Effect of Salinity and Salicylic Acid on Some Morphological, Biochemical Responses and Essential Oil Content of Peppermint (Mentha piperita L.)

Due to the role of salicylic acid in resistance to environmental stresses, this study was conducted at Ferdowsi University of Mashhad to evaluate the effect of this compound under saline condition on peppermint. In a pot experiment, the effect of salicylic acid at five concentrations (0, 5, 10, 50, 100 ppm) and salinity (sodium chloride) at three concentrations (0, 75, 125 mM), in a factorial experiment based on Completely Randomized Design with 15 treatments and three replications was evaluated. The simple effect of salinity showed that with increasing salinity, anthocyanin content and antioxidant capacity increased. This was while the number of days to flowering, plant height, number of lateral branches, leaf area, aerial part dry weight, and leaf to stem ratio decreased significantly. The simple effect of salinity also reduced the percentage and yield of essential oil. Significant interaction was observed between different concentrations of salicylic acid and salinity in terms of the effect on the number of lateral branches, dry weight of underground and aerial part, root to shoot ratio and percentage of essential oil. Also, the simple effect of salicylic acid treatment on delay flowering and reduction of plant height was significant. Salicylic acid treatment reduced the percentage of essential oil. However, this treatment was able to prevent a reduction in essential oil yield significantly. Therefore, salicylic acid treatment was able to reduce the possible negative effects of salinity stress.