THE ENERGETICS OF PHOTOSYNTHESIS 83 



Time of illumination: 60 min. 



h(, = —215.5 mm 



h = -220.0 mm 



ho — // = 4.5 mm 



xoj = {/lo — h)K(), = 11.0 ;ul 



, , 60 X 24.8 X0.033 + 0.5 X 60 X 1.0 X 0.19 



^/•^ 11.0 + 1 X3.5 ^-^^ 



As discussed in § 30, the number of quanta absorbed in blue-green has to be 

 multiplied by 0.5 and the respiration at rest taken into consideration. 



§ 34 The Carbon Dioxide Outburst 



Emerson et al. (22, 23) criticized manometry stating that in the first 

 minutes of illumination Chlorella not only absorbs but also removes COo. 

 Accordingly ^/ ^ of Warburg's manometric efTect would be due not to COo 

 reduction but to COo development. Thus, ^/^ x (x\ Oo would be measured 

 instead of x ^1 Oo, and the remaining ^/ ^ x ^A would be not O.; but CO2. 

 This would explain why Warburg and Burk found such low quantum re- 

 quirements. The real quantum requirement should therefore be three 

 times higher. It should be 9 instead of 3. There is, of course, no evidence 

 whatsoever to support such a hypothesis. Although this photochemically 

 and physiologically incomprehensible COo outburst is still mentioned by 

 some authors, it has never been demonstrated in quantum yield experiments 

 (44). As it is now possible to measure the quantum requirement in experi- 

 ments lasting several hours, the mysterious CO2 outburst — if it really does 

 occur in the first minutes of illumination — must be attributed to faulty mano- 

 metric technique. 



If there were any outburst of COo, the pressure changes would be greater 

 at the onset of illumination than later. The photosynthetic quotient at the 

 beginning of the experiment would also differ from that noted later. The 

 quotient would initially be strongly positive and even attain values as high 

 as +4. Warburg and Kubowitz (38, 39) established that neither abnormal 

 high initial pressures nor abnormal photosynthetic quotient values are ob- 

 tained. If the pressure changes are recorded at short intervals, it makes no 

 difference whether the quantum requirement is calculated for the total dura- 

 tion of the experiment or for the duration of illumination only. However, 

 at high light intensity a kind of COo outburst has been observed by Warburg 

 too. At such intensities, a sharp reversal of negative to positive pressure 

 changes can occur and lead to the formation of foam bubbles. When using 

 the modern experimental equipment and when all the experimental conditions 

 are fulfilled, Warburg et al. have never observed any outburst of COo. 



Emerson observed the strange effect when using the two- vessel method. 

 However, Warburg (43, 64) and Brown and Whittingham (8) pointed out 

 that the main prerequisite of the method was not fulfilled. Instead of both 

 vessels being illuminated simultaneously, one was illuminated 8 to 24 hours 

 after the other. It is essential to the two-vessel method that exactly the same 



