Trichomes

Photo 1: Black & white magnified trichomes.
Photo 2: Magnified colour image of trichomes.

"It is during the last few weeks of life that the female plant is most active in the production of cannabinoids and terpenes. The plant will produce variable inflorescences, these being complex clusters of flowers and bracts. Close examination of these inflorescences reveals the individual flowers, which are fairly insignificant to the naked eye. Each flower consists of a furled specialised single leaf- the calyx- within which is housed the ovary.
Protruding from each calyx are two pistils (each comprising a fused style and stigma). These are white, pink or yellowy green in colour and up to 20 mm long. The pistil's function is to trap passing pollen. Within minutes of landing on the pistil the pollen can germinate, its pollen tube then migrating to the ovule where fertilisation is completed.

Each calyx is covered in minute sticky organelles- the stalked glandular trichomes. Although the individual trichomes are only just visible to the naked eye, in vast numbers they make a striking presence, covering the lowers in a layer of white 'frosting'. Viewed in strong daylight, these trichomes sparkle like drops of dew, giving the cannabis plant a unique beauty. By reflecting the light so spectacularly, the trichome-surrounded flowers must clearly derive some protection from the scorching sun.
When viewed through a hand lens, each trichome resembles a golf-ball (the resin head, also known as the glandular head) sitting on a tee (the trichome's stalk). Brushing the plant will rupture some of these resin heads, immediately releasing the distinctive heavy, aromatic smell of the essential oils containing terpenes such as limonene and myrcene. Traces of many other terpenes and terpenoids contribute to the characteristic aroma of cannabis. Up to 70 compounds of this type are present, albeit many of them in very small quantities. In addition to these volatile compounds, the trichomes are extremely rich in cannabinoids, which are themselves odourless. Separated from the dried plant by shaking and sieving, or similar methods, these trichomes constitute the prime ingredients in hash.
Resinous stalked glandular trichomes are most abundant in the flowers, but significant numbers are sometimes also found on the upper-most leaves. Trichome production reaches its peak in the late flowering stage, and this gives an indication of the optimum time to harvest the plant. Elsewhere on the foliage and stems the plant also develops small sessile (unstalked) glandular trichomes, also known as peltate trichomes. These also release essential oils when touched, but as the fragrance generally differs from that of the oils in the stalked glandular heads near the flowers, the exact function of these organs is perhaps different.

- pp. 23- 26, Growth and Morphology of Medicinal Cannabis in The Medical Uses of Cannabis and Cannabinoids edited by Geoffry W. Guy, Brian A. Whittle & Philip J. Robson (2004); Pharmaceutical Press.

Trichomes in Colour
Trichomes in Black & White
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