are impaired in their ability to open their stomata on exposure to light, but retain the ability to adjust their stomatal apertures in response to darkness, abscisic acid or lack of carbon dioxide. Stomatal opening was not specifically impaired in response to either red or blue light as both of these stimuli caused some increase in stomatal conductance. Consistent with the reduction in maximum stomatal conductance, the relative water content of plants lacking APK1b was significantly increased under both well-watered and drought conditions. We conclude that APK1b is required for full stomatal opening in the light but is not required for stomatal closure.

  4. Guard cell photosynthesis is critical for stomatal turgor production, yet does not directly mediate CO2- and ABA-induced stomatal closing

    PubMed Central

    Azoulay-Shemer, Tamar; Palomares, Axxell; Bagheri, Andish; Israelsson-Nordstrom, Maria; Engineer, Cawas B.; Bargmann, Bastiaan O.R.; Stephan, Aaron B.; Schroeder, Julian I.

    2015-01-01

    SUMMARY Stomata mediate gas exchange between the inter-cellular spaces of leaves and the atmosphere. CO2 levels in leaves (Ci) are determined by respiration, photosynthesis, stomatal conductance and atmospheric [CO2]. [CO2] in leaves mediates stomatal movements. The role of guard-cell photosynthesis in stomatal conductance responses is a matter of debate, and genetic approaches are needed. We have generated transgenic Arabidopsis plants that are chlorophyll-deficient in guard cells only, expressing a constitutively active chlorophyllase in a guard-cell specific enhancer trap-line. Our data show that more than 90% of guard cells were chlorophyll-deficient. Interestingly, approximately ~ 45% of stomata had an unusual, previously not-described, morphology of thin-shaped chlorophyll-less stomata. Nevertheless, stomatal size, stomatal index, plant morphology, and whole-leaf photosynthetic parameters (PSII, qP, qN, FV′/FM′) were comparable to wild-type plants. Time-resolved intact leaf gas exchange analyses showed a reduction in stomatal conductance and carbon assimilation rates of the transgenic plants. Normalization of CO2 responses showed that stomata of transgenic plants respond to [CO2] shifts. Detailed stomatal aperture measurements of normal kidney-shaped stomata, which lack chlorophyll, showed stomatal closing responses to [CO2] elevation and abscisic acid (ABA), while thin-shaped stomata were continuously closed. Our present findings show that stomatal movement responses to [CO2] and ABA are functional in guard cells that lack chlorophyll. These data suggest that guard-cell CO2 and ABA signal transduction are not directly modulated by guard-cell photosynthesis/electron transport. Moreover, the finding that chlorophyll-less stomata cause a “deflated” thin-shaped phenotype, suggests that photosynthesis in guard cells is critical for energization and guard-cell turgor production. PMID:26096271

  5. Guard cell photosynthesis is critical for stomatal turgor production, yet does not directly mediate CO2 - and ABA-induced stomatal closing.

    PubMed

    Azoulay-Shemer, Tamar; Palomares, Axxell; Bagheri, Andisheh; Israelsson-Nordstrom, Maria; Engineer, Cawas B; Bargmann, Bastiaan O R; Stephan, Aaron B; Schroeder, Julian I

    2015-08-01

    Stomata mediate gas exchange between the inter-cellular spaces of leaves and the atmosphere. CO2 levels in leaves (Ci) are determined by respiration, photosynthesis, stomatal conductance and atmospheric [CO2 ]. [CO2 ] in leaves mediates stomatal movements. The role of guard cell photosynthesis in stomatal conductance responses is a matter of debate, and genetic approaches are needed. We have generated transgenic Arabidopsis plants that are chlorophyll-deficient in guard cells only, expressing a constitutively active chlorophyllase in a guard cell specific enhancer trap line. Our data show that more than 90% of guard cells were chlorophyll-deficient. Interestingly, approximately 45% of stomata had an unusual, previously not-described, morphology of thin-shaped chlorophyll-less stomata. Nevertheless, stomatal size, stomatal index, plant morphology, and whole-leaf photosynthetic parameters (PSII, qP, qN, FV '/FM' ) were comparable with wild-type plants. Time-resolved intact leaf gas-exchange analyses showed a reduction in stomatal conductance and CO2 -assimilation rates of the transgenic plants. Normalization of CO2 responses showed that stomata of transgenic plants respond to [CO2 ] shifts. Detailed stomatal aperture measurements of normal kidney-shaped stomata, which lack chlorophyll, showed stomatal closing responses to [CO2 ] elevation and abscisic acid (ABA), while thin-shaped stomata were continuously closed. Our present findings show that stomatal movement responses to [CO2 ] and ABA are functional in guard cells that lack chlorophyll. These data suggest that guard cell CO2 and ABA signal transduction are not directly modulated by guard cell photosynthesis/electron transport. Moreover, the finding that chlorophyll-less stomata cause a 'deflated' thin-shaped phenotype, suggests that photosynthesis in guard cells is critical for energization and guard cell turgor production. PMID:26096271

  6. Guard cell photosynthesis is critical for stomatal turgor production, yet does not directly mediate CO2 - and ABA-induced stomatal closing.

    PubMed

    Azoulay-Shemer, Tamar; Palomares, Axxell; Bagheri, Andisheh; Israelsson-Nordstrom, Maria; Engineer, Cawas B; Bargmann, Bastiaan O R; Stephan, Aaron B; Schroeder, Julian I

    2015-08-01

    Stomata mediate gas exchange between the inter-cellular spaces of leaves and the atmosphere. CO2 levels in leaves (Ci) are determined by respiration, photosynthesis, stomatal conductance and atmospheric [CO2 ]. [CO2 ] in leaves mediates stomatal movements. The role of guard cell photosynthesis in stomatal conductance responses is a matter of debate, and genetic approaches are needed. We have generated transgenic Arabidopsis plants that are chlorophyll-deficient in guard cells only, expressing a constitutively active chlorophyllase in a guard cell specific enhancer trap line. Our data show that more than 90% of guard cells were chlorophyll-deficient. Interestingly, approximately 45% of stomata had an unusual, previously not-described, morphology of thin-shaped chlorophyll-less stomata. Nevertheless, stomatal size, stomatal index, plant morphology, and whole-leaf photosynthetic parameters (PSII, qP, qN, FV '/FM' ) were comparable with wild-type plants. Time-resolved intact leaf gas-exchange analyses showed a reduction in stomatal conductance and CO2 -assimilation rates of the transgenic plants. Normalization of CO2 responses showed that stomata of transgenic plants respond to [CO2 ] shifts. Detailed stomatal aperture measurements of normal kidney-shaped stomata, which lack chlorophyll, showed stomatal closing responses to [CO2 ] elevation and abscisic acid (ABA), while thin-shaped stomata were continuously closed. Our present findings show that stomatal movement responses to [CO2 ] and ABA are functional in guard cells that lack chlorophyll. These data suggest that guard cell CO2 and ABA signal transduction are not directly modulated by guard cell photosynthesis/electron transport. Moreover, the finding that chlorophyll-less stomata cause a 'deflated' thin-shaped phenotype, suggests that photosynthesis in guard cells is critical for energization and guard cell turgor production.

  7. [Effects of nighttime warming on winter wheat root growth and soil nutrient availability].

    PubMed

    Zhang, Ming-Qian; Chen, Jin; Guo, Jia; Tian, Yun-Lu; Yang, Shi-Jia; Zhang, Li; Yang, Bing; Zhang, Wei-Jian

    2013-02-01

    Climate warming has an obvious asymmetry between day and night, with a greater increment of air temperature at nighttime than at daytime. By adopting passive nighttime warming (PNW) system, a two-year field experiment of nighttime warming was conducted in the main production areas of winter wheat in China (Shijiazhuang of Hebei Province, Xuzhou of Jiangsu Province, Xuchang of Henan Province, and Zhenjiang of Jiangsu Province) in 2009 and 2010, with the responses of soil pH and available nutrient contents during the whole growth periods and of wheat root characteristics at heading stage determined. As compared with the control (no nighttime warming), nighttime warming decreased the soil pH and available nutrient contents significantly, and increased the root dry mass and root/shoot ratio to a certain extent. During the whole growth period of winter wheat, nighttime warming decreased the soil pH in Shijiazhuang, Xuzhou, Xuchang, and Zhenjiang averagely by 0.4%, 0.4%, 0.7%, and 0.9%, the soil alkaline nitrogen content averagely by 8.1%, 8.1%, 7.1%, and 6.0%, the soil available phosphorus content averagely by 15.7%, 12.1%, 19.6%, and 25.8%, and the soil available potassium content averagely by 11.5%, 7.6%, 7.6% , and 10.1%, respectively. However, nighttime warming increased the wheat root dry mass at heading stage in Shijiazhuang, Xuzhou, and Zhenjiang averagely by 31. 5% , 27.0%, and 14.5%, and the root/shoot ratio at heading stage in Shijiazhuang, Xuchang, and Zhenjiang averagely by 23.8%, 13.7% and 9.7%, respectively. Our results indicated that nighttime warming could affect the soil nutrient supply and winter wheat growth via affecting the soil chemical properties. PMID:23705390

  8. [Effects of nighttime warming on winter wheat root growth and soil nutrient availability].

    PubMed

    Zhang, Ming-Qian; Chen, Jin; Guo, Jia; Tian, Yun-Lu; Yang, Shi-Jia; Zhang, Li; Yang, Bing; Zhang, Wei-Jian

    2013-02-01

    Climate warming has an obvious asymmetry between day and night, with a greater increment of air temperature at nighttime than at daytime. By adopting passive nighttime warming (PNW) system, a two-year field experiment of nighttime warming was conducted in the main production areas of winter wheat in China (Shijiazhuang of Hebei Province, Xuzhou of Jiangsu Province, Xuchang of Henan Province, and Zhenjiang of Jiangsu Province) in 2009 and 2010, with the responses of soil pH and available nutrient contents during the whole growth periods and of wheat root characteristics at heading stage determined. As compared with the control (no nighttime warming), nighttime warming decreased the soil pH and available nutrient contents significantly, and increased the root dry mass and root/shoot ratio to a certain extent. During the whole growth period of winter wheat, nighttime warming decreased the soil pH in Shijiazhuang, Xuzhou, Xuchang, and Zhenjiang averagely by 0.4%, 0.4%, 0.7%, and 0.9%, the soil alkaline nitrogen content averagely by 8.1%, 8.1%, 7.1%, and 6.0%, the soil available phosphorus content averagely by 15.7%, 12.1%, 19.6%, and 25.8%, and the soil available potassium content averagely by 11.5%, 7.6%, 7.6% , and 10.1%, respectively. However, nighttime warming increased the wheat root dry mass at heading stage in Shijiazhuang, Xuzhou, and Zhenjiang averagely by 31. 5% , 27.0%, and 14.5%, and the root/shoot ratio at heading stage in Shijiazhuang, Xuchang, and Zhenjiang averagely by 23.8%, 13.7% and 9.7%, respectively. Our results indicated that nighttime warming could affect the soil nutrient supply and winter wheat growth via affecting the soil chemical properties.

  9. Stomatal limitation to carbon gain in Paphiopedilum sp. (Orchidaceae) and its reversal by blue light

    SciTech Connect

    Zeiger, E.; Grivet, C.; Assmann, S.M.; Dietzer, G.F.; Hannegan, M.W.

    1985-02-01

    Leaves from Paphiopedilum sp. (Orchidaceae) having achlorophyllous stomata, show reduced levels of stomatal conductance when irradiated with red light, as compared with either the related, chlorophyllous genus Phragmipedium or with their response to blue light. These reduced levels of stomatal conductance, and the failure of isolated Paphiopedilum stomata to open under red irradiation indicates that the small stomatal response measured in the intact leaf under red light is indirect. The overall low levels of stomatal conductance observed in Paphiopedilum leaves under most growing conditions and their capacity to increase stomatal conductance in response to blue light suggested that growth and carbon gain in Paphiopedilum could be enhanced in a blue light-enriched environment. To test that hypothesis, plants of Paphiopedilum acmodontum were grown in controlled growth chambers under daylight fluorescent light, with or without blue light supplementation. Blue light enrichment resulted in significantly higher growth rates over a 3 to 4 week growing period, with all evidence indicating that the blue light effect was a stomatal response. Manipulations of stomatal properties aimed at long-term carbon gains could have agronomic applications.

  10. Urban Legends Series: Recurrent Aphthous Stomatitis

    PubMed Central

    Baccaglini, Lorena; Lalla, Rajesh V.; Bruce, Alison J.; Sartori-Valinotti, Julio C.; Latortue, Marie C.; Carrozzo, Marco; Rogers, Roy S.

    2011-01-01

    Recurrent aphthous stomatitis (RAS) is the most common idiopathic intraoral ulcerative disease in the USA. Aphthae typically occur in apparently healthy individuals, although an association with certain systemic diseases has been reported. Despite the unclear etiopathogenesis, new drug trials are continuously conducted in an attempt to reduce pain and dysfunction. We investigated four controversial topics: (1) Is complex aphthosis a mild form of Behçet’s disease (BD)? (2) Is periodic fever, aphthous stomatitis, pharyngitis and adenitis (PFAPA) syndrome a distinct medical entity? (3) Is RAS associated with other systemic diseases (e.g., celiac disease and B12 deficiency)? (4) Are there any new RAS treatments? Results from extensive literature searches, including a systematic review of RAS trials, suggested that: (1) Complex aphthosis is not a mild form of BD in North America or Western Europe; (2) Diagnostic criteria for PFAPA have low specificity and the characteristics of the oral ulcers warrant further studies; (3) Oral ulcers may be associated with celiac disease; however, these ulcers may not be RAS; RAS is rarely associated with B12 deficiency; nevertheless, B12 treatment may be beneficial, via mechanisms that warrant further study; (4) Thirty-three controlled trials published in the past 6 years reported some effectiveness, though potential for bias was high. PMID:21812866

  11. Ozone slows stomatal response to light and leaf wounding in a Mediterranean evergreen broadleaf, Arbutus unedo.

    PubMed

    Paoletti, Elena

    2005-04-01

    The effect of a 90-d ozone exposure (charcoal-filtered air or 110 nmol mol(-1) O3) on stomatal conductance (gs) was investigated in the Mediterranean evergreen broadleaf Arbutus unedo L. Ozone did not significantly reduce midday steady-state gs compared to controls. However, it slowed stomatal response to abrupt reduction of light intensity and to increasing water stress, applied by severing the leaf midrib. Ozone slowed stomatal closure, rather than aperture. Nevertheless, vein-cutting did not allow ozonated leaves to reach the pre-injury gs levels, like controls did, suggesting re-opening was still, slowly in progress. The sluggish behaviour was recorded 10 days after cessation of O3 exposure ("memory effect") and may affect stomatal control in response to sunflecks and leaf wounding. Mediterranean evergreen broadleaves are regarded as tolerant to O3 exposure. Nevertheless, measurements of steady-state gs at midday may not account for altered stomatal responses to stressors. PMID:15620589

  12. Electrical potentials in stomatal complexes

    SciTech Connect

    Saftner, R.A.; Raschke, K.

    1981-06-01

    Guard cells of several species, but predominantly Commelina communis, were impaled by micropipette electrodes and potential differences measured that occurred between cell compartments and the flowing bathing medium. The wall developed a Donnan potential that was between -60 and -70 millivolt in 30 millimolar KC1 at pH 7. The density of the fixed charges ranged from 0.3 to 0.5 molar; its dependence on pH was almost identical with the titration curve of authentic polygalacturonic acid. The vacuolar potential of guard cells of Commelina communis L., Zea mays L., Nicotiana glauca Graham, Allium cepa L., and Vicia faba L. was between -40 and -50 millivolt in 30 millimolar KCl when stomata were open and about -30 millivolt when stomata were closed. The vacuolar potential of guard cells of C. communis was almost linearly related to stomatal aperture and responded to changes in the ionic strength in the bathing medium in a Nernstian manner. No specificity for any alkali ion (except Li/sup +/), ammonium, or choline appeared. Lithium caused hyperpolarization. Calcium in concentrations between 1 and 100 millimolar in the medium led to stomatal closure, also caused hyperpolarization, and triggered transient oscillations in the intracellular potential. Gradients in the electrical potential existed across stomatal complexes with open pores. When stomata closed, these gradients almost disappeared or slightly reverted; all epidermal cells were then at potentials near -30 millivolt in 30 millimolar KCl.

  13. Nighttime Fears and Fantasy-Reality Differentiation in Preschool Children

    ERIC Educational Resources Information Center

    Zisenwine, Tamar; Kaplan, Michal; Kushnir, Jonathan; Sadeh, Avi

    2013-01-01

    Nighttime fears are very common in preschool years. During these years, children's fantasy-reality differentiation undergoes significant development. Our study was aimed at exploring the links between nighttime fears and fantasy-reality differentiation in preschool children. Eighty children (aged: 4-6 years) suffering from severe nighttime fears…

  14. Nighttime parenting strategies and sleep-related risks to infants.

    PubMed

    Volpe, Lane E; Ball, Helen L; McKenna, James J

    2013-02-01

    A large social science and public health literature addresses infant sleep safety, with implications for infant mortality in the context of accidental deaths and Sudden Infant Death Syndrome (SIDS). As part of risk reduction campaigns in the USA, parents are encouraged to place infants supine and to alter infant bedding and elements of the sleep environment, and are discouraged from allowing infants to sleep unsupervised, from bed-sharing either at all or under specific circumstances, or from sofa-sharing. These recommendations are based on findings from large-scale epidemiological studies that generate odds ratios or relative risk statistics for various practices; however, detailed behavioural data on nighttime parenting and infant sleep environments are limited. To address this issue, this paper presents and discusses the implications of four case studies based on overnight observations conducted with first-time mothers and their four-month old infants. These case studies were collected at the Mother-Baby Behavioral Sleep Lab at the University of Notre Dame USA between September 2002 and June 2004. Each case study provides a detailed description based on video analysis of sleep-related risks observed while mother-infant dyads spent the night in a sleep lab. The case studies provide examples of mothers engaged in the strategic management of nighttime parenting for whom sleep-related risks to infants arose as a result of these strategies. Although risk reduction guidelines focus on eliminating potentially risky infant sleep practices as if the probability of death from each were equal, the majority of instances in which these occur are unlikely to result in infant mortality. Therefore, we hypothesise that mothers assess potential costs and benefits within margins of risk which are not acknowledged by risk-reduction campaigns. Exploring why mothers might choose to manage sleep and nighttime parenting in ways that appear to increase potential risks to infants may

  15. Nighttime Parenting Strategies and Sleep-Related Risks to Infants

    PubMed Central

    Volpe, Lane E.; Ball, Helen L.; McKenna, James J.

    2012-01-01

    A large social science and public health literature addresses infant sleep safety, with implications for infant mortality in the context of accidental deaths and Sudden Infant Death Syndrome (SIDS). As part of risk reduction campaigns in the USA, parents are encouraged to place infants supine and to alter infant bedding and elements of the sleep environment, and are discouraged from allowing infants to sleep unsupervised, from bed-sharing either at all or under specific circumstances, or from sofa-sharing. These recommendations are based on findings from large-scale epidemiological studies that generate odds ratios or relative risk statistics for various practices; however, detailed behavioural data on nighttime parenting and infant sleep environments are limited. To address this issue, this paper presents and discusses the implications of four case studies based on overnight observations conducted with first-time mothers and their four-month old infants. These case studies were collected at the Mother-Baby Behavioral Sleep Lab at the University of Notre Dame USA between September 2002 and June 2004.Each case study provides a detailed description based on video analysis of sleep-related risks observed while mother-infant dyads spent the night in a sleep lab. The case studies provide examples of mothers engaged in the strategic management of nighttime parenting for whom sleep-related risks to infants arose as a result of these strategies. Although risk reduction guidelines focus on eliminating potentially risky infant sleep practices as if the probability of death from each were equal, the majority of instances in which these occur are unlikely to result in infant mortality. Therefore, we hypothesise that mothers assess potential costs and benefits within margins of risk which are not acknowledged by risk-reduction campaigns. Exploring why mothers might choose to manage sleep and nighttime parenting in ways that appear to increase potential risks to infants may help

  16. Evidence Regarding the Treatment of Denture Stomatitis.

    PubMed

    Yarborough, Alexandra; Cooper, Lyndon; Duqum, Ibrahim; Mendonça, Gustavo; McGraw, Kathleen; Stoner, Lisa

    2016-06-01

    Denture stomatitis is a common inflammatory condition affecting the mucosa underlying complete dentures. It is associated with denture microbial biofilm, poor denture hygiene, poor denture quality, and nocturnal denture use. Numerous treatment methodologies have been used to treat stomatitis; however, a gold standard treatment has not been identified. The aim of this systematic review is to report on the current knowledge available in studies representing a range of evidence on the treatment of denture stomatitis.

  17. Drought limitations to leaf-level gas exchange: results from a model linking stomatal optimization and cohesion-tension theory.

    PubMed

    Novick, Kimberly A; Miniat, Chelcy F; Vose, James M

    2016-03-01

    We merge concepts from stomatal optimization theory and cohesion-tension theory to examine the dynamics of three mechanisms that are potentially limiting to leaf-level gas exchange in trees during drought: (1) a 'demand limitation' driven by an assumption of optimal stomatal functioning; (2) 'hydraulic limitation' of water movement from the roots to the leaves; and (3) 'non-stomatal' limitations imposed by declining leaf water status within the leaf. Model results suggest that species-specific 'economics' of stomatal behaviour may play an important role in differentiating species along the continuum of isohydric to anisohydric behaviour; specifically, we show that non-stomatal and demand limitations may reduce stomatal conductance and increase leaf water potential, promoting wide safety margins characteristic of isohydric species. We used model results to develop a diagnostic framework to identify the most likely limiting mechanism to stomatal functioning during drought and showed that many of those features were commonly observed in field observations of tree water use dynamics. Direct comparisons of modelled and measured stomatal conductance further indicated that non-stomatal and demand limitations reproduced observed patterns of tree water use well for an isohydric species but that a hydraulic limitation likely applies in the case of an anisohydric species.

  18. Mesophyll photosynthesis and guard cell metabolism impacts on stomatal behaviour.

    PubMed

    Lawson, Tracy; Simkin, Andrew J; Kelly, Gilor; Granot, David

    2014-09-01

    Stomata control gaseous fluxes between the internal leaf air spaces and the external atmosphere. Guard cells determine stomatal aperture and must operate to ensure an appropriate balance between CO2 uptake for photosynthesis (A) and water loss, and ultimately plant water use efficiency (WUE). A strong correlation between A and stomatal conductance (gs ) is well documented and often observed, but the underlying mechanisms, possible signals and metabolites that promote this relationship are currently unknown. In this review we evaluate the current literature on mesophyll-driven signals that may coordinate stomatal behaviour with mesophyll carbon assimilation. We explore a possible role of various metabolites including sucrose and malate (from several potential sources; including guard cell photosynthesis) and new evidence that improvements in WUE have been made by manipulating sucrose metabolism within the guard cells. Finally we discuss the new tools and techniques available for potentially manipulating cell-specific metabolism, including guard and mesophyll cells, in order to elucidate mesophyll-derived signals that coordinate mesophyll CO2 demands with stomatal behaviour, in order to provide a mechanistic understanding of these processes as this may identify potential targets for manipulations in order to improve plant WUE and crop yield.

  19. Monoterpene hydrocarbons in the nighttime troposphere

    SciTech Connect

    Roberts, J.M.; Hahn, C.J.; Fehsenfeld, F.C.; Warnock, J.M.; Albritton, D.L.; Sievers, R.E.

    1985-01-01

    Monoterpene hydrocarbons were measured during the night at a rural site in the Rocky Mountains. The compounds positively identified and quantified were ..cap alpha..-pinene, camphene, ..beta..-pinene, ..delta../sup 3/-carene, and d-limonene. The average sum of the mixing ratios of the five compounds measured during the nighttime between July and Oct., 1982, was 0.63 ppb (volume), which was about twice the corresponding daytime average sum. No significant difference was observed between day and night in the relative concentrations of the individual monoterpenes. Increased atmospheric stability, with attendant reduced mixing and dilution during the night, was found to contribute to the large nighttime vs. daytime monoterpene mixing ratios. Nighttime atmospheric stability was also responsible for the observation of ozone diminution and a corresponding inverse relationship between monoterpene and ozone mixing ratios. The results indicate that, at this site, transport rather than chemistry determines the concentrations of the monoterpenes. The ultimate fate of the monoterpenes is chemical reaction with O/sub 3/, OH, or NO/sub 3/. Because of the differences in rate constants of reactions between the various monoterpenes and the above species, chemical reaction should cause systematic changes in relative concentrations of monoterpenes, which are characteristic of the reactant species involved.

  20. Adverse Health Effects of Nighttime Lighting

    NASA Astrophysics Data System (ADS)

    Motta, M.

    2012-06-01

    The effects of poor lighting and glare on public safety are well-known, as are the harmful environmental effects on various species and the environment in general. What is less well-known is the potential harmful medical effects of excessive poor nighttime lighting. A significant body of research has been developed over the last few years regarding this problem. One of the most significant effects is the startling increased risk for breast cancer by excessive exposure to nighttime lighting. The mechanism is felt to be by disruption of the circadian rhythm and suppression of melatonin production from the pineal gland. Melatonin has an anticancer effect that is lost when its production is disrupted. I am in the process of developing a monograph that will summarize this important body of research, to be presented and endorsed by the American Medical Association, and its Council of Science and Public health. This paper is a brief overall summary of this little known potential harmful effect of poor and excessive nighttime lighting.

  1. Histopathological study of stomatitis nicotina.

    PubMed

    Reddy, C R; Kameswari, V R; Ramulu, C; Reddy, P G

    1971-09-01

    One hundred and thirteen biopsies of the palate in people accustomed to smoking cigars, most of them with the burning end of the cigar inside the mouth, have been studied.Thirty-eight of these showed mild to severe atypical changes in the epithelium. There were 19 lesions showing orthokeratosis and 53 showing hyperorthokeratosis.The earliest atypical change is seen in the mouths of the ducts of the glands.There were 3 cases showing microinvasive carcinomas.Pigmentation is a prominent feature in these cases.The papules with umbilication could be due to hyperplasia of the mucous glands.It is suggested that stomatitis nicotina occurring in men and women with the habit of reverse smoking is probably precancerous because of the presence of atypical changes in the epithelium and also the finding of 3 microinvasive carcinomas without any macroscopic evidence.There is no acceptable explanation why the soft palate escapes getting either stomatitis nicotina lesion or carcinoma in reverse smokers.

  2. Natural variation in stomatal responses to environmental changes among Arabidopsis thaliana ecotypes.

    PubMed

    Takahashi, Sho; Monda, Keina; Negi, Juntaro; Konishi, Fumitaka; Ishikawa, Shinobu; Hashimoto-Sugimoto, Mimi; Goto, Nobuharu; Iba, Koh

    2015-01-01

    Stomata are small pores surrounded by guard cells that regulate gas exchange between plants and the atmosphere. Guard cells integrate multiple environmental signals and control the aperture width to ensure appropriate stomatal function for plant survival. Leaf temperature can be used as an indirect indicator of stomatal conductance to environmental signals. In this study, leaf thermal imaging of 374 Arabidopsis ecotypes was performed to assess their stomatal responses to changes in environmental CO2 concentrations. We identified three ecotypes, Köln (Kl-4), Gabelstein (Ga-0), and Chisdra (Chi-1), that have particularly low responsiveness to changes in CO2 concentrations. We next investigated stomatal responses to other environmental signals in these selected ecotypes, with Col-0 as the reference. The stomatal responses to light were also reduced in the three selected ecotypes when compared with Col-0. In contrast, their stomatal responses to changes in humidity were similar to those of Col-0. Of note, the responses to abscisic acid, a plant hormone involved in the adaptation of plants to reduced water availability, were not entirely consistent with the responses to humidity. This study demonstrates that the stomatal responses to CO2 and light share closely associated signaling mechanisms that are not generally correlated with humidity signaling pathways in these ecotypes. The results might reflect differences between ecotypes in intrinsic response mechanisms to environmental signals. PMID:25706630

  3. Scaling of stomatal size and density optimizes allocation of leaf epidermal space for gas exchange in angiosperms

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

    Stomata on plant leaves are key traits in the regulation of terrestrial fluxes of water and carbon. The basic morphology of stomata consists of a diffusion pore and two guard cells that regulate the exchange of CO2 and water vapour between the leaf interior and the atmosphere. This morphology is common to nearly all land plants, yet stomatal size (defined as the area of the guard cell pair) and stomatal density (the number of stomata per unit area) range over three orders of magnitude across species. Evolution of stomatal sizes and densities is driven by selection pressure on the anatomical maximum stomatal conductance (gsmax), which determines the operational range of leaf gas exchange. Despite the importance of stomata traits for regulating leaf gas exchange, a quantitative understanding of the relation between adaptation of gsmax and the underlying co-evolution of stomatal sizes and densities is still lacking. Here we develop a theoretical framework for a scaling relationship between stomatal sizes and densities within the constraints set by the allocation of epidermal space and stomatal gas exchange. Our theory predicts an optimal scaling relationship that maximizes gsmax and minimizes epidermal space allocation to stomata. We test whether stomatal sizes and densities reflect this optimal scaling with a global compilation of stomatal trait data on 923 species reflecting most major clades. Our results show optimal scaling between stomatal sizes and densities across all species in the compiled data set. Our results also show optimal stomatal scaling across angiosperm species, but not across gymnosperm and fern species. We propose that the evolutionary flexibility of angiosperms to adjust stomatal sizes underlies their optimal allocation of leaf epidermal space to gas exchange.

  4. Transmission and pathogenesis of vesicular stomatitis viruses

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Vesicular Stomatitis (VS) is caused by the Vesicular Stomatitis Virus (VSV), a negative single stranded RNA arthropod-borne virus member of the Family Rhabdoviridae. The virion is composed of the host derived plasma membrane, the envelope, and an internal ribonucleoprotein core. The envelope contain...

  5. Genetic manipulation of stomatal density influences stomatal size, plant growth and tolerance to restricted water supply across a growth carbon dioxide gradient.

    PubMed

    Doheny-Adams, Timothy; Hunt, Lee; Franks, Peter J; Beerling, David J; Gray, Julie E

    2012-02-19

    To investigate the impact of manipulating stomatal density, a collection of Arabidopsis epidermal patterning factor (EPF) mutants with an approximately 16-fold range of stomatal densities (approx. 20-325% of that of control plants) were grown at three atmospheric carbon dioxide (CO(2)) concentrations (200, 450 and 1000 ppm), and 30 per cent or 70 per cent soil water content. A strong negative correlation between stomatal size (S) and stomatal density (D) was observed, suggesting that factors that control D also affect S. Under some but not all conditions, mutant plants exhibited abnormal stomatal density responses to CO(2) concentration, suggesting that the EPF signalling pathway may play a role in the environmental adjustment of D. In response to reduced water availability, maximal stomatal conductance was adjusted through reductions in S, rather than D. Plant size negatively correlated with D. For example, at 450 ppm CO(2) EPF2-overexpressing plants, with reduced D, had larger leaves and increased dry weight in comparison with controls. The growth of these plants was also less adversely affected by reduced water availability than plants with higher D, indicating that plants with low D may be well suited to growth under predicted future atmospheric CO(2) environments and/or water-scarce environments.

  6. Natural variation in stomatal response to closing stimuli among Arabidopsis thaliana accessions after exposure to low VPD as a tool to recognize the mechanism of disturbed stomatal functioning

    PubMed Central

    Aliniaeifard, Sasan; van Meeteren, Uulke

    2014-01-01

    Stomatal responses to closing stimuli are disturbed after long-term exposure of plants to low vapour pressure deficit (VPD). The mechanism behind this disturbance is not fully understood. Genetic variation between naturally occurring ecotypes can be helpful to elucidate the mechanism controlling stomatal movements in different environments. We characterized the stomatal responses of 41 natural accessions of Arabidopsis thaliana to closing stimuli (ABA and desiccation) after they had been exposed for 4 days to moderate VPD (1.17 kPa) or low VPD (0.23 kPa). A fast screening system was used to test stomatal response to ABA using chlorophyll fluorescence imaging under low O2 concentrations of leaf discs floating on ABA solutions. In all accessions stomatal conductance (gs) was increased after prior exposure to low VPD. After exposure to low VPD, stomata of 39 out of 41 of the accessions showed a diminished ABA closing response; only stomata of low VPD-exposed Map-42 and C24 were as responsive to ABA as moderate VPD-exposed plants. In response to desiccation, most of the accessions showed a normal stomata closing response following low VPD exposure. Only low VPD-exposed Cvi-0 and Rrs-7 showed significantly less stomatal closure compared with moderate VPD-exposed plants. Using principle component analysis (PCA), accessions could be categorized to very sensitive, moderately sensitive, and less sensitive to closing stimuli. In conclusion, we present evidence for different stomatal responses to closing stimuli after long-term exposure to low VPD across Arabidopsis accessions. The variation can be a useful tool for finding the mechanism of stomatal malfunctioning. PMID:25205580

  7. Enhanced nighttime gas emissions from a lake

    NASA Astrophysics Data System (ADS)

    Podgrajsek, E.; Sahlée, E.; Rutgersson, A.

    2016-05-01

    Methane (CH4) and carbon dioxide (CO2) are two important greenhouse gases. Previous studies have shown that lakes can be important natural sources of atmospheric CH4 and CO2. It is therefore important to monitor the fluxes of these gases between lakes and the atmosphere in order to understand the processes that govern the exchange. Most previous lake flux studies are based on chamber measurements, by using the eddy covariance method, the resolution in time and in space of the fluxes is increased, which gives more information on the governing processes. Eddy covariance measurements at a Swedish lake show that both methane fluxes (FCH4 ) and carbon dioxide fluxes (FCO2 ) experience high nighttime fluxes for a large part of the data set (largest median FCH4night ≈ 13 nmol m2 s-1 and smallest median FCH4day ≈ 4.0 nmol m-2 s-1, largest median FCO2night ≈ 0.2 μmol m2 s-1 and smallest median FCO2day ≈ 0.02 μmol m-2 s-1, with larger variability during night). For the diel cycle of the CH4 fluxes it is suggested that water side convection could enhance the transfer velocity, transport CH4 rich water to the surface, as well as trigger ebullition. The high nighttime CO2 fluxes could to a large extent be explained with enhanced transfer velocities due to water side convection. If gas fluxes are not measured during nighttime, when water side convection normally is generated, periods of potential high gas flux might be missed and estimations of the total amount of gas released from lakes to the atmosphere will be biased.

  8. A review of nighttime eating disorders.

    PubMed

    Howell, Michael J; Schenck, Carlos H; Crow, Scott J

    2009-02-01

    Nighttime eating is categorized as either night eating syndrome (NES) or sleep-related eating disorder (SRED). These conditions represent an interruption in the overnight fast that characterizes human sleep. A critical review of the literature on NES and SRED will suggest that they are situated at opposite poles of a disordered eating spectrum. NES could be considered an abnormality in the circadian rhythm of meal timing with a normal circadian timing of sleep onset. Conversely, the feeding behavior in SRED is characterized by recurrent episodes of eating after an arousal from nighttime sleep with or without amnesia. Both conditions are often relentless and chronic. Multiple definitions of night eating have limited our ability to determine the exact prevalence of NES. Studies have suggested that central nervous system (CNS) serotonin modulation may lead to an effective treatment of NES. SRED is frequently associated with other sleep disorders, in particular parasomnias. Early studies have shown that the anti-seizure medication topiramate may be an effective treatment for SRED.

  9. Nighttime ionospheric D region: Equatorial and nonequatorial

    NASA Astrophysics Data System (ADS)

    Thomson, Neil R.; McRae, Wayne M.

    2009-08-01

    Nighttime ionospheric D region parameters are found to be generally well modeled by the traditional H‧ and β as used by Wait and by the U.S. Navy in their Earth-ionosphere VLF radio waveguide programs. New comparisons with nonequatorial, mainly all-sea VLF path observations reported over several decades are shown to be consistent with the previously determined height H‧ ˜ 85.0 km and sharpness β ˜ 0.63 km-1. These paths include NPM (Hawaii) to Washington, D. C., Omega Hawaii and NLK (Seattle) to Japan, NWC (N.W. Australia) to Madagascar, and NBA (Panama) to Colorado. In marked contrast, transequatorial path observations (even when nearly all-sea) are found to be often not well modeled: for example, for Omega Japan and JJI (Japan) to Dunedin, New Zealand, the observed amplitudes are markedly lower than those which would be expected from H‧ ˜ 85.0 km and β ˜ 0.63 km-1, or any other realistic values of H‧ and β. Other transequatorial observations compared with modeling include NWC to Japan, Omega Hawaii to Dunedin, and NPM (Hawaii) to Dunedin. It is suggested that the effects of irregularities in the equatorial electrojet may extend down into the nighttime D region and so account for the observed equatorial VLF perturbations through scattering or mode conversion.

  10. Perceptual evaluation of colorized nighttime imagery

    NASA Astrophysics Data System (ADS)

    Toet, Alexander; de Jong, Michael J.; Hogervorst, Maarten A.; Hooge, Ignace T. C.

    2014-02-01

    We recently presented a color transform that produces fused nighttime imagery with a realistic color appearance (Hogervorst and Toet, 2010, Information Fusion, 11-2, 69-77). To assess the practical value of this transform we performed two experiments in which we compared human scene recognition for monochrome intensified (II) and longwave infrared (IR) imagery, and color daylight (REF) and fused multispectral (CF) imagery. First we investigated the amount of detail observers can perceive in a short time span (the gist of the scene). Participants watched brief image presentations and provided a full report of what they had seen. Our results show that REF and CF imagery yielded the highest precision and recall measures, while both II and IR imagery yielded significantly lower values. This suggests that observers have more difficulty extracting information from monochrome than from color imagery. Next, we measured eye fixations of participants who freely explored the images. Although the overall fixation behavior was similar across image modalities, the order in which certain details were fixated varied. Persons and vehicles were typically fixated first in REF, CF and IR imagery, while they were fixated later in II imagery. In some cases, color remapping II imagery and fusion with IR imagery restored the fixation order of these image details. We conclude that color remapping can yield enhanced scene perception compared to conventional monochrome nighttime imagery, and may be deployed to tune multispectral image representation such that the resulting fixation behavior resembles the fixation behavior for daylight color imagery.

  11. Consistent allometric scaling of stomatal sizes and densities across taxonomic ranks and geologic time

    NASA Astrophysics Data System (ADS)

    de Boer, H. J.; Price, C. A.; Wagner-Cremer, F.; Dekker, S. C.; Veneklaas, E. J.

    2013-12-01

    Stomatal pores on plants leaves are an important link in the chain of processes that determine biosphere fluxes of water and carbon. Stomatal density (i.e. the number of stomata per area) and the size of the stomatal pore at maximum aperture are particularly relevant traits in this context because they determine the theoretical maximum diffusive stomatal conductance (gsmax) and thereby set an upper limit for leaf gas exchange. Observations on (sub)fossil leaves revealed that changes in stomatal densities are anti-correlated with changes in stomatal sizes at developmental and evolutionary timescales. Moreover, this anti-correlation appears consistently within single species, across multiple species in the extant plant community and at evolutionary time scales. The consistency of the relation between stomatal densities and sizes suggests that common mechanisms constrain the adaptation of these traits across the plant community. In an attempt to identify such potential generic constraints, we investigated the allometry between stomatal densities and sizes in the extant plant community and across geological time. As the size of the stomatal pore at maximum aperture is typically derived from the length of the stomatal pore, we considered the allometric scaling of pore length (lp) with stomatal density (Ds) as the power law: lp = k . Dsa in which k is a normalization constant and the exponent a is the slope of the scaling relation. Our null-hypothesis predicts that stomatal density and pore length scale along a constant slope of -1/2 based on a scale-invariant relation between pore length and the distance between neighboring pores. Our alternative hypothesis predicts a constant slope of -1 based on the idea that stomatal density and pore length scale along an invariant gsmax. To explore these scaling hypotheses in the extant plant community we compiled a dataset of combined observations of stomatal density and pore length on 111 species from published literature and new

  12. Satellite instrument provides nighttime sensing capability

    NASA Astrophysics Data System (ADS)

    Showstack, Randy

    2012-12-01

    "This is not your father's low-light sensor," Steve Miller, senior research scientist and deputy director of the Cooperative Institute for Research in the Atmosphere at Colorado State University, Fort Collins, said at a 5 December news briefing at the AGU Fall Meeting. He and others at the briefing were showing off the nighttime sensing capability of the day/night band of the Visible Infrared Imaging Radiometer Suite (VIIRS) of instruments onboard the Suomi National Polar-orbiting Partnership (NPP) Earth-observing research satellite, a joint NASA and National Oceanic and Atmospheric Administration (NOAA) satellite that was launched on 28 October 2011. Noting that low-light satellite technology has been available for about 40 years, Miller said that the VIIRS day/night band "is truly a paradigm shift in the technology and capability."

  13. [Denture stomatitis - definition, etiology, classification and treatment].

    PubMed

    Cubera, Katarzyna

    2013-01-01

    Denture stomatitis pertains to a number of pathological symptoms in the oral cavity caused by wearing acrylic dentures. Etiological factors include: mucosal trauma, fungal infection and accumulation of denture plaque. All of these factors appear to increase the ability of Candida albicans to colonize both the denture and oral mucosal surfaces. Antifungal treatment can eradicate C. albicans contamination and relieve stomatitis symptoms. Early diagnosis of the lesion is essential to assure rational therapy.

  14. Prototype active scanner for nighttime oil spill mapping and classification

    NASA Technical Reports Server (NTRS)

    Sandness, G. A.; Ailes, S. B.

    1977-01-01

    A prototype, active, aerial scanner system was constructed for nighttime water pollution detection and nighttime multispectral imaging of the ground. An arc lamp was used to produce the transmitted light and four detector channels provided a multispectral measurement capability. The feasibility of the design concept was demonstrated by laboratory and flight tests of the prototype system.

  15. Expression of Arabidopsis Hexokinase in Citrus Guard Cells Controls Stomatal Aperture and Reduces Transpiration.

    PubMed

    Lugassi, Nitsan; Kelly, Gilor; Fidel, Lena; Yaniv, Yossi; Attia, Ziv; Levi, Asher; Alchanatis, Victor; Moshelion, Menachem; Raveh, Eran; Carmi, Nir; Granot, David

    2015-01-01

    Hexokinase (HXK) is a sugar-phosphorylating enzyme involved in sugar-sensing. It has recently been shown that HXK in guard cells mediates stomatal closure and coordinates photosynthesis with transpiration in the annual species tomato and Arabidopsis. To examine the role of HXK in the control of the stomatal movement of perennial plants, we generated citrus plants that express Arabidopsis HXK1 (AtHXK1) under KST1, a guard cell-specific promoter. The expression of KST1 in the guard cells of citrus plants has been verified using GFP as a reporter gene. The expression of AtHXK1 in the guard cells of citrus reduced stomatal conductance and transpiration with no negative effect on the rate of photosynthesis, leading to increased water-use efficiency. The effects of light intensity and humidity on stomatal behavior were examined in rooted leaves of the citrus plants. The optimal intensity of photosynthetically active radiation and lower humidity enhanced stomatal closure of AtHXK1-expressing leaves, supporting the role of sugar in the regulation of citrus stomata. These results suggest that HXK coordinates photosynthesis and transpiration and stimulates stomatal closure not only in annual species, but also in perennial species. PMID:26734024

  16. Expression of Arabidopsis Hexokinase in Citrus Guard Cells Controls Stomatal Aperture and Reduces Transpiration.

    PubMed

    Lugassi, Nitsan; Kelly, Gilor; Fidel, Lena; Yaniv, Yossi; Attia, Ziv; Levi, Asher; Alchanatis, Victor; Moshelion, Menachem; Raveh, Eran; Carmi, Nir; Granot, David

    2015-01-01

    Hexokinase (HXK) is a sugar-phosphorylating enzyme involved in sugar-sensing. It has recently been shown that HXK in guard cells mediates stomatal closure and coordinates photosynthesis with transpiration in the annual species tomato and Arabidopsis. To examine the role of HXK in the control of the stomatal movement of perennial plants, we generated citrus plants that express Arabidopsis HXK1 (AtHXK1) under KST1, a guard cell-specific promoter. The expression of KST1 in the guard cells of citrus plants has been verified using GFP as a reporter gene. The expression of AtHXK1 in the guard cells of citrus reduced stomatal conductance and transpiration with no negative effect on the rate of photosynthesis, leading to increased water-use efficiency. The effects of light intensity and humidity on stomatal behavior were examined in rooted leaves of the citrus plants. The optimal intensity of photosynthetically active radiation and lower humidity enhanced stomatal closure of AtHXK1-expressing leaves, supporting the role of sugar in the regulation of citrus stomata. These results suggest that HXK coordinates photosynthesis and transpiration and stimulates stomatal closure not only in annual species, but also in perennial species.

  17. Stomatal Size, Speed, and Responsiveness Impact on Photosynthesis and Water Use Efficiency1[C

    PubMed Central

    Lawson, Tracy; Blatt, Michael R.

    2014-01-01

    The control of gaseous exchange between the leaf and bulk atmosphere by stomata governs CO2 uptake for photosynthesis and transpiration, determining plant productivity and water use efficiency. The balance between these two processes depends on stomatal responses to environmental and internal cues and the synchrony of stomatal behavior relative to mesophyll demands for CO2. Here we examine the rapidity of stomatal responses with attention to their relationship to photosynthetic CO2 uptake and the consequences for water use. We discuss the influence of anatomical characteristics on the velocity of changes in stomatal conductance and explore the potential for manipulating the physical as well as physiological characteristics of stomatal guard cells in order to accelerate stomatal movements in synchrony with mesophyll CO2 demand and to improve water use efficiency without substantial cost to photosynthetic carbon fixation. We conclude that manipulating guard cell transport and metabolism is just as, if not more likely to yield useful benefits as manipulations of their physical and anatomical characteristics. Achieving these benefits should be greatly facilitated by quantitative systems analysis that connects directly the molecular properties of the guard cells to their function in the field. PMID:24578506

  18. Expression of Arabidopsis Hexokinase in Citrus Guard Cells Controls Stomatal Aperture and Reduces Transpiration

    PubMed Central

    Lugassi, Nitsan; Kelly, Gilor; Fidel, Lena; Yaniv, Yossi; Attia, Ziv; Levi, Asher; Alchanatis, Victor; Moshelion, Menachem; Raveh, Eran; Carmi, Nir; Granot, David

    2015-01-01

    Hexokinase (HXK) is a sugar-phosphorylating enzyme involved in sugar-sensing. It has recently been shown that HXK in guard cells mediates stomatal closure and coordinates photosynthesis with transpiration in the annual species tomato and Arabidopsis. To examine the role of HXK in the control of the stomatal movement of perennial plants, we generated citrus plants that express Arabidopsis HXK1 (AtHXK1) under KST1, a guard cell-specific promoter. The expression of KST1 in the guard cells of citrus plants has been verified using GFP as a reporter gene. The expression of AtHXK1 in the guard cells of citrus reduced stomatal conductance and transpiration with no negative effect on the rate of photosynthesis, leading to increased water-use efficiency. The effects of light intensity and humidity on stomatal behavior were examined in rooted leaves of the citrus plants. The optimal intensity of photosynthetically active radiation and lower humidity enhanced stomatal closure of AtHXK1-expressing leaves, supporting the role of sugar in the regulation of citrus stomata. These results suggest that HXK coordinates photosynthesis and transpiration and stimulates stomatal closure not only in annual species, but also in perennial species. PMID:26734024

  19. Carbon dioxide effects on stomatal responses to the environment and water use by crops under field conditions.

    PubMed

    Bunce, James A

    2004-06-01

    Reductions in leaf stomatal conductance with rising atmospheric carbon dioxide concentration ([CO2]) could reduce water use by vegetation and potentially alter climate. Crop plants have among the largest reductions in stomatal conductance at elevated [CO2]. The relative reduction in stomatal conductance caused by a given increase in [CO2] is often not constant within a day nor between days, but may vary considerably with light, temperature and humidity. Species also differ in response, with a doubling of [CO2] reducing mean midday conductances by <15% in some crop species to >50% in others. Elevated [CO2] increases leaf area index throughout the growing season in some species. Simulations, and measurements in free air carbon dioxide enrichment systems both indicate that the relatively large reductions in stomatal conductance in crops would translate into reductions of <10% in evapotranspiration, partly because of increases in temperature and decreases in humidity in the air around crop leaves. The reduction in evapotranspiration in crops is similar to that in other types of vegetation which have smaller relative reductions in stomatal conductance, because of the poorer aerodynamic coupling of the canopy to the atmosphere in crops. The small decreases in evapotranspiration at elevated [CO2] may themselves be important to crop production in dry environments, but changes in climate and microclimate caused by reduced stomatal conductance could also be important to crop production. PMID:14557864

  20. Direct observation of reversible and irreversible stomatal responses of attached sunflower leaves to SO/sub 2/

    SciTech Connect

    Omasa, K.; Hashimoto, Y.; Kramer, P.J.; Strain, B.R.; Aiga, I.; Kondo, J.

    1985-09-01

    The effects of SO/sub 2/ on stomatal aperture of attached sunflower leaves were observed with a remote-control light microscope system that permitted continuous observation of stomatal responses over periods of several hours. The relationship between actual stomatal aperture and stomatal conductance, measured with a porometer, also was examined on leaves before and after exposure to SO/sub 2/. A distinction between uninjured and injured regions was clearly visible on leaves after exposure to 1.5 microliters per liter SO/sub 2/ for less than an hour. During the exposure, the mean value of apertures for many stomata, which indicates stomatal conductance and transpiration rate, tended to decrease simultaneously in the uninjured and injured regions. There was a good correlation between pore width and stomatal conductance measured with a porometer before exposure to SO/sub 2/. This correlation continued in leaves exposed to SO/sub 2/ until visible, irreversible injury occurred, but then it disappeared. The results of these experiments indicate the necessity of continuous observation of individual stomata under the microscope to understand the effects of air pollutants such as SO/sub 2/ on stomatal behavior.

  1. Nonstomatal versus stomatal uptake of atmospheric mercury.

    PubMed

    Stamenkovic, Jelena; Gustin, Mae S

    2009-03-01

    Atmospheric constituents may be deposited to and incorporated into plant leaves, with gases entering via stomata, and gas and particles being sorbed at the surface and in some cases traversing the cuticle, possibly reaching the epidermis. Plants are known to be a sink for atmospheric mercury (Hg), and the current paradigm is that uptake of gaseous elemental Hg occurs by way of the stomata. Four plant species, Rudbeckia hirta, Sorghastrum nutans, Andropogon gerardii, and Populus tremuloides, were exposed to air from different sources and with different Hg and CO2 concentrations in light and dark within a gas exchange chamber at approximately 25% relative humidity. Data showed that Hg concentration and air source had a significant effect (p < 0.001) on leaf-atmosphere Hg flux, with more deposition to the leaf occurring in elevated-Hg air, and in scrubbed air compared to ambient air. Deposition also occurred during dark and elevated CO2 exposures, when stomatal conductance was reduced. These observations and the fact that limited or no Hg emission occurred after deposition of atmospheric Hg suggests that the nonstomatal pathway may be an important route of foliar accumulation of atmospheric Hg.

  2. The stomatal CO2 proxy does not saturate at high atmospheric CO2 concentrations: evidence from stomatal index responses of Araucariaceae conifers.

    PubMed

    Haworth, Matthew; Elliott-Kingston, Caroline; McElwain, Jennifer C

    2011-09-01

    The inverse relationship between the number of stomata on a leaf surface and the atmospheric carbon dioxide concentration ([CO(2)]) in which the leaf developed allows plants to optimise water-use efficiency (WUE), but it also permits the use of fossil plants as proxies of palaeoatmospheric [CO(2)]. The ancient conifer family Araucariaceae is often represented in fossil floras and may act as a suitable proxy of palaeo-[CO(2)], yet little is known regarding the stomatal index (SI) responses of extant Araucariaceae to [CO(2)]. Four Araucaria species (Araucaria columnaris, A. heterophylla, A. angustifolia and A. bidwillii) and Agathis australis displayed no significant relationship in SI to [CO(2)] below current ambient levels (~380 ppm). However, representatives of the three extant genera within the Araucariaceae (A. bidwillii, A. australis and Wollemia nobilis) all exhibited significant reductions in SI when grown in atmospheres of elevated [CO(2)] (1,500 ppm). Stomatal conductance was reduced and WUE increased when grown under elevated [CO(2)]. Stomatal pore length did not increase alongside reduced stomatal density (SD) and SI in the three araucariacean conifers when grown at elevated [CO(2)]. These pronounced SD and SI reductions occur at higher [CO(2)] levels than in other species with more recent evolutionary origins, and may reflect an evolutionary legacy of the Araucariaceae in the high [CO(2)] world of the Mesozoic Era. Araucariacean conifers may therefore be suitable stomatal proxies of palaeo-[CO(2)] during periods of "greenhouse" climates and high [CO(2)] in the Earth's history.

  3. Stomatal Responses to Light and Leaf-Air Water Vapor Pressure Difference Show Similar Kinetics in Sugarcane and Soybean 1

    PubMed Central

    Grantz, David A.; Zeiger, Eduardo

    1986-01-01

    Stomatal responses to light and humidity (vapor pressure difference, VPD) are important determinants of stomatal conductance. Stomatal movements induced by light are the result of a transduction of the light stimulus into modulated ion fluxes in guard cells and concomitant osmotic adjustments and turgor changes. It is generally assumed that this transduction process is a general stomatal property, with different environmental stimuli integrated into guard cell metabolism through their modulation of ion fluxes. In contrast with this notion, the VPD response, which is unique because both its triggering signal and the turgor changes required for aperture modulations involve water molecules, has been considered to be hydropassive and thus independent of guard cell metabolism. We used a kinetic approach to compare the light and VPD responses in order to test the hypothesis that hydropassive changes in guard cell turgor could be faster than the metabolism-dependent light responses. Changes in stomatal conductance in intact leaves of sugarcane and soybean were measured after application of step changes in VPD and in light. In spite of a 5-fold difference in overall rates between the two species, the response rates following light or VPD steps were similar. Although a coincidental kinetic similarity between two mechanistically different responses cannot be ruled out, the data suggest a common mechanism controlling stomatal movements, with the VPD stimulus inducing metabolic modulations of ion fluxes analogous to other stomatal responses. PMID:16664916

  4. Relationships between stomatal behavior, xylem vulnerability to cavitation and leaf water relations in two cultivars of Vitis vinifera.

    PubMed

    Tombesi, Sergio; Nardini, Andrea; Farinelli, Daniela; Palliotti, Alberto

    2014-11-01

    Current understanding of physiological mechanisms governing stomatal behavior under water stress conditions is still incomplete and controversial. It has been proposed that coordination of stomatal kinetics with xylem vulnerability to cavitation [vulnerability curve (VC)] leads to different levels of isohydry/anisohydry in different plant species/cultivars. In this study, this hypothesis is tested in Vitis vinifera cultivars displaying contrasting stomatal behavior under drought stress. The cv Montepulciano (MP, near-isohydric) and Sangiovese (SG, anisohydric) were compared in terms of stomatal response to leaf and stem water potential, as possibly correlated to different petiole hydraulic conductivity (k(petiole)) and VC, as well as to leaf water relations parameters. MP leaves showed almost complete stomatal closure at higher leaf and stem water potentials than SG leaves. Moreover, MP petioles had higher maximum k(petiole) and were more vulnerable to cavitation than SG. Water potential at the turgor loss point was higher in MP than in SG. In SG, the percentage reduction of stomatal conductance (PLg(s)) under water stress was almost linearly correlated with corresponding percentage loss of k(petiole) (PLC), while in MP PLg(s) was less influenced by PLC. Our results suggest that V. vinifera near-isohydric and anisohydric genotypes differ in terms of xylem vulnerability to cavitation as well as in terms of k(petiole) and that the coordination of these traits leads to their different stomatal responses under water stress conditions.

  5. Pre-dawn stomatal opening does not substantially enhance early-morning photosynthesis in Helianthus annuus.

    PubMed

    Auchincloss, Lisa; Easlon, Hsien M; Levine, Diedre; Donovan, Lisa; Richards, James H

    2014-06-01

    Most C3 plant species have partially open stomata during the night especially in the 3-5 h before dawn. This pre-dawn stomatal opening has been hypothesized to enhance early-morning photosynthesis (A) by reducing diffusion limitations to CO2 at dawn. We tested this hypothesis in cultivated Helianthus annuus using whole-shoot gas exchange, leaf level gas exchange and modelling approaches. One hour pre-dawn low-humidity treatments were used to reduce pre-dawn stomatal conductance (g). At the whole-shoot level, a difference of pre-dawn g (0.40 versus 0.17 mol m(-2) s(-1)) did not significantly affect A during the first hour after dawn. Shorter term effects were investigated with leaf level gas exchange measurements and a difference of pre-dawn g (0.10 versus 0.04 mol m(-2) s(-1)) affected g and A for only 5 min after dawn. The potential effects of a wider range of stomatal apertures were explored with an empirical model of the relationship between A and intercellular CO2 concentration during the half-hour after dawn. Modelling results demonstrated that even extremely low pre-dawn stomatal conductance values have only a minimal effect on early-morning A for a few minutes after dawn. Thus, we found no evidence that pre-dawn stomatal opening enhances A.

  6. Stomatal plugs of Drimys winteri (Winteraceae) protect leaves from mist but not drought

    PubMed Central

    Feild, Taylor S.; Zwieniecki, Maciej A.; Donoghue, Michael J.; Holbrook, N. Michele

    1998-01-01

    Two outstanding features of the flowering plant family Winteraceae are the occlusion of their stomatal pores by cutin plugs and the absence of water-conducting xylem vessels. An adaptive relationship between these two unusual features has been suggested whereby stomatal plugs restrict gas exchange to compensate for the presumed poor conductivity of their vesselless wood. This hypothesized connection fueled evolutionary arguments that the vesselless condition is ancestral in angiosperms. Here we show that in Drimys winteri, a tree common to wet forests, these stomatal occlusions pose only a small fixed resistance to water loss. In addition, they modify the humidity response of guard cells such that under high evaporative demand, leaves with plugs lose water at a faster rate than leaves from which the plugs have been experimentally removed. Instead of being adaptations for drought, we present evidence that these cuticular structures function to maintain photosynthetic activity under conditions of excess water on the leaf surface. Stomatal plugs decrease leaf wettability by preventing the formation of a continuous water film that would impede diffusion of CO2 into the leaf. Misting of leaves had no effect on photosynthetic rate of leaves with plugs, but resulted in a marked decrease (≈40%) in leaves from which the plugs had been removed. These findings do not support a functional association between stomatal plugs and hydraulic competence and provide a new perspective on debates surrounding the evolution of vessels in angiosperms. PMID:9826687

  7. Clinical study on thermography, as modern investigation method for Candida-associated denture stomatitis.

    PubMed

    Iosif, Laura; Preoteasa, Cristina Teodora; Murariu-Măgureanu, Cătălina; Preoteasa, Elena

    2016-01-01

    Candida-associated denture stomatitis is an infectious inflammatory condition of the oral mucosa, with frequent recurrences. The aim of this study was to assess the use of infrared thermography as investigation method for Candida-associated denture stomatitis (as inflammatory disorder of the maxillary denture bearing area), by comparing disease and non-disease groups. An observational study was conducted on maxillary edentulous patients treated by acrylic dentures, with and without Candida-associated denture stomatitis. Diagnostic test methods used were clinical examination for denture stomatitis and conventional microbiological culture method for oral candidiasis. Thermography analysis of the maxillary denture bearing area was made using the ThermaCAM PM350 infrared camera (Inframetrics, Flir Systems) and ThermaGram Pro 95 software, data being acquired by usage of standard protocol of thermographic registrations. The sample included 52 patients, 21 with and 31 without Candida-associated denture stomatitis. The temperature of the maxillary mucosa corresponding to the denture bearing area was found to be statistically significantly higher in Candida-associated denture stomatitis (mean 36.20°C), compared to healthy oral mucosa (mean 34.85°C). The thermal threshold value of 35.44°C was identified as best differentiating a pathological from normal state of the maxillary mucosa corresponding to the denture bearing area. In conclusion, infrared thermography, a rapid non-invasive investigation method, has the premises to bring valuable data in inflammatory disorders of the maxillary denture bearing area, as Candida-associated denture stomatitis that may be used for screening, diagnostic or monitoring purposes.

  8. Nighttime lights and population changes in Europe 1992-2012.

    PubMed

    Archila Bustos, Maria Francisca; Hall, Ola; Andersson, Magnus

    2015-11-01

    Nighttime satellite photographs of Earth reveal the location of lighting and provide a unique view of the extent of human settlement. Nighttime lights have been shown to correlate with economic development and population but little research has been done on the link between nighttime lights and population change over time. We explore whether population decline is coupled with decline in lighted area and how the age structure of the population and GDP are reflected in nighttime lights. We examine Europe between the period of 1992 and 2012 using a Geographic Information System and regression analysis. The results suggest that population decline is not coupled with decline in lighted area. Instead, human settlement extent is more closely related to the age structure of the population and to GDP. We conclude that declining populations will not necessarily lead to reductions in the extent of land development.

  9. Analysis of Temperature Distributions in Nighttime Inversions

    NASA Astrophysics Data System (ADS)

    Telyak, Oksana; Krasouski, Aliaksandr; Svetashev, Alexander; Turishev, Leonid; Barodka, Siarhei

    2015-04-01

    Adequate prediction of temperature inversion in the atmospheric boundary layer is one of prerequisites for successful forecasting of meteorological parameters and severe weather events. Examples include surface air temperature and precipitation forecasting as well as prediction of fog, frosts and smog with hazardous levels of atmospheric pollution. At the same time, reliable forecasting of temperature inversions remains an unsolved problem. For prediction of nighttime inversions over some specific territory, it is important to study characteristic features of local circulation cells formation and to properly take local factors into account to develop custom modeling techniques for operational use. The present study aims to investigate and analyze vertical temperature distributions in tropospheric inversions (isotherms) over the territory of Belarus. We study several specific cases of formation, evolution and decay of deep nighttime temperature inversions in Belarus by means of mesoscale numerical simulations with WRF model, considering basic mechanisms of isothermal and inverse temperature layers formation in the troposphere and impact of these layers on local circulation cells. Our primary goal is to assess the feasibility of advance prediction of inversions formation with WRF. Modeling results reveal that all cases under consideration have characteristic features of radiative inversions (e.g., their formation times, development phases, inversion intensities, etc). Regions of "blocking" layers formation are extensive and often spread over the entire territory of Belarus. Inversions decay starts from the lowermost (near surface) layer (altitudes of 5 to 50 m). In all cases, one can observe formation of temperature gradients that substantially differ from the basic inversion gradient, i.e. the layer splits into smaller layers, each having a different temperature stratification (isothermal, adiabatic, etc). As opposed to various empirical techniques as well as

  10. Moonlight DOAS for nighttime studies of volcanic plumes

    NASA Astrophysics Data System (ADS)

    Zielcke, Johannes; Bobrowski, Nicole; Vogel, Leif; Kern, Christoph; Platt, Ulrich

    2010-05-01

    Differential Optical Absorption Spectroscopy (DOAS) in the ultraviolet and visible wavelength region has become a widespread tool not only to study the chemistry of trace gases such as sulphur dioxide (SO2) and halogen oxides (e.g. BrO, ClO, OClO) in volcanic plumes, but also for volcano monitoring by observing SO2 fluxes. During daylight hours either direct or scattered sunlight can be used for measurements. At night other light sources have to be used, the two main possibilities being artificial ones and the moon. While artificial lighting has several important advantages, such as otherwise not available wavelength regions (e.g. deep UV) and a known light path, it is limited to measurements at the crater rim in most circumstances in volcanic environments, which is a potentially dangerous place, and limits the investigation of plume chemistry to the nearer source region. To study the composition of the plume further downwind at night, the moon is the only available source of light. Within the NOVAC (Network for Volcanic and Atmospheric Change) project, passive scanning DOAS instruments in the UV wavelength region were developed and deployed at several degassing volcanoes. We adapted these instruments, however, to track the moon and thus to conduct direct light measurements. As the speciation of bromine and other halogenic oxides relies on photodissociation of their respective elementary molecules, a discrepancy between day and nighttime chemistry is expected. While emissions during the day have been studied for some time now, little is known about the reactions occuring at night. We present direct moonlight measurements carried out at Mount Etna during November/December 2009. SO2 slant column densities (SCD) of up to 2 × 1018 molecules-cm2 were detected and spectra are analyzed for halogen compounds. The results are compared to direct sunlight measurements undertaken in the same period. Our maximum nighttime BrO-SO2 ratio is significantly lower than the ones

  11. The evolution of mechanisms driving the stomatal response to vapor pressure deficit.

    PubMed

    McAdam, Scott A M; Brodribb, Timothy J

    2015-03-01

    Stomatal responses to vapor pressure deficit (VPD) are a principal means by which vascular land plants regulate daytime transpiration. While much work has focused on characterizing and modeling this response, there remains no consensus as to the mechanism that drives it. Explanations range from passive regulation by leaf hydration to biochemical regulation by the phytohormone abscisic acid (ABA). We monitored ABA levels, leaf gas exchange, and water status in a diversity of vascular land plants exposed to a symmetrical, mild transition in VPD. The stomata in basal lineages of vascular plants, including gymnosperms, appeared to respond passively to changes in leaf water status induced by VPD perturbation, with minimal changes in foliar ABA levels and no hysteresis in stomatal action. In contrast, foliar ABA appeared to drive the stomatal response to VPD in our angiosperm samples. Increased foliar ABA level at high VPD in angiosperm species resulted in hysteresis in the recovery of stomatal conductance; this was most pronounced in herbaceous species. Increased levels of ABA in the leaf epidermis were found to originate from sites of synthesis in other parts of the leaf rather than from the guard cells themselves. The transition from a passive regulation to ABA regulation of the stomatal response to VPD in the earliest angiosperms is likely to have had critical implications for the ecological success of this lineage. PMID:25637454

  12. Stomatal acclimation to vapour pressure deficit doubles transpiration of small tree seedlings with warming.

    PubMed

    Marchin, Renée M; Broadhead, Alice A; Bostic, Laura E; Dunn, Robert R; Hoffmann, William A

    2016-10-01

    Future climate change is expected to increase temperature (T) and atmospheric vapour pressure deficit (VPD) in many regions, but the effect of persistent warming on plant stomatal behaviour is highly uncertain. We investigated the effect of experimental warming of 1.9-5.1 °C and increased VPD of 0.5-1.3 kPa on transpiration and stomatal conductance (gs ) of tree seedlings in the temperate forest understory (Duke Forest, North Carolina, USA). We observed peaked responses of transpiration to VPD in all seedlings, and the optimum VPD for transpiration (Dopt ) shifted proportionally with increasing chamber VPD. Warming increased mean water use of Carya by 140% and Quercus by 150%, but had no significant effect on water use of Acer. Increased water use of ring-porous species was attributed to (1) higher air T and (2) stomatal acclimation to VPD resulting in higher gs and more sensitive stomata, and thereby less efficient water use. Stomatal acclimation maintained homeostasis of leaf T and carbon gain despite increased VPD, revealing that short-term stomatal responses to VPD may not be representative of long-term exposure. Acclimation responses differ from expectations of decreasing gs with increasing VPD and may necessitate revision of current models based on this assumption.

  13. The Evolution of Mechanisms Driving the Stomatal Response to Vapor Pressure Deficit1[OPEN

    PubMed Central

    McAdam, Scott A.M.; Brodribb, Timothy J.

    2015-01-01

    Stomatal responses to vapor pressure deficit (VPD) are a principal means by which vascular land plants regulate daytime transpiration. While much work has focused on characterizing and modeling this response, there remains no consensus as to the mechanism that drives it. Explanations range from passive regulation by leaf hydration to biochemical regulation by the phytohormone abscisic acid (ABA). We monitored ABA levels, leaf gas exchange, and water status in a diversity of vascular land plants exposed to a symmetrical, mild transition in VPD. The stomata in basal lineages of vascular plants, including gymnosperms, appeared to respond passively to changes in leaf water status induced by VPD perturbation, with minimal changes in foliar ABA levels and no hysteresis in stomatal action. In contrast, foliar ABA appeared to drive the stomatal response to VPD in our angiosperm samples. Increased foliar ABA level at high VPD in angiosperm species resulted in hysteresis in the recovery of stomatal conductance; this was most pronounced in herbaceous species. Increased levels of ABA in the leaf epidermis were found to originate from sites of synthesis in other parts of the leaf rather than from the guard cells themselves. The transition from a passive regulation to ABA regulation of the stomatal response to VPD in the earliest angiosperms is likely to have had critical implications for the ecological success of this lineage. PMID:25637454

  14. The evolution of mechanisms driving the stomatal response to vapor pressure deficit.

    PubMed

    McAdam, Scott A M; Brodribb, Timothy J

    2015-03-01

    Stomatal responses to vapor pressure deficit (VPD) are a principal means by which vascular land plants regulate daytime transpiration. While much work has focused on characterizing and modeling this response, there remains no consensus as to the mechanism that drives it. Explanations range from passive regulation by leaf hydration to biochemical regulation by the phytohormone abscisic acid (ABA). We monitored ABA levels, leaf gas exchange, and water status in a diversity of vascular land plants exposed to a symmetrical, mild transition in VPD. The stomata in basal lineages of vascular plants, including gymnosperms, appeared to respond passively to changes in leaf water status induced by VPD perturbation, with minimal changes in foliar ABA levels and no hysteresis in stomatal action. In contrast, foliar ABA appeared to drive the stomatal response to VPD in our angiosperm samples. Increased foliar ABA level at high VPD in angiosperm species resulted in hysteresis in the recovery of stomatal conductance; this was most pronounced in herbaceous species. Increased levels of ABA in the leaf epidermis were found to originate from sites of synthesis in other parts of the leaf rather than from the guard cells themselves. The transition from a passive regulation to ABA regulation of the stomatal response to VPD in the earliest angiosperms is likely to have had critical implications for the ecological success of this lineage.

  15. Stomatal acclimation to vapour pressure deficit doubles transpiration of small tree seedlings with warming.

    PubMed

    Marchin, Renée M; Broadhead, Alice A; Bostic, Laura E; Dunn, Robert R; Hoffmann, William A

    2016-10-01

    Future climate change is expected to increase temperature (T) and atmospheric vapour pressure deficit (VPD) in many regions, but the effect of persistent warming on plant stomatal behaviour is highly uncertain. We investigated the effect of experimental warming of 1.9-5.1 °C and increased VPD of 0.5-1.3 kPa on transpiration and stomatal conductance (gs ) of tree seedlings in the temperate forest understory (Duke Forest, North Carolina, USA). We observed peaked responses of transpiration to VPD in all seedlings, and the optimum VPD for transpiration (Dopt ) shifted proportionally with increasing chamber VPD. Warming increased mean water use of Carya by 140% and Quercus by 150%, but had no significant effect on water use of Acer. Increased water use of ring-porous species was attributed to (1) higher air T and (2) stomatal acclimation to VPD resulting in higher gs and more sensitive stomata, and thereby less efficient water use. Stomatal acclimation maintained homeostasis of leaf T and carbon gain despite increased VPD, revealing that short-term stomatal responses to VPD may not be representative of long-term exposure. Acclimation responses differ from expectations of decreasing gs with increasing VPD and may necessitate revision of current models based on this assumption. PMID:27392307

  16. ABA signaling in stomatal guard cells: lessons from Commelina and Vicia.

    PubMed

    Mori, Izumi C; Murata, Yoshiyuki

    2011-07-01

    Abscisic acid (ABA) signaling mechanisms have been studied in a broad variety of plant species using complementary analyses, taking advantage of different methodologies suitable for each plant species. Early studies on ABA biosynthesis using Solanum lycopersicum mutants suggested an importance of ABA synthesis in stomatal closure. To understand ABA signaling in guard cells, cellular, biochemical and electrophysiological studies in Vicia faba and Commelina communis have been conducted, providing fundamental knowledge that was further reconfirmed by molecular genetic studies of Arabidopsis. In this article, examples of stomatal studies in several plants and prospects in ABA research are discussed.

  17. Responses of Hawaiian plants to volcanic sulfur dioxide: stomatal behavior and foliar injury

    SciTech Connect

    Not Available

    1980-11-14

    Hawaiian plants exposed to volcanic sulfur dioxide showed interspecific differences in leaf injury that are related to sulfur dioxide-induced changes in stomatal conductance. Species with leaves that did not close stomata developed either chlorosis or necrosis, whereas leaves of Metrosideros collina closed stomata and showed no visual symptoms of sulfur dioxide stress.

  18. Gaseous NO2 effects on stomatal behavior, photosynthesis and respiration of hybrid poplar leaves

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In this study, we used poplar as a model plant and investigated the effects of gaseous nitrogen dioxide (NO2, 4 microliter per liter) on stomatal conductance, photosynthesis, dark- and photorespiration of Populus alba x Populus berolinensis hybrid leaves using the photosynthesis system and scanning...

  19. Ozone risk assessment for agricultural crops in Europe: Further development of stomatal flux and flux-response relationships for European wheat and potato

    NASA Astrophysics Data System (ADS)

    Pleijel, H.; Danielsson, H.; Emberson, L.; Ashmore, M. R.; Mills, G.

    Applications of a parameterised Jarvis-type multiplicative stomatal conductance model with data collated from open-top chamber experiments on field grown wheat and potato were used to derive relationships between relative yield and stomatal ozone uptake. The relationships were based on thirteen experiments from four European countries for wheat and seven experiments from four European countries for potato. The parameterisation of the conductance model was based both on an extensive literature review and primary data. Application of the stomatal conductance models to the open-top chamber experiments resulted in improved linear regressions between relative yield and ozone uptake compared to earlier stomatal conductance models, both for wheat ( r2=0.83) and potato ( r2=0.76). The improvement was largest for potato. The relationships with the highest correlation were obtained using a stomatal ozone flux threshold. For both wheat and potato the best performing exposure index was AF st6 (accumulated stomatal flux of ozone above a flux rate threshold of 6 nmol ozone m -2 projected sunlit leaf area, based on hourly values of ozone flux). The results demonstrate that flux-based models are now sufficiently well calibrated to be used with confidence to predict the effects of ozone on yield loss of major arable crops across Europe. Further studies, using innovations in stomatal conductance modelling and plant exposure experimentation, are needed if these models are to be further improved.

  20. Most stomatal closure in woody species under moderate drought can be explained by stomatal responses to leaf turgor.

    PubMed

    Rodriguez-Dominguez, Celia M; Buckley, Thomas N; Egea, Gregorio; de Cires, Alfonso; Hernandez-Santana, Virginia; Martorell, Sebastia; Diaz-Espejo, Antonio

    2016-09-01

    Reduced stomatal conductance (gs ) during soil drought in angiosperms may result from effects of leaf turgor on stomata and/or factors that do not directly depend on leaf turgor, including root-derived abscisic acid (ABA) signals. To quantify the roles of leaf turgor-mediated and leaf turgor-independent mechanisms in gs decline during drought, we measured drought responses of gs and water relations in three woody species (almond, grapevine and olive) under a range of conditions designed to generate independent variation in leaf and root turgor, including diurnal variation in evaporative demand and changes in plant hydraulic conductance and leaf osmotic pressure. We then applied these data to a process-based gs model and used a novel method to partition observed declines in gs during drought into contributions from each parameter in the model. Soil drought reduced gs by 63-84% across species, and the model reproduced these changes well (r(2)  = 0.91, P < 0.0001, n = 44) despite having only a single fitted parameter. Our analysis concluded that responses mediated by leaf turgor could explain over 87% of the observed decline in gs across species, adding to a growing body of evidence that challenges the root ABA-centric model of stomatal responses to drought.

  1. Most stomatal closure in woody species under moderate drought can be explained by stomatal responses to leaf turgor.

    PubMed

    Rodriguez-Dominguez, Celia M; Buckley, Thomas N; Egea, Gregorio; de Cires, Alfonso; Hernandez-Santana, Virginia; Martorell, Sebastia; Diaz-Espejo, Antonio

    2016-09-01

    Reduced stomatal conductance (gs ) during soil drought in angiosperms may result from effects of leaf turgor on stomata and/or factors that do not directly depend on leaf turgor, including root-derived abscisic acid (ABA) signals. To quantify the roles of leaf turgor-mediated and leaf turgor-independent mechanisms in gs decline during drought, we measured drought responses of gs and water relations in three woody species (almond, grapevine and olive) under a range of conditions designed to generate independent variation in leaf and root turgor, including diurnal variation in evaporative demand and changes in plant hydraulic conductance and leaf osmotic pressure. We then applied these data to a process-based gs model and used a novel method to partition observed declines in gs during drought into contributions from each parameter in the model. Soil drought reduced gs by 63-84% across species, and the model reproduced these changes well (r(2)  = 0.91, P < 0.0001, n = 44) despite having only a single fitted parameter. Our analysis concluded that responses mediated by leaf turgor could explain over 87% of the observed decline in gs across species, adding to a growing body of evidence that challenges the root ABA-centric model of stomatal responses to drought. PMID:27255698

  2. Magnitude of nighttime transpiration does not affect plant growth or nutrition in well-watered Arabidopsis.

    PubMed

    Christman, Mairgareth A; Donovan, Lisa A; Richards, James H

    2009-07-01

    Significant water loss occurs throughout the night via partially open stomata in many C(3) and C(4) plant species. Although apparently wasteful in terms of water use, nighttime transpiration (E(night)) is hypothesized to benefit plants by enhancing nutrient supply. We tested the hypothesis that plants with greater E(night) would have improved plant nutrient status and greater fitness, estimated as pre-bolting biomass, for Arabidopsis thaliana. Two very different levels of E(night) were generated in plants by exposing them to high vs low nighttime leaf-to-air vapor pressure deficits (VPD(leaf)) in controlled environment chambers. An assessment of responses of nighttime leaf conductance (g(night)) to VPD(leaf) indicated that E(night) differed by at least 80% between the treatments. This large difference in E(night), imposed over the entire vegetative growth phase of Arabidopsis, had no effect on leaf nutrient content (N, Ca, K) or pre-bolting rosette biomass. The lack of response to differences in E(night) held true for both a high and a low nitrogen (N) treatment, even though the low N treatment decreased leaf N and biomass by 40-60%. The N treatment had no effect on g(night). Thus, higher E(night) did not provide a nutrient or growth benefit to Arabidopsis, even when the plants were N-limited.

  3. The magnitude of the stomatal response to blue light : modulation by atmospheric humidity.

    PubMed

    Assmann, S M; Grantz, D A

    1990-06-01

    The effect of leaf-air vapor pressure difference (VPD) on the magnitude of the stomatal response to blue light was investigated in soybean (Glycine max) by administering blue light pulses (22 seconds by 120 micromoles per square meter per second) at different levels of VPD and temperature. At 20 degrees C and 25 degrees C, the magnitude of the integrated conductance response decreased with increasing VPD (0.4 to 2.6 kiloPascals), due to an earlier onset of stomatal closure that terminated the pulse response. In contrast, at 30 degrees C this magnitude increased with rising VPD (0.9 to 3.5 kiloPascals), due to an increasing maximum excursion of the conductance response despite the accelerated onset of stomatal closure. When the feedforward response of stomata to humidity caused steady state transpiration to decrease with increasing VPD, the magnitude of the pulse-induced conductance response correlated with VPD rather than with transpiration. This suggests that water relations or metabolite movements within epidermal rather than bulk leaf tissue interacted with guard cell photobiological properties in regulating the magnitude of the blue light response. VPD modulation of pulse magnitude could reduce water loss during stomatal responses to transient illumination in natural light environments. PMID:16667526

  4. Stomatal Closure and Photosynthetic Inhibition in Soybean Leaves Induced by Petiole Girdling and Pod Removal 1

    PubMed Central

    Setter, Tim L.; Brun, William A.; Brenner, Mark L.

    1980-01-01

    The presence of strong sinks of photoassimilates is thought to stimulate photosynthesis by minimizing photosynthetic end product accumulation in leaves. This hypothesis was examined in soybeans (Glycine max [L] Merr.) with treatments designed to alter the phloem translocation of photoassimilates out of source leaves. Pod removal and petiole girdling resulted in 70 and 90% reductions, respectively, in leaf CO2 exchange rate. Reductions of similar magnitude also were observed in stomatal diffusive conductivity. Time course data showed that CO2 exchange rates as well as stomatal conductivities were significantly reduced 0.5 hour after girdling and 5 hours after pod removal, thus suggesting that stomatal closure was the cause of the reduced rates of photosynthesis. Mesophyll conductivities to CO2, calculated from gas exchange data, were not affected by the treatments. Radiocarbon assimilation rates by leaf slices floated in KH14CO3 solutions were not reduced by pod removal and were reduced only 10% by girdling. It was concluded that treatments which block or slow translocation from source leaves reduce their photosynthetic rate by inducing stomatal closure. PMID:16661301

  5. The health impact of nighttime eating: old and new perspectives.

    PubMed

    Kinsey, Amber W; Ormsbee, Michael J

    2015-04-09

    Nighttime eating, particularly before bed, has received considerable attention. Limiting and/or avoiding food before nighttime sleep has been proposed as both a weight loss strategy and approach to improve health and body composition. Indeed, negative outcomes have been demonstrated in response to large mixed meals in populations that consume a majority of their daily food intake during the night. However, data is beginning to mount to suggest that negative outcomes may not be consistent when the food choice is small, nutrient-dense, low energy foods and/or single macronutrients rather than large mixed-meals. From this perspective, it appears that a bedtime supply of nutrients can promote positive physiological changes in healthy populations. In addition, when nighttime feeding is combined with exercise training, any adverse effects appear to be eliminated in obese populations. Lastly, in Type I diabetics and those with glycogen storage disease, eating before bed is essential for survival. Nevertheless, nighttime consumption of small (~150 kcals) single nutrients or mixed-meals does not appear to be harmful and may be beneficial for muscle protein synthesis and cardiometabolic health. Future research is warranted to elucidate potential applications of nighttime feeding alone and in combination with exercise in various populations of health and disease.

  6. The health impact of nighttime eating: old and new perspectives.

    PubMed

    Kinsey, Amber W; Ormsbee, Michael J

    2015-04-01

    Nighttime eating, particularly before bed, has received considerable attention. Limiting and/or avoiding food before nighttime sleep has been proposed as both a weight loss strategy and approach to improve health and body composition. Indeed, negative outcomes have been demonstrated in response to large mixed meals in populations that consume a majority of their daily food intake during the night. However, data is beginning to mount to suggest that negative outcomes may not be consistent when the food choice is small, nutrient-dense, low energy foods and/or single macronutrients rather than large mixed-meals. From this perspective, it appears that a bedtime supply of nutrients can promote positive physiological changes in healthy populations. In addition, when nighttime feeding is combined with exercise training, any adverse effects appear to be eliminated in obese populations. Lastly, in Type I diabetics and those with glycogen storage disease, eating before bed is essential for survival. Nevertheless, nighttime consumption of small (~150 kcals) single nutrients or mixed-meals does not appear to be harmful and may be beneficial for muscle protein synthesis and cardiometabolic health. Future research is warranted to elucidate potential applications of nighttime feeding alone and in combination with exercise in various populations of health and disease. PMID:25859885

  7. Evaluation of NPP-VIIRS Nighttime Light Data for Mapping Global Fossil Fuel Combustion CO2 Emissions: A Comparison with DMSP-OLS Nighttime Light Data.

    PubMed

    Ou, Jinpei; Liu, Xiaoping; Li, Xia; Li, Meifang; Li, Wenkai

    2015-01-01

    Recently, the stable light products and radiance calibrated products from Defense Meteorological Satellite Program's (DMSP) Operational Linescan System (OLS) have been useful for mapping global fossil fuel carbon dioxide (CO2) emissions at fine spatial resolution. However, few studies on this subject were conducted with the new-generation nighttime light data from the Visible Infrared Imaging Radiometer Suite (VIIRS) sensor on the Suomi National Polar-orbiting Partnership (NPP) Satellite, which has a higher spatial resolution and a wider radiometric detection range than the traditional DMSP-OLS nighttime light data. Therefore, this study performed the first evaluation of the potential of NPP-VIIRS data in estimating the spatial distributions of global CO2 emissions (excluding power plant emissions). Through a disaggregating model, three global emission maps were then derived from population counts and three different types of nighttime lights data (NPP-VIIRS, the stable light data and radiance calibrated data of DMSP-OLS) for a comparative analysis. The results compared with the reference data of land cover in Beijing, Shanghai and Guangzhou show that the emission areas of map from NPP-VIIRS data have higher spatial consistency of the artificial surfaces and exhibit a more reasonable distribution of CO2 emission than those of other two maps from DMSP-OLS data. Besides, in contrast to two maps from DMSP-OLS data, the emission map from NPP-VIIRS data is closer to the Vulcan inventory and exhibits a better agreement with the actual statistical data of CO2 emissions at the level of sub-administrative units of the United States. This study demonstrates that the NPP-VIIRS data can be a powerful tool for studying the spatial distributions of CO2 emissions, as well as the socioeconomic indicators at multiple scales. PMID:26390037

  8. Evaluation of NPP-VIIRS Nighttime Light Data for Mapping Global Fossil Fuel Combustion CO2 Emissions: A Comparison with DMSP-OLS Nighttime Light Data

    PubMed Central

    Ou, Jinpei; Liu, Xiaoping; Li, Xia; Li, Meifang; Li, Wenkai

    2015-01-01

    Recently, the stable light products and radiance calibrated products from Defense Meteorological Satellite Program’s (DMSP) Operational Linescan System (OLS) have been useful for mapping global fossil fuel carbon dioxide (CO2) emissions at fine spatial resolution. However, few studies on this subject were conducted with the new-generation nighttime light data from the Visible Infrared Imaging Radiometer Suite (VIIRS) sensor on the Suomi National Polar-orbiting Partnership (NPP) Satellite, which has a higher spatial resolution and a wider radiometric detection range than the traditional DMSP-OLS nighttime light data. Therefore, this study performed the first evaluation of the potential of NPP-VIIRS data in estimating the spatial distributions of global CO2 emissions (excluding power plant emissions). Through a disaggregating model, three global emission maps were then derived from population counts and three different types of nighttime lights data (NPP-VIIRS, the stable light data and radiance calibrated data of DMSP-OLS) for a comparative analysis. The results compared with the reference data of land cover in Beijing, Shanghai and Guangzhou show that the emission areas of map from NPP-VIIRS data have higher spatial consistency of the artificial surfaces and exhibit a more reasonable distribution of CO2 emission than those of other two maps from DMSP-OLS data. Besides, in contrast to two maps from DMSP-OLS data, the emission map from NPP-VIIRS data is closer to the Vulcan inventory and exhibits a better agreement with the actual statistical data of CO2 emissions at the level of sub-administrative units of the United States. This study demonstrates that the NPP-VIIRS data can be a powerful tool for studying the spatial distributions of CO2 emissions, as well as the socioeconomic indicators at multiple scales. PMID:26390037

  9. Distinct Cellular Locations of Carbonic Anhydrases Mediate Carbon Dioxide Control of Stomatal Movements.

    PubMed

    Hu, Honghong; Rappel, Wouter-Jan; Occhipinti, Rossana; Ries, Amber; Böhmer, Maik; You, Lei; Xiao, Chuanlei; Engineer, Cawas B; Boron, Walter F; Schroeder, Julian I

    2015-10-01

    Elevated carbon dioxide (CO2) in leaves closes stomatal apertures. Research has shown key functions of the β-carbonic anhydrases (βCA1 and βCA4) in rapid CO2-induced stomatal movements by catalytic transmission of the CO2 signal in guard cells. However, the underlying mechanisms remain unclear, because initial studies indicate that these Arabidopsis (Arabidopsis thaliana) βCAs are targeted to distinct intracellular compartments upon expression in tobacco (Nicotiana benthamiana) cells. Which cellular location of these enzymes plays a key role in native guard cells in CO2-regulated stomatal movements remains unknown. Here, we express fluorescently tagged CAs in guard cells of ca1ca4 double-mutant plants and show that the specific locations of βCA4 at the plasma membrane and βCA1 in native guard cell chloroplasts each can mediate rapid CO2 control of stomatal movements. Localization and complementation analyses using a mammalian αCAII-yellow fluorescent protein in guard cells further show that cytoplasmic localization is also sufficient to restore CO2 regulation of stomatal conductance. Mathematical modeling of cellular CO2 catalysis suggests that the dynamics of the intracellular HCO3 (-) concentration change in guard cells can be driven by plasma membrane and cytoplasmic localizations of CAs but not as clearly by chloroplast targeting. Moreover, modeling supports the notion that the intracellular HCO3 (-) concentration dynamics in guard cells are a key mechanism in mediating CO2-regulated stomatal movements but that an additional chloroplast role of CAs exists that has yet to be identified. PMID:26243620

  10. Distinct Cellular Locations of Carbonic Anhydrases Mediate Carbon Dioxide Control of Stomatal Movements1[OPEN

    PubMed Central

    Hu, Honghong; Rappel, Wouter-Jan; Occhipinti, Rossana; Ries, Amber; Böhmer, Maik; You, Lei; Xiao, Chuanlei; Engineer, Cawas B.; Boron, Walter F.; Schroeder, Julian I.

    2015-01-01

    Elevated carbon dioxide (CO2) in leaves closes stomatal apertures. Research has shown key functions of the β-carbonic anhydrases (βCA1 and βCA4) in rapid CO2-induced stomatal movements by catalytic transmission of the CO2 signal in guard cells. However, the underlying mechanisms remain unclear, because initial studies indicate that these Arabidopsis (Arabidopsis thaliana) βCAs are targeted to distinct intracellular compartments upon expression in tobacco (Nicotiana benthamiana) cells. Which cellular location of these enzymes plays a key role in native guard cells in CO2-regulated stomatal movements remains unknown. Here, we express fluorescently tagged CAs in guard cells of ca1ca4 double-mutant plants and show that the specific locations of βCA4 at the plasma membrane and βCA1 in native guard cell chloroplasts each can mediate rapid CO2 control of stomatal movements. Localization and complementation analyses using a mammalian αCAII-yellow fluorescent protein in guard cells further show that cytoplasmic localization is also sufficient to restore CO2 regulation of stomatal conductance. Mathematical modeling of cellular CO2 catalysis suggests that the dynamics of the intracellular HCO3− concentration change in guard cells can be driven by plasma membrane and cytoplasmic localizations of CAs but not as clearly by chloroplast targeting. Moreover, modeling supports the notion that the intracellular HCO3− concentration dynamics in guard cells are a key mechanism in mediating CO2-regulated stomatal movements but that an additional chloroplast role of CAs exists that has yet to be identified. PMID:26243620

  11. Honey and Radiation-Induced Stomatitis in Patients With Head and Neck Cancer

    PubMed Central

    Bahramnezhad, Fatemeh; Dehghan Nayeri, Nahid; Bassampour, Shiva Sadat; Khajeh, Mahboobeh; Asgari, Parvaneh

    2015-01-01

    Background: Stomatitis is a common oral complication which affects 100% of patients undergoing head and neck radiotherapy. Acute stomatitis might cause failure and delay radiotherapy. Attention to mouth hygiene, particularly using mouthwash, has a fundamental importance for these patients. Objectives: The current study came to addresses the effects of pure natural honey on radiation-induced stomatitis in patients with a variety of head and neck cancers. Patients and Methods: The present single-blinded nonrandomized controlled trial was conducted on 105 patients undergoing radiotherapy due to head and neck cancer at the radiation unit of Shafa hospital in Kerman, Iran, from October 2012 to March 2012. The research groups were selected by writing the names of the protocols (the mouthwashes of chamomile, honey and the common caring protocol at ward which uses water) on three cubes. The first extracted cube was related to the chamomile mouthwash (Matrica), the second to the honey mouthwash and the last cube to the water mouthwash. The first experimental group (n = 35) gurgled a solution containing 20 mL diluted honey, the second group gurgled a solution containing German chamomile, and the 35 patients in the control group were advised to gurgle 20 mL water (the ward routine). Results: The results showed that severe stomatitis in groups of honey, chamomile and control was 0, 5.7%, and 17.6%, respectively. On the 14th day, it was 0, 0, and 17.6%, respectively. There were significant differences between the three groups regarding the severity of stomatitis in the 14th day (P < 0.001). Conclusions: The application of natural honey is effective in managing and preventing radiation-induced stomatitis in patients with head and neck cancers. PMID:26568850

  12. Photosynthesis-dependent/independent control of stomatal responses to CO2 in mutant barley with surplus electron transport capacity and reduced SLAH3 anion channel transcript.

    PubMed

    Córdoba, Javier; Molina-Cano, José-Luis; Pérez, Pilar; Morcuende, Rosa; Moralejo, Marian; Savé, Robert; Martínez-Carrasco, Rafael

    2015-10-01

    The mechanisms of stomatal sensitivity to CO2 are yet to be fully understood. The role of photosynthetic and non-photosynthetic factors in stomatal responses to CO2 was investigated in wild-type barley (Hordeum vulgare var. Graphic) and in a mutant (G132) with decreased photochemical and Rubisco capacities. The CO2 and DCMU responses of stomatal conductance (gs), gas exchange, chlorophyll fluorescence and levels of ATP, with a putative transcript for stomatal opening were analysed. G132 had greater gs than the wild-type, despite lower photosynthesis rates and higher intercellular CO2 concentrations (Ci). The mutant had Rubisco-limited photosynthesis at very high CO2 levels, and higher ATP contents than the wild-type. Stomatal sensitivity to CO2 under red light was lower in G132 than in the wild-type, both in photosynthesizing and DCMU-inhibited leaves. Under constant Ci and red light, stomatal sensitivity to DCMU inhibition was higher in G132. The levels of a SLAH3-like slow anion channel transcript, involved in stomatal closure, decreased sharply in G132. The results suggest that stomatal responses to CO2 depend partly on the balance of photosynthetic electron transport to carbon assimilation capacities, but are partially regulated by the CO2 signalling network. High gs can improve the adaptation to climate change in well-watered conditions.

  13. Photosynthesis-dependent/independent control of stomatal responses to CO2 in mutant barley with surplus electron transport capacity and reduced SLAH3 anion channel transcript.

    PubMed

    Córdoba, Javier; Molina-Cano, José-Luis; Pérez, Pilar; Morcuende, Rosa; Moralejo, Marian; Savé, Robert; Martínez-Carrasco, Rafael

    2015-10-01

    The mechanisms of stomatal sensitivity to CO2 are yet to be fully understood. The role of photosynthetic and non-photosynthetic factors in stomatal responses to CO2 was investigated in wild-type barley (Hordeum vulgare var. Graphic) and in a mutant (G132) with decreased photochemical and Rubisco capacities. The CO2 and DCMU responses of stomatal conductance (gs), gas exchange, chlorophyll fluorescence and levels of ATP, with a putative transcript for stomatal opening were analysed. G132 had greater gs than the wild-type, despite lower photosynthesis rates and higher intercellular CO2 concentrations (Ci). The mutant had Rubisco-limited photosynthesis at very high CO2 levels, and higher ATP contents than the wild-type. Stomatal sensitivity to CO2 under red light was lower in G132 than in the wild-type, both in photosynthesizing and DCMU-inhibited leaves. Under constant Ci and red light, stomatal sensitivity to DCMU inhibition was higher in G132. The levels of a SLAH3-like slow anion channel transcript, involved in stomatal closure, decreased sharply in G132. The results suggest that stomatal responses to CO2 depend partly on the balance of photosynthetic electron transport to carbon assimilation capacities, but are partially regulated by the CO2 signalling network. High gs can improve the adaptation to climate change in well-watered conditions. PMID:26398787

  14. Changes in stomatal function and water use efficiency in potato plants with altered sucrolytic activity.

    PubMed

    Antunes, Werner C; Provart, Nicholas J; Williams, Thomas C R; Loureiro, Marcelo E

    2012-04-01

    As water availability for agriculture decreases, breeding or engineering of crops with improved water use efficiency (WUE) will be necessary. As stomata are responsible for controlling gas exchange across the plant epidermis, metabolic processes influencing solute accumulation in guard cells are potential targets for engineering. In addition to its role as an osmoticum, sucrose breakdown may be required for synthesis of other osmotica or generation of the ATP needed for solute uptake. Thus, alterations in partitioning of sucrose between storage and breakdown may affect stomatal function. In agreement with this hypothesis, potato (Solanum tuberosum) plants expressing an antisense construct targeted against sucrose synthase 3 (SuSy3) exhibited decreased stomatal conductance, a slight reduction in CO(2) fixation and increased WUE. Conversely, plants with increased guard cell acid invertase activity caused by the introduction of the SUC2 gene from yeast had increased stomatal conductance, increased CO(2) fixation and decreased WUE. (14)CO(2) feeding experiments indicated that these effects cannot be attributed to alterations in photosynthetic capacity, and most likely reflect alterations in stomatal function. These results highlight the important role that sucrose breakdown may play in guard cell function and indicate the feasibility of manipulating plant WUE through engineering of guard cell sucrose metabolism.

  15. Use of infrared thermography for monitoring stomatal closure in the field: application to grapevine.

    PubMed

    Jones, Hamlyn G; Stoll, Manfred; Santos, Tiago; de Sousa, Claudia; Chaves, M Manuela; Grant, Olga M

    2002-11-01

    This paper reviews and discusses strategies for the use of thermal imaging for studies of stomatal conductance in the field and compares techniques for image collection and analysis. Measurements were taken under a range of environmental conditions and on sunlit and shaded canopies to illustrate the variability of temperatures and derived stress indices. A simple procedure is presented for correcting for calibration drift within the images from the low-cost thermal imager used (SnapShot 225, Infrared Solutions, Inc.). The use of wet and dry reference surfaces as thresholds to eliminate the inclusion of non-leaf material in the analysis of canopy temperature is discussed. An index that is proportional to stomatal conductance was compared with stomatal measurements with a porometer. The advantages and disadvantages of a possible new approach to the use of thermal imagery for the detection of stomatal closure in grapevine canopies, based on an analysis of the temperature of shaded leaves, rather than sunlit leaves, are discussed. Evidence is presented that the temperature of reference surfaces exposed within the canopy can be affected by the canopy water status. PMID:12379792

  16. Stomatal encryption by epicuticular waxes as a plastic trait modifying gas exchange in a Mediterranean evergreen species (Quercus coccifera L.).

    PubMed

    Roth-Nebelsick, Anita; Fernández, Victoria; Peguero-Pina, José Javier; Sancho-Knapik, Domingo; Gil-Pelegrín, Eustaquio

    2013-03-01

    The adaptive benefit of stomatal crypts remains a matter of controversy. This work studies the effect on gas exchange of cuticular rims that overarch the stomatal pore in the Mediterranean species Quercus coccifera L. growing under Mediterranean (lower relative humidities and high summer temperatures) or oceanic conditions (higher daily relative humidities and mild temperatures). After microscopic assessment of the leaf surfaces and stomatal architecture, the impact of the cuticular 'cup' on gas exchange was evaluated by employing three-dimensional finite element models. Here, we provide evidence for a high plasticity of the Q. coccifera cuticular cup, with much larger vents under oceanic conditions compared to small vents under Mediterranean conditions. This structure adds a substantial fixed resistance thereby strongly decreasing gas exchange under Mediterranean conditions. The cuticular cup, which also increases leaf internal humidity, might buffer the rapid changes in vapour pressure deficit (VPD) often observed under Mediterranean conditions. Since water loss of guard and adjacent epidermal cells regulates stomatal aperture, we suggest that this structure allows an efficient regulation of stomatal conductance and optimum use of resources under high VPD. This study provides evidence that plasticity of stomatal architecture can be an important structural component of hydraulic adaptation to different climate conditions. PMID:22897384

  17. Stomatal encryption by epicuticular waxes as a plastic trait modifying gas exchange in a Mediterranean evergreen species (Quercus coccifera L.).

    PubMed

    Roth-Nebelsick, Anita; Fernández, Victoria; Peguero-Pina, José Javier; Sancho-Knapik, Domingo; Gil-Pelegrín, Eustaquio

    2013-03-01

    The adaptive benefit of stomatal crypts remains a matter of controversy. This work studies the effect on gas exchange of cuticular rims that overarch the stomatal pore in the Mediterranean species Quercus coccifera L. growing under Mediterranean (lower relative humidities and high summer temperatures) or oceanic conditions (higher daily relative humidities and mild temperatures). After microscopic assessment of the leaf surfaces and stomatal architecture, the impact of the cuticular 'cup' on gas exchange was evaluated by employing three-dimensional finite element models. Here, we provide evidence for a high plasticity of the Q. coccifera cuticular cup, with much larger vents under oceanic conditions compared to small vents under Mediterranean conditions. This structure adds a substantial fixed resistance thereby strongly decreasing gas exchange under Mediterranean conditions. The cuticular cup, which also increases leaf internal humidity, might buffer the rapid changes in vapour pressure deficit (VPD) often observed under Mediterranean conditions. Since water loss of guard and adjacent epidermal cells regulates stomatal aperture, we suggest that this structure allows an efficient regulation of stomatal conductance and optimum use of resources under high VPD. This study provides evidence that plasticity of stomatal architecture can be an important structural component of hydraulic adaptation to different climate conditions.

  18. Responses of two semiarid conifer tree species to reduced precipitation and warming reveal new perspectives for stomatal regulation

    SciTech Connect

    Garcia-Forner, Nuria; Adams, Henry D.; Sevanto, Sanna; Collins, Adam D.; Dickman, Lee T.; Hudson, Patrick J.; Zeppel, Melanie J. B.; Jenkins, Michael W.; Powers, Heath; Martinez-Vilalta, Jordi; Mcdowell, Nate G.

    2015-08-08

    Here, relatively anisohydric species are predicted to be more predisposed to hydraulic failure than relatively isohydric species, as they operate with narrower hydraulic safety margins. We subjected co-occurring anisohydric Juniperus monosperma and isohydric Pinus edulis trees to warming, reduced precipitation, or both, and measured their gas exchange and hydraulic responses. We found that reductions in stomatal conductance and assimilation by heat and drought were more frequent during relatively moist periods, but these effects were not exacerbated in the combined heat and drought treatment. Counter to expectations, both species exhibited similar gs temporal dynamics in response to drought. Further, whereas P. edulis exhibited chronic embolism, J. monosperma showed very little embolism due to its conservative stomatal regulation and maintenance of xylem water potential above the embolism entry point. This tight stomatal control and low levels of embolism experienced by juniper refuted the notion that very low water potentials during drought are associated with loose stomatal control and with the hypothesis that anisohydric species are more prone to hydraulic failure than isohydric species. Because direct association of stomatal behaviour with embolism resistance can be misleading, we advocate consideration of stomatal behaviour relative to embolism resistance for classifying species drought response strategies.

  19. Responses of two semiarid conifer tree species to reduced precipitation and warming reveal new perspectives for stomatal regulation

    DOE PAGES

    Garcia-Forner, Nuria; Adams, Henry D.; Sevanto, Sanna; Collins, Adam D.; Dickman, Lee T.; Hudson, Patrick J.; Zeppel, Melanie J. B.; Jenkins, Michael W.; Powers, Heath; Martinez-Vilalta, Jordi; et al

    2015-08-08

    Here, relatively anisohydric species are predicted to be more predisposed to hydraulic failure than relatively isohydric species, as they operate with narrower hydraulic safety margins. We subjected co-occurring anisohydric Juniperus monosperma and isohydric Pinus edulis trees to warming, reduced precipitation, or both, and measured their gas exchange and hydraulic responses. We found that reductions in stomatal conductance and assimilation by heat and drought were more frequent during relatively moist periods, but these effects were not exacerbated in the combined heat and drought treatment. Counter to expectations, both species exhibited similar gs temporal dynamics in response to drought. Further, whereas P.more » edulis exhibited chronic embolism, J. monosperma showed very little embolism due to its conservative stomatal regulation and maintenance of xylem water potential above the embolism entry point. This tight stomatal control and low levels of embolism experienced by juniper refuted the notion that very low water potentials during drought are associated with loose stomatal control and with the hypothesis that anisohydric species are more prone to hydraulic failure than isohydric species. Because direct association of stomatal behaviour with embolism resistance can be misleading, we advocate consideration of stomatal behaviour relative to embolism resistance for classifying species drought response strategies.« less

  20. Responses of two semiarid conifer tree species to reduced precipitation and warming reveal new perspectives for stomatal regulation.

    PubMed

    Garcia-Forner, Núria; Adams, Henry D; Sevanto, Sanna; Collins, Adam D; Dickman, Lee T; Hudson, Patrick J; Zeppel, Melanie J B; Jenkins, Michael W; Powers, Heath; Martínez-Vilalta, Jordi; Mcdowell, Nate G

    2016-01-01

    Relatively anisohydric species are predicted to be more predisposed to hydraulic failure than relatively isohydric species, as they operate with narrower hydraulic safety margins. We subjected co-occurring anisohydric Juniperus monosperma and isohydric Pinus edulis trees to warming, reduced precipitation, or both, and measured their gas exchange and hydraulic responses. We found that reductions in stomatal conductance and assimilation by heat and drought were more frequent during relatively moist periods, but these effects were not exacerbated in the combined heat and drought treatment. Counter to expectations, both species exhibited similar gs temporal dynamics in response to drought. Further, whereas P. edulis exhibited chronic embolism, J. monosperma showed very little embolism due to its conservative stomatal regulation and maintenance of xylem water potential above the embolism entry point. This tight stomatal control and low levels of embolism experienced by juniper refuted the notion that very low water potentials during drought are associated with loose stomatal control and with the hypothesis that anisohydric species are more prone to hydraulic failure than isohydric species. Because direct association of stomatal behaviour with embolism resistance can be misleading, we advocate consideration of stomatal behaviour relative to embolism resistance for classifying species drought response strategies. PMID:26081870

  1. Plant virus infections control stomatal development

    PubMed Central

    Murray, Rose R.; Emblow, Mark S. M.; Hetherington, Alistair M.; Foster, Gary D.

    2016-01-01

    Stomata are important regulators of carbon dioxide uptake and transpirational water loss. They also represent points of vulnerability as bacterial and fungal pathogens utilise this natural opening as an entry portal, and thus have an increasingly complex relationship. Unlike the situation with bacterial and fungal pathogens, we know very little about the role of stomata in viral infection. Here we report findings showing that viral infection influences stomatal development in two susceptible host systems (Nicotiana tabacum with TMV (Tobacco mosaic virus), and Arabidopsis thaliana with TVCV (Turnip vein-clearing virus)), but not in resistant host systems (Nicotiana glutinosa and Chenopodium quinoa with TMV). Virus infected plants had significantly lower stomatal indices in systemic leaves of susceptible systems; N. tabacum 9.8% reduction and A. thaliana 12.3% reduction, but not in the resistant hosts. Stomatal density in systemic leaves was also significantly reduced in virus infected A. thaliana by 19.6% but not in N. tabacum or the resistant systems. In addition, transpiration rate was significantly reduced in TMV infected N. tabacum. PMID:27687773

  2. Stomatal Dimorphism of Neodiplogaster acaloleptae (Diplogastromorpha: Diplogastridae)

    PubMed Central

    Kanzaki, Natsumi

    2016-01-01

    Several genera belonging to the nematode family Diplogastridae show characteristic dimorphism in their feeding structures; specifically, they have microbial feeding stenostomatous and predatory eurystomatous morphs. A diplogastrid satellite model species, Pristionchus pacificus, and its close relatives have become a model system for studying this phenotypic plasticity, with intensive physiological and structural studies having been undertaken. However, the many other species that are morphologically and phylogenetically divergent from P. pacificus have not been examined to date. In the present study, the detailed stomatal structure and induction of dimorphism in Neodiplogaster acaloleptae were examined. N. acaloleptae has a fungal feeding stenostomatous morph and a predatory eurystomatous morph. The predatory morph was induced by starvation, high population density, and co-culturing with its potential prey, Caenorhabditis elegans. The feeding behavior of the stenostomatous and eurystomatous morphs of N. acaloleptae was confirmed, demonstrating that 1) the stomatal and pharyngeal movements of the two morphs were basically identical, and 2) the stomatal elements were protracted to cut open the hyphae and/or prey to feed when a N. acaloleptae flips its dorsal movable tooth dorsally and tilts its subventral stegostomatal cylinder ventrally, forming a pair of scissors to cut the food source. The stoma morphology of N. acaloleptae with a single movable tooth and a long stoma is markedly different from that of Pristionchus, which has two movable teeth and a short stoma. It is, however, similar to that of Mononchoides, tentatively a sister to Neodiplogaster. PMID:27196730

  3. Plant virus infections control stomatal development

    NASA Astrophysics Data System (ADS)

    Murray, Rose R.; Emblow, Mark S. M.; Hetherington, Alistair M.; Foster, Gary D.

    2016-09-01

    Stomata are important regulators of carbon dioxide uptake and transpirational water loss. They also represent points of vulnerability as bacterial and fungal pathogens utilise this natural opening as an entry portal, and thus have an increasingly complex relationship. Unlike the situation with bacterial and fungal pathogens, we know very little about the role of stomata in viral infection. Here we report findings showing that viral infection influences stomatal development in two susceptible host systems (Nicotiana tabacum with TMV (Tobacco mosaic virus), and Arabidopsis thaliana with TVCV (Turnip vein-clearing virus)), but not in resistant host systems (Nicotiana glutinosa and Chenopodium quinoa with TMV). Virus infected plants had significantly lower stomatal indices in systemic leaves of susceptible systems; N. tabacum 9.8% reduction and A. thaliana 12.3% reduction, but not in the resistant hosts. Stomatal density in systemic leaves was also significantly reduced in virus infected A. thaliana by 19.6% but not in N. tabacum or the resistant systems. In addition, transpiration rate was significantly reduced in TMV infected N. tabacum.

  4. Association genetics, geography and ecophysiology link stomatal patterning in Populus trichocarpa with carbon gain and disease resistance trade-offs.

    PubMed

    McKown, Athena D; Guy, Robert D; Quamme, Linda; Klápště, Jaroslav; La Mantia, Jonathan; Constabel, C P; El-Kassaby, Yousry A; Hamelin, Richard C; Zifkin, Michael; Azam, M S

    2014-12-01

    Stomata are essential for diffusive entry of gases to support photosynthesis, but may also expose internal leaf tissues to pathogens. To uncover trade-offs in range-wide adaptation relating to stomata, we investigated the underlying genetics of stomatal traits and linked variability in these traits with geoclimate, ecophysiology, condensed foliar tannins and pathogen susceptibility in black cottonwood (Populus trichocarpa). Upper (adaxial) and lower (abaxial) leaf stomatal traits were measured from 454 accessions collected throughout much of the species range. We calculated broad-sense heritability (H(2) ) of stomatal traits and, using SNP data from a 34K Populus SNP array, performed a genome-wide association studies (GWAS) to uncover genes underlying stomatal trait variation. H(2) values for stomatal traits were moderate (average H(2) = 0.33). GWAS identified genes associated primarily with adaxial stomata, including polarity genes (PHABULOSA), stomatal development genes (BRASSINOSTEROID-INSENSITIVE 2) and disease/wound-response genes (GLUTAMATE-CYSTEINE LIGASE). Stomatal traits correlated with latitude, gas exchange, condensed tannins and leaf rust (Melampsora) infection. Latitudinal trends of greater adaxial stomata numbers and guard cell pore size corresponded with higher stomatal conductance (gs ) and photosynthesis (Amax ), faster shoot elongation, lower foliar tannins and greater Melampsora susceptibility. This suggests an evolutionary trade-off related to differing selection pressures across the species range. In northern environments, more adaxial stomata and larger pore sizes reflect selection for rapid carbon gain and growth. By contrast, southern genotypes have fewer adaxial stomata, smaller pore sizes and higher levels of condensed tannins, possibly linked to greater pressure from natural leaf pathogens, which are less significant in northern ecosystems.

  5. Gas Exchange Analysis of the Relative Importance of Stomatal and Biochemical Factors in Photosynthetic Induction in Alocasia macrorrhiza1

    PubMed Central

    Kirschbaum, Miko U. F.; Pearcy, Robert W.

    1988-01-01

    When leaves of Alocasia macrorrhiza adapted to 10 micromole quanta per square meter per second were transferred to 500 micromole quanta per square meter per second, the rate of photosynthetic CO2 assimilation increased for over 45 minutes. For the first 10 to 15 minutes, increases in both stomatal conductance and the leaf's photosynthetic capacity were responsible for the increase in assimilation rate. Thereafter, continuing increases in stomatal conductance were almost entirely responsible for further increases in assimilation rate. When conductances were initially high, assimilation rates 1 minute after the increase in photon flux density could be more than six times as high as for similar leaves with initially low conductance. Further increases in assimilation rate in these leaves with high conductance were predominantly due to increases in the induction state at the biochemical level and followed an exponential time course. When stomatal conductances were initially low, then increases in conductance were predominantly responsible for the increases in assimilation rate, with both following a sigmoidal time course. In these leaves, it was important to also consider the effect of cuticular water loss on the calculation of the intracellular partial pressure of CO2, and an assessment of the relative importance of stomatal conductance differed considerably from one that did not include cuticular water loss. PMID:16665988

  6. Napping in College Students and Its Relationship with Nighttime Sleep

    ERIC Educational Resources Information Center

    Ye, Lichuan; Hutton Johnson, Stacy; Keane, Kathleen; Manasia, Michael; Gregas, Matt

    2015-01-01

    Objective: To examine the habit of napping and its relationship with nighttime sleep in college students. Participants: Four hundred and forty undergraduate students who responded to an anonymous online survey in April 2010. Methods: Three questions were asked to determine the frequency, length, and timing of napping during the past month. Sleep…

  7. The Ionospheric Mid-Latitude Summer Nighttime Anomaly

    NASA Astrophysics Data System (ADS)

    Lin, C.; Chen, C.; Hsu, M.; Liu, C. H.; Liu, J. G.; Burns, A. G.; Wang, W.

    2009-12-01

    This paper presents monthly variations of the mid-latitude summer nighttime anomaly (MSNA) of the ionosphere for the first time by using global observations of the FORMOSAT-3/COSMIC (F3/C), NASA TIMED-GUVI, ground-based radars and GPS receiver network. The MSNA is characterized by greater nighttime (19:00 LT - 24:00 LT, or period of larger solar zenith angles) ionospheric electron density than that during daytime (08:00 - 18:00 LT, or period of smaller solar zenith angles) at middle latitudes during solstices. The anomaly shown in the southern hemisphere during December solstice was previously known as the Weddell Sea Anomaly (WSA) occurring around the Antarctica and the nearby Pacific Ocean, while a WSA-like electron density structure also occurs in the northern hemisphere around June solstice. This study demonstrates that the anomalies occurred in both the northern and southern hemispheres share similar character of greater nighttime density. Moreover, the latitude-altitude cross-section plots of the electron density structure show very similar time-varying electron density evolutions of the MSNA. In both hemispheres, the anomalies with similar electron density characteristics and variations caused by the similar mechanism prompts us to name this phenomenon the mid-latitude summer nighttime anomaly.

  8. Modelling ozone stomatal flux of wheat under mediterranean conditions

    NASA Astrophysics Data System (ADS)

    González-Fernández, I.; Bermejo, V.; Elvira, S.; de la Torre, D.; González, A.; Navarrete, L.; Sanz, J.; Calvete, H.; García-Gómez, H.; López, A.; Serra, J.; Lafarga, A.; Armesto, A. P.; Calvo, A.; Alonso, R.

    2013-03-01

    Correct estimation of leaf-level stomatal conductance (gsto) is central for current ozone (O3) risk assessment of wheat yield loss based on the absorbed O3 phytotoxic dose (POD). The gsto model parameterizations developed in Europe must be checked in the different climatic regions where they are going to be applied in order to reduce the uncertainties associated with the POD approach. This work proposes a new gsto model parameterization for estimating POD of Triticum aestivum and Triticum durum under Mediterranean conditions, based on phenological observations over 25 years and gsto field measurements during 5 growing seasons. Results show that POD in the Mediterranean area might be higher than previously estimated. However, caution must be paid when assessing the risk of yield loss for wheat in this area since field validation of O3 impacts is still limited.

  9. Seasonal stomatal behavior of a common desert shrub and the influence of plant neighbors.

    PubMed

    Kropp, Heather; Ogle, Kiona

    2015-02-01

    Stomata simultaneously regulate plant carbon gain and water loss, and patterns of stomatal conductance (g(s)) provide insight into water use strategies. In arid systems, g(s) varies seasonally based on factors such as water availability and temperature. Moreover, the presence and species identity of neighboring plants likely affects g(s) of the focal plant by altering available soil water and microclimate conditions. We investigated stomatal behavior in Larrea tridentata, a drought-tolerant, evergreen shrub occurring throughout the arid southwestern United States. We measured g(s) in Larrea over multiple seasons in the presence of neighbors representing different woody species. The data were analyzed in the context of a commonly used phenomenological model that relates g(s) to vapor pressure deficit (D) to understand spatial and temporal differences in stomatal behavior. We found that g(s) in Larrea was affected by neighborhood association, and these effects varied seasonally. The greatest effect of neighborhood association on g(s) occurred during the winter period, where Larrea growing alone (without neighbors) had higher g(s) compared to Larrea growing with neighbors. Larrea's stomatal sensitivity to D and reference conductance (i.e., g(s) at D = 1 kPa) also differed significantly among different neighbor associations. Random effects indicated reference g(s) varied over short time scales (daily), while stomatal sensitivity showed little daily or seasonal variation, but was notably affected by neighbor associations such that neighboring species, especially trees, reduced Larrea's sensitivity to D. Overall, seasonal dynamics and neighborhood conditions appear critical to understanding temporal and spatial variation in Larrea's physiological behavior. PMID:25526845

  10. Nighttime chemistry at a high altitude site above Hong Kong

    NASA Astrophysics Data System (ADS)

    Brown, Steven S.; Dubé, William P.; Tham, Yee Jun; Zha, Qiaozhi; Xue, Likun; Poon, Steven; Wang, Zhe; Blake, Donald R.; Tsui, Wilson; Parrish, David D.; Wang, Tao

    2016-03-01

    Nighttime reactions of nitrogen oxides influence ozone, volatile organic compounds, and aerosol and are thus important to the understanding of regional air quality. Despite large emissions and rapid recent growth of nitrogen oxide concentrations, there are few studies of nighttime chemistry in China. Here we present measurements of nighttime nitrogen oxides, NO3 and N2O5, from a coastal mountaintop site in Hong Kong adjacent to the megacities of the Pearl River Delta region. This is the first study of nighttime chemistry from a site within the residual layer in China. Key findings include the following. First, highly concentrated urban NOx outflow from the Pearl River Delta region was sampled infrequently at night, with N2O5 mixing ratios up to 8 ppbv (1 min average) or 12 ppbv (1 s average) in nighttime aged air masses. Second, the average N2O5 uptake coefficient was determined from a best fit to the available steady state lifetime data as γ(N2O5) = 0.014 ± 0.007. Although this determination is uncertain due to the difficulty of separating N2O5 losses from those of NO3, this value is in the range of previous residual layer determinations of N2O5 uptake coefficients in polluted air in North America. Third, there was a significant contribution of biogenic hydrocarbons to NO3 loss inferred from canister samples taken during daytime. Finally, daytime N2O5 mixing ratios were in accord with their predicted photochemical steady state. Heterogeneous uptake of N2O5 in fog is determined to be an important production mechanism for soluble nitrate, even during daytime.

  11. Stomatal Blue Light Response Is Present in Early Vascular Plants.

    PubMed

    Doi, Michio; Kitagawa, Yuki; Shimazaki, Ken-ichiro

    2015-10-01

    Light is a major environmental factor required for stomatal opening. Blue light (BL) induces stomatal opening in higher plants as a signal under the photosynthetic active radiation. The stomatal BL response is not present in the fern species of Polypodiopsida. The acquisition of a stomatal BL response might provide competitive advantages in both the uptake of CO2 and prevention of water loss with the ability to rapidly open and close stomata. We surveyed the stomatal opening in response to strong red light (RL) and weak BL under the RL with gas exchange technique in a diverse selection of plant species from euphyllophytes, including spermatophytes and monilophytes, to lycophytes. We showed the presence of RL-induced stomatal opening in most of these species and found that the BL responses operated in all euphyllophytes except Polypodiopsida. We also confirmed that the stomatal opening in lycophytes, the early vascular plants, is driven by plasma membrane proton-translocating adenosine triphosphatase and K(+) accumulation in guard cells, which is the same mechanism operating in stomata of angiosperms. These results suggest that the early vascular plants respond to both RL and BL and actively regulate stomatal aperture. We also found three plant species that absolutely require BL for both stomatal opening and photosynthetic CO2 fixation, including a gymnosperm, C. revoluta, and the ferns Equisetum hyemale and Psilotum nudum. PMID:26307440

  12. Stomatal Blue Light Response Is Present in Early Vascular Plants.

    PubMed

    Doi, Michio; Kitagawa, Yuki; Shimazaki, Ken-ichiro

    2015-10-01

    Light is a major environmental factor required for stomatal opening. Blue light (BL) induces stomatal opening in higher plants as a signal under the photosynthetic active radiation. The stomatal BL response is not present in the fern species of Polypodiopsida. The acquisition of a stomatal BL response might provide competitive advantages in both the uptake of CO2 and prevention of water loss with the ability to rapidly open and close stomata. We surveyed the stomatal opening in response to strong red light (RL) and weak BL under the RL with gas exchange technique in a diverse selection of plant species from euphyllophytes, including spermatophytes and monilophytes, to lycophytes. We showed the presence of RL-induced stomatal opening in most of these species and found that the BL responses operated in all euphyllophytes except Polypodiopsida. We also confirmed that the stomatal opening in lycophytes, the early vascular plants, is driven by plasma membrane proton-translocating adenosine triphosphatase and K(+) accumulation in guard cells, which is the same mechanism operating in stomata of angiosperms. These results suggest that the early vascular plants respond to both RL and BL and actively regulate stomatal aperture. We also found three plant species that absolutely require BL for both stomatal opening and photosynthetic CO2 fixation, including a gymnosperm, C. revoluta, and the ferns Equisetum hyemale and Psilotum nudum.

  13. Dependence of the Extent and Direction of Average Stomatal Response in Zea mays L. and Phaseolus vulgaris L. on the Frequency of Fluctuations in Environmental Stimuli.

    PubMed Central

    Cardon, Z. G.; Berry, J. A.; Woodrow, I. E.

    1994-01-01

    Stomatal responses to fluctuating light and CO2 were investigated in Zea mays and Phaseolus vulgaris. Slow-moving stomata can affect carbon gain and water loss by plants during light flecks, under dynamic cloud cover, during alternating windy and calm air conditions (which influence CO2 concentrations and humidity immediately around leaves in plant canopies), at natural CO2 vents, or in growth chambers with imperfect CO2 control. It was found that the frequency of constant-amplitude fluctuations in light and CO2 dramatically affected the time-averaged stomatal conductance in both Zea and Phaseolus. During oscillations in light, average stomatal conductance was driven either above or below that observed at steady state at the average light level, depending on the frequency of the oscillations. Under oscillating CO2, the departure of average stomatal conductance away from that observed at steady state at the average CO2 level was also frequency dependent in both species. Upon cessation of oscillations and return of light or CO2 to the stable median level, stomatal conductance also returned to a steady state, matching that before oscillations were initiated. This work shows that fluctuations in light and CO2, and equally important, their frequency, can be critical in determining time-averaged stomatal conductance under unstable environmental conditions. PMID:12232261

  14. Recurrent aphthous stomatitis and Helicobacter pylori

    PubMed Central

    Gomes, Carolina-Cavaliéri; Gomez, Ricardo-Santiago; Zina, Lívia-Guimarães

    2016-01-01

    Background Recurrent aphthous stomatitis (RAS) is a recurrent painful ulcerative disorder that commonly affects the oral mucosa. Local and systemic factors such as trauma, food sensitivity, nutritional deficiencies, systemic conditions, immunological disorders and genetic polymorphisms are associated with the development of the disease. Helicobacter pylori (H. pylori) is a gram-negative, microaerophile bacteria, that colonizes the gastric mucosa and it was previously suggested to be involved in RAS development. In the present paper we reviewed all previous studies that investigated the association between RAS and H. pylori. Material and Methods A search in Pubmed (MEDLINE) databases was made of articles published up until July 2015 using the following keywords: Helicobacter Pylori or H. pylori and RAS or Recurrent aphthous stomatitis. Results Fifteen experimental studies that addressed the relationship between infection with H. pylori and the presence of RAS and three reviews, including a systematic review and a meta-analysis were included in this review. The studies reviewed used different methods to assess this relationship, including PCR, nested PCR, culture, ELISA and urea breath test. A large variation in the number of patients included in each study, as well as inclusion criteria and laboratorial methods was observed. H. pylori can be detected in the oral mucosa or ulcerated lesion of some patients with RAS. The quality of the all studies included in this review was assessed using levels of evidence based on the University of Oxford’s Center for Evidence Based Medicine Criteria. Conclusions Although the eradication of the infection may affect the clinical course of the oral lesions by undetermined mechanisms, RAS ulcers are not associated with the presence of the bacteria in the oral cavity and there is no evidence that H. pylori infection drives RAS development. Key words:Campylobacter, elisa, h. pylori, Helicobacter Pylori, RAS, recurrent aphthous

  15. Photosynthetic and stomatal acclimation to elevated CO{sub 2} depends on soil type in Quercus prinus

    SciTech Connect

    Bunce, J.A.

    1995-06-01

    Quercus prinus (L.) seedlings grown outdoors at ambient and elevated (ambient + 350 ppm) CO{sub 2} with a fertile soil had no photosynthetic acclimation to elevated CO{sub 2} and no stomatal response to growth or measurement CO{sub 2}. In contrast, seedlings grown with soil collected from a Q. prinus stand had photosynthetic and stomatal acclimation, and stomatal conductance was sensitive to measurement CO{sub 2}. In plants grown with the native soil, light-saturated stomatal conductance measured at the growth CO{sub 2} was reduced by 54% at elevated CO{sub 2}, compared to the short-term reduction of 36%. Photosynthetic acclimation in plants grown with the native soil reduced the stimulation of light-saturated photosynthesis at elevated CO{sub 2} from a factor of 1.9 to a factor of 1.3. In contrast to the dependence of photosynthetic and stomatal acclimation on soil type, the response of leaf respiration to elevated CO{sub 2} was the same for both soils. Respiration of leaves was reduced in the elevated CO{sub 2} treatment by 41 % on a leaf area basis. However, this effect was immediately reversible by altering the measurement CO{sub 2}, indicating that no acclimation of respiration occurred.

  16. 21 CFR 338.10 - Nighttime sleep-aid active ingredients.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 5 2010-04-01 2010-04-01 false Nighttime sleep-aid active ingredients. 338.10... (CONTINUED) DRUGS FOR HUMAN USE NIGHTTIME SLEEP-AID DRUG PRODUCTS FOR OVER-THE-COUNTER HUMAN USE Active Ingredients § 338.10 Nighttime sleep-aid active ingredients. The active ingredient of the product consists...

  17. 21 CFR 338.50 - Labeling of nighttime sleep-aid drug products.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 5 2012-04-01 2012-04-01 false Labeling of nighttime sleep-aid drug products. 338... SERVICES (CONTINUED) DRUGS FOR HUMAN USE NIGHTTIME SLEEP-AID DRUG PRODUCTS FOR OVER-THE-COUNTER HUMAN USE Labeling § 338.50 Labeling of nighttime sleep-aid drug products. (a) Statement of identity. The labeling...

  18. 21 CFR 338.50 - Labeling of nighttime sleep-aid drug products.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 5 2010-04-01 2010-04-01 false Labeling of nighttime sleep-aid drug products. 338... SERVICES (CONTINUED) DRUGS FOR HUMAN USE NIGHTTIME SLEEP-AID DRUG PRODUCTS FOR OVER-THE-COUNTER HUMAN USE Labeling § 338.50 Labeling of nighttime sleep-aid drug products. (a) Statement of identity. The labeling...

  19. 21 CFR 338.50 - Labeling of nighttime sleep-aid drug products.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 5 2014-04-01 2014-04-01 false Labeling of nighttime sleep-aid drug products. 338... SERVICES (CONTINUED) DRUGS FOR HUMAN USE NIGHTTIME SLEEP-AID DRUG PRODUCTS FOR OVER-THE-COUNTER HUMAN USE Labeling § 338.50 Labeling of nighttime sleep-aid drug products. (a) Statement of identity. The labeling...

  20. 21 CFR 338.50 - Labeling of nighttime sleep-aid drug products.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 5 2011-04-01 2011-04-01 false Labeling of nighttime sleep-aid drug products. 338... SERVICES (CONTINUED) DRUGS FOR HUMAN USE NIGHTTIME SLEEP-AID DRUG PRODUCTS FOR OVER-THE-COUNTER HUMAN USE Labeling § 338.50 Labeling of nighttime sleep-aid drug products. (a) Statement of identity. The labeling...

  1. 21 CFR 338.10 - Nighttime sleep-aid active ingredients.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 5 2012-04-01 2012-04-01 false Nighttime sleep-aid active ingredients. 338.10... (CONTINUED) DRUGS FOR HUMAN USE NIGHTTIME SLEEP-AID DRUG PRODUCTS FOR OVER-THE-COUNTER HUMAN USE Active Ingredients § 338.10 Nighttime sleep-aid active ingredients. The active ingredient of the product consists...

  2. 21 CFR 338.10 - Nighttime sleep-aid active ingredients.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 5 2011-04-01 2011-04-01 false Nighttime sleep-aid active ingredients. 338.10... (CONTINUED) DRUGS FOR HUMAN USE NIGHTTIME SLEEP-AID DRUG PRODUCTS FOR OVER-THE-COUNTER HUMAN USE Active Ingredients § 338.10 Nighttime sleep-aid active ingredients. The active ingredient of the product consists...

  3. 21 CFR 338.10 - Nighttime sleep-aid active ingredients.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 5 2014-04-01 2014-04-01 false Nighttime sleep-aid active ingredients. 338.10... (CONTINUED) DRUGS FOR HUMAN USE NIGHTTIME SLEEP-AID DRUG PRODUCTS FOR OVER-THE-COUNTER HUMAN USE Active Ingredients § 338.10 Nighttime sleep-aid active ingredients. The active ingredient of the product consists...

  4. 21 CFR 338.10 - Nighttime sleep-aid active ingredients.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 5 2013-04-01 2013-04-01 false Nighttime sleep-aid active ingredients. 338.10... (CONTINUED) DRUGS FOR HUMAN USE NIGHTTIME SLEEP-AID DRUG PRODUCTS FOR OVER-THE-COUNTER HUMAN USE Active Ingredients § 338.10 Nighttime sleep-aid active ingredients. The active ingredient of the product consists...

  5. 21 CFR 338.50 - Labeling of nighttime sleep-aid drug products.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 5 2013-04-01 2013-04-01 false Labeling of nighttime sleep-aid drug products. 338... SERVICES (CONTINUED) DRUGS FOR HUMAN USE NIGHTTIME SLEEP-AID DRUG PRODUCTS FOR OVER-THE-COUNTER HUMAN USE Labeling § 338.50 Labeling of nighttime sleep-aid drug products. (a) Statement of identity. The labeling...

  6. Evidence-based modelling of diverse plant water use strategies on stomatal and non-stomatal components under drought

    NASA Astrophysics Data System (ADS)

    zhou, S.; Prentice, C.; Medlyn, B. E.; Sabaté, S.

    2013-12-01

    Models disagree on how to represent effects of drought stress on plant gas exchange. Some models assume drought stress affects the marginal water use efficiency of plants (marginal WUE; i.e. the change in photosynthesis per unit of change in transpiration) whereas others assume drought stress acts directly on photosynthetic capacity. It is not clear whether either of these approaches is sufficient to capture the drought response, or whether the effect of drought varies among species and functional types. A collection of Eucalyptus and Quercus species derived from different hydro-climate habitats, in together with two European riparian species, were conducted with drought treatments respectively in Australia and Spain for three months. Measurements included net CO2 assimilation rate versus substomatal CO2 concentration (A-Ci) curves, fluorescence, and predawn leaf water potential at increasing levels of water stress. The correlations with quantitative plant traits of leaf, stomata, vessel, and wood density, leaf nitrogen content and 13C discrimination were also explored. We analysed the effect of drought effect on leaf gas exchange with a recently developed stomatal model that reconciles the empirical and optimal approaches on predicting optimal stomatal conductance. The model's single parameter g1 is a decreasing function of marginal WUE. The two genera showed consistence on the contrasting response patterns between species derived from mesic and arid habitats, which differed greatly in their estimated g1 values under moist conditions, and in the rate at which g1 declined with water stress. They also differed greatly in the predawn water potential at which apparent carboxylation capacity (apparent Vcmax) and mesophyll conductance (gm) declined most steeply, and in the steepness of this decline. Principal components analysis revealed a gradient in water relation strategies from sclerophyll species to malacophyll species. Malacophylls had higher g1, apparent Vcmax

  7. Stomatal crypts have small effects on transpiration: a numerical model analysis.

    PubMed

    Roth-Nebelsick, Anita; Hassiotou, Foteini; Veneklaas, Erik J

    2009-12-01

    Stomata arranged in crypts with trichomes are commonly considered to be adaptations to aridity due to the additional diffusion resistance associated with this arrangement; however, information on the effect of crypts on gas exchange, relative to stomata, is sparse. In this study, three-dimensional Finite Element models of encrypted stomata were generated using commercial Computational Fluid Dynamics software. The models were based on crypt and stomatal architectural characteristics of the species Banksia ilicifolia, examined microscopically, and variations thereof. In leaves with open or partially closed stomata, crypts reduced transpiration by less than 15% compared with nonencrypted, superficially positioned stomata. A larger effect of crypts was found only in models with unrealistically high stomatal conductances. Trichomes inside the crypt had virtually no influence on transpiration. Crypt conductance varied with stomatal conductance, boundary layer conductance, and ambient relative humidity, as these factors modified the three-dimensional diffusion patterns inside crypts. It was concluded that it is unlikely that the primary function of crypts and crypt trichomes is to reduce transpiration. PMID:19864375

  8. Stomatal Crypts Have Small Effects on Transpiration: A Numerical Model Analysis1

    PubMed Central

    Roth-Nebelsick, Anita; Hassiotou, Foteini; Veneklaas, Erik J.

    2009-01-01

    Stomata arranged in crypts with trichomes are commonly considered to be adaptations to aridity due to the additional diffusion resistance associated with this arrangement; however, information on the effect of crypts on gas exchange, relative to stomata, is sparse. In this study, three-dimensional Finite Element models of encrypted stomata were generated using commercial Computational Fluid Dynamics software. The models were based on crypt and stomatal architectural characteristics of the species Banksia ilicifolia, examined microscopically, and variations thereof. In leaves with open or partially closed stomata, crypts reduced transpiration by less than 15% compared with nonencrypted, superficially positioned stomata. A larger effect of crypts was found only in models with unrealistically high stomatal conductances. Trichomes inside the crypt had virtually no influence on transpiration. Crypt conductance varied with stomatal conductance, boundary layer conductance, and ambient relative humidity, as these factors modified the three-dimensional diffusion patterns inside crypts. It was concluded that it is unlikely that the primary function of crypts and crypt trichomes is to reduce transpiration. PMID:19864375

  9. Treatment of recurrent aphthous stomatitis. A literature review

    PubMed Central

    Jiménez-Soriano, Yolanda; Claramunt-Lozano, Ariadna

    2014-01-01

    Recurrent aphthous stomatitis (RAS) is the most common chronic disease of the oral cavity, affecting 5-25% of the population. The underlying etiology remains unclear, and no curative treatment is available. The present review examines the existing treatments for RAS with the purpose of answering a number of questions: How should these patients be treated in the dental clinic? What topical drugs are available and when should they be used? What systemic drugs are available and when should they be used? A literature search was made of the PubMed, Cochrane and Scopus databases, limited to articles published between 2008-2012, with scientific levels of evidence 1 and 2 (metaanalyses, systematic reviews, phase I and II randomized clinical trials, cohort studies and case-control studies), and conducted in humans. The results obtained indicate that the management of RAS should be based on identification and control of the possible predisposing factors, with the exclusion of possible underlying systemic causes, and the use of a detailed clinical history along with complementary procedures such as laboratory tests, where required. Only in the case of continuous outbreaks and symptoms should drug treatment be prescribed, with the initial application of local treatments in all cases. A broad range of topical medications are available, including antiseptics (chlorhexidine), antiinflammatory drugs (amlexanox), antibiotics (tetracyclines) and corticosteroids (triamcinolone acetonide). In patients with constant and aggressive outbreaks (major aphthae), pain is intense and topical treatment is unable to afford symptoms relief. Systemic therapy is indicated in such situations, in the form of corticosteroids (prednisone) or thalidomide, among other drugs. Key words:Recurrent aphthous stomatitis, treatment, clinical management. PMID:24790718

  10. Acidic mist reduces foliar membrane-associated calcium and impairs stomatal responsiveness in red spruce.

    PubMed

    Borer, Catherine H; Schaberg, Paul G; DeHayes, Donald H

    2005-06-01

    Acidic deposition can leach essential pools of calcium (Ca) directly from plant foliage. Because of the central role of Ca in environmental signal transduction, disruptions of labile foliar Ca pools could impair physiological responses to a variety of environmental stimuli and stressors. We investigated the possibility that acidic mist-induced depletion of membrane-associated Ca (mCa), which is one form of labile Ca, may alter stomatal responsiveness to water stress, a process known to include Ca in signal transduction cascades. Red spruce (Picea rubens Sarg.) seedlings were exposed to either pH 3.0 or pH 5.0 mist treatments for one growing season. Foliar nutrition was assessed following treatments, and declines in stomatal conductance and net photosynthesis were measured on current-year shoots following stem excision. Seedlings exposed to pH 3.0 acidic mist treatments had reduced mCa relative to the pH 5.0 treated seedlings. Seedlings subjected to the pH 3.0 acidic mist treatment exhibited impaired stomatal functions, including a smaller maximum aperture, slower closure and an increased lag time between stomatal closure and photosynthetic decline following experimental water stress. Delayed stomatal closure could undermine desiccation avoidance mechanisms. Previous work has demonstrated that acidic mist treatments deplete mCa in red spruce and impair cold tolerance, with similar effects in other species. The results we present provide further evidence that acidic mist-induced mCa depletion may cause disruption of a broad range of plant stress responses.

  11. Effects of leaf wetting and high humidity on stomatal function in leafy cuttings and intact plants of Corylus maxima.

    PubMed

    Fordham, Michael C.; Harrison-Murray, Richard S.; Knight, Linda; Evered, Carol E.

    2001-10-01

    When rooted cuttings of Corylus maxima Mill. cv. Purpurea are moved from the wet and humid conditions of the rooting environment, the leaves frequently shrivel and die. Since the newly formed adventitious root system has been shown to be functional in supplying water to the shoot, stomatal behaviour in C. maxima was investigated in relation to the failure to prevent desiccation. Stomatal conductance (gs) in expanding leaves (L3) of cuttings increased almost 10-fold over the first 14 days in the rooting environment (fog), from 70 to 650 mmol m-2 s-1. In contrast, gs of expanded leaves (L1) changed little and was in the region of 300 mmol m-2 s-1. Midday leaf water potential was much higher in cuttings than in leaves on the mother stock-plant (-0.5 versus -1.2 MPa) even before any roots were visible. Despite this, leaf expansion of L3 was inhibited by >50% in cuttings and stomata showed a gradual reduction in their ability to close in response to abscisic acid (ABA). To determine whether the loss of stomatal function in cuttings was due to severance or to unnaturally low vapour pressure deficit and wetting in fog, intact plants were placed alongside cuttings in the rooting environment. The intact plants displayed reductions in leaf expansion and in the ability of stomata to close in response to dark, desiccation and ABA. However, in cuttings, the additional effect of severance resulted in smaller leaves than in intact plants and more severe reduction in stomatal closure, which was associated with a 2.5-fold increase in stomatal density and distinctively rounded stomatal pores. The similarities between stomatal dysfunction in C. maxima and that observed in many species propagated in vitro are discussed, as is the possible mechanism of dysfunction. PMID:12060301

  12. Equatorial Enhancement of the Nighttime OH Mesospheric Infrared Airglow

    NASA Technical Reports Server (NTRS)

    Baker, D. J.; Mlynczak, M. G.; Russell, J. M.

    2007-01-01

    Global measurements of the hydroxyl mesospheric airglow over an extended period of time have been made possible by the NASA SABER infrared sensor aboard the TIMED satellite which has been functioning since December of 2001. The orbital mission has continued over a significant portion of a solar cycle. Experimental data from SABER for several years have exhibited equatorial enhancements of the nighttime mesospheric OH (delta v = 2) airglow layer consistent with the high average diurnal solar flux. The brightening of the OH airglow typically means more H + O3 is being reacted. At both the spring and autumn seasonal equinoxes when the equatorial solar UV irradiance mean is greatest, the peak volume emission rate (VER) of the nighttime Meinel infrared airglow typically appears to be both significantly brighter plus lower in altitude by several kilometres at low latitudes compared with midlatitude findings.

  13. Vision-based multiple vehicle detection and tracking at nighttime

    NASA Astrophysics Data System (ADS)

    Xu, Wencong; Liu, Hai

    2011-08-01

    In this paper, we develop a robust vision-based approach for real-time traffic data collection at nighttime. The proposed algorithm detects and tracks vehicles through detection and location of vehicle headlights. First, we extract headlights candidates by an adaptive image segmentation algorithm. Then we group headlights candidates that belong to the same vehicle by spatial clustering and generate vehicle hypotheses by rule-based reasoning. The potential vehicles are then tracked over frames by region search and pattern analysis methods. The spatial and temporal continuity extracted from tracking process is used to confirm vehicle's presence. To handle problem of occlusions, we apply Kalman Filter to motion estimation. We test the algorithm on the video clips of nighttime traffic under different conditions. The experimental results show that real-time vehicle counting and tacking for multi-lanes are achieved and the total detection rate is above 96%.

  14. Relationships between brightness of nighttime lights and population density

    NASA Astrophysics Data System (ADS)

    Naizhuo, Z.

    2012-12-01

    Brightness of nighttime lights has been proven to be a good proxy for socioeconomic and demographic statistics. Moreover, the satellite nighttime lights data have been used to spatially disaggregate amounts of gross domestic product (GDP), fossil fuel carbon dioxide emission, and electric power consumption (Ghosh et al., 2010; Oda and Maksyutov, 2011; Zhao et al., 2012). Spatial disaggregations were performed in these previous studies based on assumed linear relationships between digital number (DN) value of pixels in the nighttime light images and socioeconomic data. However, reliability of the linear relationships was never tested due to lack of relative high-spatial-resolution (equal to or finer than 1 km × 1 km) statistical data. With the similar assumption that brightness linearly correlates to population, Bharti et al. (2011) used nighttime light data as a proxy for population density and then developed a model about seasonal fluctuations of measles in West Africa. The Oak Ridge National Laboratory used sub-national census population data and high spatial resolution remotely-sensed-images to produce LandScan population raster datasets. The LandScan population datasets have 1 km × 1 km spatial resolution which is consistent with the spatial resolution of the nighttime light images. Therefore, in this study I selected 2008 LandScan population data as baseline reference data and the contiguous United State as study area. Relationships between DN value of pixels in the 2008 Defense Meteorological Satellite Program's Operational Linescan System (DMSP-OLS) stable light image and population density were established. Results showed that an exponential function can more accurately reflect the relationship between luminosity and population density than a linear function. Additionally, a certain number of saturated pixels with DN value of 63 exist in urban core areas. If directly using the exponential function to estimate the population density for the whole brightly

  15. The ecological impacts of nighttime light pollution: a mechanistic appraisal.

    PubMed

    Gaston, Kevin J; Bennie, Jonathan; Davies, Thomas W; Hopkins, John

    2013-11-01

    The ecological impacts of nighttime light pollution have been a longstanding source of concern, accentuated by realized and projected growth in electrical lighting. As human communities and lighting technologies develop, artificial light increasingly modifies natural light regimes by encroaching on dark refuges in space, in time, and across wavelengths. A wide variety of ecological implications of artificial light have been identified. However, the primary research to date is largely focused on the disruptive influence of nighttime light on higher vertebrates, and while comprehensive reviews have been compiled along taxonomic lines and within specific research domains, the subject is in need of synthesis within a common mechanistic framework. Here we propose such a framework that focuses on the cross-factoring of the ways in which artificial lighting alters natural light regimes (spatially, temporally, and spectrally), and the ways in which light influences biological systems, particularly the distinction between light as a resource and light as an information source. We review the evidence for each of the combinations of this cross-factoring. As artificial lighting alters natural patterns of light in space, time and across wavelengths, natural patterns of resource use and information flows may be disrupted, with downstream effects to the structure and function of ecosystems. This review highlights: (i) the potential influence of nighttime lighting at all levels of biological organisation (from cell to ecosystem); (ii) the significant impact that even low levels of nighttime light pollution can have; and (iii) the existence of major research gaps, particularly in terms of the impacts of light at population and ecosystem levels, identification of intensity thresholds, and the spatial extent of impacts in the vicinity of artificial lights.

  16. Diverse stomatal signaling and the signal integration mechanism.

    PubMed

    Murata, Yoshiyuki; Mori, Izumi C; Munemasa, Shintaro

    2015-01-01

    Guard cells perceive a variety of chemicals produced metabolically in response to abiotic and biotic stresses, integrate the signals into reactive oxygen species and calcium signatures, and convert these signatures into stomatal movements by regulating turgor pressure. Guard cell behaviors in response to such complex signals are critical for plant growth and sustenance in stressful, ever-changing environments. The key open question is how guard cells achieve the signal integration to optimize stomatal aperture. Abscisic acid is responsible for stomatal closure in plants in response to drought, and its signal transduction has been well studied. Other plant hormones and low-molecular-weight compounds function as inducers of stomatal closure and mediators of signaling in guard cells. In this review, we summarize recent advances in research on the diverse stomatal signaling pathways, with specific emphasis on signal integration and signal interaction in guard cell movement.

  17. In situ stomatal responses to long-term CO 2 enrichment in calcareous grassland plants

    NASA Astrophysics Data System (ADS)

    Lauber, Wolfgang; Körner, Christian

    A calcareous grassland community growing under full season CO 2 enrichment at low altitude in the Swiss Jura mountains was investigated for diurnal and seasonal variations of leaf diffusive conductance. A new CO 2 enrichment method (Screen aided CO 2 control, SACC) permitted in situ leaf porometry under natural climatic conditions without disturbance of plants. At 600 ppm CO 2, leaf conductance in the dominant species, Bromus erectus (a species so far not showing a growth response to elevated CO 2) was reduced to half the values measured in controls. In contrast, leaf conductance in Carex flacca, a species of low cover (the only species so far exhibiting a dramatic growth stimulation by CO 2 fertilization) remained almost unaffected by elevated CO 2. Sanguisorba minor, Plantago media, and Cirsium acaule showed intermediate responses. Trifolium montanum, studied only on a single day, showed a reduction like Bromus. Differences between treatments were largest under humid conditions and disappeared during dry periods. In none of the species studied did stomatal density or stomatal index differ between treatments. A parallel investigation of whole ecosystem evapotranspiration indicated only small (<10%) and non significant CO 2 responses, suggesting that both aerodynamic effects at the canopy level and a great interspecific variation of leaf level responses overshadow the clear CO 2 response of Bromus stomata. The different stomatal responses to CO 2 enrichment are likely to alter species specific water consumption, and may thus affect community structure in the long run.

  18. Nighttime Lights, Socioeconomic Development, and Revitalization Policies in Northeast Asia

    NASA Astrophysics Data System (ADS)

    Bennett, M.; Smith, L. C.

    2015-12-01

    Nighttime lights are typically used as a proxy for population and economic growth, yet they can also reveal socioeconomic decline. We use two night light datasets to infer socioeconomic patterns and trends in the Russian Far East, Northeast China, and North Korea, a cross-border region impacted by the 1991 collapse of the USSR. First, using the annual stable light composites from the DMSP/OLS satellites, we find that generally, nighttime lights declined in the Russian Far East, increased in Northeast China, and fluctuated in North Korea between 1992 and 2012. By 2012, lighting in most of the Russian Far East had not recovered to 1992 levels. In Northeast China, a government revitalization program may have increased lighting during the mid-2000s, suggesting sensitivity of remotely sensed nighttime lights to regional development policies. Yet caveats with DMSP/OLS data include low spatial and radiometric resolutions, saturation, and blooming. The Day/Night Band (DNB) of the Suomi NPP satellite, however, launched in October 2011, has higher quality, enabling improved monitoring of socioeconomic trends in the region. For our second night lights dataset, we use both nightly images and monthly DNB composites to make inferences regarding socioeconomic activities at finer spatial and temporal resolutions from 2012-2015. Cross-border activity in particular emerges in finer detail, allowing us to examine specific transport corridors and sites of industrial and natural resource production that involve both Russian and Chinese partners.

  19. Stomatal Spacing Safeguards Stomatal Dynamics by Facilitating Guard Cell Ion Transport Independent of the Epidermal Solute Reservoir.

    PubMed

    Papanatsiou, Maria; Amtmann, Anna; Blatt, Michael R

    2016-09-01

    Stomata enable gaseous exchange between the interior of the leaf and the atmosphere through the stomatal pore. Control of the pore aperture depends on osmotic solute accumulation by, and its loss from the guard cells surrounding the pore. Stomata in most plants are separated by at least one epidermal cell, and this spacing is thought to enhance stomatal function, although there are several genera that exhibit stomata in clusters. We made use of Arabidopsis (Arabidopsis thaliana) stomatal patterning mutants to explore the impact of clustering on guard cell dynamics, gas exchange, and ion transport of guard cells. These studies showed that stomatal clustering in the Arabidopsis too many mouths (tmm1) mutant suppressed stomatal movements and affected CO2 assimilation and transpiration differentially between dark and light conditions and were associated with alterations in K(+) channel gating. These changes were consistent with the impaired dynamics of tmm1 stomata and were accompanied by a reduced accumulation of K(+) ions in the guard cells. Our findings underline the significance of spacing for stomatal dynamics. While stomatal spacing may be important as a reservoir for K(+) and other ions to facilitate stomatal movements, the effects on channel gating, and by inference on K(+) accumulation, cannot be explained on the basis of a reduced number of epidermal cells facilitating ion supply to the guard cells. PMID:27406168

  20. Stomatal Spacing Safeguards Stomatal Dynamics by Facilitating Guard Cell Ion Transport Independent of the Epidermal Solute Reservoir12[OPEN

    PubMed Central

    Papanatsiou, Maria; Amtmann, Anna

    2016-01-01

    Stomata enable gaseous exchange between the interior of the leaf and the atmosphere through the stomatal pore. Control of the pore aperture depends on osmotic solute accumulation by, and its loss from the guard cells surrounding the pore. Stomata in most plants are separated by at least one epidermal cell, and this spacing is thought to enhance stomatal function, although there are several genera that exhibit stomata in clusters. We made use of Arabidopsis (Arabidopsis thaliana) stomatal patterning mutants to explore the impact of clustering on guard cell dynamics, gas exchange, and ion transport of guard cells. These studies showed that stomatal clustering in the Arabidopsis too many mouths (tmm1) mutant suppressed stomatal movements and affected CO2 assimilation and transpiration differentially between dark and light conditions and were associated with alterations in K+ channel gating. These changes were consistent with the impaired dynamics of tmm1 stomata and were accompanied by a reduced accumulation of K+ ions in the guard cells. Our findings underline the significance of spacing for stomatal dynamics. While stomatal spacing may be important as a reservoir for K+ and other ions to facilitate stomatal movements, the effects on channel gating, and by inference on K+ accumulation, cannot be explained on the basis of a reduced number of epidermal cells facilitating ion supply to the guard cells. PMID:27406168

  1. Stomatal Spacing Safeguards Stomatal Dynamics by Facilitating Guard Cell Ion Transport Independent of the Epidermal Solute Reservoir.

    PubMed

    Papanatsiou, Maria; Amtmann, Anna; Blatt, Michael R

    2016-09-01

    Stomata enable gaseous exchange between the interior of the leaf and the atmosphere through the stomatal pore. Control of the pore aperture depends on osmotic solute accumulation by, and its loss from the guard cells surrounding the pore. Stomata in most plants are separated by at least one epidermal cell, and this spacing is thought to enhance stomatal function, although there are several genera that exhibit stomata in clusters. We made use of Arabidopsis (Arabidopsis thaliana) stomatal patterning mutants to explore the impact of clustering on guard cell dynamics, gas exchange, and ion transport of guard cells. These studies showed that stomatal clustering in the Arabidopsis too many mouths (tmm1) mutant suppressed stomatal movements and affected CO2 assimilation and transpiration differentially between dark and light conditions and were associated with alterations in K(+) channel gating. These changes were consistent with the impaired dynamics of tmm1 stomata and were accompanied by a reduced accumulation of K(+) ions in the guard cells. Our findings underline the significance of spacing for stomatal dynamics. While stomatal spacing may be important as a reservoir for K(+) and other ions to facilitate stomatal movements, the effects on channel gating, and by inference on K(+) accumulation, cannot be explained on the basis of a reduced number of epidermal cells facilitating ion supply to the guard cells.

  2. Influence of light exposure at nighttime on sleep development and body growth of preterm infants.

    PubMed

    Kaneshi, Yosuke; Ohta, Hidenobu; Morioka, Keita; Hayasaka, Itaru; Uzuki, Yutaka; Akimoto, Takuma; Moriichi, Akinori; Nakagawa, Machiko; Oishi, Yoshihisa; Wakamatsu, Hisanori; Honma, Naoki; Suma, Hiroki; Sakashita, Ryuichi; Tsujimura, Sei-ichi; Higuchi, Shigekazu; Shimokawara, Miyuki; Cho, Kazutoshi; Minakami, Hisanori

    2016-02-15

    Previous studies have demonstrated that a light-dark cycle has promoted better sleep development and weight gain in preterm infants than constant light or constant darkness. However, it was unknown whether brief light exposure at night for medical treatment and nursing care would compromise the benefits brought about by such a light-dark cycle. To examine such possibility, we developed a special red LED light with a wavelength of >675 nm which preterm infants cannot perceive. Preterm infants born at <36 weeks' gestational age were randomly assigned for periodic exposure to either white or red LED light at night in a light-dark cycle after transfer from the Neonatal Intensive Care Unit to the Growing Care Unit, used for supporting infants as they mature. Activity, nighttime crying and body weight were continuously monitored from enrolment until discharge. No significant difference in rest-activity patterns, nighttime crying, or weight gain was observed between control and experimental groups. The data indicate that nursing care conducted at 3 to 4-hour intervals exposing infants to light for <15 minutes does not prevent the infants from developing circadian rest-activity patterns, or proper body growth as long as the infants are exposed to regular light-dark cycles.

  3. Influence of light exposure at nighttime on sleep development and body growth of preterm infants

    PubMed Central

    Kaneshi, Yosuke; Ohta, Hidenobu; Morioka, Keita; Hayasaka, Itaru; Uzuki, Yutaka; Akimoto, Takuma; Moriichi, Akinori; Nakagawa, Machiko; Oishi, Yoshihisa; Wakamatsu, Hisanori; Honma, Naoki; Suma, Hiroki; Sakashita, Ryuichi; Tsujimura, Sei-ichi; Higuchi, Shigekazu; Shimokawara, Miyuki; Cho, Kazutoshi; Minakami, Hisanori

    2016-01-01

    Previous studies have demonstrated that a light-dark cycle has promoted better sleep development and weight gain in preterm infants than constant light or constant darkness. However, it was unknown whether brief light exposure at night for medical treatment and nursing care would compromise the benefits brought about by such a light-dark cycle. To examine such possibility, we developed a special red LED light with a wavelength of >675 nm which preterm infants cannot perceive. Preterm infants born at <36 weeks’ gestational age were randomly assigned for periodic exposure to either white or red LED light at night in a light-dark cycle after transfer from the Neonatal Intensive Care Unit to the Growing Care Unit, used for supporting infants as they mature. Activity, nighttime crying and body weight were continuously monitored from enrolment until discharge. No significant difference in rest-activity patterns, nighttime crying, or weight gain was observed between control and experimental groups. The data indicate that nursing care conducted at 3 to 4-hour intervals exposing infants to light for <15 minutes does not prevent the infants from developing circadian rest-activity patterns, or proper body growth as long as the infants are exposed to regular light-dark cycles. PMID:26877166

  4. Nighttime Ground and Space Based Ionospheric Measurements in Support of FORMOSAT- 3/COSMIC

    NASA Astrophysics Data System (ADS)

    Basu, S.; Groves, K.; Lin, C.; Dymond, K.; Coker, C.; Rocken, C.; Valladares, C.

    2006-12-01

    Coordinated multi-technique measurements were conducted in support of COSMIC launched in April 2006. These early measurements were organized to take advantage of the clustering of satellites in the constellation generally referred to as "beads on string" configuration. This configuration only occurs during the early phase when the satellites are around the launch altitude, approximately 500 km, before they are finally deployed at 800 km altitude. This clustered configuration permits measurements with high spatial and temporal resolution from all three COSMIC instruments, namely, the GPS occultation sensor (GOX), the Tiny Ionospheric Photometer (TIP) and the radio beacon. The main advantage of this constellation is that the coverage in latitude and longitude is unprecedented. The TIP observations of nighttime 135.6 nm emission provide the features of the equatorial anomaly, namely the ionization density at the crests, the crest to trough density ratio, the latitude separation of the crests and their asymmetry. The GOX sensor is able to provide accurate electron density profiles in the equatorial anomaly region at dusk by the assimilation of TIP data on density gradients. Major ground-based support was provided by incoherent scatter radars at Jicamarca and Kwajalein, the TEC network in the South American sector and scintillation measurements from nearby SCINDA sites. These early results on large and small-scale plasma structuring in the nighttime equatorial ionosphere will be presented.

  5. Attenuated Vesicular Stomatitis Viruses as Vaccine Vectors

    PubMed Central

    Roberts, Anjeanette; Buonocore, Linda; Price, Ryan; Forman, John; Rose, John K.

    1999-01-01

    We showed previously that a single intranasal vaccination of mice with a recombinant vesicular stomatitis virus (VSV) expressing an influenza virus hemagglutinin (HA) protein provided complete protection from lethal challenge with influenza virus (A. Roberts, E. Kretzschmar, A. S. Perkins, J. Forman, R. Price, L. Buonocore, Y. Kawaoka, and J. K. Rose, J. Virol. 72:4704–4711, 1998). Because some pathogenesis was associated with the vector itself, in the present study we generated new VSV vectors expressing HA which are completely attenuated for pathogenesis in the mouse model. The first vector has a truncation of the cytoplasmic domain of the VSV G protein and expresses influenza virus HA (CT1-HA). This nonpathogenic vector provides complete protection from lethal influenza virus challenge after intranasal administration. A second vector with VSV G deleted and expressing HA (ΔG-HA) is also protective and nonpathogenic and has the advantage of not inducing neutralizing antibodies to the vector itself. PMID:10196265

  6. Smokeless tobacco use prevents aphthous stomatitis.

    PubMed

    Grady, D; Ernster, V L; Stillman, L; Greenspan, J

    1992-10-01

    Aphthous stomatitis is a common, recurrent, painful ulcerative condition of the oral mucosa. Cigarette smoking has been reported to protect against aphthous ulcers. To determine whether smokeless tobacco use also protects against aphthous ulcers, we examined the oral mucosa in 1456 professional baseball players, about half of whom were smokeless tobacco (ST) users. After controlling for the confounding effects of age, race, cigarette smoking, alcohol consumption, and dental hygiene practices, ST use was found to significantly reduce the risk of aphthous ulcers among these healthy young men (odds ratio = 0.4; p = 0.04). It has been suggested that cigarette smoking prevents aphthous ulcers by causing increased keratinization of the oral mucosa, and ST may protect by the same mechanism. Alternatively, a component of tobacco that is systemically absorbed might be responsible for protecting against aphthous ulcers. If the mechanism that protects ST users against aphthous ulcers is systemic, then nicotine is the likely protective factor.

  7. Biophysical studies of vesicular stomatitis virus.

    PubMed

    McCombs, R M; Melnick, M B; Brunschwig, J P

    1966-02-01

    McCombs, Robert M. (Baylor University College of Medicine, Houston, Tex.), Matilda Benyesh-Melnick, and Jean P. Brunschwig. Biophysical studies of vesicular stomatitis virus: J. Bacteriol. 91:803-812. 1966.-The infectivity and morphology of vesicular stomatitis virus (VSV) were studied after density gradient centrifugation in cesium chloride (CsCI), potassium tartrate (KT), and sucrose. Centrifugation in CsCl revealed two equally infectious bands corresponding to densities of 1.19 and 1.22 g/ml, and a third (density, 1.26 g/ml) band of low infectivity. Two bands (densities of 1.16 and 1.18 g/ml) were observed in the KT gradient, in which the lighter band contained most of the infectivity. Centrifugation in sucrose resulted in a single broad infectious band (density, 1.16 g/ml). The typical rod-shaped VSV particles were found mainly in the lighter bands obtained in CsCl (1.19 g/ml) and KT (1.16 g/ml) and in the single sucrose gradient band (1.16 g/ml). Bent particles equally as infectious as the rod-shaped particles were a constant finding in the CsCl preparations, and were observed mainly in the second band (density, 1.19 g). Numerous strands 15mmu wide were found in the third CsCl (density, 1.26 g/ml) and the second KT (1.18 g/ml) bands. Similar strands could be liberated from VSV particles after treatment with deoxycholate. Internal transverse striations were found to be a regular feature of VSV particles examined with the pseudoreplication negative-staining technique. For crude virus stocks, the physical particle-to-infectivity ratio ranged from 73 to 194. Several morphological similarities between VSV and myxoviruses were observed, including 10 mmu surface projections, pleomorphic morphological forms, and 15 mmu seemingly nucleoprotein strands.

  8. Allyl isothiocyanate induces stomatal closure in Vicia faba.

    PubMed

    Sobahan, Muhammad Abdus; Akter, Nasima; Okuma, Eiji; Uraji, Misugi; Ye, Wenxiu; Mori, Izumi C; Nakamura, Yoshimasa; Murata, Yoshiyuki

    2015-01-01

    Isothiocyanates are enzymatically produced from glucosinolates in plants, and allyl isothiocyanate (AITC) induces stomatal closure in Arabidopsis thaliana. In this study, we investigated stomatal responses to AITC in Vicia faba. AITC-induced stomatal closure accompanied by reactive oxygen species (ROS) and NO production, cytosolic alkalization and glutathione (GSH) depletion in V. faba. GSH monoethyl ester induced stomatal reopening and suppressed AITC-induced GSH depletion in guard cells. Exogenous catalase and a peroxidase inhibitor, salicylhydroxamic acid, inhibited AITC-induced stomatal closure, unlike an NAD(P)H oxidase inhibitor, diphenylene iodonium chloride. The peroxidase inhibitor also abolished the AITC-induced ROS production, NO production, and cytosolic alkalization. AITC-induced stomatal closure was suppressed by an NO scavenger, 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide, and an agent to acidify cytosol, butyrate. These results indicate that AITC-induced stomatal closure in V. faba as well as in A. thaliana and suggest that AITC signaling in guard cells is conserved in both plants.

  9. Isolation of the envelope of vesicular stomatitis virus.

    PubMed Central

    Taube, S E; Rothfield, L I

    1978-01-01

    Vesicular stomatitis virus was disrupted by a combination of freezing and thawing, osmotic shock, and sonic treatment. Subviral components were separated by isopycnic centrifugation. The low-density, lipid-rich fractions were pooled and shown to contain primarily viral glycoprotein. Further purification of this material resulted in the isolation of a preparation of vesicles which contained only the G protein and the same phospholipids as in the intact virions and exhibited spikelike structures similar to those on intact vesicular stomatitis virions. We conclude that we have isolated fragments of native vesicular stomatitis virus envelopes. Images PMID:209217

  10. Stomatal patchiness in Mediterranean evergreen sclerophylls : Phenomenology and consequences for the interpretation of the midday depression in photosynthesis and transpiration.

    PubMed

    Beyschlag, W; Pfanz, H; Ryel, R J

    1992-07-01

    Midday depression of net photosynthesis and transpiration in the Mediterranean sclerophylls Arbutus unedo L. and Quercus suber L. occurs with a depression of mesophyll photosynthetic activity as indicated by calculated carboxylation efficiency (CE) and constant diurnal calculated leaf intercellular partial pressure of CO2 (Ci). This work examines the hypothesis that this midday depression can be explained by the distribution of patches of either wide-open or closed stomata on the leaf surface, independent of a coupling mechanism between stomata and mesophyll that results in a midday depression of photosynthetic activity of the mesophyll. Pressure infiltration of four liquids differing in their surface tension was used as a method to show the occurrence of stomatal patchiness and to determine the status of stomatal aperture within the patches. Liquids were selected such that the threshold leaf conductance necessary for infiltration through the stomatal pores covered the expected diurnal range of calculated leaf conductance (g) for these species. Infiltration experiments were carried out with leaves of potted plants under simulated Mediterranean summer conditions in a growth chamber. For all four liquids, leaves of both species were found to be fully infiltratable in the morning and in the late afternoon while during the periods leading up to and away from midday the leaves showed a pronounced patchy distribution of infiltratable and non-infiltratable areas. Similar linear relationships between the amount of liquid infiltrated and g (measured by porometry prior to detachment and infiltration) for all liquids clearly revealed the existence of pneumatically isolated patches containing only wide-open or closed stomata. The good correspondence between the midday depression of CE, calculated under the assumption of no stomatal patchiness, and the diurnal changes in non-infiltratable leaf area strongly indicates that the apparent reduction in mesophyll activity results

  11. Characterization of Nighttime Light Variability Over the Southeastern United States

    NASA Technical Reports Server (NTRS)

    Cole, Tony A.; Molthan, Andrew L.; Schultz, Lori A.

    2016-01-01

    City lights provide indications of human activity at night. Nighttime satellite imagery offers daily snapshots of this activity. With calibrated, science-quality imagery, long-term monitoring can also be achieved. The degree to which city lights fluctuate, however, is not well known. For the application of detecting power outages, this degree of variability is crucial for assessing reductions to city lights based on historical trends. Eight southeastern U.S. cities are analyzed to understand the relationship between emission variability and several population centers. A preliminary, example case power outage study is also discussed as a transition into future work.

  12. Characterization of Nighttime Light Variability over the Southeastern United States

    NASA Astrophysics Data System (ADS)

    Cole, T.; Molthan, A.; Schultz, L. A.

    2015-12-01

    Severe meteorological events such as thunderstorms, tropical cyclones and winter ice storms often produce prolonged, widespread power outages affecting large populations and regions. The spatial impact of these events can extend from relatively rural, small towns (i.e. November 17, 2013 Washington, IL EF-4 tornado) to a series of adjoined states (i.e. April 27, 2011 severe weather outbreak) to entire regions (i.e. 2012 Hurricane Sandy) during their lifespans. As such, affected populations can vary greatly, depending on the event's intensity, location and duration. Actions taken by disaster response agencies like FEMA, the American Red Cross and NOAA to provide support to communities during the recovery process need accurate and timely information on the extent and location(s) of power disruption. This information is often not readily available to these agencies given communication interruptions, independent storm damage reports and other response-inhibiting factors. VIIRS DNB observations which provide daily, nighttime measurements of light sources can be used to detect and monitor power outages caused by these meteorological disaster events. To generate such an outage product, normal nighttime light variability must be analyzed and understood at varying spatial scales (i.e individual pixels, clustered land uses/covers, entire city extents). The southeastern portion of the United States serves as the study area in which the mean, median and standard deviation of nighttime lights are examined over numerous temporal periods (i.e. monthly, seasonally, annually, inter-annually). It is expected that isolated pixels with low population density (rural) will have tremendous variability in which an outage "signal" is difficult to detect. Small towns may have more consistent lighting (over a few pixels), making it easier to identify outages and reductions. Finally, large metropolitan areas may be the most "stable" light source, but the entire area may rarely experience a

  13. Passive nighttime warming facility for forest ecosystem research.

    PubMed

    Luxmoore, R. J.; Hanson, P. J.; Beauchamp, J. J.; Joslin, J. D.

    1998-01-01

    A nighttime warming experiment is proposed. Over the last four decades a significant rise in nighttime minimum temperature has been determined from analysis of meteorological records from a global distribution of locations. The experiment involves nighttime deployment of infrared (IR) reflecting curtains around four sides of a forest canopy and across the top of the forest to mimic the top-down warming effect of cloud cover. The curtains are deployed with cable and pulley systems mounted on a tower and scaffolding structure built around the selected forest site. The trunk space is not enclosed except as an optional manipulation. The curtains reflect long-wave radiation emitted from the forest and ground back into the forest warming the trees, litter, and soil. Excellent infrared reflection can be obtained with commercially available fabrics that have aluminum foil bonded to one side. A canopy warming of 3 to 5 degrees C is expected on cloudless nights, and on cloudy nights, a warming of 1 to 3 degrees C is anticipated relative to a control plot. The curtains are withdrawn by computer control during the day and also at night during periods with precipitation or excessive wind. Examples of hypothesized ecosystem responses to nighttime warming include: (1) increase in tree maintenance respiration (decreasing carbon reserves and ultimately tree growth), (2) increase in the length of the growing season (increasing growth), (3) increase in soil respiration, (4) increase in litter decomposition, (5) increase in mineralization of N and other nutrients from soil organic matter, (6) increase in nutrient uptake (increasing growth), and (7) increase in N immobilization in litter. Hypothesis 1 has the opposite consequence for tree growth to Hypotheses 2 and 6, and thus opposite consequences for the feedback regulation that vegetation has on net greenhouse gas releases to the atmosphere. If Hypothesis 1 is dominant, warming could lead to more warming from the additional CO(2

  14. A form of stomatitis induced by excessive peppermint consumption.

    PubMed

    Rogers, S N; Pahor, A L

    1995-01-01

    This paper reports on a form of stomatitis and glossitis associated with extremely prominent circumvalate papillae in two patients who consumed excessive amounts of mint-flavoured sweets. PMID:7664971

  15. Investigating Polyploidy: Using Marigold Stomates and Fingernail Polish.

    ERIC Educational Resources Information Center

    Hunter, Kimberly L.; Leone, Rebecca S.; Kohlhepp, Kimberly; Hunter, Richard B.

    2002-01-01

    Describes a science activity on polyploidy targeting middle and high school students which can be used to discuss topics such as chromosomes, cells, plant growth, and functions of stomates. Integrates mathematics in data collection. (Contains 13 references.) (YDS)

  16. Role of Sucrose in Emerging Mechanisms of Stomatal Aperture Regulation.

    SciTech Connect

    Outlaw, W. H.

    2000-09-15

    Focused on the second of 2 hypotheses that were proposed for testing that transpiration rate determines the extent to which suc accumulates in the GC wall providing a mechanism for regulating stomatal aperture size.

  17. Sleep quality and temperament among university students: differential associations with nighttime sleep duration and sleep disruptions.

    PubMed

    Lukowski, Angela F; Milojevich, Helen M

    2015-01-01

    Sleep-temperament associations have not yet been examined among university students, despite awareness of the high incidence of sleep problems in this population. The present study was conducted (a) to examine whether sleep quality was associated with temperament among university-attending young adults and (b) to determine whether particular components of sleep quality were differentially associated with temperament. University students completed questionnaires designed to assess sleep quality and temperament. Poor sleep quality was associated with increased negative affect and orienting sensitivity as well as decreased effortful control; regression analyses revealed differential associations between components of nighttime sleep quality and temperament ratings. The presented study reveals conceptual continuity in sleep-temperament relations from infancy to young adulthood and highlights important avenues for future research.

  18. Use of sap flow measurements to validate stomatal functions for mature beech (Fagus sylvatica) in view of ozone uptake calculations.

    PubMed

    Braun, Sabine; Schindler, Christian; Leuzinger, Sebastian

    2010-09-01

    For a quantitative estimate of the ozone effect on vegetation reliable models for ozone uptake through the stomata are needed. Because of the analogy of ozone uptake and transpiration it is possible to utilize measurements of water loss such as sap flow for quantification of ozone uptake. This technique was applied in three beech (Fagus sylvatica) stands in Switzerland. A canopy conductance was calculated from sap flow velocity and normalized to values between 0 and 1. It represents mainly stomatal conductance as the boundary layer resistance in forests is usually small. Based on this relative conductance, stomatal functions to describe the dependence on light, temperature, vapour pressure deficit and soil moisture were derived using multivariate nonlinear regression. These functions were validated by comparison with conductance values directly estimated from sap flow. The results corroborate the current flux parameterization for beech used in the DO3SE model.

  19. Testing a vapour-phase model of stomatal responses to humidity.

    PubMed

    Mott, Keith A; Peak, David

    2013-05-01

    This study tests two predictions from a recently proposed model for stomatal responses to humidity and temperature. The model is based on water potential equilibrium between the guard cells and the air at the bottom of the stomatal pore and contains three independent variables: gs(0), Z and Θ. gs(0) is the value of stomatal conductance that would occur at saturating humidity and will vary among leaves and with CO2 and light. The value of Z is determined primarily by the resistance to heat transfer from the epidermis to the evaporating site and the value of Θ is determined primarily by the resistance to water vapour diffusion from the evaporating site to the guard cells. This leads to the two predictions that were tested. Firstly, the values of Z and Θ should be constant for leaves of a given species grown under given conditions, although gs(0) should vary among leaves and with light and CO2. And secondly, the ratio of Z to Θ should be higher in leaves having their stomata in crypts because the distance for heat transfer is greater than that for water vapour diffusion. Data from three species, Nerium oleander, Pastinaca sativum and Xanthium strumarium support these two predictions. PMID:23072325

  20. Utilizing systems biology to unravel stomatal function and the hierarchies underpinning its control.

    PubMed

    Medeiros, David B; Daloso, Danilo M; Fernie, Alisdair R; Nikoloski, Zoran; Araújo, Wagner L

    2015-08-01

    Stomata control the concomitant exchange of CO2 and transpiration in land plants. While a constant supply of CO2 is need to maintain the rate of photosynthesis, the accompanying water losses must be tightly regulated to prevent dehydration and undesired metabolic changes. The factors affecting stomatal movement are directly coupled with the cellular networks of guard cells. Although the guard cell has been used as a model for characterization of signaling pathways, several important questions about its functioning remain elusive. Current modeling approaches describe the stomatal conductance in terms of relatively few easy-to-measure variables being unsuitable for in silico design of genetic manipulation strategies. Here, we argue that a system biology approach, combining modeling and high-throughput experiments, may be used to elucidate the mechanisms underlying stomata control and to determine targets for modulation of stomatal responses to environment. In support of our opinion, we review studies demonstrating how high-throughput approaches have provided a systems-view of guard cells. Finally, we emphasize the opportunities and challenges of genome-scale modeling and large-scale data integration for in silico manipulation of guard cell functions to improve crop yields, particularly under stress conditions which are of pertinence both to climate change and water use efficiency. PMID:25689387

  1. Simple relations for different stomatal control mechanisms link partially drying soil and transpiration

    NASA Astrophysics Data System (ADS)

    Huber, Katrin; Vanderborght, Jan; Javaux, Mathieu; Vereecken, Harry

    2015-04-01

    Stomata can close to regulate plant water loss under unfavourable water availability. This closure can be triggered by hydraulic ('H') and/or chemical signals ('C', 'H+C'). By combining plant hydraulic relations with a model for stomatal conductance, including chemical signalling, our aim was to derive a simple relation that links soil water availability, expressed as the fraction of roots in dry soil, to transpiration. We used the detailed mechanistic soil-root water flow model R-SWMS to verify this relation. Virtual split root experiments were simulated, comparing horizontally and vertically split domains with varying fractions of roots in dry soil and comparing different strengths of stomatal regulation by chemical and hydraulic signals. Transpiration predicted by the relation was in good agreement with numerical simulations. Under certain conditions H+C control leads to isohydric plant behaviour, which means that stomata close to keep leaf water potential constant after reaching a certain level. C control on the other hand exerts anisohydric behaviour, meaning that stomata remain fully open during changes in leaf water potential. For C control the relation between transpiration reduction and fraction of roots in dry soil becomes independent of transpiration rate whereas H+C control results in stronger reduction for higher transpiration rates. Simple relations that link effective soil and leaf water potential can describe different stomatal control resulting in contrasting behaviour.

  2. [Mechanism of stomatal regulation by root sourced signaling and its agricultural signficance].

    PubMed

    Guo, Anhong; Li, Zhaoxiang; Liu, Gengshan; Yang, Yuanyan; An, Shunqing

    2004-06-01

    Under soil drought condition, root sourced signal abcisic acid (ABA) plays an important role in the long distance signaling process, and can be a measurement of soil water availability. ABA is also an effective stomatal closing agent, and acts to reduce transpiration and canopy water loss. This paper briefly introduced the physiological mechanism and theoretical model about the stomatal regulation by root sourced signaling, and indicated that the combination of this model with root water absorption model and stomatal conductance model could be more effective in depicting the response of plant to soil drying and atmospheric drought. In addition, some effective irrigation approaches, such as regulated deficit irrigation (RDI), partial root-zone drying (PRD) and controlled alternative irrigation (CAI) were profited from the mechanism of plant water use regulation by the root sourced signaling. These irrigation measures favored to reasonably distribute available soil water in root-zone. Root signaling system also played important role in regulating root growth and its development, retarding shoot growth to adjusting root shoot ratio, and optimizing assimilation allocation to favor to improve reproductive development. These processes hold substantial promise for enhancing crop water use efficiency. PMID:15362642

  3. Large amplitude nonlinear structures in the nighttime polar mesosphere

    NASA Astrophysics Data System (ADS)

    Maharaj, Shimul K.; Bharuthram, Ramashwar; Singh Lakhina, Gurbax; Muralikrishna, Polinaya; Singh, Satyavir

    2016-07-01

    The existence of large amplitude potential structures will be investigated for a plasma composed of negative ions, positive ions, electrons and an additional fourth component of charged (usually positive) nano-sized ions in an attempt to model the plasma composition in the nighttime polar mesosphere (˜80 - 90 km altitude) [1]. The fourth ionic component becomes positively charged if there is a high enough concentration of negative ions which are sufficiently heavy. The positive charge on the fourth component can be explained by the capture of currents, and is not a result of photo-emission and secondary electron emission processes. Consequently, if the negative ions are much lighter, then the fourth ion component will become negatively charged. The charged ion species will be treated as inertial species which are cold or adiabatic, whilst the electrons will be considered to be Boltzmann-distributed (isothermal). Taking into consideration not only the dynamics of the heaviest species (dust-acoustic) but also the lighter ions (ion-acoustic), the theoretical study will use the Sagdeev pseudo-potential formalism to explore the existence of arbitrary amplitude solitons and double layer potential structures. [1] Observations of positively charged nanoparticles in the nighttime polar mesosphere, M. Rapp, J. Hedin, I. Strelnikova, M. Friederich, J. Gumbel, and F.˜J. Lübken, Geophys. Res. Letters. 32, L23821, doi:10.1029/2005GL024676 (2005).

  4. [Nighttime eating disorders--clinical symptoms and treatment].

    PubMed

    Zawilska, Jolanta B; Santorek-Strumiłło, Edyta J; Kuna, Paulina

    2010-01-01

    Nighttime eating is categorized as either night eating syndrome (NES) or the sleep-related eating disorder (SRED). Both diseases are often connected with an increase of the body mass, obesity, and with psychiatric disturbances. NES is characterized by evening hyperphagia, abnormally increased food intake after the evening meal, nocturnal awakings with ingestions, morning anorexia, and insomnia. Patients suffering from NES are aware of their nocturnal ingestions. It is suggested that NES is an abnormality in the circadian rhythm of meal timing that occurs in people with normal circadian rhythm of sleep. Other factors underlying NES include genetic predispositions, hormonal and neurochemical disturbances, and mood disorders. SRED is characterized by recurrent episodes of eating or drinking after arousal from nighttime sleep, unaware in tight the most cases, with adverse consequences. The distinctive features of SRED are amnesia of night eating episodes and consumption of non-typical food or dangerous articles. SRED is frequently associated with other sleep disorders, e.g., restless leg syndrome, periodic limb movement disorder, obstructive sleep apnea, and somnambulism. It can be also induced by medicines applied by a patient (e.g. zolpidem). It is hypothesized that the syndrome represents a variation of somnambulism. In the treatment of NES both non-pharmacological methods (psychotherapy, phototherapy) as well as the pharmacotherapy (aimed to increase serotoninergic neurotransmission in the brain, predominantly by sertraline, a selective serotonin re-uptake inhibitor) are used. SRED can be treated by controlling comorbid sleep disorders and eliminating provocative sedative hypnotics.

  5. Nighttime ionospheric D region parameters from VLF phase and amplitude

    NASA Astrophysics Data System (ADS)

    Thomson, Neil R.; Clilverd, Mark A.; McRae, Wayne M.

    2007-07-01

    Nighttime ionospheric D region heights and electron densities are determined from an extensive set of VLF radio phase and amplitude observations. The D region parameters are characterized by the traditional H' (height in kilometers) and β (sharpness in km-1) as used by Wait and by the U. S. Navy in their Earth-ionosphere waveguide programs. The VLF measurements were made with several frequencies in the range 10 kHz to 41 kHz on long, mainly all-sea paths, including Omega La Reunion and Omega Argentina to Dunedin, New Zealand, NAU (Puerto Rico) and NAA (Maine, USA) to Cambridge, UK, and NPM (Hawaii) to San Francisco. Because daytime VLF propagation on such paths is readily measured and predicted, the differences between night and day amplitudes and phases were measured and compared with calculations for a range of nighttime ionospheric parameters. This avoided the problem of uncertainties in the transmitter powers. In this way the height, H', and the sharpness, β, when averaged over periods of several days, at least for the midlatitude D region near solar minimum, were found to be 85.1 ± 0.4 km and 0.63 ± 0.04 km-1, respectively.

  6. Calculating Change in Global Urbanization Using Nighttime Lights

    NASA Astrophysics Data System (ADS)

    Stewart, B. P.; McWilliams, K. L.; Roberts, M.

    2014-12-01

    Measuring urban change is important for policy makers at the municipal, regional, national, and international levels. However, obtaining urban metrics from countries is often difficult, and data-poor, developing countries have little to no capacity to measure urban change over long time periods. The goals of this analysis were to develop a standard methodology for extracting urban footprints from remotely sensed data, and to determine what environmental and economic conditions control urban brightness. For example, an urban area in a country with less development may have darker urban areas than their more developed counterparts, thus, country specific thresholds for separating urban from non-urban areas are necessary to appropriately analyze urbanization. Nighttime lights data, from the DMSP-OLS constellation, are well suited for this task, due to their global coverage, historical archive, and ease of accessibility for data-poor countries. In this project, we used ESA's GlobCover dataset as our validation data, and developed a country-specific classification of urban vs. non urban cover using the nighttime lights data. Classification accuracies varied by country, but ranged from ~90-99%. Preliminary results show that brightness thresholds vary substantially both between countries, and as a function of geographic location. Finally, brightness thresholds and their associated accuracies were compared to environmental and economic indices through regression analysis, in an attempt to determine the drivers of urban brightness.

  7. Savanna Tree Seedlings are Physiologically Tolerant to Nighttime Freeze Events

    PubMed Central

    O’Keefe, Kimberly; Nippert, Jesse B.; Swemmer, Anthony M.

    2016-01-01

    Freeze events can be important disturbances in savanna ecosystems, yet the interactive effect of freezing with other environmental drivers on plant functioning is unknown. Here, we investigated physiological responses of South African tree seedlings to interactions of water availability and freezing temperatures. We grew widely distributed South African tree species (Colophospermum mopane, Combretum apiculatum, Acacia nigrescens, and Cassia abbreviata) under well-watered and water-limited conditions and exposed individuals to nighttime freeze events. Of the four species studied here, C. mopane was the most tolerant of lower water availability. However, all species were similarly tolerant to nighttime freezing and recovered within one week following the last freezing event. We also show that water limitation somewhat increased freezing tolerance in one of the species (C. mopane). Therefore, water limitation, but not freezing temperatures, may restrict the distribution of these species, although the interactions of these stressors may have species-specific impacts on plant physiology. Ultimately, we show that unique physiologies can exist among dominant species within communities and that combined stresses may play a currently unidentified role in driving the function of certain species within southern Africa. PMID:26870065

  8. [Nighttime eating disorders--clinical symptoms and treatment].

    PubMed

    Zawilska, Jolanta B; Santorek-Strumiłło, Edyta J; Kuna, Paulina

    2010-01-01

    Nighttime eating is categorized as either night eating syndrome (NES) or the sleep-related eating disorder (SRED). Both diseases are often connected with an increase of the body mass, obesity, and with psychiatric disturbances. NES is characterized by evening hyperphagia, abnormally increased food intake after the evening meal, nocturnal awakings with ingestions, morning anorexia, and insomnia. Patients suffering from NES are aware of their nocturnal ingestions. It is suggested that NES is an abnormality in the circadian rhythm of meal timing that occurs in people with normal circadian rhythm of sleep. Other factors underlying NES include genetic predispositions, hormonal and neurochemical disturbances, and mood disorders. SRED is characterized by recurrent episodes of eating or drinking after arousal from nighttime sleep, unaware in tight the most cases, with adverse consequences. The distinctive features of SRED are amnesia of night eating episodes and consumption of non-typical food or dangerous articles. SRED is frequently associated with other sleep disorders, e.g., restless leg syndrome, periodic limb movement disorder, obstructive sleep apnea, and somnambulism. It can be also induced by medicines applied by a patient (e.g. zolpidem). It is hypothesized that the syndrome represents a variation of somnambulism. In the treatment of NES both non-pharmacological methods (psychotherapy, phototherapy) as well as the pharmacotherapy (aimed to increase serotoninergic neurotransmission in the brain, predominantly by sertraline, a selective serotonin re-uptake inhibitor) are used. SRED can be treated by controlling comorbid sleep disorders and eliminating provocative sedative hypnotics. PMID:21387771

  9. Enhanced tiredness among young impaired male nighttime drivers.

    PubMed

    Corfitsen, M T

    1996-03-01

    This study focuses on the incidence and amount of tiredness among young impaired male nighttime drivers during the hours between midnight and 6 a.m. One hundred and twenty impaired drivers, aged 18-30 years, with an average blood alcohol concentration of 1.54 g/l (range 0.81-2.99 g/l) are compared to 240 sober drivers of similar age stopped by the police in roadside surveys. A questionnaire shows that the increase in median awake period during the six observation hours is gradual and directly proportional to the time of the night for both groups, while the average awake period is significantly longer and that the average previous sleep period is significantly shorter for the impaired drivers. Self-assessment of tiredness shows 30 "rested," 68 "tired," and 22 "very tired" impaired drivers and 123 "rested," 105 "tired," and 12 "very tired" sober control drivers. This difference in level of "tiredness" is also significant. The questionnaire and the results of a simple visual reaction time test show individual differences for the drivers in both groups, but the difference in mean reaction time between the impaired drivers and the sober drivers is significant. Sub-division of the impaired drivers according to their self-assessed level of "tiredness" also shows significant differences in mean reaction time. The findings of the present study support the hypothesis that tiredness is an inherent and common accident risk factor among young male impaired drivers in nighttime traffic. PMID:8703273

  10. Savanna Tree Seedlings are Physiologically Tolerant to Nighttime Freeze Events.

    PubMed

    O'Keefe, Kimberly; Nippert, Jesse B; Swemmer, Anthony M

    2016-01-01

    Freeze events can be important disturbances in savanna ecosystems, yet the interactive effect of freezing with other environmental drivers on plant functioning is unknown. Here, we investigated physiological responses of South African tree seedlings to interactions of water availability and freezing temperatures. We grew widely distributed South African tree species (Colophospermum mopane, Combretum apiculatum, Acacia nigrescens, and Cassia abbreviata) under well-watered and water-limited conditions and exposed individuals to nighttime freeze events. Of the four species studied here, C. mopane was the most tolerant of lower water availability. However, all species were similarly tolerant to nighttime freezing and recovered within one week following the last freezing event. We also show that water limitation somewhat increased freezing tolerance in one of the species (C. mopane). Therefore, water limitation, but not freezing temperatures, may restrict the distribution of these species, although the interactions of these stressors may have species-specific impacts on plant physiology. Ultimately, we show that unique physiologies can exist among dominant species within communities and that combined stresses may play a currently unidentified role in driving the function of certain species within southern Africa. PMID:26870065

  11. Calcium effects on stomatal movement in Commelina communis L

    SciTech Connect

    Schwartz, A.; Ilan, N.; Grantz, D.A. )

    1988-07-01

    Stomatal movements depends on both ion influx and efflux: attainment of steady state apertures reflects modulation of either or both processes. The role of Ca{sup 2+} in those two processes was investigated in isolated epidermal strips of Commelina communis, using the Ca{sup 2+} chelator EGTA to reduce apoplastic (Ca{sup 2+}). The results suggest that a certain concentration of Ca{sup 2+} is an absolute requirement for salt efflux and stomatal closure. EGTA (2 millimolar) increased KCl-dependent stomatal opening in darkness and completely inhibited the dark-induced closure of initially open stomata. Closure was inhibited even in a KCl-free medium. Thus, maintenance of stomata in the open state does not necessarily depend on continued K{sup +} influx but on the inhibition of salt efflux. Opening in the dark was stimulated by IAA in a concentration-dependent manner, up to 15.4 micrometer without reaching saturation, while the response to EGTA leveled off at 9.2 micrometer. IAA did not inhibit stomatal closure to the extent it stimulated opening. The response to IAA is thus consistent with a primary stimulation of opening, while EGTA can be considered a specific inhibitor of stomatal closing since it inhibits closure to a much larger degree than it stimulates opening. CO{sub 2} causes concentration-dependent reduction in the steady state stomatal aperture. EGTA completely reversed CO{sub 2}-induced closing of open stomata but only partially prevented the inhibition of opening.

  12. NFX1-LIKE2 (NFXL2) Suppresses Abscisic Acid Accumulation and Stomatal Closure in Arabidopsis thaliana

    PubMed Central

    Lisso, Janina; Schröder, Florian; Fisahn, Joachim; Müssig, Carsten

    2011-01-01

    The NFX1-LIKE1 (NFXL1) and NFXL2 genes were identified as regulators of salt stress responses. The NFXL1 protein is a nuclear factor that positively affects adaptation to salt stress. The nfxl1-1 loss-of-function mutant displayed reduced survival rates under salt and high light stress. In contrast, the nfxl2-1 mutant, defective in the NFXL2 gene, and NFXL2-antisense plants exhibited enhanced survival under these conditions. We show here that the loss of NFXL2 function results in abscisic acid (ABA) overaccumulation, reduced stomatal conductance, and enhanced survival under drought stress. The nfxl2-1 mutant displayed reduced stomatal aperture under all conditions tested. Fusicoccin treatment, exposition to increasing light intensities, and supply of decreasing CO2 concentrations demonstrated full opening capacity of nfxl2-1 stomata. Reduced stomatal opening presumably is a consequence of elevated ABA levels. Furthermore, seedling growth, root growth, and stomatal closure were hypersensitive to exogenous ABA. The enhanced ABA responses may contribute to the improved drought stress resistance of the mutant. Three NFXL2 splice variants were cloned and named NFXL2-78, NFXL2-97, and NFXL2-100 according to the molecular weight of the putative proteins. Translational fusions to the green fluorescent protein suggest nuclear localisation of the NFXL2 proteins. Stable expression of the NFXL2-78 splice variant in nfxl2-1 plants largely complemented the mutant phenotype. Our data show that NFXL2 controls ABA levels and suppresses ABA responses. NFXL2 may prevent unnecessary and costly stress adaptation under favourable conditions. PMID:22073231

  13. Psychological Stress and Recurrent Aphthous Stomatitis

    PubMed Central

    de Barros Gallo, Camila; Mimura, Maria Angela Martins; Sugaya, Norberto Nobuo

    2009-01-01

    INTRODUCTION AND OBJECTIVES: Recurrent aphthous stomatitis (RAS) is the most common type of ulcerative disease of the oral mucosa. Despite its worldwide occurrence and the extensive amount of research that has been devoted to the subject, the etiology of RAS remains unclear. Nevertheless, several hereditary, nutritional, infectious and psychological factors have been associated with RAS. The aim of this case-control study was to assess the influence of psychological stress on the manifestation of RAS. METHOD: Fifty patients were enrolled in the trial. Twenty-five RAS patients constituted the study group and another 25 non-RAS patients who were similarly matched for sex, age and socioeconomic status constituted the control group. Each patient was evaluated in terms of the four domains of stress (emotional, physical, social and cognitive) using an internationally validated questionnaire, which was comprised of 59 items and measured the frequency and intensity of stress symptoms. The RAS group was interviewed during an active RAS episode. Completed questionnaires were submitted to proper analytical software and interpreted by an expert psychologist. RESULTS: There was a higher level of psychological stress among RAS group patients when compared to the control group (P < 0.05). CONCLUSION: Psychological stress may play a role in the manifestation of RAS; it may serve as a trigger or a modifying factor rather than being a cause of the disease. PMID:19606240

  14. Correcting incompatible DN values and geometric errors in nighttime lights time series images

    SciTech Connect

    Zhao, Naizhuo; Zhou, Yuyu; Samson, Eric L.

    2014-09-19

    The Defense Meteorological Satellite Program’s Operational Linescan System (DMSP-OLS) nighttime lights imagery has proven to be a powerful remote sensing tool to monitor urbanization and assess socioeconomic activities at large scales. However, the existence of incompatible digital number (DN) values and geometric errors severely limit application of nighttime light image data on multi-year quantitative research. In this study we extend and improve previous studies on inter-calibrating nighttime lights image data to obtain more compatible and reliable nighttime lights time series (NLT) image data for China and the United States (US) through four steps: inter-calibration, geometric correction, steady increase adjustment, and population data correction. We then use gross domestic product (GDP) data to test the processed NLT image data indirectly and find that sum light (summed DN value of pixels in a nighttime light image) maintains apparent increase trends with relatively large GDP growth rates but does not increase or decrease with relatively small GDP growth rates. As nighttime light is a sensitive indicator for economic activity, the temporally consistent trends between sum light and GDP growth rate imply that brightness of nighttime lights on the ground is correctly represented by the processed NLT image data. Finally, through analyzing the corrected NLT image data from 1992 to 2008, we find that China experienced apparent nighttime lights development in 1992-1997 and 2001-2008 respectively and the US suffered from nighttime lights decay in large areas after 2001.

  15. Non-Stomatal Limitation to Photosynthesis in Cinnamomum camphora Seedings Exposed to Elevated O3

    PubMed Central

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

    2014-01-01

    Ozone (O3) is the most phytotoxic air pollutant for global forests, with decreased photosynthesis widely regarded as one of its most common effects. However, controversy exists concerning the mechanism that underlies the depressing effects of O3 on CO2 assimilation. In the present study, seedlings of Cinnamomum camphora, a subtropical evergreen tree species that has rarely been studied, were exposed to ambient air (AA), ambient air plus 60 [ppb] O3 (AA+60), or ambient air plus 120 [ppb] O3 (AA+120) in open-top chambers (OTCs) for 2 years. Photosynthetic CO2 exchange and chlorophyll a fluorescence were investigated in the second growing season (2010). We aim to determine whether stomatal or non-stomatal limitation is responsible for the photosynthesis reduction and to explore the potential implications for forest ecosystem functions. Results indicate that elevated O3 (E-O3) reduced the net photosynthetic rates (PN) by 6.0-32.2%, with significant differences between AA+60 and AA+120 and across the four measurement campaigns (MCs). The actual photochemical efficiency of photosystem II (PSII) in saturated light (Fv′/Fm′) was also significantly decreased by E-O3, as was the effective quantum yield of PSII photochemistry (ΦPSII). Moreover, E-O3 significantly and negatively impacted the maximum rates of carboxylation (Vcmax) and electron transport (Jmax). Although neither the stomatal conductance (gs) nor the intercellular CO2 concentration (Ci) was decreased by E-O3, PN/gs was significantly reduced. Therefore, the observed reduction in PN in the present study should not be attributed to the unavailability of CO2 due to stomatal limitation, but rather to the O3-induced damage to Ribulose-1,5-bisphosphate carboxylase/oxygenase and the photochemical apparatus. This suggests that the down-regulation of stomatal conductance could fail to occur, and the biochemical processes in protoplasts would become more susceptible to injuries under long-term O3 exposure, which may

  16. Sport Transition of JPSS VIIRS Imagery for Night-time Applications

    NASA Technical Reports Server (NTRS)

    Fuell, Kevin; LeRoy, Anita; Smith, Matt; Miller, Steve; Kann, Diedre; Bernhardt, David; Reydell, Nezette; Cox, Robert

    2014-01-01

    The NASA/Short-term Prediction, Research, and Transition (SPoRT) Program and NOAA/Cooperative Institute for Research in the Atmosphere (CIRA) work within the NOAA/Joint Polar Satellite System (JPSS) Proving Ground to demonstrate the unique capabilities of the VIIRS instrument. Very similar to MODIS, the VIIRS instrument provides many high-resolution visible and infrared channels in a broad spectrum. In addition, VIIRS is equipped with a low-light sensor that is able to detect light emissions from the land and atmosphere as well as reflected sunlight by the lunar surface. This band is referred to as the Day-Night Band due to the sunlight being used at night to see cloud and topographic features just as one would typically see in day-time visible imagery. NWS forecast offices that collaborate with SPoRT and CIRA have utilized MODIS imagery in operations, but have longed for more frequent passes of polar-orbiting data. The VIIRS instrument enhances SPoRT collaborations with WFOs by providing another day and night-time pass, and at times two additional passes due to its large swath width. This means that multi-spectral, RGB imagery composites are more readily available to prepare users for their use in GOES-R era and high-resolution imagery for use in high-latitudes is more frequently able to supplement standard GOES imagery within the SPoRT Hybrid GEO-LEO product. The transition of VIIRS also introduces the new Day-Night Band capability to forecast operations. An Intensive Evaluation Period (IEP) was conducted in Summer 2013 with a group of "Front Range" NWS offices related to VIIRS night-time imagery. VIIRS single-channel imagery is able to better analyze the specific location of fire hotspots and other land features, as well as provide a more true measurement of various cloud and aerosol properties than geostationary measurements, especially at night. Viewed within the SPoRT Hybrid imagery, the VIIRS data allows forecasters to better interpret the more frequent, but

  17. Stomatal action directly feeds back on leaf turgor: new insights into the regulation of the plant water status from non-invasive pressure probe measurements.

    PubMed

    Ache, Peter; Bauer, Hubert; Kollist, Hannes; Al-Rasheid, Khaled A S; Lautner, Silke; Hartung, Wolfram; Hedrich, Rainer

    2010-06-01

    Uptake of CO(2) by the leaf is associated with loss of water. Control of stomatal aperture by volume changes of guard cell pairs optimizes the efficiency of water use. Under water stress, the protein kinase OPEN STOMATA 1 (OST1) activates the guard-cell anion release channel SLOW ANION CHANNEL-ASSOCIATED 1 (SLAC1), and thereby triggers stomatal closure. Plants with mutated OST1 and SLAC1 are defective in guard-cell turgor regulation. To study the effect of stomatal movement on leaf turgor using intact leaves of Arabidopsis, we used a new pressure probe to monitor transpiration and turgor pressure simultaneously and non-invasively. This probe permits routine easy access to parameters related to water status and stomatal conductance under physiological conditions using the model plant Arabidopsis thaliana. Long-term leaf turgor pressure recordings over several weeks showed a drop in turgor during the day and recovery at night. Thus pressure changes directly correlated with the degree of plant transpiration. Leaf turgor of wild-type plants responded to CO(2), light, humidity, ozone and abscisic acid (ABA) in a guard cell-specific manner. Pressure probe measurements of mutants lacking OST1 and SLAC1 function indicated impairment in stomatal responses to light and humidity. In contrast to wild-type plants, leaves from well-watered ost1 plants exposed to a dry atmosphere wilted after light-induced stomatal opening. Experiments with open stomata mutants indicated that the hydraulic conductance of leaf stomata is higher than that of the root-shoot continuum. Thus leaf turgor appears to rely to a large extent on the anion channel activity of autonomously regulated stomatal guard cells. PMID:20345603

  18. Stomatal action directly feeds back on leaf turgor: new insights into the regulation of the plant water status from non-invasive pressure probe measurements.

    PubMed

    Ache, Peter; Bauer, Hubert; Kollist, Hannes; Al-Rasheid, Khaled A S; Lautner, Silke; Hartung, Wolfram; Hedrich, Rainer

    2010-06-01

    Uptake of CO(2) by the leaf is associated with loss of water. Control of stomatal aperture by volume changes of guard cell pairs optimizes the efficiency of water use. Under water stress, the protein kinase OPEN STOMATA 1 (OST1) activates the guard-cell anion release channel SLOW ANION CHANNEL-ASSOCIATED 1 (SLAC1), and thereby triggers stomatal closure. Plants with mutated OST1 and SLAC1 are defective in guard-cell turgor regulation. To study the effect of stomatal movement on leaf turgor using intact leaves of Arabidopsis, we used a new pressure probe to monitor transpiration and turgor pressure simultaneously and non-invasively. This probe permits routine easy access to parameters related to water status and stomatal conductance under physiological conditions using the model plant Arabidopsis thaliana. Long-term leaf turgor pressure recordings over several weeks showed a drop in turgor during the day and recovery at night. Thus pressure changes directly correlated with the degree of plant transpiration. Leaf turgor of wild-type plants responded to CO(2), light, humidity, ozone and abscisic acid (ABA) in a guard cell-specific manner. Pressure probe measurements of mutants lacking OST1 and SLAC1 function indicated impairment in stomatal responses to light and humidity. In contrast to wild-type plants, leaves from well-watered ost1 plants exposed to a dry atmosphere wilted after light-induced stomatal opening. Experiments with open stomata mutants indicated that the hydraulic conductance of leaf stomata is higher than that of the root-shoot continuum. Thus leaf turgor appears to rely to a large extent on the anion channel activity of autonomously regulated stomatal guard cells.

  19. Global Night-Time Lights for Observing Human Activity

    NASA Technical Reports Server (NTRS)

    Hipskind, Stephen R.; Elvidge, Chris; Gurney, K.; Imhoff, Mark; Bounoua, Lahouari; Sheffner, Edwin; Nemani, Ramakrishna R.; Pettit, Donald R.; Fischer, Marc

    2011-01-01

    We present a concept for a small satellite mission to make systematic, global observations of night-time lights with spatial resolution suitable for discerning the extent, type and density of human settlements. The observations will also allow better understanding of fine scale fossil fuel CO2 emission distribution. The NASA Earth Science Decadal Survey recommends more focus on direct observations of human influence on the Earth system. The most dramatic and compelling observations of human presence on the Earth are the night light observations taken by the Defence Meteorological System Program (DMSP) Operational Linescan System (OLS). Beyond delineating the footprint of human presence, night light data, when assembled and evaluated with complementary data sets, can determine the fine scale spatial distribution of global fossil fuel CO2 emissions. Understanding fossil fuel carbon emissions is critical to understanding the entire carbon cycle, and especially the carbon exchange between terrestrial and oceanic systems.

  20. Anisotropy of high-latitude nighttime F region irregularities

    SciTech Connect

    Livingston, R.C.; Rino, C.L.; Owen, J.; Tsunoda, R.T.

    1982-12-01

    The anisotropy of intermediate-scale, F region irregularities in the nighttime auroral zone is described. The study is based upon spaced-receiver phase scintillation measurements made with the Wideband satellite at Poker Flat, Alaska. A systematic dependence of irregularity anisotropy with local time and magnetic latitude is observed, suggesting convective control. Sheetlike irregularities are confined to the zone of east-west drift near the equatorward boundary of the auroral zone, and at the flow reversal, or Harang discontinuity, the cross-field extension of the sheets is reduced. The extension of rodlike irregularities, which are observed poleward of the zonal convection boundary, also shows apparent convection dominance. Mechanisms for convection control of the anisotropy are discussed.

  1. Rocket radio measurement of electron density in the nighttime ionosphere

    NASA Technical Reports Server (NTRS)

    Gilchrist, B. E.; Smith, L. G.

    1979-01-01

    One experimental technique based on the Faraday rotation effect of radio waves is presented for measuring electron density in the nighttime ionosphere at midlatitudes. High frequency linearly-polarized radio signals were transmitted to a linearly-polarized receiving system located in a spinning rocket moving through the ionosphere. Faraday rotation was observed in the reference plane of the rocket as a change in frequency of the detected receiver output. The frequency change was measured and the information was used to obtain electron density data. System performance was evaluated and some sources of error were identified. The data obtained was useful in calibrating a Langmuir probe experiment for electron density values of 100/cu cm and greater. Data from two rocket flights are presented to illustrate the experiment.

  2. Nighttime reactive nitrogen measurements from stratospheric infrared thermal emission observations

    NASA Technical Reports Server (NTRS)

    Abbas, Mian M.; Kunde, Virgil G.; Brasunas, J. C.; Herman, J. R.; Massie, Steven T.

    1991-01-01

    IR thermal emission spectra of the earth's atmosphere in the 700-2000/cm region were obtained with a cryogenically cooled high-resolution interferometer spectrometer on a balloon flight from Palestine, Texas, on September 15-16, 1986. The observations exhibit spectral features of a number of stratospheric constituents, including important species of the reactive nitrogen family. An analysis of the observed data for simultaneously measured vertical distributions of O3, H2O, N2O, NO2, N2O5, HNO3, and ClONO2 is presented. These measurements permit the first direct determination of the nighttime total reactive nitrogen concentrations, and the partitioning of the important elements of the NO(x) family. Comparisons of the total reactive nitrogen budget are made with the measurements by the ATMOS experiment and with the predictions of one-dimensional and two-dimensional photochemical models.

  3. Satellite Imagery Analysis for Nighttime Temperature Inversion Clouds

    NASA Technical Reports Server (NTRS)

    Kawamoto, K.; Minnis, P.; Arduini, R.; Smith, W., Jr.

    2001-01-01

    Clouds play important roles in the climate system. Their optical and microphysical properties, which largely determine their radiative property, need to be investigated. Among several measurement means, satellite remote sensing seems to be the most promising. Since most of the cloud algorithms proposed so far are daytime use which utilizes solar radiation, Minnis et al. (1998) developed a nighttime use one using 3.7-, 11 - and 12-microns channels. Their algorithm, however, has a drawback that is not able to treat temperature inversion cases. We update their algorithm, incorporating new parameterization by Arduini et al. (1999) which is valid for temperature inversion cases. This updated algorithm has been applied to GOES satellite data and reasonable retrieval results were obtained.

  4. Observation of the nighttime nitrate radical in Hefei, China.

    PubMed

    Li, Suwen; Liu, Wenqing; Xie, Pinua; Li, Ang; Qin, Min; Peng, Fumin; Zhu, Yanwu

    2008-01-01

    Observation of nighttime nitrate radical (NO3) was performed by using long path differential optical absorption spectroscopy (LP-DOAS), on the outskirts of Hefei, China. The time series of NO3 and supporting parameters were simultaneously measured for a week (31 May-7 June 2006). The results indicated that the average concentration of NO3 was 15.6 pptv with an average lifetimes of 96 s, whereas, NO3 production rates varied from 8 x 10(5)/(cm3 x s) to 2.98 x 10(7)/(cm3 x s). Furthermore, the calculated N2O5 concentration averaged at 380 pptv. Analysis of data indicated that direct sinks were probably dominating the NO3 loss process during this campaign. The results were compared with other campaigns in the boundary layer.

  5. Evening and nighttime features of equatorial ionospheric F2 layer

    NASA Astrophysics Data System (ADS)

    Oyekola, Oyedemi S.

    2016-07-01

    We have used ionosonde observations recorded at Ibadan (7.4 degree North, 3.9 degree East) during the International Geophysical year (1957-58) to investigate evening and nighttime characteristic features of equatorial ionosphere during high solar flux and quiet magnetic conditions. We have also used International Reference Ionosphere model (IRI-2012) data. Our results show that the base of the ionosphere descends at a rate of -27.5 km/hr between 2000 LT and 0400 LT, whereas the observed bottomside peak of the ionosphere move down at a rate of -29.3 km/hr between 1900 and 0500 LT, while IRI2012 bottomside peak show -29.8 km/hr between 2000 LT and 0500 LT. The downward flow rate of plasma concentration between 1900 LT and 0500 LT and between 1800 LT and 0400 LT is approximately 0.040 electron per cubic metre per hour and 0.081 electron per cubic metre per hour, respectively for observed and for modeled NmF2. Month-by-month averaged altitudes (h'F, hmF2, and modeled hmF2) indicate significant local time variation. In addition, the month-by month variation indicates nighttime double crest of averaged peak height (hmF2) in the ionosonde measurements and in the IRI-2012 empirical model with a trough in June-August for data and In July for model. The monthly mean downward vertical drift velocities derived from local time variation of h'F and hmF2 together with global drift model essential demonstrate much fluctuations. We found a "domed shape" in modeled drift velocity, indicating equatorward plasma between April and September.

  6. Nighttime NOx Chemistry in Coal-Fired Power Plant Plumes

    NASA Astrophysics Data System (ADS)

    Fibiger, D. L.; McDuffie, E. E.; Dube, W. P.; Veres, P. R.; Lopez-Hilfiker, F.; Lee, B. H.; Green, J. R.; Fiddler, M. N.; Ebben, C. J.; Sparks, T.; Weinheimer, A. J.; Montzka, D.; Campos, T. L.; Cohen, R. C.; Bililign, S.; Holloway, J. S.; Thornton, J. A.; Brown, S. S.

    2015-12-01

    Nitrogen oxides (NOx = NO + NO2) play a key role in atmospheric chemistry. During the day, they catalyze ozone (O3) production, while at night they can react to form nitric acid (HNO3) and nitryl chloride (ClNO2) and remove O3 from the atmosphere. These processes are well studied in the summer, but winter measurements are more limited. Coal-fired power plants are a major source of NOx to the atmosphere, making up approximately 30% of emissions in the US (epa.gov). NOx emissions can vary seasonally, as well as plant-to-plant, with important impacts on the details of the plume chemistry. In particular, due to inefficient plume dispersion, nighttime NOx emissions from power plants are held in concentrated plumes, where rates of mixing with ambient O3 have a strong influence on plume evolution. We will show results from the aircraft-based WINTER campaign over the northeastern United States, where several nighttime intercepts of power plant plumes were made. Several of these intercepts show complete O3 titration, which can have a large influence on NOx lifetime, and thus O3 production, in the plume. When power plant NO emissions exceed background O3 levels, O3 is completely consumed converting NO to NO2. In the presence of O3, NO2 will be oxidized to NO3, which will then react with NO2 to form N2O5, which can then form HNO3 and/or ClNO2 and, ultimately, remove NOx from the atmosphere or provide next-day oxidant sources. If there is no O3 present, however, no further chemistry can occur and NO and NO2 will be transported until mixing with sufficient O3 for higher oxidation products. Modeling results of plume development and mixing, which can tell us more about this transport, will also be presented.

  7. Impact of Nighttime Temperature on Physiology and Growth of Spring Wheat

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Climate models predict greater increases in nighttime temperature in future climates. The effects of high nighttime temperature on wheat (Triticum aestivum L.) are not well understood and are needed to better understand impacts of climate change. The objectives of this study were to investigate the ...

  8. Protein Phosphorylation and Redox Modification in Stomatal Guard Cells.

    PubMed

    Balmant, Kelly M; Zhang, Tong; Chen, Sixue

    2016-01-01

    Post-translational modification (PTM) is recognized as a major process accounting for protein structural variation, functional diversity, and the dynamics and complexity of the proteome. Since PTMs can change the structure and function of proteins, they are essential to coordinate signaling networks and to regulate important physiological processes in eukaryotes. Plants are constantly challenged by both biotic and abiotic stresses that reduce productivity, causing economic losses in crops. The plant responses involve complex physiological, cellular, and molecular processes, with stomatal movement as one of the earliest responses. In order to activate such a rapid response, stomatal guard cells employ cellular PTMs of key protein players in the signaling pathways to regulate the opening and closure of the stomatal pores. Here we discuss two major types of PTMs, protein phosphorylation and redox modification that play essential roles in stomatal movement under stress conditions. We present an overview of PTMs that occur in stomatal guard cells, especially the methods and technologies, and their applications in PTM identification and quantification. Our focus is on PTMs that modify molecular components in guard cell signaling at the stages of signal perception, second messenger production, as well as downstream signaling events and output. Improved understanding of guard cell signaling will enable generation of crops with enhanced stress tolerance, and increased yield and bioenergy through biotechnology and molecular breeding.

  9. Protein Phosphorylation and Redox Modification in Stomatal Guard Cells

    PubMed Central

    Balmant, Kelly M.; Zhang, Tong; Chen, Sixue

    2016-01-01

    Post-translational modification (PTM) is recognized as a major process accounting for protein structural variation, functional diversity, and the dynamics and complexity of the proteome. Since PTMs can change the structure and function of proteins, they are essential to coordinate signaling networks and to regulate important physiological processes in eukaryotes. Plants are constantly challenged by both biotic and abiotic stresses that reduce productivity, causing economic losses in crops. The plant responses involve complex physiological, cellular, and molecular processes, with stomatal movement as one of the earliest responses. In order to activate such a rapid response, stomatal guard cells employ cellular PTMs of key protein players in the signaling pathways to regulate the opening and closure of the stomatal pores. Here we discuss two major types of PTMs, protein phosphorylation and redox modification that play essential roles in stomatal movement under stress conditions. We present an overview of PTMs that occur in stomatal guard cells, especially the methods and technologies, and their applications in PTM identification and quantification. Our focus is on PTMs that modify molecular components in guard cell signaling at the stages of signal perception, second messenger production, as well as downstream signaling events and output. Improved understanding of guard cell signaling will enable generation of crops with enhanced stress tolerance, and increased yield and bioenergy through biotechnology and molecular breeding. PMID:26903877

  10. Stomatal uptake of O3 in aspen and aspen-birch forests under free-air CO2 and O3 enrichment.

    PubMed

    Uddling, Johan; Hogg, Alan J; Teclaw, Ronald M; Carroll, Mary Anne; Ellsworth, David S

    2010-06-01

    Rising atmospheric carbon dioxide (CO2) may alleviate the toxicological impacts of concurrently rising tropospheric ozone (O3) during the present century if higher CO2 is accompanied by lower stomatal conductance (gs), as assumed by many models. We investigated how elevated concentrations of CO2 and O3, alone and in combination, affected the accumulated stomatal flux of O3 (AFst) by canopies and sun leaves in closed aspen and aspen-birch forests in the free-air CO2-O3 enrichment experiment near Rhinelander, Wisconsin. Stomatal conductance for O3 was derived from sap flux data and AFst was estimated either neglecting or accounting for the potential influence of non-stomatal leaf surface O3 deposition. Leaf-level AFst (AFst(l)) was not reduced by elevated CO2. Instead, there was a significant CO2 x O(3) interaction on AFst(l), as a consequence of lower values of gs in control plots and the combination treatment than in the two single-gas treatments. In addition, aspen leaves had higher AFst(l) than birch leaves, and estimates of AFst(l) were not very sensitive to non-stomatal leaf surface O3 deposition. Our results suggest that model projections of large CO2-induced reductions in gs alleviating the adverse effect of rising tropospheric O3 may not be reasonable for northern hardwood forests.

  11. Stomatal uptake of O3 in aspen and aspen-birch forests under free-air CO2 and O3 enrichment.

    PubMed

    Uddling, Johan; Hogg, Alan J; Teclaw, Ronald M; Carroll, Mary Anne; Ellsworth, David S

    2010-06-01

    Rising atmospheric carbon dioxide (CO2) may alleviate the toxicological impacts of concurrently rising tropospheric ozone (O3) during the present century if higher CO2 is accompanied by lower stomatal conductance (gs), as assumed by many models. We investigated how elevated concentrations of CO2 and O3, alone and in combination, affected the accumulated stomatal flux of O3 (AFst) by canopies and sun leaves in closed aspen and aspen-birch forests in the free-air CO2-O3 enrichment experiment near Rhinelander, Wisconsin. Stomatal conductance for O3 was derived from sap flux data and AFst was estimated either neglecting or accounting for the potential influence of non-stomatal leaf surface O3 deposition. Leaf-level AFst (AFst(l)) was not reduced by elevated CO2. Instead, there was a significant CO2 x O(3) interaction on AFst(l), as a consequence of lower values of gs in control plots and the combination treatment than in the two single-gas treatments. In addition, aspen leaves had higher AFst(l) than birch leaves, and estimates of AFst(l) were not very sensitive to non-stomatal leaf surface O3 deposition. Our results suggest that model projections of large CO2-induced reductions in gs alleviating the adverse effect of rising tropospheric O3 may not be reasonable for northern hardwood forests. PMID:20089338

  12. Treatment of radiation- and chemotherapy-induced stomatitis

    SciTech Connect

    Carnel, S.B.; Blakeslee, D.B.; Oswald, S.G.; Barnes, M. )

    1990-04-01

    Severe stomatitis is a common problem encountered during either radiation therapy or chemotherapy. Most therapeutic regimens are empirical, with no scientific basis. The purpose of this study is to determine the efficacy of various topical solutions in the treatment of radiation- or chemotherapy-induced stomatitis. Eighteen patients were entered into a prospective double-blinded study to test several topical solutions: (1) viscous lidocaine with 1% cocaine; (2) dyclonine hydrochloride 1.0% (Dyclone); (3) kaolin-pectin solution, diphenhydramine plus saline (KBS); and (4) a placebo solution. Degree of pain relief, duration of relief, side effects, and palatability were evaluated. The results showed that Dyclone provided the most pain relief. Dyclone and viscous lidocaine with 1% cocaine provided the longest pain relief, which averaged 50 minutes This study provides objective data and defines useful guidelines for treatment of stomatitis.

  13. Stomatal Response to Environment with Sesamum indicum. L. 1

    PubMed Central

    Hall, Anthony E.; Kaufmann, Merrill R.

    1975-01-01

    Leaf resistance of Sesamum indicum L. increased when the humidity gradient between leaf and air was increased, at moderate temperatures, even though calculated carbon dioxide concentrations within the leaf decreased slightly. Mesophyll resistance remained relatively constant when humidity gradients were changed, indicating that the increases in leaf resistance were mainly caused by reductions in stomatal aperture and that nonstomatal aspects of photosynthesis and respiration were not affected. Low carbon dioxide concentrations inside the leaf decreased but did not eliminate resistance response to the humidity gradient. Internal carbon dioxide concentrations had little effect on resistance in humid air but had moderate effects on resistance with large humidity gradients between leaf and air. Stomatal response to humidity was not present at high leaf temperatures. Effects of humidity gradients on photosynthetic and stomatal responses to temperature suggested that large humidity gradients may contribute to mid-day closure of stomata and depressions in photosynthesis. PMID:16659101

  14. Ozone Inhibits Guard Cell K+ Channels Implicated in Stomatal Opening

    NASA Astrophysics Data System (ADS)

    Torsethaugen, Gro; Pell, Eva J.; Assmann, Sarah M.

    1999-11-01

    Ozone (O3) deleteriously affects organisms ranging from humans to crop plants, yet little is understood regarding the underlying mechanisms. In plants, O3 decreases CO2 assimilation, but whether this could result from direct O3 action on guard cells remained unknown. Potassium flux causes osmotically driven changes in guard cell volume that regulate apertures of associated microscopic pores through which CO2 is supplied to the photosynthetic mesophyll tissue. We show in Vicia faba that O3 inhibits (i) guard cell K+ channels that mediate K+ uptake that drives stomatal opening; (ii) stomatal opening in isolated epidermes; and (iii) stomatal opening in leaves, such that CO2 assimilation is reduced without direct effects of O3 on photosynthetic capacity. Direct O3 effects on guard cells may have ecological and agronomic implications for plant productivity and for response to other environmental stressors including drought.

  15. The role of brassinosteroids and abscisic acid in stomatal development.

    PubMed

    Serna, Laura

    2014-08-01

    Gas exchange with the atmosphere is regulated through the stomata. This process relies on both the degree and duration of stomatal opening, and the number and patterning of these structures in the plant surface. Recent work has revealed that brassinosteroids and abscisic acid (ABA), which control stomatal opening, also repress stomatal development in cotyledons and leaves of at least some plants. It is speculated that, in Arabidopsis, these phytohormones control the same steps of this developmental process, most probably, through the regulation of the same mitogen-activated protein (MAP) kinase module. The conservation, in seeds plants, of components downstream of this module with MAP kinase target domains, suggests that these proteins are also regulated by these cascades, which, in turn, may be regulated by brassinosteroids and/or ABA.

  16. Efficacy of alum for treatment of recurrent aphthous stomatitis

    PubMed Central

    Rafieian, Nasrin; Abdolsamadi, Hamidreza; Moghadamnia, Aliakbar; Jazayeri, Mina; Seif-Rabiee, Mohammadali; Salmanzadeh, Mina; Radi, Shahrbanoo

    2016-01-01

    Background: Recurrent aphthous stomatitis (RAS) is the most common painful ulcers of oral mucosal which can cause many sufferings. Treatment of RAS often includes administration of corticosteroids, analgesics and regulators of the immune system. However, considering the side effects of these medications, even their topical application must be done with caution. Alum is used in traditional medicine for treatment of oral ulcers without significant side effect. This study sought to assess the effect of topical application of alum on aphthous ulcers. Methods: This clinical randomized double-blind placebo-controlled study was conducted on 50 females aged 21 to 27 years. Mucosal adhesive patches were prepared in two forms of basic and 7% alum-containing patches. Subjects in two groups of case and control randomly received the mucosal adhesive patches containing alum and the basic patches, respectively three times in five days. Duration of recovery, changes in size of lesion and severity of pain were recorded. Data were entered into SPSS Version 16 and analyzed using t-test. Results: The average period of full recovery was 7.52 days in the case and 12.2 days in the control groups; which was significantly different (p<0.001). Size of wound and severity of pain were significantly lower at one, three and five days posttreatment compared to baseline values before treatment in the case group (p<0.001) and the difference in this regard between the case and control groups was statistically significant. Conclusion: Alum can significantly decrease the size of aphthous lesions, severity of pain and expedite the recovery of patients with RAS. PMID:27757206

  17. Overexpression of the Mg-chelatase H subunit in guard cells confers drought tolerance via promotion of stomatal closure in Arabidopsis thaliana.

    PubMed

    Tsuzuki, Tomo; Takahashi, Koji; Tomiyama, Masakazu; Inoue, Shin-Ichiro; Kinoshita, Toshinori

    2013-01-01

    The Mg-chelatase H subunit (CHLH) has been shown to mediate chlorophyll biosynthesis, as well as plastid-to-nucleus and abscisic acid (ABA)-mediated signaling. A recent study using a novel CHLH mutant, rtl1, indicated that CHLH specifically affects ABA-induced stomatal closure, but also that CHLH did not serve as an ABA receptor in Arabidopsis thaliana. However, the molecular mechanism by which CHLH engages in ABA-mediated signaling in guard cells remains largely unknown. In the present study, we examined CHLH function in guard cells and explored whether CHLH expression might influence stomatal aperture. Incubation of rtl1 guard cell protoplasts with ABA induced expression of the ABA-responsive genes RAB18 and RD29B, as also observed in wild-type (WT) cells, indicating that CHLH did not affect the expression of ABA-responsive genes. Earlier, ABA was reported to inhibit blue light (BL)-mediated stomatal opening, at least in part through dephosphorylating/inhibiting guard cell H(+)-ATPase (which drives opening). Therefore, we immunohistochemically examined the phosphorylation status of guard cell H(+)-ATPase. Notably, ABA inhibition of BL-induced phosphorylation of H(+)-ATPase was impaired in rtl1 cells, suggesting that CHLH influences not only ABA-induced stomatal closure but also inhibition of BL-mediated stomatal opening by ABA. Next, we generated CHLH-GFP-overexpressing plants using CER6 promoter, which induces gene expression in the epidermis including guard cells. CHLH-transgenic plants exhibited a closed stomata phenotype even when brightly illuminated. Moreover, plant growth experiments conducted under water-deficient conditions showed that CHLH transgenic plants were more tolerant of drought than WT plants. In summary, we show that CHLH is involved in the regulation of stomatal aperture in response to ABA, but not in ABA-induced gene expression, and that manipulation of stomatal aperture via overexpression of CHLH in guard cells improves plant drought

  18. Improving Cloud-screening for Global Nighttime Lights Composites Using the VIIRS Day/Night Band

    NASA Astrophysics Data System (ADS)

    Baugh, K.; Elvidge, C.; Zhizhin, M. N.; Hsu, F. C.

    2014-12-01

    The Earth Observation Group (EOG) at the National Oceanic Atmospheric Administration's National Geophysical Data Center (NOAA/NGDC) has built a 22 year record of annual global nighttime lights composites using data from the Defense Meteorological Satellite Program's Operational Linescan System (DMSP-OLS). Using the newly available data from the Visible Infrared Imaging Radiometer Suite (VIIRS) Day/Night Band (DNB) allows EOG to extend this record beyond the life of the DMSP-OLS sensors, and create vastly improved products due to the increased spatial resolution and dynamic range of the DNB over the OLS sensor. Creation of high quality nighttime lights composites requires filtering of data degraded by th presence of clouds, heavy aerosols, or other atmospheric conditions that alter the sharpness and brightness of the nighttime light signal. The VIIRS Cloud-Mask (VCM) product is currently being used to define cloud-impacted regions in the creation of VIIRS DNB nighttime lights composites. Artifacts in the VCM, however, allow for some known cloud-impacted regions to be included in the nighttime lights composites, and conversely some known cloud-free regions to be excluded from the nighttime lights composites. This study investigates alternative methods to define regions of the nighttime DNB imagery that are impacted by atmospheric conditions. The first method filters the DNB using a spectral sharpness index. The second method examines shape of peaks in the DNB imagery to assess atmospheric impacts on the nighttime light signal. These two methods are compared against using the VCM for creation of nighttime lights composites using the VIIRS DNB.

  19. Self-focused thinking predicts nighttime physiological de-arousal.

    PubMed

    Takano, Keisuke; Ueno, Mayumi; Tanno, Yoshihiko

    2014-03-01

    Excessive focus on the internal self has maladaptive consequences for mental and physical health. Although the emotional functions of self-focus have been well established, no study has examined physiological arousal during the daily experience of self-focused thinking. The present study investigates the association between self-focus and autonomic activity using the experience sampling method with ambulatory monitoring of heart rate variability (HRV). Forty-five students reported the content of their thoughts during their daily activities while their heart rate (HR) was being recorded. Multilevel modeling analyses showed that HRV was lower (and HR was higher) over the sampling day if participants engaged in more self-focus, while HRV increased (and HR decreased) from midday to nighttime if participants did not engage in self-focused thinking. These results suggest that self-focus at night is associated with increased physiological arousal, and leads to inhibition of de-arousal associated with normal sleep processes. Implications for insomnia are discussed.

  20. Nighttime Aerosol Optical Depth Variability From Astronomical Photometry

    NASA Astrophysics Data System (ADS)

    Musat, I. C.; Ellingson, R. G.

    2006-12-01

    A technique for determination of the short-term (6 minutes intervals) variability of the aerosol optical depth (AOD) during nighttime from broadband visible measurements of star irradiances during clear nights was developed for the instrument called the Whole Sky Imager (WSI), placed at the Atmospheric Radiation Measurement (ARM) observation site in Oklahoma. The AOD is inferred indirectly from simultaneous observations of extinction of stars having different colors (spectra) and different elevations above the horizon, and takes into account the other sources for starlight attenuation in the atmosphere which might be present and which are measured by other instruments at the site at compatible timescales (e.g., precipitable water vapor content, columnar ozone amount, observed atmospheric stratification). The total error of the new method is a combination of the absolute star flux measurement error with the WSI and a systematic error in the models assumed for the other atmospheric components causing the starlight extinction. The relative error in the aerosol optical depth determined through this method is found to be below 4%. For the validation of the results, the comparison of the aerosol optical depth measured with the Lidar at 10 minutes intervals (at 355nm) with the AOD determined from WSI (in visible) shows a good agreement for the data in the interval studied (1999-2003).

  1. High-performance LLLTV CCD camera for nighttime pilotage

    NASA Astrophysics Data System (ADS)

    Williams, George M., Jr.

    1992-06-01

    Nighttime, nap-of-the-earth pilotage requires information from several sensors including thermal and image intensified sensors. Traditionally, the thermal imagery is displayed on a CRT; the image intensified imagery is displayed with a night vision goggle (NVG), a direct- view device worn immediately in front of the pilot''s eyes. If electronic output data from the image intensifier could be displayed on a CRT, the pilot''s safety and mission effectiveness would be greatly enhanced. Conventional approaches to using charge coupled devices fiberoptically coupled to image intensifier tubes have failed to provide the resolution, contrast, and sensitivity that pilots are accustomed to with night vision goggles. To produce image intensified sensors with performance comparable to an NVG, an intensified sensor that is optimized for coupling to solid state sensors and eliminates all fiberoptic-to-fiberoptic interfaces was fabricated. The Integrated Taper Assembly (ITA) sensor has a fiberoptic taper built into the vacuum of the image tube. The fiberoptic taper minifies the 18 or 25 millimeter (mm) output of the image intensifier tube to the 11 mm diagonal of the high resolution CCD. This requires one optical coupling -- at the CCD surface. By offering high resolution, high sensitivity, and a simplified optical path, the ITA image intensifier overcomes the shortcomings that normally limit the performance of intensified CCD cameras.

  2. Nighttime removal of NOx in the summer marine boundary layer

    NASA Astrophysics Data System (ADS)

    Brown, S. S.; Dibb, J. E.; Stark, H.; Aldener, M.; Vozella, M.; Whitlow, S.; Williams, E. J.; Lerner, B. M.; Jakoubek, R.; Middlebrook, A. M.; DeGouw, J. A.; Warneke, C.; Goldan, P. D.; Kuster, W. C.; Angevine, W. M.; Sueper, D. T.; Quinn, P. K.; Bates, T. S.; Meagher, J. F.; Fehsenfeld, F. C.; Ravishankara, A. R.

    2004-04-01

    The nitrate radical, NO3, and dinitrogen pentoxide, N2O5, are two important components of nitrogen oxides that occur predominantly at night in the lower troposphere. Because a large fraction of NO2 reacts to form NO3 and N2O5 during the course of a night, their fate is an important determining factor to the overall fate of NOx (=NO and NO2). As a comprehensive test of nocturnal nitrogen oxide chemistry, concentrations of O3, NO, NO2, NO3, N2O5, HNO3 and a host of other relevant compounds, aerosol abundance and composition, and meteorological conditions were measured in the marine boundary layer from the NOAA research vessel Ronald H. Brown off the East Coast of the United States as part of the New England Air Quality Study (NEAQS) during the summer of 2002. The results confirm the prominent role of NO3 and N2O5 in converting NOx to HNO3 at night with an efficiency on par with daytime photochemical conversion. The findings demonstrate the large role of nighttime chemistry in determining the NOx budget and consequent production of ozone.

  3. Simulated midlatitude summer nighttime anomaly in realistic geomagnetic fields

    NASA Astrophysics Data System (ADS)

    Ren, Zhipeng; Wan, Weixing; Liu, Libo; Le, Huijun; He, Maosheng

    2012-03-01

    In the present work, using the three-dimensional theoretical ionospheric model of the Earth in Institute of Geology and Geophysics, Chinese Academy of Sciences (TIME3D-IGGCAS), we simulate the temporal-spatial distribution of the midlatitude summer nighttime anomaly (MSNA) and the influences of thermospheric meridional and zonal winds on the formation of MSNA. MSNA mainly appears in three distinct regions, the East Asian region, the northern Atlantic-Europe region and the South Pacific region. MSNA in the South Pacific region is obviously stronger than that in the other two regions. In these three regions, MSNA not only occurs in local summer, but also often occurs in Equinox. Through lifting up or lowering the F region ionization, thermospheric winds mainly drive the formation of MSNA. In the East Asian region and the northern Atlantic-Europe region, MSNA are mainly driven by the thermospheric meridional wind, and the influence of the thermospheric zonal wind can be neglected. However, although MSNA in the South Pacific region (or Weddell Sea Anomaly) are mainly driven by the thermospheric meridional wind, the thermospheric zonal wind also plays an important role in the formation of MSNA.

  4. Nighttime ion composition measurements at the geomagnetic equator

    NASA Technical Reports Server (NTRS)

    Goldberg, R. A.; Aikin, A. C.

    1973-01-01

    Two ion composition profiles, representative of the nighttime equatorial ionosphere between 90 km and 300 km, are presented. These profiles were obtained by two rocket-borne ion mass spectrometers on a single night for solar zenith angles of 112 deg and 165 deg. For both flights, the principal ion above 200 km is O(+). The downward drift of the atomic ions O(+) and N(+), coinciding with the postsunset lowering of the F2 peak, is observed through an enhancement of the density of O(+) at altitudes above 200 km and N(+) above 240 km. Below the drift region, O(+) and N(+) are observed in concentrations larger than expected. The NO(+) altitude distribution retains its shape throughout the night, and below 210 km, is the principal ion. The behavior of O2(+) can be explained by the O(+), electron density and theoretical neutral nitric oxide concentrations. Light metallic ions, including Mg(+), Na(+), and possibly Si(+), are observed to altitudes approaching 300 km and are affected by vertical drift.

  5. Modeling Global Urbanization Supported by Nighttime Light Remote Sensing

    NASA Astrophysics Data System (ADS)

    Zhou, Y.

    2015-12-01

    Urbanization, a major driver of global change, profoundly impacts our physical and social world, for example, altering carbon cycling and climate. Understanding these consequences for better scientific insights and effective decision-making unarguably requires accurate information on urban extent and its spatial distributions. In this study, we developed a cluster-based method to estimate the optimal thresholds and map urban extents from the nighttime light remote sensing data, extended this method to the global domain by developing a computational method (parameterization) to estimate the key parameters in the cluster-based method, and built a consistent 20-year global urban map series to evaluate the time-reactive nature of global urbanization (e.g. 2000 in Fig. 1). Supported by urban maps derived from nightlights remote sensing data and socio-economic drivers, we developed an integrated modeling framework to project future urban expansion by integrating a top-down macro-scale statistical model with a bottom-up urban growth model. With the models calibrated and validated using historical data, we explored urban growth at the grid level (1-km) over the next two decades under a number of socio-economic scenarios. The derived spatiotemporal information of historical and potential future urbanization will be of great value with practical implications for developing adaptation and risk management measures for urban infrastructure, transportation, energy, and water systems when considered together with other factors such as climate variability and change, and high impact weather events.

  6. Are fern stomatal responses to different stimuli coordinated? Testing responses to light, vapor pressure deficit, and CO2 for diverse species grown under contrasting irradiances.

    PubMed

    Creese, Chris; Oberbauer, Steve; Rundel, Phil; Sack, Lawren

    2014-10-01

    The stomatal behavior of ferns provides an excellent system for disentangling responses to different environmental signals, which balance carbon gain against water loss. Here, we measured responses of stomatal conductance (gs ) to irradiance, CO2 , and vapor pressure deficit (VPD) for 13 phylogenetically diverse species native to open and shaded habitats, grown under high- and low-irradiance treatments. We tested two main hypotheses: that plants adapted and grown in high-irradiance environments would have greater responsiveness to all stimuli given higher flux rates; and that species' responsiveness to different factors would be correlated because of the relative simplicity of fern stomatal control. We found that species with higher light-saturated gs had larger responses, and that plants grown under high irradiance were more responsive to all stimuli. Open habitat species showed greater responsiveness to irradiance and CO2 , but lower responsiveness to VPD; a case of plasticity and adaptation tending in different directions. Responses of gs to irradiance and VPD were positively correlated across species, but CO2 responses were independent and highly variable. The novel finding of correlations among stomatal responses to different stimuli suggests coordination of hydraulic and photosynthetic signaling networks modulating fern stomatal responses, which show distinct optimization at growth and evolutionary time-scales.

  7. The Arabidopsis GTL1 Transcription Factor Regulates Water Use Efficiency and Drought Tolerance by Modulating Stomatal Density via Transrepression of SDD1[W][OA

    PubMed Central

    Yoo, Chan Yul; Pence, Heather E.; Jin, Jing Bo; Miura, Kenji; Gosney, Michael J.; Hasegawa, Paul M.; Mickelbart, Michael V.

    2010-01-01

    A goal of modern agriculture is to improve plant drought tolerance and production per amount of water used, referred to as water use efficiency (WUE). Although stomatal density has been linked to WUE, the causal molecular mechanisms have yet to be determined. Arabidopsis thaliana GT-2 LIKE 1 (GTL1) loss-of-function mutations result in increased water deficit tolerance and higher integrated WUE by reducing daytime transpiration without a demonstrable reduction in biomass accumulation. gtl1 plants had higher instantaneous WUE that was attributable to ~25% lower transpiration and stomatal conductance but equivalent CO2 assimilation. Lower transpiration was associated with higher STOMATAL DENSITY AND DISTRIBUTION1 (SDD1) expression and an ~25% reduction in abaxial stomatal density. GTL1 expression occurred in abaxial epidermal cells where the protein was localized to the nucleus, and its expression was downregulated by water stress. Chromatin immunoprecipitation analysis indicated that GTL1 interacts with a region of the SDD1 promoter that contains a GT3 box. An electrophoretic mobility shift assay was used to determine that the GT3 box is necessary for the interaction between GTL1 and the SDD1 promoter. These results establish that GTL1 negatively regulates WUE by modulating stomatal density via transrepression of SDD1. PMID:21169508

  8. Nighttime Breastfeeding Behavior Is Associated with More Nocturnal Sleep among First-Time Mothers at One Month Postpartum

    PubMed Central

    Doan, Therese; Gay, Caryl L.; Kennedy, Holly P.; Newman, Jack; Lee, Kathryn A.

    2014-01-01

    Study Objective: To describe sleep duration and quality in the first month postpartum and compare the sleep of women who exclusively breastfed at night to those who used formula. Methods: We conducted a longitudinal study in a predominantly low-income and ethnically diverse sample of 120 first-time mothers. Both objective and subjective measures of sleep were obtained using actigraphy, diary, and self-report data. Measures were collected in the last month of pregnancy and at one month postpartum. Infant feeding diaries were used to group mothers by nighttime breastfeeding behavior. Results: Mothers who used at least some formula at night (n = 54) and those who breastfed exclusively (n = 66) had similar sleep patterns in late pregnancy. However, there was a significant group difference in nocturnal sleep at one month postpartum as measured by actigraphy. Total nighttime sleep was 386 ± 66 minutes for the exclusive breastfeeding group and 356 ± 67 minutes for the formula group. The groups did not differ with respect to daytime sleep, wake after sleep onset (sleep fragmentation), or subjective sleep disturbance at one month postpartum. Conclusion: Women who breastfed exclusively averaged 30 minutes more nocturnal sleep than women who used formula at night, but measures of sleep fragmentation did not differ. New mothers should be encouraged to breastfeed exclusively since breastfeeding may promote sleep during postpartum recovery. Further research is needed to better understand how infant feeding method affects maternal sleep duration and fragmentation. Citation: Doan T; Gay CL; Kennedy HP; Newman J; Lee KA. Nighttime breastfeeding behavior is associated with more nocturnal sleep among first-time mothers at one month postpartum. J Clin Sleep Med 2014;10(3):313-319. PMID:24634630

  9. Jasmonate-mediated stomatal closure under elevated CO2 revealed by time-resolved metabolomics

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Foliar stomatal movements are critical for regulating plant water status and gas exchange. Elevated carbon dioxide (CO2) concentrations are known to induce stomatal closure. However, current knowledge on CO2 signal transduction in stomatal guard cells is limited. Here we report the metabolomic respo...

  10. Regulation of stomatal opening by the guard cell expansin AtEXPA1.

    PubMed

    Wei, Peng-Cheng; Zhang, Xiu-Qing; Zhao, Ping; Wang, Xue-Chen

    2011-05-01

    Stomatal movement is strictly regulated by various intracellular and extracellular factors in response environmental signals. In our recent study, we found that an Arabidopsis guard cell expressed expansin, AtEXPA1, regulates stomatal opening by altering the structure of the guard cell wall. This addendum proposes a mechanism by which guard cell expansins regulate stomatal movement.

  11. Design Calibration and Field Use of a Stomatal Diffusion Porometer

    PubMed Central

    Kanemasu, E. T.; Thurtell, G. W.; Tanner, C. B.

    1969-01-01

    Modifications of the design and calibration procedure of a diffusion porometer permit determinations of stomatal resistance which agree well with results obtained by leaf energy balance. The energy balance and the diffusion porometer measurements indicate that the boundary layer resistances of leaves in the field are substantially less than those predicted from heat transport formulas based on wind flow and leaf size. PMID:16657142

  12. Burdock fructooligosaccharide induces stomatal closure in Pisum sativum.

    PubMed

    Guo, Yanling; Guo, Moran; Zhao, Wenlu; Chen, Kaoshan; Zhang, Pengying

    2013-09-12

    Burdock fructooligosaccharide (BFO) isolated from the root tissue of Arctium lappa is a reserve carbohydrate that can induce resistance against a number of plant diseases. Stomatal closure is a part of plant innate immune response to restrict bacterial invasion. In this study, the effects of BFO on stomata movement in Pisum sativum and the possible mechanisms were studied with abscisic acid (ABA) as a positive control. The results showed that BFO could induce stomatal closure accompanied by ROS and NO production, as is the case with ABA. BFO-induced stomatal closure was inhibited by pre-treatment with L-NAME (N(G)-nitro-L-arginine methyl ester, hydrochloride; nitric oxide synthase inhibitor) and catalase (hydrogen peroxide scavenger). Exogenous catalase completely restricted BFO-induced production of ROS and NO in guard cells. In contrast, L-NAME prevented the rise in NO levels but only partially restricted the ROS production. These results indicate that BFO-induced stomatal closure is mediated by ROS and ROS-dependent NO production.

  13. Burdock fructooligosaccharide induces stomatal closure in Pisum sativum.

    PubMed

    Guo, Yanling; Guo, Moran; Zhao, Wenlu; Chen, Kaoshan; Zhang, Pengying

    2013-09-12

    Burdock fructooligosaccharide (BFO) isolated from the root tissue of Arctium lappa is a reserve carbohydrate that can induce resistance against a number of plant diseases. Stomatal closure is a part of plant innate immune response to restrict bacterial invasion. In this study, the effects of BFO on stomata movement in Pisum sativum and the possible mechanisms were studied with abscisic acid (ABA) as a positive control. The results showed that BFO could induce stomatal closure accompanied by ROS and NO production, as is the case with ABA. BFO-induced stomatal closure was inhibited by pre-treatment with L-NAME (N(G)-nitro-L-arginine methyl ester, hydrochloride; nitric oxide synthase inhibitor) and catalase (hydrogen peroxide scavenger). Exogenous catalase completely restricted BFO-induced production of ROS and NO in guard cells. In contrast, L-NAME prevented the rise in NO levels but only partially restricted the ROS production. These results indicate that BFO-induced stomatal closure is mediated by ROS and ROS-dependent NO production. PMID:23911508

  14. Stomatal closure: the old guard takes up the SLAC.

    PubMed

    Chater, Caspar; Gray, Julie E

    2015-03-30

    Flowering plant stomata close through passive dehydration or by active pumping of anions through SLAC, a phospho-activated membrane channel. A new study reports that moss likely utilise this same mechanism, and thus supports an early origin for SLAC-mediated active stomatal control.

  15. Stomatal Control and Leaf Thermal and Hydraulic Capacitances under Rapid Environmental Fluctuations

    PubMed Central

    Schymanski, Stanislaus J.; Or, Dani; Zwieniecki, Maciej

    2013-01-01

    Leaves within a canopy may experience rapid and extreme fluctuations in ambient conditions. A shaded leaf, for example, may become exposed to an order of magnitude increase in solar radiation within a few seconds, due to sunflecks or canopy motions. Considering typical time scales for stomatal adjustments, (2 to 60 minutes), the gap between these two time scales raised the question whether leaves rely on their hydraulic and thermal capacitances for passive protection from hydraulic failure or over-heating until stomata have adjusted. We employed a physically based model to systematically study effects of short-term fluctuations in irradiance on leaf temperatures and transpiration rates. Considering typical amplitudes and time scales of such fluctuations, the importance of leaf heat and water capacities for avoiding damaging leaf temperatures and hydraulic failure were investigated. The results suggest that common leaf heat capacities are not sufficient to protect a non-transpiring leaf from over-heating during sunflecks of several minutes duration whereas transpirative cooling provides effective protection. A comparison of the simulated time scales for heat damage in the absence of evaporative cooling with observed stomatal response times suggested that stomata must be already open before arrival of a sunfleck to avoid over-heating to critical leaf temperatures. This is consistent with measured stomatal conductances in shaded leaves and has implications for water use efficiency of deep canopy leaves and vulnerability to heat damage during drought. Our results also suggest that typical leaf water contents could sustain several minutes of evaporative cooling during a sunfleck without increasing the xylem water supply and thus risking embolism. We thus submit that shaded leaves rely on hydraulic capacitance and evaporative cooling to avoid over-heating and hydraulic failure during exposure to typical sunflecks, whereas thermal capacitance provides limited protection

  16. Resource use and efficiency, and stomatal responses to environmental drivers of oak and pine species in an Atlantic Coastal Plain forest

    PubMed Central

    Renninger, Heidi J.; Carlo, Nicholas J.; Clark, Kenneth L.; Schäfer, Karina V. R.

    2015-01-01

    Pine-oak ecosystems are globally distributed even though differences in anatomy and leaf habit between many co-occurring oaks and pines suggest different strategies for resource use, efficiency and stomatal behavior. The New Jersey Pinelands contain sandy soils with low water- and nutrient-holding capacity providing an opportunity to examine trade-offs in resource uptake and efficiency. Therefore, we compared resource use in terms of transpiration rates and leaf nitrogen content and resource-use efficiency including water-use efficiency (WUE) via gas exchange and leaf carbon isotopes and photosynthetic nitrogen-use efficiency (PNUE) between oaks (Quercus alba, Q. prinus, Q. velutina) and pines (Pinus rigida, P. echinata). We also determined environmental drivers [vapor pressure deficit (VPD), soil moisture, solar radiation] of canopy stomatal conductance (GS) estimated via sap flow and stomatal sensitivity to light and soil moisture. Net assimilation rates were similar between genera, but oak leaves used about 10% more water and pine foliage contained about 20% more N per unit leaf area. Therefore, oaks exhibited greater PNUE while pines had higher WUE based on gas exchange, although WUE from carbon isotopes was not significantly different. For the environmental drivers of GS, oaks had about 10% lower stomatal sensitivity to VPD normalized by reference stomatal conductance compared with pines. Pines exhibited a significant positive relationship between shallow soil moisture and GS, but only GS in Q. velutina was positively related to soil moisture. In contrast, stomatal sensitivity to VPD was significantly related to solar radiation in all oak species but only pines at one site. Therefore, oaks rely more heavily on groundwater resources but have lower WUE, while pines have larger leaf areas and nitrogen acquisition but lower PNUE demonstrating a trade-off between using water and nitrogen efficiently in a resource-limited ecosystem. PMID:25999966

  17. Ecophysiological relevance of cuticular transpiration of deciduous and evergreen plants in relation to stomatal closure and leaf water potential.

    PubMed

    Burghardt, Markus; Riederer, Markus

    2003-08-01

    The water permeability of the leaves of three deciduous plants (Acer campestre, Fagus sylvatica, Quercus petraea) and two evergreen plants (Hedera helix, Ilex aquifolium) was analysed in order to assess its role as a mechanism of drought resistance. Cuticular permeances were determined by measurement of the water loss through adaxial, astomatous leaf surfaces. Minimum conductances after complete stomatal closure were obtained by leaf drying curves. The comparison of the water permeabilities determined with these two experimental systems revealed good agreement in the case of Acer, Fagus, Quercus, and Ilex. For Hedera the minimum conductance was 3-fold higher than the cuticular permeance indicating a significant contribution of residual stomatal transpiration. The leaf water potential was measured as a function of water content and analysed by pressure-volume curves. The influence of water potential as a component of the driving force for transpirational water loss was assessed in order to identify modifications of the cuticular barrier by the leaf water content. The ecophysiological meaning of the water relations parameters describing transpiration under drought conditions (cuticular transpiration, minimum transpiration, residual stomatal transpiration, effect of leaf water content on transpiration) and the water relations parameters derived from pressure-volume curves (osmotic potential at full saturation, turgor loss point, bulk modulus of elasticity) are discussed with regard to adaptations for drought resistance.

  18. Effects of Nighttime Light Radiance on the Sleep of the General Population

    NASA Technical Reports Server (NTRS)

    Ohayon, Maurice M.; Milesi, Cristina

    2015-01-01

    The objectives of this study is to verify if the exposure to greater nighttime radiance is associated with changes in the sleep/wake schedule and with greater sleep disturbances. Methods: The target population was the adults (18 years and older) living in California, USA. This represents 24 million of inhabitants. A total of 3,104 subjects participated in the survey (participation rate 85.6%). The participants were interviewed by telephone using the Sleep-EVAL system. The interviews covered several topics including sleeping habits, sleep quality, sleep disturbances, physical symptoms related to menopause. Chronic insomnia was defined as difficulty initiating or maintaining sleep for at least 3 months. Global nighttime light emissions have been collected by the Defense Meteorological Satellite Program's Operational Linescan System (DMSP/OLS) sensors. We extracted the radiance calibrated nighttime lights corresponding to the date of the interviews for a three by three window centered on each coordinate corresponding to an interview address. Results: Dissatisfaction with sleep quantity and/or quality was associated with an increased nighttime radiance (p=0.02). Similarly, excessive sleepiness accompanied with impaired functioning was significantly associated with an increased nighttime radiance (p (is) less than 0.0001). The association remained significant after controlling for age, gender and use of a night lamp in the bedroom. Confusional arousals were also significantly associated with an increased nighttime radiance (p (is) less than 0.0001). Bedtime hour was linearly increasing with the intensity of nighttime radiance: the later the bedtime, the greater the nighttime radiance (p (is) less than 0.0001). Similarly, wakeup time became progressively later as the nighttime radiance increased (p (is) less than 0.0001). Both associations remained significant after controlling for age, gender and use of a night lamp in the bedroom. Circadian Rhythm Disorders were the

  19. Autophagy contributes to nighttime energy availability for growth in Arabidopsis.

    PubMed

    Izumi, Masanori; Hidema, Jun; Makino, Amane; Ishida, Hiroyuki

    2013-04-01

    Autophagy is an intracellular process leading to the vacuolar degradation of cytoplasmic components. Autophagic degradation of chloroplasts is particularly activated in leaves under conditions of low sugar availability. Here, we investigated the importance of autophagy in the energy availability and growth of Arabidopsis (Arabidopsis thaliana). autophagy-deficient (atg) mutants showed reduced growth under short-day conditions. This growth inhibition was largely relieved under continuous light or under short-day conditions combined with feeding of exogenous sucrose, suggesting that autophagy is involved in energy production at night for growth. Arabidopsis accumulates starch during the day and degrades it for respiration at night. Nighttime energy availability is perturbed in starchless mutants, in which a lack of starch accumulation causes a transient sugar deficit at night. We generated starchless and atg double mutants and grew them under different photoperiods. The double mutants showed more severe phenotypes than did atg or starchless single mutants: reduced growth and early cell death in leaves were observed when plants were grown under 10-h photoperiods. Transcript analysis of dark-inducible genes revealed that the sugar starvation symptoms observed in starchless mutants became more severe in starchless atg double mutants. The contents of free amino acids (AAs) increased, and transcript levels of several genes involved in AA catabolism were elevated in starchless mutant leaves. The increases in branched-chain AA and aromatic AA contents were partially compromised in starchless atg double mutants. We conclude that autophagy can contribute to energy availability at night by providing a supply of alternative energy sources such as AAs.

  20. Characteristics of the Nighttime Hospital Bedside Care Environment (Sound, Light, and Temperature) for Children with Cancer

    PubMed Central

    Linder, Lauri A.; Christian, Becky J.

    2010-01-01

    Background Children with cancer must cope not only with their disease and its treatment but also the environment in which treatment is given. The intensities of sound and light levels required to perform necessary patient care may result in a disruptive nighttime care environment. Objective The purpose of this study was to describe nighttime patterns of environmental factors, sound light, and temperature levels, at the bedside of children with cancer receiving inpatient chemotherapy. Methods Participants were 15 school-age children receiving chemotherapy on an inpatient pediatric oncology unit. Sound, light, and temperature in the child’s room were measured continuously using a digital sound pressure level meter and an external channel data logger. Results Mean nighttime sound levels were 49.5 dB (SD=3.1; range 34.6–84.8 dB). Sound and light intensity were greatest early in the shift and decreased through the night. A basic mixed linear model identified significant main effects of time of night for both sound (F=50.42, p<.01) and light (F=12.43, p<.01). Conclusions Study findings identified a bedside care environment with persistently elevated sound levels and abrupt increases in sound intensity throughout the night. Such a disruptive nighttime environment is not conducive to restful nighttime sleep and may serve as an additional source of physiologic and psychologic stress for hospitalized children with cancer. Implications for Practice Efforts are needed to identify modifiable sources of nighttime sound and develop interventions to reduce nighttime sound. Collaborative efforts to organize clinical care to minimize nighttime disruptions may lead to to reduced bedside sound levels. PMID:21522058

  1. Plasticity in stomatal size and density of potato leaves under different irrigation and phosphorus regimes.

    PubMed

    Sun, Yanqi; Yan, Fei; Cui, Xiaoyong; Liu, Fulai

    2014-09-01

    The morphological features of stomata including their size and density could be modulated by environmental cues; however, the underlying mechanisms remain largely elusive. Here, the effect of different irrigation and phosphorus (P) regimes on stomatal size (SS) and stomatal density (SD) of potato leaves was investigated. The plants were grown in split-root pots under two P fertilization rates (viz., 0 and 100mgkg(-1) soil, denoted as P0 and P1, respectively) and subjected to full (FI), deficit (DI), and partial root-zone drying (PRD) irrigation regimes. Results showed that SS and SD were unresponsive to P but significantly affected by the irrigation treatment. FI plants had the largest SS, followed by DI, and PRD the smallest; and the reverse was the case for SD. Compared to FI and DI, PRD plants had significantly lower values of specific leaf area (SLA) and leaf carbon isotope discrimination (Δ(13)C) under P0. Midday leaf water potential (Ψleaf) and stomatal conductance (gs) was similar for DI and PRD, which was significantly lower than that of FI. Leaf contents of C, N, K, Ca and Mg were higher in PRD than in DI plants, particularly under P0. When analyzed across the three irrigation regimes, it was found that the P1 plants had significantly higher leaf contents of P and Mg, but significantly lower leaf K content compared to the P0 plants. Linear correlation analyses revealed that SS was positively correlated with Ψleaf and Δ(13)C; whereas SD was negatively correlated with Ψleaf, Δ(13)C and SLA, and positively correlated with leaf C, N and Ca contents. And gs was positively correlated with SS but negatively correlated with SD. Collectively, under low P level, the smaller and denser stomata in PRD plants may bring about a more efficient stomatal control over gas exchange, hereby potentially enhance water-use efficiency as exemplified by the lowered leaf Δ(13)C under fluctuating soil moisture conditions.

  2. Effect of Obstructed Translocation on Leaf Abscisic Acid, and Associated Stomatal Closure and Photosynthesis Decline 1

    PubMed Central

    Setter, Tim L.; Brun, William A.; Brenner, Mark L.

    1980-01-01

    Pod removal or petiole girdling, which causes obstruction of translocation, was found in our previous study to cause reduced rates of photosynthesis in soybean leaves due to stomatal closure. The purpose of this research was to determine the involvement of photoassimilate accumulation and leaf abscisic acid (ABA) levels in the mechanism of stomatal closure induced by such treatments. Leaf glucose and sucrose levels increased during the initial 12-hour period after depodding or petiole girdling. Starch, which represents a much larger pool of leaf carbohydrate, was not perceptibly increased above control levels during the 12-hour posttreatment period. When leaflets were exposed to nonphotosynthetic environments (shading or CO2-free air) for a 24-hour period after the translocation-obstructing treatments were applied and then returned to normal light or CO2 concentration, stomatal diffusive conductivity was reduced 65% and 85% with depodding and girdling, respectively. These reductions were comparable to those previously observed without an intervening nonphotosynthetic exposure, thus indicating that photosynthate accumulations were not necessary for the observed response. Free and bound ABA (released on alkaline hydrolysis) were determined by gas liquid chromatography with electron capture detection following preparative high performance liquid chromatography. Free ABA in monitored leaves increased almost 10-fold 48 hours after complete depodding and 25-fold 24 hours after petiole girdling of such leaves. By 3 hours after treatment, in a time course study, free ABA had increased 2-fold above control values in depodded and 5-fold in girdled leaves. Leaf concentrations of bound ABA did not appear to be related to the treatment effects on stomata. Thus, the translocation-obstructing treatments cause an increased level of ABA by a mechanism not involving accumulation of photoassimilate. Increased leaf ABA levels, which were independent of water stress or leaf water

  3. Nighttime warming enhances drought resistance of plant communities in a temperate steppe

    PubMed Central

    Yang, Zhongling; Jiang, Lin; Su, Fanglong; Zhang, Qian; Xia, Jianyang; Wan, Shiqiang

    2016-01-01

    Drought events could have profound influence on plant community structure and ecosystem function, and have subsequent impacts on community stability, but we know little about how different climate warming scenarios affect community resistance and resilience to drought. Combining a daytime and nighttime warming experiment in the temperate steppe of north China with a natural drought event during the study period, we tested how daytime and nighttime warming influences drought resistance and resilience. Our results showed that the semi-arid steppe in north China was resistant to both daytime and nighttime warming, but vulnerable to drought. Nighttime warming, but not daytime warming, enhanced community resistance to drought via stimulating carbon sequestration, whereas neither daytime nor nighttime warming affected community resilience to drought. Large decline in plant community cover, primarily caused by the reduction in the cover of dominant and rare species rather than subordinate species during drought, did not preclude rapid ecosystem recovery. These findings suggest that nighttime warming may facilitate ecosystem sustainability and highlight the need to assess the effects of climate extremes on ecosystem functions at finer temporal resolutions than based on diurnal mean temperature. PMID:26987482

  4. Nighttime warming enhances drought resistance of plant communities in a temperate steppe

    NASA Astrophysics Data System (ADS)

    Yang, Zhongling; Jiang, Lin; Su, Fanglong; Zhang, Qian; Xia, Jianyang; Wan, Shiqiang

    2016-03-01

    Drought events could have profound influence on plant community structure and ecosystem function, and have subsequent impacts on community stability, but we know little about how different climate warming scenarios affect community resistance and resilience to drought. Combining a daytime and nighttime warming experiment in the temperate steppe of north China with a natural drought event during the study period, we tested how daytime and nighttime warming influences drought resistance and resilience. Our results showed that the semi-arid steppe in north China was resistant to both daytime and nighttime warming, but vulnerable to drought. Nighttime warming, but not daytime warming, enhanced community resistance to drought via stimulating carbon sequestration, whereas neither daytime nor nighttime warming affected community resilience to drought. Large decline in plant community cover, primarily caused by the reduction in the cover of dominant and rare species rather than subordinate species during drought, did not preclude rapid ecosystem recovery. These findings suggest that nighttime warming may facilitate ecosystem sustainability and highlight the need to assess the effects of climate extremes on ecosystem functions at finer temporal resolutions than based on diurnal mean temperature.

  5. Nighttime warming enhances drought resistance of plant communities in a temperate steppe.

    PubMed

    Yang, Zhongling; Jiang, Lin; Su, Fanglong; Zhang, Qian; Xia, Jianyang; Wan, Shiqiang

    2016-01-01

    Drought events could have profound influence on plant community structure and ecosystem function, and have subsequent impacts on community stability, but we know little about how different climate warming scenarios affect community resistance and resilience to drought. Combining a daytime and nighttime warming experiment in the temperate steppe of north China with a natural drought event during the study period, we tested how daytime and nighttime warming influences drought resistance and resilience. Our results showed that the semi-arid steppe in north China was resistant to both daytime and nighttime warming, but vulnerable to drought. Nighttime warming, but not daytime warming, enhanced community resistance to drought via stimulating carbon sequestration, whereas neither daytime nor nighttime warming affected community resilience to drought. Large decline in plant community cover, primarily caused by the reduction in the cover of dominant and rare species rather than subordinate species during drought, did not preclude rapid ecosystem recovery. These findings suggest that nighttime warming may facilitate ecosystem sustainability and highlight the need to assess the effects of climate extremes on ecosystem functions at finer temporal resolutions than based on diurnal mean temperature. PMID:26987482

  6. Clinical evaluation of the essential oil of Pelargonium graveolens for the treatment of denture stomatitis

    PubMed Central

    Sabzghabaee, Ali Mohammad; Shirdare, Zahra; Ebadian, Behnaz; Aslani, Abolfazl; Ghannadi, Alireza

    2011-01-01

    Background: Natural products are proved to play a good role as an alternative to synthetic chemicals in clinical conditions. Previous studies showed that Pelargonium graveolens has anti-inflammatory and antifungal activity against Candida albicans. The aim of this study was to evaluate the efficacy of essential oil of Pelargonium graveolens in the treatment of denture stomatitis. Materials and Methods: In this double-blind randomized clinical trial conducted in Isfahan (Iran), 80 (51 females and 29 males) eligible wearers of complete denture were included. According to the patients’ profiles number, they randomly divided to 2 groups of 40 patients’ case and 40 patients control treated with Pelargonium 1% gel or placebo, respectively. They were recommended to apply the gel twice daily for a 14-day course. All data were analyzed using SPSS® for windows (v.18). We have used the χ2 test for analyzing qualitative and Student t-test for quantitative data considering as P<0.05 as significant. Results: According to mycological data and clinical observation after treatment in the case group, 34% of patients had been improved completely, 56% partially and 10% had no improvement. In the control group, 5% of patients had complete recovery, 25% partial recovery, and 70% no improvement. A significant reduction in fungal growth was observed in case group rather than the control group (P value<0.0001). Conclusion: It seems that the application of a 1% Geranium oil topical gel formulation is more effective than placebo in the treatment of denture stomatitis. PMID:23372587

  7. Inconsolable night-time awakening: beyond night terrors.

    PubMed

    Snyder, David M; Goodlin-Jones, Beth L; Pionk, Mary Jane; Stein, Martin T

    2008-08-01

    Sophia is a 3-year-old girl who was brought to her pediatrician by her parents who were concerned about inconsolable night-time awakening. Her mother indicated that she has frequent (>6), early nocturnal awakenings accompanied by screaming and crying lasting up to 1 hour since her birth. These episodes increased in intensity and frequency in the past year since the birth of her brother. With a bedtime routine (a cup of water by bedside with a washcloth and touching mother's nose, chin, and cheeks), Sophia falls asleep easily; however, within 1 hour she awakes screaming and flailing unaware of her surroundings and unable to be comforted. There are no tonic-clonic movements. Prior interventions, including a sleep coach and "letting Sophia cry it out," did not change her sleep pattern. Sophia's mother reports that she needs to be on a specific daily routine including set times for awakening, activity, snacks, naps, and meals. Diversion from the routine and separation from her mother results in a tantrum (kicking, hitting, screaming, and inconsolability) often lasting more than 30 minutes. Sophia was born after an uncomplicated 37-week gestation. Neonatal hyperbilirubinemia required readmission for 24 hours of phototherapy; serum bilirubin levels were performed daily for 3 weeks after discharge. At 6 weeks, daily episodes of screaming, inconsolability, forceful vomiting, and inability to sleep led to a diagnosis of gastroesophageal reflux. Medication trials were not successful, but the symptoms resolved by 5 months. Formula intolerance and difficulty swallowing and chewing different textures of solid food occurred in the first year. Occupational therapy was of "no benefit"; Sophia was overwhelmed by the activity and took a long time to warm up to the therapist. Her texture aversion resolved by 2 years of age. She prefers one-on-one play and has minimal interactions with other children. She has met all her developmental milestones appropriately and has no other health

  8. Solubilization and reconstitution of vesicular stomatitis virus envelope using octylglucoside.

    PubMed Central

    Paternostre, M; Viard, M; Meyer, O; Ghanam, M; Ollivon, M; Blumenthal, R

    1997-01-01

    Reconstituted vesicular stomatitis virus envelopes or virosomes are formed by detergent removal from solubilized intact virus. We have monitored the solubilization process of the intact vesicular stomatitis virus by the nonionic surfactant octylglucoside at various initial virus concentrations by employing turbidity measurements. This allowed us to determine the phase boundaries between the membrane and the mixed micelles domains. We have also characterized the lipid and protein content of the solubilized material and of the reconstituted envelope. Both G and M proteins and all of the lipids of the envelope were extracted by octylglucoside and recovered in the reconstituted envelope. Fusion activity of the virosomes tested either on Vero cells or on liposomes showed kinetics and pH dependence similar to those of the intact virus. Images FIGURE 4 PMID:9083672

  9. Remission of severe aphthous stomatitis of celiac disease with etanercept

    PubMed Central

    2013-01-01

    Celiac disease is a common autoimmune disease triggered by gluten-containing foods (wheat, barley and rye) in genetically predisposed individuals. We present a patient with celiac disease complicated by severe aphthous stomatitis resulting in impairing swallowing, chewing and speaking. This led to weight loss, psychosocial problems as well as inability to perform her work. A variety of topical and systemic medications used resulted in either no improvement or only partial alleviation of the patient’s symptoms. After informed consent, etanercept was initiated and resulted in complete remission of aphthous stomatitis, decrease in arthralgia and fatigue and considerable improvement in her quality of life. The use of newer biological agents for selected and severe manifestations of celiac disease may lead to improved morbidity in these patients, but more studies are needed to determine long-term efficacy as well as safety of these drugs in the mucosal and/or systemic complications of this disease. PMID:24365222

  10. Oral exfoliative cytology in female reverse smokers having stomatitis nicotina.

    PubMed

    Reddy, C R; Sarma, P R; Kameswari, V R

    1975-01-01

    1. The Karyopyknotic index of the palatal and lingual mucosa is increased in female reverse smokers when compared to non-smoking females. 2. The Karyopyknotic index of the buccal mucosa did not show any change in female reverse smokers when compared to non-smoking females. 3. The Karyopyknotic index did not show any change with age in the non-smoking females. 4. Very few cases show epithelial atypia in palatal smears from female reverse smokers having stomatitis nicotina.

  11. Within-catchment variation in regulation of water use by eucalypts, and the roles of stomatal anatomy and physiology

    NASA Astrophysics Data System (ADS)

    Gharun, Mana; Turnbull, Tarryn; Adams, Mark

    2014-05-01

    Understanding how environmental cues impact water use of forested catchments is crucial for accurate calculation of water balance and effective catchment management in terrestrial ecosystems. We characterised structural and physiological properties of leaves and canopies of Eucalyptus delegatensis, E. pauciflora and E. radiata, the most common species in high-country catchments in temperate Australia. These properties were related to whole-tree water transport to assess differences in water use strategies among the three species. Stomatal conductance, instantaneous transpiration efficiency, stomatal occlusion (through cuticular ledges) and leaf area index differed significantly among species. Whole-tree water use of all species was strongly coupled to changes in vapour pressure deficit (VPD) and photosynthetically active radiation (Q), yet stomatal closure reduced water transport at VPD > 1 kPa in all species, even when soil water was not limiting. The observed differences in leaf traits and related water use strategies reflect species-specific adaptations to dominant environmental conditions within the landscape matrix of catchments. The generalist E. radiata seems to follow an opportunistic, while the two more spatially restricted species have adopted a pessimistic water use strategy. Catchment-scale models of carbon and water fluxes will need to reflect such variation in structure and function, if they are to fully capture species effects on water balance and yield.

  12. GID1 modulates stomatal response and submergence tolerance involving abscisic acid and gibberellic acid signaling in rice.

    PubMed

    Du, Hao; Chang, Yu; Huang, Fei; Xiong, Lizhong

    2015-11-01

    Plant responses to abiotic stresses are coordinated by arrays of growth and developmental programs. Gibberellic acid (GA) and abscisic acid (ABA) play critical roles in the developmental programs and environmental responses, respectively, through complex signaling and metabolism networks. However, crosstalk between the two phytohormones in stress responses remains largely unknown. In this study, we report that GIBBERELLIN-INSENSITIVE DWARF 1 (GID1), a soluble receptor for GA, regulates stomatal development and patterning in rice (Oryza sativa L.). The gid1 mutant showed impaired biosynthesis of endogenous ABA under drought stress conditions, but it exhibited enhanced sensitivity to exogenous ABA. Scanning electron microscope and infrared thermal image analysis indicated an increase in the stomatal conductance in the gid1 mutant under drought conditions. Interestingly, the gid1 mutant had increased levels of chlorophyll and carbohydrates under submergence conditions, and showed enhanced reactive oxygen species (ROS)-scavenging ability and submergence tolerance compared with the wild-type. Further analyses suggested that the function of GID1 in submergence responses is partially dependent on ABA, and GA signaling by GID1 is involved in submergence tolerance by modulating carbohydrate consumption. Taken together, these findings suggest GID1 plays distinct roles in stomatal response and submergence tolerance through both the ABA and GA signaling pathways in rice.

  13. Nighttime snacking reduces whole body fat oxidation and increases LDL cholesterol in healthy young women.

    PubMed

    Hibi, Masanobu; Masumoto, Ayumi; Naito, Yuri; Kiuchi, Kahori; Yoshimoto, Yayoi; Matsumoto, Mai; Katashima, Mitsuhiro; Oka, Jun; Ikemoto, Shinji

    2013-01-15

    The increase in obesity and lipid disorders in industrialized countries may be due to irregular eating patterns. Few studies have investigated the effects of nighttime snacking on energy metabolism. We examined the effects of nighttime snacking for 13 days on energy metabolism. Eleven healthy women (means ± SD; age: 23 ± 1 yr; body mass index: 20.6 ± 2.6 kg/m(2)) participated in this randomized crossover trial for a 13-day intervention period. Subjects consumed a specified snack (192.4 ± 18.3 kcal) either during the daytime (10:00) or the night time (23:00) for 13 days. On day 14, energy metabolism was measured in a respiratory chamber without snack consumption. An oral glucose tolerance test was performed on day 15. Relative to daytime snacking, nighttime snacking significantly decreased fat oxidation (daytime snacking: 52.0 ± 13.6 g/day; nighttime snacking: 45.8 ± 14.0 g/day; P = 0.02) and tended to increase the respiratory quotient (daytime snacking: 0.878 ± 0.022; nighttime snacking: 0.888 ± 0.021; P = 0.09). The frequency of snack intake and energy intake, body weight, and energy expenditure were not affected. Total and low-density lipoprotein (LDL) cholesterol significantly increased after nighttime snacking (152 ± 26 mg/dl and 161 ± 29 mg/dl; P = 0.03 and 76 ± 20 mg/dl and 83 ± 24 mg/dl; P = 0.01, respectively), but glucose and insulin levels after the glucose load were not affected. Nighttime snacking increased total and LDL cholesterol and reduced fat oxidation, suggesting that eating at night changes fat metabolism and increases the risk of obesity.

  14. Glutamate functions in stomatal closure in Arabidopsis and fava bean.

    PubMed

    Yoshida, Riichiro; Mori, Izumi C; Kamizono, Nobuto; Shichiri, Yudai; Shimatani, Tetsuo; Miyata, Fumika; Honda, Kenji; Iwai, Sumio

    2016-01-01

    Guard cells are indispensable for higher plants because they control gas exchange and water balance to maintain photosynthetic activity. The signaling processes that govern their movement are controlled by several factors, such as abscisic acid (ABA), blue light, pathogen-associated molecular patterns (PAMPs), and carbon dioxide. Herein, we demonstrated that the amino acid glutamate (Glu), a well-known mammalian neurotransmitter, functions as a novel signaling molecule in stomatal closure in both Arabidopsis and fava bean (Vicia faba L.). Pharmacological and electrophysiological analyses provided important clues for the participation of Glu-receptors, Ca(2+), and protein phosphorylation during the signaling process. Genetic analyses using Arabidopsis ABA-deficient (aba2-1) and ABA-insensitive (abi1-1 and abi2-1) mutants showed that ABA is not required for Glu signaling. However, loss-of-function of the Arabidopsis gene encoding Slow Anion Channel-Associated 1 (SLAC1) and Calcium-Dependent Protein Kinase 6 (CPK6) impaired the Glu response. Moreover, T-DNA knockout mutations of the Arabidopsis Glu receptor-like gene (GLR), GLR3.5, lost their sensitivity to Glu-dependent stomatal closure. Our results strongly support functional Glu-signaling in stomatal closure and the crucial roles of GLRs in this signaling process.

  15. Characterization of acquired denture pellicle from healthy and stomatitis patients.

    PubMed

    Edgerton, M; Levine, M J

    1992-10-01

    Little information is available about the acquired pellicle layer that is formed on denture surfaces or its role in regulating microbial colonization of the prosthetic surface. Because denture-induced stomatitis is associated with increased numbers of Candida albicans and other microorganisms on the denture surface, the acquired denture pellicle (ADP) may play a role in modulating this colonization. This study examined and compared ADP from healthy patients and patients with stomatitis by chemical and immunochemical methods. The ADP was found to be composed of a selectively adsorbed layer containing salivary amylase, high molecular weight mucin (MG1), lysozyme, albumin, and sIgA. Salivary cystatins, proline-rich proteins, and low molecular weight mucin (MG2) were not detected. ADP amino acid composition was distinct from any of the ductal salivas, but had many similarities with enamel pellicle. Immunoblots of ADP from patients with stomatitis identified additional serum components, degradation products, and C. albicans cell components that were not detected in ADP from healthy patients. Quantification of these molecules in ADP could lead to a diagnostic test for oral mucosal disease underlying a denture base. Identification of specific molecules in denture pellicle that promote adhesion of C. albicans may elucidate a mechanism of fungal cell colonization on the denture surface. Future studies that chemically modify the denture acrylic resin surface to immobilize antimicrobial proteins may be a means of decreasing pathogenic plaque development.

  16. Glutamate functions in stomatal closure in Arabidopsis and fava bean.

    PubMed

    Yoshida, Riichiro; Mori, Izumi C; Kamizono, Nobuto; Shichiri, Yudai; Shimatani, Tetsuo; Miyata, Fumika; Honda, Kenji; Iwai, Sumio

    2016-01-01

    Guard cells are indispensable for higher plants because they control gas exchange and water balance to maintain photosynthetic activity. The signaling processes that govern their movement are controlled by several factors, such as abscisic acid (ABA), blue light, pathogen-associated molecular patterns (PAMPs), and carbon dioxide. Herein, we demonstrated that the amino acid glutamate (Glu), a well-known mammalian neurotransmitter, functions as a novel signaling molecule in stomatal closure in both Arabidopsis and fava bean (Vicia faba L.). Pharmacological and electrophysiological analyses provided important clues for the participation of Glu-receptors, Ca(2+), and protein phosphorylation during the signaling process. Genetic analyses using Arabidopsis ABA-deficient (aba2-1) and ABA-insensitive (abi1-1 and abi2-1) mutants showed that ABA is not required for Glu signaling. However, loss-of-function of the Arabidopsis gene encoding Slow Anion Channel-Associated 1 (SLAC1) and Calcium-Dependent Protein Kinase 6 (CPK6) impaired the Glu response. Moreover, T-DNA knockout mutations of the Arabidopsis Glu receptor-like gene (GLR), GLR3.5, lost their sensitivity to Glu-dependent stomatal closure. Our results strongly support functional Glu-signaling in stomatal closure and the crucial roles of GLRs in this signaling process. PMID:26586261

  17. Physiology and Regulation of Calcium Channels in Stomatal Guard Cells

    SciTech Connect

    Schroeder, Julian I.

    2007-05-02

    Stomatal pores in the epidermis of leaves regulate the diffusion of CO2 into leaves for photosynthetic carbon fixation and control water loss of plants during drought periods. Guard cells sense CO2, water status, light and other environmental conditions to regulate stomatal apertures for optimization of CO2 intake and plant growth under drought stress. The cytosolic second messenger calcium contributes to stomatal movements by transducing signals and regulating ion channels in guard cells. Studies suggest that both plasma membrane Ca2+ influx channels and vacuolar/organellar Ca2+ release channels contribute to ABA-induced Ca2+ elevations in guard cells. Recent research in the P.I.'s laboratory has led to identification of a novel major cation-selective Ca2+-permeable influx channel (Ica) in the plasma membrane of Arabidopsis guard cells. These advances will allow detailed characterization of Ica plasma membrane Ca2+ influx channels in guard cells. The long term goal of this research project is to gain a first detailed characterization of these novel plasma membrane Ca2+-permeable channel currents in Arabidopsis guard cells. The proposed research will investigate the hypothesis that Ica represents an important Ca2+ influx pathway for ABA and CO2 signal transduction in Arabidopsis guard cells. These studies will lead to elucidation of key signal transduction mechanisms by which plants balance CO2 influx into leaves and transpirational water loss and may contribute to future strategies for manipulating gas exchange for improved growth of crop plants and for biomass production.

  18. Environmental adaptation in stomatal size independent of the effects of genome size

    PubMed Central

    Jordan, Gregory J; Carpenter, Raymond J; Koutoulis, Anthony; Price, Aina; Brodribb, Timothy J

    2015-01-01

    Cell sizes are linked across multiple tissues, including stomata, and this variation is closely correlated with genome size. These associations raise the question of whether generic changes in cell size cause suboptimal changes in stomata, requiring subsequent evolution under selection for stomatal size. We tested the relationships among guard cell length, genome size and vegetation type using phylogenetically independent analyses on 67 species of the ecologically and structurally diverse family, Proteaceae. We also compared how genome and stomatal sizes varied at ancient (among genera) and more recent (within genus) levels. The observed 60-fold range in genome size in Proteaceae largely reflected the mean chromosome size. Compared with variation among genera, genome size varied much less within genera (< 6% of total variance) than stomatal size, implying evolution in stomatal size subsequent to changes in genome size. Open vegetation and closed forest had significantly different relationships between stomatal and genome sizes. Ancient changes in genome size clearly influenced stomatal size in Proteaceae, but adaptation to habitat strongly modified the genome–stomatal size relationship. Direct adaptation to the environment in stomatal size argues that new proxies for past concentrations of atmospheric CO2 that incorporate stomatal size are superior to older models based solely on stomatal frequency. PMID:25266914

  19. Tulip-poplar leaf diffusion resistance calculated from stomatal dimensions and varying environmental parameters

    SciTech Connect

    McConathy, R.K.

    1983-03-01

    The study describes the gradients of stomatal size and density in the crown of a mature forest-grown tulip-poplar (Liriodendron tulipifera L.) in eastern Tennessee. These data are used to predict leaf resistance to vapor diffusion in relation to stomatal width and boundary layer resistance. Stomatal density on individual leaves did not vary, but density increased with increasing crown height. Stomatal size decreased with increasing height of leaves within the crown. Stomatal size and density variations interacted to result in a constant number of stomata per leaf at all crown heights. Stomatal diffusive resistance values calculated from stomatal measurements and varying environmental parameters indicated that stomatal resistance controlled transpiration water losses only at small apertures (<0.6 ..mu..m). Boundary layer resistance was controlling at large stomatal apertures (>0.6 ..mu..m) and at low wind speeds (approx.100 cm/s). Under normal forest conditions tulip-poplar stomatal resistance exercised more control over transpiration than did boundary layer resistance.

  20. Stomatal guard cells co-opted an ancient ABA-dependent desiccation survival system to regulate stomatal closure.

    PubMed

    Lind, Christof; Dreyer, Ingo; López-Sanjurjo, Enrique J; von Meyer, Katharina; Ishizaki, Kimitsune; Kohchi, Takayuki; Lang, Daniel; Zhao, Yang; Kreuzer, Ines; Al-Rasheid, Khaled A S; Ronne, Hans; Reski, Ralf; Zhu, Jian-Kang; Geiger, Dietmar; Hedrich, Rainer

    2015-03-30

    During the transition from water to land, plants had to cope with the loss of water through transpiration, the inevitable result of photosynthetic CO2 fixation on land [1, 2]. Control of transpiration became possible through the development of a new cell type: guard cells, which form stomata. In vascular plants, stomatal regulation is mediated by the stress hormone ABA, which triggers the opening of the SnR kinase OST1-activated anion channel SLAC1 [3, 4]. To understand the evolution of this regulatory circuit, we cloned both ABA-signaling elements, SLAC1 and OST1, from a charophyte alga, a liverwort, and a moss, and functionally analyzed the channel-kinase interactions. We were able to show that the emergence of stomata in the last common ancestor of mosses and vascular plants coincided with the origin of SLAC1-type channels capable of using the ancient ABA drought signaling kinase OST1 for regulation of stomatal closure. PMID:25802151

  1. Stomatal guard cells co-opted an ancient ABA-dependent desiccation survival system to regulate stomatal closure.

    PubMed

    Lind, Christof; Dreyer, Ingo; López-Sanjurjo, Enrique J; von Meyer, Katharina; Ishizaki, Kimitsune; Kohchi, Takayuki; Lang, Daniel; Zhao, Yang; Kreuzer, Ines; Al-Rasheid, Khaled A S; Ronne, Hans; Reski, Ralf; Zhu, Jian-Kang; Geiger, Dietmar; Hedrich, Rainer

    2015-03-30

    During the transition from water to land, plants had to cope with the loss of water through transpiration, the inevitable result of photosynthetic CO2 fixation on land [1, 2]. Control of transpiration became possible through the development of a new cell type: guard cells, which form stomata. In vascular plants, stomatal regulation is mediated by the stress hormone ABA, which triggers the opening of the SnR kinase OST1-activated anion channel SLAC1 [3, 4]. To understand the evolution of this regulatory circuit, we cloned both ABA-signaling elements, SLAC1 and OST1, from a charophyte alga, a liverwort, and a moss, and functionally analyzed the channel-kinase interactions. We were able to show that the emergence of stomata in the last common ancestor of mosses and vascular plants coincided with the origin of SLAC1-type channels capable of using the ancient ABA drought signaling kinase OST1 for regulation of stomatal closure.

  2. Moderate water stress causes different stomatal and non-stomatal changes in the photosynthetic functioning of Phaseolus vulgaris L. genotypes.

    PubMed

    Ramalho, J C; Zlatev, Z S; Leitão, A E; Pais, I P; Fortunato, A S; Lidon, F C

    2014-01-01

    The impact of moderate water deficit on the photosynthetic apparatus of three Phaseolus vulgaris L. cultivars, Plovdiv 10 (P10), Dobrudjanski Ran (DR) and Prelom (Prel), was investigated. Water shortage had less impact on leaf hydration, RWC (predawn and midday) and predawn water potential in Prel. RWC and Ψ(p) were more reduced in P10, while there was no osmotic adjustment in any cultivar. Although drought drastically reduced stomatal opening in P10 and DR, reduced A(max) indicated non-stomatal limitations that contributed to the negligible P(n). These limitations were on potential thylakoid electron transport rates of PSI and II, pointing to photosystem functioning as a major limiting step in photosynthesis. This agrees with decreases in actual photochemical efficiency of PSII (F(v)'/F(m)'), quantum yield of photosynthetic non-cyclic electron transport (ϕ(e)) and energy-driven photochemical events (q(P)), although the impact on these parameters would also include down-regulation processes. When compared to DR, Prel retained a higher functional state of the photosynthetic machinery, justifying reduced need for photoprotective mechanisms (non-photochemical quenching, zeaxanthin, lutein, β-carotene) and maintenance of the balance between energy capture and dissipative pigments. The highest increases in fructose, glucose, arabinose and sorbitol in Prel might be related to tolerance to a lower oxidative state. All cultivars had reduced A(max) due to daytime stomatal closure in well-watered conditions. Under moderate drought, Prel had highest tolerance, higher leaf hydration and maintenance of important photochemical use of energy. However, water shortage caused appreciable non-stomatal limitations to photosynthesis linked to regulation/imbalance at the metabolic level (and growth) in all cultivars. This included damage, as reflected in decreased potential photosystem functioning, pointing to higher sensitivity of photosynthesis to drought than is commonly assumed.

  3. Night-Time Noise Index Based on the Integration of Awakening Potential.

    PubMed

    Tagusari, Junta; Takashima, Tomoya; Furukawa, Satoshi; Matsui, Toshihito

    2016-03-01

    Sleep disturbance induced by night-time noise is a serious environmental problem that can cause adverse health effects, such as hypertension and ischemic heart disease. Night-time noise indices are used to facilitate the enforcement of permitted noise levels during night-time. However, existing night-time noise indices, such as sound exposure level (SEL), maximum sound level (LA max) and night equivalent level (L night) are selected mainly because of practical reasons. Therefore, this study proposes a noise index based on neurophysiological determinants of the awakening process. These determinants have revealed that the potential on awakening is likely integrated into the brainstem that dominates wakefulness and sleep. From this evidence, a night-time noise index, N awake,year, was redefined based on the integration of the awakening potential unit (p unit) estimated from the existing dose-response relationships of awakening. The newly-defined index considers the total number of awakenings and covers a wide-range and number of noise events. We also presented examples of its applicability to traffic noise. Although further studies are needed, it may reveal a reasonable dose-response relationship between sleep disturbance and adverse health effects and provide a consistent explanation for the risks of different sound sources where the characteristics of noise exposure are quite different. PMID:26938546

  4. Night-Time Noise Index Based on the Integration of Awakening Potential.

    PubMed

    Tagusari, Junta; Takashima, Tomoya; Furukawa, Satoshi; Matsui, Toshihito

    2016-03-01

    Sleep disturbance induced by night-time noise is a serious environmental problem that can cause adverse health effects, such as hypertension and ischemic heart disease. Night-time noise indices are used to facilitate the enforcement of permitted noise levels during night-time. However, existing night-time noise indices, such as sound exposure level (SEL), maximum sound level (LA max) and night equivalent level (L night) are selected mainly because of practical reasons. Therefore, this study proposes a noise index based on neurophysiological determinants of the awakening process. These determinants have revealed that the potential on awakening is likely integrated into the brainstem that dominates wakefulness and sleep. From this evidence, a night-time noise index, N awake,year, was redefined based on the integration of the awakening potential unit (p unit) estimated from the existing dose-response relationships of awakening. The newly-defined index considers the total number of awakenings and covers a wide-range and number of noise events. We also presented examples of its applicability to traffic noise. Although further studies are needed, it may reveal a reasonable dose-response relationship between sleep disturbance and adverse health effects and provide a consistent explanation for the risks of different sound sources where the characteristics of noise exposure are quite different.

  5. Night-Time Noise Index Based on the Integration of Awakening Potential

    PubMed Central

    Tagusari, Junta; Takashima, Tomoya; Furukawa, Satoshi; Matsui, Toshihito

    2016-01-01

    Sleep disturbance induced by night-time noise is a serious environmental problem that can cause adverse health effects, such as hypertension and ischemic heart disease. Night-time noise indices are used to facilitate the enforcement of permitted noise levels during night-time. However, existing night-time noise indices, such as sound exposure level (SEL), maximum sound level (LAmax) and night equivalent level (Lnight) are selected mainly because of practical reasons. Therefore, this study proposes a noise index based on neurophysiological determinants of the awakening process. These determinants have revealed that the potential on awakening is likely integrated into the brainstem that dominates wakefulness and sleep. From this evidence, a night-time noise index, Nawake,year, was redefined based on the integration of the awakening potential unit (punit) estimated from the existing dose-response relationships of awakening. The newly-defined index considers the total number of awakenings and covers a wide-range and number of noise events. We also presented examples of its applicability to traffic noise. Although further studies are needed, it may reveal a reasonable dose-response relationship between sleep disturbance and adverse health effects and provide a consistent explanation for the risks of different sound sources where the characteristics of noise exposure are quite different. PMID:26938546

  6. Observations and Modeling of the Nighttime Electron Density Enhancement in the Mid-latitude Ionosphere

    NASA Astrophysics Data System (ADS)

    Chen, C.; Saito, A.; Lin, C.; Huba, J. D.; Liu, J. G.

    2010-12-01

    In this study, we compare the observational data from FORMOSAT-3/COSMIC and theoretical model results performed by SAMI2 (Sami2 is Another Model of the Ionosphere) for studying the longitudinal structure of the Mid-latitude Summer Nighttime Anomaly (MSNA). In order to study the occurrence of the nighttime electron density enhancement, we defined MSNA index by the ratio of the difference of the nighttime and daytime electron densities. The observational results by the FORMOSAT-3/COSMIC satellites show that there are three obvious nighttime electron density enhancement areas around South American, European, and Northeast Asian regions during local summer. The SAMI2 model can also successfully reproduce the ionospheric MSNA structure during local summer on both hemispheres, except for Northeast Asian region. This difference between observation and model simulation may be caused by the difference between the neutral wind model and the real winds. The physical mechanisms for the longitudinal structure of the MSNA are investigated in the different model conditions. Results show that the equatorward meridional neutral winds can drive the electron density up to a higher altitude along the magnetic field lines and the longer plasma production rate by solar EUV at higher latitudes in the summer time can provide the electron density source in the nighttime ionosphere. We concluded that the combination effect by the neutral wind and the plasma production rate play the important role of the MSNA longitudinal structure.

  7. Estimation of nighttime dip-equatorial E-region current density using measurements and models

    NASA Astrophysics Data System (ADS)

    Pandey, Kuldeep; Sekar, R.; Anandarao, B. G.; Gupta, S. P.; Chakrabarty, D.

    2016-08-01

    The existence of the possible ionospheric current during nighttime over low-equatorial latitudes is one of the unresolved issues in ionospheric physics and geomagnetism. A detailed investigation is carried out to estimate the same over Indian longitudes using in situ measurements from Thumba (8.5 ° N, 76.9 ° E), empirical plasma drift model (Fejer et al., 2008) and equatorial electrojet model developed by Anandarao (1976). This investigation reveals that the nighttime E-region current densities vary from ∼0.3 to ∼0.7 A/km2 during pre-midnight to early morning hours on geomagnetically quiet conditions. The nighttime current densities over the dip equator are estimated using three different methods (discussed in methodology section) and are found to be consistent with one another within the uncertainty limits. Altitude structures in the E-region current densities are also noticed which are shown to be associated with altitudinal structures in the electron densities. The horizontal component of the magnetic field induced by these nighttime ionospheric currents is estimated to vary between ∼2 and ∼6 nT during geomagnetically quiet periods. This investigation confirms the existence of nighttime ionospheric current and opens up a possibility of estimating base line value for geomagnetic field fluctuations as observed by ground-based magnetometer.

  8. Carbon dioxide and the stomatal control of water balance and photosynthesis in higher plants

    SciTech Connect

    Taiz, L.; Zeiger, E.; Mawson, B. T.; Cornish, K.; Radin, J. W.; Turcotte, E. L.; Hercovitz, S.; Tallman, G.; Karlsson, P. E.; Bogomolni, R. A.; Talbott, L. D.; Srivastava, A.

    1992-01-01

    Research continued into the investigation of the effects of carbon dioxide on stomatal control of water balance and photosynthesis in higher plants. Topics discussed this period include a method of isolating a sufficient number of guard cell chloroplasts for biochemical studies by mechanical isolation of epidermal peels; the measurement of stomatal apertures with a digital image analysis system; development of a high performance liquid chromatography method for quantification of metabolites in guard cells; and genetic control of stomatal movements in Pima cotton. (CBS)

  9. A thermodynamic geography: night-time satellite imagery as a proxy measure of emergy.

    PubMed

    Coscieme, Luca; Pulselli, Federico M; Bastianoni, Simone; Elvidge, Christopher D; Anderson, Sharolyn; Sutton, Paul C

    2014-11-01

    Night-time satellite imagery enables the measurement, visualization, and mapping of energy consumption in an area. In this paper, an index of the "sum of lights" as observed by night-time satellite imagery within national boundaries is compared with the emergy of the nations. Emergy is a measure of the solar energy equivalent used, directly or indirectly, to support the processes that characterize the economic activity in a country. Emergy has renewable and non-renewable components. Our results show that the non-renewable component of national emergy use is positively correlated with night-time satellite imagery. This relationship can be used to produce emergy density maps which enable the incorporation of spatially explicit representations of emergy in geographic information systems. The region of Abruzzo (Italy) is used to demonstrate this relationship as a spatially disaggregate case. PMID:24338007

  10. Performance analysis of a thermosyphon solar water heating system. Part 2: Nighttime performance

    SciTech Connect

    Ghoneim, Z.A.; Nassr, I.S.

    1995-11-01

    The paper presents an experimental and theoretical analysis of the performance of a thermosyphon solar water heating system under actual operating conditions during nighttime. The system consisted of a 1.8 m by 0.8 m flat plate collector and a 100 liter tank. Detailed temperature-time curves for the system over a 24 hour period were recorded using a stand alone microprocessor-based measurement and control system. Nighttime mass flow rates were calculated using several methods, based on the recorded temperature-time curves, the governing conservation equations and the system thermal losses. Deduced nighttime mass flow rates are in the order of 0.005 kg/sec. The effect of reverse flow was found to increase the system thermal losses by nearly fourfold.

  11. Functional Analysis of Cellulose and Xyloglucan in the Walls of Stomatal Guard Cells of Arabidopsis.

    PubMed

    Rui, Yue; Anderson, Charles T

    2016-03-01

    Stomatal guard cells are pairs of specialized epidermal cells that control water and CO2 exchange between the plant and the environment. To fulfill the functions of stomatal opening and closure that are driven by changes in turgor pressure, guard cell walls must be both strong and flexible, but how the structure and dynamics of guard cell walls enable stomatal function remains poorly understood. To address this question, we applied cell biological and genetic analyses to investigate guard cell walls and their relationship to stomatal function in Arabidopsis (Arabidopsis thaliana). Using live-cell spinning disk confocal microscopy, we measured the motility of cellulose synthase (CESA)-containing complexes labeled by green fluorescent protein (GFP)-CESA3 and observed a reduced proportion of GFP-CESA3 particles colocalizing with microtubules upon stomatal closure. Imaging cellulose organization in guard cells revealed a relatively uniform distribution of cellulose in the open state and a more fibrillar pattern in the closed state, indicating that cellulose microfibrils undergo dynamic reorganization during stomatal movements. In cesa3(je5) mutants defective in cellulose synthesis and xxt1 xxt2 mutants lacking the hemicellulose xyloglucan, stomatal apertures, changes in guard cell length, and cellulose reorganization were aberrant during fusicoccin-induced stomatal opening or abscisic acid-induced stomatal closure, indicating that sufficient cellulose and xyloglucan are required for normal guard cell dynamics. Together, these results provide new insights into how guard cell walls allow stomata to function as responsive mediators of gas exchange at the plant surface. PMID:26729799

  12. Stomatal Blue Light Response Is Present in Early Vascular Plants1[OPEN

    PubMed Central

    Doi, Michio; Kitagawa, Yuki; Shimazaki, Ken-ichiro

    2015-01-01

    Light is a major environmental factor required for stomatal opening. Blue light (BL) induces stomatal opening in higher plants as a signal under the photosynthetic active radiation. The stomatal BL response is not present in the fern species of Polypodiopsida. The acquisition of a stomatal BL response might provide competitive advantages in both the uptake of CO2 and prevention of water loss with the ability to rapidly open and close stomata. We surveyed the stomatal opening in response to strong red light (RL) and weak BL under the RL with gas exchange technique in a diverse selection of plant species from euphyllophytes, including spermatophytes and monilophytes, to lycophytes. We showed the presence of RL-induced stomatal opening in most of these species and found that the BL responses operated in all euphyllophytes except Polypodiopsida. We also confirmed that the stomatal opening in lycophytes, the early vascular plants, is driven by plasma membrane proton-translocating adenosine triphosphatase and K+ accumulation in guard cells, which is the same mechanism operating in stomata of angiosperms. These results suggest that the early vascular plants respond to both RL and BL and actively regulate stomatal aperture. We also found three plant species that absolutely require BL for both stomatal opening and photosynthetic CO2 fixation, including a gymnosperm, C. revoluta, and the ferns Equisetum hyemale and Psilotum nudum. PMID:26307440

  13. Functional Analysis of Cellulose and Xyloglucan in the Walls of Stomatal Guard Cells of Arabidopsis.

    PubMed

    Rui, Yue; Anderson, Charles T

    2016-03-01

    Stomatal guard cells are pairs of specialized epidermal cells that control water and CO2 exchange between the plant and the environment. To fulfill the functions of stomatal opening and closure that are driven by changes in turgor pressure, guard cell walls must be both strong and flexible, but how the structure and dynamics of guard cell walls enable stomatal function remains poorly understood. To address this question, we applied cell biological and genetic analyses to investigate guard cell walls and their relationship to stomatal function in Arabidopsis (Arabidopsis thaliana). Using live-cell spinning disk confocal microscopy, we measured the motility of cellulose synthase (CESA)-containing complexes labeled by green fluorescent protein (GFP)-CESA3 and observed a reduced proportion of GFP-CESA3 particles colocalizing with microtubules upon stomatal closure. Imaging cellulose organization in guard cells revealed a relatively uniform distribution of cellulose in the open state and a more fibrillar pattern in the closed state, indicating that cellulose microfibrils undergo dynamic reorganization during stomatal movements. In cesa3(je5) mutants defective in cellulose synthesis and xxt1 xxt2 mutants lacking the hemicellulose xyloglucan, stomatal apertures, changes in guard cell length, and cellulose reorganization were aberrant during fusicoccin-induced stomatal opening or abscisic acid-induced stomatal closure, indicating that sufficient cellulose and xyloglucan are required for normal guard cell dynamics. Together, these results provide new insights into how guard cell walls allow stomata to function as responsive mediators of gas exchange at the plant surface.

  14. Observational Evidence for Involvement of Nitrate Radicals in Nighttime Oxidation of Mercury.

    PubMed

    Peleg, Mordechai; Tas, Eran; Obrist, Daniel; Matveev, Valeri; Moore, Christopher; Gabay, Maor; Luria, Menachem

    2015-12-15

    In the atmosphere, reactive forms of mercury species can be produced by oxidation of the dominant gaseous elemental mercury (GEM). The oxidation of GEM is an important driver for deposition, but oxidation pathways currently are poorly constrained and likely differ among regions. In this study, continuous measurements of atmospheric nitrate radical (NO3) concentrations and mercury speciation (i.e., elemental and reactive, oxidized forms) were performed during a six week period in the urban air shed of Jerusalem, Israel during summer 2012, to investigate the potential nighttime contribution of nitrate radicals to oxidized mercury formation. Average nighttime concentrations of reactive gaseous mercury (RGM) were almost equivalent to daytime levels (25 pg m(-3) and 27 pg m(-3) respectively), in contrast to early morning and evening RGM levels which dropped to low levels (9 and 13 pg m(-3)). During daytime, the presence of RGM was increased when solar radiation exceeded 200 W m(-2), suggesting a photochemical process for daytime RGM formation. Ozone concentrations were largely unrelated to daytime RGM. Nighttime RGM concentrations were relatively high (with a maximum of 97 pg m(-3)) compared to nighttime levels in other urban regions. A strong correlation was observed between nighttime RGM concentrations and nitrate radical concentration (R(2) averaging 0.47), while correlations to other variables were weak (e.g., RH; R(2) = 0.35) or absent (e.g., ozone, wind speed and direction, pollution tracers such as CO or SO2). Detailed analyses suggest that advection processes or tropospheric influences were unlikely to explain the strong nighttime correlations between NO3 and RGM, although these processes may contribute to these relationships. Our observations suggest that NO3 radicals may play a role in RGM formation, possibly due to a direct chemical involvement in GEM oxidation. Since physical data, however, suggest that NO3 unlikely initiates GEM oxidation, NO3 may play a

  15. Modelling the Effect of Fruit Growth on Surface Conductance to Water Vapour Diffusion

    PubMed Central

    GIBERT, CAROLINE; LESCOURRET, FRANÇOISE; GÉNARD, MICHEL; VERCAMBRE, GILLES; PÉREZ PASTOR, ALEJANDRO

    2005-01-01

    • Background and Aims A model of fruit surface conductance to water vapour diffusion driven by fruit growth is proposed. It computes the total fruit conductance by integrating each of its components: stomata, cuticle and cracks. • Methods The stomatal conductance is computed from the stomatal density per fruit and the specific stomatal conductance. The cuticular component is equal to the proportion of cuticle per fruit multiplied by its specific conductance. Cracks are assumed to be generated when pulp expansion rate exceeds cuticle expansion rate. A constant percentage of cracks is assumed to heal each day. The proportion of cracks to total fruit surface area multiplied by the specific crack conductance accounts for the crack component. The model was applied to peach fruit (Prunus persica) and its parameters were estimated from field experiments with various crop load and irrigation regimes. • Key Results The predictions were in good agreement with the experimental measurements and for the different conditions (irrigation and crop load). Total fruit surface conductance decreased during early growth as stomatal density, and hence the contribution of the stomatal conductance, decreased from 80 to 20 % with fruit expansion. Cracks were generated for fruits exhibiting high growth rates during late growth and the crack component could account for up to 60 % of the total conductance during the rapid fruit growth. The cuticular contribution was slightly variable (around 20 %). Sensitivity analysis revealed that simulated conductance was highly affected by stomatal parameters during the early period of growth and by both crack and stomatal parameters during the late period. Large fruit growth rate leads to earlier and greater increase of conductance due to higher crack occurrence. Conversely, low fruit growth rate accounts for a delayed and lower increase of conductance. • Conclusions By predicting crack occurrence during fruit growth, this model could be helpful

  16. Guard cell-specific upregulation of sucrose synthase 3 reveals that the role of sucrose in stomatal function is primarily energetic.

    PubMed

    Daloso, Danilo M; Williams, Thomas C R; Antunes, Werner C; Pinheiro, Daniela P; Müller, Caroline; Loureiro, Marcelo E; Fernie, Alisdair R

    2016-03-01

    Isoform 3 of sucrose synthase (SUS3) is highly expressed in guard cells; however, the precise function of SUS3 in this cell type remains to be elucidated. Here, we characterized transgenic Nicotiana tabacum plants overexpressing SUS3 under the control of the stomatal-specific KST1 promoter, and investigated the changes in guard cell metabolism during the dark to light transition. Guard cell-specific SUS3 overexpression led to increased SUS activity, stomatal aperture, stomatal conductance, transpiration rate, net photosynthetic rate and growth. Although only minor changes were observed in the metabolite profile in whole leaves, an increased fructose level and decreased organic acid levels and sucrose to fructose ratio were observed in guard cells of transgenic lines. Furthermore, guard cell sucrose content was lower during light-induced stomatal opening. In a complementary approach, we incubated guard cell-enriched epidermal fragments in (13) C-NaHCO3 and followed the redistribution of label during dark to light transitions; this revealed increased labeling in metabolites of, or associated with, the tricarboxylic acid cycle. The results suggest that sucrose breakdown is a mechanism to provide substrate for the provision of organic acids for respiration, and imply that manipulation of guard cell metabolism may represent an effective strategy for plant growth improvement. PMID:26467445

  17. Guard cell-specific upregulation of sucrose synthase 3 reveals that the role of sucrose in stomatal function is primarily energetic.

    PubMed

    Daloso, Danilo M; Williams, Thomas C R; Antunes, Werner C; Pinheiro, Daniela P; Müller, Caroline; Loureiro, Marcelo E; Fernie, Alisdair R

    2016-03-01

    Isoform 3 of sucrose synthase (SUS3) is highly expressed in guard cells; however, the precise function of SUS3 in this cell type remains to be elucidated. Here, we characterized transgenic Nicotiana tabacum plants overexpressing SUS3 under the control of the stomatal-specific KST1 promoter, and investigated the changes in guard cell metabolism during the dark to light transition. Guard cell-specific SUS3 overexpression led to increased SUS activity, stomatal aperture, stomatal conductance, transpiration rate, net photosynthetic rate and growth. Although only minor changes were observed in the metabolite profile in whole leaves, an increased fructose level and decreased organic acid levels and sucrose to fructose ratio were observed in guard cells of transgenic lines. Furthermore, guard cell sucrose content was lower during light-induced stomatal opening. In a complementary approach, we incubated guard cell-enriched epidermal fragments in (13) C-NaHCO3 and followed the redistribution of label during dark to light transitions; this revealed increased labeling in metabolites of, or associated with, the tricarboxylic acid cycle. The results suggest that sucrose breakdown is a mechanism to provide substrate for the provision of organic acids for respiration, and imply that manipulation of guard cell metabolism may represent an effective strategy for plant growth improvement.

  18. 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.

  19. A study of oxygen 6300 Å airglow production through chemical modification of the nighttime ionosphere

    NASA Astrophysics Data System (ADS)

    Semeter, Joshua; Mendillo, Michael; Baumgardner, Jeffrey; Holt, John; Hunton, Donald E.; Eccles, Vincent

    1996-09-01

    The Release Experiments to Derive Airglow Inducing Reactions (RED AIR) conducted on April 3, 1989, and December 6, 1991, offer a unique set of observations for studying the specific processes associated with the production of the O(3P--1D) emission at 6300 Å. In these experiments, sounding rockets were used to place equal quantities of CO2 above and below hmax of the nocturnal F region. CO2 leads to 6300 Å emission by a three-step process: (1) CO2+O+->O2++CO, (2) O2++e-->O*+O, (3)O*->O+hν6300. Direct measurements of plasma parameters and indirect measurements of the neutral atmosphere densities were used in conjunction with the Fluid Element Simulation (FES) computer code to model the temporal and spatial evolution of the observed 6300 Å airglow enhancement and accompanying plasma depletion. Using the currently accepted set of reaction rates relevant to F region chemistry, the quantum yield of O(1D) from reaction (2) was found to have a mild altitude dependence, decreasing by 16% from 275 to 350 km. Since the initial vibrational distribution of the nascent O2+ was the same for the two releases, this result implies an altitude dependence in the quenching of O2+ vibrational states. Building on previous evidence that O2+ is vibrationally excited in the nighttime thermosphere, we further conclude that this vibrational distribution is altitude dependent. In terms of 6300 Å airglow production, the effect is manifested in an altitude dependence of f(1D). Additionally, quenching by O(3P) was found to contribute very little to the depopulation of the nascent O(1D), with Q0=0 giving the best fit to the RED AIR observations.

  20. Modeling the Arecibo nighttime F{sub 2} layer 2. Ionospheric gradients

    SciTech Connect

    Melendez-Alvira, D.J.; Burnside, R.G.; Walker, J.C.G.

    1994-12-01

    The servo model is extended and used to fit horizontal gradients in the F{sub 2} layer height and density and to estimate the zonal Pedersen current and its zonal and meridional gradient. Horizontal gradients were measured from the Arecibo Observatory during the following five nights: August 16-17 and 17-18, 1982; and October 4-5, 5-6, and 9-10, 1983. The model gradients are driven by nonzero current gradients, which are applied as needed to fit the m