The action spectrum of photosynthesis shows a high light absorption for violet/blue and orange/red and a low absorption for green/yellow. If we were to set up an experiment where narrow bands of unicolored light were shown on an aquatic plant such as Elodea, and we counted the number of bubbles of oxygen produced as an indicator of photosynthetic rate, how would the graph appear?
A) just like the action spectrum with peaks at violet/blue and orange/red and a trough at yellow/green
B) exactly inverted from the action spectrum with a peak for yellow/green
C) perfectly flat because many wavelengths are used by chlorophyll
D) a descending line because ultra-violet has more energy than infrared
E) There is no way to guess without actually running the experiment.

Question

Quizplus · Accepted Answer

The graph of the number of oxygen bubbles produced would have peaks at the wavelengths of light that are most efficiently absorbed by chlorophyll, which are violet/blue and orange/red. There would be a trough at the wavelengths of light that are least efficiently absorbed, which are green/yellow. This matches the action spectrum of photosynthesis.

The Action Spectrum of Photosynthesis Shows a High Light Absorption