303 



Jack Myers 



feel obliged to include explanation of wavelength dependence of 

 light- saturation in current theory of enhancement. 



CH/LRACTEEISTICS IN ANACYSTIS AND CHLORELLA 



Quantitative Expression 



Enhancement may be expressed in several different ways. With- 

 out debating the merits of several possible ways I shall simply 

 state my own rationale. The enhancement effect at any wavelength 

 (\i or X2) is seen most clearly when observed on a large excess 

 of the complementary wavelength region. 



Suppose that we observe a rate of oxygen evolution pi at in- 

 tensity Ii of wavelength }^x and a rate p2 at intensity I2 of com- 

 planentary wavelength >^2 (using the subscript notation previously 

 defined). When Ii and I2 are presented together we observe a 

 rate pi2 which is larger than pi + p2. We can now express a 

 ratio or gain factor E referred to either wavelength alone: 



Pi 



5^^Pi£^_Pi (2) 



P2 



Equations (l) and (2) are peimltted by the important finding both 

 in Chlorella >^^ and in Anacystis"""^ that Ei and E2 are functions 

 of the ratios between, but not the absolute values of, Ii and I2 

 or pi and p2. 



Quantitative Relations 



Fig. 1 shows El vs. P2/P1 (a) and E2 vs. pi/p2 (b) from ex- 

 perimental data on Chlorella^^*^® and Anacystis.''"'^ There are 

 several aspects of Importance. Each curve shows an initial 

 linear segment and a final plateau at which Ei or E2 reaches a 

 maximum value. Curvature between the two regions may be attrib- 

 uted to several causes, one of which is clearly evident. Because 

 of great differences in absorption between 650 and 710 my. in 

 Chlorella or between 620 and 700 mn in Anacystis, it is impossi- 

 ble to maintain a constant ratio of Ii and I2 (or pi and P2) 



