Effects of salicylic acid on morphological and physiological characteristics of cucumber seedling (Cucumis sativus cv. Super Dominus) under drought stress

Application of Salicylic acid (SA) as a phytohormone has been increased due to resistance to stresses such as drought. The main goal of this experiment was to evaluate the effects of SA on morphological and physiological characteristics of cucumber seedlings under drought stress. For this purpose a factorial trial based on completely randomized design was conducted with 5 levels of SA (0 (control), 0.25, 0.5, 0.75 and 1 mM) and 2 levels of drought stress, daily irrigation (control) and stopping irrigation for 6 days with 3 replications. SA was used as seed soaking for 24 hr. Drought stress was also applied in 3-4 leave stage. The results showed that SA increased chlorophyll index and leaf area by 27 and 139 percent in comparison to control, respectively. In contrast, stomatal conductance and electrolyte leakage decreased with SA application. Use of SA increased stem diameter, height, leaf number, shoot and root dry weight and biomass by 31, 65, 60, 100, 180 and 96 percent in comparison to control, respectively. Leaf number, leaf area and shoot dry weight decreased under drought stress, while increased with SA application. The interactions between SA concentrations and drought stress for the measured traits such as chlorophyll index, stomatal conductance, stem diameter, height, root dry weight and biomass, was not statistically significant.