Chapter
Three
Energy For
Tree Growth
PLANTS
SUPPLIES NEEDED
Gather enough
materials for each
team of 4-5 students:
5 Small grass jar or
tumbler
5 Plastic kitchen
wrap
5 Leaf-bearing twig
5 Solid shortening or
Vaseline
5 Gallon-size jar
5 20-24 inches tree
seedling
5 Plant container
5 Cardboard paper
towel tube
5 Flexible soda
straws
5 Black paint
EDUCATION
BENCHMARKS
• Diagram and
explain a cycle.
• Describe the basic
needs of living
things.
• Ask questions and
make predictions
that are based on
observations and
can be explored
Page 3-11
through simple
investigations.
ACTIVITY OVERVIEW
ACTIVITY
SUMMARY
Students explore
how trees get
energy through two
experiments.
PREPARATION
Plan ahead
5
5
Both experiments
should be
conducted during
growing season.
Collect 2 feet
seedlings and
leaf-bearing twigs
for each team.
LOCATION
Outside
TIME NEEDED
20-30 minutes to set up
experiment and 4-5
weeks to collect data.
OBJECTIVES
Students learn:
•
•
•
How trees derive energy through
transpiration and sunlight.
How to collect data to support theories.
How to compare two different
experiments and draw conclusions from
the comparisons.
This material is
derived from the
4-H Forestry Leader
Guide, Unit A, p. 11,
an OSU Extension
4-H Youth Program
publication.
ENERG Y FOR TREE GR OWTH
OSU EXTENSION 4-H YOUTH
BACKGROUND
All activity requires
energy. We use energy in
doing any kind of physical
work or play. We require
energy to grow. A tree
also requires energy to
grow. People get their
energy by eating foods
produced from plants or
animals. But where do
trees get their energy?
Trees have to have food
but each tree
manufactures its own.
Water, containing mineral
nutrients, is absorbed by
the root hairs. Xylem cells
in the sapwood carry it up
to the leaves.
Air containing carbon
dioxide is taken in by the
leaves through openings
called stomata. In a
process called
photosynthesis, energy
from the sunlight enables
the tree to manufacture in
the leaves its needed
foods from the minerals
and the carbon dioxide.
The phloem cells of the
inner bark transport the
food from the leaves to the
branches, trunks and roots
of the tree. A girdled tree
usually dies because the
translocation of foods and
food materials, particularly
to the root system, has
either stopped or has been
seriously curtailed. To aid in
recall, suggest the tree has
a “bus system” - it’s xylemUP” and phloem-DOWN” in
transporting water up and
food down.
Plant and Animal
Comparisons—
Trees and other green
plants whose leaves
contain chlorophyll absorb
air, make the most use of
the carbon dioxide and
expel oxygen. Animals
inhaling air make greatest
use of the oxygen, and
exhale carbon dioxide. The
two forms of life help each
other in this respect. It has
been estimated that one
acre or nearly one-half
hectare covered with
healthy, rapidly growing
trees will produce enough
oxygen for 18 people.
Older mature or over
mature stands produce
little excess oxygen since
they are slower growing
and decaying branches
and trees recycle the
oxygen as it becomes
available. Both plants and
animals use water in their
life supporting processes.
Animals eliminate their
waste or excess water
through urination,
respiration and perspiration.
Plants give off excess
moisture through their
leaves. This is called
transpiration.
ENERG Y FOR TREE GR OWTH
Page 3-12
OSU EXTENSION 4-H YOUTH
METHODS (continued)
Transpiration
Experiment
1. A demonstration of
how trees give off
(transpire) moisture
can be carried out as
follows: During the
growing season, fill a
glass tumbler or a
small jar about twothirds full with water.
2. Cover the top with a
plastic kitchen wrap to
make it air tight.
3. Cut a leaf-bearing
twig from a tree and
carefully insert the
base of the twig
through the plastic.
4. Use solid shortening,
Vaseline or other
suitable substance to
make it airtight where
the twig goes through
the plastic.
5. Cover the twig and its
receptacle with an
inverted gallon-size
glass jar or with a
transparent plastic
bag.
6. To keep scientific,
have another set-up
that is identical in
every way except
that one does not
put in a twig.
7. Students observe
what happens
inside the two
covers. If moisture
collects inside the
cover with the twig
and the inside of the
other cover stays
dry, the reasonable
explanation for the
moisture is that it
passed up through
the stem and out
through the leaves of
the twig.
Do the leaves of the plant transpire?
ENERG Y FOR TREE GR OWTH
Page 3-13
OSU EXTENSION 4-H YOUTH
METHODS (continued)
Sunlight Experiment
1.
2.
3.
4.
but they should be
arranged so that little or
no light is admitted to the
Another procedure is to
box. Soda straws with
demonstrate the
elbows can be used.
necessity for trees to have
Paint the straws black.
sunlight. Take up a
Insert one end through a
seedling that is 20 to 24
tight fitting hole and bend
inches or 50 to 60
the elbow joint. Several
centimeters tall before
of these will permit
growth starts in the spring.
aeration without
In can be either
admitting light.
coniferous or a broadleaf
5. Keep the seedling in
seedling
good light, but where it
Plant it in a container.
does not get too hot. This
Enclose one of its main
is to prevent the enclosed
branches in a cardboard
branch from being
tube or oblong box so
damaged by
that light is shut off from it.
overheating.
Small holes will be
6.
Keep the branch
necessary for aeration,
enclosed until the new
leaves on the other
branches have been out
for four to five weeks.
Then, remove the
covering from the branch
and compare the branch
that has had no sunlight
with the other branches.
If the covering was
sufficiently aerated, then
differences between the
covered branch and
other branches should be
due to lack of light. Light
was the only factor the
other branches had that
the covered branch did
not have.
ENERG Y FOR TREE GR OWTH
Page 3-14
OSU EXTENSION 4-H YOUTH