Document Type: Research Paper
Department of Agronomy and Plant Breeding, College of Agriculture, Isfahan University of Technology, 84156-83111, Isfahan, Iran.
Research Institute of Forests and Rangelands, P.O. Box 13185-116, Tehran, Iran.
Thymus daenensis is a medicinal plant endemic to semi-arid regions of Iran. A
field experiment using a randomized complete block design with four replications
was conducted to evaluate the effect of 20, 50 and 80% soil water depletion on
morpho-physiological traits, essential oil content and composition and water use
efficiency of T. daenensis during 2010-2011. Water stress reduced growth, herbage
production, chlorophyll and carotenoid content, while increased proline, K+,
essential oil content and irrigation water use efficiency based on essential oil yield
(IWUEeso). Thymol was the highest essential oil composition (63.3-73.5%)
followed by carvacrol (3.6-16.0%), ρ-cymene (3.8-7.4%), γ-terpinene (3.3-4.7%),
β-caryophyllene (2.8-4.0%) and borneol (1.4-3.4%), respectively. Thymol, ρ-cymene
and γ-terpinene were increased, while the other compositions decreased under
water stress. It is concluded that irrigation of T. daenensis based on 50% water
depletion should be an appropriate choice for first growing season and 80% water
depletion for the second growing season in semi-arid climatic conditions.