1946 KINETICS OF PHOTOSYNTHESIS CHAP. 37D 



about 10. However, this explanation does not apply to the results de- 

 scribed in sections 1 and 2, in which Emerson and Whittingham found 

 no dependence of the yield of photosynthesis in Chlorella on CO2 concentra- 

 tion in the range 0.2 to 5% CO2, in weak as well as in strong light, and 

 obtained minimum quantum requirements between 8.8 and 8.9 (in 5% 

 CO2) and 9.0 and 9.5 (in 0.2% CO2), according to Emerson (table 37D.3); 

 and betw^een 9.9 in 0.037 M HCO3-, and 10.7 in 0.26 M HCO3-, according 

 to Whittingham (table 37D.1). True, Gaffron (c/. sections 1 and 2) found 

 an increase in photosynthesis in acid-grown algae with increasing [CO2], up 

 to and above 2% ; but this effect was noted in saturating light ; and the ulti- 

 mate level of saturation was not higher for the algae showing it than for the 

 algae grown in bicarbonate and showing no [CO2] dependence down to 



0.2%. 



The quantum yields obtained by Emerson, Rieke, and others, m earlier 

 experiments in phosphate buffers equilibrated wdth 5% CO2, also did not 

 differ from those they observed in buffer No. 9, by more than 10-15% 

 (p. 1095). Therefore, the reason for the contradictory findings of Warburg 

 and co-workers, could not lie simply in different carbon dioxide concentra- 

 tion. Rather, it must be sought in the totahty of the conditions used, in- 

 cluding, in addition to high CO2 concentration, also intermittency of illu- 

 mination, and certain procedures in the culturing of the algae. 



Warburg called these results "the end of a long road . . . which could 

 be foreseen for several years, but was hard to reach." In Warburg and 

 Burk's earlier paper (1950) the statement had been made that "in a per- 

 fect world, photosynthesis is perfect, too"; Warburg now repeated this 

 assertion, implying that the anticipated perfection has now been experi- 

 mentally reached. 



Warburg, Geleick and Briese (1952) described additional experiments on 

 the yield in carbonate buffers. Using a thin suspension, and compensating 

 respiration with white light, they found, in buffer No. 9, a quantum re- 

 quirement of 9 to 10 for added green hght, in agreement with Emerson and 

 others. In the "new buffer" (95 parts 0.2 M HCO3- + 5 parts 0.2 M CO3— ; 

 K+, Na+ or K+ + Na+ could be used as cations; Li+ or Cs+ proved un- 

 suitable) the yields were much better. However, if cells were washed twice 

 with this buffer before resuspending them for the measurement (as has been 

 customary in working with buffer No. 9), the quantum requirement was 

 found to be high, and rising with time— e. g., 6.75 in the first hour and 11.6 

 in the third hour; in the fourth hour, photosynthesis was replaced by 

 photoxidation. If washing was omitted, a quantum requirement of 3.95 

 was found in the first hour, and 4.25 in the fourth hour. The damaging 

 effect of washing was attributed by Warburg ei al. to bicarbonate penetra- 

 tion into the cells (c/. section 1 above). 



