Describe the exchange of gases which takes place in the leaves of a plant (a) during daytime, and (b) at night.

(i) During the daytime, plants carry out both photosynthesis and respiration. During photosynthesis, oxygen is produced some of which is used by the plant leaves and rest is released into the air. During respiration, carbon dioxide is produced which is entirely utilized by leaves for photosynthesis. Leaves even absorb more carbon dioxide from the air for photosynthesis. Thus during the day time, the exchange of gases looks like : Oxygen diffuses out and carbon dioxide diffuses in.

(ii) During the night, photosynthesis doesn’t take place and hence only respiration process occurs in plants. Because of the absence of photosynthesis, oxygen is not produced. For respiration, leaves take in oxygen from the air and release carbon dioxide into the air. Thus during the night time, the exchange of gases looks like : Oxygen diffuses in and carbon dioxide diffuses out.


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