Effect of salicylic acid on growth and phytochemical characteristics of Thymus daenensis under drought irrigation

Drought as the most important problem of agricultural development in Iran is one of the main obstacles in the production of agricultural products. Because the global approach to the production of medicinal plants is effective in improving the quantity and quality of the substance, today the use of salicylic acid as one of the plant hormones in increasing plant resistance to stresses such as drought has increased. In this study, the effect of foliar application of salicylic acid on the growth and phytochemical characteristics of Thymus daenensis Celak in low irrigation conditions was studied. The experiments were performed as a split plot in the form of a randomized complete block design with 3 replications in research field of Jihad University Medicinal Plants Research Institute located in Heljard, Karaj in 2017. The results showed that low irrigation stress significantly reduced plant height, number of lateral branches, yield of flowering branches, chlorophyll a and chlorophyll b, percentage of essential oil and essential oil constituents including thymol, carvacrol, paracetamol and beta-caryophylline. On the other hand, the use of salicylic acid reduced the negative effects of poor irrigation conditions. Also, the highest growth and phytochemical indices were observed in plants treated with salicylic acid, which indicates the role of elastores in stress relief. The results showed that salicylic acid by inducing stress tolerance moderated the damage caused by under irrigation stress in thyme and increased the growth rate of stressed plants. The findings of this study can be used to reduce plant damage in low water areas.