Drought and salinity differentially influence activities of superoxide dismutases in narrow-leafed lupins

Effects of drought and salinity on growth and activities of superoxide dismutase (SOD) forms were studied in narrow-leafed lupins (Lupinus angustifolius L.). Shoot dry weight and the elongation rate were depressed after 3 days of drought, with leaf water potential dropping to - 1.64 MPa. Activity of total SOD increased by 21%, Cu/ZnSOD by 33% and FeSOD by 50% after 2 days of withholding water; further increases were noted with an increase in severity of drought stress. Two days after resupplying water, leaf water potential and the activity of Cu/ZnSOD returned to the control level, but the FeSOD activity remained high. The activity of MnSOD was unaffected by drought. Root fresh weight and the shoot elongation rate were not affected up to 50 mM NaCl, but were reduced at 100 mM NaCl after 6 days, with leaf water and osmotic potentials being - 1.4 and - 1.8 MPa, respectively. Concentrations of Na⁺ and Cl^- in leaves increased linearly with an increase in NaCl concentration in the growth medium. Salinity stress enhanced activity of Cu/ZnSOD by 145% without influencing the activity of other SOD forms. Drought and salinity differentially influence activity of SOD forms in narrow-leafed lupins, indicating that different mechanisms may be involved in oxidative stress injury caused by drought and salinity.