Proposed cellular events and signaling cascades in a plant cell responding to
drought stress. Drought stress is perceived by an unknown mechanism, which then activates
the signaling cascades, plausibly by abscisic acid (ABA), hydrogen peroxide (H2O2) and
calcium (Ca+2). These cascades then activate the synthesis of specific protein kinases which
activate more downstream responses such as changes in gene expression. The response to
these signaling cascades also results in changes in plant metabolism including activation and
synthesis of antioxidants, synthesis and accumulation of osmo-protectants and solutes, and
stomatal closure under acute drought stress.