Abstract: Taking the seedlings of typical subtropical economic tree species Myrica rubra in Zhejiang Province as test materials, a pot experiment was conducted to study their water physiological characteristics under effects of simulated acid rain (pH 2.5 and pH 4.0), with water (pH 5.6) as the control. Season, year, and acid rain all had significant effects on the  photosynthetic rate (P_n). Among the treatments, the P_n had a greater difference in summer than in spring and autumn, and was higher in treatment acid rain (pH 4.0). Season, year, acid rain, and the interactions of season and year and of the three factors had significant effects on the stomata conductance (G_s), and also, the G_s had a greater difference among the treatments in summer than in spring and autumn. Acid rain had inhibitory effect on G_s. Season, year, acid rain, and the interactions of season and year and of season and acid rain affected the transpiration rate (T_r) significantly. Same as P_n and G_s, the T_r had a greater difference among the treatments in summer than in spring and autumn. Acid rain (pH 2.5) had the strongest inhibitory effect on T_r. Acid rain and the interactions of season and year and of season and acid rain had significant effects on the water use efficiency (WUE), and acid rain (pH 2.5) had definitely positive effect on the WUE.

Key words: simulated acid rain, Myrica rubra, seedling, water physiology