Combined effect of soil acidification and lead ion on antioxidant system in soybean roots

Abstract

Soil acidification and lead (Pb) pollution seriously affect the antioxidant system in plants. However, studies on their combined effects on the antioxidant system in plant roots are limited. Here, the combined effects of soil acidification and Pb 2+ on peroxidase (POD) activity, catalase (CAT) activity, malonydialdehyde content, cell membrane permeability and Pb content in soybean roots at different growth stages were investigated. We showed that at the seedling stage, combined treatment with soil acidification at pH 4.5/3.5 and 0.3 mM Pb 2+ increased POD activity, and combined treatment with soil acidification at pH 3.0 and 0.3/0.9 mM Pb 2+ increased CAT activity. Combined treatment with soil acidification at pH 4.5 and 0.9 mM Pb 2+ also increased CAT activity at the flowering and pod-formation stage. The remaining combined treatments decreased the POD activity, CAT activity and malonydialdehyde content, but increased the membrane permeability in the roots. Moreover, the combined effects of soil acidification and Pb 2+ on the antioxidant system in soybean roots at the seedling stage were stronger than those at the flowering/pod-formation stage and seed-filling stages. Furthermore, the combined effects on the antioxidant system resulted from the accumulation of Pb in the roots.