The gas released by plants during photosynthesis is oxygen. During this vital process, plants, algae, and some bacteria convert carbon dioxide and water into glucose and oxygen, using sunlight as energy. Chlorophyll, the green pigment in plant leaves, captures light energy needed for this transformation. The released oxygen is essential for most living organisms on Earth as it provides the necessary gas for respiration. Photosynthesis not only sustains the plant itself but also plays a crucial role in maintaining the Earth's atmosphere and supporting life by producing the oxygen we breathe.