Plants take in oxygen and give out carbon dioxide during respiration all the time. Why do we then say that plants supply oxygen to the air?

Requirement of carbon dioxide in plants:

1. During the day, there is a higher requirement of carbon dioxide as it is the reagent used for photosynthesis giving out oxygen as the product.
   
2. ​This is why plants release oxygen during the day when photosynthesis occurs as the production exceeds the amount of oxygen required by respiration.
   
3. During the night, plants take oxygen and release carbon dioxide due to respiration only.
4. This is why plant acts as a major supplier of oxygen to the atmosphere.