The leaf is an aerial part of plants and provides a number of critical functions. One of them is the upward and downward flow of water with nutrients dissolved in it. This largely happens with the help of vascular-fibrous bundles - veins. They are easy to see on a leaf blade, even with the naked eye. The venation of leaves, its types and features of functioning will be considered in our article.
What are leaf veins
Surely, looking at the leaf blade, you noticed intricate patterns on its surface. This is the veins of the leaves. But this is not just a characteristic pattern. It is an element of the conductive tissue of plants. Veins, which are also called vascular-fibrous bundles, consist of vessels and sieve tubes. The first provide an upward flow of water. Its essence lies in the movement of liquid with minerals dissolved in it from the root to the leaves. This process is very important, because water is a necessary condition for the implementation of the photosynthesis process.
Leaf venation provides the reverse process. Its essence lies in the movement of organic substances that were formed in the leaf during photosynthesis, to other parts of the plant. This is done by the sieve tubes of the conductive tissue. As a rule, the vessels are located above the sieve tubes and together form the so-called core of the sheet.
Types of venation sheet
Vascular-fibrous bundles are located in leaves in different ways. The nature of their location - this is the venation of the leaves. This symptom is systematic. This means that by its type it is possible to determine the classification unit of the plant. For example, net venation is characteristic of the leaves of dicotyledonous plants. Such a pattern are the leaves of cherries, pears, apples. A parallel and arc - for monocotyledons. Examples of plants with this type of venation are lily of the valley, leeks, wheat, and barley. The nature of venation is easy to determine visually. Let's take a closer look at its main types.
Parallel venation of leaves
There is a clear relationship between the type of leaf blade and venation. Consider this with wheatgrass. This plant with linear leaves is a malicious weed. Getting rid of it can be quite difficult. Veins on such leaves are actually located almost in one line. This type of venation is called parallel. It is characteristic of all cereals, which are representatives of monocotyledons.
Arc venation
If the leaf blade is wider but elongated, then the veins come out of its base. Then they diverge in the form of arcs, and connect at the top. The main vein cannot be distinguished among them, since they are all of the same shape and size. This is an arc venation of leaves, which is characteristic of plantain, lily of the valley, tulip.
Mesh venation
This type of venation is most common in nature. This fact is easy to explain. Mesh leaf venation is characteristic of the green part of all dicotyledonous representatives, and they occupy a dominant position in the plant world. In terms of numbers and species diversity, they significantly exceed all others.
Everyone saw the leaves of maple or apple tree. The main vein is clearly distinguished on them. Less noticeable second-order vascular-fibrous bundles extend from it in both directions. In relation to each other, they are located almost in parallel. From the veins of the second order, in turn, even smaller ones depart. Together, they form a dense network of elements of the conductive tissue of the leaf blade. For the effective provision of all the substances necessary for life, this is the most perfect type of venation. Plants of the families Rosaceae, Cabbage, Legumes, Solanaceae, Asters are a vivid example.
So, to summarize: leaf venation is the nature of the arrangement of vascular-fibrous bundles on the plate. They are elements of a conductive tissue and provide the movement of nutrients throughout the plant. There are three main types of venation: mesh, parallel and arc.