Sheet: functions, description and structure. Functions of conducting beams in leaves

Nutrition and respiration - it is these vital functions that are capable of carrying out plant leaves. Lianas and cacti, grasses and water lilies - each of these plants is a unique kind of leaves give.

Leaf - side part of the shoot

The escape of any plant consists of the axial part - the stem to which the sheet is attached - the side part. This arrangement allows the sheet to occupy the most advantageous position with respect to the sun. The shape and size of the leaves depend on the habitat of the plant. For example, plants of moist natural zones have leaves with large leaf blades for a more intensive process of evaporation of water. If the plant grows in a region with a dry climate, there is no need to lose moisture. Therefore, the leaves of such plants will be small and thin. That's how wise nature created a leaf, the functions of which are so important for plant and animal organisms.

In addition, some leaves can change their shape along with changing environmental conditions. Everyone knows a strepolist in the water has a ribbon-like shape of leaves. It is necessary that this organ can not damage the strong flow of water. When the water becomes smaller and some leaves die, the leaves of the arrow-shaped form grow in their place. Their photosynthetic surface is much larger, which means that the chances of a plant for survival increase significantly.

External structure

The sheet consists of a leaf plate and petiole, with which it is attached to the stem. Some leaves are deprived of petiole, and the place of their attachment is the base of the leaf blade. These leaves are called sedentary.

Each leaf blade has its own way of dissecting. Thus, the leaves of the willow are entire, the oak is pinnately lobed, and the dandelion is pinnately divided. Everyone knows the finger-like leaves near the chestnut tree and the triplets at the clover.

Internal structure

The functions of the plant leaf are interrelated with the features of its internal structure. Outside there is a live cover cloth - skin. It not only protects the sheet. Functions of metabolism, water evaporation and gas exchange are carried out by stomata - special skin structures. They have shutters that can open and close depending on the need for intensity of the process.

The main part of the leaf is filled with chlorophyll-bearing and storing tissue. It creates mass, stores water with a solution of nutrients and carries out a complex process of photosynthesis.

Absorption and movement of substances - these functions of the leaf of the plant provide conductive tissues. They are represented by xylem, according to the vessels and tracheids of which there is an ascending current. Another of its kind is phloem, responsible for the opposite current of substances - the descending one. After all, the sugars formed in leaves due to solar energy are needed for all organs of the plant, including the root.

Since such a complex organ as the sheet of the function of carrying out substances carries out the opposite, the elements of its conducting system are assembled into bundles.

These structures are covered with elements of mechanical tissues and together form vascular fibrous bundles. Simply they are called veins.

Due to this structure, the conductive bundles in the leaves perform the function of the movement of substances, as well as the supporting and mechanical.

Venation

Such conductive bundles are visible to the naked eye. On the leaf plate they form a unique unique pattern like the fingerprints of a man. Here is another function of the bundles in the leaves.

There are several types of venation. The mesh is easy to determine by the presence of the main vein, from which the smaller ones leave, forming a reticulum. Surely everyone saw such an image on the leaves of plum, apricot or cherry.

Lily and wheat have thin leaves, veins on which are located next to each other. This type is called parallel. But the veins of the leaves of the lily-of-the-valley are like arcs - this is the arc venation.

Regardless of the type of arrangement, the conductive bundles in the leaves function, without which the life of plants would be simply impossible.

Types of leaves

The leaves are also classified according to the number of leaf blades. Simple called leaves with a single plate. Peach, cherry plum, maple, medinitsa are examples of plants with simple leaves. Complex leaves have acacia, walnut, alfalfa. They consist of several leaf blades attached to one petiole.

What is the sheet function?

With the help of leaves, vegetative reproduction is possible. Its essence lies in the separation from the whole organism of its multicellular part. At home, so you can multiply the violet or zigokaktus.

Important for plants and transpiration is the process of evaporation of water. If it does not occur, the plant organism will die. Since the temperature of the internal environment of all representatives of the vegetable kingdom depends on the temperature of the environment, they can simply overheat.

The leaves of some plants are capable of mutating. Thus, the pea-bean tendrils ensure its firm attachment to the support, the cactus spines protect against excessive loss of moisture, the fleshy leaves of aloe provide a supply of water with nutrients.

Green leaf: functions of planetary significance

The next functions of the sheet are two reverse processes - photosynthesis and respiration.

Breathing is the process of absorbing oxygen and releasing carbon dioxide. It is a necessary condition for the existence of all living organisms and is characteristic of representatives of virtually all kingdoms of living nature.

Photosynthesis - the process of formation of organic substances from inorganic due to the energy of light. This process can only occur in the leaves, as they contain the green pigment chlorophyll. It requires carbon dioxide, which is released in sufficient quantities during breathing. And as a result of photosynthesis, a carbohydrate of glucose and oxygen is formed.

Without exaggeration, we can agree that the green leaf is a real factory that produces not just chemical substances, but also provides all living things on our planet with the necessary conditions for life.