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|| EXAMINING WOODY STEMS
Let's look very carefully at this willow (or horse chestnut)
stem. It is like wood, because it's part of a tree. It's
not at all the same as a flower stem.
There are roots at the bottom (base) of the stem, just like
plants have, and the woody stems almost always grow upward.
Plants grow toward light. Most trees are outside, and the
sun is their light. Trees grow toward the sun, and spread
their arms (limbs) as though to welcome the sunlight.
Do you see the little swollen places on the stem? They are
called "nodes," and they are the places where leaves will
grow. On trees that blossom, the nodes are the places where
flowers will bloom, and then leaves will come out from the
nodes also. On trees that bear fruit, like peach trees, the
fruit will grow where the flowers are. Nodes have a lot of
jobs to do! In the fall, when the leaves drop off, there
will be little marks on the stems where the leaves were.
Those marks are called "leaf scars." Above each leaf (if it
is on the stem) or leaf scar (if the leaf has fallen), there
is another tiny swollen place. That is called a "lateral
bud." The buds have tiny "scales," which are like lids, and
they remain there after the leaves are gone. The bud scales
show us where new growth began on the stems. There is
another bud on the very end of the stem. It is called the
"terminal bud" (the word "terminal" means "end").
The spaces between the nodes, where there aren't going to be
leaves, are called "internodes," and they are not all the
same. Part of what makes plants interesting is that their
leaves and flowers (and fruits) are uneven. On the
internodes of some stems, like birch, horse chestnut, and
cherry, you can see pores along the internodes. These pores
are called "lenticels" (pronounced "len-ti-cells"). The
lenticels help the tree to take in water and air.
If you put the base of a willow stem into some potting soil
and keep it watered, it will grow roots and the nodes will
develop leaves. Then, stems will grow out from where the
leaves were, and you'll have another willow tree!
Make a list of all the parts of the stem, and then look at
other kinds of stems to see if they have the same parts.
Some kinds of plants have different looking parts, but they
do the same things.
The nodes on a mint stem, for example, are fat places that go
all the way around the stem--they aren't swollen only on one
side of the stem. Several leaves, going in all directions,
will grow out from the nodes of a mint stem. Mint stems are
interesting for another reason: they are sort of square.
Isn't that a surprise?
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