68 PLANT GROWTH AND NUTRITION 



Method. — In some corn grains that have sprouted remove the 

 endosperm. Place them side by side in moist sawdust with some 

 normal sprouted grains. Give each lot of seedlings the same con- 

 ditions of water, light, and air. 



Observations. — Watch them carefully for a period of at least two 

 weeks. What differences do you observe in the rates of growth in 

 the two lots of seedlings ? 



Conclusion. — What is the use of the endosperm to the corn? 



Prohlern 46 : To find whether starch or grape sugar will dis- 

 solve in water. 



Materials. — Test tubes, starch, grape sugar. 



Method. — Shake up a little starch with water. Let it stand 

 for a few minutes. Shake up an equal amount of dry grape sugar 

 in water. Let it stand for the same length of time as the starch. 



Observations. — How do the two compare in appearance? 



NOTE. — A substance is said to be soluble when it dissolves or entirely disappears 

 from view in water or some other liquid. 



Conclusion. — Is starch or grape sugar soluble in water? 



Problem 47 : To find how the young plant makes use of the 

 food supply. Digestion. 



Method and Observations. — Wash some dry, unsprouted corn 

 grains and test them for grape sugar. Then cut some corn grains 

 that have just begun to germinate lengthwise through the embryo 

 and test for grape sugar. Look for changes in color between the 

 embryo and endosperm. 



NOTE. — Under certain conditions when starch is changed to grape sugar it is 

 said to have been digested. In the corn plant this is accomplished by a digestive 

 ferment, or enzyme, called diastase. 



What differences between the unsprouted and sprouted corn 

 do you find? 



Conclusion. — 1. What happens to the starch when corn 

 sprouts ? 



2. What causes this change? 



3. Of what use would this change in the form of the food supply 

 be to the young plant? 



