Abstract: Using a pot culture experiment, the response of one-year-old seedlings of Cyclobalanopsis gilva from three provenances to drought stress was assessed to understand the adaptation mechanisms of C. gilva to drought stress. The seedlings originating from Qingyuan of Zhejiang Province, and Dongkou and Jingxian of Hunan Province were observed for their growth and physiological properties in this experiment. The growth, biomass production and allocation, free water and bound water and endogenous hormone contents of leaves, and root vitality of the seedlings were measured. The results showed that as the drought stress increased, the increment of height and stem diameter and the increment of aboveground biomass and root biomass of the seedlings had a trend of decrease, and the ratio of free water to bound water of leaves decreased gradually, while the bound water content increased for all three provenances. However, the changes in free water content did not show a consistent trend. Moreover, the drought stress led to an increase in root vitality of the seedlings from Dongkou and Jingxian of Hunan, while a decrease in root vitality of the seedlings from Qingyuan of Zhejiang. In addition, the drought stress resulted in decreases of gibberellins, brassinolide, indole-3acetic acid and zeatins contents and increases of abscisic acid and methyl jasmonate contents of leaves of the seedlings from all three provenances. The subordinate function analysis showed that the seedlings from Dongkou of Hunan had stronger drought resistance than those from Qingyuan of Zhejiang and Jingxian of Hunan. This result implied that C. gilva seedlings became adaptive to drought stress by decreasing the increment of growth and increasing the increment of root biomass. Meanwhile, maintaining a higher bound water content, decreasing auxin (indole3acetic acid), cytomin (zeatin and brassinolide) and gibberellin contents, and increasing abscisic acid and methyl jasmonate contents, provided the physiological potential of C. gilva’s to resist drought stress.

Key words: floret sterility, pollen., rice, abiotic stress