Put a plant in a box that has a dish of Benedict solution (this detects simple sugars) in a sunny area. Then put another box with the same contents in a more shaded area. Let both plants sit for 24 hours and see results. Put bromothymol solution in both containers. You should notice that in a sunny area photosynthesis occurs, in the dark area you should notice that the plant actually releases CO2 rather than O2.
