CBSE Class 10 Answered

Photosynthesis and respiration are two different processes.

Photosynthesis takes place in the light which is available only during the daytime.  In this process, plants take in carbon dioxide and give out oxygen. However, at night, in the absence of sunlight, photosynthesis does not occur. Hence, there is no release of oxygen during the night.

Respiration is a continuous process which takes place during the day and also at night. In this process, plants take in oxygen and give out carbon dioxide. Hence, there is a continuous release of carbon dioxide during the daytime and nighttime. However, during the daytime, the waste carbon dioxide released during respiration is utilized by the plants for photosynthesis.

As a result, it appears as if plants give out oxygen only during the day and carbon dioxide during night. However, respiration occurs continuously day in and day out.