Why are autumn leaves in the United States and Europe different?

Walking out into the streets in the autumn, brilliantly colored leaves adorning the trees is a wonderful sight. In Europe the leaves in autumn are mostly yellow, while in the United States and East Asia the leaves are bright red. Why is there such a color difference?

A new theory by Professor Simcha Lev-Yadun of the Department of Educational and Biological Sciences at Haifa-Oranim University and Professor Jarmo Holopainen of Kuopio University in Finland and published in New Phytologist magazine, turned 35 million years ago to decipher this mysterious color.

The green color of the leaves is due to a large amount of chlorophyll pigment in the leaves. The change in the color of the leaves to red or yellow when the fall comes is not the result of the leafy leaves, but a series of processes - the difference between red and yellow autumn leaves. When the chlorophyll pigment in the leaves decreases, the existing yellow pigment will prevail and produce the color for the leaves. The red leaves are a result of another process: When the chlorophyll decreases, the red pigment, anthocyanin, which is not previously present, is produced in the leaves. These facts have only recently been discovered and lead to a series of other studies that explain why plants use their resources to produce red pigments when they are about to shed their leaves.

The explanations for this phenomenon are very diverse and there is no agreement on this issue yet. One of them said that the chromatogram was created as a result of some physiological functions that redistribute amino acids to the wood parts of the plant to provide protection from light and cold damage. price caused. Other explanations show that the red pigment is created as a plant strategy to protect itself from insects growing in the amino acid family. But regardless of the answer, these explanations do not help us understand why the process of producing anthocyanins, red pigments, does not appear in Europe.

An evolutionary ecology method deduces that the color of autumn leaves is the result of an evolutionary war between plants and insects that use plants as hosts. In the fall, when the beetles suck the amino acid from the leaves and then lay the eggs, the leaves turn red because the aphids are often attracted to the yellow color, thereby warning insects about the quality of the plant's defense to make reduce the parasite's desire to parasite.In this case, the protective logic of the red pigment seems reasonable, but the gold leaf phenomenon cannot be explained by this method. And to solve that problem, a new theory is applied.

According to the theory of Professor Lev-Yadun and Professor Holopainen, until 35 million years ago, large areas of the earth were covered by 'evergreen' forests with tropical trees. During this period, a series of ice ages and dry conditions led many plants to evolve into deciduous species. Many of these plants begin to evolve to produce red pigments in leaves to repel insects. In North America and East Asia, mountain ranges from North to Na, allow plants and animals to 'migrate' to the south or north with the advancement and retreat of the ice according to climate fluctuations. And, of course, the insect enemies of trees also migrated. So the war of survival is always going on. In contrast, in Europe. Its mountains - the Alps and its other branches - spread from East to West, and therefore no 'protected' area was created. Many plants that cannot survive in too cold climates die with insects that rely on them for survival. At the end of the ice age, most of the extant plants in Europe did not need to face many extinct insects, and therefore there was no need to create red leaves to protect themselves.

According to scientists, the evidence supporting this hypothesis can be found in dwarf shrubs growing in Scandinavia, a species that still produces red pigments for leaves in autumn colors. Unlike other plants, dwarf shrubs have survived the ice age under a layer of snow covering them and protecting them from the extreme conditions above. Under this layer of snow, insects that eat dwarf shrubs are also protected - so the war between this plant and insects continues, causing the creation of red leaves is still necessary.