Photosynthesis action spectrum

Fig. 2.24 Light absorption characteristics of some photosynthetic pigments and their relationship with utilization of light energy during photosynthesis (action spectrum).

The existence of two separate but interacting photosystems in photosynthetic eukaryotes was demonstrated through analysis of the photochemical action spectrum of photosynthesis, in which the oxygen-evolving capacity as a function of light wavelength was determined (Figure 22.10). 

FIGURE 22.10 The photochemical action spectrum of photosynthesis. The qnantnm yield of photosynthesis as a fnnction of wavelength of incident light shows an abrnpt decrease above 680 nm, the so-called red drop. 

The action spectrum of photosynthesis, which describes the efficiency of photosynthesis as a function of the wavelength of incident light, has a valley around 550 nm. Why ... 

Figure 5-13. Absorption spectrum for an algal thallus and the action spectrum for its O2 evolution, illustrating the red drop in photosynthesis. [Data for Viva taeniata are from Haxo and Blinks (1950). Reproduced from The Journal of General Physiology by copyright permission of The Rockefeller University Press.]...

Fig. 17. (A) Absorption decrease at 704 nm in broken spinach chioroplasts induced by a 720-nm fiash and absorption increase induced by a 638-nm fiash (B) action spectrum for the absorption changes due to P700 oxidation and reduction, respectiveiy, measured at 433 nm. Figures from Witt (1967) On the anaiysis of photosynthesis by pulse techniques in the ICr to 10 second range, in S Ciaesson (ed) Fast Reactions and Primary Processes in Chemicai Kinetics, p 273 and 275. Interscience.

In the 1950s, Robert Emerson used a more precise version of the action spectrum to investigate photosynthesis. When he measured... 

If the rate of photosynthesis versus the incident wavelength of light is plotted, an action spectrum is obtained. How can the action spectrum provide information about the nature of the light-absorbing pigments involved in photosynthesis ... 

Using the action spectrum for photosynthesis on p.445, determine what wavelengths of light appear to be optimal for photosynthesis. 

One of the strongest pieces of evidence for the involvement of chlorophylls and carotenoids in photosynthesis Is that the absorption spectrum of these pigments is similar to the action spectrum of photosynthesis (Figure 8-32). The latter Is a measure of the relative ability of light of different wavelengths to support photosynthesis. 

This assumption is always true for polychromatic-illumination and for monochromatic-illumination experiments in the case of eukaryotic microalgae, according to the well-known action spectrum of photosynthesis. This is not the case for monochromatic illumination of cyanobacteria (Farges et al., 2009). 

McCree KJ The action spectrum, absorptance and quantum yield of photosynthesis in crop plants, Agric Meteorol 9(3) 191—216, 1971. 

The study of the wavelength dependence of photosynthesis has been extremely valuable in determining the role of the various pigments in photosynthesis. Such studies have been carried out by comparing the action spectrum of photosynthesis with the absorption spectrum of the plant. The photosynthetic action spectrum is determined by measuring the... 

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