Mercury-induced oxidative stress in tomato seedlings

Mercury content and distribution as well as its effects on growth and oxidative stress were investigated in 30-day-old tomato seedlings (Lycopersicon esculentum Mill.). The content of Hg increased with external Hg concentrations, and was considerably higher in roots than in shoots. Among the leaves, the mature leaves accumulated more. Excess Hg suppressed biomass production of both roots and shoots and reduced chlorophyll content in leaves. Further, substantial increases of H2O2 content, malondialdehyde formation, and antioxidant enzyme activities such as superoxide dismutase (SOD), catalase (CAT), and peroxidase (POX) were observed in Hg-stressed plants in comparison with controls. The results suggest that the phytotoxic effects of Hg in tomato seedlings may be achieved by an enhanced production of active oxygen species (AOS) and subsequent lipid peroxidation. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.