Excessive chromium (Cr) causes oxidative stress to plants, and the positive effect of selenium(Se) become evident especially in plants subjected to intemal and extemal oxidative stressors. Theimpacts of exogenous Se on Cr-induced oxidative stress and antioxidant system in leaves of Brassicacampestris L. ssp. Pekinensis were investigated by using cellular and biochemical approcaches.Supplementation of the medium witb lower Se level resulted in alleviated growth inhibition and alteredthe distribution of Cr in subcellular of the leaves. Cr-induced lipid peroxidation and superoxide freeradicals (02') overproduction, as well as ultrastructal changes of leaves were largely reversed by Sesupplementation in the medium. Se application significantly altered the Cr effects on anitioxidantenzymes, and significantly increased the activities of superoxide dismutase (SOD) and peroxidase (CAT).The results suggested that Se is able to protect the Brassica campestris L. ssp. Pekinensis against Crtoxicity by: (1) activate the antioxidant enzymes SOD and POD; (2) reduction of oxygen radicals; (3)removal of Cr from metabolically active cellular sites.
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