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Why Leaves Change Color
October 20, 2014
I am overwhelmed by all of your thoughts and prayers this past week.
Thank you so very much, your prayers have helped.
We did manage a short afternoon of ArtPrize.
Only scratching the surface, we didn't catch a glimpse of the Grand Prize winner, but we did see some fantastic and different kinds of art.
(Pictured is living art, Plants as a background and other plants spelling 'Breathe O2'.)
At the bottom of this letter is paper artwork by a Japanese artist, her work is very impressive.
Shown is 'Eagle in flight'.
More important, was some needed down time, and time with my best friend (Karen).
Fall migration continues.
Canada Geese have been busy practicing the past few weeks.
Juveniles must learn to strengthen their wings for and families are now in small flocks as they practice and learn to fly in formation (bird school).
Every fall I seem to witness a few near collisions (in flight).
The robins are slowly making their way back from the woods.
Not all the time, but enough to feed on worms and such.
Bird songs are replaced by the music of wind chimes.
Smells of autumn permeate the outdoor air.
Earthy smells and the smell of fallen leaves.
Birds aren't the only living things that rely on length of day.
Trees and shrubs do too.
I write on this every couple of years.
Longtime readers, it may be a refresher course.
For newer readers, this may be a first time and you might even say to yourself "I didn't know that".
Tree foliage is a science, and there is no real shortcut to explain this.
I will add this, however.
Nothing just happens.
It was all created by the First and Greatest Scientist of them all.
Leaves changing is a science, it doesn't just happen.
It was there all along, and our Creator allows us to discover when the time is right.
That said, down to the topic at hand.
It starts as a whisper.
One leaf, one branch at a time.
If you are fortunate, you live in one of those parts of the world where Nature has one last fling before settling down into winter's sleep.
In these places, as days shorten and temperatures become crisp, the quiet green palette of summer foliage is transformed into the vivid autumn palette of reds, oranges,
A crescendo of color takes place.
On special years (like this one), the colors are truly breathtaking.
Why Do Leaves Change?
Animals aren't the only things to store up food for the winter.
Deciduous trees and shrubs must also.
Leaves are nature's food factories.
Plants take water and oxygen from the ground through their roots.
They take a gas called carbon dioxide from the air.
Plants then use sunlight to turn water and carbon dioxide into glucose.
Plants use glucose ( a kind of sugar) as food for energy and as a building block for growing.
The way plants turn water and carbon dioxide into sugar is called "Photosynthesis."
That "word" we all learned about at one time or another.
It means "putting together with light."
A chemical called chlorophyll helps make "Photosynthesis" happen.
You know that Chlorophyll is what gives plants their green color.
Where do the Autumn Colors Come From?
A color palette needs pigments, and there are three types that are involved in Autumn color.
The quiet green of summer foliage is transformed into the vivid autumn reds, oranges, yellows, golds, and browns before the leaves fall off the trees.
On years like this one, the colors are truly breathtaking.
It is necessary for photosynthesis, the chemical reaction that enables plants to use sunlight to manufacture sugars for their food.
Trees in the temperate zones store these sugars for their winter dormant period.
Carotenoids, which produce yellow, orange, and brown colors in such things as corn, carrots, and daffodils, as well as rutabagas, buttercups, and bananas.
Anthocyanins, which give color to such familiar things as cranberries, red apples, concord grapes, blueberries, cherries, strawberries, and plums.
Tannins, are responsible for the brown hues in the leaves of some oaks and other trees.
The golden yellow in some leaves such as beech are a result of tannins being present along with the yellow carotenoid pigments.
These compounds are always present in the leaves, but only become visible as chlorophyll ad carotenoids disappear from leaves.
Tannins are bitter substances responsible for the color and flavor of tea.
These chemicals are water soluble and appear in the watery liquid of leaf cells.
Both chlorophyll and carotenoids are present in the chloroplasts of leaf cells throughout the growing season.
Most anthocyanins are produced in the autumn, in response to bright light and excess plant sugars within leaf cells.
During the growing season, chlorophyll is continually being produced and broken down and leaves appear green.
Phosphate is at a high level.
Phosphate has a vital role in the breakdown of the sugars manufactured by chlorophyll.
But in the fall, phosphate, along with the other chemicals and nutrients, moves out of the leaf into the stem of the plant.
When this happens, the sugar-breakdown process changes, leading to the production of anthocyanin pigments.
As night length increases in the autumn, chlorophyll production slows down and then stops and eventually all the chlorophyll is destroyed.
The brighter the light during this period, the greater the production of anthocyanins and the more brilliant the resulting color display that we see.
When the days of autumn are bright and cool, and the nights are chilly but not freezing, the brightest colorations usually develop.
Carotenoids and anthocyanins that are present in the leaf are then unmasked and show their colors. The carotenoids occur, along with the chlorophyll pigments, in tiny structures called "plastids" within the cells of leaves.
Sometimes they are in such abundance in the leaf that they give a plant a yellow-green color, even during the summer. But usually we become aware of their presence for the first time in autumn, when the leaves begin to lose their chlorophyll.
Certain colors are characteristic of particular species.
Oaks turn red, brown, or russet;
Hickories turn golden bronze;
Ash species (those that are still alive) turn yellow or purple.
Aspen, Cottonwood Tulip, and Poplar, are a golden yellow.
Dogwood turn purplish red;
Beech, light tan.
Sourwood and black Tupelo turn crimson.
Maples differ species by species-red maple turns brilliant scarlet.
Sugar maple, orange- red; and black maple, glowing yellow.
Striped maple becomes almost colorless.
Sweetgum is known for its showy autumn foliage of different colors at the same time.
Leaves of some species such as the elms simply shrivel up and fall, exhibiting little color other than drab brown.
Are you getting them idea here?
The timing of the color change also varies by species.
Sourwood in southern forests can become vividly colorful in late summer while all other species are still vigorously green.
Oaks put on their colors long after other species have already shed their leaves.
These differences in timing among species seem to be genetically inherited, for a particular species at the same latitude will show the same coloration in the cool temperatures of high mountain elevations at about the same time as it does in warmer lowlands.
How does weather affect autumn color?
For years, scientists have worked to understand the changes that happen to trees and shrubs in the autumn.
Although we don't know all the details, we do know enough to explain the basics and help you to enjoy more fully Nature's multicolored autumn farewell.
Three factors influence autumn leaf color-leaf pigments, length
The amount and brilliance of the colors that develop in any particular autumn season are related to weather conditions that occur before and during the time the chlorophyll in the leaves is dwindling.
The best places in the world for viewing fall colors is probably the Eastern United States and The Great Lakes Region.
This is because of the climate there, and the wide variety of deciduous trees.
The brightest colors are seen when late summer is dry, and autumn has bright sunny days and cool (low 40's Fahrenheit) nights.
Then trees make a lot of anthocyanin pigments.
A fall with cloudy days and warm nights brings drab colors. And an early frost quickly ends the colorful display.
Temperature and moisture are the main influences.
A succession of warm, sunny days and cool, crisp but not freezing nights seems to bring about the most spectacular color displays.
During these days, lots of sugars are produced in the leaf but the cool nights and the gradual closing of veins going into the leaf prevent these sugars from moving out.
These conditions-lots of sugar and lots of light-spur production of the brilliant anthocyanin pigments, which tint reds, purples, and crimson.
Because carotenoids are always present in leaves, the yellow and gold colors remain fairly constant from year to year.
The amount of moisture in the soil also affects autumn colors.
Like the weather, soil moisture varies greatly from year to year.
The countless combinations of these two highly variable factors assure that no two autumns can be exactly alike.
A late spring, or a severe summer drought, can delay the onset of fall color by a few weeks.
A warm period during fall can also lower the intensity of autumn colors.
A warm wet spring, favorable summer weather, and warm sunny fall days with cool nights should produce the most brilliant autumn colors.
What triggers leaves to drop?
In early autumn, in response to the shortening days and declining intensity of sunlight, leaves begin the processes leading up to their fall.
In late summer the veins that carry fluids into and out of the leaf are gradually closed off as a layer of special cork cells forms at the base of each leaf.
As this cork layer develops, water and mineral intake into the leaf is reduced, slowly at first, and then more rapidly.
It is during this time that the chlorophyll begins to decrease.
Often the veins will still be green after the tissues between them have almost completely change color.
These clogged veins trap sugars in the leaf and promote production of anthocyanins.
(You probably have seen leaves like this before and never gave it a thought.)
Once this separation layer is complete and the connecting tissues are sealed off, the leaf is ready to fall.
Here is an interesting tidbit.
Research shows and suggests that fall colors help birds during migration by finding food sources.
Learned and instinctive behaviors help birds to locate food by fall leaf coloration.
Certain shades of red or other colors mean certain fruits and berries
An example would be:
Native shrubs and trees like Red chokeberry (Aronia arbutifolia) and Black chokeberry (Aronia melanocarpa) are good choices for naturalistic sites and can tolerate moist conditions.
The bright red fall color is matched by the plant’s bright red berries, guaranteed to attract migrating birds.
It works for hummingbirds, why not other birds?
Birds know that certain colors mean food.
Creating wildlife habitats and birdscaping your yard just got a bit more fun and interesting, didn't it?
How wondrous that nothing goes unnoticed or goes to waste in the natural world.
It's amazing how God's wonders that can take our breath away and blow our mind at the same time.
Well<< FIRST_NAME_OF_SUBSCRIBER>>, it's time to fly for now.
Before I go, here is your positive thought for the week.
“Patience is waiting.
Not passively waiting.
Another one of my favorite verses.
"But those who hope in the Lord Will renew their strength. They will soar on wings like eagles; They will run and not grow weary, They will walk and not be faint."
"Treat the earth well:
It was not given to you by your parents,
It was loaned to you by your children.
We do not inherit the Earth from our
Ancestors, we borrow it from our Children."
Ancient Indian Proverb
Your friend indeed,
Better yet, have them sign up so they can receive their own letters.
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