[Campbell Biology P.243] Why is the action spectrum for photosynthesis Figure 10.9b broader ... | Practice Question

Why is the action spectrum for photosynthesis Figure 10.9b broader than the absorption spectrum of chlorophyll a alone Figure 10.9a ?

  • A: Chlorophyll a undergoes structural changes in different light conditions, allowing it to absorb more wavelengths.
  • B: Accessory pigments such as chlorophyll b and carotenoids absorb different wavelengths of light, thus broadening the range of colors usable for photosynthesis.
  • C: The measurement of O2 release in the action spectrum is inherently less precise than light absorption, leading to a broader curve.
  • D: Only chlorophyll a is active in light absorption for photosynthesis, but its efficiency varies greatly across the spectrum.

Explanation

The text explicitly states: 'Notice by comparing Figures 10.9a and 10.9b that the action spectrum for photosynthesis is much broader than the absorption spectrum of chlorophyll a. The absorption spectrum of chlorophyll a alone underestimates the effectiveness of certain wavelengths in driving photosynthesis. This is partly because accessory pigments with different absorption spectra—including chlorophyll b and carotenoids—broaden the spectrum of colors that can be used for photosynthesis.'