There is growing evidence within the horticultural sphere that adding supplementary UV light to an indoor growing environment can stimulate plants to produce more secondary metabolites and other protective compounds. Some of the potential benefits of supplemental UV are:
Increased oil production
Killing or suppressing powdery mildew
Killing or suppressesing insects
More dense compact flowers
UV (ultraviolet) light sits just outside the range of wavelengths visible to the human eye and is found in natural sunlight. UVa occupies the 315-400 nm (nanometer) range, while UVb and UVc occupy 280-315 nm and 100-280 nm respectively.