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Question #45980
The Question
During drought stress, Abscisic Acid (ABA) mediates stomatal closure by promoting the efflux of potassium ions (K+) from guard cells. Suppose a mutant plant possesses defective guard cell anion channels that completely prevent the efflux of chloride (Cl-) and malate, while K+ channels and ABA receptors remain fully functional. Which of the following best describes the physiological outcome when this mutant is exposed to severe water stress?
Options
- A.
Complete stomatal closure occurs because K+ efflux alone is sufficient to increase the water potential of guard cells.
- B.
Stomata fail to close completely because the retention of anions maintains a low osmotic potential, preventing the necessary efflux of water.
- C.
Guard cells undergo rapid plasmolysis due to an uncompensated electrical gradient, leading to permanent stomatal closure.
- D.
The plant exhibits a reversed Hamburger phenomenon, actively secreting bicarbonate ions to balance the retained Cl-, resulting in normal closure.
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
ABA|Chloride Shift (Hamburger Phenomenon)|Guard Cell Turgor
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often memorize 'ABA causes K+ efflux to close stomata' (NCERT base) without realizing that osmotic water movement requires a net loss of total solutes (both cations and anions) to alter the water potential gradient.
The trap exploits the failure to recognize the coupled nature of ion fluxes for electrical neutrality and cumulative osmotic effect in guard cell turgor regulation.
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 |