food and in return gives off oxygen that we breathe. Have you ever been
in a greenhouse where there are lots of plants and noticed how good the
air smells? It’s because of all the fresh oxygen the plants are producing
and filtering out the harmful gases that our bodies don’t need, like
carbon dioxide.
Next, we have the trunk. This is what gives the tree its strength. Figure
1 shows the different parts that make up the trunk.
Theouter barkis what protects the tree from damage; it’s basically the
tree’s armor. Theinner barkis where the sugar the leaves make is carried
to all other parts of the tree where it is changed into food.
Thecambiumis only one cell thick! This is where the tree trunk grows in
diameter. The interesting thing about these cells is that on one side they
produce bark and on the other side they produce wood.
Xylem or Sapwoodis the highway structure of the tree. All the nutrients
and water taken in by the roots are moved up through the sapwood and
is then fed into the branches and up into leaves.
Heartwoodis the backbone of the tree. This layer of wood is no longer
active. It’s made when the inner layers of the old sapwood stop carrying
the water and nutrients to the leaves. This wood is harder and much
stronger than the sapwood. Many times the heartwood is also a different
color than the sapwood, usually darker, but not always.
Finally, we get to the bottom of things. The roots of a tree anchor it in
the ground and also supply water and nutrients as stated earlier. Have
youeverwatchedatreebeingblownbackandforthinastrongwind?
How do trees keep from being blown over? The answer is in the root
structure. Trees have a root that goes deep into the earth called the
taproot. The taproot grows deep in search of water and nutrients in
times of drought. When there is plenty of rain, however; the surface
roots collect most of the water and nutrients and spread out far to further
anchor the tree.