Bot. Gaz. 144(1):43-48. 1983.
Paul G. Mahlberg And John K. Hemphill
Department of Biology, Indiana University, Bloomington, IN 47405
Keywords: Cannabis sativa, Cannabaceae, cannabinoids, gland, development, structure
Plants of a drug strain of Cannabis sativa L.-grown 33 days under daylight, shaded daylight conditions, filtered green, blue, and red light, and darkness-were analyzed by gas-liquid chromatography for their cannabinoid content. The highest content of cannabinoids, predominantly D9-tetrahydrocannabinol (D9-THC) in this strain, occurred in the youngest leaves of daylight-grown plants. Leaves at successively lower nodes of this control condition and all treated plants subsequently grown in daylight contained progressively lower levels of cannabinoids. Leaves from plants grown under filtered green light and darkness contained significantly lower levels of D9-THC than those from plants grown in daylight. However, the D9-THC content of leaves from plants grown under shaded daylight and filtered red and blue light did not differ significantly from the D9-THC content in daylight controls, indicating that these conditions did not alter the synthetic rate of this cannabinoid. The cannabichromene (CBC) content of plants grown under filtered red and green light and darkness differed from the CBC content in plants grown in daylight, indicating that the formation of this cannabinoid was independent of D9-THC. Leaves from plants grown under filtered red and green light and darkness recovered the capacity to synthesize typical levels of A’-THC and CBC when placed under daylight conditions. Plants from all light and dark treatments, when subsequently placed under daylight conditions for 66 days, attained levels of cannabinoid synthesis comparable to the daylight controls.