EFFECT OF EXOGENOUS GLUTATHIONE ON PHOTOSYSTEM II FUNCTIONING OF RICE (ORYZA SATIVA L.) SEEDLINGS UNDER Na2CO3 STRESS

Chlorophyll (Chl) a fluorescence as a non-destructive technique was used to assess photosynthetic information when plants were subjected to environmental stress. Glutathione (GSH) is a strong non-enzymatic antioxidant. The purpose of this study was to estimate rice (Oryza sativa L.) seedlings' response to Na2CO3 stress after spraying exogenous GSH. The results showed that Na2CO3 stress had a negative impact on the development of rice seedlings and reduced SPAD values. The changes of specific energy fluxes (ABS/RC, TR0/RC, DI0/RC) revealed Na2CO3 stress inhibited the activity of photosystem II (PSII) reaction centers (RCs) and chloroplast stability. As shown by the alteration of the polyphasic fluorescence transient (OJIP) parameters, PSII function was less effective due to the reduction of energetic connectivity under Na2CO3 stress, which resulted in an imbalance in electron transfer. However, GSH effectively reversed changes in PSII as well as improved the photochemical efficiency. Therefore, the results suggested that exogenous GSH as a regulator of cellular defense against abiotic stress could effectively alleviate the damage to the PSII RC by Na2CO3 stress and improve the resistance of rice to salt stress.