Abstract: [Objective] To elucidate the regulating mechanism of exogenous SA on Phyllostachys edulis under different water stresses, we investigated the growth and physiological parameters of P. edulis grown under different water treatments. [Method] This experiment was designed in random block. In the experiment, we set five treatments i.e. treatment with normal water supply(CK),drought(D),drought with 0.5 mmol·L^-1 SA(DS1),drought with 1.0 mmol·L^-1 SA(DS2),and drought with 2.0 mmol·L^-1 SA(DS3). By determining physiological indexes such as protection enzymes activity, osmotic regulation substances content, leaf water content, leaf electrolyte leakage rate and chlorophyll content of P. edulis seedlings, the article explored the effect of exogenous salicylic acid (SA) on physiological and biochemical characteristics of P. edulis seedlings. Under drought stress, soluble sugar content, soluble protein content, peroxidase(POD) activity, chlorophyll content, leaf water content and plant biomass significantly (P < 0.05) decreased, while electrolyte leakage rate increased significantly (P < 0.05).[Result] Under drought stress, after treating with 0.5-2.0 mmol·L^-1 exogenous SA, soluble sugar content and POD activity, chlorophyll content, leaf water content and plant biomass of P. edulis seedlings significantly (P < 0.05) increased with increasing content of SA. Meanwhile, the electrolyte leakage rate decreased significantly (P < 0.05), and catalase (CAT) activity and superoxide dismutase (SOD) activity slightly declined in a short period. Under drought stress, after treating with 0.5 mmol·L^-1 SA, electrolyte leakage rate decreased significantly (P < 0.05), while other physiological and biochemical indexes had no significantly change. The results showed that, under moderate drought stress, SA relieved the damage by drought stress to P edulis seedlings by increasing the activity of protective enzymes (especially activity of POD). Meanwhile, exogenous SA increased physiological activity and biomass accumulation of P. edulis by keeping its relativity high level of leaf water and chlorophyll content. Thus, SA improved P. edulis' drought-resistant ability. Within 0.5-2.0 mmol·L^-1, the effect of SA had been increasing with concentration. Under the same concentration, the treating effect of SA was firstly increased and then decreased with time increasing. [Conclusion] Thus,we could conclude that certain concentrations (especially 2.0 mmol·L^-1) of exogenous SA can effectively improve the drought-resistant ability of P. edulis seedlings in a certain period,and relieve the damage under drought in its growth period. Meanwhile, we speculate that SA could have positive effect on increasing the survival rate of afforestation and drought resistant ability of bamboo forests.

Key words: salicylic acid, seedling of Phyllostachys edulis, drought, physiological propertis, drought resistance ability