GERMINATION THE SEED WAKES UP 45 



The Necessity of Stored Foods. The necessity of this stored 

 food can be shown by taking a number of well-started seedlings, 

 removing part of the stored food (in cotyledon or endosperm) in 

 some of them, removing it all in others, and leaving still others 

 unharmed. If these seedlings are then placed so that the root can 

 dip into water, by suspending them on a netting over a well-filled 

 glass, their development can be watched. 



Several seedlings must be used in each group, lest we draw 

 conclusions from too few instances, or perhaps be misled in case 

 some one seed were abnormal. The conditions of growth must 

 be the same in each case, lest it appear that these varying condi- 

 tions, and not the loss of stored food, produces the results. 



After a few days it will be seen that the whole seeds grow well 

 and rapidly; that those with part of their food removed start 

 more slowly and soon cease growing; while those with all the stored 

 food removed scarcely start at all. This is because of the fact 

 that, until the seedling can develop roots and leaves, it depends 

 solely on this store of food whose removal is shown to have so 

 serious results. 



The Digestion of Stored Foods in Seeds. To prove that these 

 food stuffs must be digested before they can be used in germinating 

 plants, corn seeds can be tested for starch and for grape sugar, 

 both before and after germination has started. 



Starch is insoluble in cold water, and does not pass readily 

 through the absorbing membranes. Therefore it has to be digested 

 (changed to soluble sugars) before the plant can use it. 



This digestive change is accomplished by a substance in the 

 seed, called diastase, which acts somewhat like the digestive 

 fluids in our bodies. 



If the corn be tested before germination has begun, much starch 

 and little or no sugar will be found. If it be tested in the same ways, 

 after germination has proceeded for a few days, the reverse will 

 be discovered, as most of the stored starch will have been converted 

 into soluble form, sugar, by the diastase in the cotyledon. 



Conditions for Germination. That sufficient heat, air, and 

 moisture are essential conditions for germination, can be proved 



