Antioxidative efficiency of Triticum aestivum L. exposed to chromium stress.

Wheat (Triticum aestivum L. cv Sonalika) seedlings were grown in presence of K2Cr2O7 (10, 50 and 100 ppm) for 7 days and growth, total chlorophyll, activities of antioxidative enzymes like superoxide dismutase (SOD; EC 1.15.1.1), catalase (CAT; EC 1.11.1.6) and guaiacol peroxidase (POX; EC 1.11.1.7) and lipid peroxidation were determined in root and shoot tissues. Growth of the seedlings was significantly (p < or = 0.05) depressed and at 100 ppm, root length was reduced by 63% and shoot length by 44% in comparison to the respective controls. Total chlorophyll loss in shoots was about 46% at 10 ppm of K2Cr2O7 which further increased to 80% at 100 ppm. Both in root and shoot tissues, activities of SOD and CAT declined with increase of metal in growth medium and it was significant (p < or = 0.05) even at lowest concentration of the metal tested. But POX activity showed a different trend. In root tissues it was decreased whereas in shoots, there was many fold increase in the activity (about 370% over control at 100 ppm). Malondialdehyde (MDA) content increased both in root and shoot tissues, but it reached significant (p < 0.05) level at 50 ppm in roots and at 100 ppm in shoot tissues. Even though antioxidative enzyme activities were not assayed in germinating embryos, inhibition in germination percentage (by 40% at 100 ppm) and increase in lipid peroxidation level (by 71% over control at 100 ppm) were observed in 2-day-old embryos, germinated in presence of K2Cr2O7 (10, 50 and 100 ppm). The results indicated the imposition of oxidative stress situations both during germination and early stages of seedling growth by Cr6 stress, which might be one of the probable reasons behind Cr toxicity in plants.