[Effects of arsenic on maize growth, antioxidant system, and ion distribution]

A greenhouse sand culture experiment was conducted to study the effects of arsenic (As) on the biomass accumulation, photosynthetic pigments, antioxidant system, and the absorption and distribution of As and mineral ions in maize Zhengdan 958. At lower concentrations (<2 mg As x L(-1)), As stimulated the growth of maize seedlings, and increased the plant height, taproot length, and biomass accumulation significantly; at higher concentrations (>4 mg As x L(-1)), As inhibited the seedlings growth severely. At 2 mg As x L(-1), the chlorophyll a, b, and a+b contents reached their peaks; but with increasing As concentration, the chlorophyll contents decreased gradually. At 10 mg As x L(-1), the destruction of chloroplast structure and the dissolution of thylakoid membrane were observed by electron microscopy. With increasing As concentration, the activities of antioxidant enzymes SOD, POD, and CAT in root increased, and those in leaf reached the maximum at 8 mg As x L(-1). The sensibility of the enzymes in leaf to As stress was in the order of POD >CAT>SOD. Correlation analysis showed that the contents of MDA, soluble sugar, and soluble protein were positively correlated with As concentration. High concentration As inhibited the absorption of P, K, Ca, Fe and other elements obviously. And comparing with shoot, root was more sensitive to As stress. The growth indices of root could be more available to be used as the indicators of plant arsenic toxicity.