Growth and antioxidant responses in mustard (<i>Brassica juncea</i>L.) plants subjected to combined effect of gibberellic acid and salinity

The effects of salt stress on plant growth parameters, lipid peroxidation and some antioxidant enzyme activities [superoxide dismutase (SOD; EC 1.15.1.1), catalase (CAT, EC 1.11.1.6), peroxidase (POD, EC 1.11.1.7), glutathione reductase (GR; EC EC 1.6.4.2) and ascorbate peroxidase (APX, EC 1.11.1.11) activity] were studied in the leaves of mustard. Plants were exposed to two different concentrations of NaCl stress (100 and 150 mM) for 45 days and were sprayed with GA3 (75 ml pot−1, conc. 75 mg l−1) once a week. Salt stress resulted in decrease in the growth and biomass yield of mustard but the exogenous application of GA3 enhanced these parameters significantly. Application of GA3 counteracted the adverse effects of NaCl salinity on relative water content, electrolyte leakage and chlorophyll (Chl) content. GA3 was sufficient to attenuate partially the stimulatory effect of NaCl supply on proline and glycinebetaine biosynthesis. GA3 reduced lipid peroxidation in the leaves, which was increased during salt stress. The activity of all the antioxidant enzymes was increased significantly during salt stress in mustard. The exogenous application of GA3 decreased the enzyme activity. The results of the present study indicate that usage of GA3 reduces the harmful effects of salinity and increases resistance to salinity in mustard plant.

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