If the experimental plants were grown in an atmosphere of pure 12CO2 for two days, then harvested and the plant material carbon dated and compared to plant material from control plants grown in a normal atmosphere, what would the carbon date reveal?

A series of experiments was run in order to determine the effects of various gases on the growth processes of plants. Each plant was cultured until fully grown in a soil containing an excellent balance of both macro- and micronutrients, and the soil was laden with adequate mycorrhizae culture. After this maturation growth phase, the plants were sealed in separate gas chambers into which a single gas was introduced to replace the normal atmospheric composition. The plants were then given adequate water provisions and observed compared to controls grown under normal atmospheric conditions.