Question

Reason for Plants Give Out Carbon Dioxide at Night
Why do plants give out carbon dioxide at night?

Answer 1

Actually plant give out co2 all the time but in presence of light photosynthesis dominates. Co2 is produced as a byproduct of repiration

Answer 2

Respiration process produces CO2 at night.  And during the day respiration produces CO2 and  the photosynthesis in the presence of chlorophyll  absorbs CO2.  Both are independent processes.