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Question #46215
The Question
A plant physiologist applies a high concentration of exogenous GA3 to a rosette plant (e.g., beet) to induce bolting. The plant exhibits rapid internodal elongation but subsequently undergoes premature leaf yellowing and senescence prior to flowering. Which of the following physiological imbalances best explains this systemic failure?
Options
- A.
The rapid shoot biomass expansion outpaced root meristematic differentiation, causing a severe hydraulic and nutrient deficit that induced ABA-mediated senescence.
- B.
Exogenous GA3 directly inhibited the synthesis of ethylene in the shoot apical meristem, preventing normal internodal maturation and leading to structural collapse.
- C.
The induced bolting caused a sudden shift of the sink from the roots to the shoot, directly triggering cytokinin-induced apoptosis in the older leaves.
- D.
GA3 application prematurely activated floral meristem identity genes, causing the plant to bypass the vegetative phase and undergo immediate monocarpic senescence.
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
Gibberellin|Root Meristem|Shoot Apical Meristem
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often rote-memorize 'GA3 causes bolting' but fail to integrate whole-plant physiology (the root-shoot ratio).
The trap is treating bolting as an isolated shoot event rather than a coordinated systemic process.
The question tests the application of source-sink dynamics and the antagonistic relationship between growth promoters (GA) and stress hormones (ABA) when physiological decoupling occurs.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Morphology of Flowering Plants - Class 11 |
| Concept | Root Region Differentiation |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |