Interplay between chemistry and morphology in medical cannabis (Cannabis sativa L.)

Abstract

Despite the long history of cannabis use, the chemical and physiological state of the plants have not sufficiently been addressed due to legal restrictions. Hundreds of secondary metabolites of therapeutic potential were identified in cannabis. This large number, together with the need to standardize chemical composition of the plant material supplied to patients dictates a need to understand interrelations between morphology and chemistry. The present study investigated the interplay between chemical profiles (of cannabinoids and the ionome) and locales in the plant body. We studied location and organ-specific effects on chemical profiles of cannabinoids, the ionome and physiological traits. A number of important morphological-related chemical trends were identified, which demonstrate in-planta variation in regulation of the chemotype: The cannabinoid profile changes with location along the plant demonstrating significant variation among differing heights for almost every cannabinoid studied. The content of most cannabinoids (including THC, CBD, CBG, CBC, THCV) substantially increased with plant height, both in the flowers and the inflorescence leaves. The concentration of cannabinoids in the inflorescence leaves is considerable and for THC and CBD reached about half of that found in flowers. Concentration in fan leaves is about 1/10 the concentration found in flowers. A number of cannabinoids, including CBC and CBG, were present in the inflorescence leaves at equal or greater levels than in the flowers. The partitioning of mineral nutrients between plant organs demonstrate typical uptake and translocation in the plant. The lower concentrations of N, P, K and higher concentration of Ca in fan-leaves compared with inflorescence-leaves, a result of in-planta translocation abilities in the phloem, supports the physiological findings that the fan leaves are older than the inflorescence leaves. The substantial spatial gradients in secondary-metabolites demonstrate organ and location-specific regulation of accumulation. This in-planta variability in regulation of the chemotype requires standardization for the development of Cannabis as a therapeutic crop for modern medicine.