Fig. 4

Capitate trichome development on cannabis strain SQ, lower bract surface, at 3 and 6 weeks of inflorescence development. a At 3 weeks, most capitate trichomes at the tip of the bract are sessile. b Close-up view showing a mixture of sessile-capitate trichomes with bulbous trichomes and nonglandular hairs. There are no stalked-capitate trichomes. c–e Presecretory (sessile) trichomes showing the outlines of presecretory disc cells. f A range of stalk lengths have developed on capitate trichomes, and sessile trichomes can be seen in the background. g At 6 weeks, stalked-capitate trichomes are densely packed together on the underside of the bracts and have formed long stalks. h Some stalked-capitate trichomes that form at the edge of a bract have extremely long stalks, up to 1000 μm (arrow). i Magnified view of capitate trichomes showing fully formed heads surrounded by a cuticle