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Question #45976
The Question
A C3 plant under severe drought stress exhibits a sharp increase in endogenous Abscisic Acid (ABA) levels. While this response is critical for preventing desiccation, it paradoxically accelerates the loss of previously fixed carbon and drains cellular energy. Which of the following biochemical sequences best explains this phenomenon?
Options
- A.
ABA-induced stomatal closure lowers the intercellular CO2 to O2 ratio, favoring RuBisCO's oxygenase activity and resulting in the release of previously fixed CO2 from the mitochondria.
- B.
ABA promotes massive K+ influx into guard cells, causing flaccidity and stomatal closure, which subsequently halts the light reactions and prevents ATP synthesis.
- C.
The accumulation of ABA directly induces the synthesis of phosphoglycolate in the chloroplast stroma, bypassing the Calvin cycle to dissipate excess excitation energy.
- D.
Stomatal closure prevents the exit of O2 produced by the photolysis of water at Photosystem I, which competitively inhibits RuBisCO and permanently denatures the enzyme.
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
ABA|Photorespiration Metabolic Cost|RUBISCO
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often view ABA's role in drought stress purely as a beneficial survival mechanism (water conservation) without recognizing the severe metabolic trade-off (photorespiration) it forces upon C3 plants.
The distractors heavily utilize classic NEET traps: reversing ion flow direction (K+ influx vs efflux), confusing 'Directly' vs 'Indirectly', and misidentifying the exact location of a process (PS I vs PS II for oxygen evolution).
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 |