Cadmium (Cd) is one of the most toxic environmental pollutants for soils. The seedlings of S. nigrum were exposed to half-strength Hogland solution with 100 μmol/L CdCl2 for 1-4 days, and the activity of antioxidant enzyme in leaves and roots was investigated. The results show that the contents of MDA and H2O2 increase in leaves and roots and the increase of MDA in leaves is larger than that in roots while the increase of H2O2 in roots is larger than that in leaves. Also, the activities of SOD, CAT, APX, and POD in leaves and roots are enhanced with prolonged Cd treatment. It is suggested that the H2O2 accumulation induced by Cd stress leads to oxidative stress and the increase of the oxitioxidant enzyme activity may be one of the mechanisms of Cd detoxification in S. nigrum. H2O2 in leaves may be scavenged by both CAT and APX while the H2O2 in roots may be mainly scavenged by APX.
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