For Your Eyes Only? The Story Of A Leaf

Leaves are at their most georgous when they're dying. Especially the ones that turn red. But have you ever asked yourself why? Why do they turn beautiful colors? The leaves don't turn red just for our viewing pleasure; nature has to have some benefit for the tree. I set out to find a tree with it's leaves in different stages of turning color, and it didn't take long. It was only a block away. And here is my picture. Until about ten years ago, scientists viewd the changing colors as appealing but pointless. The standard thought now is that leaves don't actually change color. The red was always lurking in the leaf. It is only when the chlorophyll dissappears that the red underneath shows up. In my picture, look at the leaf in the middle; it's in the process of turning. Is it actually changing color, or just revealing the red underneath as the green recedes? It's hard to tell. So now we know how the color changes, but why? Here is the latest theory:aphids. In the fall, aphids are looking for twigs to lay their overwintering eggs. The following spring, the new generation feeds on the tree, damaging it in the process. The red leaves are sending a signal to the aphids: back off! The bugs don't like red, and one reason is that red leaves have a lower nitrogen content in the leaf fluid, which is what the bugs feed on. So it seems that the reason leaves turn red is to ward off insects. Of course, there are still many unanswered questions. Why don't all trees have leaves that turn red? Why do some turn yellow or orange instead? I love a mystery, don't you?