Optimising cotton water productivity and antioxidant capacity via foliar abscisic acid: A dual-pathway regulation mechanism

Minimising non-productive water loss while sustaining yield is crucial for cotton cultivation in water-limited environments. Although abscisic acid (ABA) can induce stomatal closure, its synergistic regulation of antioxidant defense and water relations during the critical flowering and boll-setting stage remains poorly understood. This study aimed to elucidate whether foliar ABA application could enhance drought tolerance through a dual-pathway mechanism that concurrently improves antioxidant capacity and optimizes leaf water-use efficiency (WUEL), and to identify an optimal concentration that balances water conservation with yield stability. A two-year field experiment was conducted with foliar applications of ABA at low (AL, 50 μmol L⁻¹) and high (AH, 100 μmol L⁻¹) concentrations, alongside a distilled water control (CK). Physiological traits, endogenous hormones, antioxidant enzyme activities, and yield components were analysed. The AL treatment activated a beneficial dual-pathway response: it directly enhanced the antioxidant system, increasing superoxide dismutase, peroxidase, and catalase activities and proline content, while reducing malondialdehyde accumulation; concurrently, it orchestrated stomatal regulation, significantly lowering stomatal conductance and transpiration rate, which collectively improved WUEL. TOPSIS analysis ranked AL as the optimal treatment, as it enhanced water-saving and antioxidant capacity without significant yield loss, unlike the AH treatment. Thus, foliar application of 50 μmol L⁻¹ ABA improves drought resistance in cotton through a synergistic dual-pathway mechanism that coordinates antioxidant defence and stomatal regulation, thereby optimising water use and alleviating oxidative stress under drought conditions. Our findings provide a mechanistic basis and a practical strategy for implementing ABA in water-saving cotton production systems. • ABA application significantly enhances cotton water use efficiency and antioxidant enzyme activities. • ABA application reducing transpiration and oxidative damage. • Spraying ABA directly activates antioxidant systems and indirectly regulates hormones and photosynthesis. • Low concentration ABA improves physiological drought adaptation via stomatal control and ROS scavenging. • ABA application (50 μmol L −1 ) offering a practical water-saving strategy for arid-region cotton cultivation.