428 



Birgit Vennesland 



by sonerated Chlorella extracts shows a similar stimulation by CO^/ 

 lustrated in Table I. Sonerated Chlorella extract was incubated in the light 



TABLE I 



Effect of CO2 on H2O2 Production 



Sonerated Chlorella extract (200 (jI cells/ml) as indicated, 300 

 jjmoles phosphate, pH 6.6, 50 pmoies KCI, 3 pmoles NaN_, in 

 volume of 3 ml; air; L = 600 pl/min, 20°, 70 min. 



Amount extract CO^ O^ '^9^9 



ml % pmoles pmoles 



1.0 



2 -6.8 9.9 



-4.8 5.2 



0.25 



2 -2.4 3.4 



-1.9 1.7 



.-3 



with phosphate buffer, KCI and 10"^ M NaN to inhibit catalase. The 

 Table shows the O^ consumption and H„0„ production in the presence and 

 absence of externally added CO„. If nothing else is happening, one ex- 

 pects two molecules of H^O_ to accumulate for each mole of O^ taken up. 

 This ratio is not observed here, partly because there Is a consumption of O^ 

 in the dark, for which we have made no correction. The CO^ effect is re- 

 flected very clearly in the H»0^ formation. There Is twice as much H2O2 

 formed in the presence of externally added CO» as in its absence. 



With spinach chloroplasts. It Is more difficult to show the CO2 effect on 

 H„0_ production, but it Is there and can be demonstrated after depletion 

 procedures. Here again, H„0_ production gives a more sensitive response 

 to CO„ than does oxygen consumption. With broken chloroplasts, I have 

 obtained 20% stimulation of H^O^ production by CO2 under conditions 

 where the oxygen consumption was apparently unaffected. 



THE HILL REACTION WITH FMN 



May I turn now to a more detailed consideration of the Hill reaction 

 with FMN. The previous discussion provides a background for the 



