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Question #46783
The Question
During pollen-pistil interaction in angiosperms, the filiform apparatus of the synergids plays a crucial role in guiding the pollen tube into the embryo sac. If a localized environmental stress significantly alters the pH and ionic strength of the synergid microenvironment, fertilization often fails despite successful pollen tube growth through the style. Which of the following best explains this specific reproductive failure based on molecular recognition principles?
Options
- A.
The altered pH disrupts the zwitterionic patches of chemotropic proteins secreted by the filiform apparatus, preventing molecular recognition by the pollen tube.
- B.
The ionic shift causes the generative cell to undergo premature mitosis, physically blocking the pollen tube before it reaches the micropyle.
- C.
The change in pH degrades the sporopollenin of the growing pollen tube tip, causing it to burst prematurely outside the embryo sac.
- D.
The altered ionic strength reverses the polarity of the egg apparatus, directing the pollen tube towards the antipodal cells at the chalazal end.
Check Your Answer
Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Regulatory_Failure
Understand how NOT, EXCEPT, and logical constraints are used to manipulate exam results.
Concepts Behind This Question
Amino Acid Zwitterion Equilibrium | Synergid Filiform Apparatus | Pollen Wall Chemistry
Why This Question Is Tricky
Common Mistakes
The Conceptual Pivot lies in understanding the biochemical nature of 'chemotropism' mentioned in NCERT.
Students often memorize that the filiform apparatus guides the pollen tube but fail to synthesize that this is a protein-receptor interaction highly dependent on pH and ionic gradients.
The question also tests structural misconceptions, specifically the 'sporopollenin trap', where students incorrectly associate the highly resistant sporopollenin with the actively growing, permeable pollen tube tip.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Biomolecules - Class 11 |
| Concept | Amino Acid Zwitterion Equilibrium |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |