6b. How might elevated CO2 concentration affect the light saturation curve of a plant?

'D' is the correct answer since it shows an increase in the light saturation point and maximal rate of photosynthesis. With more CO2 available, photosynthesis can take advantage of higher light levels. The light compensation point and maximal rate of photosynthesis are higher.

Some people might mistakenly select 'A'; however, a careful analysis shows this to be incorrect. Higher CO2 levels will only affect the rate of photosynthesis at the highest light levels. Curve 'A' shows photosynthesis rate is also increased at low light levels. This would not be expected, since at low light levels the overall rate of photosynthesis will be determined, as before, by the availability of light.

 

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