Oxidative stress and antioxidant responses in young leaves of mulberry plants grown under nitrogen, phosphorus or potassium deficiency

The aim of this study was to associate the generation of reactive oxygen species (ROS) with induced antioxidant responses and disturbed cellular redox environment in the nitrogen-(N), phosphorus-(P), or potassium-(K) deficient mulberry (Morus alba L. var. Kanva-2) plants. The indicators of oxidative stress and cellular redox environment and antioxidant defense-related parameters were analyzed. Deficiency of N, P or K suppressed growth, accelerated senescence, and decreased concentrations of chloroplastic pigments and glutathione. Lipid peroxidation and activities of superoxide dismutase, ascorbate peroxidase and glutathione reductase were also increased in these N, P, or K deprived plants. Concentration of hydrogen peroxide increased in plants deficient in N or P. Deficiency of N or P particularly altered the cellular redox environment as indicated by changes in the redox couples, namely ascorbic acid/total ascorbate decreased in P-, glutathione sulfydryl/total glutathione decreased in W, and increased in P-deficient plants. Activity staining of native gels for superoxide dismutase revealed increased activity as indicated by increased intensity of bands, and induction of few new isoforms in P- and K-deficient plants. Differences in the patterns of superoxide dismutase isoforms and redox status (ascorbic acid/total ascorbate and glutathione sulfydryl/total glutathione) indicate that N-, P-, or K-deficiency altered antioxidant responses to varying extents in mulberry plants.