Plant growth regulators affecting the physiological and yield responses of field barley genotypes to the drought and salinity stresses

More has yet to be investigated on the physiological and yield responses of barley genotypes to the double stresses of drought and salinity affected by plant growth regulators (PGR) as the objective of the present research. A split split-plot with three replicates testing the main treatments of control (70 mm evaporation from class A pan with salinity of 4 dsm⁻¹), salinity (70 mm evaporation from a class A pan with the salinity of 12 dSm⁻¹) and drought (120 mm evaporation from a class A pan with salinity of 4 dsm⁻¹) was conducted. The foliar application of water (control), zinc sulfate (5 gL⁻¹), potassium sulfate (5 gL⁻¹), salicylic acid (SA, 1.5 mM) and superoxide dismutase (SOD, 3 gL⁻¹) were used as the subplots. The sub-subplots consisted of the three barley genotypes of Goharan, Armaghan and Mehr. Plant relative water, proline and protein contents were higher in salty conditions than drought conditions. There were significant differences among the genotypes in terms of physiological and yield responses. The results indicate the positive effects of Zn, SA and SOD in salt stress and K in drought stress conditions. Different PGR including K (60.7%), followed by SA (61.0%), Zn (63.7%) and SOD (63.7%) resulted in the least EL. The highest grain yield in salt stress was resulted by K (6766 kgha⁻¹) and Zn (6690 kgha⁻¹) and in drought stress by Zn (5262 kgha⁻¹). The results indicate the positive effects of the tested PGR on the alleviation of the double stresses of salt and drought.