[Stomatal regulation of plants in response to drought stress]

The regulation on carbon acquisition and water loss plays a critical role in plant growth and survival. Stomata are important portals for plants to control the exchanges of carbon and water between leaves and the atmosphere. Therefore, understanding stomatal control mechanisms and modelling stomatal conductivity are indispensable to accurately simulate carbon and water cycling in terrestrial ecosystems. As global climate change is accelerating in recent years, drought events have become more and more frequent and thus profoundly affect the survival, growth and distribution of plants. In order to deeply understand the underlying mechanism of carbon-water coupling of plants and predict the dynamics of plants and communities under global changes, it is crucial to explore responses of stomatal regulation of plants to drought stress. In this review, we synthesized recent research progress on mechanisms and modeling of plant stomatal regulation under drought stress. First, this review described the active and passive regulation of plant stomatal control in response to drought stress, and discussed the evolution of plant stomatal regulation, including the passive hydraulic regulation of ferns and lycophytes, the active regulation of angiosperms, and the dual-control mechanism of gymnosperms that was proposed as an important transitional type during evolution from ferns to angiosperms. Then, we analyzed the relationship between stomatal and hydraulic regulations, and discussed the debates on the decoupling of plant water potential from stomatal conductivity. The application of stomatal-conductivity optimization models was introduced based on the water use efficiency hypothesis and the maximum carbon gain hypothesis. The model based on the latter had a greater potential of prediction and practical application. Finally, we proposed two issues that should be urgently addressed: 1) to scale up the research of plant stomatal regulation from leaf or individual to ecosystem or even larger scales so as to improve the mechanistic models of carbon and water cycling in terrestrial ecosystems; and 2) to quantify the hydroactive feedback processes of plant stomatal regulation so as to modify current hydraulics models of plant stomatal function.