THE CHEMICAL PROCESSES IN PLANT RESPIRATION II5 



hydrocyanic acid unites with ferric ions and consequently this 

 causes a displacement of respiratory material from the regions 

 of oxidation, since ferric ions are said to be indispensable for 

 the oxidation. 



It is certainly very welcome to have physiological-chemical 

 theories of respiration finally arrive. Without doubt a thor- 

 ough explanation of various processes which are physiologically 

 important can be obtained only by drawing on the capillary 

 phenomena. Warburg himself^ expresses the opinion "that 

 the conception of respiration as a surface reaction will indicate 

 the way followed by the transformation of energy in the living 

 cell, " since the forces of surface tension perform work. More- 

 over, the assumption is not precluded that various supposed 

 "enzyme effects" might often be traced to the fact that the 

 particular process represents a boundary surface phenomenon 

 by which the concentration of the substances concerned in the 

 reaction is uncommonly high.'- However, in the field of plant 

 respiration some facts have not yet been harmonized with vari- 

 ous points of the Warburg theory as it now stands. Thus ferric 

 ions for the most part are not detectable in plant cells because 

 the iron exists in rather stable organic combination. On the 

 other hand, it would be premature to deny the participation of 

 peroxidases in the respiratory processes. According to Will- 

 statter, these enzymes are found to be entirely free from iron.^ 

 It is to be emphasized especially that sugars serve as the respira- 

 tory material of plants. A repetition of the Warburg model 

 experiment by Meyerhof^ shows that various amino acids but 

 no sugars are burned under these conditions. It would certainly 

 be most interesting to test fermented sugar solutions on the 

 Warburg model. Meyerhof declares that hexose phosphate is 

 hereby attacked. From the standpoint of the theory of genetic 

 connection of the anaerobic with normal respiration, the results 

 obtained by Meyerhof certainly do not contradict Warburg's 



1 Warburg, O. loc. cil. 



■ In this case the specific nature of the adsorbent is of secondary importance. Hence an 

 assumption of specific catalysts seems to be superfluous in many cases. 



3 Hence it is apparent that a biological activation of oxygen can also occur without the 

 assistance of ferric ions. [Note that the results of the later work of Willstatter and PoUinger 

 (loc. cit.) contradict this statement.] 



4 Meyerhof, O. und H. Weber. Biochem. Z. 135: 558. 1923. 



