Biochemical Changes Associated with Senescence

When senescence begins many physiological and biochemical changes take place. For example, one of the important changes observed is in chlorophyll content. Its level starts declining. As a result, the capacity of CO₂ fixation also declines and the overall structure of chloroplast in terms of organisation of thylakoids gets disturbed. For quite some time the rate of respiration remains constant but later it also drops and the supply of ATP is reduced. It is also shown that a number of degradative enzymes like proteases (hydrolyse proteins), ribonucleases (hydrolyse nucleic acids), β-glucan hydrolases (which loosens cell wall), chlorophyllase (which degrades chlorophyll) are produced which result in catabolism and finally over a period of time, the plant succumbs and dies.