Effects of different levels of salinity and drought stress on growth parameters and essential oil of lemon balm (Melissa officinalis L.)

In order to evaluate the effects of drought and salinity stresses on growth parameters and essential oil of lemon balm, two experiments with three replications in a randomized complete block design were applied. Five levels of salinity including zero, one, two, three and four dS/m of sodium chloride solution, and five drought stress treatments including 50, 62.5, 75, 87.5 and 100% as available water for plants were used. Parameters including morphological, dry matter, and essential oil percentage were measured in each experiment separately. Drought and salinity stress, with the exception of essential oil percentage, decreased all measured parameters and the effect of salinity stress was higher. The highest and lowest growth characteristics were achieved from the 100 and 50% available water treatments, and the maximum and minimum essential oil was achieved from 50 and 100% available water, respectively. In salinity experiment, growth parameters declined with increasing salinity. The level of salinity from zero to one dS/m increased the essential oil percentage. However, compared to control, treated plants showed higher essential oil percentages. Salinity and drought stresses reduced the growth parameters and essential oil percentage was somewhat increased.