Effects of Simulated Acid Rain on the Antioxidative System in Cinnamomum philippinense Seedlings

This study examined the importance of the antioxidative defense mechanism during the application of simulated acid rain (SAR) pH 4, pH 3, pH 2, and pH 6 as control treatment in Cinnamomum philippinense seedlings. Analysis was carried out on 1, 10, and 15 days of spraying SAR. In our results, catalase (CAT), ascorbate peroxidase (APx), guaiacol peroxidase (GPOD), and glutathione reductase (GR) activity significantly were induced on 1 day of spraying SAR pH 3 and pH 2, suggesting that C. philippinense seedlings exposed to pH 3 and pH 2 acid rain for only 1 day were under oxidative stress, and antioxidant enzyme were apparently increased until 10 days of spraying SAR pH 4. However, on 10 days of spraying SAR pH 2, the accumulated intensity of acidity significantly inhibited the activities of CAT and APx accompanying with increased concentrations of malonydialdehyde (MDA). On the contrary, GPOD activity and the ascorbic acid ratio were remarkably increased when spraying SAR pH 2 for 15 days. Therefore, GPOD and ascorbate contribute to the scavenging of ROS at stronger acidity stresses. However, they were not enough to avoid cellular damage, since membrane lipids were injured, and necrosis appeared.