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Abstract

Drought stress remains a primary limitation to agricultural productivity, demanding targeted strategies to enhance plant resilience under limited water availability. This study investigated both individual and interactive effects of foliar-applied salicylic acid (SA) and gibberellic acid (GA) on morphological, physiological, and biochemical responses in two barley cultivars under optimal and restricted irrigation conditions. According to the results, the drought-tolerant barley variety exhibited a stronger response to foliar applications. The combined use of SA and GA demonstrated a synergistic effect. Application of SA and GA in combination enhanced the accumulation of key nutrients in the shoots under stress, increasing nitrogen, potassium, calcium, and copper contents from 1.60% to 1.97%, 2937 to 4269 mg kg⁻¹, 12,633 to 14,513 mg kg⁻¹, and 16.26 to 16.35 mg kg⁻¹, respectively. Furthermore, foliar application led to a reduction in DPPH levels by 18.4% in the Zeynel Ağa variety and by 22.5% in the Tarm-92 variety under drought stress. The combined foliar application of SA+GA markedly enhanced drought resilience in barley by improving nutrient uptake, sustaining growth, and mitigating oxidative stress, particularly under severe water deficit conditions. For practical implementation, 1.5 mM SA with 110 mg L⁻¹ GA at 15 and 30 days after emergence is recommended to achieve over 20% higher biomass and up to 35% reduction in oxidative damage under drought stress. Future studies should focus on elucidating the molecular mechanisms underlying SA–GA crosstalk and validating these synergistic effects across different barley genotypes under field conditions.

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