Effects of Elevated O3 and CO2 on Biomass and Antioxidant System in Needles of Armand Pine

Abstract

Using open top chambers, effects of elevated O3 (80 nmol mol-1) and CO2 (700 µmol mol-1), alone and in combination, were studied on young armand pine (Pinus armandii Franch.) trees. Current-year needles were collected after a growth season in all the treatments. No marked changes were found in the needles under elevated CO2 exposure alone. Needles biomass was significantly decreased by elevated O3, and the decrease was lower in the needles concomitantly exposed to elevated CO2. Hydrogen peroxide and malondialdehyde contents increased significantly in the needles under elevated O3 exposure, but the O3-induced increase was alleviated by elevated CO2. Elevated O3 remarkably reduced ascorbate content and enhanced activities of superoxide dismutase and ascorbate peroxidase, and these changes was all alleviated by elevated CO2. The results suggest that elevated CO2 ameliorated O3-induced oxidative stress in the needles of armand pine. Consequently, needles biomass was less affected at high O3 and CO2 in combination than at high O3 alone. This protection of CO2 against O3 stress was achieved hardly by enhancing antioxidant capability.