Effect of water deficit on chemotypic and phenotypic attributes of some Thymus daenensis Celak. ecotypes from Iran

The growth and productivity of plants are affected by water as it may limit the cultivation of high water requirement plants. The use of plants with low water requirement and also high economical increment might be a good choice to overcome the limitation. Thymus daenensis Celak., an endemic medicinal plant in Iran, with high adaptation potential to drought habitats and also a high percentage of thymol has great importance in pharmaceutical, alimentary and hygienic industries. In this study, phenotypic and chemotypic attributes of eight Iranian T. daenensis ecotypes were assessed under water deficit conditions for two years. The experiment was run as a split-plot design based on RCBD with three replicates. To simulate water-limited conditions, three irrigation treatments were considered as normal irrigation, stop irrigation at beginning of flowering and at the vegetative stages. There was no significant effect of water stress on essential oil percentage. In the second year of cultivation (two-year-old plants), essential oil and dry matter were significantly affected by water stress and differentiated among the ecotypes. The carvacrol was the dominant component of essential oil in the ecotype of Zaghe while that was in others for thymol. The ecotype of Khanemirane-paien had the highest thymol (76.51%). Based on the morphological and phytochemical response of the species to water-limited conditions, T. daenensis can be introduced as a drought-tolerant plant and also as a good alternative for T. vulgaris (the cultivated species) because of the existing high quality and quantity of essential oil-producing genotypes.