Cnapter 6 



PLANT MANUFACTURE OP POOD 



One of the most remarkable characteristics of living things is 

 their ability to produce constant sources of energy within them- 

 selves, and to create matter with the resultant tremendous 

 increase in bulk. A tiny seed, weighing an ounce or two, takes 

 root in the soil and in time becomes a forest giant with tons of 

 foliage on its branches and more tons of wood in its trunk. 

 Where does all this come from, in a place where there was no 

 visible matter before? At the same time, living involves work and 

 therefore requires energy, even among plants. This is dramati- 

 cally displayed by the seedling which germinates in a crevice of 

 a boulder, eventually growing to such size that it splits the rock 

 in two. From where does this energy come? 



The answer to both questions is the same: the energy and the 

 substance originates in food. Foods can be defined as those 

 chemical compounds which can be used by living things for 

 energy, or out of which protoplasm can be constructed through 

 growth. Thus one of the most fundamental relations of organisms 

 to their environment is the securing of this all-important food. 



Glucose: the Basic Food 



Foods belong in three chemical categories: carbohydrates, 

 fats and proteins. All three are compounds of carbon and 

 hydrogen and oxygen; and all are distributed throughout the 

 bodies of plants and animals, but in varying amounts and suited 

 to various purposes. Carbohydrates and fats are commonly the 

 chief sources of energy, while proteins are especially useful in 

 the creation of new protoplasm through growth. Fats and pro- 

 teins are secondary foods, being derived from the simpler 

 carbohydrates; fats can be elaborated by either plants or animals, 

 but only plants can change carbohydrates into proteins. Thus 



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