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Question #46807
The Question
During a period of severe drought, a monocot plant exhibits inward rolling of its leaves and a simultaneous cessation of sucrose translocation from the leaves to the roots. Based on the principles of plant anatomy and the Pressure Flow Hypothesis, which of the following statements correctly explains this dual phenomenon?
Options
- A.
Flaccidity of bulliform cells reduces the exposed surface area-to-volume ratio to conserve water, while the inability to draw water from the xylem prevents the buildup of high turgor pressure in the source sieve tubes, halting mass flow.
- B.
Turgidity of bulliform cells causes leaf rolling to minimize transpiration, and the resulting stomatal closure directly inhibits the ATP-dependent active loading of sucrose into companion cells.
- C.
Flaccidity of bulliform cells increases the surface area-to-volume ratio to maximize heat dissipation, while low leaf water potential reverses the direction of phloem mass flow toward the source.
- D.
Loss of turgor in bundle sheath cells induces leaf rolling, and the subsequent drop in solute potential at the sink decouples the pressure-flow mechanism by preventing phloem unloading.
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|Bulliform Cell Function|Phytochrome Interconversion
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often memorize that 'phloem loading is an active process' but fail to realize that the actual driving force for mass flow is the hydrostatic (turgor) pressure gradient, which is entirely dependent on water availability from the xylem.
Additionally, confusing the turgid vs. flaccid state of bulliform cells during leaf rolling is a classic NCERT factual trap.
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 |