826 FLUORESCENCE OF PIGMENTS IN VIVO CHAP. 24 



the absence of reactants, or poisoning, prevents the use of absorbed energy 

 for constructive purposes (z. e., for photosynthesis). 



While Franck's theory emphasizes the indirect mechanism of fluores- 

 cence changes associated with photosynthesis, the Dutch group (see 

 Wassink, Katz et at. 1938, 1942, 1949) use the simple concept of competi- 

 tion between the primary photochemical process and fluorescence (+ dis- 

 sipation). Because of the stronger effect on (p, in purple bacteria, of the 

 presence or absence of reductants (as compared to the presence or absence 

 of the oxidant, CO2) they assume that the primary process involves ex- 

 cited chlorophyll and the (enzymatically "prepared") reductants, but 

 does not involve CO2 (or the I CO2} -complex). 



There is no doubt that simple competition between fluorescence and 

 photochemical primary process is insufficient to interpret all the experi- 

 mental evidence. Franck's concept of indirect action, on the other hand, 

 has been successfully applied to a wide range of phenomena and has thus 

 acquired a considerable degree of probability. 



We will end this discussion here and leave the more detailed presenta- 

 tion and interpretation of experimental results to chapters 27-33 in part 

 IV, dealing with the kinetics of photosynthesis. Measurement of fluo- 

 rescence has become a tool in the study of the reaction kinetics of photo- 

 synthesis, and it would be inconvenient to separate the discussion of the ef- 

 fects of light intensity, or temperature, or carbon dioxide concentration on 

 the yield of fluorescence, from the discussion of the influence of the same 

 factors on the yield of photosynthesis. 



Bibliography to Chapter 24 

 Fluorescence of Pigments in Vivo 



1852 Stokes, G. G., Trans. Roy. Soc. London, 1852, 463. 



1862 Simmler, R. T., Ann. Phys. {PoggendorJ), 115, 593. 



1867 Askenasy, E., Botan. Z., 25, 225. 



1870 Hagenbach, A., Ann. Phys. {PoggendorJ), 141, 245. 



1871 Lommel, E., ihid., 143, 568. 



1872 Hagenbach, A., ibid., 146, 508. 



1874 Hagenbach, A., ibid., Jubilee Vol., 303. 



1883 Reinke, J., Ber. deut. botan. Ges., 1, 395. 

 Engelmann, Th. W., Arch. ges. Physiol. Pflilgers, 32, 80. 



1884 Reinke, J., Ber. deut. botan. Ges., 2, 265. 

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1913 Buder, J., ibid., 31 (80). 



1914 Lelnnann, H., Z. iviss. Mikroskop.. 30, 417. 

 Wilschke, A., ibid., 31, 338. 



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1921 Stern, K., Z. Botan., 13, 193. 



