THE CHEMICAL PROCESSES IN PLANT RESPIRATION 121 



The later biochemical studies showed that in reality sugars 

 are considerably easier to oxidise than proteins. The modern 

 theories of biological oxidation processes make it possible to 

 furnish a satisfactory explanation for the respiration of sugar 

 by means of the theory of the participation of enzymes of fer- 

 mentation in the normal respiratory process. The theory of 

 the connection of the anaerobic with normal respiration of 

 course directly contradicts Detmer's views. The latter are not 

 based on a single experimentally established fact and are incom- 

 patible with many experimental results. This is an example 

 of the way in which purely speculative theories have been able 

 to appear even in more recent times as well as at the beginning 

 of the 19th century. 



In the seed-plants almost all living cells are provided with a 

 supply of sugars or other carbohydrates. All the polysaccha- 

 rides such as starch, hemi-celluloses, and inulin, as well as the 

 glucosides, break down easily in the protoplasm through the 

 action of specific enzymes, to form simple sugars, particularly 

 glucose and fructose, which as direct respiratory material 

 undergo an oxidative cleavage. 



Sugars and polysaccharides are also contained in large 

 amounts in various lower plants. The starch of the higher 

 plants is often replaced by glycogen while among the disaccha- 

 rides trehalose is especially common in fungi. There is never 

 lacking in these plants a supply of respiratory material which 

 furnishes fermentable hexoses by means of hydrolytic cleavage. 

 In the plants containing chlorophyll, as well as in those with- 

 out chlorophyll, the respiratory material is often deposited in 

 the form of fat. The conversion of fat to sugar is a process 

 which has not yet been done artificially but it proceeds easily 

 in Kving plant cells. ^ The respiration of fat is associated with 



CO2- 



a comparatively low value of ^^ ^^^ undoubtedly is effected 



by way of the intermediate stage of sugar. 



1 Leclere du Sablon. Compt. rend. 117: 524- 1893; up : 610. 1894; Maquenne. Ibid. 

 127:625. 1908. For the respiration of fat in the lower fungi see Flieg, O. Jahrb. f. wiss, 

 Bot. 61: 24. 1922. 



2Godlewski, E. Jahrb. f. wiss. Bot. 13: 524. 1882. 



