THE ENERGETICS OF PHOTOSYNTHESIS 53 



From equation 10 we find the amount of Oo produced to be 



Owing to the small CO2 partial pressure of the carbonate buflfer, the gas phase 

 contains very little COo and the manometrically observed pressure change is 

 equal to /?o,, so that 



Since V^ = 5000 ^1, V, = 10000 p\ and T = 298°, the value of A'o, is 0.5 

 mm^. 



When 200 /xl CO, are reduced, ,v„^ = 200 mI i.e. for A',,, = 0.5 the O., 

 partial pressure has been changed by 400 mm. The change of the CO.. partial 

 pressure after removal of 200 ^1 COo was only 2 mm, which is thus only 

 0.5% of the 0.2 partial pressure. It follows from this that making b = Z?,,, is 

 permissible. 



§ 21 Energy Turnover 



Warburg and Negelein (20, 30) were the first to study the question con- 

 cerning which fraction of absorbed radiation energy in photosynthesis could be 

 transformed to chemical energy. If the light energy absorbed is E and the 



Fig. 27. Relationship between the ab- 

 sorbed radiation energy E and the ac- 

 compHshed work U. 



tga,= lim -^ 



chemical work performed simultaneously — the increase in total energy — is 

 U, the quotient 



. = I (5) 



becomes of special interest. In Figure 27 the abscissa shows the light energy 

 absorbed per sec and the ordinate the chemical work performed per sec. We 

 can see from the curve that r/ changes with the intensity of the radiation ab- 

 sorbed. The more intensive the radiation, the smaller -q becomes, thus mak- 

 ing that portion transformed into chemical energy smaller. With decreasing 



