Eco- toxicological Effects of Selenium Stress on Wheat (Triticum aestium L.) and Its Critical Value

The effects of selenium added to soil on the growth and scavenging system of activated oxygen of wheat (Triticum aestium L.) were studied through pot experiment. It was found that wheat biomass, the content of chlorophyll a, chlorophyll a/b and the activities of antioxidative enzymes (SOD, POD, CAT, GSH- Px) increased obviously, with MDA content decreasing, at low levels of Se (8 mg· kg- 1) added to soils; while, at high levels (16 mg· kg- 1) of Se added to soils, the biomass, the content of chlorophyll a and chlorophyll a/b were obviously inhibited, the activity of GSH- Px and MDA content increased, the activities of SOD and CAT decreased significantly, but the activity of POD showed no change. The concentration of Se in soil significantly was correlated to the physiological indexes (roots biomass, shoots biomass, chlorophyll a/b, content of MDA, the activities of SOD and CAT). According to the pot experiment, the inhibition rate of roots biomass or shoots biomass “ 10% ” could be regarded as the critical value, and the critical content of Se in soil was estimated to be 30 mg· kg- 1.