Action of Potassium Cyanide on Nereocystis 233 



Photodynamic sensitization occurs when strips are exposed to 

 light in the presence of higher concentrations (in the experiment 

 cited below .00016 mol.) of cyanide. Injury occurs in propor- 

 tion to the concentration of cyanide, as shown by table 2, which 

 gives the degree of recovery of the strips, and the mechanism of 

 photosynthesis in terms of capacity to produce oxygen in pure 

 sea water in light, after previous treatment with KNC in light. 



TABLE n. 



Strips of equal area placed in cyanide solutions (column 1) for nine hours in 

 sunlight. Washed in sea water for eighteen hours and then tested for 

 phototynthesis in pure sea water. Numbers in column 2 give the amounts 

 of oxygen in c.e. thiosulfate produced ( + ) in a five-hour test. 



Strip 

 number. 



1. 



2. 



Condition of strip at end 

 of experiment. 



Cone, of KNC 

 in sea water. 



C*2 in c.c. 

 Thiosulfate. 



1 



Pure sea water 



+7.05 



Normal color. 



2 



.00016 mol. KNC 



+4.81 



Normal color. 



3 



.00032 mol. KNC 



+3.14 



Slight loss of color. 



4 



.00048 mol. KNC 



+1.86 



More loss of color. 



5 



.00064 mol. KNC 



+ .28 



Almost complete loss of color. 



6 



.0008 mol. KNC 



+ .41 



Almost complete loss of color. 



7 



.00112 mol. KNC 



+ .22 



Almost complete loss of color. 



8 



.002 mol. KNC 



— .31 



Complete loss of color. 



9 



.0032 mol. KNC 



— .13 



Complete loss of color. 



Solutions of cyanide in sea water (about .0006 mol.) which 

 produce permanent injury in light do not produce injury when 

 the strip is placed in darkness, all other conditions remaining 

 the same. 



The possible significance and full details of the experiments 

 will be given elsewhere. 



