Senescence in Plants

Abstract

Plant senescence is the final stage of development during which the plant recycles the valuable cellular building blocks that have been deposited in the leaves and other parts of the plant during growth. These reusable nutrients are then stored in the plant until they can be used in new growth or sent to the seed to provide a nutrient store for the next generation. Maintaining an efficient senescence process is therefore essential for the fitness of the plant or its seed. Senescence is a complex, highly regulated process that requires new gene expression and involves the interactions of many signalling pathways. In crops inappropriately timed senescence can reduce final crop yield, and in many vegetable crops significant postharvest loss is due to senescence. Unravelling the regulatory mechanisms that underlie senescence may have significant impact on increasing future food production. Key Concepts Plant senescence is a recycling process. Senescence confers an adaptive advantage to a plant increasing its fitness or reproductive success. Initiating senescence triggers a regulated series of events that dismantle, degrade and then mobilise valuable cellular processes. The majority of a leaf protein and lipid component is in the chloroplast and it undergoes dramatic structural changes during senescence. Chlorophyll needs to be rapidly degraded during senescence to ensure cells do not die due to phototoxicity. Proteins degraded during senescence release valuable nitrogen and other minerals for mobilisation. Thousands of genes are involved in the regulation of senescence. Most of the major plant hormones have roles in the regulation of senescence.