effect of foliar application of jasmonic acid (ja) on essential oil yield and its compositions of thymus daenensis celak

background & aim: recent researches have been done on effects of plant growth regulators (pgr) on growth and production of different crops whose results indicate the effectiveness of most of these hormones on qualitative and quantitative growth of herbs. the application of regulators and inhibitors of growth on herbs may, in addition to growth, also lead to secondary metabolites stimulation. jasmonic acid (ja) and its volatile methyl ester (mj) collectively termed jasmonates, are regarded as endogenous regulators that play important roles in regulating stress responses, plant growth and development. this study was carried out to survey the effect of spraying of jasmonic acid (ja) on t. daenensis celak in shahrekord, southwest iran at 2010-2011. experimental: a pot experiment was conducted in a crd with six treatments and seven replications. the treatments including i: distilled water (control), ii: distilled water and solution (acetone), iii-vi: ja in various concentrations (50, 100, 200 and 400 µm). the treatments were applied before flowering stage. the aerial parts were characterized by clevenger approach and gas chromatography–mass spectrometry. results & discussion: results of analysis of variance of the experiment showed that different levels of the foliar application of ja do have significant impacts on chemical constitutes in the essential oil of t. daenensis. various concentrations of foliar application of ja caused decrease or increase some of secondary metabolites in essential oil. in comparison with other treatments, there is a significant difference between amount of thymol and carvacrol, as two main compounds in essential oil of t. daenensis, having 100 µm ja. the application of acetone solvent with distilled water also caused the increase in some of constitutes of the essential oil. industrial and practical recommendations: in metabolic cultivation, for producing a special metabolite, the main agronomic and processing management should be regarded in order to increase the rate of essence and metabolites. finally, some of secondary metabolite production in thymus daenensis celak could be partially changed by supplementation of different elicitors such as ja.