The substances needed by the plant to carry out photosynthesis are: Sunlight (Source: Sun) - This light energy is converted into chemical energy. Water (Source: soil) - The water molecules get split to release oxygen. Chlorophyll (Source: contained in the leaf) - chlorophyll absorbs the light energy and uses it in splitting water molecules into H+ ions and OH- ions. Carbon dioxide (Source: atmosphere) - The CO2combines with the H+ ions to form glucose.