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

Analyzing provided statements: Statement I and Statement II.

Statement I: In C₃ plants, O₂ binding to RuBisCO reduces CO₂ fixation.

This statement is true. In C₃ plants, RuBisCO, the enzyme responsible for CO₂ fixation, also binds O₂, initiating photorespiration. This process reduces photosynthetic efficiency by oxidizing ribulose bisphosphate and consequently lowering CO₂ assimilation into sugars.

Statement II: In C₄ plants, mesophyll cells exhibit minimal photorespiration, and bundle sheath cells show none.

This statement is false. C₄ plants minimize photorespiration through a mechanism involving initial CO₂ fixation into a four-carbon compound in mesophyll cells. This compound is then transported to bundle sheath cells, releasing CO₂ for the Calvin cycle. This spatial CO₂ concentration in bundle sheath cells effectively prevents photorespiration there. Mesophyll cells themselves do not intrinsically limit photorespiration; it is the CO₂ concentrating mechanism in bundle sheath cells that achieves this. Thus, the notion of minimal photorespiration in mesophyll cells due to their inherent properties is inaccurate.

Based on these evaluations, the correct conclusion is: Statement I is true but Statement II is false.