Growth, oil and physiological parameters of three mint species grown under saline stress levels

Salinity stress is known to have a detrimental effect on mint plants. The aim of the present work was to investigate the possible effects of salinity stress on Mentha spicata, Mentha piperita and Mentha arvensis. Plants were exposed to salinity stress using different concentrations of NaCl (0, 50, 100, 150 mM). Under salinity stress, plant growth, oil yield, content and composition, as well as physiological parameters were adversely affected. Among the studied species, M. arvensis experienced the maximum loss in terms of oil percentage. Physiological characteristics and oil composition were significantly affected with intensification of salt stress. For instance, in M. spicata, with increasing salinity stress, piperitone oxide was decreased from 78.4 percent in control to 38.0 percent in 150 mM NaCl, whereas menthol was increased from 1.0 to 37.1 percent. Moreover, in M. piperita, menthone, isomenthone and limonene were all increased in low stress and then were decreased in high stress conditions. In M. arvensis, the major compound; menthol was not affected but the content of menthone increased. It could be concluded that the salinity stress is detrimental but might be useful and may be recommended as an appropriate approach in improving the oil quality or to producing specific compounds under mild or moderate stress.