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Question #47626
The Question
In a transgenic C4 plant, a targeted mutation disrupts the normal orientation of the phragmoplast during cytokinesis in developing leaf primordia. This prevents the periclinal cell divisions required to form concentric cellular layers around the vascular bundles. Which of the following physiological outcomes is most likely to be observed in this mutant plant under high light intensity and high temperature?
Options
- A.
The spatial isolation between primary carboxylation and the C3 cycle is abolished, causing RuBisCO to exhibit high oxygenase activity.
- B.
The plant will transition to Crassulacean Acid Metabolism (CAM) by temporally separating PEP carboxylase and RuBisCO activity.
- C.
Primary CO2 fixation will cease entirely because PEP carboxylase requires a low O2 environment to function.
- D.
The plant will maintain its photosynthetic yield by shifting the decarboxylation of malic acid to the mesophyll chloroplasts.
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Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Evolutionary_Exception
Tackle problems where standard rules evolve or change based on specific environmental constraints.
Concepts Behind This Question
PEP_Carboxylase|Cytokinesis|Bundle_Sheath_Differentiation
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Understanding that C4 photosynthetic efficiency is not merely a biochemical adaptation (presence of PEPcase) but fundamentally an anatomical one (Kranz anatomy).
Students often fail to link cellular developmental processes (cytokinesis/phragmoplast orientation) to macroscopic physiological efficiency (avoidance of photorespiration).
The trap in Option C tests the misconception that PEPcase, like RuBisCO, is affected by oxygen.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Photosynthesis in Higher Plants - Class 11 |
| Concept | C4 Pathway Efficiency |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |