Autumn Colors

[science_spot]

By the time school starts back, I am already itching for autumn.  By far, my favorite season, for the food, the weather, the seemingly brighter moon and the coziness of home.  The color on the trees is a vibrant bonus before the bland grey of winter takes hold. 

(this picture is my beloved black lab - doberman mix, Tela)

 

Have you ever wonder how the leaves get those remarkable colors?  I have seem dull browns, dull and bright yellows, deep and light orange, dull red, bright red and purple-red throughout the years. I live in an area of deciduous forest, meaning the trees lose their leaves for the winter months.  I look forward to taking the kids for a nice road trip to see some leaves (and have a picnic).

Deciduous trees (and shrubs) spend the early summer opening leaves (for energy production) and making new buds for next year.  In June, when these two jobs are complete, the tree starts making sugars (through photosynthesis), which it stores for use in the winter and following spring.  Photosynthesis is supported by a constant manufacture of chlorophyll.  This process of storing sugar continues until it is triggered to stop.  The trigger is the length of the day.

As the days get shorter in late August and early September, the tree stops storing the sugars by blocking the supply chain from the leaves (the source of the sugars made through photosynthesis).  The tree also stops its production of chlorophyll, and within a few days the total chlorophyll (green color in the leaves) is decreasing rapidly.

As the chlorophyll content decreases to zero, the other pigments become visible.  These other pigments have always been in the leaves, but the high amount of green chlorophyll hides them until autumn when the chlorophyll is gone.  These other pigments are:

• Carotenoids - orange pigments, always found in the leaves, helping with photosynthesis.  The most common is the carotene, like that which made carrots so famously orange!
• Xanthophylls - yellow pigments, always found in the leaves, helping with photosynthesis.  These yellows also make egg yolks yellow.
• Anthocyanins - red (bluish red) pigments, made only in autumn from sugars left in the leaves.  These bright reds are commonly found in flowers and fruits.

Once the leaves have completely converted to colorful, having stored or used all the remaining sugars, one final thing happens.  Death overcomes the cells that originally cut off the sugar supply chain from the leaves to the rest of the tree.  This leaves them brittle and the leaves thenfall from the trees.  As the leaves lay on the ground, the pigments break down in the presence of light, which fades them until no color remains.  This is when the brown colors from the tannin pigment family begin to show, as the leaves begin their decay in the wet, late autumn.

The intensity of the leaf color, longetivity of the foilage season and speed of change depend on a variety of factors, including sunlight, length of day, temperature and precipitation.

 

Do you plan to spendsome time viewing the color change in your area?  Do you ever take pictures? If not, the United States National Arboretum has a nice Fall Foliage Gallery!

 

Tonya

AKA sunmoonstars

The Science Spot

 

[arthistmom]

Sep. 14, 2009 at 1:00 PM

Unfortunately, SoCal doesn't do autumn colors. What we have instead is fire season. :-( The showy fall foliage is definitely one thing I miss about upstate NY. That and lilacs in the spring. Lucky you!

[Momforhealth]

Sep. 14, 2009 at 1:05 PM

I grew up in WI but now live in TX.  I tend to automatically start wanting to wear sweatshirts around this time of the year...but the change usually doesnt start until October November down here.  Not nearly as vibrantly beautiful as it was back home.  :( Its 70's right now but will be back up into the 90's by the weekend.  I miss the fall.

[deadheadjen]

Sep. 14, 2009 at 1:19 PM

CT is gorgeous for leaf peeping. Lots of vibrant colors, stone walled fields, fall festivals...sigh. Good stuff.

p.s. tela is adorable.

[sati769leigh]

Sep. 14, 2009 at 2:45 PM

i love autumn!! love the holidays, the crisp air, the colors!! ahhh its wonderful!

[roseisrose]

Sep. 15, 2009 at 2:20 PM

this is so cool. I had NO idea about the colors. I just love Fall~ its my favorite!

thanks for the post. :)