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, cereals and water lilies - each of these plants is a unique kind of leaves give.
Leaf - side part of the shoot
Escape any plant consists of the axial part -the stem to which the sheet is attached - the lateral part. This arrangement allows the sheet to occupy the most favorable position relative 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 may change theirform together with changing environmental conditions. Everyone knows the shooter in the water has a ribbon-like shape of the leaves. It is necessary that this organ can not damage the strong current 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 are significantly increased.
The sheet consists of a leaf plate and petiole, withthe help of which is attached to the stem. Some leaves lack a petiole, and the place of their attachment is the base of the leaf blade. These leaves are called sedentary.
Each sheet has its own waydismemberment. 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.
The functions of the plant leaf are interrelated withfeatures 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 functionsThe plant leaves are provided with 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 necessary 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 functions of the movement of substances, as well as the supporting and mechanical.
Such conductive bundles are visible to the naked eye. On the sheet plate, they form a special unique pattern like the fingerprints of a person. 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 a 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
Leaves are also classified by numberleaf blades. Simple called leaves with one plate. Peach, cherry plum, maple, lungwort 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 processevaporation 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 oxygen uptake andrelease of carbon dioxide. It is a necessary condition for the existence of all living organisms and is characteristic of representatives of almost all kingdoms of living nature.
Photosynthesis - the process of formation of organicsubstances from inorganic due to the energy of light. This process can only take place 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 greensheet 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.