EXERCISE 29 



HOW MAY INSOLUBLE FOODS, AS STARCH, BE MOVED 

 FROM PLACE TO PLACE IN THE PLANT? 



Materials. Corn grains which have been soaked twenty-four hours ; 

 corn grains which have germinated and grown sprouts an inch long ; 

 young corn plants several inches high with the seed grain attached ; 

 Fehling's solution ; iodine solution. 



Directions for work. Crush the soaked grain and boil it in 

 water in a test tube. Pour part of the resulting solution into 

 another tube and add iodine. Is there much starch present? 

 To the remaining liquid add Fehling's solution and bring to 

 boiling. If glucose (a form of sugar) is present, a copper-red 

 or orange color appears and the material which produces the 

 color settles to the bottom later as a precipitate. The amount 

 of sugar may be judged by the amount of precipitate if suf- 

 ficient Fehling's solution has been added to act on all the sugar. 

 A slight blue color in the solution after the precipitate has 

 settled indicates that a slight excess of Fehling's solution has 

 been used. 



Repeat both tests with germinated grains and with the grains 

 which have been separated from young corn plants. 



Note the facts discovered in each test. What evidence do 

 you have regarding the gradual disappearance of the starch ? 

 What evidence of the presence of sugar when starch is disap- 

 pearing ? If starch can be changed into sugar, would the trans- 

 portation of this sort of food material be explainable? How? 



The experiment may be repeated with other common seeds. 



References 



BERGEN and CALDWELL. Practical Botany, pp. 78-81. 

 BERGEN and CALDWELL. Introduction to Botany, pp. 40-43. 



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