Effect of NaCl Stress on Growth and Photosynthetic Characteristics of Apple on Four Different Rootstock-scion Combinations

Aiming to provide advice for the selection of NaCl-resistance tree type and NaCl-resistance mechanism,four group of three years old apple trees cultivated in the pot with different rootstock-scion combinations were stressed by NaCl with different concentration(0,0.2%,0.4% and 0.6% NaCl) in the treated soil.The effect of NaCl stress on the synthesis of chlorophyll,conductivity leaf areas and the photosynthetic capacity were investigated.The results showed that the net photosynthetic rate(Pn),stomatal conductance(Gs),transpiration rate(Tr),the content of chlorophyll and leaf growth reduced,but cell membrane permeability increased when increasing stress concentration of NaCl.Chlorophyll b was more sensitive to salt stress than chlorophyll a.NaCl-resistance of different rootstock-scion combination were different: the NaCl resistance of Changfu 2 grafted on M26 Rootstock was superior to that of Fuhungzaoga;the NaCl resistance of Gala grafted on Begonia rootstock was better than that of Shaanfu No.3.The photosynthesis decline in the low-salinity stress was principally influenced by stomatal limitation,and in the middle and high salinity stress,stomatal limitation and non-stomatal limitation plays a role commonly.