725 



Edgar Inselberg and J. L. Rosenberg 



Such large rapid increases in fluorescence yield that could 

 account for these emission changes have not been reported, to our 

 knowledge; on the other hand, cases of large increases in fluo- 

 rescence during prolonged bleaching are well knovm (1). By analo- 

 gy to the steady-state situations, we visualize the flash as 

 bringing about a temporary bleaching of some chlorophyll, either 

 by phot ©oxidation or by j^otoionization. This process would tem- 

 porarily impede the flow of excitation energy throu^ the photo- 

 synthetic units, resulting in increased dissipation as fluores- 

 cence • 



SUMMARY 



Relatively large changes in emission may be superimposed on 

 changes in absorption when observations are made with a red-sen- 

 sitive flash apparatus. Accordingly, it is desirable to reexamine 

 some of the findings on the 703 mp, change. An apparatus design 

 and a procedure for resolving the contribution of absorption and 

 emission changes to overall changes observed with a flash-appara- | 

 tus are described. As a tentative mechanism for flash-induced lu- 

 minescence, we propose that the actinic li^t by bleaching some 

 chlorophyll causes a temporary disruption of energy migration 

 with a concomitant temporary increase in fluorescence. 



ACKTJOWLEDaEMENT 



Tliis research was supported by the United States Air Force 

 throu^ the Air Force Office of Scientific Research under grant 

 No. AF-AFOSR-3U9-63. 



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2. Kok, B., Biochim. et Biophys. Acta, 22, 399-liOl (1956). 



3. Kok, B., Acta Botan. Neer., 6, 316-336 (1957). 

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(McElroy, V/. D., and Glass, B., eds.) 397-ul6, Tlie Johns 

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5. Witt, H. T., Moraw, R., and Miiller, A,, Z. physik. Chem. Neue 



Folge, 20, 193-205 (1959). 



6. Witt, H. T,, and Moraw, R., Z. physik. Chem. Neue Folge, 20, 



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7. Witt, H. T., Miiller, A., and Rumberg, B,, Nature, 192, 967-969 



(1961), 



