Osmotic Adjustment and Antioxidant Activity of Cucumber Seeds Pre-treated with Stress Attenuators and Subjected to Drought Stress During Germination

Drought stress limits cucumber germination and initial growth. Decreases cucumber germination and initial growth cause uneven plant stands and decrease crop productivity. Identifying drought-tolerant cultivars and drought stress attenuators can improve cucumber germination and initial growth. Therefore, we evaluated the drought stress tolerance of cucumber cultivars and the action of drought-stress attenuators on cucumber germination, initial growth, osmotic adjustment, and antioxidant activity. The research was carried out in two stages. In the first one, we evaluated five levels of osmotic potential and seven cucumber cultivars. In the second stage, we evaluated two cultivars-one sensitive and one tolerant to drought stress-subjected to six combinations of osmotic potential and attenuator. The osmotic potential of - 0.4 MPa is critical for cucumber seedlings-the cultivars Compadre, Campeiro, Sliced Max, and Premio are sensitive, and cultivars Diplomat, Runner, and Safira are tolerant at the - 0.4 MPa level. Sensitive cultivar seeds treated with hydropriming, salicylic acid, and hydrogen peroxide showed better growth, osmotic adjustment, and higher antioxidant activity than seeds not treated under drought stress. Gibberellic acid was beneficial only in the drought-stress tolerant cultivar and can increase the vigor of drought-tolerant cultivars. Our results reveal that Diplomat, Runner, and Safira cucumber cultivars are drought-tolerant and that hydropriming, salicylic acid, and hydrogen peroxide improve the tolerance of drought-sensitive cucumber cultivars.