The Experts below are selected from a list of 54975 Experts worldwide ranked by ideXlab platform
Pol Coppin - One of the best experts on this subject based on the ideXlab platform.
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Thermal infrared imaging of the temporal variability in Stomatal Conductance for fruit trees
International Journal of Applied Earth Observation and Geoinformation, 2015Co-Authors: Raymond Ralph Struthers, Anna Ivanova, Laurent Tits, Rony Swennen, Pol CoppinAbstract:Abstract 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.
Afrasyab Rahnama - One of the best experts on this subject based on the ideXlab platform.
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Stomatal Conductance as a screen for osmotic stress tolerance in durum wheat growing in saline soil
Functional Plant Biology, 2010Co-Authors: Afrasyab Rahnama, Richard A James, K Poustini, Rana MunnsAbstract:The change in Stomatal Conductance measured soon after durum wheat (Triticum turgidum ssp. durum Desf.) was exposed to salinity was verified as an indicator of osmotic stress tolerance. It was a reliable and useful screening technique for identifying genotypic variation. The minimum NaCl treatment needed to obtain a significant Stomatal response was 50 mM, but 150 mM was needed to obtain significant differences between genotypes. The response to the NaCl was osmotic rather than Na+-specific. Stomatal Conductance responded similarly to iso-osmotic concentrations of KCl and NaCl, both in the speed and extent of closure, and in the difference between genotypes. The new reduced rate of Stomatal Conductance in response to addition of 50 mM NaCl or KCl occurred within 45 min, and was independent of the concentration of Na+ in leaves. The difference between genotypes was long-lasting, translating into differences in shoot biomass and tiller number after a month. These results indicate that the relative size of the change in Stomatal Conductance when the salinity is introduced could be a means of screening for osmotic stress tolerance in wheat and other cereals.
Steven C Wofsy - One of the best experts on this subject based on the ideXlab platform.
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dynamics of canopy Stomatal Conductance transpiration and evaporation in a temperate deciduous forest validated by carbonyl sulfide uptake
Biogeosciences, 2016Co-Authors: R Wehr, Roisin Commane, William J Munger, Barry J Mcmanus, David D Nelson, Mark S Zahniser, Scott R Saleska, Steven C WofsyAbstract:Abstract. Stomatal Conductance influences both photosynthesis and transpiration, thereby coupling the carbon and water cycles and affecting surface–atmosphere energy exchange. The environmental response of Stomatal Conductance has been measured mainly on the leaf scale, and theoretical canopy models are relied on to upscale Stomatal Conductance for application in terrestrial ecosystem models and climate prediction. Here we estimate Stomatal Conductance and associated transpiration in a temperate deciduous forest directly on the canopy scale via two independent approaches: (i) from heat and water vapor exchange and (ii) from carbonyl sulfide (OCS) uptake. We use the eddy covariance method to measure the net ecosystem–atmosphere exchange of OCS, and we use a flux-gradient approach to separate canopy OCS uptake from soil OCS uptake. We find that the seasonal and diurnal patterns of canopy Stomatal Conductance obtained by the two approaches agree (to within ±6 % diurnally), validating both methods. Canopy Stomatal Conductance increases linearly with above-canopy light intensity (in contrast to the leaf scale, where Stomatal Conductance shows declining marginal increases) and otherwise depends only on the diffuse light fraction, the canopy-average leaf-to-air water vapor gradient, and the total leaf area. Based on Stomatal Conductance, we partition evapotranspiration (ET) and find that evaporation increases from 0 to 40 % of ET as the growing season progresses, driven primarily by rising soil temperature and secondarily by rainfall. Counterintuitively, evaporation peaks at the time of year when the soil is dry and the air is moist. Our method of ET partitioning avoids concerns about mismatched scales or measurement types because both ET and transpiration are derived from eddy covariance data. Neither of the two ecosystem models tested predicts the observed dynamics of evaporation or transpiration, indicating that ET partitioning such as that provided here is needed to further model development and improve our understanding of carbon and water cycling.
Raymond Ralph Struthers - One of the best experts on this subject based on the ideXlab platform.
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Thermal infrared imaging of the temporal variability in Stomatal Conductance for fruit trees
International Journal of Applied Earth Observation and Geoinformation, 2015Co-Authors: Raymond Ralph Struthers, Anna Ivanova, Laurent Tits, Rony Swennen, Pol CoppinAbstract:Abstract 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.
William J. Davies - One of the best experts on this subject based on the ideXlab platform.
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Abscisic acid in leaves and roots of willow: significance for Stomatal Conductance.
Tree physiology, 2001Co-Authors: L. Liu, A. J. S. Mcdonald, I. Stadenberg, William J. DaviesAbstract:Excised leaves and roots of willow (Salix dasyclados Wimm.) accumulated abscisic acid (ABA) in response to desiccation. The accumulation of ABA was greater in young leaves and roots than in old leaves and roots. In mature leaves, ABA accumulation was related to the severity and duration of the desiccation treatment. Water loss equal to 12% of initial fresh weight caused the ABA content of mature leaves to increase measurably within 30 min and to double in 2.5 h. The drying treatment caused significant (P = 0.05) reductions in leaf water potential and Stomatal Conductance. Recovery of leaf water potential to the control value occurred within 10 min of rewatering the dehydrated leaves, but recovery of Stomatal Conductance took an hour or longer, depending on the interval between dehydration and rewatering. The addition of ABA to the transpiration stream of well-watered excised leaves was sufficient to cause partial Stomatal closure within 1 h and, depending on ABA concentration, more or less complete Stomatal closure within 3 h. When the ABA solution was replaced with water, Stomatal Conductance increased at a rate inversely related to the concentration of the ABA solution with which the leaves had been supplied.
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The coupled response of Stomatal Conductance to photosynthesis and transpiration
Journal of Experimental Botany, 1998Co-Authors: Andy Jarvis, William J. DaviesAbstract:Increases in the net rate of photosynthesis and Stomatal Conductance of leaves are perceived to occur simultaneously. Published data are re-analysed here to show that when increases in the net rate of photosynthesis are a result of transient increases in the ambient CO 2 concentration then the reverse is the case, i.e. increases in net photosynthesis are closely correlated to reductions in Stomatal Conductance. Rather than explain this observation in terms of a direct effect of CO 2 on stomata this article develops the idea that stomata respond to a signal in proportion to the degree to which the photosynthetic capacity is realized. This interpretation of Stomatal function facilitates the formulation of a simple static model of Stomatal responses to the rates of both carbon gain and water loss.
