206 



FIXATION OF CARBON DIOXIDE 



CHAP. 8 



servations of this kind have been made only accidentally, in the kinetic 

 studies of photosynthesis, when conditions were such that the acceptor 

 became "denuded" of carbon dioxide (because the enzymatic formation 

 of the complex did not hold step with the consumption of carbon dioxide 

 by photosynthesis). Under these conditions, a cessation of illumination 



-o 



(3 

 •*- 



i 



« 



Carbon dioxide concenfrotion — 0.3% by volume 



^3000 r.-c 



-2000 



■1000 



»3000 



5 10 15 



Time, minutes 



20 



Fig. 22. — Time course of carbon dioxide assimilation at 16° and 26° C. for four 

 light intensities. The "pickup" in the dark appears at the two higher hght intensities 

 (after McAUster 1939). 



was followed by a carbon dioxide absorption in the dark, which lasted 

 for seconds or even minutes. This phenomenon, called the "pickup," 

 was observed by McAlister (1939), McAlister and Myers (1940) and 

 Aufdemgarten (1939), who have followed photosynthesis by registering 

 continuously the consumption of carbon dioxide, rather than (as is 

 usually done) the evolution of oxygen. 



