BioCoach Activity

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. As you view the animation, 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.