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Question #46809
The Question
A researcher applies a chemical inhibitor that specifically blocks the H⁺-ATPase pumps on the plasma membrane of companion cells in the mature aerial stem of a typical plant belonging to the family Liliaceae. Which of the following statements correctly identifies the anatomical context of the affected tissue and the primary physiological consequence of this inhibition?
Options
- A.
The vascular bundles are conjoint and closed with an endarch xylem arrangement; the inhibitor will prevent the establishment of a proton gradient, halting the active loading of sucrose.
- B.
The vascular bundles are conjoint and closed with an exarch xylem arrangement; the inhibitor will prevent the establishment of a proton gradient, halting the active loading of sucrose.
- C.
The vascular bundles are conjoint and open with an endarch xylem arrangement; the inhibitor will halt the active loading of sucrose, triggering compensatory secondary growth.
- D.
The stem features scattered, closed vascular bundles; the inhibitor will stop the passive symplastic diffusion of sucrose directly into the sieve tube elements.
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
Companion Cell-Sieve Tube Symport|Glandular Secretion Mechanism|Liliaceae Floral Formula
Why This Question Is Tricky
Common Mistakes
The 'Conceptual Pivot' requires students to simultaneously synthesize structural botany (monocot stem anatomy vs. root anatomy, closed vs. open bundles) and plant physiology (the active nature of phloem loading via proton gradients).
Students often memorize anatomy and transport mechanisms in isolation.
The distractors are designed with 'Common Half-Truths': Option B traps students who confuse stem (endarch) and root (exarch) xylem arrangements; Option C traps those who fail to link Liliaceae to monocot characteristics (closed bundles/no secondary growth); Option D traps those who misunderstand the active energy requirement of the Mass Flow Hypothesis.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Anatomy of Flowering Plants - Class 11 |
| Concept | Companion Cell-Sieve Tube Symport |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |