Figure 1.

Schematic model for abiotic stress-triggered stomatal closure mediated by H₂O₂. The net ion release and turgor reduction lead to stomatal closing. ABA-dependent process (red arrows and clamps): Under conditions of drought or salt stress, ABA induces H₂O₂ production via the activation of plasma membrane NADPH oxidases. Then, H₂O₂ activates plasma membrane calcium channels resulting in cytosolic Ca²⁺ elevation. This cytosolic Ca²⁺ elevation activates outward Cl⁻ channels and inactivates inward K⁺ channels, causing membrane depolarization. Membrane depolarization activates outward K⁺ channels and facilitates the efflux of organic solutes. ABA-independent process (blue arrow and clamp): The expression of DST is negatively regulated by drought or salt stress. DST positively regulates the expression of H₂O₂ scavenger genes; e.g., peroxidase 24 precursor.