Yellow leaves of the birch, orange-red at the maple, pink at the spindle-leaf - all the variety of shades of autumn foliage is caused by three mixed groups of dyes contained in the cells of fading leaves.
Chlorophyll is responsible for the green color of plants. This is one of the necessary elements in a chain of chemical reactions that allow plants to "eat" light.
Chlorophyll molecules can be found not only in leaves, but also in other green parts of plants. They are not evenly distributed throughout the cell, but are found in the organelles responsible for photosynthesis, chloroplasts. Depending on the intensity of illumination, chloroplasts can move inside the cell, regulating the amount of incoming light.
The color spectrum of leaves and fruits from yellow to red is due to the content of carotenoids. They have an auxiliary role in the process of converting the energy of light into the energy of chemical bonds. In the green parts of plants, carotenoids are present together with chlorophyll, but they become noticeable only when its molecules are destroyed, for example, under the influence of low temperatures and with a decrease in the level of metabolism in tissues.
Pink, purple or blue-violet color parts of plants is made by anthocyanins. These substances are contained in the cell sap and are very sensitive to changes in the acidity and the content of metal ions. According to researches, in autumn leaves anthocyanins accumulate as an adaptive factor, which increases resistance to low temperatures and the ability to withstand pests and diseases.