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Photosynthesis
Concept 3: The Action Spectrum for
Photosynthesis
A classic experiment reveals which
wavelengths work best for photosynthesis. The pigment molecules in
photosynthetic organisms absorb specific wavelengths of light. In
1883, Thomas Engelmann devised an experiment to learn which
wavelengths (colors) of light were the most effective in carrying
out photosynthesis in the green alga Spirogyra.
Note that oxygen-dependent bacteria produce a "living
graph" as they accumulate near the parts of the alga that are
illuminated with red and blue light. Those are the wavelengths that
work best for photosynthesis, which is why the alga released more
oxygen in the red and blue light.
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