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Question #45503
The Question
In an experimental angiosperm model, a targeted mutation completely ablates the formation of the filiform apparatus in the synergids, while all other structures of the embryo sac remain normal. Despite successful pollen germination on the stigma, seed formation fails. Which of the following best explains the physiological and stoichiometric basis for this failure?
Options
- A.
The pollen tube bursts prematurely in the transmitting tissue of the style, preventing gamete delivery and halting both syngamy and triple fusion.
- B.
The directed release of male gametes into the embryo sac fails, disrupting the obligate coupling of syngamy (2n) and triple fusion (3n), thereby preventing the formation of the endosperm nutrient reservoir.
- C.
The generative cell fails to undergo mitosis to form two male gametes, resulting in a solitary syngamy event and an embryo that starves without a 3n endosperm.
- D.
The central cell undergoes spontaneous diploid parthenogenesis to compensate for the lack of triple fusion, creating a 2n endosperm that cannot support the developing zygote.
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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
Synergid Filiform Apparatus|Double Fertilization Stoichiometry|Secondary Productivity
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often memorize that synergids 'guide the pollen tube' but fail to synthesize this with the stoichiometric necessity of double fertilization.
The synergid is the physical site of gamete release; without its gatekeeping function, the 1:1 ratio of syngamy to triple fusion cannot occur.
This tests the student's ability to link a micro-anatomical structure (filiform apparatus) to a macro-physiological outcome (endosperm nutrient reservoir formation and seed viability).
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Sexual Reproduction in Flowering Plants - Class 12 |
| Concept | Synergid Filiform Apparatus |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |