Why do plants RELEASE carbon dioxide at night?
During the daytime, plants need carbon dioxide to produce carbohydrates as well as oxygen. Plants , at night, perform the process of respiration in which they take in the oxygen and release carbon dioxide. The process of Photosynthesis which changes CO2 into O2 cannot happen at night in the absence of sunlight. So, Plants take in oxygen for respiration and thus release carbon dioxide in the process.