Chromium toxicity induces oxidative stress in turnip

Abstract

Effect of chromium (both CrIII and CrVI) were studied on the oxidative damages and the induction of antioxidant defence in turnip. For this purpose turnip (Brassica rapa L.) plants were grown in refined sand under three different sources of chromium, i.e., chromium sulphate (CrIII), potassium chromate (CrVI) and potassium dichromate (CrVI) supplied at 250 µM concentrations for 4, 24 and 168 h (7 days) after 50 days of growth in normal nutrition. The extent of oxidative damage was most in dichromate as it caused a maximum increase in lipid peroxidation and H2O2 concentration in leaves of turnip plants. The growth and biomass of plants decreased, while the levels of chloroplastic pigment and iron increased in plants supplied CrVI (both potassium chromate and potassium dichromate). Exposure of plants to Cr led to increase in Cr concentration, more in the roots than in shoots. Excess supply of Cr (chromium sulphate, potassium chromate and potassium dichromate), though inhibited peroxidase activity (at 4 and 168 h exposure), stimulated catalase, ascorbate peroxidase and superoxide dismutase activities. Localization of different isoforms of APX and SOD on native gels revealed activation of certain isoform in the Cr-treated plants.