Name: Photosynthetic Pigments
Uploaded: 2019-07-19
Duration: 10 min 37 s
Description: There are six photosynthetic pigments in plants of which chlorophyll is of paramount importance. They absorb light of a certain wavelength for photosynthesis...

Question

Discuss the similarities and differences between the absorption spectra for chloroplast pigments in figure a and the action spectrum for photosynthesis in figure b. If a composite line draws for the absorption spectra, combining all the absorption spectra for the different pigments, how similar would this line be to the action spectrum for photosynthesis? Suggest reasons for any differences.

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Accepted Answer

The absorption spectrum is a graph showing the absorbance of different wavelengths of light by a photosynthetic pigment. The most common pigment molecules are chlorophyll a, chlorophyll b and carotenoids. Chlorophyll a and b show high absorption in the blue and red regions of the visible light. There is no absorption in the green region because the green pigments reflect green colour. The carotenoids also show maximum absorption in the blue region and no absorption from green to red. This is because carotenoids consist of different pigments ranges from yellow (xanthophyll) to red (lycopene).

The action spectrum is a graph showing the effect of different wavelengths of light on photosynthesis. The graph showing the rate of photosynthesis is maximum in blue (400 to 500 nm) and red (600 nm to 700 nm) regions.

If a composite line draws for the absorption spectra, combining all the absorption spectra for the different pigments as given below, the graph shows more similarities with the action spectrum.

The absorption spectrum of chlorophyll a and b are similar to the action spectrum of photosynthesis because these two pigments are the main pigment in this process. The main difference between these two are the region of the wavelength between 500-620nm (yellow-green region). In this region absorption rate is minimum by chlorophyll (pigment) molecules, but photosynthesis takes place at a slower rate. This is because other pigment molecules also take part in photosynthesis, which can absorb green and yellow light.

Mary Jones, Richard Fosbery, Dennis Taylor and, Jennifer Gregory Solutions for Chapter: Photosynthesis, Exercise 4: Questions

Mary Jones Biology Solutions for Exercise - Mary Jones, Richard Fosbery, Dennis Taylor and, Jennifer Gregory Solutions for Chapter: Photosynthesis, Exercise 4: Questions

Questions from Mary Jones, Richard Fosbery, Dennis Taylor and, Jennifer Gregory Solutions for Chapter: Photosynthesis, Exercise 4: Questions with Hints & Solutions

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