Saturday, December 8, 2012

Why Do Leaves Change Their Colors?

Autumn is my obsession - hence the tattoo

So, why is autumn my obsession? I always adored it as a kid. The moment school started and I had brand new notebooks and a clean slate, a fluffy sweater and a chilly nose while waiting for the school bus, I was anticipating the change in my life (every year hoping I’d be more popular, get better grades, get an awesome boyfriend), I was also anticipating the change in the trees. I remember one particular time when I walked through the woods and stopped in a field. All around me every tree was a completely different color. None of them were the same. I spun in circles until the colors blended into an orange mix in my periphery and then I rushed past the trees, picking one leaf from each, skipping home and ironing them between wax paper to try to preserve that feeling. It was as if their colors were a sign that they were all screaming for my attention. After a spring and summertime of green, green, and more green—there was color! Each tree became an individual like a human with a face.

So, what makes trees change color? Most people assume it’s climate or moisture but it’s actually the length of nighttime. These longer nights create a chemical change. There are three types of pigment involved in fall colors: Chlorophyll which we know as the chemical that creates the plants’ green color. Carotenoids which produce yellow, orange and browns, and anthocyanins which create red. As autumn arrives, the chlorophyll production goes down with the longer nights (less sunlight). The other two chemicals present in the leaves show at this point; the carotenoids and anthocyanins. Some species take longer to change colors. Temperature and moisture during the time that chlorophyll is lowering is what influences the brilliance of the colors.

Here in Phoenix, the trees that do change usually do so at Christmas. And, I stop in parking lots where deciduous trees are and gather up the little samples just like in childhood, only I don't spin around or I'm likely to be run over by a soccer mom in an SUV.

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