DANIEL I. ARNON 565 



164. AVarburg. ().. in Uctwx Metnl Prosllirlir C,)(iuf>s mid Enzyme Action, pp. 213- 



211. Ciarciulon Press. Oxford (1919). 



165. \Varburg, O., Krippahl, G., Gewitz, H. S., and Volkcr, W. Z., Naturforsch., 14b, 



712-724 (1959). 



166. Wci.ssbach, A.. Horcckci, B. L., and lluiwit/, J., /. liiol. Chcm., 218, 795-810 



(1956). 



167. Wessels, J. S. C, Rec. trav. chim., 73, 529-536 (1954). 



168. Wessels, J. S. C, Biochim. el Biopliys. Acta, 25, 97-100 (1957). 



169. AVessels. J. S. C, Biochim. et Biopliys. Ada, 29. 113-123 (1958). 



170. Whatley, F. R., Allen, M. B., and .\rnon, D. I., Biochim. el Biophys. Ada, 16, 



605-606 (1955). 



171. AVhatley, F. R., Allen, M. B., and Arnon, D. 1., Planl Physiol., 32, (Supp.) 



iii (1957). 



172. Whatley, F. R., Allen, M. B., and Arnon, D. I., Biochim. el Biophys. Ada, 



32, 32-46 (19.59). 



173. Whatley. V. R.. .\llen. M. B.. Rosenberg, L. L., Capindale, J. B., and Arnon, 



D. L, Biochim. et Biophys. Acta, 20, 462-468 (1956). 



174. Whatley, F. R., Allen, M. B., Trebst, A. V., and Arnon, D. I., Plant Physiol., 



33, (Supp.) xxvii-xxviii (1958). 



175. Whatley, F. R., Allen, M. B., Trebst, A. V., and Arnon, D. 1., Plant Physiol., 



35, 188-193 (1960). 



176. AVhittingham. C. P.. Biol. Rev., 30, 40-64 (1955). 



177. Williams, A. M., Biochim. et Biophys. Acta. 19, 570 (1956). 



178. Winogradsky, S., Botan. Ztg., 45, 489 ff. (1887). 



179. 'Winogradsky, S., Ziir Morphologic iind Physiologic der Schwefelbaderien, 



Arthur Felix, Leipzig (1888). 



DISCUSSION 



Dr. Frenkel: If Chromatium can produce hydrogen in the light, its cell- 

 free extracts should be capable of photoreducing pyridine nucleotides com- 

 parable to isolated chloroplasts or to chromatophores from Rhodospirillum 

 rubrum. I cannot see that the mechanism for the production of photo- 

 reductant and photo-oxidant is necessarily different in bacteria and in 

 higher plants. 



Dr. Arnon: First of all, let me say that we have observed in cell-free 

 Chromatium preparations reduction of pyridine nucleotides with succinate 

 and light, similar to the one you have reported with Rhodospirillum rubrum. 

 The difference between plants and photosynthetic bacteria is this. Bacteria, 

 for example, can use succinate to reduce pyridine nucleotide and as a 

 result fumarate is formed. However, green plants use water and form 

 reduced pyridine nucleotide and oxygen. That is the difference. Bacteria, 

 in our view, do not use water as a reductant. 



Dr. Frenkel: Yes, but in your earlier statement you implied that in higher 

 plants you have photolysis of water, whereas in bacteria you have some kind 

 of mysterious process in which high energy phosphate is formed which does 

 not involve photolysis. You stated that this is the big difference. You 

 stated definitely that photolysis is not occurring in bacteria. 



Dr. Arnon: I might plead guilty to an even greater heresy and say that 

 photolysis of water does not even apply to green plants. I think photolysis 



