Effect of Ca~(2+) pretreatment on the harm of maize seedlings by acid rain

：The protective effect of calcium pretreatment on the harm of maize seedlings by acid rain was studied through sand cultivation experiment.The results showed that under acid rain, the chloraphyll content, the chlorophyll a/b ratio and the pH value of leave cell juice reduced; the activity of superoxide dismutase -SOD- increased first and decreased under the acid rain of pH2.5,that of catalase -CAT- decreased,while that of peroxidase -POD- increased obviously with membrane lipid peroxidation enhanced. However, under the same acid rain coercion, in the maize seedlings pretreated with CaCl2, the chlorophyll content and chlorophyll a/b ratio increased, the pH value of leave cell juice was stable; the activity levels of SOD and CAT increased, and that of POD decreased relatively; the membrane lipid peroxidation decreased, but the contents of chlorophyll and protein and net photosynthesis rate increased. Therefore,the Ca2+ pretreatment could reduce the harmful effect of acid rain on maize seedlings .