|Description of Trichomes:
Glandular trichomes (peltate and bulbous); non-glandular trichomes (cystolith hairs).
Leaves of Humulus lupulus possess two types of glandular trichomes: peltate (lupulin) and bulbous. Peltate trichomes are built of a glandular head consisting of 30 to 72 cells, four stalk cells and four basal cells. The glandular head consists of a multi-cellular ring of cells that forms a cup-like structure that fills with a yellow resin containing large amounts of xanthohumol and other terpenophenolics. Bulbous trichomes consist of four (occasionally eight) head glandular cells, two stalk cells and two basal cells. The glandular trichomes in Humulus lupulus form at the base of the abaxial surface of bract-like leaves surrounding the female flower.
Leaves of Humulus lupulus also possess non-glandular trichomes -- cystolith hairs, which is a hard calcium carbonate structure at base of a hair.
Essential oil includes Myrcene, humulene and caryophyllene; bitter acids includes humulones and lupulones; prenylfalvonoids includes Xanthohumol and desmethylxanthohumol.
1) Jana Nagel, et al. (2008) EST analysis of hop glandular trichomes identifies an O-Methyltransferase that catalyzes the biosynthesis of xanthohumol. The Plant Cell 20:186-200.
2) M. Margarida Oliveira, M. Salomk S. Pais. (2008) Glandular trichomes of Humulus lupulus var. Brewer's Gold: Ontogeny and histochemical characterization of the secretion. Nordic Journal of Botany. 8(4): 349-359.