159 



R. P. Levine 



were unable to carry out normal photosynthesis because of gene mutation that 

 either; 



1) affected the synthesis or activity of enzymes responsible for the 

 formation of components in the electron transport system of photo- 

 synthesis; or, 



2) affected the synthesis or activity of enzymes whose function lies in 

 synthetic processes attending normal chloroplast development; or, 



3) affected the synthesis or activity of enzymes responsible for the 

 formation of components of the reductive pentose cycle. 



Clearly, the actual nature of the genetic block could be any one of the afore- 

 mentioned and result in a cell's inability to carry out normal photosynthesis. 

 Furthermore, it was realized that it might be difficult to distinguish, at least 

 on a phenotypic basis, between certain classes of mutants in view of the intimate 

 relationship between chloroplast structure and function. 



The results and conclusions presented here derive principally from bio-- 

 chemical experiments utilizing chloroplast fragments and, as such, they may 

 not necessarily reveal what happens in the intact cell or chloroplast. However, 

 the model presented here is in substantial agreement with some of the models 

 that have been proposed from studies with whole cells or whole chloroplasts''^"^^. 



METHODS 



The methods we have used for investigating the electron transport system 

 of photosynthesis in C. reinhardi stem largely from the well established tech- 

 niques used with higher plants. A description of the methods for assaying the 

 activity of enzymes related to photosynthesis, as well as the techniques for in- 

 vestigating photosynthetic reactions by whole cells and isolated chloroplast 

 fragments of C. reinhardi have been published (see principally references 9-11). 

 Details for the procedures used in isolating and measuring the quantity of dif- 

 ferent components of the electron transport system of photosynthesis have also 

 been described^ ^2, 13)_ ^^i^ methods for investigating the electron spin reso- 

 nance signals in C. reinhardi have been described elsewhere' ^'^'. Photo- 

 reductionUS) by whole cells following adaptation to hydrogen gas was measured 

 manometrically as consumption of hydrogen in the light or as carbon dioxide 

 fixation in the light from C^^.^abeled bicarbonate. The procedures, details of 

 which will be published elsewhere^ "', are similar to those used for 

 Scenedesmus( 1 "7). 



GENERAL DESCRIPTION OF THE MUTANT STRAINS 



The mutant strains of C. reinhardi used for the experiments reported 

 here were derived from the wild type strain (No. 137c) by induction with 



