126 The Maximum Efficiency of Photosynthesis 



Finally all light was turned off: 



No. 5 No. 3 



10' dark— 11 10' dark — 6 



10' xo 2 = — 12 -4 cu - mm - 

 60' xo 2 = -~ 74 cu - mm -' 



74 

 that is, - — ■ 100 = 18% of the cell volume/hr. 

 420 

 At (J - AJ) in vessel 5, - 45 mm. were produced in 10'. The light action was therefore 45 + 12 



= 57 mm. in 10'. Assuming a value of y = 1.0, this meansjo 2 = 57 !- 42 6 == 485 cu - mm - 



O-2/hr., or 485/74 = 6.5 times respiration. 



This experiment shows that 1) the efficiency of the added red light was essen- 

 tially the same whether the respiration was overcompensated from above or from 

 below, with white light or with red-yellow light; 2) a quantum requirement of 3.5 

 was obtained when respiration was 6.5 times compensated with a red-yellow light 

 and a value of 3.0 when respiration was similarly overcompensated with white light. 



Experiment 9 



August 5, 1949, Woods Hole 



Culture medium, pH 5. In vessels 5 and 3, gas phase 5°„ C0 2 in air. In vessel 34 air, in the 

 two sidearms NaOH. In each aessel 230 cu. mm. of cells, suspended in 7 ml. culture medium. 



AJ = 5.7 



No. 5 No. 3 



v = 13.913 v F == 7.00 v =- 17.993 v F 7.00 



k'o 2 == 0.665 £'co 2 == 1-253 k G , =- 1-046 k C o, 1-634 



Respiration not compensated 

 20' dark — 27.5 20' AJ — 7 20' dark — 13 20' AJ — 2 



20' H' + 20.5 mm. H + 11 mm. 



yo2 = ; 23.6 cu. mm. | „ = _ 82 

 yco-2 = — 1^-3 cu. mm. | ' 



1 AJ X 20 



23.6 



4.8 



Respiration overcompensated 

 No. 5 No. 3 



20' J+ 57.5 20'(.7+ 47) + 76 20' J - 39 20' (Jf + AJ) -f 48 



20' H' 4- 18.5 20' H + 9 



yo 2 = - 26 cu. mm. ) j 



^C02 = ~26 cu. mm. ) 



1 _ *J X 20 4 4 

 26 



