Tuesday, September 14, 2010

Colorful Leaves

I guess I never really thought about why the leaves change... We don't get much of a 'fall' out here, but when we see the few trees that do change color, Ryan and I are always quick to point out 'FALL'.

Why Do Leaves Change Color in Fall?

How do leaves change from green to yellow, orange and red? And what's in store for us this year? We have the answers.

Why do leaves change color?

It's one of those questions – like, why is the sky blue? – that can stump a parent on an otherwise enjoyable fall walk. So let's answer the question.

Most simply, to survive the winter, deciduous trees need to store nutrients in their roots, which means they must absorb the nutrients in their leaves. Changes in color are triggered as the trees absorb essential nutrients. Here's how it works:

Throughout the warm sunny months, trees are lush and green because they're working hard. Tree leaves are green because the abundance of the pigment chlorophyll, which is essential to converting sunlight, water and carbon dioxide into energy-rich sugars. If plants hadn't figured out the trick of photosynthesis, we'd all be out of luck, since the energy humans need to live comes from plants, or the animals that eat plants. Tree leaves are also busy using other essential nutrients, like nitrogen and phosphorus (the same main ingredients in most store-bought fertilizers, or in compost), so these nutrients are abundant in summer foliage.

As summer wanes, changes in tree leaves are triggered by the cooler temperatures, changes in rainfall and weather, and most of all, the shortening of daylight hours. Much of the change happens without our knowing it, as trees begin to absorb essential nutrients and store them in their roots so they are available for the following spring. As the trees absorb the last of the chlorophyll, however, the brilliant colors we associate with autumn begin to appear.

The rest of the article here.

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