186 PLANT PHYSIOLOGY 



N-, N.. 



>N. \ HO— C— OH -> N^\ 



< XMg + I ^Mg— O— C— OH 







This compound of chlorophyll and carbon dioxide directly 

 absorbs light energy and is further transformed into the peroxide 

 form. 



>\ 



< \Mg— O— CH< I 

 NN-ff/ ^0 



>/ 



Finally, the peroxide decomposes under the influence of 

 enzymes, present in the stroma of the chloroplast or in the proto- 

 plasm, releasing free oxygen and formaldehyde, while chloro- 

 phyll is reduced to its initial form. 



N, 



>Mg + HCHO + O2 



Willstatter's theory, explains the sensitizing action of chloro- 

 phyll. It is supported by the fact that the dry substance of the 

 green leaf absorbs carbon dioxide almost as avidly as venous 

 blood or alkaline solutions. The decomposition of the peroxide 

 compound is accomplished by an enzyme belonging to the group 

 of catalases, i.e., enzymes that split hydrogen peroxide with the 

 liberation of molecular oxygen. 



Photosynthesis, therefore, may proceed through three phases 

 at least : the union of carbon dioxide to chlorophyll, the internal 

 rearrangement of atoms in the compound with transformation 

 into a peroxide form, and the decomposition of the peroxide 



