Evaluation of the effect of salicylic acid on morphological and physiological traits and essential oil of (Mentha piperita L.) under salinity stress

In order to investigate the effect of salicylic acid foliar application on the vegetative and physiological traits and the amount of essential oil of peppermint plant (Mentha piperita L.) under salinity stress conditions, a factorial experiment was conducted based on a completely randomized design in three replications in a greenhouse located in the north of Iran. The treatments included Foliar spraying of salicylic acid (zero, 50 and 100 mg/l) and salinity stress (zero, 50, 100 and 150 mg/l of sodium chloride) were the salinity stress at the six-leaf stage twice a week in the form of irrigation and foliar spraying of salicylic acid. It was applied in three stages of the four-leaf stage at a time interval of 10 days. The results showed that all the evaluated traits were significant at the level of 1 and 5%, increasing the salinity steress reduced all the evaluated traits except proline and salicylic acid foliar application had a positive effect on improving these traits under stress conditions. Fresh and dry weight of shoots and roots, plant height, total chlorophyll and essential oil percentage in salicylic acid treatment 100 mg/l and control salinity level and maximum root length in salicylic acid treatment 100 mg/l and the salinity level of 50 mg/l were obtained. Also, the highest content of phenol and flavonoids was observed in the treatment of salicylic acid 50 mg/l and the salinity level of 50 mg/l, and in the treatment of salicylic acid 100 mg/l and the salinity level of 150 mg/l the highest proline was observed. Therefore, according to the results of the present study, foliar application of salicylic acid at a concentration of 100 mg/l can be recommended to reduce the negative effects of salinity stress on peppermint.