Effects of cadmium on antioxidant enzyme activities in sugar cane

Sugar cane (Saccharum officinarum L, cv. Copersucar SP80-3280) seedlings were grown in nutrient solution with varying concentrations (0, 2 and 5 mM) of cadmium chloride for 96 h. Leaves were analysed for catalase (CAT), glutathione reductase (GR) and superoxide dismutase (SOD) activities. Although a clear effect of CdCl2 on plant growth was observed, the activity of SOD was riot altered significantly. However, the CAT activity decreased as the concentration of CdCl2 increased. GR exhibits a significant increase in activity at 2 and 5 mM CdCl2. CAT and SOD isoenzymes were further characterised by analysis in non-denaturing PAGE. Activity staining for SOD revealed up to seven isoenzymes in untreated control and 2 mM CdCl2 treated plants, corresponding to Cu/Zn-SOD isoenzymes. At 5 mM CdCl2, only six Cu/Zn-SOD isoenzymes were observed. No Fe-SOD and Mn-SOD isoenzymes were detected. For CAT, one band of activity was observed.