Green plant do not give out CO₂ during day time because they

Green plant do not give out CO₂ during day time because they consume it in photosynthesis.
During daylight hours, plants take in carbon dioxide and release oxygen through photosynthesis, and at night only about half that carbon is then released through respiration. Plants typically absorb CO₂ and release oxygen, but they also “exhale” CO₂, particularly at night, when photosynthesis ceases due to the lack of sunlight.