Effect of methyl jasmonate on some physiological and biochemical responses of peppermint (Mentha piperita L.) under salt stress

Salinity is a major environmental factor limiting plant growth and crop productivity. Therefore many studies had been done to minimize the stress effects caused by salinity in agriculture and plant physiology. To access the effect of methyl jasmonate and salinity on peppermint, experiment was conducted as factorial based on a randomized complete design (CRD) with three replications. In this research, methyl jasmonate sprayed at three levels including, 0 (without spraying or control treatment), 60 and 120 μM and also salt stress applied at four levels including 1.86, 5, 7.5 and 10 dS/m. The results showed that application of methyl jasmonate increased dry weights of roots and shoots, and thereby compensate weight loss induced by salt stress. Leaf chlorophyll (a, b and total chlorophylls) contents at salinity level of 5 dS/m significantly increased compared to control then decreased at higher levels of salinity. But application of 60 µM methyl jasmonate increased leaf chlorophyll a and total chlorophyll contents. Proline and soluble sugars contents in plant shoots increased under salt stress. Also, the concentration of 60 µM methyl jasmonate incremented shoot soluble sugars and proline contents in compared to controls.