The document discusses plant physiology and photosynthesis. It explains that green plants use sunlight, carbon dioxide, and water to produce carbohydrates like glucose through photosynthesis. The chemical equation provided shows that carbon dioxide and water are converted to glucose and oxygen. The primary function of leaves is to carry out photosynthesis using chloroplasts, which contain chlorophyll that absorbs sunlight to power the process. Photosynthesis produces carbohydrates and oxygen, while aerobic respiration in animals produces carbon dioxide, water, and energy from carbohydrates.