The functions and structure of the stem of the plant

Flora - one of the most amazing and unusual wonders of our planet.Plants differ from each other at times as much as they are different to animals.The only thing that unites some of them - stalk.Of course, it is complex and heterogeneous structure, whose functions are very diverse.So in this article we will look at the structure of the stem.

General

This is the main shaft portion of the plant.It attached leaves that are carried on the stem to the light, he received them channels solutions nutrients, water and mineral salts.Be aware that it is there may be delaying nutrients "in reserve".In addition, the structure of a stalk it involves the development of fruit, seed and flower, which serve for reproduction of the plant body.

basic structural units are the node and internode.Node is called the land, which are located directly on the leaves or buds.Thus, between two adjacent nodes located interstice.The space, which is formed between the node and leaf petioles, called the sinus.Accordingly, those buds that are located in this area, called axillary.At the top of the stem there is a growing bud, which is called the apex.

If you step back a little from the main direction of the article, you can tell something interesting.Did you know that the interstices some plants are large enough to have been possible to do even small kegs?Some species of bamboo, of course!This giant grass has such strong stems that are not only doing the dishes, but also excellent rafts.Stems from hollow bamboo, durable, almost do not rot, and that led to the choice of many sailors in ancient times.

Lifetime

Everyone knows that the stems are woody and herbaceous plants differ greatly in life.So, a variety of herbs, which are common in the temperate zone, it does not live more than one season.The stem is woody plants can be kept more than a century.Worldwide known bristlecone pine Prometheus, which grow on the territory of the present United States (index WPN-114).It was cut down in 1964.According to radiocarbon dating, it was the age of ... 4862 years!Even the Christmas tree is met, when he was already in a very "respectable" age!

What other features worth knowing, studying the structure of the stem?The trunk is called the main stem, from shrubs, which have several growth points, such formations are called trunks.Recall that there are several types.Here is the classification of the stems, which was adopted today.

main classification

erect very common species.Immediately reminded of almost all the trees, much of herbs.At the same time the structure of the stem is different well-developed mechanical parts, but not necessarily to its tissues were completely woody.Example - sunflowers, corn, whose trunk is still quite flexible and lively.In cereals the aerial part of the stem is called a culm.Generally, it is hollow inside (except nodal zones).However, hollow species are widespread among melons, umbrella plants, etc.

Some herbs have a creeping stem.Its characteristic feature - the ability to take root node.A perfect example - wild strawberry.

climbs and winding type, which in many ways is a variation of the previous, widely distributed among the vines.Among these plants there are also herbaceous and woody species.They differ in a huge growth rate, thereby reinforcing the mechanical part is simply no time to develop, but because the vine in dire need of support.

Curly, according to its title, entwine basis.It is interesting that some species tendrils wrap around base in a clockwise direction, and in some - in the opposite direction.There are also such plants, the stems of which equally well may be bent in all directions.Unlike them, clinging species climb the pole, vtseplyayas into tiny cracks and bumps on the surface of his mustache (hops, ivy).

most common forms stem

If you take a plant and cut it, to look at the structure of the stem in this case most often will resemble a circle.Of course, nature is not limited to:

• three-sided cut from sedges.
• Tetrahedral from nettles.
• beautiful and incredibly complex polyhedrons cacti.
• Prickly pears are the flattened, almost flat on the kind of cut.
• have a sweet pea plant stem structure resembles a wing.

But do not assume that this diversity can be endless.Needless wide asymmetric stems often arise as a result of any serious anomalies and irregularities in development.Here are the different types of structure stems.

As the stem moves water and mineral salt solutions?

As we know, the plant for normal life have to be provided with water and mineral salt solutions.One of the most important functions of the stem is precisely their transport.If you cut a branch of birch or maple sap flow in the beginning, but this can be easily seen, since the cut surface will drain plenty of sap.

Almost all body plants permeated conductive fabric.Moreover, they are differentiated: Water and aqueous solutions are raised by one, and the organic substances - other channels.In plants, these structures are often permeated by mechanical tissue bundles that provide them the necessary strength.

As the stem moves organic matter?Where they can stock up?

All organic nutrients are deposited in specialized cells that play a role reserving.Actually, it was for the people of these substances and tamed plants: it produces are oils and fats, the most valuable raw material for the chemical, processing and food industry.

Typically, these compounds are deposited in the young shoots, seeds and fruits of plants.We believe that all known potato, sweet potato and peanuts, in which case everything is just so.As for the trees, the organic compound often accumulate in the core.So, it is from this part of certain types of palm extract valuable raw material for the chemical industry (waxes, oils).

What is inside?

The youngest newly grown plants trunks covered with delicate skin first.Subsequently, it is completely replaced by a stopper.Her cells completely die from them remain only an empty "shell" filled the air.Thus, the skin and cork are classified covering tissues, the tube is a multilayer structure.

Contrary to popular opinion, it is formed in the first year life of the plant.With increasing age and increasing the thickness of the cork layer.All of the covering fabric designed by nature to protect the plant body from the adverse effects and the effects of the environment.

must be remembered that all these data are of great importance in some industries.First of all, wood.For example, in the processing of wood should always remember that those parts which prevailed during the life of the tree, young and rapidly dividing cells, it is better not to use.Actually, at the top of the wood discarded for this reason.That's how important biology in everyday life!The structure of the stem is very difficult, but it is necessary to know him.

Thus, these fabrics to prevent excessive evaporation, which is particularly important in areas with severe and hot climate, protect the plant against the ingress of dust and its thickness harmful microorganisms that could cause illness and death of the organism.For the gas exchange surface covering tissues are tiny stomata, through which plants "breathe".

on the tube can be seen as tiny bumps with holes called lenticels.They formed a particularly large cells of the fabric, which differ impressive size of the intercellular space.

Under the cover shell (and not on the surface) is bark, the inner layer is called the phloem.Moreover, the internal structure of the stem includes a sieve structure and companion cells.Besides them, there are special cells which are reserved nutrients.

crustal structure

Bast fibers are stretched in length, with the dead in the development of content and woody walls, performing carrier, the mechanical role.They determine the strength of the stem, its resistance to fracture.Sieve structures - a vertically arranged rows of live cells with disrupted nuclei and cytoplasm, which adheres to the inner shell.Their walls are penetrated through holes.The sieve cells belong to the conducting system of the plant, which forms the water and nutrient solutions.

in the internal structure of the stem cambium is also characterized with long, stretched and flat cells.They actively share in the spring and summer.The main part of the stem is the wood itself.Very similar in structure to the phloem, also formed by cells of different shape and function, which form several tissues (a plurality of conductive structures, mechanical and underlying tissues).Annual tree rings formed by all these cells and tissues.

It studies the structure of the stem Grade 6 in an ordinary secondary school.Unfortunately, the educational program is not so often focuses on the core.But it is formed by large cells with thin walls.They are loosely adjacent to each other, as the game store and funded role.If you've ever seen the core of a tree trunk, you probably remember the "antennae" that diverge from it in different directions.

But they play a vital role!It is for these tyazham that are large clusters of conductive patterns, the nutrients go into the phloem and other parts of the plant organism.To help you better imagined the structure of the stem (dicots as well), we present the basic data in table form.

This table "Structure of the stem" will help you remember the basic components, to understand their functional significance.Oddly enough, but the details of it can be useful in everyday life.

Common features of the anatomical structure of the stem

Now we will examine the anatomical structure of the stem.Oddly enough, but this topic is very often difficult for those students who are studying botany course.In general, if you at least know the general functionality of the various structures of the stalk, then the structure will be able to understand without any special effort.Simply put, the structure and function of the stem are inextricably linked, so they should be examined together.

In conducting tissues developed conductive structures (sieve cells) by which nutrients are delivered to all parts of the plant.The main part of the barrel has a large number of mechanical tissue, are responsible for the strength properties.The young shoots contain a developed system of meristems.

With a conventional light microscope you can see that the apical meristem give rise procambium and gusset meristem.It is through them begins to form the primary structure of the stem.In some plants, it is stored for a long time.Cambium, which is a secondary structure, forms the secondary structure of the stem.

Features primary system

Consider the features of the structure of the stem.Rather, its primary structure.One should distinguish between the central core (stele), and the bark of the primary order.Outside the bark is covered with cloth cover (periderm), and under it there is assimilation tissue (hlorenhima).She has a very important role, as it acts as a kind of bridge between the cortex and mechanical tissues (collenchyma and sclerenchyma).

central core is protected on all sides by a layer of endoderm.Most of this took conductive strands, formed by the merger of the conductive and mechanical tissues, which we just talked about.The core consists of practically specialized parenchyma.Due to the fact that her bad cells adjacent to each other (as repeatedly stated above), it often forms an air cavity, the volume of which can be very significant.

cambium produces secondary xylem and phloem.This is due to the fact that the primary cortex is constantly dies and therefore needs to be replaced, and which provides a cambial tissue.Finally it is worth mentioning that the structure stems largely depends not only on the plant species, but also on the conditions in which they grow.So should study the structure of the stem 6 class.