Effects of elevated O_3 and CO_2 on the antioxidant enzyme activities in Pin us tabulaeformis needles.

LI Xiang1,2, HE Xing-yuan1, CHEN Wei1, XU Sheng1, YAN Kun 1,2 (1Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110 016, China; 2Graduate University of Chinese Academy of Sciences, Beijing 1 00039, China).

elevated O3; elevated CO_2; Pinus tabulaeformis; antioxidant system.

Four-year-old Pinus tabulaeformis seedlings were planted in open-topped c hamb ers and treated with elevated O3 (80 nmol·mol-1) and/or CO_2 (700 μmo l·mol-1). After treated for three years, the malondialdehyde (MDA) conten t, reactive oxygen species, and antioxidant enzyme activities in the current year needles were analyzed. In treatment elevated O3, the activities of superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT) and de hydroascorbate reductase (DHAR) increased significantly, being 43.1%, 18.9%, 283.5% and 142.6% higher than the control; and in treatments elevated CO_2 an d its combination with elevated O3, only APX and CAT activities were induced r emarkably but still lower than those in treatment elevated O3. Elevated O3 i ncreased the MDA content by 51.8%, whereas the combination of elevated O3 and CO_2 reversed this increase efficiently. No significant differences were obser ved in the superoxide anion (O-·2) generating rat e and H2O2 content among all treatments. All the results demonstrated that elevated O3 was able to eff ectively activate the antioxidant enzyme system in P. tabulaeformis current year needles, while elevated CO_2 could mitigate the negative effects of elevat ed O3 through the actions other than enhancing the antioxidant enzyme activiti es.