394 DANIEL I. ARNON 



presence of the requisite cofactors, cyclic photophosphorylation is capable 

 of diverting all the absorbed light energy for the formation of ATP, and 

 suppressing TPN reduction and Og evolution. It is assumed that the 

 intact cell has suitable regulatory mechanisms for keeping cyclic and non- 

 cyclic photophosphorylation in balance. 



-o 8 



< 



3. 



minutes 



Fig. 30. Photophosphorylation and oxygen evolution by isolated chloroplasts 

 in the presence and absence of FMN (Arnon, Whatley, and Allen, [95, 158]). 



TABLE XVII 



Effect of FMN and Vitamin K3 on Photophosphorylation and Oxygen 

 Evolution Linked to TPN Reduction 



(Arnon, Whatley, and Allen [158]) 



The marked increase in phosphorylation accompanied by a total 

 abolition of oxygen evolution and TPNHo accumulation, shown in Figs. 30 

 and 31, occurred on adding o • i /nmoles of FMN or o -2 ^moles of vitamin 

 K (in a final volume of 3 ml.). However, the addition of even extremely 

 minute amounts of either FMN or vitamin K had a measurable effect on 



