678 



C. P. Whlttingham, et al. 



5 10 5 



TIME M MINUTES 



200 

 ISO 

 100 

 50 



S 10 IS 20 



TIME M MINUTES 





 WO 



n 



■m 



«o 



20 







Fig. 3. Ihe time course of loss of radioactivity in individual 

 conpounds when -'-^C is removed from the gas phase. 



A in the absence of INH,Ain the presence of INH. 



and thence transformed to the amino acids alanine and glutamic acid. The sum 

 total of radioactivity in serine together with glycine did not change after the 

 illumination ceased (Fig. 4). This indicates that (in the absence of I'JHj)at low 

 CO2 tensions glycine and serine are the main amino acids formed frcm the photo- 

 synthetic cycle, whereas in the dark iimediately following the light the main 

 cycle exit is to alanine and glutaiiate (the latter through the tricarboxylic 

 acid cycle). 



13 5 7 10 



MINUTES 



13 5 7 10 

 MINUTES 



5 7 R5" 

 MINUTES 



Pig. 4. The changes in time course in radioactivity upon 

 darkening after 5 min. illumination at 0.2% CO2. Solid 

 symbols, +1M; open symbols. Control. 



We have also shown^ '' that it is these corrpounds that are formed when radio- 

 active glucose is fed to Chlorella in the dark. Initially most of the radio- 

 activity from glucose appeared in sugar mono- and diphosphates and subsequently 

 in PGA and alanine, which lost activity after 15 min to aspartate and glutamata 



