CHEMISTRY OF PLANT GROWTH 239 



There is always a slight loss of nitrogen in the germina- 

 tion of seeds. 



336. Germination of Seeds and Digestion of Food 

 Compared. The chemical changes which take place in 

 the germination of seeds are similar to those which take 

 place in the digestion of food. In the germination pro- 

 cess, starch, fat, and proteids are changed by ferment 

 action to soluble forms. The diastase and peptonizing 

 ferments are among the most active in producing 

 the chemical changes in both the germination and diges- 

 tion processes. Seed germination is, in part, a digestion 

 process. 



337. The Necessary Conditions for Germination 



are: (i) Moisture, (2) heat, and (3) oxygen. The 

 same conditions which produce decay are necessary for 

 germination. The temperature required for germination 

 ranges between comparatively narrow limits : 



Wheat 35 F. to 104 F. 



Barley 38 F. to 104 F. 



Peas 44.5 F. to 102 F. 



Corn 48 F. to 1 15 F. 



The necessity of oxygen for germination is shown by 

 the following experiment : When seeds are put into 

 water those that float are generally the only ones that 

 germinate. A few of those that sink may germinate, 

 getting their oxygen from that dissolved in water. If a 

 current of air is passed through the water all of the seeds 

 will germinate. Oxygen is necessary during germination 

 in order to oxidize some of the reserve material and pro- 

 duce heat. Seeds, in germinating, always lose weight. 



