Question

Why plants take carbon dioxide and give out oxygen in day and take oxygen and give out carbondioxide at night?

Answer 1

During day plants need carbon dioxide for photosynthesis and release oxygen. They respire in day also but because of photosynthesis the release of oxygen is more than carbon dioxide.
At night the process of photosynthesis stops because of absence of light, so they only do respiration at night. During respiration they take oxygen and release carbon dioxide