The warm colors of autumn leaves get us ready for winter’s chill. Pull up a blanket and see how.
Today, we officially say good-bye to summer and hello to autumn. This year’s equinox begins at 3:44 p.m. From here on, the days will gradually get shorter and temperatures will slowly drop.
This is a pleasant time of year. Summer’s blistering heat quickly fades from memory. Days are sunny, and the crisp air gives a hint of what’s to come. We dress in cozy sweaters and warm hats and gloves and pull up an extra blanket at night. It is during this time that Mother Nature puts on quite a display of color, turning the leaves to shades of yellow, red, gold and orange before they fall to the ground.
Just how do the leaves change color? Chemical changes are taking place
in the leaves throughout the spring and summer. During these seasons, leaves act as factories that manufacture food for the trees. The leaves get their green color from chlorophyll. They also contain yellow or orange carotenoids – which, by the way, are also responsible for the carrots’ orange color. All of these colors exist in the leaf.
But during the spring and summer, since the leaf is in full food- production mode, the chlorophyll is dominant.
As fall sets in, the dwindling daylight and cooler temperatures cause the chlorophyll to break down. It’s here that the other colors appear, making fall the most colorful time of year.
The brightest leaf colors will appear when the days are sunny and somewhat warm, with cool nights below 45 degrees. Sugar is made in the leaves during the day and trapped there at night. The captured sugar helps form the red pigment called anthocyanin.
You might think that all trees show the same colors during the fall – not true. Different species produce specific colors.
For example, birch and hickory trees show only yellow. Most oaks will show only brown, while the leaves of the beech tree turn golden bronze.
Ginko trees produce bright golden, fan-shaped yellow leaves – the female trees also make foul-smelling fruit.
Some leaves just turn brown and die without ever showing bright colors.
Colors on the tree in your back yard may change a bit from year to year. Leaves that spend most of the time
in direct sunlight will produce more red, while the ones getting less sun will show more yellow.
This, of course, depends on the mixing of chlorophyll with the other pigments contained in the leaves.
Other things affect how much bright color we see in the fall. Too much rain will cause the leaves to produce drab colors, while drought will make the leaves show red.
A warm, dry summer and early rain in autumn will stop the leaves from falling too fast, giving their colors a chance to show.
The leaves finally fall when a special layer of cells develops and destroys the tissue that attaches them to the tree. The place where the leaf grew is marked by a scar.
But nothing ever goes
to waste in nature. The dead fallen leaves create a blanket on the forest floor and contain large amounts of calcium and potassium that were used to nourish the tree that they came from. As they decompose, they give these minerals back to the earth.
Today’s lesson fulfills the following New York standards: English Language Arts Standards: E1c, E3d. Science Standards: S1a, S4a, S6b.
New York Post Activities
Decorate your classroom for fall. Bring in brightly colored leaves. Examine them and see how many colors you can find in each.
Check the weather page in today’s Post and make a note of
it. Track the weather for the next week and try to predict if the leaves in your area will be bright
or dull. Use the weather map in the paper to predict the leaf color for other parts of the country.
Check The Post
for ads that feature things needed for fall. With a classmate, create your own checklist of things you need to be ready for the chilly temperatures ahead.
Teachers: For more information about the New YorkPost’s Classroom Extra program, contact Customer Service at 1-800-552-7678. Today’s lesson can be found in Classroom Extra at nypost.com.