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Why are trees so clourful in autumn?

Кампус КПІ. 1 корпус восени

I think these lines of Alexander Pushkin are familiar to all. And all students of KPI can enjoy by trees that are dressed in the gold and purple robes at our university.

The most famous of them – a kind of Internet stars and wedding photos – golden maple and purple smoke tree in front of the first building, near the monument to the great mechanics Stepan Tymoshenko. Beautiful photos of autumn trees from the park of KPI often can be seen at the exhibition of  "Talents KPI" on the Internet. They were in the pages of our newspaper.

And today I would like to talk about what makes the leaves of trees and bushes so beautiful – about colors, which they have. So why autumn leaves are yellow and red?

I think everyone knows chlorophyll, which makes leaves green. In the molecule of chlorophyll photosynthesis is occurring under the  influence of sunlight - from water and carbon dioxide produced hydrocarbons and oxygen. Hydrocarbons - is a cellulose, which is a structural material for all components of plants, sucrose and fructose, which gives a sweet taste to fruits, starch that exists in potatoe, and others. Photosynthesis happen only in certain physical conditions – at the appropriate temperature and light. When in autumn day becomes shorter and temperature decreases, photosynthesis slows down and then stops. Chlorophyll molecules are destroyed by light, the green color disappears, leaves become yellow.

Carotenoids provide leaves with yellow colour. Carotenoids it is carotenes and xanthophylls oxidized forms - lutein and violoksantyn. They are in the green leaves, but then their color masks the chlorophyll. Carotenoids play a supporting role in photosynthesis, expanding the spectrum of light that is absorbed while this process. Carotenoids cause the color not only to an autumn leaves, but to the yellow flowers, fruit and vegetables.

Anthocyanins dyes cause to  leaves a red, pink, purple, cherry colour. By chemical type they are glucosides. Unlike the yellow pigments,  they are absent in green leaves,  they produced only in autumn under the influence of sunlight and low temperature. These dyes cause blue, pink, red, blue, purple colours to flowers  and berries such as blackberry, cherry and others.

So, the brief answer on the question why leaves are yellow and red in autumn. Of course this answer is not complete. The full answer you can find in the works of specialists on plant physiology, who studied not only the role of various dyes in plant life, but also studied changes that occur in trees in autumn, the significance of defoliation and many other issues.

In the end I want to notice that before the first building grows one more smoke tree it is near the monument to the first principal of KPI Victor Kirpichev. In autumn it is protected from sunlight and it remains green for a long time and  rarely becomes red. And demonstrates the importance of sunlight for the leaves to change their colour.

V. Mykolayenko


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