Would it be possible for plants to evolve a co-dependency on a community of bioluminescent bacteria in order to survive in a low or zero light environment? Such as the plant gathering nutrients and water for the bacteria in its leaves in exchange for an excess of glucose the bacteria produces, or something similar.
How would the relationship between the two organisms affect the plant? Such as how large could they grow, what would their leaves look like and what would be, if any, the side effects of a plant using second-hand glucose?
Is there a real world equivalent of this?
1) Its not impossible. Without getting too deep into the underlying process (you could spend a semester studying plant respiration and barely scratch the surface), plants have two main processes for producing chemical energy. The first is the light reactions, which require light. The second is the dark reactions, which do not require light.
Again, not getting into it too deeply, but the light reactions turn water and sunlight into oxygen and energy. The dark reactions turn carbon dioxide and energy into sugars. Thus, the symbiotic bacteria can either a) provide the light necessary for the light reactions (which @AstroDan showed us is possible), or b) directly provide the energy necessary for carbon fixing in the dark reactions. Note that because the plant will need energy to live, in either energy supply method, the bacteria will not come out ahead energy-wise. The bacteria will have to have some reason it needs the sugars produced by the plant. There could be a multitude of reasons, from long term energy storage to structural support.
2) the plant would probably not look much like a trees or grasses we think of. In all likelihood the bacteria would live inside the plant for protection and convenience. The leaves, if it had any, would lack sunlight to absorb, and consequently have no reason to be flat. The would probably be cylindrical to maximize bacteria holding efficiency. The plants would be low to the water, mosslike, because structural sugars would be hard to come by, and drawing water up a stem would be a waste of water and energy.
it's unlikely that the plant would accept bacteria glucose; it's far more likely that the trade would be the other way around. After all, plants have spent the last few hundred million years perfecting glucose production.
3) A real world... not equivalent, but perhaps similarity, would be coral. Coral polyps (animals, not plants) have this sort of symbiotic relationship. They provide nutrients and shelter to algaes living in them, in exchange for excess chemical energy from the algae (x). This is why coral bleaching is so dangerous to reefs. Without their algae, the polyps have far less food available, and not infrequently starve.
While there are bio-luminescent bacteria they cannot provide energy (in darkness) that will be sufficient to a plant. Also searching for whether plants can survive without sunlight did not yield anything useful. However it is possible for a plant to depend on bacteria that do not require sunlight, but only partially (they get some of the nutrition from the bacteria, the rest from the low amount of sunlight)
A plant could not survive using light from bioluminescent bacteria it is feeding, as this would mean that the plant's energy is coming from itself, which is not possible. However, something similar could evolve. If a species of virus evolves to spread itself by mycorrhiza, then a tree might evolve to have a powerful bioluminescent organ, which it shines like a spotlight on the tree's offspring, allowing it to feed them without them needing to connect to potentially dangerous mycorrhiza.