212 COLLEGE BOTANY 



Some enzymes act by causing oxidation, but most of the com- 

 mon ones act by causing hydration, and the process may be 

 illustrated by the following: 



OiaH M O n -|- H 2 O = C 6 H 12 O 6 + C 6 H 12 O 6 



(Sucrose) (Water) (Dextrose) (Levulose) 



Some of the more important of these enzymes are (a) the 

 diastases, which act on starches; (&) the cystase, which acts on 

 cellulose, and (c) the proteolitic enzymes, which act on proteins, 

 etc. The enzymes are of the very greatest importance in ger- 

 mination, in growth, in the ripening of fruits and in many other 

 activities of the plant. In fact, all the chemical processes of 

 the plant are probably the results of enzyme activities. 



Translocation. The digested products are soluble and in 

 this form are transported to the various parts of the plant for use 

 in growth. This is by no means thoroughly understood, and it 

 no doubt varies in both quantity and character of materials at 

 different seasons of the year and at different periods in the 

 plant's growth. We have already referred to the fact that 

 sugars are carried in the cell sap through the xylem parts of the 

 nbro-vascular bundles and that the digested proteins are carried 

 in the sieve tubes of the phloem of the same structures. 



It is very generally said that the movement through the 

 xylem is upward and the movement through the phloem is down- 

 ward, but these statements do not account for all the movements 

 of plant products in the plant. The presence of sugar and starch 

 in tubers, bulbs and .fleshy roots is a proof that these compounds 

 are carried downward from the chlorophyll-bearing parts in 

 which they are produced. It is very evident that the movement 

 of liquids within the plant is not well understood. 



