The primary gas released by plants during photosynthesis is oxygen. During this biological process, plants convert carbon dioxide from the atmosphere and water from the soil into glucose and oxygen, using sunlight as energy. Photosynthesis occurs in the chloroplasts of plant cells, where the green pigment chlorophyll captures light energy. This process not only provides energy for the plant itself but also generates oxygen, which is crucial for the survival of aerobic organisms, including humans. The role of plants in producing oxygen emphasizes their importance in maintaining ecological balance and supporting life on Earth.