284 



PHOTOSYNTHESIS 



with the intermediate formation of formic acid (or more properly a 

 formic acid stage) ; this undergoes a similar rearrangement, with the 

 absorption of energy, to a peroxide and a subsequent splitting off of 

 oxygen : 



Intermediate products are not liberated from the chlorophyll. A re- 

 duction product as, for instance, a strong acid such as formic acid, would 

 not be freed from the magnesium, or only with destruction of the chloro- 

 phyll, which does not occur. All of the evidence of Willstatter and StoU 

 points to the conclusion that the reduction is carried straight through to 

 formaldehyde or its equivalent in degree of reduction. This fact is used 

 to support the conclusion that the reduction product remains combined 

 with the chlorophyll until a molecule of oxygen is removed. 



Formaldehyde does not remain combined with the chlorophyll. Willstat- 

 ter and Stoll have shown that chlorophyll is not capable of forming an 

 . addition product with formaldehyde. The liberation of formaldehyde from 

 the chlorophyll is brought about by the action of the carbonic acid or by 

 water. For the condensation of formaldehyde to sugars energy is pre- 

 sumably not necessary. 



The splitting out of oxygen from the j^eroxide also requires little en- 

 ergy. The radiant energy is used in the rearrangement of the chlorophyll- 

 carbonic acid complex to the peroxide. It is possible that the splitting of 

 the peroxide is accomplished by enzyme activity. As has been discussed 

 in the section of this book dealing with the efifect of temperature and 



