QUANTUM YIELD MEASUREMENTS BY THE MANOMETRIC METHOD 1097 



Tanada (1951) made a systematic study of the quantum yield of the di- 

 atom Nayicula minima in dependence on ^va^"e length. This Mork will be 

 described in chapter 30 (p. 1173) ; what is significant for the purpose of the 

 present discussion is that the maximum yield obtained in carbonate buffer 

 No. 9 was 7o = 0.11(0.05), corresponding to a quantum requirement of 

 I/to = 9; and that the yield in acid phosphate buffer appeared to be, 

 at all light intensities, 5-10% lowei^ (and not 10-20% higher, as in ChloreUa) 

 than that in alkaline carbonate buffer. In this case, Warbui'g's attribution 

 of a ciuantum requirement of ^^ 10 to a ''nonphj'siological" pll does not 

 seem plausible. 



Similarly to Kok (p. 1113), Tanada found the quantum yield to depend 

 on the age of the culture. Both the quantum yield in weak light and the 

 maximum rate in strong light dropped sharply from their original values 

 (7o = 0.115, P™^" = 3.0 mm^O./mm^ cells hr), between the sixth and the 

 eighth day of cultivation (70 = 0.07; P"'^" = 1.0 on the eighth day); the 

 decline continued steadily but more slowly for the next 12 days until, on 

 the 20th day, 7u was down to 0.0() and P""*^ was down to 0.75. 



We thus see that a whole series of manometric determinations of the 

 maximum quantum yield, applied to green higher plants, green algae, 

 blue-green algae and diatoms, and made in acid solutions as well as in car- 

 bonate buffers, gave 7„iax values of 0.1 ± 0.02. With the exception of 

 Emerson and Lewis' measurements, which have revealed the carbon di- 

 oxide burst, they were all carried out under conditions when the burst, 

 if it did occur at all, was either absorbed by the medium or minimized by 

 the averaging of results over an extended period of time. Many of the 

 experiments were performed in somewhat stronger light (up to ten times 

 that used by Warburg), and this, too, is Hkely to minimize the effects of 

 the burst. The experiments of Emerson and Lewis, and of Rieke, carried 

 out under exact adherence to the Warburg-Negelein procedure, showed 

 that Warburg's results can be duplicated, if the carbon dioxide burst is 

 treated as part of normal gas liberation by photosynthesis. 



We now turn to the other side in the controversy — investigations in 

 which Warburg and Negelein's results were confirmed imder conditions 

 which did not seem to admit of the interpretation suggested by Emerson 

 and Lewis. 



First, we have to mention the investigation by Eichhoft' (1939), carried 

 out in Noddack's lalioratory. Iilichhoft" suspended Chlorclla cells in car- 

 bonate-bicarbonate buffers and measured the quantum yield after a prelimi- 

 nary illumination for 15 or 30 min. (obviously these two precautions should 

 have prevented the carbon dioxide burst from affecting the results) . Eich- 

 hoff worked either with a "dense" suspension of ChloreUa pyrenoidosa, 



