361 



David C. Fork 



determined with weak 700 nip background light, has a peak at 669 mp 

 and a far-red limit near 713 mn. This action spectrum shows that 

 the production of O2 by chloroplasts illuminated with 700 mu light 

 is most effectively mediated by absorption by short-wavelength 

 chlorophylls such as chlorophyll a 670 and chlorophyll b. 



The action spectrum for the regeneration of the O2 spike had a 

 small hump at 660 mp. The possibility that some accessory pig- 

 ments also accompany the long -wave length chlorophyll needs further 

 investigation, 



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