388 



Photosynthesis 



100 

 80 



w 



\60 

 t 



•40 



20 



2 



I 10 12 14 



HOUR OF OAY 



16 18 20 22 24 



Fig. 1. Fluctuating light intensity 

 in the culturing of Chlorella. 



In the light reaction, one molecule of O2 will develop per molecule of Chloro- 

 phyll, with, however, a quantum requirement, not of 3, but of 1. This at first 

 appears to contradict the laws of energy. However, during the dark period follow- 

 ing the end of illumination it can be observed manometrically, under suitable con- 

 ditions, that two-thirds of the oxygen gas develop during the light period undergoes 



flC 1 1 1 1 1 3 



¥00 ¥20 WO ¥60 ¥80 500rap.520 



Fig. 2. Action spectrum of blue-green light. 



HOURS ILLUMINATED 



Fig. 3. Oxygen gas produced at constant 

 illumination with green light with a small 

 quantity of blue-green light added (nve-hour 

 experiment). 



a back reaction, with restoration of the original condition wherein light can again 

 produce O2 as before 5 . Thus, if the light reaction is not considered by itself, but 

 together with the dark reaction, all is in order energetically. 



Closer study showed that in the dark reaction the oxygen of carbonic acid was 

 so loosened that, with the help of the energy of respiration, one quantum then 

 sufficed to produce one molecule of O2. The carbonic acid derivative with the 

 loosened oxygen is probably a peroxide. In order not to go beyond the facts, we 

 may call it the "photolyte" of photosynthesis. 



If we write the light and dark reactions of photosynthesis one after the other, we 

 obtain (Chi, Chlorophyll) : 



(Light) 3(ChlCO-j*) + 3N hr - 3C0 2 -> 3(ChlCO- 2 ) 3C 3(> 



(Dark) 2C 20 2 -■ 2C0 2 200,000 cal 



(Dark) 3(ChlCO- 2 ) - - 3(ChlC0 2 *) — 200,000 cal 



(Balance) ICO2 3N„hr - - IC + 10 2 



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[2] 

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