Autumn leaf fall is an unusually bright and amazing natural phenomenon that is striking in its beauty. Looking at the flying golden leaves that are covered with soft carpets, the question certainly arises: how is this process arranged and why, in fact, do the leaves fall in autumn?
Many tree species are exempted from leaves to survive in adverse weather conditions. In the tropics and subtropics, foliage crumbles at the beginning of the dry season, in regions with a temperate climate, trees lose their leaves in the fall, when cold weather is approaching. Trees that drop leaves at certain times of the year are known as deciduous trees. Trees whose leaves do not fall are called evergreen trees.
Most species of deciduous trees have broad leaves that crumble in cold or dry weather. Evergreen trees, unlike deciduous trees, grow in a humid, warm climate, or have weather-resistant needles.
Interesting fact: Evergreen trees retain their leaves throughout the year, as their leaves are coated with wax, which protects them from the cold, and their cells contain antifreeze chemicals that prevent the tree from freezing at low ambient temperatures. Deciduous trees, on the other hand, are very susceptible to cold.
Causes of fall foliage:
- daylight hours
- leaf damage;
- arid climate;
- cold climate;
- pollination of trees.
Daylight hours
In the fall, daylight hours gradually decrease. With decreasing exposure to daylight in the leaves, the production of chlorophyll, the green pigment, by which the plant absorbs sunlight and then turns it into nutrients, decreases; and the process of photosynthesis slows down (which is carried out with the participation of chlorophyll) until it stops.
As a result of this, the production of sucrose, which plants use as food, is stopped, and, therefore, the supply of nutrients to the tree is limited. To reduce the need for nutrients and resist cold or drought, trees drop foliage.
Interesting fact: It has been observed that forest trees drop foliage faster than urban trees. This is due to the fact that the city has more lighting, including artificial (lights, light from windows, cars, etc.).
Leaf damage
By the end of summer, leaves are damaged by insects, diseases or general wear and tear and are ready for renewal. With the advent of autumn, trees are exposed to low ambient temperatures, cold winds and other conditions that also damage the leaves. For these reasons, the leaves are falling. In addition, in addition to nutrients, harmful substances (metabolites, excess mineral salts) are collected in the leaves. Therefore, getting rid of the leaves, the plant is cleaned.
Arid climate
In hot weather, the leaves evaporate a lot of moisture. The roots of the tree, supplying leaves, lose a large amount of water. Coniferous foliage, so-calledevergreen trees do not fall, since their needles, occupying a small surface area, require less moisture than deciduous trees. Thus, deciduous trees dump foliage during the dry period to reduce the need for moisture and to avoid drying out.
Cold climate
In autumn, trees, sensing a decrease in daylight and a drop in air temperature, begin to prepare for the cold. To preserve a sufficient amount of water and energy resources for the winter period, plants accumulate nutrients and get rid of leaves. This process occurs cyclically and does not harm the plant. So begins the autumn leaf fall.
Nutrient accumulation
Trees collect valuable nutrients (nutrients) from the leaves and store them in the roots for future use. Chlorophyll (the pigment that colors the leaves green) is the first to decompose into nutrients. By the way, in connection with this, the leaves change color in the fall from green to orange, crimson, and gold.
Separation of leaves from a tree
The leaves are cut off from the tree with the help of a separation layer, which is formed at the place where the leaf stem connects to the branch, and is a cluster of cells. As the autumn days are shortened, this layer clogs the vessels on the stem of the leaf, which move water to the leaf and nutrients to the tree. After the stem is clogged, the layer becomes dry and scaly and, as a result of decomposition, separates the leaf from the tree.In the place of fallen leaves in the spring, new stems appear and leaves grow.
Trees, getting rid of the leaves, enter a state of suspended animation, which is compared with deep sleep. At this time, the plant uses the reserves of nutrients deposited in the summer.
The benefits of fallen leaves
Fallen leaves do not lose ecological significance. When decomposed, their beneficial substances flock to the soil and feed future generations of plant and animal life. Thanks to this, the tree receives the necessary nutrients for growing new leaves. In addition, a layer of discarded leaves covering the soil warms the tree and protects it from freezing in the cold season.
It is likely that fallen foliage is the main factor in the survival of not only trees, but also forests as a whole.
Tree pollination
Dropping leaves by trees also increases the efficiency of pollination of flowering plants. When there are no leaves on the branches, wind pollen spreads over large areas and, accordingly, covers more trees.
The answer to the question why the leaves fall in the fall is obvious: leaf falling helps trees retain energy and water, i.e., performs an energy-saving function and maintains water balance in the plant body. Dropping leaves is a way of adapting trees to weather conditions.
In addition, the falling of leaves on trees does not depend solely on climatic changes, this is a natural process laid down by nature in the biological cycle (indoor plants also drop leaves), which helps them to renew.
