If a plant were to absorb a substance that readily reacts with carbon dioxide in the stroma, the dark reactions would be most likely to:

The right answer is the dark reaction would stop happening.

The Calvin cycle (or dark reactions, independent of the sunlight) makes it possible to manufacture glucose, an energy molecule, from carbon dioxide. This is called carbon fixation. There are three reactions of this cycle take place in the stroma of chloroplasts: the first of which is the fixation of carbon dioxide. which is a limiting step in this cycle. If a substance other than the components of the dark reactions absorbs and uses carbon dioxide, the carbon cycle will not be able to occur for lack of one of these ingredients which is the CO2.