Changes in essential oil profile of Thymus daenensis Celak., Thymus fedtschenkoi Ronniger., and Thymus vulgaris L. under methyl jasmonate treatment
Background: Thymus plants are well-known medicinal plants and it is believed that the pharmaceutical and therapeutically properties of these plants are related to their essential oils. The quality and quantity of the essential oils, as a secondary metabolite of aromatic plant, is 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 evaluate the influence of 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, essential oil content of all three species increased in all treatment levels. However, the changes of 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: It seems the type of plant species has a specific role in determining the response. There were no interpretable changes between treatment levels.