CHAPTER VIII
THE ROOT.—FUNCTION AND STRUCTURE
The function of roots is twofold,—to provide support or anchorage for the plant, and to collect and convey food materials.
The first function is considered in Chapter VII;
we may now give attention in more detail to the second.
The feeding surface of the roots is near their ends. As the roots become old and hard, they serve only as channels through which food passes and as hold-fasts or supports for the plant. The root-hold of a plant is very strong. Slowly pull upwards on some plant, and note how firmly it is anchored in the soil.
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Fig. 40.—Wheat growing under Different Soil Treatments. Soil deficient in nitrogen; commercial nitrogen applied to pot 3 (on right).
Roots have power to choose their food; that is, they do not absorb all substances with which they come in contact. They do not take up great quantities of useless or harmful materials, even though these materials may be abundant in the soil; but they may take up a greater quantity of some of the plant-foods than the plant can use to advantage. Plants respond very quickly to liberal feeding,—that is, to the application of plant-food to the soil (Fig 40). The poorer the soil, the more marked are the results, as a rule, of the application
