CHEMICAL COMPOSITION OF PLANTS 69 



disintegrating protein substances (papain, peptase, tryptase, and 

 others) as well as other compounds, the molecules of which possess 

 the same type of connections as proteins (urease acting on urea, 

 arginase decomposing arginin, and others); (3) glucosidases 

 hydrolyzing glucosides; (4) esterases decomposing compounds 

 having ester linkages (Hpase); and (5) several other enzymes. 



The most important representatives of the group of desmolases 

 are the enzymes by means of which the processes of respiration 

 and fermentation are activated. These processes represent 

 sources of free energy, indispensable for the vital activity of 

 organisms. They will be further discussed when these problems 

 are being examined in Chap. IV. 



17. Synthetic Processes during Germination. The Utiliza- 

 tion of Carbohydrates and Fats in Germinating Seeds. — The 

 metabohsm of organic substances during the germination of 

 seeds does not terminate with the formation of the final products 

 of hydrolysis, viz., simple sugars from starch and other poly- 

 saccharides, glycerin and fatty acids from fats, and mixtures 

 of different amino acids from protein substances. All these 

 processes of disintegration further pass into processes of syn- 

 thesis; for the phenomenon of germination represents not only 

 an expenditure of accumulated reserves but also the formation 

 of new, vitally active organs. The interrelations of disinte- 

 gration and synthesis are manifested by the gradual emptying 

 of those parts of the seed that serve as storage organs, viz., the 

 cotyledons and endosperm, accompanied by their gradual shrink- 

 age and desiccation, and on the other hand by the rapid increase 

 in size of the parts of the embryo and the initiation of the vege- 

 tative organs of the young plant, its roots, stems, and leaves. In 

 order to isolate the digestion processes taking place during 

 germination for the purpose of studying them, the germinating 

 seeds are usually killed so as to preserve the enzymatic system. 

 This is achieved by applying autolysis: the soaked and finely 

 ground seeds are placed in an antiseptic solution such as chloro- 

 form or toluol that does not affect the activity of the enzymes 

 (see Art. 15). The study of synthetic processes during germina- 

 tion represents a far more difficult problem, for it is not possible 

 to create such conditions as are normal in synthesis. For this 

 reason, the synthetic processes in germinating seeds can be fol- 

 lowed only by comparing the changes in chemical composition 



