Trichomes, Cannabis and Light Microscopy

1974).
             Cannabinoids.
             The surface of Cannabis sativa L. is covered by glandular trichomes which are the source of cannabinoids (Turner et al. 1978). Cannabinoids are compounds that are unique to the genus Cannabis, and are the active drug ingredient in marijuana (Pate 1994). Cannabinoids are released by the epidermal glands of the plant (Pate 1994). Cannabinoids are present mainly in the epidermal glands and not in non-glandular trichomes (Malingre et al. 1975). Their glands vary in shape, size and density depending on the location of the anatomy examined (Pate 1994). Most aerial parts of the plant possess both glandular and/or non-glandular trichomes (Dayanandan and Kaufman 1976; Pate 1994). The glandular trichomes are considered to be the primary location of cannabinoids (Dayanandan and Kaufman 1976). The glandular trichomes release a hallucinogen called Î"-9-tetrahydrocannabinol, which is used in the preparation of the drug marijuana (Pate 1994).
             Glandular Trichomes.
             There are three types of glandular trichomes that occur on the female plant, especially on the flowering bracts (Dayanandan and Kaufman 1976). These include; (1) the capitate-stalked trichomes which are composed of a large multicellular head that terminates a stalk at a variable height, (2) capitate-sessile trichomes have a large head but a short stalk, and (3) bulbous trichomes which are composed of a large multicellular head (Hammond and Mahlberg 1973; de Pasquale et al. 1974; Emboden 1974; Turner et al. 1978; Pate 1994). Both capitate-stalked and capitate-sessile trichomes are the main source of cannabinoids (Turner et al. 1978).
             Non-Glandular Trichomes.
             The non-glandular trichomes are very abundant on the epidermis of the plant (Turner et al. 1978). There are two types of non-glandular trichomes: (1) squat unicellular cystolith trichomes, these hairs are abundant on the upper surface of leaves and bracts, and (2) elongated unicellular covering hairs (non-cystolith trichomes) which are present on leaves, the lower surface of bracts and bracteoles (Fairbairn 1972).