بررسی روش کاربرد نیتروژن در شرایط نیمه خشک و معتدل سرد بر صفات رویشی و ترکیبهای اسانس گیاه دارویی آویشن (Thymus vulgaris L.)

Thyme (Thymus vulgaris L.) is an important plant of family Lamiaceae and its essential oil is famous among 10 essential oil of medicinal plant. In present study, effects of nitrogen application methods was evaluated at two moderate and semi arid zones for distinguishing the best nitrogen application method in each habitat considering the growth differentiation balance (GDB) for vegetative production and secondary metabolites. The experiment was conducted into a randomized complete blocks design with 3 replications in two regions Shahr e ray and Karadj in 2008. Treatments were included nitrogen application methods (no application as the control), 50 kg.ha-1 soil application and 50 kg.ha-1 foliar applications. Fresh samples of thyme plants were taken at two experimental farms and after drying in the shade, oil was extracted and the essence was analyzed by the GC apparatus. The results of independent and combined analyses showed that the foliar application of nitrogen at Karadj significantly increased plant height, percentage of thymol (2.74%) and thymol yield (19.5 kg.ha-1), dry shade yield (2498.2 kg.ha-1) and essential oil (38.9 lit.ha-1) as well. In contrast, the highest values for dry shade (2772.7 kg.ha-1), yield essential oil (19.1 lit.ha-1), yield and percentage of secondary metabolites i.e.)percentage of Thymol (1.2%) and thymol yield (7.72 kg.ha-1) percentage of P-cymene (0.68%) and P-cymene yield (7.62 kg.ha-1) and percentage of carvacrol (0.076%) and carvacrol yield (0.85 kg.ha-1) (measured under the soil application of nitrogen on the experimental filed of Shahr e Ray). Thymol and P-cymene were the representative compounds at two experimental locations. It was concluded that better adaptation of thyme plant under the moderate cool and high altitude in Karadj rather than the semi arid condition in Shahr e Ray was due to the faster establishment and increase of the number of branches. Foliar application of nitrogen in Karadj resulted in a kind of growth differential balance (GDB) and increased both vegetative production and thymol composition as the most important secondary metabolites of thyme. Declined humidity and warm wind, in the experimental farm of Shahr e Ray reduced nitrogen absorption through the leaf feeding.