Impact of exogenously applied ABA on proline metabolism conferring drought and salinity stress tolerance in wheat genotypes

Drought and salinity are the most catastrophic abiotic stresses that affect plant growth and development. Plant initiates alterations at physiological, biochemical and molecular levels to combat adverse effects of drought in which abscisic acid (ABA) plays a pivotal role. The present investigation aims to study the modulation of enzymatic changes conferring stress tolerance in the 7-day-old shoots of five wheat genotypes influenced by exogenously applied ABA during stress. The results revealed that application of ABA (10 μM) positively influenced the shoot length and biomass of Gladius and Drysdale under water deficit and water withholding condition, while Kharchia was the only genotype showing positive response under salt stress condition and nearly negligible effect being observed in PBW 175 and PBW 660. The content of thiobarbituric acid reactive substances was lowered while proline content along with 2,2 diphenyl-picrylhydrazyl activity increased drastically with exogenous ABA especially in Gladius, Drysdale and Kharchia. The genotypes, i.e., Gladius, Drysdale and Kharchia, also possessed increased activity of proline metabolizing enzymes, i.e., NADH-dependent glutamate dehydrogenase, pyrroline-5-carboxylate synthetase (1.5–2-fold) in response to ABA while proline dehydrogenase remained unresponsiveness to ABA indicating the ABA-dependent and ABA-independent regulation of enzymes, respectively, and depicting the role of ABA and proline in conferring drought and salinity tolerance.