CHAPTER FIVE 
THE FOOD OF PLANTS 
There’s magic done in plants. 
O’er simple elements of earth and air, 
A sun-beam wand is passed — 
And food is there! 
NEvIN WooDsIDE 
WE live and grow on the food we eat, but a corn 
plant lives and grows without eating. It sends its roots 
out into the soil, spreads its leaves to the light and air, 
and week by week increases in size. Finally the ear ap- 
pears with the kernels swollen with a rich store of food. 
The plant has lived, reached its full size, and at the end 
of life has a surplus of food on hand. 
In our garden and field crops we find sugar, starch, oils, 
and the other foods that we live on, and these are not in 
the soil or air. Where do plants get them? What do 
plants use for food? Only in comparatively recent years 
have scientists been able to answer these questions. 
The food of plants. In your study of physiology 
you learn that man and the lower animals use for food 
proteins, fats, and starch and sugar. Plants use these 
same foods The difference between the nourishment 
of a green plant and the nourishment of an animal is 
that the green plant makes its own foods from water, carbon 
dioxid, and minerals, while an animal cannot do this 
but must have its food already prepared for it. 
1 Sometimes carbon dioxid, water, and the various minerals used by 
a plant are called ‘“‘plant foods.” Sometimes these are called the ‘‘raw 
materials used in the making of food,” or simply “‘food materials,”’ and 
the term “food” is used to mean the sugars, starches, fats, and proteins 
that are built up from these substances. In this text the word is used 
(as it is in animal physiology) to mean the complex, built-up substances 
actually used in the nourishment and growth of the living matter of the 
cells. ‘ 
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