Mitigation of the Adverse Effects of Salinity Stress on Walnut (Juglans regia L.) by Ascorbic Acid under In Vitro Conditions

Global food production and agricultural systems are challenged by salinity stress. There is evidence to suggest that ascorbic acid is beneficial for alleviating abiotic stress. Due to its ability to prevent free radical damage and oxidation, it has been found to have potent antioxidant properties. In the present study, we evaluated the potential of ascorbic acid (AsA) to mitigate salt stress in walnut plantlets cultivated under in vitro conditions. The present study investigated a comprehensive assessment of "Chandler" cultivar walnut under in vitro salinity stress conditions by varying NaCl concentrations (0, 30, 60, and 90 mM) and AsA levels (0 and 100 mg/L). Growth indexes, electrolyte leakage, proline content, malondialdehyde levels, total soluble sugars (TSS) content, and correlations between key walnut characteristics were analyzed. Shoot growth was adversely affected by salinity stress. However, The AsA application mitigated these effects, particularly as evidenced by the length and thickness of shoots. Despite salt stress, AsA treatment increased fresh and dry weights while total water content remained unchanged. AsA concentration and NaCl level significantly affected proline content, with the highest proline concentration found at 100 mg AsA in 90 mM NaCl. Electrolyte leakage, an indicator of salinity stress, was significantly reduced with AsA supplementation. Malondialdehyde (MDA) levels correlated with salinity stress, while AsA treatment reduced MDA levels. Moreover, salinity stress, in combination with AsA, significantly influenced TSS content. Correlation analysis highlighted associations among various walnut traits, providing insights into their interdependencies, which require further in-depth exploration for validation and mechanistic understanding.