139 



Ellen C. Weaver eind Norman I. Bishop 



The second class are termed "CO2" mutants because they have a 

 greatly reduced ability to photoreduce carbon dioxide with hydro- 

 gen, although the quinone-Hill reaction is relatively intact. One 

 of these, Mutant 8, shows no R signal at all, even though it has 

 abundant chlorophyll (^). Dr. Warren Butler's investigations on 

 this mutant (5) indicate that it lacks P7OO, but information on 

 this point for the other "COg" mutants is lacking. Fig. 1 illus- 

 trates the behavior of the cultures under consideration. 



LIGHT OFF 



S-SIGNflL 



LIGHT ON 



"COJ' MUTANT 



^^'V^ 



,AkU. 



S- SIGNAL 

 ONLY 



"Oj' MUTANT 



tW^V*"**'^**''*' 



R- SIGNAL 

 ONLY 



,.» M^'^V, '^*'^ 



WILD TYPE 



'H- 



f S-SIGNAL 



VV 



\JV 



■A**^ 



g- VALUE 

 H — ► 



T 



V 



I 



s a R 



SIGNALS 



^V*4MVr'^ 



Fig. 1 Comparison of the EPR spectra in mutant and wild type 

 Scenedesmus . Due to its long decay time, the S signal 

 can be seen in the absence of illumination, whereas the R signal 

 decays within seconds, g-value may be thought of as the EPR ana- 

 logue of wavelength as used in optical spectroscopy. All spectra 

 are made with suspensions containing approximately 5 x 10" cells 

 per milliliter and with identical instrumental parameters . 



