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autumn leaves
2008-Oct-02, Thursday 09:25 pmI'll start with the photo. Lecture afterward. :)
Back in October 2003, I think it was, I picked some leaves from plants around the parking lot where I worked at the time. I put them in a flatbed scanner and created this photo. It's available in 1600x1200 pixels, if you keep clicking links to the original photo.
It's made a nice autumn desktop for my pc for a few years. Maybe someone else will enjoy it too. Now time for the lecture....
I've long read that leaves turn color in the fall because the tree works to prevent moisture loss. As the air changes temperature, it cannot hold as much water per cubic meter when the air is cold versus when it is warm. To keep from drying out (getting freezer burned, essentially), a tree loses its leaves during the cold season. Before it drops the leaves, it tries to recover some of the nutrients, nitrogen, and chlorophyll (?). As the chlorophyll breaks down, other pigments (which had been there all along) show their colors.
But why these particular colors? Is one dying leaf the same as any other dying leaf?
Maybe not. Some researchers think that plants may develop a red leaf as a way to further conceal (even after the green chlorophyll is gone) the underlying yellow color that would remain. Yellow, apparently, is very enticing to some insects that are harmful to trees. The scientists tested their theory by creating a color test for aphids, giving them opportunity to mate and lay eggs on backgrounds of 70 different colors.
Back in October 2003, I think it was, I picked some leaves from plants around the parking lot where I worked at the time. I put them in a flatbed scanner and created this photo. It's available in 1600x1200 pixels, if you keep clicking links to the original photo.It's made a nice autumn desktop for my pc for a few years. Maybe someone else will enjoy it too. Now time for the lecture....
I've long read that leaves turn color in the fall because the tree works to prevent moisture loss. As the air changes temperature, it cannot hold as much water per cubic meter when the air is cold versus when it is warm. To keep from drying out (getting freezer burned, essentially), a tree loses its leaves during the cold season. Before it drops the leaves, it tries to recover some of the nutrients, nitrogen, and chlorophyll (?). As the chlorophyll breaks down, other pigments (which had been there all along) show their colors.
But why these particular colors? Is one dying leaf the same as any other dying leaf?
Maybe not. Some researchers think that plants may develop a red leaf as a way to further conceal (even after the green chlorophyll is gone) the underlying yellow color that would remain. Yellow, apparently, is very enticing to some insects that are harmful to trees. The scientists tested their theory by creating a color test for aphids, giving them opportunity to mate and lay eggs on backgrounds of 70 different colors.
After two weeks, they found that traps appearing green to humans caught on average more than three times as many aphids as the red traps, but yellow traps attracted even more, around four times as many as the green ones.So even as the leaves "die", they may still be working to play a part in the health of their tree. Although the theory is not accepted yet, it already has people thinking about pest control possibilities. Maybe growing a red-leafed variety alone would help reduce pest problems.
