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Question #45974
The Question
Ethylene induces a characteristic 'triple response' in dicot seedlings to help them navigate mechanical stress, such as a hard soil crust. A researcher isolates a mutant plant with a dominant mutation in the ETR1 gene, rendering its receptors completely insensitive to ethylene. If these mutant seeds are germinated deep under a hard soil crust, which of the following represents the most likely physiological outcome?
Options
- A.
The seedlings will fail to form an apical hook and swell their axis, resulting in fatal mechanical damage as they attempt to grow vertically.
- B.
The seedlings will exhibit constitutive horizontal growth and axis swelling even before encountering the mechanical stress of the soil crust.
- C.
The seedlings will successfully overcome the mechanical stress by hyper-elongating their hypocotyls through a compensatory gibberellin pathway.
- D.
The seedlings will demonstrate normal apical hook formation but fail to initiate horizontal growth, as the ETR1 gene exclusively regulates gravitropism.
Check Your Answer
Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Evolutionary_Exception
Tackle problems where standard rules evolve or change based on specific environmental constraints.
Concepts Behind This Question
ETR1|Signal Transduction|Ethylene
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: This question tests the integration of Plant Growth and Development (NCERT) with basic genetic principles.
Students often memorize the 'triple response' but fail to apply its ecological necessity (survival under mechanical stress).
The trap lies in confusing the outcome of an 'insensitive' mutation (failure to respond, leading to death under stress) with a 'constitutive' mutation (responding even without the hormone).
Option B serves as a high-level distractor for students who misunderstand the negative regulatory nature of the ETR1 receptor.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Plant Growth and Development - Class 11 |
| Concept | Ethylene Triple Response |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |