Final answer:
Photosynthesis requires sunlight, carbon dioxide, and water as starting reactants. These substances combine to produce glucose and oxygen. Carbon dioxide is obtained from the atmosphere, and water is absorbed by the roots of the plant.
Step-by-step explanation:
Photosynthesis requires sunlight, carbon dioxide, and water as starting reactants. During the process, these substances combine to produce glucose, a carbohydrate, and oxygen as a waste product. Carbon dioxide is obtained from the atmosphere through diffusion, while water is absorbed by the roots of the plant. Sunlight is absorbed by chlorophyll in the chloroplasts of the leaf cells, where photosynthesis takes place.