The part of a plant most responsible for photosynthesis is the leaf, specifically in structures called chloroplasts. Leaves contain chlorophyll, the pigment that captures light energy, which is then used to convert carbon dioxide and water into glucose and oxygen. This process is vital for the plant's energy production and supports life on Earth by contributing to the oxygen supply and forming the base of the food chain. The efficiency of photosynthesis in leaves is fundamental to plant growth and ecosystem health.