Glandular trichomes are known to be the sites of cannabinoid accumula-tion in Cannabis sativa. They cover the surface of the aboveground plantparts but are most abundant on the floral bracts of pistillate plants. Thisstudy conducted to determine where the cannabinoids are synthesizedand localized at the whole-plant level and at the cellular level usingmicromanipulation and transmission electron microscopy. According totheir external features, three types of glandular trichomes are recognized:bulbous, capitate-sessile, and capitate-stalked trichomes. The gland headconsist of disc cells containing cytoplasm and a non-cellular intrawallsecretorycavity. The lipoplasts in the disc cells of globose heads synthesizelipophilic terpenes that migrate through the plasma membrane and intothe cell wall adjacent to the secretory cavity. They subsequently passthrough the cell wall and accumulate in the secretory cavity in the form ofsecretory vesicles. Numerous vesicles of different sizes and densities arelocalized in the secretory cavity. In conclusion, lipophilic terpenes andphenols, when released from their respective lipoplasts and vacuolecompartments, accumulate in the plasma membrane/cell wall interface,where enzymes combine these precursors into cannabinoids. Matureglands possess the highest concentration of major cannabinoids, such asCBD in the fiber strains and THC in the drug strains of Cannabis sativa.
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