Effect of Acid Rain on Morphological and Physiological Characteristics of Persian Maple (Acer velutinum Boiss)

Air pollution is a serious problem at recent years which progressively increases. This study was accomplished in order to more understanding of morphological and physiological responses of acid rain on Persian maple trees as an ornamental and industrial plant. Accordingly, three-year old Persian maple seedlings were submitted based on completely randomized design to four different acid rain regimes: pH 3, 4, 5 and near neutral (pH 6) as control, in tree replications, during 10 days. At the end of experiment, some visible changes such as necrotic spots and leaf marginal wrinkle were observed in the plant leaves sprayed only with AR of pH 3. Results showed that electrolyte leakage (EL) and lipidperoxidation (LPO) amount significantly increased as pH values of AR decreased. However, reducing of AR had no effect on leaf chlorophyll content by pH 4.0, whereas AR of pH 3.0 dramatically degraded it. In addition, AR did not significantly affect superoxide dismutase (SOD) activity. On the contrary, it enhanced peroxidase (POD) and ascorbate peroxidase (APX) activities by pH 4.0, but AR of pH 3.0 markedly decreased them, thereby, the antioxidative system was weakened and injury appeared. Overall, our results cleared that Persian maple was resistant to AR by pH 4.0, while it is certainly susceptible to pH 3.0 and lower pH values.