Impact of Far-red Light Supplementation On Yield and Growth of Cannabis sativa

Far-red light(700-780nm) induces shade avoidance response in many different species of plants. The shade avoidance response triggers a number of changes in the plant such as cell expansion and stem elongation. This cell expansion has shown to increase yields in leafy greens and increase flower set in tomatoes. Despite there being a void in the literature for Cannabis sativa, far-red lights are often advertised to provide several benefits. This study will evaluate the effects of far-red light supplementation on the yield and height of Cannabis sativa. Five cannabis clones were grown under white (410-730nm) light emitting diodes (LED’s) at approximately 500 µmol/m²/s photosynthetic photon flux density (PPFD). 0,20,40, and 60 µmol/m²/S PPFD of far-red light was supplemented as a control and three treatments. The plants were grown for 6 weeks under 18 hours of light and 6 hours of darkness (vegetative period) and then another 8 weeks under 12 hours of light and 12 hours of darkness (flowering period). Far-red light was supplemented only during the flowering period of this experiment. Measurements of height were recorded at the beginning of the flowering period (week 7) and right before harvest (week 14). At 14 weeks the plants are harvested, dried, and then weighed for dry weight of flower. Finally samples were sent off to a third party lab for cannabinoid and terpene analysis. Results showed a decrease in yield and an increase in height as far-red light intensity increased, these results are significant at a p-value of