Histochemical Analyses of Laticifers and Glandular Trichomes in Cannabis sativa

Abstract

The unbranched nonarticulated laticifer, including its latex, and capi.tate glandubr trichomes from Cannabis saliva L. were analyzed in fresh and cryo­ stat preparati ons with histochemical procedures for the presence of cannabinoids, alkaluius, aml other selected celiular components. A positive response to cannabinoid indicators, Duquenois-Negm, fast blue salt B, Gibb, and Beam reagents occurred in laticifers, as well as exuded latex and in disc cells of epidermal capitate glandular trichomes. No response or only an apparent background response to these reagents was detected in other cells. Alkaloids were detected histochemically in laticifers and exuded latex with Wagner, Dittmar, Ellram, chromic acid, Hager, and Dragendorff reagents. Alkaloid indicators also reacted with capitate glandular trichomes but did not show a positive response in other cells of the plant. Laticifers also contained other specialized contents including the enzymes, cytochrome oxidase, and lipase. Free lipids and storage proteins were not detected in laticifers. Qualitative responses to these histochemical procedures were similar in laticifers and capitatelandular trichomes from various regions and organs of the plant axis. Histochemical indi­ cators can be useful for preliminary surveying of specialized cell types and tissues for the presence of specialized substances. Recent investigations of the chemistry of Cannabis sativa L. have identified a group of terpenophenols, the cannabinoids, which occur only in this genus (1, 2, 3). The major cannabinoids, including � 9 -tetrahydrocanna binol (� 9 -THC), cannabinol (CBN), and cannabidiol (CBD), are utilized in the chemical characteri­ zation of drug, nondrug, or fiber strains of Cannabis (4, 5). These compounds appear to be most abundant in actively growing regions of the shoot system of both pistillate and staminate plants (6). Several recent studies have indicated that these cannabinoids accumulate in epidermal glandular trichomes (7, 8, 9). However, there have been few studies of the relationship of cannabinoids to laticifers, an internal secretory system, or to other specific cells or tissue systems in the plant. Similarly, the presence of alkaloids, including choline and trigonelline, already noted in the early literature (10) have been reported from Cannabis tissues (11, 12, 13). Other investigators have identified a group of cannabimine (14) as well as hordenine, neurine, and spermidine (15, 16, 17, 18) alkaloids from various portions of this plant. The presence of alkaloids has not been related to specific cell types or tissues in this genus, although alkaloids are common constituents in specialized cells such as the laticifer in other plants. The purpose of this study is to examine whether histochemical procedures can be utilized effectively to survey plant tissues for their general composition. Histochemical techniques are applied to the laticifer and glandular systems as well as other cells to determine sites of accumulation of cannabinoids, alkaloids and other specific compounds in these cells. We will show that these techniques can be useful for preliminary surveying of cells and tissues for the presence of specialized substances.