Impact of Foliar Application of Salicylic Acid and Jasmonic Acid on Biochemical and Agronomic Properties of Thymus vulgaris L. under Drought Stress

To investigate the effect of different levels of foliar applications of salicylic acid and jasmonic acid on biochemical characteristics and yield of Thymus vulgaris under drought stress conditions, a split factorial experiment has been performed based on randomized complete design with three replications during cropping seasons of 2019-2020 in Varamin region. The main factor include irrigation levels (60 (normal) and 110 mm of evaporation from the evaporation pan (drought stress)), with the sub factors being different levels of foliar application of salicylic acid (three level: control (zero), 25, and 50 mg l-1) and jasmonic acid (three level: control (zero), one, and two mg l-1). The effect of irrigation× foliar application treatments has been significant for all studied traits at 1%. The highest plant height (38.2 cm), wet and dry weights (7112.3 and 1778.7 kg h-1), percentage of secondary metabolites (essential oil 0.28 and thymol 60.9%), and concentrations of salicylic and jasmonic acid of leaves and the lowest activity of antioxidant enzymes (SOD, CAT and GPX) of thyme are observed in normal irrigation with 50 and 2 mg -1 salicylic and jasmonic acid treatment. Thus, external use of salicylic and jasmonic acid (50 and 2 mg -1) in drought stress conditions can be considered in improving related traits of yield and increasing the production of thyme.