Evaluation of exogenous ascorbic acid application as a protective agent against simulated acid rain in Persian maple (Acer velutinum Boiss)

摘要

Air pollution is a problem at recent years which progressively increases. This study was accomplished to determine whether ascorbic acid could be applied in counteracting the adverse effects of acid rain (AR) stress. Accordingly, three-year-old Persian maple seedlings were subjected to the foliar application of ascorbic acid (AsA) at three levels (0, 1 and 2 mM). Afterwards, at each AsA levels, the plants were exposed to four different rain regimes: pH 3, 4, 5 and near neutral (pH 6) as control. 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 3.0. AsA efficiently impeded of appearance of visible AR-induced injury symptoms. Results also showed that membrane injury, indicated by electrolyte leakage (EL), and lipid peroxidation (LPO) increased following exposure to the acid rain. On the contrary, AsA considerably diminished LPO and EL. It also prevented from leaf chlorophyll degradation caused by AR of pH 3.0. Both AR and AsA treatments did not significantly affect superoxide dismutase (SOD) activity. However, AsA enhanced peroxidase (POD) and ascorbate peroxidase (APX) activities particularly at pH 3.0 AR, thereby plant leaves remained health. A hypothesis can be represented that elevated activity of POD and APX are important in the plant defense against AR stress.