Response of Antioxidant System in Leaves of <i>Ginkgo</i> <i>biloba</i> to Elevated CO<sub>2</sub> and/or O<sub>3</sub> and its Natural Recovery in an Urban Area

Abstract

Changes of oxidative stress and antioxidant system were studied in leaves of Ginkgo biloba exposed to elevated CO2 and O3 fumigation (2006-2008), and released the gases fumigation for the natural recovery in open-top chambers (OTCs) during the growing season in 2009. Elevated CO2 had no significant effect on hydrogen peroxide (H2O2) and malondialdehyde (MDA) contents, and the activities of antioxidant enzymes in leaves of G. biloba during the gas fumigation in 2008. Elevated O3 increased significantly H2O2 and MDA contents, especially after 90 days of gas fumigation. The adverse effect or damage of elevated O3 on trees during the gas fumigation was also alleviated by the released-O3 exposure during the natural recovery. The antioxidative enzyme including superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX) activities showed higher levels under the natural recovery than under the gas fumigation, which may be a helpful response to scavenging reactive oxygen species (ROS). The results also indicated that future alleviating the emissions of CO2 and O3 would differentially affect the antioxidant system in plants.