Abstract: In order to explore the effects of salt stress on photosynthesis characteristics of Malus zumi seedlings, the Malus zumi potted seedlings were used as the experimental materials, and photosynthesis parameters, chlorophyll contents and chlorophyll fluorescence characteristics of the plants were studied under different concentrations of NaCl. The results show that the net photosynthetic rate (Pn), stomatal conductance (Gs), transpiration rate (Tr), potential activity of PSⅡ(Fv/F₀), the actual photochemical efficiency of PSⅡ and contents of chlorophyll b increased firstly and then declined under salt stress, but intercellular CO₂ concentration (Ci) decreased firstly and then increased, and the contents of chlorophyll a and carotenoids decreased continuously. Photosynthesis parameters and contents of chlorophyll b increased under lower salinity (50 mmol·L^-1), which indicated Malus zumi seedlings had a certain resistance to salt stress. The photosynthesis parameters, transpiration rate (Tr), chlorophyll contents of the plants declined with the salt contents increase, and it indicated that the photosystem of the plant was interfered and its photosynthesis performance reduced.

Key words: Malus zumi, salt stress, photosynthetic parameter, chloroplast pigments content, chlorophyll fluorescence characteristics