Any botanists here have experience with the hyperventilating technique with CO2 or possibly other substances?
No, but I saw a program about vertical farming and agritecture the other day; only salad vegetables though. How about an artificial duck pond at the center of a building complex which can feed on the water-recycled plants above?
I would say you could probably only do it with plants already known to be aquatic plants. A duckpond isn't quite the controlled area called for when growing normal plants hydroponically, not to mention the water that the ducks would be swimming in would be gallons and gallons of a chemical solution. Edit: Plus, there would be a bunch of ducks running around the building.