external application of salicylic acid on physiological changes and yield of sweet pepper (capsicum annuum) under drought stress

Drought is a global crisis that poses a serious threat to agriculture, which reduces growth as well as yield of plants. salicylic acid (sa) is a phenolic growth regulator that has a protective role against stress conditions in the plants. the purpose of the present research was to investigate the impact of foliar spray of sa on the resistance of sweet pepper plants to drought. this experiment was performed as factorial in a completely randomized design, and treatments consisted of three levels of salicylic acid (0, 0.5 and 1mm) and three levels of drought stress (irrigation at 100, 60, and 30% of field capacity). findings suggested that drought reduced plant growth factors such as number and weight of pepper fruit, yield, plant height, photosynthetic pigments (chlorophyll a, b, and total) and carotenoids. it also increased activity rate of antioxidant enzymes such as catalase (cat), superoxide dismutase (sod), peroxidase (pod), soluble sugars, proline, anthocyanins, malondialdehyde (mda), and h2o2. sa treatment improved plant growth parameters, enhancing cat, sod, pod, chlorophyll a and b, proline contents, total chlorophyll, carotenoids, soluble carbohydrates, anthocyanins while decreasing the content of mda and h2o2. the study concludes that application of sa enhances the activity of the enzymes and decreases the harmful impacts of drought.