Action and Absorption Spectra

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Chlorophyl A and B are a photosynthetic pigments and are always present in chloroplasts. In addition to chlorophyl, chloroplasts have accessory pigments.

Each different photosynthetic pigment absorb different wavelengths of light less or more.

Carotenoids are an example of accessory photosynthetic pigments, which stand to extend the range of wavelengths of light plants can use to photosynthesize as each photosynthetic pigment will be able to absorb a different range of wavelengths.

The graph above is called an absorption graph, and graphs the amount of light absorbed by the molecules for the visible light spectrum.

Below is an absorption and action spectrum overlayed. The semitransparent graphs are the absorption spectrum of multiple photosynthetic pigments, and the fully colored line (the action spectrum) plots the rate of photosynthesis at different wavelengths of lights.

Plants photosynthesize at all other colors other than green, as they hold multiple pigments that are sensitive to multiple points on the color spectrum, demonstrated by the peaks in the absorption spectra.