Nitrogen supply affects cannabinoid and terpenoid profile in medical cannabis (Cannabis sativa L.)

Secondary metabolism in plants is considerably affected by environmental factors including mineral nutrition. Nitrogen is a key plant nutrient, known to affect primary and secondary metabolism in plants, that its effect on the cannabis plants' chemical profile is not known. To evaluate the hypothesis that N supply affects the cannabinoid and terpenoid profile, we studied the impact of N application on chemical and functional-physiology phenotyping in medical cannabis at the flowering stage. The plants were grown under five N treatments of 30, 80, 160, 240, and 320 mg L−1 (ppm) under environmentally controlled conditions. The results revealed that N supply affects cannabinoid and terpenoid metabolism, supporting the hypothesis. The concentrations of most cannabinoids and terpenoids tested were highest under the deficient concentration of 30 mg L−1 N and declined with the elevation of N supply. The concentrations of the two main cannabinoids, tetrahydrocannabinolic acid (THCA) and cannabidiolic acid (CBDA), decreased by 69% and 63%, respectively, with the increase in N supply from 30 to 320 mg L−1 N. Plant development and function were restricted under inputs lower than 160 mg L−1 N, demonstrating N deficiency. The morpho-physiological state of the plants was optimal at supply rates of 160–320 mg L−1 N. Inflorescence yield reflected the plant physiological state, increasing with the increase in N supply up to 160 mg L−1 N, and was unaffected by further increase in N. These results of the functional and chemical characterizations suggest that high N supply has adverse effects on the production of secondary compounds in cannabis, while it promotes growth and biomass production. Hence, N supply may serve for the regulation of the cannabinoid and terpenoid profiles, or for increasing plant yield, according to the desired production scheme. Taken together, the results reveal that the optimal N level for yield quantity, that allows also a relatively high secondary metabolites content, is 160 mg L−1 N. Finally, the present study provides a better understanding of the impact of N on 'drug-type' medical cannabis physiology, and takes us one step closer to the optimization of medical cannabis cultivation.