442 H. GAFFRON 



is significant because it means that in the chloroplasts as soon as you turn the 

 light off the photosynthetic intermediates are converted into Krebs cycle inter- 

 mediates, and on turning the light on again, some of them are converted back 

 over to photosynthetic intermediates. 



Gaffron: This is very agreeable. We can explain nearly everything. A question, 

 of course, concerns the quantities we have. We also ought to be careful in compar- 

 ing the times. 



Bassham : I think they are in perfect agreement with all your results. 



Blinks : I thought I saw one place where there might have been a flash of CO2 

 gas. You meant the Emerson CO2 effect? 



Gaffron : Yes. I have to use Chorella and keep them cool. Then I get it, but it is a 

 long-drawn-out affair. 



Wassink: I would like to comment that Dr. Gaffron probably recalls that we 

 have done exactly the same thing. With a suitable sequence of light and dark 

 periods, you can keep fluorescence at a higher level, and you can get photosyn- 

 thesis during that situation and find certain characteristics, which I don't recall. 

 However, these are different from those in the steady-state illumination and may 

 have a bearing on these compounds and still other ones that are engaged in the 

 final phases of photosynthesis. 



Gaffron : Observations of fluorescence and chemiluminescence first have to be 

 taken at their face value from the point of view of the physicists and their inter- 

 pretation sought simply in terms of what the pigments themselves can do when 

 illuminated. This is difficult enough. Following this, we have to collect biochemical 

 data on the kinetics of intermediates. A joint physical and biochemical approach 

 may permit a satisfactory explanation of induction periods. 



Kok: I want to point out that to me it appears premature to hypothetically 

 postulate biochemical pathways for explaining these complicated effects. I could 

 have shown all sorts of anomalous oxygen and carbon dioxide exchanges, which 

 we measured simultaneously under a variety of conditions. One can obtain just 

 about any result. 



Gaffron : Therefore we should concentrate on those which are typical and can 

 easily be reproduced. These are a selected few, which make sense. 



Brown: Have you done any measurements at low pH where you do not have a 

 good bicarbonate buffer? 



Gaffron : Yes, the only difference I found is that, unfortunately, one cannot 

 calculate the rates. For pure bicarbonate buffers we can calculate nicely, as Dr. 

 Rosenberg has shown, and we can convert these wiggles into quantitative rates. 



Brown : I mean well out of the buffer range. 



Gaffron: I can wash the algae three times with distilled water, saturate with 

 5% CO2, and watch what happens there. It turns out that the general shape of the 

 curve remains identical. So we may consider ourselves on safe ground. 



Brown : I don't want distilled water because you still have a buffer to some ex- 

 tent probably. I want a dilute buffer, at low pH. Do you have that kind of data? 



Gaffron: For a dilute carbonate-free pho.sphate buffer near neuti'alit.y see Fig. 1. 

 I have no experiments with buffers in the trulj^ acid range. 



