Question

Assertion (A) In the day time, CO2 generated during respiration is used up for photosynthesis.
Reason (R) There is no CO2 release during day.
A. Both A and R are true and R is the correct explanation of A.
B. Both A and R are true, but R is not the correct explanation of A
C. A is true, but R is false
D. A is false, but R is false

Answer 1

The correct option is A. Both A and R are true and R is the correct explanation of A.

Carbon dioxide availability during the day:

• Plants release carbon dioxide during respiration like animals.
• In the daytime, another physiological process, photosynthesis is carried out by the plants.
• In this process of photosynthesis, carbon dioxide reacts with water in the presence of sunlight to form glucose.
• Thus, the carbon dioxide released from preparation is utilised in photosynthesis during the daytime. This is the reason why carbon dioxide is not released during the daytime.

In the given question,

• Carbon dioxide generated during respiration is used up for photosynthesis. The reason is true.
• This is why no carbon dioxide is released during the day.
• Thus, the reason statement correctly explains the assertion statement.

Note- In the nighttime, photosynthesis is halted due to the absence of sunlight, hence carbon dioxide will be released into the atmosphere.

Answer 2

Answer: A. Both A and R are true and R is the correct explanation of A.

Explanation: In respiration, O2 is taken in and CO2 is released while in photosynthesis, CO2 is used up and O2 is released. Both photosynthesis and respiration occurs in plant during daytime. But the rate of photosynthesis is much more than rate of respiration. Thus there is no net release of CO2.