251 



F. R. Whatley 



redox balance without oxygen, and in the case of both PMS and 

 pyocyanine can be shown to become easily overoxidized by oxygen. 

 The hypothesis of a regulatory role for oxygen is consistent 

 with the results of Jagendorf and Avron on the effect of air, 

 CMU and o-phenanthroline on the PMS system, for which they were 

 earlier unable to offer an explanation (9) . The hypothesis also 

 suggests an explanation for the stimulatory effect of DCMU on 

 the cyclic photophosphorylation catalyzed by the indophenol 

 dyes, which has been described by Trebst and Eck (12). 



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