Walking through the zoo in the last days of autumn, visitors admire the trees dressed in gold and crimson robes. And did everyone think about why the leaves are yellow and red in autumn?
Today we would like to talk about what makes the leaves of trees and shrubs so beautiful - about the dyes they have.
Apparently, everyone knows about chlorophyll, which gives the leaves a green color. It is in the molecules of chlorophyll under the action of sunlight happens photosynthesis - from water and carbon dioxide are formed hydrocarbons and oxygen. Hydrocarbons are cellulose, which is the building material of all plant components, sucrose and fructose, which give the fruit a sweet taste, starch found in potatoes, and others. Photosynthesis takes place only under certain physical conditions - at the proper temperature and light.
When the day shortens in the fall and the temperature drops, photosynthesis slows down and eventually stops. Chlorophyll molecules are destroyed by light, the green color disappears, the leaves turn yellow.
Yellow color of leaves is given by carotenoids - carotenes and oxidized forms of carotenes xanthophylls - lutein and violoxanthin. They are also in the green leaf, but then their color is masked by chlorophyll. Carotenoids play a supporting role in photosynthesis, expanding the spectrum of light absorbed. Carotenoids determine the color not only of autumn leaves, but also yellow flowers, fruits and vegetables.
And red, pink, crimson, cherry color leaves give anthocyanins. By chemical type, they are glucosides. Unlike yellow pigments, green leaves do not have them, they are formed only in autumn, under the action of light when the temperature drops. These dyes cause blue, pink, red, blue, purple colors of flowers, as well as berries - currants, cherries and others.
Everyone knows that dressing in the autumn colors the trees thus preparing for winter. Shorter days let the internal clock of the tree know that it is time to gradually stop the supply of water and nutrients to the leaves. Each leaf in response forms a partition at the base of the stem. It is similar in composition to the bark and blocks metabolism between the leaf and stem. Because of this, the leaf eventually falls off.
Here is a very short answer to the question: why are the leaves yellow and red in autumn?
We would like to note that November at the zoo is an amazing spectacle. Circling in a slow circle, the leaves fall to the ground, covering it with colorful carpets. And with each passing day, which is approaching the end of the autumn season, you can see this phenomenon more and more often.
So, don't forget to visit Mykolaiv Zoo to plunge into an autumn palette of colorful November!