214 



H. TAMIYA, K. MIYACHI, T. HIROKAWA 



photochemical decay. We have made studies on the processes of for- 

 mation and decay of this agent which, for convenience, we shall de- 

 note as R. In this paper we report the results of experiments which 

 lead to the conclusion that R is formed photochemically concomitant 

 with oxygen evolution, reacts with oxygen and quinone, functions as a 

 reducing agent in CO2 fixation, and is involved in the cyanide inhibi- 

 tion of photosynthesis. 



10 



20 30 " 50 



TIME IN MINUTES 



60 



70 



Fig. 2 Effect of air on the course of formation of R in the Ught. Air was intro 

 duced 45 minutes before the beginning of illumination. 



The experimental organism was Chlorella ellipsoidea, w^hich was 

 grown as previously described. In most cases the experimental tem- 

 perature was 25 °C. Preillumination was accomplished while the sus- 

 pension was flushed with N2. The C^*02 was provided in the dark in an 

 atmosphere of N2. 



We were able to confirm that nearly all the effect of preillumina- 

 tion is achieved within 30 seconds of light and that background fix- 

 ation by nonpreilluminated cells is negligible in short time intervals. 

 Consequently the C^'' fixed in 30 seconds of light is taken as a meas- 

 ure of R. 



Figure 1 shows that, after prolonged darkness, R was formed 

 with a characteristic induction period. Two transient depressions 

 in the time course of R increase may be noted — the first occurring at 

 about the 10th to the 15th second, the other between the 2nd and 

 5th minute. The steady-state R level obtained in the light was about 

 5 to 7 X 10~^ molar C02-equivalent per gram dry weight of algae. 



