If you took the chemicals a plant gains through photosynthesis and put it through the plants' roots or by injection, or used as a foliar application for intake through the stomata, would the plant need light? If not, how would it respond to the treatment?
Not exactly the same thing, but a species of algae has been genetically altered to allow it to uptake glucose, bypassing the need for photosynthesis: http://www.unisci.com/stories/20012/0615013.htm
I doubt this would work for the vast majority of plants. I think it would cause root rot as the microorganisms in the soil would out-compete the plant. Also the transport systems of the plant might not be efficient in this direction.
I mean might there be a plant somewhere where this might work? Sure. Fungi that grow in the dark would be a lot like such plants, so its biologically possible. There might be a primitive plant that doesn't need its chloroplast to be active to live. I've never heard of one and wikipedia is not helping here...