Students observe changes in a selected tree
leaf near their homes during the fall. Twice each week students record changes
in the leaf using words, pictures, and numbers. Observations continue for
a period of three or more weeks. Activities in the classroom will emphasize
tree adaptation for winter survival.
The Family Page extends this learning to the community by inviting parents
to facilitate home observations and discussion related to seasonal plant adaptations.
inquiry will require a minimal classroom time commitment and will therefore
be implemented in the midst of other classroom science activities.
Topics: adaptations, plants, cycles
Ohio Academic Standards Alignment: Click here to view content standards alignment to Science for Ohio by grade level.
Classroom Time Required:
15 minutes to introduce, 15 minutes each week to check observations, 90
minutes for closure activities
Chlorophyll absorbs sunlight using the sun's energy to make food for the plant.
In preparation for freezing weather, nutrients move slowly out of the leaves
and into the tree's branches, trunk and roots where they are safely stored
against the cold. When spring comes, the tree will draw on these nutrients
to grow new leaves. When the nutrients depart, however, the leaves stop making
chlorophyll, and the chlorophyll remaining in the leaves gradually disintegrates,
allowing other pigments to come out of hiding and hence turning the leaves
a different color!
Deciduous trees (those with broad, flat leaves) lose their leaves to save
water. Trees, as well as all other plants, take in moisture through their
roots and lose moisture through their leaves (transpiration). During
the warmer months this keeps leaves moist and healthy so they can produce
sap (food) for the tree using the sun's energy. During the winter months,
moisture in the soil is often frozen and therefore unavailable for use by
plants. Losing leaves in the fall insures that the tree will be able to save
enough water to get through the winter.
Trees, as well as other plants, use the energy of the sun to make a kind of
sugar in their leaves that is the tree's food. This process is called
photosynthesis. Starting with the first day of summer, daylight hours
begin to grow shorter. Daylight hours will continue to shorten until the first
day of winter. Fewer hours of daylight means fewer hours for plants
to make food.
As fall approaches, weather conditions begin to fluctuate. While
the needle-like leaves of coniferous trees can withstand the changes in temperature
that come with the winter season, most deciduous trees cannot.
During the late spring and summer months, deciduous trees make all of the
food they will need for the entire year. Changes in sunlight and temperature
in the late summer and fall lessen a tree's ability to make food. Trees
adapt to these seasonal changes by shedding their leaves. While this
prevents a tree from continuing to make food for growth, it also greatly reduces
the amount of water lost through transpiration. Trees, in effect,
go through a period of hibernation in the late fall and winter by transferring
the sap made during the warmer months down into the roots of the tree and
using it sparingly during the winter months.
Myth: When the leaves fall off of a tree, the tree dies. Fact: A deciduous
tree loses its leaves in order to save water and energy during the winter
when groundwater is often frozen and sunlight hours are at an annual low.
- Caution(s). Students
should choose a tree leaf that can be observed while standing on the ground.
The use of chairs or ladders to observe leaves is not recommended.
- Expected Results.
Deciduous trees in Ohio will lose most of their leaves between
the middle of October and the middle of November, with the exception of oak
trees which will often keep their leaves after color change through most of