If carbon dioxide is completely removed from a plants environment, what would you expect to happen to the plants production of high-energy sugars

The plant's production of high-energy sugars would reduce significantly. I'm not going to say that the plant would completely stop producing the sugars because it has to respire, and one product of respiration would be carbon dioxide. This carbon dioxide would be recycled so that the plant can photosynthesize and produce sugars.

If carbon dioxide is completely removed from a plant's environment, I would expect the plant's production of high-energy sugars to decrease. The amount of sugar produced by a plant is, within a limit, proportional to the amount of carbon dioxide available. You can see this by looking at the chemical formula for photosynthesis: 6CO2 + 6H2O + light energy = C6H12O6 + 6O2. As one can see, it takes exactly 6 carbon dioxide atoms (among other things) to produce 1 molecule of sugar. If you were to remove remove the carbon dioxide from the plant's environment, it'd have no carbon dioxide to produce the sugar.