329 



Govind jee 



The ratio of intensities of the 718 and the 685 m|a fluores- 

 cence bands at -196° C is higher when chlorophyll a is excited, 

 than when phycocyanin is excited. This suggests two separate 

 chlorophyll a systems: (1) one system in which the energy prefer- 

 entially goes to the part of chlorophyll a that fluoresces at 

 718 ni|j,; and (2) another system in which the energy preferentially 

 goes to the chlorophyll a that fluoresces at 685 m|a. 



The 750 mja peak in the excitation spectrum (see figure 13) is 

 observed consistently, and is perhaps due to P 750 N. The 760 mp, 

 shoulder in the fluorescence spectrum is due to the fluorescence 

 of this pigment. The 696 m[x band may be due to the "unknown trap" 

 of photosystem II (cf. also 57 and 58). 



700 750 



WAVELENGTH, m;< 



Figure 12. Fluorescence emission spectrum of 

 Anacyst is. (after Spencer and Govind jee). 



600 700 



WAVELENGTH, m/i 



Figure 13. Fluorescence excitation spectrum of 

 Anacyst is at two temperatures (after Spencer and 

 Govind jee) . 



