Exogenous ascorbic acid enhances drought tolerance in sour orange through integrated physiological and antioxidant mechanisms.

Drought stress significantly reduces citrus yield by disrupting photosynthesis, affecting water balance, and damaging cellular structure. This research examined the effectiveness of exogenous Ascorbic Acid (AsA) in alleviating drought-related damage in sour orange (Citrus aurantium). Plants were subjected to drought stress (water withholding for 14 days) and foliar sprayed with AsA at concentrations of 0, 125, or 250 mg L- 1. Compared to the control, drought severely reduced photosynthetic pigments and relative water content (RWC), while increasing markers of oxidative damage, including malondialdehyde and markers of membrane damage. Application of AsA, particularly at 250 mg L-1 effectively counteracted these effects, markedly enhancing chlorophyll and carotenoid levels, improving water status and significantly boosting the activity of key antioxidant enzymes (catalase and peroxidase), AsA treatment also promoted the accumulation of osmoprotectants (proline, soluble sugars) and total protein. Correlation analysis revealed strong associations among these parameters, suggesting that AsA may strengthen the positive relationships between antioxidant defense, osmotic adjustment, and membrane stability, which could reflect an integrated physiological response to drought. These results highlight AsA as a cost-effective approach to improve drought resilience in citrus, with potential benefits for sustainable horticulture in water limited environments.