Answer:
More CO2 molecules are responsible for production of more carbohydrates.
Step-by-step explanation:
Plants make their carbohydrates (food) by process called photosynthesis. CO2 is responsible for Carbon Fixation in Calvin cycle during photosynthesis. The more CO2 is utilized the more carbohydrates can be manufactured.
Thus, if plants are grown for several days in atmosphere where more 14CO2 is available as compared to 12CO2 then more food (starch-carbohydrates) production can be accomplished.