Resin Gland Anatomy and Development

As resin gland development commences, the medically important cannabinoids and the associated terpenes begin to appear. Although the cannabinoids are odorless, terpenes are the primary aromatic principles found in the essential oil of Cannabis (9,10). Most interesting economically and medically are the cannabinoid-rich terpenoid secretions of the head cells of glandular hairs densely distributed across the myriad surfaces of the female flowers. Male plants are of no consequence in medicine production because they develop few glandular trichomes and consequently produce few cannabinoids or terpenes. Solitary resin glands most often form at the tips of slender stalks that form as extensions of the plant surface and glisten in the light. The cluster of one to two dozen glandular head cells atop each stalk secretes aromatic terpene-containing resins with very high percentages of cannabinoids (>80%) that collects in vesicles under a thin membrane surrounding the secretory head cells. The secreted resin component is in large part physically segregated from the secretory cells (11). This isolates the resin from the atmosphere as well as membrane-bound enzyme systems within the secretory cells, possibly protecting the terpenes and cannabinoids from oxidative degradation and enzymatic change. At the base of each cluster of resin head

* Cannabis breeders maintain male clones in the same way and induce them to flower whenever pollen is required to produce seed. However, males are often more difficult than females to maintain in the vegetative state.

Gland Heads Cannabis
Fig. 2. Microscope photograph and drawing of a Cannabis resin gland. The secretory head cells are easily visible within the transparent blister of cannabinoid and terpe-noid-rich resin. (Photo courtesy of David Potter, drawing from ref. 1 .)

cells lies an abscission layer allowing the resin gland and secreted resin to be easily removed by mechanical means (see Fig. 2). Hashish or charas is simply millions of resin glands that have been rubbed, shaken, or washed from fresh or dry plants and compressed into a dense mass (11).

Resin glands containing cannabinoids and terpenes may have an adaptive significance in reducing insect and fungal attack (12). However, Cannabis crops are subject to infestation by a wide variety of pests (13), particularly under greenhouse and grow room conditions.

Continue reading here: Cannabinoid and Terpenoid Biosynthesis

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