Leaf fall - what is it? Causes and significance of the phenomenon

Falling leaves ... What is the phenomenon occurs every fall, everyone knows. But why do trees lose their magnificent outfit? The answer to this question you will find in our article.

What is leaf fall?

There is even a fairy tale about leaf fall. It tells that earlier all plants were evergreen. Once the cold came, and all the animals went to the warmer parts. And only a small bird with a wounded wing could not do it. With a request for help she turned to the trees. But they were too busy. Only spruce and pine did not deny it, sheltering from the cold in their branches. And juniper treated berries. As punishment, Moroz ordered the wind to tear down leaves for the winter with indifferent trees.

The phenomenon that we are considering is always a sign of the approaching colds. This applies only to plants that grow in the temperate zone with a clear change of seasons. However, tropical representatives of this kingdom also discard foliage. This usually occurs before a drought.

What is leaf fall? This is a cyclic phenomenon in the life of plants. It can be associated with a variety of adverse conditions, except for colds and drought. For example, this may indicate a mechanical damage, a viral infection or atmospheric toxins. Thus, dropping leaves is a protective reaction of the plant.

Causes of a leaf fall

So why do plants have to periodically change their green attire and what metamorphosis accompanies this process? Before the leaf fall begins, the leaves always change their color. This is due to the transformation of plastids. Chloroplasts contain a pigment called chlorophyll, which makes the leaves green. It is in them that the process of photosynthesis takes place, one of the conditions of which is the presence of water.

When unfavorable conditions occur in the base of the sheet, a plug is formed. It prevents water from entering the sheet. Photosynthesis is impossible, as a result of which chlorophyll is destroyed. But other pigments start to appear, and the leaves get red, yellow, orange or purple. Trees and bushes seem to change their outfit.

Cork fabric, located at the base of the leaf blade, makes this place brittle. Even a small wind can cause the petiole to come off the stem.

Deciduous plants

And what is leaf fall from the point of view of physiology? This is a necessary protection against excessive loss of moisture. Since the surface of the leaf blade is the basis of transpiration, the plant simply gets rid of it. Water is very necessary for the plant to experience the cold period, so it does not make sense to lose it.

Almost all angiosperms are deciduous. But there are exceptions. For example, shrubs of red bilberry, ledum, heather retain leaves. To do this, they have other devices to protect against water loss. So, on the underside of cranberry leaves there are small dimples, the walls of which contain a mucous substance that absorbs water. The process of evaporation of water in the Ledum helps prevent essential oils. They fill in special moves in the leaves of this plant.

Eternal greenery

But there are plants that do not even know what leaf fall is. They are almost all representatives of the Gymnosperms department. "Winter and summer - one color" - this is a mystery familiar to all from childhood about them. The leaves of gymnosperms are called needles. They are very narrow, so the evaporation of water from their surface is negligible.

Evergreen trees lose their leaves only as it ages. On average this happens in 4-5 years. And in the spinous pine, needles can function for more than 40 years. The only gymnosperm that changes its cover when changing the season is larch.

So, leaf fall is a biological process, which has an important protective value in plant life. It can be associated with the change of the season, damage to their organs or the onset of an unfavorable period.