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Question #45502
The Question
A researcher applies colchicine to the sporogenous tissue of a diploid angiosperm (2n = 14) prior to microsporogenesis. The mature pollen grains produced are then dusted onto the stigma of a normal, untreated plant of the same species. Which of the following best describes the subsequent cytological and physiological events?
Options
- A.
The pollen grains will possess 14 chromosomes, but the pollen tube will likely fail to discharge male gametes into the synergid due to altered chemotropic interaction with the filiform apparatus.
- B.
The pollen grains will possess 28 chromosomes, and fertilization will yield a tetraploid zygote and a pentaploid primary endosperm nucleus (PEN).
- C.
The pollen grains will possess 7 chromosomes, but the generative cell will fail to undergo mitosis, resulting in syngamy without triple fusion.
- D.
The pollen grains will possess 14 chromosomes, and successful double fertilization will result in a triploid (3n = 21) zygote and a tetraploid (4n = 28) PEN.
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
Synergid Filiform Apparatus|Microsporogenesis Ploidy Shift|Meiosis
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often mechanically calculate ploidy outcomes for artificial polyploidy (e.g., 2n male gamete + n egg = 3n zygote) without considering the physiological barriers of pollen-pistil interaction.
The trap (Option D) relies on students doing the math correctly but forgetting that the filiform apparatus relies on precise Ca2+ gradients, which are disrupted by the altered metabolism of polyploid pollen tubes, leading to pre-fertilization failure.
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 |