Which Green Plants Give Off Oxygen?

During the day while photosynthesis is the dominant process in leaves, carbon dioxide is taken up from the air and used in the process of making sugars, trees give off Oxygen during the day. At night, when photosynthesis does not occur - no sunlight for energy - respiration does occur, which gives off carbon dioxide just as it does in animals. On balance, though, plants take up much more carbon dioxide in photosynthesis than they give off in respiration.

Plants only absorb carbon dioxide from the atmosphere for its photosynthesis purpose in presence of sunlight. And hence they give off the oxygen. The level of CO2 reduces in the atmosphere with the help of plants and trees.