Effects of Ascorbic and Oxalic Acids on Cucumber Seedling Growth and Quality Under Mildly Limey Soil Conditions

Limey soil/high soil pH is a common stressor for cucumbers which limits growth and development. Limey soil reduces iron (Fe) availability and leads to Fe chlorosis. Thus, the acquisition of Fe by plants is limited under lime-stress conditions. Plants which release organic acids can acquire Fe by adjusting the soil pH. Thus, exogenous organic acid treatment may alleviate limey soil stress. Furthermore, treatment with antioxidants may alleviate stress factors. In the present experiment, the effects of ascorbic (AsA) and oxalic acids (OA) on cucumber seedlings under lime-stress conditions were evaluated. Cucumber seedlings were grown under mildly limey soil conditions (pH = 8, CaCO₃ = 10%). The treatments Fe-EDDHA, 50 and 100 ppm ASA, and 3 and 10 mmol OA were applied at sowing and repeated weekly. Control plants did not receive Fe-EDDHA, AsA, and OA application. Seedlings were evaluated 30 days after sowing. AsA and OA treatments significantly affected cucumber seedlings. We evaluated the Dickson quality index parameter to compare seedling quality among the treatments, and results showed that Fe-EDDHA-treated seedlings had the highest value followed by 100 ppm AsA and 3 mmol OA. AsA and OA treatments increased the xylem conduit diameter compared to control and Fe-EDDHA treatments. The 3 mmol OA and 100 mmol AsA treatments triggered lignification. The highest cortical cell diameter was found in 100 ppm AsA followed by 3 mmol OA treatments. As a result, we suggest that AsA and OA can be used under high soil pH conditions.