THE BACKGROUND CO2 FIXATION 



209 



flash, there occurred a distinct break in the course of C^^-fixation, and 

 the subseciuent ascension of the curve started from a point which was 

 lower than that observed immediately before the flashing of light. 

 If the duration of flashing light was prolonged to 3 seconds, the break 

 of the curve became less abrupt, but the lowering of the subsequent 



cpiii 



120 



80 



40 



OJ 

 X 



o 



10 SLC. I LASH 



II, 



TIME (IN MINUTES) OF CONTACT OF 

 CELLS WITH C'*02 IN THE DARK 

 ( IN N2 ATMOSPHERE ) 



Fig. 3. C"02 outburst from the product of background 0^*0^ fixation occurring 

 in N2 atmosphere. C^^Oo was supplied in the dark after the cells were dark- 

 adapted for 25 minutes in N2 atmosphere. Light flashes of indicated duration 

 were applied at the points shown by arrows. 



curve was more pronounced than was the case with the 1-second 

 flash. When the flash duration was 10 seconds, the break of the curve 

 practically disappeared, and the subsequent part of the curve showed 

 a peculiar course, ascending with increasing steepness with the lapse 

 of time. The break in C^'' fixation time course caused by 1- or 3- 

 second flashes must be taken as evidence that a part of C^* fixed 



