The effect of different harvesting stages on aerial parts yield, essential oil percentage and main components of Thymus daenensis Celak.

In order to study the effect of different harvesting stages on aerial yield, essential oil percentage and essential oil components in Thymus daenensis Celak., an experiment was conducted in Esfahan as a randomized complete blocks design with 3 replications during 2007- 2009 and the best harvest time for maximum aerial yield, essential oil yield and amount of thymol were investigated. Aerial parts of the plants were harvested at four stages including: beginning of flowering, 50% flowering, full flowering and fruit set and were dried in the shade. The results showed that different harvesting stages had significant effects on all evaluated traits. According to the results of mean comparisons, the highest aerial dry weight and essential oil yield occurred at full flowering stage and the highest essential oil percentage was recorded at 50% flowering. Interaction effect of year and different harvesting stages showed that the highest aerial dry weight and essential oil yield (3083 and 68.61 kg/ha respectively) were recorded at full flowering stage in the second year. In both years, the highest amount of essential oil percentage was observed at 50% flowering and the year had no significant effect on this trait. The essential oil was mainly consisted of six components, among them thymol was dominant at four harvesting stages. The highest amount of thymol was obtained from beginning of flowering stage (85.9%) which had significant difference compared to other stages. The second dominant component was carvacrol at fruit set which showed significant difference compared to other stages. The maximum amount of P-cymene, 1,8-cineole and δ-terpinene were recorded at 50% flowering stage (3.4, 1.4 and 1.8% respectively). Borneole was also dominant (2.53%) at fruit set. In conclusion, full flowering stage was identified as the best time for harvesting of T. daenensis to achieve the maximum aerial yield, essential oil and thymol yield.