Counteracting excessive stomatal closure under drought: mechanisms and implications for plant growth and crop productivity

Abstract

Drought severely constrains plant photosynthesis, growth, and productivity, and can even lead to plant death. In response to water deficit, plants close their stomata, primarily through abscisic acid (ABA)-mediated signaling, thereby reducing transpirational water loss and enhancing survival, particularly under severe drought. However, excessively sensitive or complete stomatal closure severely limits CO2 assimilation, leading to substantial penalties in plant growth and crop yield, especially under mild and moderate drought stress. This creates a critical trade-off between stress resistance and carbon gain. Although extensive research has focused on the mechanisms underlying drought-induced stomatal closure, much less attention has been paid to how plants prevent excessive closure in order to sustain photosynthesis and growth during drought. In this review, we first provide a brief overview of the signaling pathways involved in drought-induced stomatal closure, with particular emphasis on the ABA pathway. We then summarize diverse mechanisms that antagonize stomatal closure under drought, including the actions of plant hormones, small molecules, transcription factors, and peptides. These mechanisms function by modulating ABA biosynthesis and signaling or by interfering with downstream effectors such as reactive oxygen species (ROS). In addition, we discuss current and potential applications of these mechanisms for improving plant growth and crop yield under drought conditions. Overall, this review provides a comprehensive framework for understanding how stomatal regulation balances stress resistance with growth, and highlights opportunities for crop improvement through the optimization of stomatal responses to drought according to drought severity and hydraulic safety margin.