248 



F. R. Whatley 



Table 3 



Effect of small amounts of ferricyanide 

 on cyclic photophosphorylation 

 catalyzed by a limiting amount of PMS 

 under argon 



Ferricyanide 

 added 

 (umoles) 







0.25 

 0.5 



1.0 

 1.5 

 2.0 

 2.5 



ATP formed in 

 30 minutes 

 (umoles) 



1.7 

 3.5 

 6.2 



6.1 

 7.9 



8.0 



8.4 



Experimental condi- 

 tions as described in 

 legend to Table 1. 3 

 Jig PMS were added to 

 each vessel. Ferri- 

 cyanide was added as 

 indicated and remain- 

 ed in contact with 

 the chloroplast frag- 

 ments and the PMS for 

 5 minutes while the 

 vessels were flushed 

 with argon, and be- 

 fore the light was 

 turned on. 



The inhibitor p-chlorophenyl-dimethyl-urea (CMU) also affec- 

 ted cyclic photophosphorylation with PMS, as can be seen by ex- 

 amining the data presented in Table h. The addition of CMU 

 (2.10"^ M final concentration) to the PMS system under argon 



Experimental conditions as described in legend 

 to Table 1. CMU to a final concentration of 

 2.10"^ M was added where indicated. 



produced a large stimulation of ATP formation at lower concen- 

 trations of PMS (Columns 1,2), this effect resembling very 

 closely the effect of air (Column 3). When 3O ^grams PMS were 

 added no effect was produced by CMU. On the other hand, the 



