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Question #45972
The Question
A dicot seedling germinating under heavy soil cover typically exhibits the ethylene-mediated 'triple response'. However, if the seedling is simultaneously exposed to extreme high-temperature stress and severe desiccation, the triple response fails to manifest, and growth is completely arrested. Which of the following best explains the physiological basis of this 'metabolic stalemate'?
Options
- A.
Thermal stress inhibits ACC-oxidase, preventing ethylene synthesis, while stress-induced Abscisic Acid (ABA) antagonizes growth to enforce dormancy.
- B.
High temperatures accelerate ACC to ethylene conversion, but stress-induced ABA competitively binds to ethylene receptors to halt growth.
- C.
Desiccation triggers a massive release of Gibberellins, which overrides the ethylene-induced radial swelling to promote rapid vertical elongation.
- D.
Extreme heat denatures ethylene receptors in the apical hook, while ABA promotes the horizontal growth of the seedling to escape heat.
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
Ethylene|1-Aminocyclopropane-1-carboxylic acid (ACC)|Diapause|Aestivation
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often memorize isolated hormone functions ('mechanical stress = ethylene = triple response' and 'water stress = ABA = dormancy').
The trap lies in understanding the antagonistic hierarchy and biosynthetic bottlenecks when multiple stresses overlap.
Students must recognize that survival cues (ABA) override developmental cues (Ethylene), and that thermal stress actively blocks ethylene production via ACC-oxidase inhibition, rather than just receptor competition.
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 |