HOW DO SENESCING LEAVES LOSE PHOTOSYNTHETIC ACTIVITY

Delay in leaf senescence to a maximal extent is an agronomically desired trait. The photosynthetic capacity of senescing leaves is usually much lower than their normal counterparts. The onset of senescence involves major changes in various characteristics of ribulose-1,5-bisphosphate carboxylase/oxygenase, the enzyme which is thought to rate-limit photosynthesis. In addition, certain selective and specific changes take place in the electron transport process of the senescing chloroplasts. This article provides information on senescence-associated alterations in various partial reactions of photosynthesis and on gene expression which accompany this phenomenon.