The responses of potted saplings of chandler and fernor walnut cultivars under water stress

The study was carried out in 2020 to determine the responses of Chandler and Fernor walnut saplings grafted on Juglans regia rootstock under water stress. Three different irrigation levels were applied to one-year-old potted saplings in a greenhouse for three months. These; full irrigation (100% of the pot field capacity (PFC)) and two deficit irrigation treatments (50% of the PFC and 25% of the PFC). Deficient water amount was given every 5 days. After every 15 days, the physiological and biochemical responses of the plants were determined in leaves. İn the study; sapling height, trunk diameter, root dry matter ratio, the leaf area, SPAD values, leaf water potential, stomatal conductivity and membrane stability index values, malondialdehyde (MDA), total phenolics, total flavonoids, total protein, total proline and the activities of antioxidant enzyme (superoxide dismutase (SOD), peroxidase (POD), ascorbate peroxidase (APX), catalase (CAT)) were determined. The application of 25% PFC significantly decreased the leaf area and leaf SPAD value compared to the control (100% PFC) application. As the severity of water stress increased, the MDA content, total phenolic, total flavonoids, total protein, total proline, antioxidant enzyme activities increased linearly, while the stomatal conductance decreased linearly. There was no significant difference between water stress applications in terms of membrane stability index values. As a result, it has been determined that the saplings of Chandler and Fernor cultivars exhibit a possible tolerance by developing certain defense mechanisms against water stress (by decreasing leaf water potential and stomatal conductivity; by increasing osmolytes such as proline, increasing the activity of antioxidant systems). It has been observed that there are different regulatory mechanisms, different tendencies of antioxidant compounds and enzymes for both the cultivars in response to oxidative damage. While the total protein, the total phenolic, POD and CAT activities occur at higher levels in Chandler cultivar; the total proline, the total flavonoid, SOD and APX activities were higher in Fernor cultivar.