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We have demonstrated in previous studies that the essential macro-nutrients nitrogen (N) and phosporous (P) have profound effects on the production of cannabinoids and terpenoids in the cannabis plant. The present study was undertaken to evaluate the hypothesis that potassium (K) supply, which is known to substantially affect plant development and function, affects the secondary metabolism of the cannabis plant. Two cultivars of medical cannabis were grown in controlled environment conditions, under five levels of K supply: 15, 60, 100, 175, and 240 mg L−1 K. The results revealed that the development and function of plants that received the low K supply of 15 mg L−1 K were impaired, as the plants suffered from visual chlorosis, and the inflorescence yield was reduced in both cultivars. Plants that received higher K inputs in the range of −175 mg L−1 K demonstrated optimal plant function and high yield, and one cultivar demonstrated over-supply symptoms under the high K level of 240 mg L−1. The concentrations of most cannabinoids and terpenoids declined with the elevation of K supply, thus supporting the hypothesis. As secondary metabolite concentrations decreased with the increase in K supply, and higher K levels had no positive effects, 60 mg L−1 K is the suggested application level to maintain high function and yield combined with high secondary metabolism. [ABSTRACT FROM AUTHOR]

The standard two-step methods for grafting horticultural crops involve cultivating the rootstock for a period of time and then connecting the scion. Medicinal Cannabis differs from most annual horticultural crops because it is usually clonally propagated from cuttings. We developed a grafting methodology specifically for medicinal Cannabis, involving a single step, in which a freshly cut scion is grafted to a freshly cut donor stem that will become the rootstock. This study also aimed to uncover a potential role for roots in influencing cannabinoid content. Two varieties with desirable attributes but cultivation limitations were selected to act as scions. The first, "CBD1" was a high CBDA accumulating variety with low biomass yield, and the second, "THC2", was a high yielding, high THCA accumulating line with inconsistent root development during cloning. Two candidate rootstocks, "THC9r" and "THC8r", were identified; both were high THCA, low CBDA varieties. Biomass yields in the THC2 scions grafted to THC9 rootstocks (THC9r_2s) were 20% higher than in the non-grafted THC2 plants. In CBD1 grafted plants, the concentrations of CBDA and some minor cannabinoids were significantly different to non-grafted CBD1, but biomass yields were lower. There was a trend towards a higher concentration of THCA in THC9r_2s plants, and when combined with the increased biomass, yield of THCA was increased from 8 g Plant−1 to 13 g Plant−1. Our results present a new grafting method for medicinal Cannabis that improved yield in THC2 and required no additional cultivation time. [ABSTRACT FROM AUTHOR]