Spring and autumn are the eternal laws of the world. Every autumn, especially in the north, it seems that the trees all over the world are covered with red and yellow autumn clothes. It's a sign of late autumn. We often think: why do the leaves turn yellow in autumn? Let's take this question to discuss why leaves turn yellow in autumn.
The reason why the leaves of trees turn yellow after autumn comes, trees feel the climate change from autumn, so that a large number of their own chlorophylls cover the green, people naturally see the leaves turn red or yellow. In autumn, deciduous trees stop growing and only need a small amount of nutrients to survive. Before defoliation, the tree trunk first decomposes chlorophyll, and the substances produced by decomposition are transported from the leaves to the tree hate as winter nutrition. After the decomposition of chlorophyll, the leaves are left with heme, so you can see the leaves turn from green to yellow. The reason why the leaves are green is that they contain chlorophyll. But in addition to the green pigment in the leaves, there are also red pigment, yellow pigment and many other pigments, but in a small amount. In autumn, the green pigment gradually fades away, and the red pigment and yellow pigment are exposed.
All leaves contain green chlorophyll. Trees use chlorophyll to capture light energy and store it in the form of chemicals such as sugar with the help of other substances in the leaves. In addition to chlorophyll, many leaves also contain yellow, orange and red and other pigments. Although these pigments can't photosynthesize like chlorophyll, some of them can transfer the captured light energy to chlorophyll. In spring and summer, the content of chlorophyll in leaves is much more than that of other pigments, so the leaves show the green color of chlorophyll, but can not see the color of other pigments.
"As the leaves age, the amount of chlorophyll in them is reduced," said yoshizo Yamada, a professor who specializes in chlorophyll decomposition at the University of science and technology in Shizuoka, Japan When chlorophyll is broken down, the green of leaves becomes lighter and lighter, and other pigments contained in leaves are highlighted, among which the pigment reflecting yellow light is called "lutein". New leaves contain about eight times more chlorophyll than lutein. Spring and summer yellow are covered by green, we can't see it. As the leaves age, although all the pigments contained in the leaves will be decomposed, but the decomposition speed of lutein is relatively slow, so the leaves gradually turn yellow.
Conclusion: in autumn, the leaves turn yellow. In fact, the decomposition speed of chlorophyll is much faster than that of lutein. When the chlorophyll is decomposed, only lutein is left, so we can see that the leaves on the trees are yellow in autumn.
Why do leaves turn yellow in autumn