amelioration of drought stress damages by 5-aminolevulinic acid application in sweet pepper plants (capsicum annuum l. cv. red bell pepper)

drought, withnegative impacts on plant growth and development, isa major abiotic stress. in order to decreasing drought stress injuries and recognizing red peppers tolerance physiology against drought stress in greenhouse conditions, an experiment with three levels of drought stress (irrigation at 100, 60 and 30% of field capacity) and four concentrations of 5-aminolevolinic acid ((ala; 0, 0.25, 0.5, and 1 mm)with four replications in an experimental was 3×4 factorial experiments in a randomized completely design was conducted in greenhouse of agricultural faculty of ilam university. in the end of experiments, parameters such as ascorbate peroxidase activity, total antioxidant activity, malondialdehyde content, ascorbic acid, relative water content, plant height and number of lateral buds was evaluated. the results showed that with increasing drought stress severity the growth parameters decreased significantly but ascorbate peroxidase activities, total antioxidant capacity, malondialdehyde and ascorbic acid content increased. foliar application of aha reduced malondialdehyde content and improved other evaluated traits. ala protected cell membranes by reducing malondialdehyde content and lipid peroxidation. in addition, ala with increasing ascorbate peroxidase activity, total antioxidant capacity and ascorbic acid contents in plants improved physiological traits and drought stress resistance.