CHEMICAL COMPOSITION OF PLANTS 65 



products are produced during the soaking and germination of 

 seeds. 



Enzymes represent the most important chemical reagents of 

 the cell. Judging from a number of properties, especially from 

 their easy destruction by heat and toxic substances, 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 nonliving 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. According to Palladin, plants treated by 

 one or another of these methods are killed. They should be 

 distinguished from plants that have died as a result, for example, 

 of boiling, in which not only the plasma is killed but all its 

 enzymes. 



In carefully killed plants, all the enzymes present in their 

 cells continue to function 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 

 degressions from ordinary enzymatic action, aiid many of them 

 will cease to work altogether. This probably happens because 

 in a dead cell coordination between the activities of the various 

 enzymes is lost. Often some of them begin to destroy others; 

 the reactions in the cell medium exercise a very great influence 

 upon the whole course of digestion. This phenomenon is called 

 ''autolysis" or ''autodigestion of the cells," in which the proteo- 

 Ijrtic enzymes usually continue to work longer than the others. 



It is not known in just what way the coordination of the work 

 of the enzymes is brought about in the living cell. According 

 to Oparin (1934), an important role belongs to the phenomenon 

 of adsorption of enzymes by colloids, especially by protein 

 substances. With the continuous alternation of the processes 

 of coagulation and dispersion of colloids in the living cell, at 

 times the activity of some of the enzymes weakens or stops 

 completely; with coagulation, at others, on the contrary, it 

 increases, with the dispersion of the colloids. Apparently there 

 is always in the cell a reserve of enzymes that are firmly adsorbed 

 by colloidal substances. Only a certain part of this reserve ii? 

 active, momentarily going into solution. 



