Seasonal and diurnal variability of essential oil and its components in Origanum onites L. grown in the ecological conditions of Çukurova

Turkish Oregano (Origanum onites L.) is one of the most commonly collected from nature as well as cultivated Origanum species in Turkey. In addition, Turkish Oregano is the most exported Origanum species from Turkey to the entire World. In this study, the seasonal and diurnal variability of the essential oil content in Origanum onites L. grown in the ecological conditions of Cukurova was studied from September 2000-August 2001. Monthly variability of the essential oil composition was also studied. The plant cuttings collected from the region were rooted in the greenhouse and transferred to the field in a split plot design with three replications. One year later from transplanting, fresh leaves from the top shoots were collected every week three times a day on Monday (at 08.00, 12.00 and 16.00 o'clock) throughout the year. The content and composition of the essential oil were analysed in fresh leaf samples by hydrodistillation. The essential oil content changed according to the seasons and the hour of day. The highest essential oil content (% 1.92) was found in the post-flowering -at the beginning of the seed formation period in the afternoon harvests during the second half of June (40th week). The essential oil composition varied monthly and the highest value (% 73.65) of carvacrol, the main component of the essential oil, was obtained from the flowering period in May