Effect of growth regulator salicylate on some physiological and biochemical parameters of peppermint (Mentha piperita L.) under drought stress

Peppermint (Mentha piperita L.), with numerous medicinal properties is one of the most important plants from Lamiaceae family. To investigate the effects of drought stress and salicylic acid on peppermint, an experiment was conducted as factorial based on completely randomized design with four replications in the greenhouse of Medicinal Plants Department, Faculty of Agriculture and Natural Resources, Arak University during 2017. Studied factors included drought stress (35%, 65%, 95% and 100% of field capacity) and salicylic acid (0, 50, 100 and 150 mg/l). Results showed that salicylic acid (concentration) improved most physiological traits including chlorophyll index, relative water content, chlorophyll a, b and total chlorophyll, carotenoids, phenol and flavonoid content, antioxidant capacity, ion leakage and malondialdehyde. The highest level of ionic leakage and malondialdehyde was obtained in combination treatments of 50 mg/L and 35% FC. Maximum total flavonoid content and antioxidant capacity were observed in the combination treatment of salicylic acid (150 mg/L) and 95% drought stress. Therefore, application of this growth regulator at the level of 100 mg/L can be helpful in alleviating drought stress in peppermint.