232 Scientific Proceedings (128) 



the necessity for this substance in the nutrition of the tubercle 

 bacillus is obvious. 



112 (2072) 



The action of potassium cyanide on the chlorophyll 

 mechanism of Nereocystis. 



By E. J. LUND and VESTA HOLT (by invitation). 



[From the Paget Sound Marine Biological Laboratory, Friday 

 Harbor, Washington.} 



In connection with studies on the nature of the action of 

 cyanide on cell respiration, it seemed of interest to test the effect 

 which cyanide might have upon the mechanism of photosynthesis. 



Strips lx 10 cm. cut from the frond of the large, Pacific coast 

 kelp Nereocystis were used, and oxygen production was taken as 

 a measure of photosynthesis using Winkler's method for deter- 

 mination of oxygen. 



That potassium cyanide (.00008 mol in the experiment given) 

 can produce an apparently complete but reversible inhibition of 

 photosynthesis is shown by the following condensed statement of 

 results from a typical experiment. 



TABLE I. 



Each number in the table is the average quantity of oxygen produced ( + ), 

 or consumed ( — ) in three duplicate determinations. Concentration of 

 KNC in first test, .00008 mol. 



Strip placed in. 



First test. 



Second test. 

 All in light. 

 No KNC. 



0 2 in c.c. 

 thiosulfate. 



0 2 in c.c. 

 thiosulfate. 



Light 



+6.65 



+6.89 



Light KNC 



+ .18 



+6.82 



Darkness 



—1.10 



+6.63 



Darkness KNC 



— .39 



+5.80 



4 In this paper the term fat is used as a convenient expression for the 

 ether acetone soluble substances. 



