Patterns of Ageing and Death

Plants and their parts develop continuously from germination until death. The latter part of the developmental process, which leads from maturity to the ultimate complete loss of organisation and function, is termed senescence. It is a characteristic of plant behavior that senescence is not simply a running down of the life processes but is a highly ordered and programmed process or series of processes.

According to their habit of growth, plants senesce in many different ways. We will briefly discuss major events of senescence in plants:

1. Whole Plant Senescence: The whole plant may senesce and die at one time after flowering and fruit formation (all annual like wheat, rice, mustard belong to this category). Delay in flowering postpones senescence phase by keeping the plants alive in unfavorable conditions for flowering.

2. Organ Senescence: Parts of the plant like leaves undergo senescence after maturation. Rest of the plant remains alive. New leaves replace senescing leaves.

3. Tissue Senescence: Some tissues like sclerenchyma, tracheids and xylem vessels may senesce and die although the plant as a whole is in a state of good growth.