Salt and osmotic stress-induced changes in physio-chemical responses, PSII photochemistry and chlorophyll a fluorescence in peanut

Abstract

Peanut (Arachis hypogaea L.) is an important cash crop in arid and semi-arid region. Study reports effects of salinity and osmatic stress on photosynthetic machinery along with physio-biochemical responses in peanut. Salt and osmotic stress negatively affected growth of peanut. Under stress condition, accumulations of biomolecules maintained osmotic adjustment and help to prevented damage due to reactive oxygen species (ROS) accumulation. Stress caused ROS generation, which caused destruction of cellular processes and ultimately resulted in reduced photosynthesis. The higher chlorophyll a/b ratio indicated the reduced size of PSII light-harvesting antenna in peanut under stress. Lower φ(R0) in peanut under stress indicated inefficient functioning of PSI acceptor side. Prompt fluorescence indicated damages to electron transport chain at the PSI acceptor side in a stress strength and duration dependent manner in peanut. The change in delayed fluorescence under stress condition and increment in non-reducing reaction center results in lower electron transport. The δVI–P and δFI–P have been correlated with PsaD protein of PSІ and the results indicated lower electron transport and higher ROS generation in peanut under stress. At higher strength, salinity and osmotic stress induced photo-inhibition, which in turn lowered the PSII photosynthetic yield, quantum yield of PSII electron transport and capturing efficiency of excitation energy by open PSII RCs in peanut.