502 



LIGHT AND LIFE 



INTENSE LIGHT and HIGH CHLOROPHYLL 



14 



12 



10 



8 



6 



4 



-2 



0D03 0.01 0.05 0.1 0.3 

 /j.moles vit. Kj added 



1.0 



0003 0.01 0.05 0.1 0.3 1.0 



/imoles FMN added 



Fig. 3. Effect of vitamin K^, (2-metli\l-l,4-naphthoqiiinone) and FMX concentra- 

 tion on cyclic photophosphorylation by spinach chloroplasts in nitrogen and air 

 at a high Hght intensity. The reaction mixture (3 ml final volume) included 

 chloroplast fragments (Ci^) containing 1.5 mg chlorophyll; and in micromolcs: 

 Tris buffer pH 8.3, 80; K„H''-PO„ 20; ADP, 20; MgSO,. -r, and TPN, 0.3 (only in 

 the FMN scries). FMN and \itamin K.j were added as indicated. The reaction 

 was run for ') minutes at an illumination of .")().()()() Lux. (Tsujimoto, Hall, and 

 Arnon, l.")f); .\rnon, Whatley, and Allen, unpublished tiala, 1954.) 



reoxidizing the requisite catalysts — when these are present in limiting 

 concentrations. At the higher concentrations of added cofactors, 

 photosynthetic phosphorylation could proceed in the total absence of 

 oxygen (see Section 16) . 



This interpretation is in agreement with the recent results of 

 Wessels (169), Jagendorf and Avron (77), and Nakamoto, Krog- 

 mann, and Vennesland (111), that photosynthetic phosphorylation 

 with suboptimal amounts of cofactors was oxygen-dependent but 

 became oxygen-independent at higher concentrations of cofactors. 



In charting their subsequent investigation, the Berkeley group laid 

 special stress on the anaerobic photosynthetic phosphorylation which 

 proceeds in isolated chloroplasts at optimal catalytic concentrations of 

 FMN and vitamin K. They considered this type more fundamental 

 to photosynthesis in general than the oxygen-catalyzed type because 

 it would also apply to bacterial photosynthesis, which is an anaerobic 

 process. 



