Home Grounds Blog

“There’s a crispness in the air that greets the morning sun, a feeling of anticipation, a new day has begun.

Harvest days are ending, winter is drawing near, yet in between is surely the most special time of year.
They call it Indian Summer, and it seems to fit the bill, for it’s as if the Lord took a feathered brush and painted all the hills”
Excerpt from “Autumn” by Julie L. O’Connor

 

florida maple 4.JPGBeing a born and bred Alabamian, I find myself struggling to look forward to the chilly temperatures of our reasonably mild winters. While some folks relish the bitter coldness of ice and snow, I personally find the stifling heat and humidity of Alabama summers a bit more sufferable than our northern neighbors. Although I openly chide the coming cold, there is one benefit of the diminishing daylight and cooling temperatures:  the astounding colors of autumn. Though not being famous for our long autumn and fall seasons, we are blessed to have a state with such varied topography that yields a broad selection of plant life. With over 4,000 species of plants listed in Alabama, we are the 5th most floristically diverse state within the Country. Given that we have a plethora of which to feast our mind and eyes upon, we are destined to see some amazing colors in the ensuing months.  To fully appreciate the varied shades of red, orange, yellow and green that will soon grace our landscapes; I believe that it is important to consider the “behind the scenes” action that takes place to give us such a splendid show.
First, let us take a trip back to middle school science and biology. There are three primary colors of light: red, blue and green. When mixed in certain amounts, we get the colors of yellow, cyan (blue-green) and magenta.  We all learned that the colors we see are those that are reflected by certain pigments. For example, if a shirt appears red to our eyes it is in fact absorbing the blue and green light, thus reflecting red. To continue that, a leaf that appears green is actually absorbing red and blue light waves and reflecting green. The compounds within a leaf that absorb the blue and red light from the sunlight are called chlorophyll. The molecules of chlorophyll are contained within structures called chloroplasts, in which photosynthesis takes place. Photosynthesis is the life giving process of converting carbon dioxide and water into oxygen and carbohydrates using light. The chlorophyll absorbs light from the sun to supply energy used by plants during photosynthesis. Finally, it is important to note here that chlorophyll is considered an unstable molecule when exposed to bright light, and is constantly being broken down and regenerated all summer long.
So, chlorophyll is the compound that is responsible for the everyday green that we all overlook throughout the summer and is generated on warm and bright days. So what is responsible for the shades of fall? In most leaves, two other compounds are also present, carotene and anthocyanin. Carotene is considered an accessory absorber, capturing the blue-green and blue light of the sun and supplying energy for photosynthesis. When combined with chlorophyll, the two reflect the standard green. As the temperatures cool down and chlorophyll production begins to decrease, the more stable carotene reflects several shades of yellow, as often seen in birch and hickory trees in the fall.
While chlorophyll and carotene are spectacular in their own right, the award winner for “best in fall color” is certainly the last compound to be discussed:  anthocyanin. Anthocyanins absorb the blue, cyan and green light, resulting in leaves that contain anthocyanins reflecting the many shades of red that we all know. When mixed with other compounds in the leaf, colors including burnt orange, crimson and even shades of blue can be found. Some plants, such as red oak, red maple, and sumac, contain more anthocyanins than others, giving them a display of the brightest red and deepest purple.
Anthocyanins are formed later, during the cooler and dryer times of the year, when levels of sugar in the plant sap are high. Since cool temperatures mixed with bright light destroy chlorophyll, bright sunny days that have cool nights make for a more gorgeous fall. That being said, I think that we are up for an astonishing show, due to our mostly clear cobalt skies and lack of rain as of late. So, take time this fall to drive the country roads and enjoy the vast array of fall color that our great state gives us. Drive North to Jackson and DeKalb County early and continue your way south as the season progresses; I assure that you will not be disappointed.
 
In parting, I’ll leave you with the final stanza of Ms. O’Connor’s poem:
“…So I say that the eyes are a window, beauty is found within the soul, and upon the hills of Autumn, that are strewn with red and gold…”
 
written by Hunter McBrayer of the Alabama Cooperative Extension System, C. Beaty Hanna Horticulture & Environmental Center, which is based at the Birmingham Botanical Gardens.

 


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