400 ENZYMES 



such as hydrogen peroxide, or dissolved oxygen in the pre- 

 sence of sensitizers such as sodium chloride. 



In addition to oxidative processes carried out in the plant 

 by these enzymes, they may play an important part in the 

 preparation of raw food-material in the soil. Thus Schreiner 

 and Reid f as the result of their experimental work have come 

 to the conclusion that enzymes, principally peroxidases, are 

 excreted by the roots, and so oxidize organic substances in 

 the soil. Oxidation was found to be most potent in the root- 

 hair regions and those places where the secondary roots are 

 developing. The older parts of the root and also the root-cap 

 do not produce these enzymes. The degree of the activity of 

 the enzymes in the soil depends upon the character of the soil ; 

 thus the presence of sodium nitrate accelerates the oxidative 

 processes, and, in brief, the most productive soils show the 

 most vigorous oxidation. On the other hand, the reverse 

 obtains in poor unproductive soils which contain substances 

 which interfere with the process. These deleterious agents 

 may be removed sometimes by suitable treatment, e.g. the 

 use of absorbing agents such as lamp-black. 



* Schreiner and Reid: " Bot. Gaz.," 1909, 47, 355. See also Schreiner and 

 Sullivan : id., 191 1, 51, 156, 273. 



FURTHER REFERENCES. 



Bayliss : " The Nature of Enzyme Action," London, 1919. 



Euler : " Allgemeine Chemie der Enzyme," Wiesbaden, 1910. 



Griiss : " Biologic und Kapillaranalyse der Enzyme," Berlin, 1912. 



Oppenheimer : " Die Fermente u. ihre Wirkung," Leipzig, 1910. 



Effront : " The Enzymes and their Applications " (translated by Prescott), 

 New York, 1902 ; " Biochemical Catalysts in Life and Industry," New York, 

 1917. 



Priestley : " Science Progress," 1913, 8, 113, 482. 



The following works of general reference will be 

 found of considerable value : 



Abderhalden: " Biochemisches Handlexikon," Berlin, 1911; " Handbuch 

 der Biochemischen Arbeitsmethoden," Berlin, 1910. 

 Czapek : " Biochemie der Pflanzen," Jena, 1905. 

 Nathansohn : " Stoffwechsel der Pflanzen," Leipzig, 1912. 

 Pammel : " Manual of Poisonous Plants," Iowa, 1911. 

 Thorpe : " Dictionary of Applied Chemistry," London. 

 Wehmer : " Die Pflanzenstoffe," Jena, 1911. 

 Zimmermann : " Botanical Microtechnique," London, 1896. 



