[Interactive Effects of Ozone and Drought on Antioxidant Enzyme Activities of Poplar Leaves]

Ground-level ozone (O₃) pollution and drought have become major environmental factors that threaten the normal growth of plants. In this study, we determined the effects of three O₃ concentrations (charcoal-filtered air, CF, non-filtered air, NF and non-filtered air+40 nmol·mol^-1, NF40), two water treatments (well-watered, WW, and mild drought, MD, 60% of WW in volumetric soil water content), and their interactions on the light-saturated photosynthesis rate (A_sat) and on the activity of antioxidant enzymes and soluble proteins of the poplar '546' (Populus deltoids cv. 55/56×P. deltoides cv. Imperial). Results showed that A_sat significantly decreased with elevated O₃, and with interactions between O₃ and drought. Drought significantly reduced the activities of catalase (CAT) and superoxide dismutase (SOD) but did not affect the activities of peroxidase (POD) or ascorbate peroxidase (APX). Reduction ranges in CAT and SOD increased with drought duration. APX activity significantly decreased with increasing O₃ and drought, but soluble protein content did not. Activities of antioxidant enzymes were not significantly affected by elevated O₃ and their interactions. Results provide a scientific basis for protection of poplar plantations in response to increasing O₃ concentrations and drought under environmental changes.