The part of the plant primarily responsible for photosynthesis is the leaf. Leaves contain specialized cells known as mesophyll cells, which house chloroplasts, the organelles that perform photosynthesis. Chloroplasts contain chlorophyll, the green pigment that captures sunlight. During photosynthesis, plants convert light energy, water, and carbon dioxide into glucose and oxygen. This process is crucial for plant growth, providing the energy needed to produce organic compounds, and it plays a significant role in the Earth's ecosystem, as it supplies oxygen and organic material for other organisms in the food chain.