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

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 well-defined 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.