DANIEL I. ARNON 



i39 



2 3 4 



fuM TPN added 



Fig. 18. Stoicliiometry of oxygen evolution and ATP formation resulting from 

 the photochemical reduction of TPN (Arnon, VVhatley, and Allen, 18, 18a). /x.\, 

 microatoms. 



inhibitor as it was in cyclic photophosphorylation (Table 4) , but an 

 electron acceptor which promoted ATP formation. The results are 

 shown in Table 10. 



The mechanism of reaction 5 is visualized as the non-cyclic electron 

 flow mechanism in photosynthetic bacteria (Fig. 17) but with water 

 as the electron donor (H/J) . Fig. 19 gives a diagram of the non- 

 cyclic photophosphorylation of green plants, represented here as a 

 part of the general electron flow mechanism in photosynthesis that 

 was shown elsewhere (9) . 



We visualize non-cyclic photophosphorylation of green plants (Fig. 

 19) as having in common with other photophosphorylations the same 

 primary photochemical act (Equations 3 and 3a) and the saine pri- 



