The seedlings were cultured in the 1/2 Hogland nutrients solution with five salt gradient concentrations［0(CK), 0. 20% , 0. 30% , 0. 40% , 0. 45%)］. During culture, salt injury symptoms in seedlings were recorded, photosynthetic parameters(including gas exchange parameters, chlorophyll fluorescence parameters, chlorophyll content)were measured, and changes of chloroplast ultrastructure were observed. Also, the responses of biomass partitioning to salt stress were assessed at the end of experiment.

Salt-damage symptoms such as yellowing, purplish and anthracnose-like gradually appeared in the leaves of seedlings from bottom to top under salt stress. With the increment of salt concentration and the elongation of stress, leaves and new shoots withered, until the whole plant wilted and died. Periods of 50% survival for treatments with >0. 20% salt concentrations were lower than 20 days. Although gradual increments were monitored in biomass of root /shoot with strength of salt stress, the effects of salt stress on biomass partitioning was still not significant. With the increase of salt concentrations and the lasting duration of culture, net photosynthetic rate(P_n), stomatal conductance(G_s), intercellular CO₂ concentration(C_i)and transpiration rate(T_r) were decreased, but leaf water use efficiency(E_WUE)was improved. Of all salt treatments, photosynthetic parameters in seedlings suffering from 0. 20% salt stress were affected slightly. Compared with a little effect of salt stress on maximum optical quantum yield(F_v/F_m), the potential photochemical activities of PSⅡ(F_v/F₀)were significantly affected by salt stress. Significantly, treatments with >0.20% salt concentrations decreased the contents of chlorophyll a(Chl a), chlorophyll b(Chl b), total chlorophyll(Chl a+b) and carotenoid(Car). Meanwhile, salt stress obviously changed chloroplast ultrastructure, showing that number of starch grains, lipid droplets and osmiophilic globules in chloroplast were increased, and stromal lamellae structure was loose and getting swell with strengthen of salt stress.

Salt stress exerted significantly inhibitions on photosynthetic characteristics and chloroplast ultrastructure, resulting in various salt-damage symptoms on leaves of seedlings and different survival rates corresponding to salt concentrations. Considering the responses of all measured indexes to salt stress, growth, photosynthetic characteristics and chloroplast ultrastructure in seedlings of Cornus hongkongensis subsp. elegans treated with 0.20 % salt concentration were similar to that of CK, which is in accord with the results of field trial.