Photosynthesis and Starch

We put three different plants under different conditions to demonstrate that both light and carbon dioxide are needed for photosynthesis to occur. A leaf from each plant is taken and heated in ethanol to remove the pigment. These are then cleaned before iodine solution is added to them to see if starch has been produced and photosynthesis has occurred. Biology - Plants - Learning Points. Plants need light, carbon dioxide and water for photosynthesis. Iodine solution is used to test for the presence of starch. Light intensity affects the rate of photosynthesis. Other factors can limit the rate of photosynthesis. A Twig Experiment Film. Let students experience real experiments in lab conditions anywhere, from setup, method all the way through to analysis and real-world application.