Title: THE EFFECTS OF ULTRAVIOLET-B RADIATION ON THE GROWTH, PHYSIOLOGY AND CANNABINOID PRODUCTION OF CANNABIS SATIVA L. (MARIHUANA, SECONDARY PRODUCTS, DELTA-9 THC)
Author(s): LYDON, JOHN
Institution: UNIVERSITY OF MARYLAND COLLEGE PARK; 0117
Source: DAI, 47, no. 04B, (1985): 1386
Abstract: The concentration of cannabinoids in Cannabis sativa L. is correlated with high ultraviolet-B (UV-B) radiation environments. (DELTA)('9)-Tetrahydrocannabinolic acid and cannabidiolic acid, both major secondary products of C. sativa, absorb UV-B radiation and may function as solar screens. The object of this study was to test the effects of UV-B radiation on the physiology and cannabinoid production of C. sativa.
Drug and fiber-type C. sativa were irradiated with three levels of UV-B radiation for 40 days in greenhouse experiments. Physiological measurements on leaf tissues were made by infra-red gas analysis.
Drug and fiber-type control plants had similar CO(,2) assimilation rates from 26 to 32(DEGREES)C. Drug-type control plants had higher dark respiration rates and stomatal conductances than fiber-type control plants. Transpiration, mesophyll conductance, leaf area, leaf dry weight and specific leaf weight were not significantly different between drug and fiber-type controls.
The concentration of (DELTA)('9)-tetrahydrocannabinol ((DELTA)('9)-THC, but not of other cannabinoids) in both vegetative and reproductive tissues increased with UV-B dose in drug-type plants. None of the cannabinoids in fiber-type plants were affected by UV-B radiation. There were no significant physiological or morphological differences among UV-B treatments in either drug of fiber-type plants.
The increased level of (DELTA)('9)-THC found in leaves after irradiation may account for the physiological and morphological insensitivity to UV-B radiation in the drug-type plants. However, fiber plants showed no comparable change in the level of cannabidiol (CBD). Thus the contribution of cannabinoids as selective UV-B filters in vegetative C. sativa is equivocal. Nevertheless, drug-type plants may experience more reproductive success in high UV-B environments due to the additional protective screening of floral tissues. Alternatively, cannabinoids may function as defense chemicals against herbivory.
Resin stripped from fresh fiber-type floral tissue by sonication was spotted on filter paper and irradiated continuously for 7 days. Cannabidiol (CBD) gradually decreased when irradiated but (DELTA)('9)-THC and cannabichromene did not. The lack of the photochemical conversion of CBD (in its resin concentrate) into (DELTA)('9)-THC indicates that such conversions are not responsible for the trace amount of (DELTA)('9)-THC found in many fiber-types of C. sativa.
Accession No: AAG8614253