Photosynthesis is the chief function of leaves. The word photosynthesis means putting together with light. Green plants use energy from light to combine carbon dioxide and water to make food. All our food comes from this important energy-converting activity of green plants.
Light energy is converted to chemical energy and is stored in the food that is made by green plants.
Animals eat the plants, and we eat animal products as well as plants. The light used in photosynthesis is absorbed by a green pigment called chlorophyll. Each food-making cell in a plant leaf contains chlorophyll in small bodies called chloroplasts. In chloroplasts, light energy causes water drawn from the soil to split into molecules of hydrogen and oxygen. In a series of complicated steps, the hydrogen combines with carbon dioxide from the air, forming a simple sugar.