TRANSIENTS FOR CARBON DIOXIDE 



435 



if corresponding manometric pressure changes were l^elieved to be 

 caused by normal pJiotosynthesis is obvious. 



The exact flatness of the part of the curve inunediately after the 

 hght has been turned on does not seem to have been caused by a 

 fortuitous balance of the release and uptake of carbon dioxide aided 

 by a lag in the response of the apparatus. Off hand, one would expect 

 a gradual change from respiration to photosynthesis. Figure 5 shows 

 this type of transition found with the same suspension of algae which 



PH6.5 



PH7.0 



"38 SCENEDESMUS 08 % IN -g^ BICARBONATE 



Fig. 6. Absence of conspicuous transients under anaerobic conditions and their 

 reappearance with the beginning of respiration. Recording of pH changes during a 

 succession of Hght ( j ) and dark ( f ) periods. The lower curve is the continuation 

 of the upper one. Scenedesmus, 0.8% cell volume in 0.002 M bicarbonate, kept 30 

 minutes under hydrogen in the dark. 



a short moment ago gave a flat compensation. In both these curves the 

 rate of the response of the apparatus to the pH change in the dark and 

 in the light is about the same, yet we have this striking difference in 

 the shape of the transition during the first 30 seconds in the light. It is 

 therefore the conditions in the algae and not that of the apparatus 

 which determine the shape of the induction curve. 



A gradual transition from carbon dioxide release to carbon dioxide 

 absorption speaks for an independent respiration on which a slowly 



