416 LIGHT AND LIFE 



complete photosynthesis (consuming 2 quanta per electron) , hoAv are 

 the absorbed quanta distributed over the two pathways in the proper 

 ratio? In other words, how can, as in green plants, the quantum yield 

 remain virtually constant over a spectral region in which the ratio 

 Chi. rt/Chl. b absorbance varies widely. Several ad hoc hypotheses 

 can be advanced, some of which are open to experimental test. 



It must be reemphasized that these thoughts about the two-quanta 

 interaction in the sensitization of photosynthesis are speculative and 

 are presented as a basis for discussion. However, evidence gathered 

 to date indicates a mechanism of this general type. 



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17. Kok, B., and Gott, J. W., Plant Physiol, (in press). 



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(1956). 



DISCUSSION 



Dr. Arnon: I have several questions. I will not take the time to ask 

 thcni all, but will start with the last point first, '^'our (oncludiiis; sentence 

 was that the yield of phoiophosphorylation was very low. and th.it the 

 (|uauturn yield was also so lf)vv that it is questionable whether it should be 

 taken seriously. Yet earlier you stated that the chloroplast material that 

 you had used was kept for long periods in the refrit-erator. Now, it happens 

 that the photophosphorylation yield is very mutli dependent upon the con- 



