THE RELATION BETWEEN PIGMENT CONCENTRATION AND PHOTO- 

 SY NTHETIC CAPACITY IN A MUTANT OF CHLAMYDOMONAS REIN- 



~~ HARDI ^ 



G. C. McLeod^, G. A. Hudock^, and R. P. Levine 



The wild type strain, 137 c, of Chlamydomonas reinhardi is capable of 

 phototrophic growth in the light in a minimal medium with carbon dioxide 

 as a sole carbon source 0). |t can be grown in the dark if the minimal 

 medium is supplemented with 0.2 percent sodium acetate. Both light and 

 dark grown cells have a chloroplast and photosynthetic pigments ^ ' ' , 



In contrast to the wild type there are several mutant strains ^ ' ' deno- 

 ted as yellow-in-the-dark or y strains which are unable to form a chloro- 

 plast or synthesize chlorophylTin the dark. Growth in the dark results in 

 a two-fold decrease in chlorophyll content with each cell division. The 

 most striking feature of the dark grown yellow cells is the absence of a 

 lamellar structure of the chloroplast ^~*/ . 



When the dark grown yellow cells are placed in the light chlorophyll 

 synthesis precedes lamellar formation. A normal chlorophyll content of 

 1 .5 to 2.0 ug/lO<^ cells is attained in 8-10 hours. During this exposure to 

 light the doubling time of the chlorophyll is 80-90 minutes whereas the 

 doubling time of the cells is 10 hours. The presence of the carotenoid pig- 

 ments is not sufficient for lamellar formation ^°) . The first detectable 

 lamellae are found after two hours of illumination by which time the chl- 

 orophyll content is between 0.5 to 0.7 ug/lO^ cells or 30 percent of the 

 normal complement. At the end of the regreening period the chlorophyll 

 content and chloroplast structure of the yellow cells are indistinguishable 

 from those of the wild type strain. Thus, the y-2 strain of C . reinhardi 

 during bleaching and regreening provides a biological system suited for 

 the study of the development of photosynthetic capacity under diverse pig- 

 ment compositions. 



400 



