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| Photo Credit: Bryce H. Lane |
| Check out the bright oranges and yellows produced by pigments in this sassafras. |
Fall is one of my favorite seasons. We finally get some relief from the oppressive summer heat, and the cooler weather brings a new palate of fall colors. This is also the time of year that drivers struggle to keep their eyes on the road and off the brilliant autumn hues that drape the roadsides.
One neat thing about fall is that every year it looks different: Sometimes the seasonal transition is earlier; sometimes it’s later. Sometimes it’s spectacular; other years it’s slightly less impressive. There are lots of factors that weigh into how colorful fall will be, but the main one is weather – that’s what determines when leaves will change, as well as if a given year’s autumn show will be something worth talking about. | Add Photo to Journal |  | | Photo Credit: Bryce H. Lane | | Sugar maples are a winner when it comes to displaying soft, consistent yellow color in fall. |
Leaves contain pigments that visually tell us that a tree is undergoing a transition. In the fall, we observe this transition by watching the leaves change color. A given season’s weather determines how much pigment we see. Here’s the neat little science lesson behind it all:
Leaves are green thanks to the presence of chlorophyll, a green pigment that’s necessary for plants to produce food. As temperatures decrease in fall, chlorophyll production slows. As this happens, the green fades, allowing other pigments – usually hidden by the chlorophyll – to show through. Just like “chlorophyll” is the name for “green pigment,” the other pigments have “fancy” names, too. “Carotenoids” are the yellow and orange pigments present in leaves (easy to remember because “carrots” are orange). “Anthocyanins” are the purples and reds. Weather conditions actually determine the presence of these pigments and the intensity of the color each year.
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