Every autumn, with a decrease in day length, the leaves of most trees and shrubs change from green to yellow-orange. In the fall, chlorophyll is destroyed in the leaves. The orange and yellow pigments in the leaf cells persist and become visible. This is why the leaves take on an autumn color.
Soon, the leaves that have lost chlorophyll are discarded – leaf fall occurs – a natural process of separation of leaves from stems.
Long before the leaf separates from the stem, a layer of cork is laid at its base. It covers the future leaf scar. A separating layer is formed outside of it. The cells of this layer become mucous, which leads to disruption of the connection between the leaf and the stem. A weak wind is enough – the leaf is completely separated from the stem and falls under the weight of its own plate. The wound is tightened with a cork, forming a leaf scar.
The formation of cork and separating layers occurs long before snow falls and is associated with a decrease in the length of the day.
The meaning of falling leaves
Trees and shrubs shed their leaves so as not to die in winter from a lack of moisture, since the roots of many plants cannot absorb cold water from the soil. During the fall, together with the fallen leaves, harmful substances that have accumulated in the leaf cells by autumn are removed from the plants.
Some plants keep their leaves all winter long. These are evergreen shrubs of lingonberries, heather, cranberries, etc. Small dense leaves of these plants, which evaporate water weakly, are preserved under the snow. Conifers and some herbs overwinter with green leaves, for example, strawberries, clover, celandine.