Fall Slumbers Background Information

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

Background Information:

• Chlorophyll. 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!
• Water.  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.
• Sunlight.  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.
• Temperature.  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.
• Adaptation.  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.
• Misconception(s).  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 the winter.