Response of antioxidant defence system in soybean nodules and roots subjected to cadmium stress

Abstract

The antioxidant defence system of soybean (Glycine maxL.) nodules and roots was studied in plants subjected to three different concentrations (50, 100 and µ200 M ) of CdCl ₂ . Cadmium (Cd)-induced oxidative stress was determined by lipid peroxidation, which remained unaltered in nodules and roots treated with 50 µM Cd(II). No changes were observed in nodules treated with 100 M Cd(II), while a 20% increase was found in roots and 200 µM Cd(II) produced an increase of about 55% in both tissues. The soluble antioxidant defence, reduced glutath one(GSH) and the corresponding reduced/oxidised glutathione (GSH/GSSG) ratio showed different behaviour in both tissues, decreasing in roots with 100 and 200 µM Cd(II). No changes were observed in the GSH/GSSG ratio in nodules under the three Cd treatments. However, ascorbate content and ascorbate/dehydroascorbate (As/DAs) ratio were diminished in nodules and roots subjected to the three Cd concentrations. Regarding the antioxidant enzymes, it was found that, except for catalase, a general decrease in nodule enzyme activities was produced only under the 200 µM Cd(II) treatment. Nevertheless, root enzymatic antioxidant defences showed significant increments in L -ascorbate peroxidase (APOX), dehydroascorbate reductase (DHAR) and glutathione reductase (GR) activities under lower Cd treatment, while the enzyme activities decreased with the two higher concentrations of CdCl ₂ . These results suggest that soybean roots were more affected than nodules by Cd treatments, although the higher Cd concentration produced oxidative stress and deleterious effects in antioxidant defence system in both tissues.