Forestry Science I
Unit 3
Lesson 1
Created by Ms. Holli Bowman
FORS 7730
Fall 2001
Modified by Georgia Agricultural Education Curriculum Office
July 2002.
And CTAE Resource Network, 2010
Introduction
• Trees rank only
second to grass in
their distribution on
the earth.
• Forest land owners
need to be familiar
with the trees on
their land.
What is a tree?
• A tree is a woody plant
having one welldefined stem and a
formed crown and
usually attaining a
height of at least 8
feet.
• It has three main
parts: roots, stem and
crown.
Functions of the roots
• Serve to anchor the tree against wind and
other forces of nature
• Rootlets are smaller roots that come from
the largest roots
• Root hairs are fine, hair-like roots which
extract nutrients and water from the soil
that are necessary for the tree’s growth
Functions of the stem
• Also known as the trunk
• Transports food, water and minerals up and
down the plant
• Produces the bulk of the useful wood in a
tree
Functions of the stem
• Heartwood -- the darker-colored wood of the
center portion of large trees. This wood is dead.
This core serves only to give the tree strength and
keep it upright.
• Xylem -- located outside the heartwood, this is a
lighter-colored wood also know as sapwood. It is
the living portion of the tree. It is the means by
which raw nutrients and water are carried from
the roots to the crown as well as a storage area of
food synthesized in the leaves.
Functions of the stem
• Cambium -- located outside the sapwood and inside the
bark. This layer of active cells is responsible for the
growth of the tree and forming a new annual ring each
year.
• Phloem -- located outside the cambium layer. This layer
of living cells is also called the inner bark. It carries food
made in the leaves down to the branches, trunk and
roots. It is protected by the dead, non-functioning outer
bark.
• Cork cambium -- the thin layer of cells between the
phloem and the bark itself which forms the outer bark.
Functions of the crown
• Serves as the “manufacturing plant” of the
tree by making food for the rest of the tree
• Is composed of branches, twigs and leaves
• Part of the tree where photosynthesis occurs
Functions of the crown
• Leaves -- part of the tree which contains green
chloroplasts
• Photosynthesis -- process in which leaves turn
sunlight, carbon dioxide and water into
carbohydrates (starches and sugars). Oxygen is a
by-product of photosynthesis.
• Transpiration -- process by which water brought to
the crown of the tree moves as water vapor into the
atmosphere.
Functions of the crown
• Stomata -- pores of the leaves through which
transpiration occurs.
• Respiration -- process in which a tree
consumes oxygen and some food to obtain
energy for growth and other biological
processes. The tree gives off carbon dioxide
and water as end products.