Plants need light to grow, and cannabis is no different. But what happens when you change the type of light used to grow it? Well, a recently published review  and analysis of available scientific research is telling us just how important different light spectrums can be when it comes to growing cannabis. Essentially, the type of light you use affects the phytochemistry of the plant, which then results in different outcomes. Some of those outcomes include increased production and accumulation of cannabinoids, terpenes, and flavonoids. This is great news, considering their medicinal value and therapeutic applications, but how the light changes these different profiles of the plant is an interesting mystery we are still working to understand fully.
The review  notes that as far back as 1987, scientists  discovered UV-B radiation affects the accumulation of cannabinoids. “When the daily dosage of UV-B radiation increased from 0 to 13.4 kJ m−2, the THC [tetrahydrocannabinol] content increased from 25 to 32%,” as well as increasing the total number of trichomes. Another study  mentioned in the same review reported how altitude affects light exposure; when solar UV radiation is increased, it “results in higher CBDA [cannabidiolic acid], terpene, and cannaflavin content…” The review also included a study  that looked at the effects of UV-A radiation, finding “Low percentages of UV-A radiation (2%) from full-spectrum LED arrays induced an increase of several cannabinoids, including CBD [cannabidiol], CBG [cannabigerol], Δ9-THC, and tetrahydrocannabivarin (THCV).” Although UV radiation appears to increase cannabinoid content, the review suggests more research is needed.
The impact of visible light has also been tested on cannabis, showing that lighting conditions and wavelengths also alter cannabinoid content. Blue light increases THC, and LED lighting increases cannabigerolic acid (CBGA) (compared to high pressure sodium lighting). Subcanopy blue green red (BGR) lighting increases terpene accumulation better than BR lighting, but both subcanopy BR and BGR light conditions increase THC and CBGA.
These are just a few of the many different ways changes in lighting conditions and the types of light being used can impact the cannabinoid and terpene profiles of cannabis, making the process that much more valuable to analyze. Even though all this research around photobiology and cannabis growth exists, exactly “how light spectra influence cannabis metabolomics is still largely unknown.” The review concludes with remarks about the need for more in-depth research into the exact influences of light on the biosynthesis of cannabinoids and terpenes throughout the cannabis plant’s life cycle. 
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