Effects of different concentrations of selenate and selenite on growth and physiology of Chinese cabbage

Chinese cabbage grown in pots was exposed to different concentrations of selenate (Se(Ⅵ)) and selenite (Se(Ⅳ)) to determine the effects of selenium species and concentration on plant growth and physiological metabolism. Lower selenium concentration (Se (Ⅳ) 10.0 mg·kg-1 and Se (Ⅵ) 5.0 mg·kg-1) stimulated the plant growth. The roots of the cabbage thickened,proline content rose and malondialdehyde (MDA) content dropped,enhancing the anti-adveristy of the plant. In contrast,higher selenium concentrations inhibited plant growth. Proline content decreased and MDA content rose while dry weight of shoots and roots declined significantly as selenate and selenite concentrations increased(p 0.01). The selenium concentration which induced inhibition of root growth was 60.0 mg·kg-1 for Se(Ⅳ) and 20.0 mg·kg-1 for Se(Ⅵ). At the same selenium concentration,cabbage biomass after selenite treatment was 1.1 to 3.0 fold greater than that after selenate treatment. Therefore,both the bioavailability and toxicity of selenate were greater than those of selenite under these experimental conditions. Plants grown in the presence of Se (Ⅵ) accumulated higher amounts of selenium in shoots in comparison to plants grown in the presence of Se (Ⅳ). For selenate exposed plants,the selenium concentration was higher in shoots than in roots,while for selenite exposed plants,the selenium concentration was higher in roots than shoots. Analysis of the factors which affected growth and physiology of Chiense cabbage showed that shoot biomass was an ideal indicator for cabbage growth on selenate and selenite polluted soil.