Effects of Ascorbic Acid and Calcium Nitrate on Morphological, Physiological, and Biochemical Responses of Cucumber (Cucumis sativus L.) Seedlings Under Salt Stress

This study was conducted to determine the effects of ascorbic acid (AA) and calcium nitrate (CN) applications on the morpho-physiological and biochemical characteristics of cucumber (Cucumis sativus L.) seedlings under salt stress conditions. The experiment was carried out in a controlled growth chamber, where “Beith Alpha” cucumber seedlings were grown under 150 mM NaCl-induced salt stress. From the two–true-leaf stage onward, AA (0.1 and 0.2 g L-1) and Ca(NO₃)₂ (1 and 2 g L-1) were applied as foliar sprays, either individually or in combination. The experiment was arranged in a completely randomized design with three replicates, including a non-saline control (K) and a salt-stressed control (Kp), comprising a total of eight treatment groups. The results showed that salt stress significantly reduced plant height, root length, biomass accumulation, and SPAD values, while increasing malondialdehyde (MDA) content, an indicator of lipid peroxidation, by approximately 3.5-fold. AA and CN applications alleviated these adverse effects in a dose- and parameter-dependent manner. Among the combined treatments, AA-1+CN-1 (0.1 g L-1 AA + 1 g L-1 Ca(NO₃)₂) resulted in the greatest increase in root length (88.7%) and provided the most effective antioxidant protection by maintaining MDA content close to control levels (0.26 nmol g-1). Among the single applications, 2 g L-1 Ca(NO₃)₂ (CN-2) showed the highest improvement in total fresh weight, dry weight, and leaf area. The effectiveness of AA was found to be dose-dependent, and the higher dose (0.2 g L-1) did not exhibit the expected growth-promoting effect. In conclusion, the combined foliar application of AA-1 and CN-1 is recommended to enhance root development and reduce oxidative damage in cucumber seedlings under salt stress, whereas CN-2 alone appears to be a more effective strategy when biomass and vegetative growth are the primary objectives.