Class 11 · Photosynthesis in Higher Plants

Absorption vs Action Spectrum — NEET Biology

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Now look at showing the wavelengths at which maximum photosynthesis occurs in a plant. Can you see that the wavelengths at which there is maximum absorption by chlorophyll a, i.e., in the blue and the red regions, also shows higher rate of photosynthesis. Hence, we can conclude that chlorophyll a is the chief pigment associated with photosynthesis. But by looking at can you say that there is a complete one-to-one overlap between the absorption spectrum of chlorophyll a and the action spectrum of photosynthesis?

🖼️Related NCERT figure: Three graphs showing (a) absorption spectrum of chlorophyll pigments with peaks for Chlorophyll b, Carotenoids, and Chlorophyll a plotted against absorbance of light by chloroplast pigments, (b) rate of photosynthesis measured by O2 release showing wavelength dependency, and (c) superimposed graphs showing both rate of photosynthesis and light absorption plotted against wavelength of light in nanometres from 400-700nm (Figure 11.3a Graph showing the absorption spectrum of chlorophyll a, b and the carotenoids Figure 11.3b Graph showing action spectrum of photosynthesis Figure 11.3c Graph showing action spectrum of photosynthesis superimposed on absorption spectrum of chlorophyll a)
NCERT Biology · Class 11 · Chapter 11 · Paragraph 27
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Assertion (A): Chlorophyll a is the primary pigment in photosynthesis. Reason (R): Chlorophyll b and carotenoids act as accessory pigments.

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