What are Trichomes?
capitate stalked trichome photo by: Eirik
Although cannabis resin glands called trichomes are structurally diverse, they come in three basic varieties:
Bulbous:
The
bulbous type is the smallest (15-30 micron). From one to four cells make up the "foot" and "stalk," and one to four cells make up the "head" of the gland. Head cells secrete a resin - presumably cannabinoids, and related compounds which accumulate between the head cells and the cuticle. When the gland matures, a nipple-like protrusion may form on the membrane from the pressure of the accumulating resin. The bulbous glands are found scattered about the surfaces of the above-ground plant parts.
Capitate-Sessile:
The second type of gland is much larger & is more numerous than the bulbous glands. They are called capitate, which means having a globular-shaped head. On immature plants, the heads lie flush, appearing not to have a stalk and are called
capitate sessile. They actually have a stalk that is one cell high, although it may not be visible beneath the globular head. The head is composed of usually eight, but up to 16 cells, that form a convex rosette. These cells secrete cannabinoids, and related compounds which accumulate between the rosette and it's outer membrane. This gives it a spherical shape. The gland measures from 25 to 100 micron across.
Capitate-Stalked:
Cannabinoids are most abundant in the
capitate-stalked gland which consists of a tier of secretory disc cells subtending a large non-cellular secretory cavity. During flowering the capitate glands that appear on the newly formed plant parts take on a third form. Some of the glands are raised to a height of 150 to 500 micron when their stalks elongate. These capitate-stalked glands appear during flowering and form their densest cover on the female flower bracts. They are also highly concentrated on the small leaves that accompany the flowers. The male flowers have stalked glands on the sepals, but they are smaller and less concentrated than on the female bracts. Male flowers form a row of very large capitate glands along the opposite sides of anthers.
photo by: Proof_of_the_pudding
photo by: Proof_of_the_pudding
The figures above denote capitate-stalked trichomes with green arrows, the bulbous trichomes with yellow arrows & the red arrows mark the capitate-sessile trichomes. Cyan arrows denote cystolith hairs.
Life inside a capitate-stalked trichome
image by: Snaps_Provolone
Disc cells, attached to leaf or bract by stipe cells
(RED) & basal cells
(GREEN), release fibrillar wall matrix into secretory cavity where it contributes to thickening of subcuticular wall during enlargement of secretory cavity. Plastids
(ORANGE) in disc cells produce secretions called lipoplasts which synthesize quantities of lipophilic substances that accumulate outside the plasma membrane, migrating into the endoplasmic reticular cytoplasm and through the plasma membrane and cell wall into the secretory cavity where they form vesicles
(BLUE) in the secretory cavity. Vesicles in contact with the subcuticular wall release contents that contribute to the growth of the cuticle during the enlargement of the secretory cavity. THC occurs in the walls, fibrillar matrix & other contents surrounding the vesicles, but not in the vesicles. Trace amounts of THC is present in the disc cells.