Effects of NaCl Stress on the Characteristics of Photosynthesis and Chlorophyll Fluorescence at Seedlings Stage in Different Sea Island Cotton Genotypes

Objective The effects of NaCl stress on photosynthesis and chlorophyll fluorescence of sea island cotton genotypes were studied.Method Two sea island cotton varieties,Xinhai 21(XH21,NaCl sensitive genotype) and Xinhai 28(XH28,NaCl tolerant genotype) were selected,and germinated in full nutrient solution.NaCl was added into solution at 3-leaf full expanding stage and NaCl concentration levels at 0,50,100,150,200 and 250 mmol·L-1 respectively.Photosynthetic parameters,chlorophyll fluorescence variation were investigated after 30 d.Result The results showed that,under low NaCl concentration stress,the growth of the plants,fresh weight,biomass,chlorophyll content were enhanced,ΦPSⅡ,qP,NPQ were increaseed as well,all these increased Pn of leaves in tolerant genotype Xinhai 28.Under high NaCl stress,plant growth restrained significantly in both genotypes,Pn,Gs,Fv/F0,Fv/Fm,ΦPSⅡ and qP were reduced,while NPQ and Ci increased.Conclusion The decrease of net photosynthetic rate was considered as a result of no-stomatal restriction turning stomatal restriction along with NaCl concentration increase.Photosynthetic parameters and chlorophyll fluorescence were highly correlated with genotypes's salt tolerance and salt concentration.