Real-Life Communication
Cabinets can be made from all sorts of materials, but one of the
most popular is wood. Trees such as oak, mahogany, alder and pine are popular
choices for making cabinets.
You are an apprentice cabinetmaker. You
wonder why wood is one of the better construction materials. Your boss tells
you to start by learning about the tree itself. "I'll bet you didn't know
that a tree is more dead than alive," he says.
You are puzzled. How
can this be? Read the following excerpt to learn more about tree biology.
Tree
biology
Peel away the layers of a tree to see its components.
First you will see the outer bark, composed of dead cells, which protects
the tree from all types of injuries and from burrowing insects. It also insulates
the tree against extreme cold and hot temperatures.
The inner bark,
called phloem, is like a pipeline that carries food produced in the leaves
down to the trunk and to the roots. Interestingly, the phloem only lives for
a short time, and then dies to become a part of the outer bark.
Inside
the inner bark is the cambium cell layer, which is the only growing part of
the trunk. Each year, the cambium produces new inner bark on the outside,
and on the inside produces new sapwood. Sapwood carries water and minerals
from the roots up the tree. As new outside layers of sapwood are added, the
inside layers die. The dead inside layers are called the heartwood. The heartwood,
even though it is dead, gives the tree its strength.
You
jotted down some questions as you read the article. Can you answer them?
- What is the function of the outer bark?
- What happens to the phloem after it dies?
- What layer gives the tree its strength?