Effect of salicylic acid and putrescine on some physiological characters and essential oil of peppermint (Mentha piperita L.)

Peppermint (Mentha piperita L.) is a medicinal and aromatic plant belonging to Lamiaceae family that its essential oil is used in differernt pharmaceutical industries. In order to study the effect salicylic acid and putrescine on some physiological characters and essential oil of peppermint, an experiment was conducted as a factorial using treatments of salicylic acid (0, 0.1, 1 mM) and putrescine (0, 0.1, 1 mM) in randomized complete block design with three replications. All traits were evaluated in two harvests. Results showed that all traits (except the ratio of chlorophyll a/b, carotenoid, anthocyanin and soluble solids) in the first harvest were significantly higher than the second harvest. Application of different concentrations of salicylic acid led to decrease the amount of chlorophyll a, total chlorophyll, carotenoid and anthocyanin. Also the treatments of 0.1 and 1 mM salicylic acid increased shoot essential oil perecentage in comparison to no consumption 16.45% and 32.91% and leaf oil perecentage in comparison to control 2.54% and 29.66%, respectively. With increasing the putrescine, yield per unit area, chlorophyll a, total chlorophyll, carotenoid and leaf essential oil perecentage were increased. Applying of 1mM putrescine increased the amount of anthocyanin and leaf essential oil perecentage in comparison to control 33.91% and 21.36%, respectively. In addition to, the interaction effect of two studied factors on fresh yield per unit area, chlorophyll a and b, total chlorophyll, carotenoid, anthocyanin, soluble solids and interaction effect of three factors on dry yield per unit, careatotal and soluble solids were significant.