effects of salicylic acid application on morphological and physiological characteristics of cucumber seedling (cucumis sativus cv. super dominus) under drought stress

abstract application of salicylic acid (sa) as a phytohormone has been increased due to its role in plant tolerance to environmental 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. a factorial experiment based on completely randomized block design was conducted with 5 levels of sa (0, 0.25, 0.5, 0.75 and 1mm) and 3 levels of drought stress, daily irrigation (control) and irrigation period of 3 and 6 days with 3 replications. sa was sprayed on shoots of the seedlings at 3-4 leaf stage under drought stress. the results showed that sa increased leaf area and chlorophyll content by 60 and 15 percent, respectively. in contrast, application of (1mm) sa, decreased stomatal conductance by 96%. stem diameter, plantlet height, leaf number, shoot and root dry weight, increased by applying sa compared to control. seedling height, shoot dry weight and leaf area, decreased with increasing drought stress, whereas increased due sa application. interaction between sa application and drought stress showed no significant effects on stomatal conductance, stem diameter, root dry weight. as conclusion salicylic acid treatment increased mentioned physiological and growth parameters in cucumber seedlings.