Revealing the drought-induced variations in rice water use strategy through a hydraulic-based stomatal optimization model

Abstract

Effects of drought on rice’s water use strategies and how these variations are linked to stress-induced physiological changes are poorly understood. This study developed a stomatal optimization model and proposed a model-based analytical framework for evaluating the variations in rice water use strategies in response to drought. We applied this approach to water deficit experiments on rice, with mild, moderate, and severe water deficit treatments representing 70 %, 60 %, and 50 % of the field water capacity (FC), respectively. Water deficit co-limited the photosynthetic capacity and water transport capacity of rice, accompanied by adaptation in water use strategies. These stress-induced physiological changes enhanced the long-term hydraulic safety in some treatments, while increasing long-term carbon gain in others. Rice that suffered severe water deficit (i.e., 50 % FC) exhibited a more anisohydric water use strategy during the post-stress period. The model predicts that while anisohydric water use strategy reduces future soil water availability, larger stomatal opening compensates for the impaired photosynthesis caused by irreversible physiological damage and thus contributes to long-term carbon gains. This work emphasizes the adaptability of plant water use strategies to the environment, which has important implications for modeling and predicting water productivity and water use efficiency of crops or other ecosystems under changing environments.