Background: TThymus plants are well-known medicinal plants and it is believed that the pharmaceutical and therapeutical properties of these plants are related to their essential oils. The quality and quantity of the essential oils, as a secondary metabolite of an aromatic plant, are directly related to the physiological state of the plant. The role of jasmonates in the plant as signal molecules in mediation and up-regulation of plant defense and secondary metabolism processes is well recognized. Objective: With the aim of increasing the performance and stimulating secondary metabolites, this study evaluates the influence of the foliar application of MJ on essential oil content and composition of three different Thymus species, whether as an elicitor or an activator Method: The experiment was arranged in a randomized block design with MJ treatments in four levels (0, 30, 60, 100 mM) and three replications Results: Compared to the control, the essential oil content of all three species increased in all treatment levels. However, the changes in essential oil composition were different. Under MJ treatments, the amount of sesquiterpenes (especially caryophyllene oxide) increased in T. daenensis and T. fedtschenkoi. In addition, the amount of thymol in T. daenensis, thymol, and γ-terpinene in T. vulgaris increased, whereas carvacrol methyl ether in T. daenensis and p-cymene in T. vulgaris decreased. Conclusion: IIt seems the type of plant species has a specific role in determining the response. There were no interpretable changes between treatment levels.
