Effects of salt stress on photosynthetic physiology and chlorophyll fluorescence characteristics of grape(Red Globe) seedlings

A pot experiment on effects of salt stress on photosynthetic physiology and chlor ophyll fluorescence characteristics of 1-year old grape(Red Globe) seedlings was conducted.The seedlings were treated with NaCl concentrations of 0.1,0.2, and 0.3 g/kg,and with fresh water as the control.The results showed that with treatment time increasing,the net photosynthetic rate,transpiration rate,stomatal conductance and the leaf chlorophyll concent ration all decreased.Furthermore,the determination of chlorophyll-fluorescence parameters revealed the PSⅡ maximal photochemical efficiency(Fv/Fm),the PSⅡ potential photochemical efficiency(Fv/F0),the maximum quanta yield(Yield),the photosynthetic electron transport(ETR),and the photochemical quenching coefficient(qP) decreased under the NaCl stress.The intercellular CO2 concentration first decreased and then increased,and non photochemical quenching of fluorescence(qN) increased.Salt stress led to decreasing of photosynthesis of from stomatal limitation to nonstomatal limitation.Furthermore,the damage of PSⅡ brought inactivation of photosynthesis center,decrease of both primary capture capacity and assimilation efficiency of light energy,increase of lightenergy consumption by means of heat and final weakening of photosynthesis capacity of Red Globe seedlings.