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

Effects of drought and salinity on growth and activities of superoxide dism utase (SOD) forms were studied in narrow-leafed lupins (Lupinus angustifoli us L.). Shoot dry weight and the elongation rate were depressed after 3 day s 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 seve rity of drought stress. Two days after resupplying water, leaf water potent ial and the activity of Cu/ZnSOD returned to the control level, but the FeS OD 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 conce ntration in the growth medium. Salinity stress enhanced activity of Cu/ZnSO D by 145% without influencing the activity of other SOD forms. Drought and salinity differentially influence activity of SOD forms in narrow-leafed lu pins, indicating that different mechanisms may be involved in oxidative str ess injury caused by drought and salinity. (C) 1999 Elsevier Science Irelan d Ltd. All rights reserved.