Chlorophyll was extracted from the leaf to test for the presence of products from photosynthesis. After detaching the leaf, all chemical reactions need to be stopped to accurately analyze what was produced during photosynthesis. Iodine is used to test for starch - a blue-black color indicates starch is present. While the leaf initially showed no color change with iodine, it later turned blue-black, suggesting starch was present and photosynthesis had occurred, though this test does not indicate starch is the first product formed. Other products besides starch may be revealed through different tests.