Effect of exogenous nitric oxide on chlorophyll fluorescence characteristics in tomato seedlings under NaCl stress

Hydroponic experiment was conducted to investigate the effect of sodium nitroprusside (SNP, an exogenous nitric oxide donor) on chlorophyll fluorescence characteristics in tomato seedlings under 100 mmol·L^-1 NaCl stress. The results show that SNP increase maximum fluorescence (Fm), photochemical efficiency of photosystem II (Fv/Fm), potential photochemical efficiency (Fv/Fo), electron transport rate (ETR), actual photochemical efficiency (ΦPSⅡ), photochemical quenching coefficient (qP) and photochemical efficiency (Prate). However, SNP decreases minimal fluorescence (Fo), non-photochemical quenching coefficient (qN), antenna heat dissipation rate (Drate), excitation pressure (1-qP) and the deviation from full balance between PSⅠand PSⅡ(β/α-1) in tomato seedlings under NaCl stress. This then suggests that nitric oxide reduces excess excitation dissipation, improves photochemical electron transport efficiency and efficiently protects tomato leaf from PSⅡdamage under salt stress.