The effect of salicylic acid on the activity of catalase and peroxidase enzymes and the content of phenol and flavonoid of (Scrophularia striata L.) under water deficit stress

Nowadays, the use of plant growth regulators has increased in improving the resistance of plants to drought stress. Therefore, in order to investigate the effect of salicylic acid on antioxidant enzymes activity and secondary metabolites of Scrophularia striata under water deficit stress, an experiment was conducted as the arrangement in a randomized complete block design with three replications in 2018 at the research greenhouse of Ilam University. Treatments included water deficit stress at four levels (100, 75, 50 and 25% of field capacity) and foliar application with salicylic acid at two levels (0 and 1.5 mM). The results showed that in 75 and 25% of field capacity with salicylic acid, malondialdehyde decreased by 17.81% and 34.04% compared with non-foliar application treatment, respectively. Also, the application of foliar spray reduced the amount of ion leakage under severe drought-stress conditions. Foliar application of salicylic acid increased total phenol content by 20.92, 33.00, 10.84 and 10.19% under 100, 75, 50 and 25%, field capacity, respectively. Under severe drought stress conditions, foliar spray with salicylic acid increased the amount of flavonol and flavonoid compared to the control. With the application of drought stress, catalase enzyme activity increased by 36.09 and 67.65%, respectively, compared to the absence of drought stress. The highest amount of peroxidase activity (1.07 units per mg protein per minute) under 25% of field capacity by application of salicylic acid was observed with the lowest amount of peroxidase activity under 100 per cent of field capacity, respectively. According to the mentioned content, it can be concluded that salicylic acid improved the growth and production of secondary metabolites (Phenol, flavonol and flavonoid) in Scrophularia striata under drought stress and non-stress conditions.