Quantitative analyses of the essential oils in intact glandular trichomes isolated
from thyme cotyledons by the use of an adhesive tape and a glass capillary tube showed
that the content of thymol per cotyledon was approximately equal to the sum total
of thymol in peltate glandular trichomes (PGTs) and capitate glandular trichomes (CGTs).
The amounts of thymol and γ-terpinene in PGTs increased with time until 9 days after
germination, when these monoterpenes were exclusively found in PGTs. The radioactivity
of [U-14
C]-sucrose administered to cotyledonal segments was incorporated into γ-terpinene and
thymol most actively by the peripheral part abundant in PGTs, whereas the incorporation
was markedly decreased by a partial removal of PGTs from cotyledons. The cell-free
extract of isolated PGTs was capable of cyclizing [14
C]-geranyl pyrophosphate into γ-terpinene, but this enzymatic reaction failed when
PGTs were removed from cotyledons. These results indicate that the biosynthesis and
accumulation of monoterpenes in thyme seedlings take place primarily in PGTs.
Thymus vulgaris
- Labiatae - glandular trichome - essential oil - thymol - γ-terpinene - biosynthesis
