Evaluation of antioxidant enzymes activities, proline, soluble sugars, photosynthetic pigments and essential oils of Mentha piperita L. in response to foliar application of salicylic acid and manganese stress

This study was aimed to investigate the effects of manganese stress and salicylic acid treatments at three different times on activities of antioxidant enzymes, proline, soluble sugars, photosynthetic pigments and essential oils of Mentha piperita L. The research was conducted in a greenhouse at the University of Zabol in 2012-13. A factorial experiment was performed in a randomized complete block design with three replications. Plant samples were harvested at three times in 1, 3 and 5 days after spraying with Mn stress (500µM) and salicylic acid (1mM). The results indicated that manganese stress significantly affected APX and proline content of peppermint leaves during all three times. The content of proline and soluble sugars significantly increased in three times compared to the control treatment under salicylic acid and manganese stress. On the other hand, the Mn stress did not significantly decrease the photosynthetic pigments. In addition, essential oils increased with manganese stress and salicylic acid. This increase was much under salicylic acid treatment. According to the obtained results, increased APX enzyme and proline content were the physiological responses of peppermint against oxidative stress. It was also observed that salicylic acid acted as a powerful growth regulator and caused modification in manganese stress response in Mentha piperita.