Visualizing Interactions of Water Stress Responses with a Whole‐Plant Simulation Model

Abstract

Simulation models provide a framework for visualizing how different physiological responses may be interacting when plants respond to water stress. The model McStress was used to evaluate data for rates of whole plant gas exchange of three species that showed contrasting responses to water stress under controlled environment conditions. Inputs to the model were systematically varied until the outputs matched the data. Excellent agreement was obtained. In analyzing how the model achieved the match, it became apparent that many of the differences among species could be explained by differences in leaf conductance under well‐irrigated conditions without invoking differences in stress response. The analysis showed both the boundary layer component and the stomatal component contributing to species differences in simulated leaf conductance, sometimes in opposite directions. Analysis of water use efficiency and carbon use efficiency data pointed up complex interacting effects of accelerated senescence on rates of photosynthesis and respiration that could not be discerned in the data. The relationship between root biomass and water uptake was analyzed by introducing the idea that only fine roots are capable of taking up water. The analysis could have been made even more realistic if the model had included gradients in water potential.