Effects of methyl jasmonate and salt stress on physiological and phytochemical characteristics of peppermint (Mentha piperita L.)

Jasmonates are key signaling compounds in plant responses to biotic and abiotic stresses as well as in development. We studied the role of methyl jasmonate (MeJA) in alleviating NaCl-induced salt stress in Mentha piperita L. through evaluating its growth, mineral and phenolics contents, essential oil (EO) quantity and quality. Accordingly, plants were exposed to the NaCl concentrations of 1.86 (control), 5, 75 and 10 dS/m for two weeks, 24 h after foliar application of 0, 60 and 120 µM MeJA. The results showed that salt stress decreased fresh and dry weights of aerial parts and concentrations of potassium (K), calcium (Ca2), magnesium (Mg2), K Na ratio and phenolic compounds, while sodium (Na) content increased significantly under salt stress. Also, EO yield increased with the increase of salinity concentration then decreased at the salinity concentration of 10 dS/m. However, exogenous application of MeJA enhanced the contents of K, Ca2, Mg2, K Na ratio and phenolics, while Na content in salt stressed plants declined. In addition, pretreatment with 60 µM MeJA improved the growth and EO yield. The highest values of menthone and menthol were obtained at the salinity concentration of 7.5 dS/m and concentrations of 60 and 120 µM MeJA. In summary, our results indicated that application of MeJA could reduce the adverse of salinity stress in M. piperita.