214 TEXTBOOK OF PLANT PHYSIOLOGY 



centrated solution of glucose with the aid of maltase, Croft Hill 

 (1898), for instance, obtained not maltose, but isomaltose. 

 Recently, however, the French scientist Bourquelot was successful 

 in synthesizing with the aid of enzymes, a large number of gluco- 

 sides from the products of their decomposition, and in such a way 

 that the possibility of enzymatic synthesis was irrefutably demon- 

 strated. It can be assumed with a great degree of probability, 

 therefore, that syntheses of polysaccharides, fats and proteins, 

 which are so common in plant cells, proceed under the influence of 

 the same enzymes which cause their decomposition. The condi- 

 tions under which such enzymatic syntheses take place are not as 

 yet fully known. It seems to be certain, however, that the con- 

 tinuous removal of water from the sphere of the reaction is neces- 

 sary. Syntheses of this kind most likely take place in maturing 

 seeds, where the reserve substances are found. The hydrolytic 

 products are produced during the soaking and germinating of 

 seeds. Judging from a number of properties, especially from their 

 easy destruction by heat and toxins, enzymes must be closely 

 related to living protoplasm. Still, considering the ease with 

 which they may be dissolved and precipitated, one is forced to 

 classify them with non-living substances. With the aid of more 

 refined methods of killing, such as desiccation, freezing, or the 

 action of antiseptics, such as chloroform, it is possible to kill the 

 cells of plants without destroying the enzymes found within them. 

 Plants, treated by one or another of these methods, according to 

 Palladin are killed. They should be distinguished from plants 

 which have died as a result, for example, of boiling, in which not 

 only the plasma is killed, but all its enzymes as well. 



In carefully killed plants, all the enzymes present in their cells 

 continue the work for a time, and therefore this method is very 

 often used in the study of enzyme activity. However, very soon 

 there are revealed in such cells many irregularities and digressions 

 from ordinary enzymatic action, and many of them will cease to 

 work altogether. This probably happens, because in a killed cell 

 coordination between the activities of the various enzymes is 

 lost. Often some of them begin to destroy others, the reaction of 

 the medium exercising a very great influence upon the whole per- 

 formance. This phenomenon is called "autolysis" or "auto- 

 digestion of the cells," in which the proteolytic enzymes usually 

 continue to work longer than the others. 



