Plants still need to use the glucose, though. It's misleading to say that plants produce CO2 at night (since they produce it all the time); rather, they become a net CO2 producer at night because they're not offsetting it with photosynthesis.

I'm not convinced that grow lamps are an effective way to offset that, since photosynthetic efficiency is fairly low (3-4%), and the electricity for the lamp has to come from somewhere. Not to mention that lamps (even LEDs) are also fairly lossy. I'm also not convinced that's even worth optimizing.