FLUORESCENCE YIELD OF CHLOROPHYLL 



115 



o 



o 



CO 

 UJ 



q: 

 o 



3 



proceeding stepwise to higher ones. When the intensities used were 

 not too great, it was possible to retrace the curve by going from high 

 to low intensities and also to check random points. 



Figure 1 shows a fluorescence intensity versus irradiation trace tor 

 Chlorella in water swept continuously with 4% carbon dioxide in air. 

 There is a break in the curve at low intensities. One observes that 



LOW CO2 



HIGH COc 



C= Region of Compensotion 

 S= Onset of Saturation 



IRRADIATION 



Fig. 2. Fluorescence intensity versus irradiation intensity for Chlorella in water 

 swept with ordinaty and COa-enriched air. 



the curve between compensatioii and saturation, if extrapolated, 

 would pass below zero on the ordinate scale. There is some uncer- 

 tainty about the exact shape of the curve at low intensities — most 

 probably there is a gently decreasing slope with diminishing irradia- 

 tion, but a relatively sharp bend in the region of compensation. The 

 slope at approximately half compensation can be seen to be roughly 

 half that of the value between compensation and saturation. Above 

 saturation, the well-known rise of the fluorescence was observed. 

 The slope below compensation was somewhat influenced by the 



