394 



Photosynthesis 



In the experiment of Fig. 9 the fluoride concentration was only 7V/1000, and 

 here one sees a great difference anaerobically and aerobically. Anaerobically the 

 decomposition is very extensive, but aerobically it is small. 



The more the glutamic acid is destroyed, just so much the more is the photo- 

 synthesis inhibited. For example, two different concentrations of fluoride were 

 added to aliquot Chlorella suspensions under aerobic conditions, and the glutamic 

 acid content and photosynthesis measured. Table 2 shows how closely decompo- 

 sition of glutamic acid and inhibition of photosynthesis parallel each other. 



Wo, 



Suspension 

 of Chlorella 



2N I actio acid 



Fig. 10. 



Manometric vessel for 



experiments with radioactive 



C0 2 . 



Continuation of these experiments brought forth a further connection between 

 glutamic acid and CO 2. A study of the binding of CO2 by Chlorella at different 

 pressures of CO2 showed that the labile CO2 is not only bound as the a-carboxyl of 

 glutamic acid but in addition an equal quantity of CO2 is dissociably bound under 

 aerobic conditions. This dissociable CO2 is also given off when the glutamic acid 

 in the cells is decomposed. The Saturation value of the dissociating CO2 is very 

 nearly equal to the glutamic acid content of the cells. The formation of carbamino- 

 glutamic acid is perhaps involved in the dissociable complex. 



In conclusion I may mention further that we have begun to study the behavicr 

 of amino acids in photosynthesis with the help of radioactive CO2. The main com- 

 partment of a manometric vessel (Fig. 10) is filled with a Suspension of Chlorella, 

 the Siamese side arm in one part with C 14 -carbonate and the other part with excess 

 lactic acid. Upon tipping the acid onto the carbonate, a pressure of radioactive CO2 



