Trees can be broken down into three main parts: the roots, the
leaves and the woody structure between them. The roots' function
is to bring raw materials-water and mineral salt dissolved in
water-to the tree. The leaves absorb carbon dioxide from the air
and use the sun's light energy to combine this gas with the
moisture from the roots, thus making the simple sugars that are
the basic nutrients of the tree.
The trunk, limbs, branches and twigs hold the leaves in position
to receive the life-giving sunlight and air; they also act as
transportation, carrying raw materials between roots and leaves.
The materials absorbed by the roots are pulled up by capillary
attraction and the osmotic action induced by evaporation of
water from the leaves. Loss of water through the leaves is
called transpiration.
On a summer day, a single birch tree may transpire 700 to 900
gallons of water. It is this enormous flow of water that causes
a continuous flow of sap from the roots to the topmost twigs.
In planting or transplanting a tree, and in building on a lot
where you wish to preserve the trees, the gardener's chief
consideration must be to protect the root structure of the tree.
The big roots near the stem anchor the tree to the ground, while
the fine root hairs at the ends of the rootlets absorb the water
from the soil.
The stem or trunk of a tree has three parts: the bark, the wood
and the pith. The pith is the central part and around it is the
wood. Between wood and bark is the cambium, a thin layer that
produces new wood and bark. When the cambium ring is severed, as
by a wire cable, the tree is killed, and since the cambium
protects against insects and disease, anything driven into it
can wound the tree severely.
Outside of man himself, trees have countless enemies.
There are 200,000 known kinds of insects that attack trees, in
addition to diseases such as blight, rust and rot, storms and
droughts. Luckily, birds help to keep caterpillars, borers,
beetles and other insects in check.
About Author :
Paul Curran is CEO of Cuzcom Internet Publishing Group and
webmaster at Trees-and-Bushes.com, providing access to their
nursery supplier for a range of quality plants, trees, bushes,
shrubs, seeds and garden products.Visit their trees section
to find a great selection of trees for your garden
