CHAPTER XV 



OCCURRENCE AND USES OF IMPOR- 

 TANT CONSTITUENTS IN AGRICUL- 

 TURAL PLANTS 



Having now considered the physiological processes by which 

 plants utilize the energy of the sun in synthesizing their own 

 food material which is used both to yield energy and to construct 

 the body substance, let us now examine different plants as to 

 the particular compounds which they contain and the general 

 uses to which the plants are adapted. We shall study the 

 different constituents according to their occurrence in plants 

 which have agricultural importance as crops and the uses to 

 which each crop is thus adapted. Generally speaking, plants 

 have two main uses economically: (i) as animal food, (2) as 

 the basis of important manufactured products. The study in 

 detail of their food value to man and animals will be taken 

 up in the next chapter. In this chapter we shall consider the 

 general distribution and uses of the plant constituents. 



CARBOHYDRATES 



The carbohydrates are the most widely and most abundantly 

 distributed of the three groups of organic constituents. There 

 is no green plant in which they are not present and in most 

 cases they are the predominating constituent. The different 

 members of this group that are found in plants may be con- 

 sidered in the following order : Polysaccharoses not sugars — 

 cellulose, starch, dextrin, inulin; anhydrides of pentose sugars 

 — pentosans; disaccharose sugars — cane sugar, malt sugar; 

 hexose monosaccharose sugars — glucose and fructose. 



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