The effect of sulfate and nano particles of iron and zinc on biomass, content and compositions of peppermint (Mentha piperita L.) essential oil under salt stress

In order to evaluate the effect of foliar application iron and zinc fertilizers in two forms of sulphate and nano particles on the essential oil content and composition of peppermint under salinity stress, an pot experiment as factorial based on completely randomized design with three replications was conducted. Treatments of the experiment were salinity stress in four levels (0, 40, 80, and 120 mM NaCl) and fertilizer spraying in five levels (control, 1500 mg/L of iron sulphate, 300 mg/L of nano iron, 1500 mg/L of zinc sulphate, and 300 mg/L of nano zinc). Plant samples were harvested at flowering stage and dried under shadow conditions. Application of zinc and iron fertilizers, especially as nano form, improved the biomass of the plant, and the best biomass of peppermint was observed in the treatment of iron nano-fertilizers application. The results showed that nano iron treatment under salinity conditions of 40 and 80 mM NaCl causes 13.96 and 25.13% increase in oil content compared to control plants. The highest amount of menthol (42.22%) was related to the 80 mM salinity and spraying of nano iron. The lowest amount of menthol (31.57%) was observed in the 120 mM salt stress and application of nano iron. According to results of this research, the salinity stress of 40 and 80 mM could have a positive effect on the menthol amount of peppermint oil. Generally, nano iron causes the improvement in the content and main compositions of essential oil and the biomass of peppermint under salinity stress.