322 A. R. KRALL 



a steady state before you turned your li{;lits ofT? How jnudi of the ohservatioii was 

 in the induction state and how juuch of it was in the steady state? 



Krall: The P" oxperijucnts wore st<^ady state ones in that they were two hours 

 long. In other ras(;s P" w;i.s phiced in (he plant for :). long time, then the plant was 

 exposed to inhibitory conditions and the (change in the P^-' distribution was noted. 

 The same results arc obtained cither way. The ATP level is very low in the presence 

 of red light, and slightly higher- in the presence of yellow light. If you keep the 

 oxygen in, the ATP stays high. 



Rabinowitch: My general remark is that when trying to cover the whole field 

 of photosynthesis, as I did, one is always impressed by how often people don't 

 care for work that others have done in this field, particularly if it was done by 

 people who had a different approach and came from a different side. The physical 

 chemists and the physicists are often told that they don't care enough for what the 

 biochemists know about likely and unlikely chemical processes. I tliink this criti- 

 cism should have reciprocal validity, and that the liiochemists, too, have a certain 

 obligation to look into, not ignore, what has been found by people who approach a 

 problem from the non-biochemical side. This alleged oxygen effect is a case in point. 



I must say the suggestion thrown out by Dr. Kamen that the energy of chloro- 

 phyll could be transferred to cytochrome is another one. He said something about 

 the need for such a transfer of an absorption band on the red side. But then he 

 said that this is perhaps not so important. I was waiting for Dr. Duysens to pro- 

 test, but since he did not, I will. 



How can one dismiss so lightly the empirical conclusion (which also has a sound 

 physical basis), that energy transfer always occurs towards the longest wave- 

 lengths? How can one lightly suggest that the cytochromes may perhaps have a 

 band somewhere in the red, and then add that if the.y don't have such a band, well, 

 it isn't so important for the resonance transfer anyhow? 



Kamen : I did not intend to give the impression I was talking only about cyto- 

 chromes. I was talking about hemo-proteins in general. There are hemo-proteins 

 here which have not been accounted for yet, which can have the necessary absorp- 

 tion characteristics. 



The point is that if you take out the cytochrome and you look at the spectrum 

 of the pure compound, even if you don't find it, it might still be possible that the 

 cytochrome in association with something in the cell can have the proper absorp- 

 tion spectrum. 



I don't think that we can argue about the phj^sical chemistry of the chlorophyll 

 molecule from the standpoint of simple magnesium porphyrins. We have to talk 

 about the whole system. 



Also I don't have a stake in the cytochrome picture. I simply say we have to 

 consider the possibility of direct excitation of the cvtochrome. Whether it is pos- 

 sible on the basis of our present knowledge I don't know. 



Gaffron: Would it not be more practical to argue from the things that we know 

 than from the things we don't know? 



Kamen : I believe I can say with some conviction that I have heard more argu- 

 ments from what we don't know from the standpoint of the physical chemists than 

 I have from the biochemists. That is my own feeling about it. 



Weigl: Perhaps what Dr. Kamen means is simpl}' that he won't in.sist on reso- 



