Effect of hexavalent chromium [Cr(VI)] stress in roots of Cr-tolerant and Cr-sensitive barley cultivars

Abstract

The effect of different chromium [Cr(VI)] concentrations (0, 75, 150 and 225 μM) on dehydrogenase activity, total soluble protein, proline, malondialdehyde (MDA) and antioxidant enzymes was investigated in the roots of two barley cultivars (Cr-tolerant Zeynelağa and Cr-sensitive Orza-96) in hydroponic experiments. The root dehydrogenase activity and protein content decreased with an increase in the Cr(VI) concentration, but no significant difference was found between the two barley cultivars. Cr(VI) stress increased the contents of proline and MDA in both cultivars, but this effect was more pronounced in Orza-96 than in Zeynelağa. The activities of antioxidant enzymes, including superoxide dismutase (SOD), ascorbate peroxidase (APX) and guaiacol peroxidase (POD), exhibited changes. The SOD activity increased in Zeynelağa and decreased in Orza-96 at 225 μM Cr(VI) compared to their controls. Cr(VI) stress decreased the APX and POD activities. Zeynelağa had greater APX activity than Orza-96 at 150 and 225 μM Cr(VI). However, there was no marked difference in POD activities between the two cultivars. The decrease in root dehydrogenase activity and protein content, the increase in proline and lipid peroxidation, and the alterations in the activities of antioxidant enzymes may be indicative of oxidative stress induced by Cr(VI).