1580 



PHOTOCHEMISTRY OF CHLOROPHYLL 



CHAP. 35 



Tolmach inquired whether the oxygen evolution can be enhanced by 

 known metabohc intermediates; he found, in fact, that the addition to the 

 drop of 1 X 10-2 mole/1, phosphoglycerate (PGA) or pyruvate (PA) in- 



20 30 40 50 

 TIME (MINUTES) 



60 



70 80 



Fig. 35.19A. Photochemical O2 evolution from 3 mm.^ of separated spinach 

 chloroplasts (A) and from crude leaf juice (B,C), l)oth containing 3 ^g. Chi 

 (Tolmach 1951). Phosphoroscopic determination of O2 pressure in N2 gas flow 

 (9.6 cm.3 N2/min.), 10-12° C. 



creased the oxygen production by up to 16% of the stoichiometric equiva- 

 lent of the amount added (assuming that each molecule of PGA or PA can 

 consume 2 atoms hydrogen). Figure 35.19B shows the time curves of 



20 



30 40 50 60 



T'MF (MINUTES) 



Fig. 35.19B. Photochemical O2 evolution from 2.5 mm.^ crude spinach juice 

 with addition of 2.5 mm.^ water (A); and 0.02 M PGA (B) at 15° C. (Tolmach 

 1951). 9.6 cm.3 N2/min. Total O2 yields: 0.026 mm.» in (A), 0.095 mm.^ 

 in (B). 



oxygen consumption of chloroplasts suspended in cell sap, with and without 

 added PGA. The shape of the curves and the total additional oxygen 

 liberation varied widely, apparently in dependence of the physiological 



