Extracellular ROS perception by HPCA1 sustains wound-induced systemic signaling and stomatal closure at the cotyledon stage in Arabidopsis

treatment. This deficiency is associated with the complete loss of local and distal stomatal closure, whereas wild-type seedlings display consistent and coordinated stomatal responses. These results indicate that extracellular ROS perception mediated by HPCA1 is essential for the transduction of systemic ROS signals into a functional physiological acclimation response at the guard-cell level. Altogether, our findings support a model in which HPCA1 acts as a key hub coupling extracellular ROS perception with signal propagation and intracellular transduction pathways, thereby sustaining wound-induced systemic signaling and coordinating stomatal acclimation in Arabidopsis seedlings.