LIGHT ABSORPTION OF PHOTOSYNTHESIZING CELLS 



()5 



Chlorella \520 



1 mm 



Fig. 3. Changes in optical density of Chlorella at 520 m.u upon onset of illumina- 

 tion (upward arrow) and darkening (downward arrow) as a function of time. 

 The relative intensities of the exciting Hght are wiitten near the arrows. 



Chorella A '420m/j 



logje .10~^ 

 I 



air with and without 

 carbon dioxide 1 



A /Off 



Fig. 4. Time courses of changes in optical density of Chlorella at 430 m/* in the 

 presence and absence of carbon dioxide. 



it is possible to measure the time course upon illumination or darken- 

 ing as a function of the following parameters: 



1. The composition and pH of the suspension medium. One may 

 vary, for example, the concentration of carbon dioxide or other 

 nutrients, oxidizing and reducing substances, poisons. 



