Given below are two statements:

Statement I: In C₃ plants, some O₂ binds to RuBisCO, hence CO₂ 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:

The correct option is: Statement I is true but Statement II is false.

Analysis of Statement I:
In C₃ plants, the carbon dioxide fixation is catalyzed by the enzyme RuBisCO (Ribulose bisphosphate carboxylase-oxygenase). RuBisCO has a dual affinity, meaning it can bind to both CO₂ and O₂ depending on their relative concentrations. When the concentration of O₂ increases, some O₂ binds to RuBisCO instead of CO₂. This initiates photorespiration, a process in which RuBP is oxidized, leading to the loss of fixed carbon as CO₂ without synthesizing any sugar or ATP. As a result, the overall rate of CO₂ fixation decreases. Hence, Statement I is true.

Analysis of Statement II:
C₄ plants have evolved a specialized anatomy (Kranz anatomy) to entirely avoid photorespiration. In C₄ plants, the enzyme RuBisCO is completely absent in the mesophyll cells and is restricted only to the bundle sheath cells. The mesophyll cells contain PEP carboxylase (PEPCase), which has no affinity for oxygen and carries out the initial CO₂ fixation. The fixed carbon is then transported as a C₄ acid to the bundle sheath cells, where it is decarboxylated to release a high concentration of CO₂ directly around RuBisCO. This high localized concentration ensures that RuBisCO functions exclusively as a carboxylase. Therefore, photorespiration is completely absent in C₄ plants (meaning neither mesophyll cells nor bundle sheath cells perform photorespiration). Because Statement II asserts that mesophyll cells show very little photorespiration, it is false.

Conclusion:
Statement I is true, whereas Statement II is false.