EFFECTS OF HPS SUPPLEMENTAL LIGHTING AND SOIL-WATER LEVELS ON GROWTH,ESSENTIAL OIL CONTENT AND COMPOSITION OF 2 THYME (THYMUS-VULGARIS L) CLONAL SELECTIONS

The growth, essential oil content and composition of two clonally sele cted Thymus vulgaris plants were each significantly affected by two li ght regimes (LR) and three different soil water levels (SWL). The high est dry matter accumulation was achieved from plants grown under suppl emental light (SL) at 90% SWL. The leaf area increased linearly from 9 59 cm(2) to 1635 cm(2) for Selection 1 and from 543 cm(2) to 1322 cm(2 ) for Selection 2 under natural light and from 1180 cm(2) to 3512 cm(2 ) for Selection 1 and from 958 to 2821 cm(2) for Selection 2 under sup plemental light, respectively, for plants grown under 50 to 90% SWL. T he coefficient of correlation between shoot yield and leaf area was hi ghly significant (r(2) = 0.96). However, maximum essential oil content and yield per plant were recorded at 70% SWL for Selection 1 grown un der SL. There were significant shifts in the content of phenols, parti cularly in monoterpene hydrocarbons in the essential oil, due to the d ifferences in LR and SWL. The major constituent of the essential oil, thymol, accounted for the shift from about 48.6% to 85.5% for Selectio n 1 and the shift from 47.2% to 68.9% for Selection 2, depending on th e treatment levels. Our data showed a maximum level of 85.5% thymol ac cumulation in the essential oil of Selection 1 grown at 70% SWL under SL. We established that both selections under investigation belonged t o the thymol chemotype.