The gas produced by plants during photosynthesis is oxygen. This process occurs in the chloroplasts of plant cells, where chlorophyll captures sunlight to convert carbon dioxide and water into glucose and oxygen. The overall reaction can be simplified as: 6 CO₂ + 6 H₂O + light energy → C₆H₁₂O₆ + 6 O₂. The oxygen produced is released into the atmosphere, which is crucial for the survival of most living organisms that rely on it for respiration. Photosynthesis not only supports plant life but also forms the foundation of the food chain and influences the Earth's climate.