30 



H. TAMIYA et al. 



VOL. 12 (1953) 



considerably weaker pliotosynthetic activity and lower chlorophyll content than the normal nascent 

 dark cells. It is evident that the transformation of light cells into dark cells involves, although not 

 manifested as a substantial increase in mass, an important anabohc and formative metabolism coupled 

 with the energy yielding aerobic metabolism, in which not only the endogenous substances, but also 

 certain inorganic materials taken from the circumambient solution are used as building blocks. 



HOURS 



IN THE 

 DARK 



9.5 



19 



30.5 



43 







A = 15 



A = 0.23 



^!^!pM<§M 



A=0.65 





.■A//M"/A",/m'A'//yA \, 



4=0,77 



A=0.9I 



3 4 5 6 1 

 CELL DIAMETER IN /i 



% 



30 



20 



W 



% 

 30 



20 



10 



% 

 30 



20 



10 



% 



30 



20 

 -\1C 



% 

 40 



30 



-\20 



W 



10 



Fig. 5. Distribution polygons of cell diameter 

 showing the transformation of light cells into 

 nascent dark cells in the dark. The starting 

 material was prepared from a dark-cell-rich 

 culture {A = 0.99) which was illuminated with 

 2000 lux light at 9°-io° C for 7 days. The re- 

 sulting light-cell-rich culture {A = 0.15) was 

 resuspended in normal culture medium, and the 

 main experiment was conducted in the dark at 

 15" C with provision of COg-enriched air. 



10 20 30 40 50 



HOURS IN THE DARK 



Fig. 6. Change of packed cell volume, cell number, 

 average cell volume and dark cell ratio during 

 the transformation of light cells into dark cells 

 under aerobic and anaerobic conditions. The data 

 of the aerobic experiment are the same as those 

 shown in Fig. 5. The anaerobic experiment was 

 performed by evacuating the cell suspension in 

 Thunberg's tubes; otherwise the condition was 

 the same as in control experiment. 



Some aspect of such constructive events occurring in the process was studiedin the e.xjierinient 

 reproduced in Fig. 7. In this experiment the contents of chlorophyll and phosphorus in cells were 

 followed during the transformation occurring in normal medium and in the dark. As may be seen, 

 the chlorophyll content in cells as well as the total amount of chlorophyll in the culture increased 

 appreciably during the dark process*. On the other hand, both the phosphorus content in cells and 

 the total amount of assimilated phosphorus in the culture remained unchanged during the process, 

 indicating that the anabolic metabolism of phosphorous compounds had been accomplished using the 

 phosphorus which had pre-existed in light cells. 



At the 53th hour of the dark experiment, when the transformation of light cells into nascent 

 dark cells seemed to have completed, the suspension was suddenly subjected to illumination (20,000 



It has been known that Chlovella can synthesize chlorophyll in the dark when it is grown 

 heterotrophically with provision of sugar as carbon source. 



References p. 40. 



