Question

Given below are two statements:
Statement I: In C₃ plants, some O₂ binds to RuBisCO, hence CO, fixation is decreased.
Statement II: In C₄ plants, mesophyll cells show very little photorespiration while bundle sheath cells do not show photorespiration.
In the light of the above statements, choose the correct answer from the options given below:

• A. Both Statement I and Statement II are true
• B. Both Statement I and Statement II are false
• C. Statement I is true but Statement II is false
• D. Statement I is false but Statement II is true

Answer 1

The Correct Option is C

Let's analyze the statements provided: Statement I and Statement II.

Statement I: In C₃ plants, some O₂ binds to RuBisCO, hence CO₂ fixation is decreased.

This statement is true. In C₃ plants, RuBisCO, the enzyme responsible for fixing CO₂, can also bind to O₂, which leads to a process known as photorespiration. This process decreases the overall efficiency of photosynthesis because it results in the oxidation of ribulose bisphosphate and ultimately decreases the amount of CO₂ being fixed into sugars.

Statement II: In C₄ plants, mesophyll cells show very little photorespiration while bundle sheath cells do not show photorespiration.

This statement is false. C₄ plants have evolved a distinctive mechanism to minimize photorespiration by initially fixing CO₂ into a four-carbon compound in the mesophyll cells. This compound is then transported to bundle sheath cells, where CO₂ is released for the Calvin cycle. The process of concentrating CO₂ in the bundle sheath cells allows C₄ plants to effectively prevent photorespiration in these cells. However, it is important to note that mesophyll cells do not significantly limit photorespiration on their own, rather it is the spatial separation and concentration of CO₂ in bundle sheath cells that minimizes this process. Therefore, the implication of minimal photorespiration in mesophyll cells due to their intrinsic properties is incorrect.

Based on the evaluations of the statements, the correct answer is: Statement I is true but Statement II is false.