Effect of salicylic acid on salinity stress tolerance improvement of peppermint (Mentha piperita L.) in greenhouse

Peppermint (Mentha piperita L.) is one of the most important medicinal plants belonging to the Lamiaceae. In order to study the effect of different concentration of salicylic acid (SA) and salinity stress on peppermint morphological characteristics, an experiment was conducted as a factorial design based on completely randomized design with four replications. To investigate the interaction of salicylic acid and salinity stress, the following treatments were used: four NaCl concentrations of 0, 50,100 and 150 mmolL-1 and four salicylic acid 0, 0.1, 0.5 and 1 mmolL-1. The plants were grown in pots until they grow to harvesting stage. At the end of experiments, various traits such as height of plants, number of lateral branches, node and leaf, diameter of main shoot and shad of canopy, dry and fresh weight of shoot, fresh weight of root, length of internodes and root were measured. Plants that were under salinity stress level of 150 mmolL-1 died before end of experiments. The results showed that effects of salinity stress on number of lateral branches, number of node and leaf, shoot diameter, dry and fresh weight of shoot, length of internodes and root and fresh weight of root, SA on number of lateral branches and dry weight of shoot and their interaction on height of plants and shad of canopy were significant on peppermint. The highest suppress effect in salinity stress was obtained in 100 mmolL-1 NaCl and the effective in SA were 0.1 and 0.5 mmolL-1.