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Question #45962
The Question
In certain positive photoblastic seeds, applying exogenous Gibberellic Acid (GA) in the dark or under continuous far-red light fails to induce optimal germination, despite GA being the primary hormone responsible for breaking seed dormancy. Based on the synergistic crosstalk between phytochrome and GA signaling, which of the following best explains this phenomenon?
Options
- A.
Exogenous GA is directly converted into dormancy-inducing Abscisic Acid (ABA) in the absence of the active phytochrome Pfr.
- B.
The degradation of DELLA repressor proteins, which is required for GA-responsive gene expression, is highly dependent on Pfr-mediated light signaling pathways.
- C.
Phytochrome Pr competitively binds to GA receptors on the cell membrane, blocking exogenous GA from initiating signal transduction.
- D.
In the absence of red light, the aleurone layer completely lacks the rough endoplasmic reticulum required to synthesize hydrolytic enzymes like alpha-amylase.
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
Gibberellin|Phytochrome|Pr_Pfr_Ratio|Seed_Germination
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often memorize that 'GA breaks seed dormancy' and assume exogenous application is an absolute override.
They fail to distinguish between hormone biosynthesis and hormone sensitivity/signaling.
The misconception is treating the absence of light merely as a lack of endogenous GA, rather than understanding that the light-activated state (Pfr) is also required to sensitize the seed to GA by facilitating the removal of DELLA repressors.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Plant Growth and Development - Class 11 |
| Concept | Gibberellin Bolting Logic |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |