Glandular trichomes and essential oils of Helichrysum stoechas

The aerial organs of Helichrysum stoechas bear a dense woolly indumentum wi th two types of trichomes: nonglandular trichomes, extremely long, simple, uniseriate and multicellular; and biseriate, glandular trichomes with 10-14 cells. Glandular trichomes are abundant on the leaf abaxial surface, parti cularly on the intervein areas, on the inflorescence, at the receptacle on interfloret positions, on the corolla lobes, and on the ovary surface. Secr etion accumulates in a subcuticular space formed above the top of the upper tier of secretory cells and is released to the outside by cuticle rupture. The essential oils isolated from the flowers and from the leaves collected during the flowering period were obtained in a yield of 0.3% (v/w) and 0.8 % (v/w), respectively. The analyses performed by GC and GC-MS revealed that the monoterpene hydrocarbon fraction was dominant in both oils, attaining 93% and 98% of the total oils from the flowers and leaves, respectively. al pha -Pinene was the major component in both oils, amounting to 69% in the f lower oil and 78% in that of leaf.