The gas that plants release as a byproduct of photosynthesis is oxygen. During photosynthesis, plants convert carbon dioxide and sunlight into glucose while releasing oxygen into the atmosphere. This process occurs primarily in the chloroplasts of plant cells and is essential for sustaining life on Earth. Oxygen produced during photosynthesis is critical for the respiration of most living organisms, serving as a vital component in energy production. The balance of oxygen and carbon dioxide in the atmosphere is crucial for overall ecosystem health.