CHEMILUMINESCENCE OF ALGAE 



135 



co-workers have shown, the spectral distribution of chemilumines- 

 cence is experimentally indistinguishable from that of the fluores- 

 cence of chlorophyll but is several orders of magnitude less intense. 

 The curves presented are not decay curves in the accustomed sense. 

 They are graphs of the intensity of chemiluminescence followed dur- 

 ing a period of irradiation — with rapidly pulsed light. 



12 3 4 5 



IRRADIATION (MINUTES) 



Fig. 1. Time course of delayed luminescence during irradiation of Chlorella in 



water. Nitrogen atmosphere. 



The Chlorella were frequently suspended in water. This reduced 

 the problem of equilibration with the gas used in sweeping and facili- 

 tated rapid changes of sweeping gas composition. Experiments were 

 also conducted using various buffer mixtures to make certain that 

 the aqueous mediinn introduced no artifacts. Figure 1 shows the 

 variation of the intensity of chemiluminescence during the course 

 of the irradiation. Chlorella were suspended in water and swept 

 with oxygen-free (less than 10~^ mm. Hg) nitrogen. The rapid initial 

 rise is followed by a deep minimum after which the luminescence rises 

 to a steady-state intensity, which could be maintained for a con- 

 siderable period of time. The dotted line at about intensity 1.5 indi- 

 cates background and stray signal. Figure 2 shows the chemilumines- 

 cence curve for Chlorella suspended in nutrient and swept with 2% 

 carbon dioxide in air. Irregularities such as those observed at 10 to 

 20 seconds are customarily found. The chemiluminescence then falls 

 to a very low level. The ratio of the initial spike height to the steady- 

 state level is 10 to 15: 1. 



