Literature suggests that cannabinoids in Cannabis sativa play a major role in plant defense. They are associated with protective responses against desiccation, microorganisms, predators and high photon flux radiation (Pate 1994). They have been suggested to have similar actions as flavonoids, which absorb harmful UV wavelengths and protect the photosystem from high UV and blue irradiation (Lydon et al. 1987).
Short wavelength irradiation has been shown to increase ∆9-THC concentration in drug-type Cannabis sativa (Lydon et al. 1987).
The response to incident UV flux or elevated amounts of blue photons in a spectrum are well described for many different plants species by activating and stimulating the biosynthesis of secondary metabolites. The so called “defense mechanism” is mediated and controlled by the photoreceptors.
In spectra with elevated amounts of blue light more cannabinoid yield in relation to the applied intensity was obtained.
The additional UV-A light (405nm) resulted in all combinations in the lowest THC concentration and cannabinoid yield.
Supplemented blue light (450nm) resulted in increased concentrations of THC and higher cannabinoid yield compared to the standard treatment and the standard treatment supplemented by UV-A (405 nm).