Autumn faces...
One of my all-time favorite shrubs is Disanthus cercidifolius. This Asian member of the witch hazel family is one of the most spectacular for autumn leaf color.
The heart-shaped leaves, reminiscent of redbud, Cercis spp. (and reflected in its specific epithet), are deep blue-green throughout the summer. But, like other temperate woody plants, around the middle of September (at least in northeastern North America) the leaves respond to the lengthening nights and cooler temperatures by breaking down the chlorophyll for future use.
At first, what is revealed are the various yellow pigments (mainly carotenoids and xanthophylls). These are actually present throughout the growing season, but because of the over-abundance of green chlorophyll, one cannot see them.
Solar radiation can be pretty intense on autumn days, even in Ithaca, NY, leading to the production of free radicals that damage leaves. Plants have a way of dealing with this, however. Certain pigments like anthocyanins, which are reddish, are produced and act as antioxidents, nullifying the impacts of excessive solar energy. If the autumn season is cloudy, without any bright days, fall leaf color will remain yellowish, for there is no reason to produce the expensive red pigments. Bring out the sunshine, though, and there can be an explosion in orange, red and purple leaves.
To illustrate this, look at the following sequence of Disanthus leaves:
The little hearts are green to purple, indicating that the days must have been pretty intense to illicit the production of anthocyanin.
But remember, it only happens when the leaves are being bombarded directly with high irradiance. Spread the leaves apart, and what is revealed?
Bright yellow splotches where the leaves had been covered up.
All of this likely took place in a single afternoon. This just goes to show how fascinating and dynamic plants are, and how intertwined the science and aesthetic can truly be.
"No spring, nor summer beauty hath such grace,
As I have seen in one autumnal face"
--John Donne, 'Elegy IX: The Autumnal'
One of my all-time favorite shrubs is Disanthus cercidifolius. This Asian member of the witch hazel family is one of the most spectacular for autumn leaf color.
The heart-shaped leaves, reminiscent of redbud, Cercis spp. (and reflected in its specific epithet), are deep blue-green throughout the summer. But, like other temperate woody plants, around the middle of September (at least in northeastern North America) the leaves respond to the lengthening nights and cooler temperatures by breaking down the chlorophyll for future use.
At first, what is revealed are the various yellow pigments (mainly carotenoids and xanthophylls). These are actually present throughout the growing season, but because of the over-abundance of green chlorophyll, one cannot see them.
Solar radiation can be pretty intense on autumn days, even in Ithaca, NY, leading to the production of free radicals that damage leaves. Plants have a way of dealing with this, however. Certain pigments like anthocyanins, which are reddish, are produced and act as antioxidents, nullifying the impacts of excessive solar energy. If the autumn season is cloudy, without any bright days, fall leaf color will remain yellowish, for there is no reason to produce the expensive red pigments. Bring out the sunshine, though, and there can be an explosion in orange, red and purple leaves.
To illustrate this, look at the following sequence of Disanthus leaves:
The little hearts are green to purple, indicating that the days must have been pretty intense to illicit the production of anthocyanin.
But remember, it only happens when the leaves are being bombarded directly with high irradiance. Spread the leaves apart, and what is revealed?
Bright yellow splotches where the leaves had been covered up.
All of this likely took place in a single afternoon. This just goes to show how fascinating and dynamic plants are, and how intertwined the science and aesthetic can truly be.
posted by guy among the trees at 9:55 PM
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