What Are Cannabis Trichomes and Resin Glands?

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Cannabis trichomes appear as sticky translucent whitish to amber resin on ripening cannabis flowers, leaves and branches. The majority of cannabinoids, including THC and CBD, are found in the resin glands with a spheric head on top of a short post or column. Typically, more intense the densely of capitate-stalked resin glands will yield in more THC and CBD. The cannabinoid-rich resin can be consumed as dried and cured flowers, or separated from the plant and made into concentrates, including rosin, dry-sieve hash,  BHO, shatter, etc.

This image is spectacular, you can actually see the cells and the pink secretion where the largest concentrations of THC and CBD are found in the translucent capitate-stalked resin glands.

Cannabinoid-rich resin glands and other trichomes include, bulbous, capitate-sessile, capitate-stalked and nonglandular trichomes. The capitate-stalked glands that cover flowers, seed bracts and small bud-leaves, are the most important to cannabis gardeners. These resin glands account for most of the CBD and THC contained in the plant. Bulbous and sessile resin glands on the surfaces of all flowers, leaves, stalks and branches, along with a small amount of cannabinoids present in interior cells, account for the balance. These large, capitate-stalked resin glands are our main focus.

Capitate-stalked resin glands become clearly visible during flowering with the naked eye. Use a 10-30X handheld lens to distinguish different types resin glands.  Visual inspection can be used to examine capitate-stalked resin glands closely to determine peak CBD and THC content. Check flowers every day starting the sixth week of flowering. Check several flowers from different plants to ensure the maximum amount of capitate-stalked resin glands are ripe for harvest. We will take a close look at trichomes and resin glands in this blog.

See “When Do I Harvest My Cannabis Plants” for a complete guide. ??Blog to be written. Name may change

Capitate-stalked resin glands become more fragile as they mature. The union of the bulbous top on top of the little post is the weakest point. Friction from rough handling or fondling flowers can knock the top off of the post, which lowers potency and speeds decomposition.

Trichomes are believed to have evolved as a defense mechanism for plants. Many plants contain a protective layer of trichomes against diseases and pests that prevents them from reaching and penetrating the surface of the plant.  Some trichomes can inhibit the growth of a few types of fungus. The chemicals in the trichomes make cannabis less appetizing to animals by secreting a bitter substance and distasteful aroma.

The protective trichomes also help insulate plants from temperature extremes, excessive water loss caused by wind and low humidity and protect from excessive moisture. They also form a natural “sunscreen” to shield against ultraviolet light rays.

Trichomes are little appendages that grow on all plants. For example, root hairs and foliage hairs are trichomes. Trichomes differ immensely. Some are glandular, with a stalk and glandular head. Others are nonglandular, elongated and tapered. Using the term “trichome” to describe “capitate-stalked resin glands” that contain the bulk of desirable cannabinoids is only partially correct. It is similar to describing all roses as “flowers.” All roses are flowers but not all flowers are roses.

Nonglandular Trichomes

Sessile and Cystolith Trichomes

Most abundant on outdoor plants, sessile and cystolith trichomes are more common on some varieties than others. More of these trichomes form on plants when they harden-off and are moved from indoors to outdoors. The trichomes (glands) exude insecticidal and miticidal substances to gum up pests’ mouthparts and repel them, but they contain no useful cannabinoids.

Sessile and cystolith trichomes,AKA plant hairs, are common on many plants and do not produce cannabinoids. These trichomes have a pointed tip and are often long and hair like. The waxy protective trichomes are most common on leaf undersides, petioles and stems. They are trichomes with pointed tips that help protect cannabis from diseases and pests.

Bulbous Resin Glands

If you look closely at small leaves, you can see little balls of resin sticking directly to the foliage. Each of these balls has a “foot” that will grow as the glands grow and accumulate cannabinoids.

Bulbous resin glands are the smallest trichomes and barely visible with the naked eye, ranging in size from 15 to 30 micrometers. One to 4 cells constitute the “foot” and “stalk,” and 1 to 4 cells make up the “head” of the gland. Head cells secrete a resin, believed to be cannabinoid-rich, along with related compounds that accumulate between the head cells and the cuticle. A nipple-like bulge may form on the membrane from the pressure of built-up resin as these glands mature. Look for bulbous glands scattered about on foliage surfaces.

Capitate-sessile Resin Glands

Images like this show every detail of the capitate-stalked resin glands.

Capitate-sessile resin glandsdevelop before and during flowering growth. The bulb head measures from 25 to 100 micrometers across the globular-shaped head or bulb. The bulb appears to lie flat on young and immature plants. The stalk elongates and grows during flowering to transform the capitate-sessile gland into a capitate-stalked resin gland. As glands accumulate progressively more resin that concentrates between the stalk and the bulbous head.

Capitate-stalked Resin Glands

Capitate-stalked resin glands are covering this flower so completely that foliage is obscured.

Capitate-stalked resin glands (trichomes) develop and become visible with the naked eye when flowers form. Look for them on female flower bracts and new flower growth and surrounding foliage where they form heavily on the plant. The resin glands also tend to accumulate heavily on veins of lower leaf surfaces around flowers. They also accumulate on somewhat larger leaves and petioles. Cannabinoid-potent varieties typically contain higher concentrations of capitate-stalked resin glands. Use a 30X handheld microscope to see close up.

Capitate-stalked resin glands are full of chemical activity. This is where the majority of cannabinoids occur. Disc cells and principally the secretory cavity, of the gland perform a key role in the physiology of secondary products. In the above illustration, disc cells are shown attached to foliage by stipe cells (red) and basal cells (green). The plastid (orange) in disc cells secrete lipoplasts where they synthesize lipophilic substances that accumulate and ultimately migrate and form BLUE vesicles. THC occurs in the top of the capitate-stalked resin gland.

Capitate-stalked resin glands hold the bulk of CBD and THC. These resin glands consist of a stalk with a spherical, bulb-like head on top. They look like a post with a knob, ball or bulb at the top. They form mainly on flowers and small leaves. The highest concentration of cannabinoids is located at the base of the bulbous resin head.

Leaves and Male Cannabis Plants

Male plants and flowers have much lower concentrations of less cannabinoid-potent capitate-stalked resin glands than found on the females plants. Male plants are typically culled from the garden and destroyed so that they do not pollinate female flowers.

Older leaves contain few cannabinoids that are clearly visible on leaf surfaces. Leaves around flowers are much more densely populated with capitate-stalked resin glands rich in cannabinoids. Large and small leaves can be separated and dealt with separately. Cannabinoids can be separated from leaves using several different methods and solvents.

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