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Question #45331
The Question
A dicotyledonous plant, which is obligately dependent on mycorrhizal association, is grown in a sterile, phosphorus-poor soil medium. Observations reveal that while double fertilization occurs successfully, seed development aborts prematurely. Histological analysis shows the proembryo remains confined near the micropylar end. Which of the following best explains the primary developmental failure leading to this aborted embryogeny?
Options
- A.
The absence of fungal symbionts halts the synthesis of sporopollenin, exposing the developing proembryo to fatal desiccation stress.
- B.
Severe phosphorus limitation restricts ATP availability, preventing suspensor elongation and failing to push the proembryo into the endosperm.
- C.
Phosphorus deficiency directly inhibits the triple fusion process, resulting in the complete absence of the primary endosperm nucleus.
- D.
The lack of mycorrhizal nitrogen fixation prevents the synthesis of storage proteins in the cotyledons, causing immediate embryo abortion.
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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
Nutrient sink|Suspensor cell|Endosperm
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: This question tests the ability to de-compartmentalize NCERT chapters.
Students must link the ecological role of Mycorrhiza (Phosphorus absorption) to cellular bioenergetics (ATP synthesis), and finally apply it to a specific anatomical function in embryology (suspensor elongation).
A common misconception is confusing the specific nutrient roles of symbiotic organisms (e.g., assuming mycorrhiza fixes nitrogen) or misattributing the location of structures like sporopollenin.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Sexual Reproduction in Flowering Plants - Class 12 |
| Concept | Embryogeny Directionality |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |