senescence

Senescence in botany refers to the aging and eventual death of plant cells, tissues, organs, or the entire plant. This process is often a programmed and adaptive part of a plant's life cycle, rather than a result of external damage.1

Key aspects of senescence include:
* Types of Senescence: It can affect individual cells (like those forming xylem vessels), organs (such as leaves), or the whole plant, as seen in annual plants that complete their life cycle in one season.1
* Physiological Changes: Senescence involves degenerative changes in cells, accumulation of breakdown products, and metabolic shifts. Protein and nucleic acid synthesis ceases, and respiration rates eventually decline.1
* Hormonal Influence: Plant hormones like cytokinins and auxins can play a role in regulating senescence. Cytokinins, synthesized in roots, can delay senescence and help maintain chlorophyll and protein content in leaves.12
* Environmental Factors: Photoperiod (day length) and temperature significantly influence senescence, particularly in perennial plants where leaf fall is linked to seasonal changes and dormancy.13

While senescence can lead to the death of the individual plant, it is crucial for the plant's overall economy, contributing to survival through the propagation of seeds and adaptation to environmental cycles.1