Abstract: With the development of urbanization and industrialization, the rising concentration of troposphere ozone threatens human health and plant growth, which arouses wide public concern. An experiment was conducted to examine the ecophysiological responses of white clovers (Trifolium repens), which were exposed to different doses of ozone (ambient air, 80 and 160 nmol·mol^-1) in opentop chambers (OTCs). The results showed that (1) O₃ induced typical visible symptoms on white clover’s leaves, and increased the producing rate of O₂^-_·, H₂O₂ content, MDA content in the leaves, improved the activity of antioxidant enzymes, while decreased the content of photosynthetic pigments. (2) Elevated O₃ inhibited white clover’s growth, especially in root. Compared with the control, 80 and 160 nmol·mol^-1 O₃ decreased white clover’s total biomass by 45.80% and 53.12%, and the root dry mass by 61.86% and 67.36%, respectively. (3) 80 nmol·mol^-1 O₃ promoted the synthesis of total phenols and improved the antioxidant level, but it couldn’t ameliorate the decrease of biomass. However, 160 nmol·mol^-1 O₃ decreased the antioxidant capacity of white clover. Meanwhile, it not only resulted in a great loss of total biomass but also caused fatal or serious injuries for white clover. White clovers were sensitive to O₃, so the elevated O₃ may have bad effect on white clover’s growth and turf grass quality.

Key words: water and nitrogen interaction, ammonia volatilization, winter wheat, yield.