Before You Begin
Question #47630
The Question
In a plant tissue culture experiment, a high Auxin to Cytokinin ratio is applied to induce rapid root differentiation and cell elongation. Molecular analysis of these non-photosynthetic cells reveals a significant, simultaneous upregulation of the enzyme PEP Carboxylase (PEPC). Which of the following best explains the metabolic necessity of this auxin-induced PEPC expression and its energetic consequence?
Options
- A.
It replenishes TCA cycle intermediates (anaplerotic flux) required for rapid biosynthesis, leading to increased competition for ATP between metabolite regeneration and cell wall expansion.
- B.
It initiates a localized C4-like pathway to prevent photorespiration in the differentiating roots, thereby conserving ATP for rapid cell division.
- C.
It directly decarboxylates oxaloacetate to release CO2, which acts as a gaseous growth regulator synergistic to auxin, decreasing overall ATP consumption.
- D.
It diverts phosphoenolpyruvate from glycolysis to synthesize ethylene, which counteracts cytokinin and promotes root elongation while generating excess ATP.
Check Your Answer
Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Comparative_Analysis
Sharpen your ability to evaluate multiple scenarios and distinguish between competing potential answers.
Concepts Behind This Question
Cytokinin-Auxin_Ratio|PEP_Regeneration_Energy_Cost|Absolute_vs_Relative_Growth
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students heavily associate PEP Carboxylase exclusively with C4/CAM photosynthesis in leaves.
The trap exploits this by offering a C4-related distractor (Option B).
The core synthesis requires understanding PEPC's non-photosynthetic, anaplerotic role in replenishing TCA cycle intermediates during rapid, auxin-induced growth, linking Plant Growth Regulators with Cellular Respiration.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Photosynthesis in Higher Plants - Class 11 |
| Concept | PEP Regeneration Energy Cost |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |