There is a constant movement of the indispensable plant nutrients
after they have entered the root-hairs, through the stems and into
the leaves. This constant movement of the plant-foods depends upon
the fact that the plant consumes in its growth considerable
quantities of these substances, and as the plant juices are
diminished in their content of particular plant-foods, more enters
from the soil solution. The necessary plant-foods do not alone enter
the plant but whatever may be in solution in the soil-water enters
the plant in variable quantities. Nevertheless, since the plant uses
only a few definite substances and leaves the unnecessary ones in
solution, there is soon a cessation of the inward movement of the
unimportant constituents of the soil solution. This process is often
spoken of as selective absorption; that is, the plant, because of
its vital activity, appears to have the power of selecting from the
soil certain substances and rejecting others.
Movement of water through plant
The soil-water, holding in solution a great variety of plant
nutrients, passes from the root-hairs into the adjoining cells and
gradually moves from cell to cell throughout the whole plant.
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