Putrescine alleviation of growth in salt stressed Brassica juncea by inducing antioxidative defense system

Seedlings of Indian mustard (Brassica juncea L.cv. RH-30) grown in controlled condition (irradiance 75 W m(-2), RH 60-70% and temp. 25 +/- 2 degrees C) for 7d and watered with Hoagland's solution containing different level of NaCl (50-250 mmol./L NaCl) with or without putrescine (PUT, 0.1 mmol/L) were examined for PUT amelioration of NaCl induced inhibition in seedling growth by altering activity of antioxygenic enzymes and level. of free radicals in the leaves. Salinity caused reduction in seedling growth and biomass accumulation was parallel to increased superoxide (O-center dot(2)-), hydrogen peroxide (H2O2) levels, lipid peroxidation (MDA content) and electrolyte leakage in leaf tissues which were reversed significantly by PUT The antioxygenic enzymes viz superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), ascorbate peroxidase (APX) and glutathione reductase (GR) were differentially altered, depending on salt level. PUT induction of enzyme was in the following order APX > GR > CAT > SOD > POD in leaf tissues of salt stressed seedlings. PUT increased the level of glutathione and carotenoids in leaf tissues. This finding suggests that PUT might be activating antioxygenic enzymes and elevating antioxidants there by controlling free radical generation, hence preventing membrane peroxidation and denaturation of biomolecules resulting into improved seedling growth under salinity. (c) 2005 Elsevier GmbH. All rights reserved.