304 



B. KOK 



how at the present time, one could make a choice between the alternatives — 

 energy diffusion or particle diffusion. The abundant experimental confirmation of 

 energy migration in the chloroplast between different pigments — to which Kok 

 refers — requires only a single energy transfer during the excitation time and cannot 

 be taken as proof that the migration between identical molecules actually extends 

 over several hundreds of the latter. 



Strehler: If the absorption changes that Dr. Witt mentioned yesterday (a 

 rapid change, followed by a slow fall-off) are due to the same compound, then, 



h. X mg. chlorophyll 



3500 n 



3000- 



2000- 



1000- 



1500 2000 



Light Intensity 

 (foot candles) 



Fig. G. The effect of light intensity on the rates of photosynthesis of cultures 

 of Scenedesmus D-3 grown on a complete, highly purified mineral medium with 

 an added 10 parts per bilhon of vanadium ( X ), and of cultures grown on the same 

 medium without added vanadium (O).'' Cells suspended in 0.171/ KHCO3-K2CO3 

 buffer pH 9.0 for measurement of photosynthetic rates. Rates of O2 production 

 corrected for dark respiratory O2 uptake. 



rather than saying, as Kok did, that there are two separate catalytic components, 

 one reacting with another, it may be that there is a single component, which is 

 adsorbed at the site of the photochemical process. This compound could dissociate 

 after the photochemical act and be replaced by another molecule just like it. 

 Diffusion would perhaps be limiting for the second process. 



Kok : A model of this type, though apt to be more complicated, may also fit the 



observations. 



Strehler: With respect to Rabinowitch's interpretation of Kok's scheme: 

 It may not be necessary to assume that enzymes are involved at all in some of these 

 steps, because it is known that some of the very important intermediate hydrogen 



