104 PROBLEMS IN PHOTOSYNTHESIS 



§ 43 Some Final Remarks 



The quantum requirement 3 determined by Warburg and Burk could not 

 be confirmed by various authors* who obtained values between 8 and 12. 

 For this reason, Warburg repeated his experiments of 1922 and 1923 in the 

 Max Planck Institute for Cell Physiology in Berlin-Dahlem and at the National 

 Cancer Institute, National Institutes of Health, Bethesda, and the Marine 

 Biological Laboratory, Woods Hole. He worked together with Burk and 

 others and used both the old and the improved methods. His earlier findings 

 were confirmed (11, 45, 46). The rather bitter controversy which ensued 

 seems quite out of date today, especially as recent investigations by Warburg 

 and Burk have completely changed views on photosynthesis energetics. It is 

 reo-rettable that nevertheless Emerson continued to criticize in a rather 

 polemical manner the fine results Warburg and Burk obtained. However, 

 his review (19) published in 1958 on the quantum yield of photosynthesis is 

 completely out of date. It intentionally ignores Warburg's work done since 

 1954, as, according to a footnote, the survey of literature was concluded in 

 September 1957. 



Although the opponents of Warburg mostly used manometry in their 

 experiments, this method was not considered to be accurate enough. Those 

 who have seen Warburg's highly experimental technique must refute this 

 objection. As long as some investigators utilizing manometry found quantum 

 requirements of 8 to 1 2, manometry was not criticized. In reality, Warburg's 

 manometric methods— an indispensable part of experimental biochemistry 

 today — and radiation measurement with such instruments as the bolometer 

 and the Ulbricht sphere, have reached a very high degree of perfection. 

 These methods are based upon the classical laws of gases and radiation. A 

 rejection of these methods would be tantamount to a rejection of these laws. 

 It is therefore a regrettable error to assume that other methods which are 

 more complicated and which are less well known to many investigators, such 

 as mass spectrography, infrared recording, paramagneto recording, etc., are 

 superior. If the findings obtained with such modern equipment do not 

 confirm the findings obtained with methods based upon well-established 

 classical principles, it is logical to conclude that they must be unsuitable for 

 experimental photosynthesis (42) . 



It is of course essential that all the conditions are fulfilled so that no objec- 

 tion can be sustained. To begin with, Chlorella must be cultivated in ap- 

 propriate culture media and under fluctuating light. The cell suspensions 

 used must be thin : light absorption must not be more than a few percent of the 

 incident light. Dense cell suspensions may not be used. Total absorption 

 of the incident light is not permissible. The cells must be young, as old cells 

 contain inactive chlorophyll. Small intensities of blue-green light have to 

 be added to the measured light. Traces of vanadium must be added to the 



* Daniels (16), Emerson and Lewis (22), Franck and Gaffron (25), Gabrielsen (26), Kok (28), 

 Wassink (65), Went (67), Yuan (70). 



