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Question #46000
The Question
A transgenic plant is engineered with a loss-of-function mutation in its Abscisic Acid (ABA) receptors. Paradoxically, instead of delayed abscission, the plant exhibits premature fruit drop. Which of the following best explains the hormonal cross-talk and enzymatic activity at the abscission zone in this mutant?
Options
- A.
Unchecked ethylene activity leads to premature induction of cellulases and pectinases, as the homeostatic brake provided by ABA is lost.
- B.
The absence of ABA signaling directly reverses the auxin gradient, stimulating the rapid dissolution of the middle lamella.
- C.
Ethylene synthesis is completely inhibited, causing mechanical shearing of the fruit stalk due to increased tissue rigidity.
- D.
Complete failure of abscission layer formation occurs, as ABA is the primary and sole trigger for abscission in angiosperms.
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
Abscisic Acid (ABA) Antagonism|Ethylene|Cytokinin
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often memorize the NCERT line 'ABA promotes abscission' and incorrectly assume that lacking ABA receptors would completely halt abscission (Option D).
The trap relies on failing to recognize the antagonistic cross-talk between ABA and ethylene at the enzymatic level.
While ABA promotes overall senescence, it acts as a homeostatic rheostat at the abscission zone to prevent premature cellulase activity driven by ethylene.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Plant Growth and Development - Class 11 |
| Concept | Senescence vs Abscission |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |