A description of the parts of the cross section of a tree.

1. THE
CROSS -SECTION
OF A TREE
Prepared By: S. Bryan

2. Lesson Objective
At the end of this lesson, the students will
be able to:
Identify the different parts and
functions of the cross – section of a
tree.

3. Lets Review!
What is a tree?

5. Lets Review!
How many types of wood are there?
1. Hardwoods: beech, balsa, mahogany,
teak
2. Softwoods: cedar, douglas fur, pine,
redwood, spruce

6. The Cross – Section of A Tree
A cut through of something at an angle
perpendicular to its axis in order to view
its interior structure.
A sample showing all characteristic
parts of the tree.

7. The Cross – Section of A Tree

8. The Cross – Section of A Tree
Pith
1. the innermost part of the tree.
2.a residual small central core of primary tissue
generated in an initial growing point before
any secondary growth.

9. The Cross – Section of A Tree
Medullary rays

10. The Cross – Section of A Tree
Heartwood
1. Most of the trunk in an old tree is dead wood
called heartwood. The heartwood is old xylem
or sapwood that no longer transports water and
minerals up the tree.
2.Heartwood can be darker, lighter, or the same
color as sapwood.

11. The Cross – Section of A Tree
Annual (Growth) Rings
1. records the tree’s age. Every year a
tree grows a little more and a new tree
ring is made.
2. These are located in both the
heartwood and the sapwood.

12. The Cross – Section of A Tree
Cambium layer
The cambium is a very thin layer of growing tissue that
produces new cells that become either xylem, phloem or
more cambium. Every growing season, a tree’s cambium
adds a new layer of xylem to its trunk, producing a visible
growth ring in most trees. The cambium is what makes the
trunk, branches and roots grow larger in diameter.

13. The Cross – Section of A Tree
Sapwood (Xylem)
The layer next to the cambium is called the
sapwood or xylem. Each year the cambium adds
new layers of woody tissue; the sapwood is made
up of the youngest layers of wood. The sapwood
is a network of thick-walled cells that forms a
pipeline, carrying water and minerals up the tree
from the roots to the leaves and other parts of the
tree. The sapwood also stores nutrients and
transports them across the tree, from one part to
another.

14. The Cross – Section of A Tree
Phloem
The layer next to the outer bark is called the inner bark or
phloem (FLOW-um). The phloem acts as a food supply line
from the leaves to the rest of the tree. Sap (water containing
dissolved sugars and nutrients) travels down from the leaves
through channels in the phloem to the branches, trunk and
roots, supplying all the living parts of the tree with food. If you
were to cut a band around the trunk through the bark and
phloem, the tree would probably die. That's because the
phloem would be severed and food could no longer flow to
the lower trunk and roots.

15. The Cross – Section of A Tree
Bark
1. The outermost layer of the tree.
2. Its texture, thickness, and flexibility depend on the type of
tree. Although bark looks different from tree to tree, it
serves the same purpose—to protect the tree from injury
and disease. Some trees have very thick bark that helps
prevent damage from fires. Others have bad-tasting
chemicals in their bark that discourage hungry insects. And
some bark is covered with spines or thorns that keep
browsing mammals away.

16. Lets Review!
Name at least one thing you
learned today.

17. The Cross – Section of A Tree
Assignment 2:
Explain the process by which
plants make food.