The process through which plants release oxygen into the atmosphere is called photosynthesis. During this process, plants, algae, and some bacteria convert light energy, typically from the sun, into chemical energy stored in glucose. They absorb carbon dioxide from the air and water from the soil, using chlorophyll to capture light energy. The overall reaction produces glucose and oxygen as byproducts, contributing to the atmosphere's oxygen levels. This process is vital for maintaining life on Earth, as it forms the basis of the food chain and influences global carbon cycling.