EFFECTS OF WATER-SUPPLY AND LIGHT-INTENSITY ON GROWTH AND ESSENTIAL OIL OF 2 THYMUS-VULGARIS SELECTIONS

The effects of three different soil water levels (SWL) and two light r egimes (LR), on two clonally selected T. vulgaris plants were investig ated under greenhouse conditions. The plants were harvested 135 days a fter the treatment and the leaf drug was subjected to a two hours stea m distillation using a Clevenger-type apparatus. The essential oil was analyzed by gas chromatography. The growth, essential oil content, co mposition, and yield/plant improved under supplemental lighting. The h ighest dry matter accumulation was achieved from plants grown at 90 % SWL under supplemental light (SL). The coefficient of determination be tween shoot yield and leaf area was highly significant (r(2) = 0.96). However, maximum essential oil content and yield per plant was recorde d at 70 % SWL for the two selections grown under supplemental lighting . There were great differences in the content of phenols and monoterpe ne hydrocarbons in the essential oil, due to the differences in SWL an d LR. Thymol content in the essential oil accounted for about 48.6 % t o 85.5 % for ''Selection 1'' and 47.2 % to 68.9 % for ''Selection 2'', depending upon the treatment levels. Our data showed a maximum level of 85.5 % thymol accumulation in the essential oil in ''Selection 1'' grown at 70 % SWL under SL. We established that both selections under the investigation belonged to the thymol chemotype.