Interactive effects of gibberellic acid (GA₃) and salt stress on growth, ion accumulation and photosynthetic capacity of two spring wheat (Triticum aestivum L.) cultivars differing in salt tolerance

Abstract

A sand culture experiment assessed whether gibberellic acid(GA₃) could alleviate the adverse effects of salt stress on thegrowth, ion accumulation and photosynthetic capacity of two spring wheatcultivars, Barani-83 (salt sensitive) and SARC-I (salt tolerant).Three-week-oldplants of both cultivars were exposed to 0, 100 and 200 molm⁻³ NaCl in Hoagland's nutrient solution. Threeweeks after the initiation of salt treatments, half of the plants of eachcultivar were sprayed overall with 100 mg L⁻¹GA₃ solution. Plants were harvested 3 weeks after theapplication of GA₃. Fresh and dry weights of shoots and roots, plantheight and leaf area were decreased with increasing supply of salt, butgibberellic acid treatment caused a significant ameliorative effect on both thecultivars with respect to these growth attributes. However, GA₃caused no significant change in grain yields but increased grain size in boththe cultivars. Saline growth medium caused a marked increase in theconcentrations of Na⁺ and Cl⁻ in shoots androots of both the lines. However, with the application of GA₃accumulation of Na⁺ and Cl⁻ was enhanced inboth shoots and roots of both wheat lines, but more ions accumulated in saltsensitive Barani-83 than in salt tolerant SARC-1. Net CO₂assimilation rate (A) of both wheat lines decreased consistently withincreasingsupply of NaCl, but application of GA₃ alleviated the effect of saltstress on this variable in both the cultivars. However, the ameliorative effectof the hormone was more pronounced in Barani-83 than in SARC-1. Althoughwater-use efficiency (A/E = CO₂assimilation/transpiration) and intrinsic water use efficiency(A/g_s = CO₂ assimilation/stomatalconductance) decreased significantly with increasing salt concentration of thegrowth medium in both the cultivars, GA₃ was more effective inenhancing both the water-use attributes in Barani-83 than in SARC-1. Overall,GA₃ treatment stimulated the vegetative growth of both cultivars ofwheat under salt stress, but it caused a slight reduction in grain yield.GA₃ treatment enhanced the accumulation of Na⁺ andCl⁻ in both shoots and roots of wheat plants under saltstress.It also caused a significant increase in photosynthetic capacity in both linesat the vegetative stage under both saline and non-saline media.