A student investigated how the rate of photosynthesis in Canadian pondweed (Elodea canadensis) is affected by light intensity.
The student placed a cut stem of Elodea into a boiling tube filled with a 0.2% sodium hydrogencarbonate (NaHCO3\text{NaHCO}_3NaHCO3) solution.
State why the student used a sodium hydrogencarbonate solution rather than deionised water in this investigation.
