The Maximum Efficiency of Photosynthesis : A Rediscovery 



97 



2. Manometric pressure changes effected by red light at 20 n C, when respiration was over- 



compensated by white light. pH 5.0. gas phase 5% CO-j in air. Actinometer for red light 5.4 



mm 3 . 0> min. TT 



Vessel I Vessel II 



v = 13.913, vf = 7.00 v' = 17.993, v' ¥ = 7.00 



25 min white 



87.5 mm. 25 min white - red = -j 110 mm. 



Action of red light - 22.5 mm in 25 min. 



30 min white 



78 mm 30 min white - red = 



91.5 mm 



Action of red light - 13.5 mm in 30 min. 



xo» in 25 min 30.3 mm 3 | CO2 



XCO2 m 25 min — 27.2 mm 3 | ' O2 



1_ hv_ 25 ■ 5.4 

 " Oo 30.3 



= 4.5 



0.9 



For the same culture, when the respiration was not compensated by white light, we obtained 



1 hv 60- 5.4 



3> == oT = 70.4 



4.6 



and 



CO2 

 2 



0.8 



3. Manometric vessels continuously illuminated for 27 hr. by white light of approximately 

 compensating intensity. — — , for the added red light, at the beginning and end of the expe- 

 riment. 



In hours 1 to 4 respiration compensated, 



In hours 20 to 22, respiration compensated, 



~0 



1 



= 4.5 (;- = - 1.0) 

 = 4.5 (-/ = - 1.0) 



In hours 27 to 28, respiration not compensated, — = 3.5 (y 



1.27) 



4. Comparison of same culture in M/10 carbonate buffer (pH 9) and in culture medium (pH 5). 



* It may be gathered from this example that the efficiency in the unnatural carbonate buffer is 

 only a fraction of the efficiency in culture medium. Many investigators believed that the efficiencies 

 in both solutions were equal, and this was one of the reasons why the quantum requirement of 4 

 was denied by them and the figures 10 to 12 accepted. 



7 Warburg, Zellphysiologie 



