354 



PHOTOMECHANICAL CONSIDERATIONS 



Fig. 2. Light-induced ESR signal in a sonic extract (cf. text) of 

 Chloropseudomonas ethylicum for light of )^xaaiX. ^^^ "^^- '^^^ signal 

 is obtained by numerical integration of the spectrometer recordings 

 (averaged over 2 spectra). Material was extracted from a 6 -day-old 

 culture. 



DISCUSSION 



These preliminary results show that 825 m/i light absorbed exclu- 

 sively by chlorophyll-770 in a green bacterium /;? vivo and in a sonic 

 fraction is effective in generating a ;?,/ ESR signal with a g-value 

 comparable to that of purple photosynthetic bacteria. This substantiates 

 the hypothesis that in this organism chlorophyll-770 is directly active 

 in photosynthesis. 



From Table 1 it might be concluded that light with Aj^^x. '^^^ ^^ 

 and absorbed by chlorobium chlorophyll is less effective in producing 

 unpaired electrons than is light with Xmax. 825 m/i. This conclusion, 

 however, would be justified only if the sample were not totally absorb- 



