The following statements are made regarding photosynthesis in a mutant maize (C₄ plant) that lacks functional bundle sheath chloroplasts:
A. Photorespiration would remain low due to PEP carboxylase activity.
B. Calvin cycle would be severely compromised, reducing sugar production.
C. Carbon fixation would shift entirely to mesophyll cells without yield penalty.
D. CO₂ concentration around Rubisco would increase dramatically.
Which one of the following options is a combination of all INCORRECT statements?

Correct option is D

Correct Answer:
(d) A, C and D
Explanation:
In C₄ plants, bundle sheath chloroplasts are essential for concentrating CO₂ around Rubisco and running the Calvin cycle efficiently.
If bundle sheath chloroplasts are non-functional, the C₄ CO₂-concentrating mechanism collapses.
A is incorrect: PEP carboxylase alone cannot keep photorespiration low without functional bundle sheath cells.
B is correct: The Calvin cycle occurs mainly in bundle sheath cells; its loss severely reduces sugar production.
C is incorrect: Shifting fixation to mesophyll cells would incur a major yield penalty due to Rubisco oxygenation.
D is incorrect: CO₂ concentration around Rubisco would decrease, not increase.
Information Booster :
· Spatial separation of CO₂ fixation and Calvin cycle is key to C₄ efficiency.
· Bundle sheath cells provide a high-CO₂, low-O₂ environment for Rubisco.
· Disruption of this anatomy makes C₄ plants behave more like inefficient C₃ plants.
· Photorespiration rises sharply when CO₂ concentration mechanisms fail.
Additional Information (Incorrect Options):
Option (a): Incorrect because B is actually a correct statement.
Option (b): Incorrect since B should not be included.
Option (c): Incomplete because statement A is also incorrect.