Action Spectrum

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•  Drawing an absorption spectrum for chlorophyll and an action spectrum for photosynthesis

Pigments absorb light as a source of energy for photosynthesis

  • The absorption spectrum indicates the wavelengths of light absorbed by each pigment (e.g. chlorophyll)
  • The action spectrum indicates the overall rate of photosynthesis at each wavelength of light

There is a strong correlation between the cumulative absorption spectra of all pigments and the action spectrum

  • Both display two main peaks – a larger peak at the blue region (~450 nm) and a smaller peak at the red region (~670 nm) 
  • Both display a trough in the green / yellow portion of the visible spectra (~550 nm)

Absorption and Action Spectra

Select Spectrum

Absorption spectrum

Action spectrum

Absorption + Action Spectra