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Question #46208
The Question
A researcher applies a high concentration of exogenous gibberellic acid to a field of rosette plants (e.g., cabbage) to induce early bolting. While rapid internodal elongation is observed, the plants shortly exhibit severe nutrient deficiency, wilting, and metabolic exhaustion, despite optimal soil moisture and light. Based on the principles of plant growth regulators and translocation, which of the following best explains this systemic collapse?
Options
- A.
Gibberellins act as direct antagonists to auxins in the root apical meristem, halting cell division and mineral uptake.
- B.
The bolting shoot becomes an extreme metabolic sink, but the root architecture remains unscaled due to unchanged auxin-cytokinin ratios, leading to resource allocation failure.
- C.
Exogenous gibberellins trigger premature senescence in source leaves by upregulating ethylene biosynthesis, cutting off the supply of photosynthates.
- D.
The rapid elongation of internodes outpaces vascular differentiation, physically rupturing the xylem vessels and preventing the mass flow of water.
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
Root System Architecture|Gibberellin Bolting Logic|Plant Growth and Development
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often memorize PGR functions in isolation (e.g., 'GA causes bolting') without integrating systemic plant physiology.
The trap tests the understanding that a rapid phenotypic shift in one organ (shoot) requires a proportional physiological scaling in another (roots) to maintain the root-shoot ratio.
Failing to recognize that root scaling is Auxin/Cytokinin-dependent, not GA-dependent, leads to missing the source-sink imbalance.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Morphology of Flowering Plants - Class 11 |
| Concept | Root System Architecture |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |