SO Agricultural Chemistry. 



of enzymes, designated as proteolytic in nature, alters the protein 

 compounds of the germinating seed ; an enzyme known as diastase 

 converts starch to dextrines and sugar; a lipase or fat splitting 

 enzyme alters fats only, while still another type of enzyme lib-i] 

 erates phosphorus, calcium and other ash constituents from or- 

 ganic compounds of the seed. Phytase, which occurs in wheat 

 arid other grains, is an example of the last mentioned class of 

 enzymes. It breaks up the compound known as phytin, produc- 

 ing simple soluble compounds of calcium, magnesium, potassium 

 and phosphorus. 



Consideration of this specific relation between enzymes and 

 organic compounds and extension of our knowledge concerning 

 the chemical structure of the substances involved therein have 

 led to a theory which likens the action of an enzyme to that 

 of a key upon a lock, in the sense that each key fits and trips 

 only the particular lock to which it is adapted. This is more 

 complete than the older theory, for it ascribes to the enzyme 

 power to reconstruct its specific compound just as the key can 

 lock as well as unlock. It is in harmony with the known re-j 

 versibility of some enzyme actions. 



The fragments of compounds resulting from enzymatic action 

 in the seed, combine with the oxygen of the air, always required 

 for germination, and either yield energy for the growth of the 

 young plant, or pass as soluble compounds with the sap into the 

 growing seedling, there to be reconstructed into compounds form- 

 ing the tissues of the young plant. 



By the time the reserve compounds of the seed are exhausted 

 the young plant is differentiated into separate organs, known as ! 

 ro-ot, stem and leaf, by means of which it can assimilate raw food 

 materials from the air and soil. 



Functions of the root. The root is an organ of great impor- 

 tance in the assimilation of food. Large amounts of water re- 

 quired by the growing plant, are taken from the soil by means 

 of the root and it is through this means that the plant obtains 

 its nitrogen and ash constituents. 



