Stomatal signaling under drought: integrating hormonal pathways for crop resilience.

Drought is a major abiotic constraint that limits plant growth and productivity worldwide. To cope with water scarcity, plants employ complex adaptive strategies, with stomatal regulation serving as a central mechanism for balancing water conservation and photosynthetic efficiency. Phytohormones are crucial signaling mediators in this process, coordinating the molecular, physiological, and biochemical responses that govern stomatal dynamics during drought. Abscisic acid (ABA) is the principal regulator of drought-induced stomatal closure; however, other hormones, including salicylic acid, methyl jasmonates, ethylene, gibberellins, cytokinins, and auxins, modulate stomatal function through synergistic or antagonistic interactions. Such hormonal crosstalk shapes guard cell sensitivity to ABA, regulates ion channel activity, influences transcriptional networks, and ultimately determines water-use efficiency. While earlier reviews have addressed the broader roles of phytohormones in drought adaptation, they often overlook the nuanced regulation of stomatal behavior. This review uniquely synthesizes recent advances in phytohormone signaling networks, with particular emphasis on their synergistic and antagonistic crosstalk and downstream signaling cascades that govern stomatal regulation under drought stress. It further integrates current insights into hormone-mediated adaptive responses coordinated with stomatal dynamics, establishing a mechanistic framework that links molecular signaling with physiological regulation and drought tolerance. We also highlight emerging strategies to harness hormonal regulation to enhance drought resilience and outline key research priorities for translating these insights into crop improvement.