&#91FOUNTAIN&#93Where the green goes

“On a day as green as dazzling.
Long for someone whom you miss.
There, there, in the place of autumn flowers,
green colors have worn out, and autumn
leaves turn red...”
It is a poem by Midang Seo Jung-ju, “The Green Day,” which singer Song Chang-sik has remade into a popular song.
The poem follows the shift from “sunny days” to “the loss of green” to “autumn leaves.”
That is the same principle of leaves turning red, botanists explain. Red leaves are an aging phenomenon. In the leaves where photosynthesis declines because the hours of sunlight shorten as winter approaches, red and yellow pigments are revealed instead of the green chlorophyll. It is well known how this physiological phenomenon takes place, but there are still many things to wonder about concerning how climate affects the red color and why trees repeat this every year.
Red autumn leaves are products of stress and daily changes in temperature. The more stress a tree receives, the stronger its color becomes. This is the basic explanation by a U.S. physiologist. If warm and sunny days continue, the leaves which still have chlorophyll create through photosynthesis energy in the form of sugar and then send the sugar to all the tree’s tissues. If the night temperature is below 10 degrees centigrade (50 degrees Fahrenheit), the movement of sugar stops. The sugar, which has accumulated, turns to red from a pigment called anthocyan. As the sunny days and cold nights continue, the leaves turn even more red.
Red autumn leaves are more beautiful in the mountains than in the plains, in sunny rather than shady areas.
Clouds, rain and wind are enemies of red autumn leaves. If cloudy days persist, sugar is not created and strong rain and wind may cause the leaves to fall before the color is fully realized.
Botanists say trees have evolved in this way to fight off harmful insects, which try to lay eggs inside a tree’s bark to survive the winter. It means red leaves are a survival strategy.
Korea’s rainy season is over, but clouds and showers are still frequent. Even Typhoon Maemi has had an effect. As a consequence, prospects for a good leaf-viewing season are dim, according to the Korea Meteorological Administration.
This fall will make us wish that there had been more “sunny days.”

by Lee Kyu-youn

The writer is a deputy city news editor of the JoongAng Ilbo.