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.

Why Do Large‐Scale Land Surface Models Produce a Low Ratio of Transpiration to Evapotranspiration?

“…Because of the higher light intensity level in NOSHADE, stomatal conductance is enhanced, resulting in elevated T and GPP. However, the increase in carbon assimilation cannot balance transpired water, contributing to the weakened WUE (Moualeu‐Ngangue et al, ). On the contrary, topographic shading effects in CTRL may compensate for the decreased photosynthetically active radiation level by enhancing light use efficiency, thus maintaining net carbon assimilation (Charbonnier et al, ).…”

Environmental triggers for photosynthetic protein turnover determine the optimal nitrogen distribution and partitioning in the canopy

“…The steady-state A c was solved analytically with Eqs (9b), (14), and (15), and A j with Eqs (9c), (14), and (15), following Moualeu‐Ngangue et al (2016). Model variables and coefficients are listed in Tables 1–3.…”

Determining Ion Toxicity in Cucumber under Salinity Stress

“…Ion accumulation and ion transport are complex processes associated with a variety of physiological phenomena, such as transpiration, the ability to avoid/enhance ion entering the shoots [42,[45][46][47]51], preferential accumulation of Na + in supporting tissues or in the vacuole [44,49,52], and recirculation of ions from the shoot to the roots via the phloem [7,8,25]. Results from the grafting experiment do not support the hypothesis that grafting onto pumpkin rootstock enhances Na + recirculation in the cucumber scion, but surprisingly, grafting onto pumpkin facilitates K + transport towards the young leaves and enhances Cl − recirculation from the young to the old leaves (Table 4).…”

“…To have an overall picture how a specific ion is accumulated and transported on the plant level requires the understanding of a complex system [45,51]. A series of modeling studies following the approach proposed by Wolf and Jeschke (1987) investigating ion distribution under salinity can be found in the literature [24,25,[54][55][56].…”