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Question #47601
The Question
DCMU (Diuron) is a potent herbicide that binds to the Q_B binding site of the D1 protein in Photosystem II. If an actively photosynthesizing C_3 plant is treated with DCMU, all of the following physiological events will occur, EXCEPT:
Options
- A.
Arrest of oxygen evolution in the thylakoid lumen due to the lack of oxidized P680.
- B.
Cessation of NADP+ reduction in the stroma due to the interruption of the Z-scheme.
- C.
Accumulation of reduced Plastoquinone (PQH2) in the thylakoid membrane.
- D.
Eventual halting of RuBP regeneration in the Calvin cycle despite open stomata.
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
Photosystem II|Plastoquinone|ATP-Synthase|DCMU
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Tracing the exact sequence of the Z-scheme.
Students often know DCMU 'stops photosynthesis' but fail to deduce the redox state of intermediates.
The trap relies on the principle that blocking an electron transport pathway causes a buildup of the intermediate before the block and a depletion of the reduced intermediate after the block.
Since PQ is downstream of the block, it cannot be reduced to PQH2.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Photosynthesis in Higher Plants - Class 11 |
| Concept | Chemiosmotic ATP Synthesis Logic |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |