Simulation Model for Studying Physiological Water Stress Responses of Whole Plants

Abstract

Simulation models are useful tools for integrating ideas about physiological responses to soil water deficits at the whole plant level. This paper describes a model that mimics the behavior of plants exposed to a single cycle of water deficit under controlled environment conditions. The model uses linear functions to describe the following basic physiological responses to soil water: (i) rate of new leaf production, (ii) stomatal closure, (iii) rate of senescence as it affects stomatal conductance, photosynthetic and respiratory rates, and leaf area. Simulations with the model demonstrated how the assumption of a hyperbolic dependence of photosynthetic rate on internal CO 2 concentration could lead to an increase in water use efficiency as stomates close. The model confirmed published data showing that stomatal closure induced by salinization increases the efficiency under water stress and leads to a greater C gain per irrigation cycle. Other simulations demonstrated how an increase in the volume of soil explored by unit mass of new roots could lead to greater amounts of water uptake and C gain per cycle. Interactions among these and other factors can be studied in a way that would not otherwise be possible.