Postharvest Senescence of Vegetables and its Regulation

This chapter discusses the specific patterns of senescence and its regulation in vegetables. A key feature of senescence in vegetables is the two major categories: functionally and nonfunctionally self-sufficient, with the former as a dormant phase. It is difficult to separate the wounding effect of harvesting from the deprivation of nutrients, water, and hormones, as vegetables in second category are so poorly adapted to being detached from the plant. The two key handling practices are low temperature to reduce respiration, and high humidity to reduce transpiration. There is a strong relationship between respiration rate and the rate of senescence. Senescence is strongly influenced by hormones, external stimuli, and correlative controls from other tissues in complex vegetables. The role of hormones in vegetable senescence varies depending on whether senescence or the senescence-delaying stage of dormancy is considered. Ethylene, cold storage, and wounding all perform similarly during both phases, while abscisic acid (ABA), cytokinins, GA, and auxins have opposite effects on each phase.