204 



METABOLISM AND PHYSIOLOGY 



period). The initial tangents of the curves (ATP formation rate vs. 

 flash duration) were proportional to light intensity. From these experi- 

 ments it is indicated that the extent of the primary photochemical 

 reaction is proportional to the amount of energy in the short flashes, 

 but utilization of the first chemical product (s) is a dark process and 

 requires a longer time than its production. 



Rate Of Phosphorylation After Flash 



A Pi/min/BCHL 



8,000 lux + 88A 

 1.45msec il 

 28« 



3.l6xlO"®M 

 BCHL./H0QN0 = 2I8 



15msec. 



Fig. 3. Effect of HOQNO on rate of phosphorylation after flash (Pi esteri- 

 fied in moles/min/mole bacteriochlorophyll). # — #, no HOQNO; O — Q 

 3.16 X 10-8 M HOQNO. Type A illumination, 8000 lux f 88A filter, 28°C. 



Effect of HOQNO, ^ MPM and temperatures on the delayed photophos- 

 phorylation 



The rates of delayed phosphorylation in the presence (3.16 x 10"^ 

 m) and absence of HOQNO are compared in Fig. 3. It is apparent that 

 the rate of decay of delayed photophosphorylation is markedly lowered 

 by HOQNO. The lower level of phosphorylation under continuous illu- 

 mination, as well as the slower decay of delayed photophosphorylation 



1 Abbreviations: HOQNO, 2-^/-heptyl-4-hydroxyquinoline-iV-oxide; MPM, meth- 

 ylphenazonium methosulfate ("phenazine methosulfate"). 



