title: A Modeling Approach to Quantify the Effects of Stomatal Behavior and Mesophyll Conductance on Leaf Water Use Efficiency.
abstract: 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.
authors.affiliation: Vegetable Systems Modelling Section, Institute of Horticultural Production Systems, Leibniz Universität Hannover Hannover, Germany.
authors.forename: Dany P
authors.initials: DP
authors.lastname: Moualeu-Ngangue
authors.affiliation: Vegetable Systems Modelling Section, Institute of Horticultural Production Systems, Leibniz Universität HannoverHannover, Germany; UMR759 Laboratoire d'Ecophysiologie des Plantes sous Stress Environnementaux, Institut National de la Recherche AgronomiqueMontpellier, France.
authors.forename: Tsu-Wei
authors.initials: TW
authors.lastname: Chen
authors.affiliation: Vegetable Systems Modelling Section, Institute of Horticultural Production Systems, Leibniz Universität Hannover Hannover, Germany.
authors.forename: Hartmut
authors.initials: H
authors.lastname: Stützel
keywords: Light regulation; mesophyll conductance; sap flow dynamics; stomatal behavior; water use efficiency