Figure 1.

Cannabinoid biosynthesis occurs in glandular trichomes borne primarily on pistillate inflorescences composed of leaves, bracts, and florets. (A) Pistillate inflorescence with receptive, white stigmas before pollination. Scale bar = 1 cm. Photo credit: George Weiblen. (B) Scanning electron micrograph of an immature pistillate floret enclosed by a pair of imbricate bracts (br1 and br2) bearing multicellular hairs. Scale bar = 0.1 mm. Photo credit: David Marks. (C) Scanning electron micrograph of stalked glandular trichomes (gt), sessile glands (sg), and cystoliths (cy). Cystoliths are pointed hairs containing calcium carbonate crystals. Scale bar = 100 µm. Photo credit: David Marks. (D) Biosynthesis of major cannabinoid compounds. CBDA and THCA are produced enzymatically from a common CBGA precursor by different enzymes. Both compounds may be decarboxylated to pharmacologically active neutral forms CBD and THC, respectively.