Interactive effects of gibberellic acid (GA(3)) and salt stress on growth, ion accumulation and photosynthetic capacity of two spring wheat (Triticum aestivum L.) cultivars differing in salt tolerance

A sand culture experiment assessed whether gibberellic acid (GA(3)) could alleviate the adverse effects of salt stress on the growth, ion accumulation and photosynthetic capacity of two spring wheat cultivars, Barani-83 (salt sensitive) and SARC-I (salt tolerant). Three-week-old plants of both cultivars were exposed to 0, 100 and 200 mol m(-3) NaCl in Hoagland's nutrient solution. Three weeks after the initiation of salt treatments, half of the plants of each cultivar were sprayed overall with 100 mg L-1 GA(3) solution. Plants were harvested 3 weeks after the application of GA(3). Fresh and dry weights of shoots and roots, plant height and leaf area were decreased with increasing supply of salt, but gibberellic acid treatment caused a significant ameliorative effect on both the cultivars with respect to these growth attributes. However, GA(3) caused no significant change in grain yields but increased grain size in both the cultivars. Saline growth medium caused a marked increase in the concentrations of Na+ and Cl- in shoots and roots of both the lines. However, with the application of GA(3) accumulation of Na+ and Cl- was enhanced in both shoots and roots of both wheat lines, but more ions accumulated in salt sensitive Barani-83 than in salt tolerant SARC-1. Net CO2 assimilation rate (A) of both wheat lines decreased consistently with increasing supply of NaCl, but application of GA(3) alleviated the effect of salt stress on this variable in both the cultivars. However, the ameliorative effect of the hormone was more pronounced in Barani-83 than in SARC-1. Although water-use efficiency (A/E = CO2 assimilation/transpiration) and intrinsic water use efficiency (A/g(s) = CO2 assimilation/stomatal conductance) decreased significantly with increasing salt concentration of the growth medium in both the cultivars, GA(3) was more effective in enhancing both the water-use attributes in Barani-83 than in SARC-1. Overall, GA(3) treatment stimulated the vegetative growth of both cultivars of wheat under salt stress, but it caused a slight reduction in grain yield. GA(3) treatment enhanced the accumulation of Na+ and Cl- in both shoots and roots of wheat plants under salt stress. It also caused a significant increase in photosynthetic capacity in both lines at the vegetative stage under both saline and non-saline media.