Abstract: Taking the seedlings of Quercus glauca, a dominant evergreen broadleaf tree species in subtropical area, as test materials, this paper studied their photosynthesis, chlorophyll fluorescence, and chlorophyll content under effects of simulated acid rain with pH 25, 40, and 56 (CK). After 2-year acid rain stress, the net photosynthetic rate of Q. glauca increased significantly with decreasing pH of acid rain. The acid rain with pH 25 and 4.0 increased the stomatal conductance and transpiration rate, and the effect was more significant under pH 25. The intercellular CO2 concentration decreased in the order of pH 25>pH 56>pH 40. The maximum photosynthetic rate, light compensation point, light saturation point, and dark respiration rate were significantly higher under pH 25 and 40 than under pH 56, while the apparent quantum yield was not sensitive to acid rain stress. The maximal photochemical efficiency of PSⅡ and the potential activity of PSⅡ under pH 25 and 40 were significantly higher than those under pH 56. The relative chlorophyll content was in the order of pH 25>pH 56>pH 40, and there was a significant difference between pH 25 and 40. All the results suggested that the photosynthesis and chlorophyll fluorescence of Q. glauca increased under the effects of acid rain with pH 25 and 40, and the acid rain with pH 25 had more obvious effects.

Key words: simulated acid rain, Quercus glauca, photosynthesis, chlorophyll fluorescence, biological trait, fourth-corner statistics, biomonitoring and bioassessment, stream.