413 



George Hoch and Olga v. H. Owens 



is still present, but is considerably smaller, both wave- 

 lengths exhibiting a slight but significant inhibition in 

 oxygen production. The results are in general agreement 

 with Warburg in demonstrating that the most pronounced 

 inhibition is observed in saturating light. 



Oxygen uptake shows an interesting effect which might 

 help to explain some of the anomalies which we have seen in 

 our experiments and which undoubtedly can lead to discrepan- 

 cies in data. At this concentration of cyanide (10"3m) dark 

 respiration was inhibited to near zero. Vi/ith increasing 

 light intensity of 65O mu, respiration increased in a nearly 

 linear fashion until it equalled and then exceeded the un- 

 inhibited control. Similar results have been obtained with 

 Anacystis . In no case, however, have we been able to show a 

 significant difference in inhibition of oxygen production 

 with wavelength. 



Respiratory effects on measurements of photosynthesis . 



The suppression of respiration affects certain measure- 

 ments of photosynthesis. Figure h shows the net oxygen 

 exchange of Anacystis for several wavelengths. The broken 



20 



60 80 100 120 140 160 



PERCENT OF COMPENSATING LIGHT 



200 -220 



curves for chlorophyll a regions make obvious the reasons 

 why Emerson measured high efficiency for this region while 

 others measured low efficiencies, it all depends where on 

 the light curve the measurements were made. A similar ex- 

 planation suffices for "negative enhancecient" or "de-enhance- 



