At what percentage of full midday sunlight does light saturation typically occur for most terrestrial C3 plants?
Answer and explanation
Correct answer: A. 10 percent of full sunlight
- Step 1: Light intensity affects photosynthetic rate linearly at low levels, but plateaus at higher intensities.
- Step 2: Except for plants in deep forest canopies or under dense shade, light is rarely a limiting factor in nature.
- Step 3: Light saturation for most plants occurs at approximately 10% of full sunlight; beyond this, factors like availability become limiting, and excessive light causes photo-oxidation of pigments.
Answer
10 percent of full sunlight
Why not the others: '50 percent of full sunlight' is far above the typical saturation point where photosynthetic rate has already plateaued; '85 percent...' and '100 percent of full sunlight' represent extreme irradiance where photoinhibition and chlorophyll solarization occur rather than saturation.
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