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Question #45988
The Question
In a photomorphogenic mutant plant, the phytochrome system is permanently locked in the inactive Pr form. Researchers observe that even after decapitation (removal of the shoot apex), the lateral buds remain completely dormant. Based on the interplay of light signaling and plant growth regulators, which of the following best explains this observation?
Options
- A.
The absence of Pfr prevents the localized accumulation of cytokinins in the lateral buds, failing to shift the auxin-cytokinin ratio required to break dormancy.
- B.
Decapitation normally removes the source of cytokinins, and without Pfr to synthesize new auxins, the lateral buds cannot initiate growth.
- C.
The permanent Pr state continuously stimulates the de novo synthesis of auxin directly within the lateral buds, maintaining absolute apical dominance.
- D.
Pfr is strictly required for the basipetal transport of auxin; without it, residual auxin remains trapped in the lateral buds despite decapitation.
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
Phytochrome|Shoot_Apical_Meristem|Lateral_Buds
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often memorize 'Decapitation = Lateral bud growth' (NCERT) without understanding the underlying requirement of a shifting Auxin:Cytokinin ratio.
The trap is failing to recognize that removing the inhibitor (Auxin) is insufficient if the promoter (Cytokinin) cannot be activated, which in this advanced scenario is dependent on Pfr-mediated light signaling.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Plant Growth and Development - Class 11 |
| Concept | Phytochrome Interconversion |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |