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Question #47529
The Question
In a gametophytic self-incompatible angiosperm, the pollen-pistil interaction involves a dynamic chemical dialogue. Researchers hypothesize that stylar S-glycoproteins (products of the S-allele) arrest pollen tube growth by acting as competitive inhibitors to the pollen tube's wall-degrading enzymes (e.g., pectinases). Based on this biochemical model and NCERT principles, which of the following statements is INCORRECT?
Options
- A.
Self-incompatibility is a genetically controlled mechanism that prevents both autogamy and geitonogamy by inhibiting pollen tube growth in the pistil.
- B.
As competitive inhibitors, the stylar S-glycoproteins would increase the apparent Km of the pollen pectinases without altering their Vmax.
- C.
This incompatibility mechanism successfully prevents double fertilization by ensuring the pollen tube never reaches the filiform apparatus of the synergids.
- D.
The competitive binding of S-glycoproteins permanently denatures the active sites of pollen enzymes, making the arrest of pollen tube growth irreversible regardless of substrate concentration.
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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
Angiosperm Double Fertilization|Rubisco Dual Functionality|Secondary Productivity
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Integrating Plant Reproduction with Biomolecules (Enzyme Kinetics).
Students often memorize that self-incompatibility 'permanently stops' pollen tubes, leading them to incorrectly associate this macroscopic physiological arrest with the irreversible denaturation of enzymes.
However, competitive inhibition is strictly reversible and alters Km, not enzyme structural integrity.
The trap relies on confusing the final biological outcome (failure to fertilize) with the microscopic biochemical mechanism (reversible competitive inhibition).
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Plant Kingdom - Class 11 |
| Concept | Angiosperm Double Fertilization |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |