STUDIES WITH CYANIDIUM CALDARIUM. II. THE FINE STRUCTURE 

 OF PIGMENT-DEFICIENT MUTANTS 



Lawrence Bogorad, Frank V. Mercer, and Rosemary Mullens 



The complete understanding of photosynthesis requires know- 

 ledge about physical and biochemical events in relation to the 

 structure of the photosynthetic system. The early suggestion of 

 Hubert that the chloroplast contains alternating layers of 

 protein and lipid with chlorophyll associated with both la- 

 yers and the carotenoids embedded in the lipid phase --j? has.ser- 

 ved as a model for most subsequent speculation and work ' on 

 the molecular structure of the photosynthetic system. 



Electron microscopy has confirmed the existence of a multi- 

 layered structure within chloroplasts . This lamellar system is 

 differentiated into grana and intergrana lamellae in most chloro- 

 plasts of higher plants; chloroplasts of algae and some other 

 species consist of simple lamellae only ' . 



There is considerable evidence that the photosynthetic lamel- 

 lae consist of protein-lipid, layers; that the chlorophyll may be 

 tightly bound to protein ' ; that the other photosynthetic 

 pigments are closely associated with the chlorophylls ; and 

 that the pigments. have a key role in the photochemical activity 

 of the lamellae , Because of these points it seems reasonable 

 to suppose that, in addition to their photosynthetic roles, the 

 pigments may also be essential structural constituents of the 

 photosynthetic lamellae ., and _have a casual role in the morpho- 

 genesis of the lamellae ' . In the present paper these pos- 

 sibilities are considered in relation to the structure and orien- 

 tation of the lamellae in non-grana type chloroplasts. 



EXPERIMENTAL 



Lamellae of non-grana chloroplasts 



The dimensions of the photosynthetic lamellae of non-grana 

 type chloroplasts of the higher plants measured on electron mi- 

 crographs show that the basic structural unit of lamellae is the 



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