YIELD OF PHOTOSYNTHESIS IN ALTERNATING LIGHT 



1437 



Table 34.1 

 Intermittency Factors for CMorella in Alternating Light" (after Warburg 1919) 



t, sec 15 Ts 0.38 0.15 0.038 0.015 0.0038 0.0038'' 0.0038' 



i,E 1.14 1.36 1.46 1.56 1.77 1.72 1.96 1.88 1.0 



" High light intensity, 25° C, [CO2] = 9.1 X 10"* mole/1. 

 '' [CO2] = 136 X 10^-^ 

 ' Low /. 



pretation caused Warburg (1919) to undertake new experiments on the 

 effect of alternating light, in which care was taken to provide an abundant 

 supply of carbon dioxide. He found that the intermittency effect occurs 

 also under these conditions, where the explanation of Willstatter and Stoll 

 cannot apply. Table 34.1 shows that the intermittency factor, Ije, is 

 considerably larger than unity at [CO2] = 9.1 X 10"^ mole/1, (a concentra- 

 tion high enough to make carbon dioxide limitation implausible), and even 



Fig. 34.2. Yellow cosmos (Cosmos sulphureus) grown with equal periods of light and 

 darkness (after Garner and AUard 1931). Compare with fig. 34.1. 



at [CO2] = 136 X 10-^ mole/1. The last figure in the table shows that 

 intermittency has no influence on the rate in weak light {ijE = 1-0; in = 

 0.5). This is understandable; in weak hght (more precisely, within the 

 linear range of the light curves), the rate of photosynthesis is limited only 

 by the frequency of the absorption acts; the catalysts can co})e with all (he 

 intei'mediates produced by light without the formation of a backlog that 

 could be utilized in the dark. In strong light, on the other hand, the 



