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Toby N. Carlson - One of the best experts on this subject based on the ideXlab platform.

Urs Schmidhalter - One of the best experts on this subject based on the ideXlab platform.

  • Can changes in Leaf Water Potential be assessed spectrally
    Functional plant biology : FPB, 2011
    Co-Authors: Salah Elsayed, Bodo Mistele, Urs Schmidhalter
    Abstract:

    Leaf Water Potential (LWP) is an important indicator of plant Water status. However, its determination via classicalpressure-chambermeasurementsistediousandtime-consuming.Moreover,suchmethodscannoteasilyaccountfor rapidchangesinthisparameterarisingfromchangesinenvironmentalconditions.Spectrometricmeasurements,bycontrast, have the Potential for fast and non-destructive measurements of plant Water status, but are not unproblematic. Spectral characteristics of plants vary across plant development stages and are also influenced by environmental factors. Thus, it remains unclear whether changes in Leaf Water Potential per se can reliably be detected spectrometrically or whether such measurements also reflectautocorrelated changesintheLeafWater content(LWC) ortheaerial plant biomass.Wetested the accuracy of spectrometric measurements in this context under controlled climate chamber conditions in series of six experiments that minimised perturbing influences but allowed for significant changes in the LWP. Short-term exposure of dense stands of plants to increasing or decreasing artificial light intensities in a growth chamber more markedly decreased LWP than LWC in both wheat and maize. Significant relationships (R 2 -values 0.74-0.92) between LWP and new spectral indices ((R940/R960)/NDVI; R940/R960) were detected with or without significant changes in LWC of both crop species. The exact relationships found, however, were influenced strongly by the date of measurement or Water stress induced. Thus, global spectral relationships measuring LWP probably cannot be established across plant development stages. Evenso,spectrometricmeasurements supplementedbyareducedcalibrationdatasetfrompressurechamber measurements might still prove to be a fast and accurate method for screening large numbers of diverse lines.

Irwin N Forseth - One of the best experts on this subject based on the ideXlab platform.

  • responses of gas exchange and phototropic Leaf orientation in soybean to soil Water availability Leaf Water Potential air temperature and photosynthetic photon flux
    Environmental and Experimental Botany, 1992
    Co-Authors: Irwin N Forseth
    Abstract:

    Abstract The response of rapid, tropic Leaf movement and gas exchange to long- and short-term environmental factors in potted soybean ( Glycine max cv. Cumberland) was examined. Leaf angles measured on leaves of droughted plants under a vertical illumination were steeper relative to those of well-Watered plants, resulting in a negative linear relationship between steady-state Leaf angle and Leaf Water Potential. Short-term changes in Leaf Water Potential induced by root cooling and reWatering did not affect the steady-state Leaf angle in response to vertical illumination. Though photosynthesis and stomatal conductance responded to short-term changes in Leaf Water Potential, a carryover effect of long-term Water availability on intercellular CO 2 concentration was still present. Increasing photosynthetic photon flux and air temperature increased steady-state Leaf angle at a given Leaf Water Potential. However, Leaf movements of droughted plants were more sensitive to increasing photosynthetic photon flux and air temperature relative to those of well-Watered plants. Leaves of droughted plants had a reduction in photosaturated photosynthesis and the photon flux required to saturate photosynthesis compared to leaves of well-Watered plants. The thermal optimum for photosynthesis was also shifted to a lower Leaf temperature in leaves of droughted plants. The only factors affecting rapid, reversible tropic Leaf movements over the short-term (minutes) appeared to be light and temperature, while Leaf Water Potential had its major effect over a long-term scale (days-weeks). Additionally, the response of paraheliotropic Leaf movement to short-term changes of environmental variables was complementary to responses of carbon dioxide and Water vapor gas exchange to long-term environmental factors.

Barry H. Lynn - One of the best experts on this subject based on the ideXlab platform.

Xuhui Lee - One of the best experts on this subject based on the ideXlab platform.

  • Influence of Leaf Water Potential on diurnal changes in CO 2 and Water vapour fluxes
    Boundary-Layer Meteorology, 2007
    Co-Authors: Jing Wang, Xuhui Lee
    Abstract:

    Mass and energy fluxes between the atmosphere and vegetation are driven by meteorological variables, and controlled by plant Water status, which may change more markedly diurnally than soil Water. We tested the hypothesis that integration of dynamic changes in Leaf Water Potential may improve the simulation of CO2 and Water fluxes over a wheat canopy. Simulation of Leaf Water Potential was integrated into a comprehensive model (the ChinaAgrosys) of heat, Water and CO2 fluxes and crop growth. Photosynthesis from individual leaves was integrated to the canopy by taking into consideration the attenuation of radiation when penetrating the canopy. Transpiration was calculated with the Shuttleworth-Wallace model in which canopy resistance was taken as a link between energy balance and physiological regulation. A revised version of the Ball-Woodrow-Berry stomatal model was applied to produce a new canopy resistance model, which was validated against measured CO2 and Water vapour fluxes over winter wheat fields in Yucheng (36°57′ N, 116°36′ E, 28 m above sea level) in the North China Plain during 1997, 2001 and 2004. Leaf Water Potential played an important role in causing stomatal conductance to fall at midday, which caused diurnal changes in photosynthesis and transpiration. Changes in soil Water Potential were less important. Inclusion of the dynamics of Leaf Water Potential can improve the precision of the simulation of CO2 and Water vapour fluxes, especially in the afternoon under Water stress conditions.