evolution of flora and fauna gradually led to the complication of their organization.Therefore, the current species diversity is so great that simply defies the imagination.The increasing complexity of the internal structure was reflected in each evolutionary branch.
This is especially affected plants that have managed to transform itself from the lower species to the submarine settled around the globe the highest representatives with complex internal and external structure.A major role in this was played by the development of special structures - the tissues that make up the bulk of the animals of the kingdom.
meristem: the definition of the concept of
Total There are five main types of tissues of plant organisms.Among them are the following:
- meristem, or educational fabric;
- is stored;
- conductive;
- mechanical;
- basic.
Each of them has a special structure, different types of cells and performs a crucial function in the life of the plant.Of particular note is the educational fabric, in fact it gives rise to virtually everything else and provides the main distinguishing feature of plants from other organisms - unlimited growth throughout life.
If you give a more accurate biological definition of this type of fabric, it will sound like this: educational fabric, or the meristem - a common name of a particular type of tissue, which consist of active lifelong cells are constantly dividing and ensuring growth and development of plantswhole.
Furthermore, it meristems give rise to many other types of tissues in the body.For example, mechanical, conductive coating and others.Through them comes the healing of wounded areas on the body of the plant, quick recovery of lost structures (leaves, pieces of stem, root).It's safe to say that the educational fabric - one of the most important, which allows plants to exist.Therefore, its structure and functions of a closer look.
Cells educational fabric.General information
There are two main types of cells that make up the meristem:
- polygonal or izodiametricheskie.They contain a very large core, which occupies almost the entire interior.Have ribosomes, mitochondria, small cytoplasmic vacuoles scattered throughout.The shell is thin enough.Between themselves, rather loosely arranged.These cells form eumeristemy.They give rise to all tissue types except conductive.
- Prozenhimnye cells.They have, on the contrary, very large vacuoles filled with cell sap.Are connected to each other more tightly, the form of elongated, cubic or prismatic.Educational fabric constructed of them gives rise to the conduction system, Kambia and procambium plants.
Thus, depending on the type of cells that form the tissue to define and execute its function.
You can also select two types of cells meristems:
- an initial - actively dividing throughout the life of the cell, providing the accumulation of the total mass of the educational fabric.They also give rise to another group.
- derivatives cells - may be different from the previous shape, size, number of vacuoles and other parameters.
These types of structures in some species of plants can generally be indistinguishable, at least morphologically.
In general, the educational structure of the fabric allows you to select several types that make up its classification.
Classification of meristems
framework can be put in a number of different symptoms.The first of them - this cell morphology of the tissue.In this particular distinction:
- plate meristem - a cube-shaped cells with a single-layer membrane, forming a coating fabric;
- columnar educational fabric - form the core of the stems and trunks of trees, prismatic cells with a dense shell;
- massive meristem - give rise to a buildup in thickness, are represented by polygonal cells.
following signs for classification - is the ability to differentiate into other structures.On this basis all the meristem can be divided into six groups:
- educational embryonic tissue.Its name speaks for itself.Generates primary embryonic tissue.
- apical meristem, also known as apical.Images: procambium, epidermis, conductive tissue parenchyma.
- Wound educational fabric.Formed at the injury site and provide rapid recovery of lost body or delaying injured.
- intercalary - gusset ensure the growth of plants in height and width.
- side or lateral - provide thickening axial structures of the body due to deposits or cambium phellogen.
- Marginal meristem - that it forms a canvas sheet.
Last classification, on which you can share all the meristem into two groups - genetic.According to her, they are divided into:
- primary - associated with embryonic and apical tissues;
- secondary - cambium, procambium and others.
obvious that the various features of the classification confirms the importance of the structures, especially their role in the life of plants.
lamellar meristem
This educational fabric, function is the formation of the epidermis of the plant.It creates coating plate meristem tissue that protect the body from external influences, maintain a certain form and structure.
Cells plate educational fabric arranged in a row, very intense sharing, and perpendicular to the working body.The result is the outer epidermis of the plant.
columnar tissue
Another name for these tissues - stem.They got his elongated prismatic shape constituting cell structure, which are arranged closely to each other and have a sufficiently thick shell.
columnar tissue gives rise to fully forms the core of the stalks and trunks of plants.Divided into cells of the tissue is also perpendicular to the axial organs.
Massive meristem.Brief description
Features educational tissue called massive that it enables the plant to accumulate a mass of undifferentiated cells that lead to thickening and increased weight.Thus there is a fairly evenly.
In the future, each of the cell mass is converted into one or another fabric that is specialized and will perform its function.So formed, for example, sporangium, and other tissues.
Options educational plant tissue
role played by the meristem, is enormous.You can designate some basic most important functions performed by the tissue under consideration:
- provides plants with unlimited growth throughout life.
- give rise to differentiation and specialization of all other types of tissue in the body.
- ensure the normal development of plants.
- repair damage and restore lost structure.
However, the main function performed by the educational fabric - a multiple cell division and accumulation of a large mass to be able to use a permanent part of the plant and thus maintain its growth and activity throughout life.For this reason, in animals and humans have similar tissue.After all, they grow only up to a genetically determined (originally incorporated in the genome) sizes.
apical meristem
This educational fabric, function and structure of which we consider to be one of the most important of all kinds of meristems.To do this, there are a number of reasons.
- It is also called the apical tissue and apical, since after the development of the embryo, it remains in the growing point (apex of the shoot).
- apical meristem allows stems and roots grow in length.
- Eventually apical tissue is transformed into an inflorescence meristem floralnuyu and allowing to form flowers with all its parts.
- gives rise to all other types of educational tissues.
why we are talking about a high degree of importance of apical meristem in plant life.
have the variety of fabric has several derivatives that it forms in the body of the plant.They are as follows:
- the covering fabric;
- protoderma;
- procambium;
- conductive fabric;
- basic;
- massive.
Along with apical go for value and lateral or lateral meristem.They give rise to Kambia and fellogenu, form the so-called annual rings, which are clearly visible in cross sections of stems and trunks.
primary education fabric
These include those that are first laid in the body of the embryo.First of all, it is the embryo meristem and apical (apical).Some of them are preserved for life, while others die, forming the primary body of the plant.
apical meristems Since we have already discussed in more detail above, there is no need to repeat everything again.Primary tissue - this is the apical educational structures.
Secondary meristem
This group includes massive meristem, which allows the plant at later stages of development to build mass.This educational tissue whose function is primarily in the formation of nodules of axial organs of plants.
special role to play, and the cambium phellogen.The most common effect of secondary meristem come after the end of the apical growth of the plant, but there are exceptions.As an example, in the case of the cambium.
the importance of wound meristem, which lead to the formation of callus - cell mass.They tightened a place of injury or damage to the plant.
