Plants absorb carbon dioxide (CO2) for photosynthesis. This process allows plants to convert sunlight, water, and CO2 into glucose and oxygen. During photosynthesis, chlorophyll in the plant's leaves captures sunlight, which drives the chemical reactions needed to combine water absorbed by the roots and carbon dioxide from the air. This is crucial for plant growth and development and serves as the foundation of food chains, as plants are primary producers. The oxygen released is essential for the survival of most life forms on Earth, making photosynthesis a vital process in the ecosystem.