UVA light benefits plants by activating certain sensors that regulate plant development, chloroplast movement, and stomatal opening (essential for breathing). In some plants, it also boosts the production of flavonoids.
Some plants, like cannabis, appear to produce more THC when exposed to UVB radiation. It accomplishes this by inducing the plants to create malonyl-CoA, a substance that is necessary for the production of cannabinoids.
It’s interesting that in some trials, UVB doesn’t lead to more CBD being produced. To further comprehend this, more study is required.