IMPORTANCE OF WATER TO PLANTS

We learned in a previous paragraph that plant roots take moisture from
the soil. What becomes of this moisture? We will answer this question
with an experiment.

=Experiment.=--Take a pot or tumbler in which a young plant is
growing, also a piece of pasteboard large enough to cover the top of
the pot or tumbler; cut a slit from the edge to the centre of the
board, then place it on top of the pot, letting the stem of the plant
enter the slit. Now close the slit with wax or tallow, making it
perfectly tight about the stem. If the plant is not too large invert a
tumbler over it (Fig. 21), letting the edge of the tumbler rest on the
pasteboard; if a tumbler is not large enough use a glass jar. Place in
a sunny window. Moisture will be seen collecting on the inner surface
of the glass. Where does this come from? It is absorbed from the soil
by the roots of the plant and is sent with its load of dissolved plant
food up through the stem to the leaves. There most of the moisture is
passed from the leaves to the air and some of it is condensed on the
side of the glass.

By experiments at the Cornell University Agricultural Experiment
Station, Ithaca, N.Y., it has been found that during the growth of a
sixty bushel crop of corn the plants pump from the soil by means of
their roots, and send into the air through their leaves over nine
hundred tons of water. A twenty-five bushel crop of wheat uses over
five hundred tons of water in the same way. This gives us some idea of
the importance of water to the plant and the necessity of knowing