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Question #45979
The Question
In many perennial plants, as days become progressively shorter during autumn, the shoot apices cease vegetative growth and floral transition, instead forming winter buds. Which of the following best explains the photoperiodic and hormonal crosstalk mediating this specific transition?
Options
- A.
A prolonged dark period increases the Pfr:Pr ratio, which antagonizes Florigen and promotes Abscisic Acid (ABA) mediated dormancy.
- B.
A prolonged dark period decreases the Pfr:Pr ratio, overriding the floral transition signal and triggering Abscisic Acid (ABA) induced bud dormancy.
- C.
Accumulation of Pr during short days directly stimulates Gibberellic Acid (GA) synthesis, which acts antagonistically to ABA to induce dormancy.
- D.
Continuous exposure to far-red light during the shorter days converts Pr to Pfr, which acts as a stress signal to synthesize Abscisic Acid (ABA).
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
Phytochrome Interconversion|ABA|Florigen
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Linking the direction of phytochrome dark reversion (Pfr to Pr) with antagonistic hormonal responses.
The trap relies on students confusing which phytochrome form accumulates in the dark (Pr, not Pfr) and mixing up the roles of ABA (dormancy inducer) and GA (dormancy breaker).
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Plant Growth and Development - Class 11 |
| Concept | Abscisic Acid (ABA) Antagonism |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |