Trapping Light Energy

Chloroplasts contain several different pigments, and these different pigments absorb different wavelengths of light. The photosynthetic pigments of higher plants form two groups:

• the chlorophylls (primary pigments)
• the carotenoids (accessory pigments)

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• Chlorophylls absorb mainly in the red and blue-violet regions of the light spectrum
  • they reflect green light, which is why plants look green
• Carotenoids absorb mainly in the blue-violet region of the spectrum

An absorption spectrum is a graph of the absorbance of different wavelengths of light by a pigment

An action spectrum is a graph of the rate of photosynthesis at different wavelengths of light

• this shows the effectiveness of the different wavelengths, which is related to their absorptiom and to their energy…