1882 SPECTROSCOPY AND FLUORESCENCE OF PIGMENTS CHAP. 37C 



(e) Fluorescence of Chlorophyll c in Diatoms 



French (1954) could find no chlorophyll h fluorescence bands in living 

 green plants, nor any chlorophyll c fluorescence bands in diatoms. The 

 latter band should lie at 640 m/i; instead, the only additional fluorescence 

 band observed in diatoms was located at 705 mn. It may represent the 

 first vibrational fluorescence band of chlorophyll c, in which case the main 

 band must be presumed to be lost by effective re-absorption in chlorophyll 

 a. 



(/) Changes of Fluorescence Intensity Related to Photosynthesis 



The kinetic relationships between the chlorophyll fluorescence in vivo 

 and photosynthesis, described in chapter 24 (section 4), chapter 27 (part 

 B) and 28 (part B) have again been reviewed by Wassink (1951). He 

 argued that the hypothesis of Franck, which ascribes the most important 

 changes in fluorescence intensity of living cells to metabolic formation and 

 removal (by oxidation or displacement) of a "narcotic" from the surface 

 of chlorophyll, is not basically different from the picture evolved by the 

 Dutch group (in which the intensity of fluorescence is determined by the 

 interaction of excited chlorophyll with an energy-accepting chemical 

 system) — if one equates ''narcotic cover" with "absence of energy-ac- 

 ceptor." However, this conciliation of the two views is purely formal 

 and neglects basic physical differences. Franck's self-consistent, and 

 physically plausible theory was again summarized in a paper (1951) 

 which contained also an interpretation, in the terms of this theory, of 

 Wassink and Kersten's observations on diatoms {cf. p. 1050, and figs. 

 28.28, 28.39 and 28.44). In these cells — in contrast to green algae and 

 purple bacteria — the yield of fluorescence decreases — instead of increas- 

 ing — when photosynthesis becomes light-saturated; Franck saw in this 

 relation evidence that in diatoms substances engaged in primary photo- 

 chemical reactions are better "fluorescence protectors" than narcotics, 

 a conclusion supported by the observation (not mentioned on p. 1063) that 

 ethyl urethane depresses the fluorescence of diatoms, while it increases 

 that of other cells {cf. figs. 28.49 and 28.50). 



Bibliography to Chapter 37C 

 Spectroscopy and Fluorescence 



1929 Pen-in, F., Ann. physique, 12, 169, 261. 



1940 Fischer, H., and Stern, A., "Chemie des Pyrrols," (Vol. II.2, Pyrrol 

 farbstoffe), Akad. Verlagsges., Leipzig. 



1944 Polgar, A., van Niel, C. B., and Zechmeister, L., Ardi.. Biochem., 5, 243. 



1945 Lewis, G. N., and Kasha, M., ./. Am. Clicm. Soc, 67, 994. 



