Effects of silicon and nano-silicon on some morpho-physiological and phytochemical traits of peppermint (Mentha piperita L.) under salinity stress

Salinity is one of the most important abiotic environmental stresses which restricts the growth and production of plants. On the other hand, silicon (Si) is the second most abundant element in the soil and alleviates the biotic and abiotic stresses in the plants. For this purpose, a greenhouse experiment was conducted as a factorial in a completely randomized statistical design with three replications to investigate the effects of silicon and nano-silicon (50 and 100 mg l-1) on some morphophysiological and phytochemical properties of peppermint (Mentha piperita L.) under salinity stress at the different levels of sodium chloride (0, 50, and 100 mg l-1) in 2019. The results showed that the salinity stress significantly reduced the fresh and dry weight of aerial parts and root, and chlorophyll, total phenol, and protein contents. The activity of superoxide dismutase and peroxidase enzymes and essential oil percentage differed at the different salinity levels. The amount of proline also increased significantly due to the sodium chloride treatment of 100 mg l-1. The plants treatment with the different levels of silicon and nano-silicon reduced the negative effects of salinity stress on the evaluated indices. The nano-silicon treatment of 100 mg l-1 showed the highest inhibition of salinity stress effects on the growth indices, antioxidant enzymes activity, and essential oil percentage. Therefore, according to the results of this research, the foliar application of silicon and nano-silicon could be recommended to reduce the negative effects of salinity stress on peppermint.