Senescence and Heat Stress Induced Alterations of Photosynthetic Electron Transport

Abstract

Loss of photosynthetic competence during leaf senescence is attributable at-least in part, to the loss of photosynthetic electron transport. The impairment of photosynthetic electron flow inflicted by a variety of environmental stresses, including senescence, appears to be due to the alterations of chloroplast integrity, thylakoid membrane structure and dynamics. There are reports suggesting that both stress-induced senescence and temperature stress bring about similar phenomenological changes in chloroplast membrane linked functions. in this report we wish to review the nature and sequence of changes in the chloroplast photoelectron transport activities by stress-induced senescence and thermal stress. Chloroplast photosynthetic electron transport activities exhibit regular periodic time dependent oscillations. These oscillations possibly reflect the rhythmic changes in membrane dynamics. We have also examined the effect of leaf aging on such periodic oscillations in chloroplast activity.