The effects of salinity stress on morphological characteristics, mineral nutrient accumulation and essential oil yield and composition in Mentha canadensis L.

Mint (Mentha canadensis L.) is one of the most important plants to produce essential oil. The aim of this study was to investigate the effects of NaCl salinity on the morphological characteristics, mineral content and essential oil yield and composition of M. canadensis L. through cultivating rhizome segments in sand tanks irrigated with full-strength Hoagland nutrient solution containing different concentrations of NaCl (0, 50, 100, 150 mM). Meanwhile fresh and dry weights of three plant parts (leaves, stems and roots) were measured, the morphological characteristics including plant heights, root and branch length, stem diameter and number of branches were also examined. The mineral element contents were determined using an ICP atomic emission spectrometer. The essential oils were extracted and analyzed by GC and GC-MS. The result showed that biomass and water content of all plant parts were significantly reduced at even the lowest (50 mM) salt concentration treatment, of which, the reduce in aerial parts was more remarkable than that in roots. The salinity treatment also reduced plant height, root and branch length, number of branches and nodes. Na+ accumulation increased significantly in all three plant parts, the Na+/K+ ratio increased with increasing concentration of NaCl, and the highest was found in the leaves, followed by stems, then roots. The essential oil content was strongly reduced in salt-treated plants. Salinity had no effect on the content of oxygenated monoterpenes but it increased the menthone and pulegone contents, while a decreased concentration of menthol under saline condition was observed.