CHEMILUMINESCENXE OF ALG.^E 141 



only a minute, only a very small spike was observed. The previous steadj'-state 

 level was almost immediately- reached. However, after 5 or 10 minutes in the dark, 

 following an irradiation, the rhemiluminescence spike was considerably higher. 



Gaffron : It appears that the highest level of chemiluminescence you obtained 

 by adding successive bursts of carbon dioxide to Chlorella in oxygen-free and 

 carbon dioxide-free nitrogen is comparable to that which you found for Chlorella 

 in pure oxygen. The steady-state level of chemiluminescence appeared to be 

 highest in oxygen, lower in pure nitrogen, and lowest in the presence of carbon 

 dioxide, with or without oxygen. 



Brugger: This is correct. 



Limiry : You told me that Dr. Frank Allen and you had studied changes in the 

 absorption spectrum of Chlorella suspensions containing phenylurethane. Did 

 you look at any other inhibitors for their eflfeet on the spectrum? We have looked 

 at a number of inhibitors which do affect the light reaction and have detected 

 no changes in spectrum at all at high light intensities. We included agents which 

 quench the fluorescence. I wonder whether there is any indication that these 

 agents have a permanent absorptive effect on the chlorophyll. 



Brugger: Dr. Allen and I built a recording monochromatic photometer by 

 modii\-ing a Beckman DU spectrophotometer. We constructed a special cell and 

 cell holder and a detecting, ampUf^-ing and recording unit, consisting of a multi- 

 plier phototube, Leeds and Xorthrup DC microammeter, and Speedomax re- 

 corder. Our electronics *ere such that we bucked most of the photosignal and 

 amplified only the residual. We were able to repeat Dr. Duysens' observations on 

 changes in absorption. Chlorella in water containing 3 X 10 "^ M phenylurethane 

 appeared to show a slight shift to the red in the absorption spectrum. We beheve 

 that the complicating feature of the enhanced fluorescence due to the phenylure- 

 thane was eliminated by judicious use of filters. As there is a definitely tentative 

 character to our results, I do not wish to discuss them at length. 



