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Question #46806
The Question
A researcher treats a mature, actively photosynthesizing leaf of a plant with a dilute solution of cyanide. Which of the following represents the most accurate sequence of events leading to the cessation of Munch's mass flow of photoassimilates?
Options
- A.
Inhibition of cytochrome c oxidase -> Depletion of ATP -> Failure of H+-ATPase in companion cells -> Cessation of sucrose-H+ symport -> Loss of hypertonic condition in sieve tubes.
- B.
Inhibition of photosystem II -> Cessation of photophosphorylation -> Depletion of ATP -> Failure of active sucrose loading -> Plasmolysis of sieve tube elements.
- C.
Inhibition of cytochrome c oxidase -> Depletion of ATP -> Failure of active sucrose diffusion through plasmodesmata -> Loss of turgor pressure gradient.
- D.
Inhibition of ATP synthase -> Depletion of ATP -> Failure of K+ ion efflux in guard cells -> Stomatal closure -> Cessation of phloem mass flow.
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
Companion Cell-Sieve Tube Symport|Substrate Level Phosphorylation (SLP) Sites|Terminal Electron Acceptor
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Bridging Cell Respiration (Cyanide's specific inhibition of Complex IV) with Plant Transport (the molecular mechanism of active phloem loading).
The trap lies in confusing the exact target of the metabolic poison and the specific nature of the transport mechanism (secondary active transport via symport, rather than direct active diffusion or stomatal regulation).
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 |