422 



R. A. OLSON, F. S. BRACKETT, R. G. CRICKARD 



be limited below 0.5% oxygen and becomes barely detectable at this 

 light intensity in gases from which oxygen has been removed by hot 

 copper. The curvilinear relationship in this range is shown by de- 

 pendence on successively increasing oxygen concentrations in Fig. 9. 



14 1 l_J I I I 1 I l_J I I 1 I I I I I I I I Q 



5 10 15 20 



TIME IN MINUTE INTERVALS 



Fig. 3. Influence of reduced CO2 concentration on anaerobically adapted sus- 

 pensions. (A) with CO2; (B) without CO2; (A) obtained from suspensions used in 

 B after equihbration with 5% CO2 and 95% No. O2 cone. = 0.1% at ilhimination 

 in both. 



Three of the recordings in Fig. 2 were made in the absence of CO2, 

 yet in these and other similar experiments the character of the burst 

 is unchanged. Figure .3 shows the results with and without CO2 in 

 identical suspensions illuminated at similar O2 concentrations after 

 similar anaerobic dark treatment times. Here the sustained rate is de- 

 pressed in the absence of CO2 while both the magnitude and the char- 

 acter of the burst remain as unchanged as in the more aerobic CO2- 



