1888 KINETICS OF PHOTOSYNTHESIS CHAP. 37D 



theory of Gaffron and Franck- — chlorophyll-enveloping "narcotics" (per- 

 haps plant acids) . This explanation was supported by the observation {cj. 

 p. 909) that, in Chlorella, inhibition persisted even after cells had been trans- 

 ferred into a medium abundant in carbon dioxide. Osterlind (1952^) could 

 not confirm the last finding, and suggested that the induction effects ob- 

 served by Whittingham in Chlorella must have been different from those in 

 Scenedesmus quadricauda. 



Whittingham (c/. Emerson and Whittingham 1953) measured the rate of 

 photosynthesis of Chlorella pyrenoidosa at constant [CO2] (= 7 X 10~^ 

 mole/1.) as function of [HCOs"], in white hght of varying intensity. 

 Table 37D.I shows the results. 



Table 37D.I 



Rate of Photosynthesis of Chlorella at Different HCOs" Concentrations 

 [CO2] = 7 X 10~5 Mole per Liter (after Whittingham") 



(Volumes O2 per hour per volume of cells) 



" Of. Emerson and Whittingham (1953). 



Expressed in fraction of the yield in saturating white light (/ = 100), 

 the rates at all other white light intensities (3 to 44) are, according to Whit- 

 tingham, independent of [HCOs"], and of the correlated changes in pR, 

 within the limits of experimental error. The rates in the (relatively weak) 

 red light, from which the quantum yields shown in the last column were 

 calculated, are definitely independent of [HCOs"]. 



Since, in this study, the concentration of free carbon dioxide was in 

 itself saturating (or almost saturating), it is not astonishing that addition 

 of bicarbonate did not significantly improve the yield, particularly in weak 

 light, where the absolute rate is low. We recall that Osterlind found no 

 evidence of bicarbonate contribution to photosynthesis in Chlorella pyrenoi- 

 dosa even at much lower CO2 concentrations. 



In a not easily explainable contradiction to the findings of Whittingham 

 and Osterlind are the data of Gaffron (1953) and Rosenberg (1954), ob- 

 tained (by electrochemical pH determination) with both Chlorella pyrenoi- 

 dosa and Scenedesmus ohliquus. As described in more detail in section (b), 

 they found, in contrast to other observers, a decline in the yield of photosyn- 

 thesis of these algae with decreasing concentration of free carbon dioxide, 



