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Question #46733
The Question
A plant geneticist engineers a mutant where the genes encoding Plasma membrane Intrinsic Proteins (PIPs), a major class of aquaporins, are completely silenced specifically in the guard cells. If this mutant plant is exposed to blue light, which normally induces stomatal opening, which of the following best describes the immediate physiological state of its guard cells?
Options
- A.
Active influx of K+ occurs, solute potential (Ψs) becomes highly negative, but turgor pressure (Ψp) remains near zero.
- B.
Active influx of K+ is inhibited due to the lack of water channels, preventing any change in solute potential (Ψs) or turgor pressure (Ψp).
- C.
Active influx of K+ occurs, solute potential (Ψs) becomes less negative, and the cells become turgid via simple diffusion of water.
- D.
Efflux of K+ occurs to compensate for the lack of water channels, leading to a highly positive water potential (Ψw).
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Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Evolutionary_Exception
Tackle problems where standard rules evolve or change based on specific environmental constraints.
Concepts Behind This Question
Stomatal Apparatus Anatomy|Active vs Passive Gradient Logic
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Decoupling active ion transport from passive water movement.
Students often assume that if a solute gradient is created, water will inevitably and immediately follow to create turgor.
This question tests the understanding that while the thermodynamic driving force (ΔΨw) is established by active K+ transport, the actual hydraulic conductance (rate of water entry) relies heavily on aquaporins.
Without them, the cell experiences 'internal wilting'—high nutrient/ion status but zero turgor.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Cell – The Unit of Life - Class 11 |
| Concept | Active vs Passive Gradient Logic |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |