Abstract: In order to explore the adaptability of Populus ussuriensis Kom. to drought stress, polyethylene glycol(PEG-6000) was used to simulate drought, the growth traits, biomass production and partitioning, the physiological and biochemical response characteristics were determined and analyzed under different stress levels. The seedling height, ground diameter and biomass accumulation of P. ussuriensis decreased significantly with the increase of drought stress intensity and the extension of stress time. The height growth under mild, moderate and severe stress decreased by 17.71%, 20.29% and 45.96%, the growth of ground diameter decreased by 4.78%, 13.62% and 17.29%, and the root ratio increased by 11.93%, 32.61% and 64.10%, respectively. The relative water content of the leaves showed a downward trend and the relative conductivity showed an upward trend. The relative water content under mild, moderate and severe stress was 23.60%, 38.56%, and 66.78% lower than the contrast, respectively, the relative conductivity was 106.97%, 161.84% and 241.75% higher than the contrast, indicating that drought stress caused obvious damage to the leaves. The contents of proline, soluble protein and soluble sugar all showed a trend of increasing first and then decreasing, which was higher than the contrast in the early and middle stages of stress, the change range of mild stress was smaller than that of moderate and severe stress. In the early and middle stages of stress, it was higher than the contrast and the seedlings had certain drought resistance. At the end of the stress period, there was a trend lower than the contrast, the seedling cells and tissues were irreversibly damaged. The net photosynthetic rate of leaves showed a double peak pattern, the stressed seedlings were significantly lower than the contrast and the time of reaching the peak was different. The first peak of the seedlings stressed was 2 h earlier than the contrast. P. ussuriensis can tolerate short-term mild drought stress environment. Moderate and severe drought stress have significant effects on the growth and physiological processes of P. ussuriensis seedlings.

Key words: Populus ussuriensis Kom., drought stress, physiological indicators, net photosynthetic rate