If you give a plant more light, it will need more of most nutrients to take advantage of the increased light. additionally, at specific light levels the rate limiting fuel for photosynthesis may be carbon dioxide (easy to provide in closed environments impossible if growing outside). I would just give the plant a bit more fertilizer.
there is some compounds that have been shown to benifet photosynthesis: Triacontanol (TRIAA) can increase quantum yeild, Silicon has been reported to increase chlorophyll content in some plants, and a product with an unnamed compound by the company Optic Foliar called WATTS. I have not experimented with any of these in regards to helping plants utilize higher light levels FYI, this is just from research.
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