Role of Nitrogen and Gibberellin (GA₃) in the Regulation of Enzyme Activities and in Osmoprotectant Accumulation in Brassica juncea L. under Salt Stress

Salt stress alters a wide array of plant metabolic mechanisms. Different strategies of the application of nutrients and phytohormones are required to overcome the adverse effects of salt stress. The main objective of the present study was to determine if added nitrogen (N) and gibberellin (GA₃) in growth medium could alleviate the adverse effects of salt stress on plant metabolism. Two-week-old plants were fed with: (i) 0 m m NaCl + 0 mg N kg⁻¹ sand + 0 m GA₃ (control), (ii) 100 m m NaCl + 0 mg N kg⁻¹ sand + 0 m GA₃, (iii) 0 m m NaCl + 40 mg N kg⁻¹ sand + 0 m GA₃, (iv) 0 m m NaCl + 0 mg N kg⁻¹ sand + 10⁻⁵ m GA₃, (v) 100 m m NaCl + 40 mg N kg⁻¹ sand + 0 m GA₃, (vi) 100 m m NaCl + 0 mg N kg⁻¹ sand + 10⁻⁵ m GA₃, (vii) 100 m m NaCl + 40 mg N kg⁻¹ sand + 10⁻⁵ m GA₃. Growth and physio-biochemical attributes i.e. shoot length, leaf area, fresh weight, dry weight, net photosynthetic rate, stomatal conductance, malondialdehyde concentration, electrolyte leakage, total chlorophyll concentration, nitrate reductase and carbonic anhydrase activities, proline and glycinebetaine concentration, leaf - N, potassium (K) and sodium (Na) concentration and K/Na ratio were affected by NaCl treatment. But application of N or GA₃ alone as well as in combination proved beneficial in alleviating the adverse effects of salt stress on these growth and physio-biochemical parameters. However, N applied with GA₃ proved more effective than N and GA₃ applied alone. The results revealed that combined application of N and GA₃ may ameliorate most of the attributes and prove to be a physiological remedy to increase the tolerance against the ill effects of salt stress in Brassica.