Figure 1.

Overview of leaf senescence. The final stages of leaf development are basically determined by plant age and transition into the reproductive stage, but are also modulated by endogenous and exogenous cues which integrate into the developmental program. Environmental conditions affecting senescence progression include biotic and abiotic stresses and nutritional status, whereas hormones represent the most relevant endogenous factors. Many environmental stresses increase propagation of reactive oxygen species (ROS) in leaf tissue, which act as signaling molecules. SAGs, senescence-associated genes.