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Question #47594
The Question
In a C3 plant exposed to elevated CO2 concentrations, a mild environmental stress partially impairs the Oxygen Evolving Complex (OEC), reducing the efficiency of photolysis. Which of the following best describes the immediate physiological consequence and the plant's compensatory metabolic shift?
Options
- A.
Decreased NADPH availability limits the Calvin cycle, prompting a compensatory increase in glycolytic flux for ATP generation, which shifts the light compensation point to a higher light intensity.
- B.
Elevated CO2 completely compensates for the reductant deficit by maximizing RuBisCO carboxylation efficiency, thereby decreasing the light compensation point and reducing the need for glycolysis.
- C.
The chloroplast shifts predominantly to cyclic photophosphorylation to directly synthesize the missing NADPH, thereby maintaining the Calvin cycle and preventing nocturnal redox overload.
- D.
Reduced photolysis increases the internal O2/CO2 ratio, triggering photorespiration to generate compensatory ATP and NADPH to maintain cellular energy homeostasis.
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
Photolysis of Water Stoichiometry|Glycolysis Redox Balance|Compensation Point Logic
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often fall for the 'High CO2 Trap', assuming elevated CO2 universally increases photosynthetic yield.
This question tests the synthesis of Light and Dark reactions, requiring the student to recognize that NADPH (from photolysis) is the ultimate limiting factor for the Calvin cycle.
It also tests the common misconception regarding cyclic photophosphorylation (which only yields ATP, not NADPH) and the energetic cost of photorespiration.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Photosynthesis in Higher Plants - Class 11 |
| Concept | Photolysis of Water Stoichiometry |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |