404 



G. C. McLeod, G. A. Hudock, and R. P. Levine 



dioxide fixation decreases in a manner almost identical to that of the 

 chlorophyll content during growth in the dark. On return to the light, 

 there is a lag period similar in length to that observed for chlorophyll 

 synthesis and then a rapid rise in the rate of carbon dioxide fixation which 

 is followed by a return to a steady state level comparable to that of the 

 light grown cells (^) . The decay of the carbon dioxide fixation during 

 the light period indicates an increased respiration during the synthesis of 

 chlorophyll . 



A plot of the oxygen evolution against chlorophyll content during blea- 

 ching and regreening is given in Figure 4. In the dark, after a lag period 

 of one generation, oxygen evolution decreases two-fold with each cell 

 division. In the light, following a lag period, there is a small but recur- 

 ring oxygen evolution similar to that reported by Fork ^ K Above chloro- 

 phyll levels of 0.5 to 0.7 ug/lO*^ cells, there is a rapid increase in the 

 rate of oxygen evolution. The maximum rate is not attained until the nor- 

 mal chlorophyll complement of 1 .5 to 2.0 ug/lO^ cells is restored. 



laor 



z 



3 



> 



UJ 



z 

 o 



o 

 > 



z 



UJ 



30 



^G CHLOROPHYLL / 10 CELLS 



Figure 4. Development of oxygen evolution in a regreening culture of 

 dark-grown y-2. Oxygen evolution in relative units is plotted as a fun- 

 ction of botTf time and chlorophyll content. 



