Senescence: Regulation and signalling

Abstract

Senescence is a multifaceted, genetically regulated programme, in which cascade of physiological and biochemical changes occur which bring about the deprivation of macromolecules and the recycling of their components to different parts of the plant. Senescence culminates in death of the plant organ as it necessitates cell viability and is often reversible until the late stages of development. The environmental stress factors such as drought, water logging, high or low solar radiation, extreme temperatures, ozone and other air pollutants, and excessive soil salinity, besides inadequate mineral nutrition in soil, negatively infl uence the senescence. These stress factors disturb the endogenously regulated system of the plant tissue which may result in promoting the process of the senescence. Despite the initiation by environmental factors, the process of senescence is coordinated through a common signalling network by endogenous and exogenous signals involving the signalling molecules ethylene, abscisic acid (ABA), salicylic acid (SA) and jasmonic acid (JA).