THE ENERGETICS OF PHOTOSYNTHESIS 



89 



3 



min 



Fig. 36. Splitting of photosynthesis into a Hght reaction and a back reaction. 22 \A cells 

 per vessel. Respiration compensated. 20° C. Mean of five values, h: compensation 

 light + measured green light (5460 A). /2.- compensation light without measured green 

 light, g: gain. Tan a = 2.35, <p = 1.1; tan /3 = 0.53, <- = 0.26 (Warburg et al, Zschr. 

 Naturf.). 



Numerical example: 



Vessel 1: AV,, = 1.321 mnr 



Kco, = 1.910 mm2 



Vessel 2: A'V., = 0.915 mm^ K'co, = 1-503 mm^ 



Absorbed intensity of the measured green light (5460 A) : / = 7.36 (A quanta/min. 



a. The measured light is added and removed 90 times at 1 -minute intervals. 

 The pressure changes are not noted every minute but only after 180 min- 

 utes. 



h' = 49.0 mn:i /; = 20.5 mm 



With the aid of equation 16, we find for the photosynthetic quotient 



7 = -1.22 



For vessel 2 we have, according to equation 12, 



xo, = h' 



K o,K CO, 



K'o^ -f yK'i 



= 3.51 /;' 



or 



Xo, = 49.0 X 3.51 = 172 ^1 



The absorbed intensity in 90 min is 



it = 7.36 X 90 = 663 /xl quanta/min 



so that the quantum yield is 



<p = xojit = 0.260 



b. The measured hght is added and removed at 3-minute intervals and the 

 cycle of 6 min is repeated 5 times. The pressure changes are noted from 



mmute to mmute 



h' = S mm // = 3.5 mm 



7 = -1.21 



