The statement is wrong because plants respire every time and expel out Carbon dioxide every time but they give out oxygen only in the daytime as photosynthesis process can take place only in the presence of sunlight. In plants, the exchange of gases, i.e. carbon dioxide and oxygen takes place by diffusion depending upon the environmental conditions and the requirements of the plants:
i. During the day, carbon dioxide is required by the plants for the process of photosynthesis. Therefore, the gas released is oxygen.
ii. But at night, due to the lack of sunlight, no photosynthesis takes place, and thus carbon dioxide formed during respiration is not used up, so it is released.