CHEMISTRY OF PLANT GROWTH 237 



of seeds are stored up mainly in the germ or portion adja- 

 cent to the embryo. The amount of nitrogenous mate- 

 rial in seeds is, like the ash, quite constant in form and 

 amount. 



332. Chemical Changes during Germination. All 

 of the food materials in seeds undergo chemical 

 changes during the process of germination. The chief 

 agents in bringing about these changes are the various 

 kinds of soluble ferments which are always present in 

 seeds. The more important changes can be summarized 

 as follows : Cellulose is changed to soluble carbohydrates; 

 starch is changed to soluble forms and then into dextrose 

 bodies ; fat is changed to starch ; insoluble proteids are 

 changed to proteoses and a small amount to amides. 

 Organic acids are produced from both nitrogenous and 

 non-nitrogenous compounds during germination. 



333. Change of Starch to Soluble Forms. When 

 seeds germinate, the starch is changed to soluble forms 

 before it is utilized by the plantlet. During conversion 

 of starch into soluble forms, the diastase ferment be- 

 comes active, rendering the granulose soluble, and finally 

 leaving nothing but a pitted cellulose skeleton which is 

 also rendered soluble. The change of starch into soluble 

 forms and dextrose bodies is brought about by the action 

 of ferments, particularly diastase which is found in all 

 seeds. During the process of germination, some of the 

 starch is oxidized, and heat is produced. Not only 

 starch, but other carbohydrates, as pentose and cellulose, 

 likewise undergo similar change during germination. 



Experiment 66. Reaction of germinating seeds. Fill a cylin- 



