Photosynthesis under Osmotic Stress. A Possible Cause of the Osmotic Stress Induced Susceptibility to Photoinhibition

Abstract

It has been proposed that drought by restricting carbon assimilation by CO2 depletion (stomatal closure) or by biochemical alterations in the chloroplast could predispose the photosynthetic apparatus to photoinhibition. However experimental data have shown contradictory results depending upon the considered species : in Nerium oleander (1) and in low light adapted willow (2), they indicated a susceptibility to photoinhibition during drought while those made in sunflower (3) and in cotton (4) demonstrated that water stress does not modify photosynthetic apparatus susceptibility to photoinhibition. This discrepancy questions the underlying causes of this susceptibility and suggests that the water stress induced slowdown of carbon metabolism is not the main factor that predisposes the plants to photoinhibition during drought.