Question

“All plants give out oxygen during the day and carbon dioxide during the night”. Do you agree with this statement? Give reason.

Answer 1

Hint: Photosynthesis and respiration are two essential processes that occur in plants. These processes have different end products namely oxygen and carbon dioxide respectively. Plants use sunlight to perform photosynthesis. At night, due to no sunlight photosynthesis cannot occur.

Complete answer: Plants are autotrophic organisms and thus make their food on their own by a process called photosynthesis. This process occurs only in the presence of sunlight, carbon dioxide, and water. The process results in the formation of energy which is stored by plants in the form of starch. Along with starch, oxygen is released as a by-product by plants. At night, there is no sunlight, and plants cannot perform photosynthesis. Hence, there is no release of oxygen at night. On the other hand, respiration is a breathing process that takes place continuously throughout the day and night. The process involves taking up oxygen and release of carbon dioxide. Thus, a continuous release of carbon dioxide occurs both during the day and night. The difference is that during the day the released carbon dioxide is taken up again by the plant to use it in the photosynthesis process. Thus, it is thought that during the day plants give oxygen and during the night plants give carbon dioxide. But this statement is not true. So, we can conclude that photosynthesis occurs only during the day but respiration occurs during the day as well as night.

Note: The respiration process is more evident at night as the photosynthesis process ceases. Roots of the plant also respire. The products of photosynthesis are used in the respiration process. Respiration simply occurs for energy production. It converts sugars into energy.