Cellular Origins of Cannabinoids

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Until they are about to flower, the plants have only two types of hairs. The unicellular covering hairs (trichomes) are long and thin and end in a point (see figure 9e). These are few until the plant is one month (in warm climates) or two months {in temperate climates) old. They subsequently show a gradual increase in number and are especially common on flower-bearing branches where they form a silky down. The second type of hair (cysto-lith) is short, swollen at the base and set into the surrounding epidermal cells (see figure 9a). Their end is blunt and they usually contain calcium carbonate crystals. They arc found mostly on the upper surface of the leaves and bracts (small specialized leaves surrounding the flowers), and sometimes on the lower surface of the branches.

When the females are about to flower, their tops become covered with multicellular glandular hairs, which appear to the eye as tiny brilliant points. When the female flower first matures, these hairs form a base of two cubical cells supported by two wedge-shaped epidermal cells and a globular head of four cells, all covered by a thin cuticle (waxy non-cellular layer). (Sec figure 9f). At maturity, the head may contain as many as 16 radially arranged cells, which secrete the cannabinoid containing oil that accumulates between the cells and the cuticle

Double Cystolith

Fig. 9. Cross section of a bract from the fruiting plant: a, cystolith hair; b, large grandular hair with several cells in head and stalk; c, head of one of the large glandular hairs; d, small glandular hair with bicellular head and unicellular stalk; e, thick walled conical trichomes; f, large developing glandular hair;g, stalk of a large glandular hair; h, palisade cell; i, cluster crystal;/, parenchymal cell; k, stomate. (Reprinted by permission, from Joyce and Curry, The Botany and Chemistry of Cannabis, 1970. Drawn by O. Erasmus.)

Fig. 9. Cross section of a bract from the fruiting plant: a, cystolith hair; b, large grandular hair with several cells in head and stalk; c, head of one of the large glandular hairs; d, small glandular hair with bicellular head and unicellular stalk; e, thick walled conical trichomes; f, large developing glandular hair;g, stalk of a large glandular hair; h, palisade cell; i, cluster crystal;/, parenchymal cell; k, stomate. (Reprinted by permission, from Joyce and Curry, The Botany and Chemistry of Cannabis, 1970. Drawn by O. Erasmus.)

(see figures 9b and 9c). When sufficient oil has accumulated, the cuticle may burst, releasing the oil (composed of about 50% cannabinoids), which quickly dries to form the sticky resin. Another view is that the cuticle is composed of oxidized resin.

These hairs vary in appearance: those of the bracts and axes of the female flowers develop an elongated stem and resemble a tiny mushroom, while others (especially on the lower surface of the top leaves) lack the stem and have a flat, round head with a masimum of ten cells (sessile glands). There is reason to believe that sessile glands are a distinct type and not an early stage of the stalked glands. All these cells lack chloroplasts and are colorless except for the amber oil produced in the head. Lesser amounts of cannabinoids are also produced by cells generally distributed throughout the epidermis of the plant (lactifers).4

Fig. 10. Scanning electron microscope picture of the lower surface of a bracteole (seed covering) magnified 100 times. The stalked glandular hairs are seen in various stages of development. Two simple covering hairs are shown at the upper right. (Reprinted from Fairbairn, Bulletin on Narcotics, Vol. 24, 1972.)

Fig. 11. Scanning electron microscope picture of a stalked glandular hair from a bracteole (seed covering) magnified 400 times. Cannabinoids are concentrated in the round head. The rectangular lumpy "bricks" are cells. (Reprinted from Fairbairn, Bulletin on Narcotics, Vol. 24, 1972.)

Fig. 10. Scanning electron microscope picture of the lower surface of a bracteole (seed covering) magnified 100 times. The stalked glandular hairs are seen in various stages of development. Two simple covering hairs are shown at the upper right. (Reprinted from Fairbairn, Bulletin on Narcotics, Vol. 24, 1972.)

Fig. 11. Scanning electron microscope picture of a stalked glandular hair from a bracteole (seed covering) magnified 400 times. Cannabinoids are concentrated in the round head. The rectangular lumpy "bricks" are cells. (Reprinted from Fairbairn, Bulletin on Narcotics, Vol. 24, 1972.)

Heredity and Environment

Regardless of seed origin, several generations in a new location will produce a plant resembling those native to the area where it is being grown. This fact has been known for centuries. In 1712, Kaempfer observed that seeds of Persian Cannabis failed to produce significant quantities of intoxicating resin when grown in Europe for several generations. Similarly, in the early nineteenth century, the Egyptian Viceroy, Mehe-met Ali, found that the French hemp seeds he imported to provide fiber for rope were useless for that purpose. After a few growing seasons the plants became short and bushy, producing large quantities of resin. (Part of the explanation undoubtedly lies in the shorter days of Egypt.) In that same century, Christison at Edinburgh, Hope in England and Hus-son in Cairo observed the same phenomenon when they planted imported seeds. In a report published in 1912, pioneer marijuana researcher, J. Bouquet, described the nature of the change that can occur in only a single generation. He said that seeds from India (Guaza) and Greece (Tripolis) planted at Lyon in France produced plants about two meters tails. They were robust and bushy with many branches and large, deep-green leaves with sharply indented edges and (in the Indian variety) distinct furrows on the upper surface of the petioles (leaf stems). The petioles of the Indian variety were reddish-brown but lost their color with age. The flowers were concentrated in clusters of cymes (main and secondary branches always terminate in a single flower) and the groups of clusters were separated from one another by leaves and well-developed bracts nearly hid the flowers from view. (Bracts are modified leaves which surround and protect the flowers and, later, the seeds.) The large, vigorous flowers gave off an intense mint-like odor which was perceptible more than two meters away. At maturity, the flowering tops were covered with shiny points which were tiny reddish droplets of resin in the glandular hairs.

When the seeds from the above plants were grown the next year at Moulin-sur-Allier, the plants were little different from those commonly cultivated in France for fiber. They were only slightly bushier, and of a somewhat deeper green than the native fiber plants, but did not have the bushy flowering tops or the furrowed, colored petioles and resin production of their ancestors. The tops were not even sticky. But seeds from the same batch were planted the same year at Beja in Tunisia (altitude: 330 meters). The resulting plants were very similar to the first generation Indian and Greek plants grown at Lyon, with their bushy odiferous flowers and intense resin production.

The second generation plants at MouIin-sur-Allier may have cross pollinated with the French fiber strains of marijuana or may have been the result of natural selection. It is likely that if the same 100 seeds of Indian marijuana were planted in India and in France, we would find differences in the number of seeds germinating. The plants which grew to adulthood would probably represent a different range of seeds in the two cases. Also, the average genetic makeup of their seeds, even if inbred, would probably differ, depending on the selective forces acting on the developing seeds and pollen. The longer days of the northern latitudes probably contribute to lengthening the internodes and altering other characteristics of the growing plant.5 Some experiments on the effect of day length on resin production are discussed later.

In relation to the role of a hot, dry environment in the production of the THC containing resin, observations made by Bouquet some 40 years ago on an aberrant variety which arose in 1935 in Tunisian crops are of great interest.

In Tunisia, it arose independently in plantations at Tabarka and Sedjenanc, located some 40 kilometers apart in the mountainous region. The seeds originated as usual from the previous year's crop, and the resulting abnormal seeds may have derived from a very few plants of the previous year and ultimately from a mutation occurring in a single plant.

The most striking characteristic of these plants was their very slow maturation. Whereas the usual variety flowered and set seed in some 14 weeks and was harvested at the beginning of July, the new type did not set seed for 22 weeks and was collected at the middle of September. Of major importance is the fact that its characteristics were fully heritable and plants grown the following year in Tunis and the United States were essentially identical. There were other striking differences from normal plants. They were slightly over a meter tall, which height, though differing little from the usual Tunisian plants, was maintained in the U.S.A. plantings, where they were markedly shorter than the rest of the crop. The plants were branched almost to their base with an extremely bushy, compact aspect. The stems are generally larger (up to 9.5 cm in circumference at the base) and sturdier than normal with longer, stronger fibers and being more deeply ribbed or fluted, though feeling smoother to the touch. The taproot was turnip-shaped (napiform) some 12.2 cm around and 12 cm long, then tapering off to a total length of 32 cm, while the ordinary type was not napiform and generally shorter. The new variety had much more numerous adventitious roots.

The leaves were always opposite from the base of the stem to the top (always imparipinnate) while the normal variety is sometimes alternate. The leaves rarely reach 10 cm from the point of insertion on the petiole to the end of the longest median leaflet, whereas the typical leaves average 20 cm. All the leaves have seven or nine leaflets with 12 to 16 teeth on each edge compared to five, seven, nine, or 11 leaflets and 14 to 22 teeth normally. The plant has a deeper green color on upper leaf surfaces but the underside of the leaves is light green at first, becoming almost white at maturity, and thus resembling the wormwood (Artemisia vulgaris) leaves. The leaf veins are deeper than normal, giving the impression of regular folds in the leaflets, and being noticeably more visible on the inferior face than usual. The threadlike (filiform) stipules at the base of the petioles of the upper leaves are a deeper yellow-orange than normal. The bracts (specialized leaves surrounding the flowers) are better developed, longer and more numerous than usual, forming little tufts. The flowering tops are less numerous, more elongate or less compact than typical with 0 to 8 seeds per inflorescence compared with the normal of 40 to 60. The tops are not sticky and the minty odor is absent even when the plant is crushed between the fingers.

Microscopically, the powder from the edge of the leaflets and the bracts is gronze-green rather than yellow-green, and again lacks the characteristic odor of fresh powder. The micro-structure appears normal, with double calcium oxalate crystals, and the various types of hairs—unicellular pointed, short cysto-lithic (containing calcium carbonate crystals), conical, swollen with blurt extremity, etc., but the clubbed, stalked (pedicellate) secretory hairs arc rare, poorly developed, and for the most part devoid of the clear amber oily resin. Both male and female flowering tops give positive reactions for cannabidiol with the male reaction being weaker, as is that of the female prior to flowering.

These observations show that we cannot necessarily expect plants to be exactly like their parents in appearance or THC content, even in the first generation. In subsequent generations the difference may be even greater and the plants may soon resemble those growing wild in our area. However, if we are very careful about our pollen source, we may succeed in growing a high THC strain for many generations since, as subsequent sections show, cannabinoid production is largely a matter of genetics.

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  • bailey
    Does hemp leaves have cystolic hairs or covering hairs?
    3 months ago

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