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Light spectrum plays a crucial role in regulating the growth of hemp ( Cannabis sativa L.) plants and the biosynthesis of secondary metabolites. Several studies have demonstrated that additional red-light exposure increases biomass accumulation, while supplementary UV-A light stimulates cannabinoid synthesis. Nevertheless, the potential of stage-specific supplementation of red and UV-A light remains underexplored in its capacity to optimize cannabinoid yield in indoor hemp cultivation. In the present study, the effect of red light in combination with UV-A light on hemp biomass and cannabinoid accumulation was investigated using a high-CBD strain. There were four treatments: (1) white light throughout the growth period (control; V W R W ); (2) red light supplementation during the vegetative stage (V WR R W ); (3) UV-A supplementation (V W R WUV ) during the flowering stage; and (4) combined red and UV-A supplementation (V WR R WUV ) during the vegetative and flowering stages. Results showed that V WR R W promoted the number of effective branches (increased by 18.0%) compared to the control (V W R W ), resulting in an increase in inflorescence yield by 17.9%. V W R WUV increased CBG and CBD content by 52.7% and 12.1%, respectively, relative to the control. The effect of V WR R WUV on biomass and cannabinoid accumulation was the strongest among the treatments, with CBG and CBD yields reaching 0.53 g and 4.62 g per plant, representing significant increase of 91.8% ( p  < 0.01) and 44.1% ( p  < 0.01), respectively, compared to the control. However, there were no significant differences in CBD yield among the V WR R W , V W R WUV and V WR R WUV treatments, indicating that the combined supplementation of red and UV-A light did not have an additive effect on CBD accumulation. These findings highlight the potential of stage-specific spectral strategy to optimize both plant growth and phytochemical quantity.

Far-red (FR) light elicits two distinct processes in plants. First, a shade avoidance response which is triggered when the ratio of red to FR (R: FR) declines. Second, it interacts synergistically with higher frequency wavelengths of light (e.g. red or white) which improves the efficiency of photosynthesis. We investigated whether we could harness these phenomena in medicinal Cannabis to improve yields so that the duration of the photoperiod could be reduced to 10 h (“10L”) whilst returning similar or improved yields compared to a 12 h photoperiod (“12L”). The THC concentrations were elevated in both high THC varieties by the different FR treatments. In Hindu Kush the concentration of THC was elevated by the addition of 4 h of total FR (“10L_2_2D”), and in Northern Lights total cannabinoid yields were increased by nearly 70% over the 12 L control (0.43 versus 0.25 g Plant − 1 ) by the addition of 2 h of FR in darkness after 10 h of light (“10L_2D”). Our results show a strong yield and quality advantage in high THC lines treated with end-of-day FR treatments. Furthermore, a lighting schedule of 10L_2D instead of 12 L would result in a saving of 5.5% in power usage and resultant emissions.

Cannabis is among the most water-demanding crops, facing ongoing expansion and water use regulations. This study evaluated the effects of greenhouse sunlight plus increased LED supplemental lighting on flower yield, water use (WU), and efficiency (WUE), as well as flower partitioning, cannabinoids, terpenes, and leaf gas exchange in Cannabis sativa ‘Suver Haze’. The supplemental lighting programs applied during the vegetative and flowering stages were: (1) Static LED levels (PPFD: 150, 300, 500, or 700 µmol m –2 s –1 for 72 days) and (2) Dynamic LED levels (PPFD: 150, 300, or 500 for 28 days, followed by 700 µmol m –2 s –1 for 44 days). Flower yield and crop WUE increased linearly with the increase of Dynamic and Static lighting. For instance, a 4.7-fold Static lighting increase caused a 4.1-fold increase in flower yield and reduced the evapotranspiration per gram of flower by 37%. Furthermore, plants in Dynamic lighting produced up to 10.4% more flowers and 24.8% higher WUE than plants in Static lighting at the same cumulative lighting. Higher leaf photosynthetic rate, WUE, and lower stomatal conductance due to higher light intensity supported the crop results. Cannabinoid and terpene changes were small and complex, with terpene concentration affected by the light program and light level. In conclusion, supplemental lighting substantially enhanced production and WUE, particularly when higher light was provided during flowering.

This study compared the effects of storage time and electron beam (EB) irradiation on microbial counts and chemical stability of dried flowers from two hemp cultivars over 12 weeks. Cannabinoid and terpene content, as well as microbial load, were evaluated at 0, 4, 8, and 12 weeks in EB-irradiated and non-irradiated samples. Microbial count in non-irradiated flowers reached up to 4.1 × 106 colony-forming units (CFU)/g; EB irradiation reduced these levels to <102 CFU/g. Cannabinoid contents were unaffected by EB irradiation and remained stable throughout storage. Terpene content decreased by 8.4% immediately after irradiation, followed by further declines during storage, reaching 22.3% and 24.0% average losses in non-irradiated and EB-irradiated samples after 12 weeks, respectively. EB irradiation caused a higher decrease in monoterpenes (10.8%) than in sesquiterpenes (2.5%). These findings confirm that EB irradiation is an effective sterilization method for hemp flowers that preserves chemical integrity. Storage time also significantly reduced microbial loads in non-irradiated samples; TAMC in cultivar B declined from 20,728 CFU/g to

Journal Article

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