Features of the structure of the conductive tissues of plants.

Like in animals, plants have separate transport mechanisms that are responsible for the delivery of nutrients to individual cells and tissues.Today we will discuss the structural features of the conducting tissue of plants.

What is it?

conductive fabric are those on which there is fluid movement of nutrients necessary for the growth and development of the plant organism.The reason for their appearance is the output of the first plants on land.From the root to the leaves, it is not hard to guess moves upward flow solutions of salts and other nutrients.Accordingly, the downward current flows in the opposite direction.

Rising transport is carried out by vessels in the woody tissue (xylem), descending the delivery - with the help of sieve structures in the inner bark bark (phloem).In general, the shape resembles that of Xylem vessels animals.Cells of elongated, oblong shape are expressed.What else are the structural features of the conducting tissues of plants?

What are they?

should know that there are primary and secondary tissue type.Let's give them a standard classification, as visibility improves its absorption of the material.So, here is a simple structure of the conducting tissues of plants presented in tabular form.

As you can understand, xylem and phloem are a complex species, since due to its heterogeneous structure and can perform such a wide range of functions.

As you can see, the structure of the conducting tissues of plants some supernatural complexity is no different.Anyway, it is much easier than that of cells of higher mammals.

Xylem.Conductive elements

most ancient elements of the system are all conducting tracheids.So called cell specific shape with distinctive, pointed ends.It is up to them subsequently occurred conventional wood fiber fabric.They have substantially stiff wall thickness.Form tracheids can be very different:

• annular.
• spiral.
• in the form of points.
• spore.

Note that passing nutrient solutions are filtered through multiple pores, and therefore their movement speed is quite low.These important structural features of the conducting tissues of plants are often forgotten.

have any plant can meet the structural element?

tracheids can be found in almost all higher sporophytes.Lower gymnosperms mostly also have in their structure these structural elements, even they have played a very important role.The fact that the strong walls of tracheids, which we have already mentioned above, allow them to carry out not only directly conducting function, but also be a support, a mechanical structure.This is - the most important structural features of the conducting tissue of plants, from which depends very much.

often when they are the only support structure, which gives the body the necessary strength to the plant.Curiously, all (!) Of conifers in the wood is completely absent any special mechanical tissue, and the strength provided solely by us tracheids discussed.The length of these amazing conductive elements can range from a few millimeters to a couple of centimeters.

In general, studies of these structural features of the conducting tissues of plants 5 class any secondary school, but often the question of the longest vessels in plants baffled even the students of biological faculties.

Feature vessels

These are highly characteristic element in the xylem of angiosperms.To look like a long, hollow tube.Each of them is formed by the confluence of elongated cells on a "joint to joint."Segments of each vessel is called a cell, which is its functional structure repeats for such tracheids.Note, however, that the segments are much wider and shorter than them.

Which category students should know the structural features of the conductive tissues of plants?5 class, which began to pass botany and structure of the plant organism, can already be guided in the most simple questions on this topic.

The formation of blood vessels

That xylem, which first appears in the process of development of the plant, called the primary.Her tab occurs in the roots and the tops of young shoots.In this case, the segments are separated by the xylem vessels grow on the distal ends of the strands prokambialnyh.Vessel itself appears after the merger, due to the destruction of interior partitions.You can see this if you look at them under a microscope section: stored inside the rims, which are just the same and are the remnants of the destroyed walls.

Let us remember, thanks to some structural elements form the conductive tissue of plants, and some of them are at the root of the plant:

• Epidermal shell.
• bark.
• Protoderma that constantly updates the layers lying above.
• apical meristem, which is the main area of ​​root growth of plants.
• from damage more delicate fabric protects the root cap.
• located inside the root tissue familiar to us: xylem and phloem.
• They are formed, respectively, and protofloemy protoksilemy.
• Endodermis.

Protoksilema (ie the first image in the plant vessels) appears at the very top of all young axial organs.Education takes place directly beneath the meristem, that is where the blood vessels surrounding the cells continue to actively grow and stretch.It should be noted that even mature vessels protoksilemy did not lose their ability to stretch, since their walls are not yet undergone Woodiness.

Typically, conductive fabric flowering plants such seal exposed early enough, because the stem is required to maintain a sufficiently massive and fragile flower.

Recall that is responsible for the hardening process?Lignin.And he was just the same is deposited in the walls of the "blanks" vessels or in a spiral or in the annular direction.This situation does not interfere with its layers of the vessel to stretch.At the same time, the lignin provides quite a decent strength of blood vessels in young plants, which prevents their destruction by mechanical action.

That is why it is important conducting tissue of plants.Figure, which is available on the pages of this article will certainly help you to better understand this question, because clearly shows the main components of the said fabric.

Education metaxylem

In the process of growth, new vessels, which are subjected to the process much earlier woodiness.When does their formation in mature parts of the plant, completing the process of growth metaxylem.How should consider high-school biology structure of the conductive tissues of plants?Class 5, is generally limited only by the fact that plant tissue-existing vessels.Further study is included in the curriculum of the older students.

At the same time the first vessel formed from protoksilemy first stretched and then completely destroyed.Mature same structural formations that emerged from metaxylem to elongation and growth are not capable in principle.In fact, it is dead, it is very hard and hollow tubes.

It is easy to think about the feasibility of the biological course of the process in this direction.If these vessels appear immediately, they would greatly hinder the formation of the surrounding tissues.Like tracheids, vascular wall thickening can be divided into the following groups (depending on their form):

• Annular.
• Spiral.
• Ladder form.
• Net.
• porous.

Please note that long, hollow tubes of xylem that have sufficient mechanical strength - ideal system for the delivery of water and mineral salt solutions over long distances.The movement of fluid in their cavities nothing difficult, the loss of water and nutrients, virtually none.What are some features of the structure of the conducting tissues of plants?Biology (6th grade secondary educational institutions) is also considering the mutual conductance walls xylitol.Let us explain.

Being similar in this respect to tracheids, xylem permit flow of water through the pores in the walls.Since they have a lot of lignin, they have high mechanical strength, and therefore is not deformed, moreover, there is practically no risk of rupture of the nutrient liquid under pressure.However, we have already talked about the supreme importance of the distinctive features of xylitol, due to which many species of timber trees is characterized by high strength and elasticity.

It is strong and simultaneously elastic xylem owe their strength ancient ships.The quiet, but strong conductive fabric plants provide high resistance long pine poles that rarely broke even in the most severe storms.

conductive structures phloem

Consider the conductive material, which are available in the phloem tissues.

Firstly, sieve structure.The material they arise procambium is localized in the primary phloem.Note that with the growth of the surrounding tissue is stretched protofloema quickly, then dies of its structures and completely stops functioning.Metafloema completes its maturing after (!) Of how plant growth ceases.

Other features

So what else should I know the structural features of the conducting tissues of plants?7 class of secondary school must study, in addition to all the above, even sieve structure and characteristics, as well as their cell companions.Let us write out the matter a little more detail.

particularly characteristic structure have segments sieve structures.Firstly, they are extremely thin cell walls, which include a lot of cellulose and pectin.That they strongly resemble the cells of the parenchyma.Important!Unlike the latter, during the maturation of these cells die off completely the nucleus and the cytoplasm, "shrink", is thinly spread over the inside of the cell membrane.Oddly enough, but they are still alive, but depending on the cell companions (reminiscent of the relationship of neurons and astrocytes in the brain of animals).

course, these structural features of the plant conductive tissue Grade 6 are not usually considered, but they are useful to know.At least in order to represent the essence of the processes occurring in the plant body.

sieve tubes and companion cells

so.Segments sieve structures form one, being closely linked.The cell-companion is unique in its cytoplasm she her extremely thick, contains a large number of mitochondria and ribosomes.You might guess that they provide not only the power of the "companion", but also the sieve segment.If the cell-satellite for some reason dies perishes and the entire structure, which is associated with it.

sieve tubes themselves are easily distinguished by their composition available in the sieve plates.Even when using a weak light microscope can observe them easily.There is it in a place where joint end formed the ends of two segments.It is logical that these records are exactly in the course of the growth of most of these segments.

types of vascular bundles

Is there still some structural features of the conducting tissues of plants?Biologists believe those are some aspects of the structure of vascular bundles, which we briefly describe.

In any higher plants can be found mentioned structure.They are a specific type of bands, located at the roots, young shoots, and other parts that are constantly growing.The structure of these bundles include vessels already discussed earlier mechanical support elements.Each structural unit consists of two parts:

• wood department.It consists of vessels and stiff fibers.
• bast site.It consists of sieve structure and bast fibers.

Very often, around the bundle forms a protective layer that consists of live or dead parenchyma cells.In addition, their structure, they are divided into two types:

• Full - xylem and phloem contain.
• Incomplete - in their structure includes only one of these tissues.

Classification of vascular bundles of Lot's

Nowadays quite common is the standard classification of lots that divides the vascular bundles in the following varieties:

• Closed, collateral type.
• Closed, bikollateralnoy species.
• concentric type - located outside the xylem.
• variation of the previous species in which xylem - inside.
• radial beams.

In general, it is almost all the information you need to know when studying conducting tissues of the plant as part of the school curriculum.