ATP FORMATION BY SPINACH CHLOROPLASTS 46 1 



Smith : There is a very interesting effect in photosynthesis which is caused by 

 irradiation of the plant with two wavelengths at the same time which is called the 

 Emerson enhancement. When these two wavelengths are used together they give 

 more photosynthesis than when used separately. It has been found that when 

 these two wavelengths are given alternatively the enhancement occurs as well as 

 given simultaneously and the effect will last as long as 15 sec. between irradiation 

 with the two wavelengths of light. In other words, times can go as high as 15 sec. 

 between the radiation with the long wavelengths and that which is absorbed by 

 chlorophyll b or some form of chlorophyll a, and my colleagues have been wonder- 

 ing whether it is phosphorylation or something of this nature ; or could one have 

 an intermediate of the form that you have suggested ? Have you done any action 

 spectrum on this at all to see whether it is formed by chlorophyll a or chlorophyll h ? 



Jagendorf: We previously obtained an action spectrum, and, as you probably 

 know, Hoch and Kok, at Glenn L. Martin Co., Baltimore, have run some action 

 spectra for phosphorylation recently. The picture is still a little bit confused, I 

 think, but briefly it looks to me as if the requirement for the accessory pigment 

 occurs only when oxygen evolution occurs. Now phosphorylation can be supported 

 either by an electron transport cycle, or by the series of reactions leading to oxygen 

 evolution. In the experiments of Hoch and Kok there seems not to have been any 

 oxygen evolution, and, correspondingly, no accessory pigment illumination was 

 needed for phosphorylation. In our experiments I think now that there probably 

 was some oxygen evolution, and we did need accessory pigment illumination for 

 phosphorylation. I want to emphasize that the existing data are not complete and 

 1 don't want to sound too positive. But I think quite clearly Kok does find some 

 phosphorylation going when only chlorophyll a is being illuminated, which would 

 rule out our present intermediate as the one where the second pigment participates. 



Packer : I would like to comment on the possibility of the existence of an 

 arsenate energy-rich intermediate or sort of factoral approach in our studies of 

 the swelling and shrinking phenomenon in mitochondria. We titrated phosphate 

 to get a certain swelling level and we soon noticed a change in the level of the 

 intermediates, so the interesting thing was that we could do the same type of 

 experiment with arsenate and it titrated to exactly the same swelling level, although 

 the arsenate requirement is slightly different from phosphate and we presume 

 from this that it miyht indicate that an energy-rich arsenate intermediate could 

 exist. 



