The escape - This is the above-ground vegetative part of the plant. It consists of an axial part - a stem on which leaves and buds are located. On some shoots, generative organs - flowers - can also be placed. It has a more complex structure than the root.

On the stem of the shoot, nodes and internodes can be distinguished. Knot - this is the place of attachment of one or more leaves to the stem. Internodes is the distance between two adjacent nodes. Between the stem and the leaf there is an upper corner called leaf sinus . The buds are located at the top of the shoot and in the leaf axils.

Shoots, depending on the degree of elongation of the internodes, can be shortened or elongated. Shortened shoots actually consist of one node. On shortened shoots of herbaceous plants (dandelion, carrots, beets, etc.), the leaves are located close to one another and form a basal rosette.

Herbaceous plants are divided into annuals, biennials and perennials. Annuals develop and grow over one year (one growing season). In the first year of life, biennial plants (carrots, radishes, beets, etc.) form vegetative organs, accumulate nutrients, and in the second year they bloom, produce fruits and seeds. perennial plants live three or more years. Woody plants are perennials.

kidneys

kidneys - these are embryonic shoots with very short internodes. They arose later than the stem and leaves. Thanks to the kidneys, branching of the shoots occurs.

According to the location of the kidney, there are apical - located at the top of the shoot, and lateral or axillary -located in leaf axils. The apical bud provides the growth of the shoot, lateral shoots are formed from the lateral buds, which provide branching.

Buds are vegetative (leaf), generative (flower) and mixed. From vegetatively th buds develop shoot with leaves. From generative - shoot with a flower or inflorescence. The flower buds are always larger than the leaf buds and have a rounded shape. From mixed buds develop shoots with leaves and flowers or inflorescences. Buds that are laid on any other part of the stem, as well as on roots or leaves, are called adnexal , or adventitious . They develop from internal tissues, provide vegetative restoration and vegetative propagation.

By the presence of scales, the kidneys are closed (if there are scales) and open (naked if there are no scales). Closed buds are characteristic mainly for plants of the cold and temperate zones. The scales of the kidneys are dense, leathery, may be covered with cuticles or resinous substances.

Most buds develop in plants every year. Buds that may not re-grow shoots for several years (even a lifetime), but remain alive, are called sleeping . Such buds resume the growth of shoots when the apical bud, trunk or branch is damaged. Typical for trees, bushes and a number of perennial herbs. By origin, they can be axillary or adnexal.

The internal structure of the kidney

Outside, the kidney may be covered with brown, gray or brown keratinized scales - modified leaves. The axial part of the vegetative bud is the germinal stem. It has germ leaves and buds. All parts together make germ shoot . The apex of the embryonic shoot is growth cone . The cells of the growth cone divide and ensure the growth of the shoot in length. Due to uneven growth, the outer leaf primordia are directed upwards and towards the center of the bud, bent over the inner leaf primordia and the growth cone, and cover them.

Inside the flower (generative) buds on the germinal shoot is the germinal flower, or inflorescence.

When a shoot grows from a kidney, its scales fall off, and scars remain in their place. They determine the length of the annual increments of the shoot.

Stem

Stem is the axial vegetative organ of plants. The main functions of the stem: provides the interconnection of plant organs among themselves, transports various substances, forms and bears leaves and flowers. Additional stem features: photosynthesis, accumulation of substances, vegetative reproduction, storage of water. They vary greatly in size (for example, eucalyptus trees up to 140-155 m high).

The flow of substances in the stem occurs in two directions: from the leaves to the root (descending current) - organic substances and from the root to the leaves (ascending current) - water and mainly mineral substances. Nutrients move along the core rays from the core to the cortex in a horizontal direction.

The shoot can branch, that is, form side shoots from vegetative buds on the main stem. The main stem of a branched plant is called the axis first order . The lateral stems that developed from its axillary buds are called axes. second order . Axes form on them. third order and so on. Up to 10 such axes can develop on a tree.

When branching, trees form a crown. Crown - this is a collection of all above-ground shoots of trees located above the beginning of the branching of the trunk. The youngest branches in the crown are the branches of the last order. The crowns have different shapes: pyramidal (poplar), rounded (spherical) (acutifolia maple), columnar (cypress), flat (some pines), etc. A person forms the crown of cultivated plants. In nature, the formation of the crown depends on the place where the tree grows.

The branching of the stem of the bushes begins at the very surface of the soil, so many side shoots are formed (rose hips, currants, gooseberries, etc.). In semi-shrubs (wormwood), the stems become stiff only in the lower perennial part, from which annual herbaceous shoots grow every year.

In some herbaceous plants (wheat, barley, etc.), shoots grow from underground shoots or from the lowest stem buds - this branching is called tillering .

The stem that carries a flower or one inflorescence is called an arrow (in primrose, onion).

According to the location of the stem in space, they distinguish: erect (poplar, maple, thistle, etc.), creeping (clover), curly (birch, hops, beans) and clinging (step white). Plants with climbing shoots are combined into a group creeper . Creeping stems with long internodes are called mustache , and with shortened ones - whips . Both mustaches and whips are above ground stolons . A shoot that spreads along the ground but does not take root is called creeping (knotweed).

According to the state of the stem, they distinguish herbaceous stems (thistle, sunflower) and woody (beech, oak, lilac).

According to the shape of the stem on a transverse section, they are distinguished: rounded (birch, poplar, etc.), ribbed (valerian), trihedral (sedge), tetrahedral (mint, lip flowers), polyhedral (umbrella, most cacti), flattened, or flat ( prickly pear), etc.

By pubescence, they are smooth and pubescent.

The internal structure of the stem

On the example of a woody stem of dicotyledonous plants. There are: periderm, bark, cambium, wood and pith.

The epidermis functions for a short time and exfoliates. It replaces periderm , consisting of cork, cork cambium (phellogen) and phelloderm. Outside, the stem is covered with integumentary tissue - cork which is made up of dead cells. Performs a protective function - protects the plant from damage, from excessive evaporation of water. Cork is formed from a layer of cells - phellogen, which lies under it. Phelloderm is the inner layer. Exchange with the external environment occurs through lenticels. They are formed by large cells of the main tissue with large intercellular spaces.

Bark

Distinguish between primary and secondary. The primary is located under the periderm and consists of the colenchyma (mechanical tissue) and the parenchyma of the primary cortex.

Secondary bark or bast

It is represented by conductive tissue - sieve tubes, mechanical tissue - bast fibers, the main one - bast parenchyma. A layer of bast fibers forms a hard bast, other tissues - soft.

Cambium

Cambium(from lat. cambio- change). Located under the bark. This is an educational tissue that looks like a thin ring in a cross section. Outside, cambial cells form bast cells, inside - wood. Wood cells, as a rule, are formed much more. Thanks to the cambium, the stem grows in thickness.

Wood

It consists of conductive tissue - vessels or tracheids, mechanical - wood fibers, the main - wood parenchyma. The length of the vessels can reach 10 cm (sometimes - several meters).

Core

Occupies a central position in the trunk. It consists of thin-walled cells of the main tissue, large in size. The outer layer is represented by living cells, the central part is predominantly dead. In the central part of the stem, a cavity can be obtained - a hollow. Nutrients are stored in living cells. From the core to the bark through the wood passes a series of core cells called core rays. They provide horizontal movement of various connections. Core cells can be filled with metabolic products, air.

Stem modifications

Stems can perform additional functions associated with their modification. Changes occur in the process of evolution.

tendrils

These are curly, long, thin stems with reduced leaves that wrap around various supports. They support the stem in a certain position. Characteristic for grapes, pumpkins, melons, cucumbers, etc.

spines

These are shortened shoots without leaves. They are located in the axils of the leaves and correspond to the lateral axils or are formed from dormant buds on stolons (gleditsia). They protect the plant from being eaten by animals. Stem spines are characteristic for wild pear, plum, blackthorn, sea buckthorn, etc.

Tree ring formation

In trees that live in climates with seasonal changes, growth rings- on the transverse section, there is an alternation of dark and light concentric rings. From them you can determine the age of the plant.

During the growing season of the plant, one annual ring is formed. Light rings are rings of wood with large thin-walled cells, vessels (tracheids) of large diameter, which are formed in spring and during active cell division of the cambium. In summer, the cells are slightly smaller and have thicker cell walls of the conductive tissue. Dark rings are obtained in autumn. Wood cells are small, thick-walled, have more mechanical tissue. Dark rings function more like a mechanical tissue, light ones - as a conductive one. In winter, cambial cells do not divide. The transition in the rings is gradual - from spring to autumn wood, sharply marked - during the transition from autumn to spring. In spring, the activity of the cambium resumes and a new annual ring is formed.

The thickness of annual rings depends on the climatic conditions in a given season. If the conditions were favorable, the light rings are wide.

Annual rings are invisible in tropical plants, as they grow almost evenly throughout the year.

ESCAPE AND ESCAPE SYSTEM

General characteristics of the shoot and kidney

escape called a stem with leaves and buds. In a narrower sense, a shoot is understood as an annual unbranched stem with leaves and buds, developed from a bud or seed. It is one of the main organs of higher plants. The shoot develops from the bud of the embryo, or axillary bud. Thus, the kidney is a rudimentary shoot. The function of the shoot is to feed the plant with air. A modified shoot - in the form of a flower (or a spore-bearing shoot) - performs the function of reproduction.

The main organs of the shoot are the stem and leaves, which are formed from the meristem of the growth cone and have a single conducting system (Fig. 3.20). The part of the stem from which the leaf (or leaves) extends is called knot, and the distance between nodes is internode. Depending on the length of the internode, each repeated node with an internode is called metamer. As a rule, there are many metameres along the shoot axis; the escape consists of a series of metameres. Depending on the length of the internodes, the shoots are elongated (in most woody plants) and shortened (for example, in an apple tree). In such herbaceous plants as dandelion, strawberry, plantain, shortened shoots are presented in the form of a rosette.

stem called the organ, which is the axis of the shoot and bearing leaves, buds and flowers. The main functions of the stem are supporting, conducting, storing; in addition, it is an organ of vegetative reproduction. The stem is the link between roots and leaves. In some plants, only the stem performs the function of photosynthesis (horsetail, cactus). The main external feature that distinguishes the shoot from the root is the presence of leaves.

Sheet- a flat lateral organ extending from the stem and having limited growth. The main functions of the sheet:

Photosynthesis;

Gas exchange;

Transpiration.

The angle between the leaf and the overlying portion of the stem is called the leaf axil.

Bud- rudimentary, but not yet developed shoot. Various signs are put in the classification of the kidneys. According to the composition and functions, vegetative, vegetative-generative (mixed) and generative buds are distinguished. Vegetative a bud consists of a stem cone, leaf buds, bud buds, and bud scales. AT mixed a number of metameres are laid in the buds, and the cone of growth is transformed into a rudimentary flower or inflorescence. generative, or floral, buds have only an inflorescence rudiment (cherry) or a single flower.

By the presence of protective scales, the kidneys are closed and open. Closed the buds have covering scales that protect them from desiccation and fluctuations in ambient temperatures (in most plants of our latitudes). Closed kidneys can fall into a dormant state for the winter, which is why they are also called wintering. open kidneys - bare, without protective scales. Their growth cone is protected by the primordia of the middle leaves (in the brittle buckthorn, tree species of the tropics and subtropics, aquatic flowering plants). The buds from which shoots form in spring are called buds. renewal.

By location on the stem, the buds are apical and lateral (axillary). Due apical kidneys, the main shoot grows in length, and due to lateral kidneys - branching of the shoot. If the apical bud dies, the lateral bud starts growing. The generative apical bud, once the apical flower or inflorescence has unfolded, is no longer capable of apical growth.

axillary buds are laid in the axils of the leaves and give lateral shoots of the following order. The axillary buds have the same structure as the apical buds. The cone of growth is represented by the primary meristem, protected by rudimentary leaflets, in the axils of which lie the axillary buds. Many axillary buds are at rest, so they are also called sleeping(or eyes). When the apical buds are damaged (by animals, during freezing or pruning), dormant buds start growing, giving, for example, tops, which are called water shoots in gardening. They are usually removed because they take a lot of nutrients.

Adnexal buds usually develop on the roots. In woody and shrubby plants, root shoots arise from them.

Deployment of the escape from the kidney

The first shoot of the plant is formed when the seed germinates from the germinal shoot. it main escape or escape first order. All subsequent metameres of the main shoot are formed from the germinal bud. From the lateral axillary buds of the main shoot, lateral shoots of the second, and later on, of the third order. This is how the system of shoots is formed (the main and side shoots of the second and subsequent orders).

The transformation of a bud into a shoot begins with the opening of the bud, the appearance of leaves and the growth of internodes. Kidney scales quickly dry up and fall off at the beginning of the deployment of the kidney. At the base of the shoot, they often leave scars - the so-called kidney rings, which are clearly visible in many trees and shrubs. By the number of kidney rings, you can calculate the age of the branch. Shoots that grow from buds in one growing season are called annual runaways, or annual growth.

A number of meristems are involved in the growth of the shoot in length and thickness. Growth in length occurs due to the apical and intercalary meristems, and in thickness- due to lateral meristems (cambia and phellogen). At the initial stages of development, the primary anatomical structure of the stem is formed, which is preserved in monocots throughout their life. In woody dicots and gymnosperms, as a result of the activity of secondary educational tissues, the secondary structure of the stem is formed quite quickly from the primary structure.

leaf arrangement

leaf arrangement,phyllotaxis - the order of placement of leaves on the axis of the shoot. There are several options for leaf arrangement:

next, or spiral,- there is one leaf at each node, and the bases of successive leaves can be connected by a conditional spiral line (birch, oak, apple tree, pea);

opposite- on each node two sheets (maple) are attached against each other;

cross opposite- a kind of opposite, when the oppositely located leaves of one node are in the mutually perpendicular plane of another node (laminate, clove);

whorled- three or more leaves depart from each node (crow's eye, anemone).

The nature of the branching of the shoot

branching shoot in plants, this is the formation of a system of axes, which is necessary to increase the area of ​​​​contact with the environment - water, air and soil.

There are the following types of branching of the shoot:

monopodial- for a long time, shoot growth is maintained due to the apical meristem (spruce);

sympodial- every year the apical bud dies, and the growth of the shoot continues due to the nearest lateral bud (birch);

false dichotomous(with opposite leaf arrangement, sympodial variant) - the apical bud dies off, and growth occurs due to the two nearest lateral buds located below the apex (maple);

dichotomous (apical)- the cone of growth of the apical bud (apex) is divided in two (moss, marchantia, etc.).

Direction of shoot growth. Shoots growing vertically, perpendicular to the surface of the earth, are called orthotropic. Horizontally growing shoots are called plagiotropic. The direction of growth may change during shoot development.

Depending on the position in space, morphological types of shoots are distinguished:

upright– when, in most cases, the main shoot retains orthotropic growth;

rising- when, in the hypocotyl part, it develops in a horizontal direction, and then grows upwards, like an erect one;

creeping- grows in a horizontal direction, parallel to the surface of the earth;

creeping (mustache)- if there are axillary buds on the creeping stem that take root, adventitious roots (tradescantia) or stolon mustaches are formed in the nodes of such shoots, ending with a rosette and giving rise to daughter plants (strawberries);

curly- wraps around an additional support, since mechanical tissues (bindweed) are poorly developed in it;

clinging- grows in the same way as curly, around an additional support, but with the help of special devices - antennae (a modified part of a complex sheet).

And kidneys. This is the main part of the plant, consisting of nodes and internodes, which grows in length due to the apical and intercalated meristems (educational tissue). The stem performs a variety of functions: conducting aqueous solutions from the root to the leaves and vice versa; increasing the surface of the plant by branching; formation of leaves and flowers; accumulation of nutrients; vegetative; support The place of attachment of leaves and buds to the stem is called a node. The section of the stem located between the nodes is called the internode. The kidney is a rudimentary shoot. It contains a cone of growth of the stem and rudimentary leaves, as well as kidney scales covering the educational tissue.

By location on escape There are apical buds, due to which the stem is lengthened, axillary, adnexal. According to the function of the kidney, there are:

a) vegetative - consist of an adventitious stem, scales, rudimentary leaves and a growth cone
b) generative - consist of a rudimentary stem, scales and the rudiment of a flower or inflorescence.

Any the escape develops from the kidney due to the division of the meristem in the growth cone. Most plants are apical.

Internal: on the cut surface, a bark is distinguished, consisting of cork and bast. Deeper is the wood - the main fabric, in the center - a loose core.

Between the bark and the wood is the cambium, an educational tissue on which the thickening of the stem depends.
Thanks to the division of cambial cells, the stems of trees, shrubs and perennial grasses grow in thickness. All layers of wood cells formed in spring, summer and autumn make up the annual growth ring. By counting the number of annual rings, you can determine the age of a cut tree or a cut branch.

Cork protects the deeper cells of the stem from excessive evaporation, from the penetration of atmospheric dust with microorganisms that cause plant diseases.

In the cork, lenticels develop - small tubercles with holes, through which gas exchange takes place. The composition of the bast includes sieve tubes, through which solutions of organic substances move, and thick-walled bast. Wood makes up the bulk of a tree trunk. It is formed by cells of various shapes and sizes. The shells of many cells are thickened and impregnated with a substance that gives them density. The composition of wood includes long tubular vessels. The cambium plays a large role in the life of the stem. Its cells divide, resulting in new layers on both sides of the cambium. Those cells that are deposited towards the bark become new cells of the bast, and the cells deposited by the cambium towards the wood become new cells of the wood. The core consists of large cells with thin membranes. This is where nutrients are stored.

Water with minerals dissolved in it rises through the vessels of wood; root pressure and evaporation of water by leaves are of great importance for raising water. In the bast there are sieve tubes, through which organic substances move from the leaves to other organs of the plant.

Modified shoots are rhizomes (nettle, couch grass, iris), tubers (potatoes, corydalis, Jerusalem artichoke), bulbs (onion, lily, tulip, narcissus).

Escape: functions, structure and diversity

When one or another plant is callednie, then in our imagination fussKakaet is just an escape, because, in fromdifference from the root, the escape is visible,the aerial part of the plant. Any dea roar rising from the earth isrun. Even the most powerful. In naturethere are also underground shoots.Are there plants without flowers?stems, without a stem, but always with a cor him and run away!

escape functions. Main escape function -air supply plants. This process is called photosynthesis . To absorb carbon dioxide (it is only 0.03% in the air) and to capture the sun's rays, the plant needs a large surface, which is provided by the complex structure of the shoot.

Shoots capable of forming adventitious roots, plants can multiply. Flowers appear on some shoots, fruits and seeds ripen.

Escape structure. A shoot consisting of a stem, leaves and buds is called vegetative . If the shoot also bears flowers, it is calledgenerative .

At the top of the shoot, in the apical bud isshoot growth cone (BUT). The tender cells of its educational tissue are protected by young rudimentary leaves. Due to cell division of the apical educational tissue and their growth, the shoot grows in length. In the internodes isinsert educational fabric (B).

Unlike the apical one, the interstitial educational tissue retains the ability to divide cells only during the growth of the internode. In the adult shoot, these cells turn into cells of permanent tissues, after which the growth of the internode in length stops. In some plants, intercalary growth continues for a long time ( wheat, rye, beans ).

Make captions for the drawing "Escape structure". (Interactive task)

Leaf arrangement. For some shoots, only one leaf can depart from the node (linden, maple, geranium ). This arrangement of leaves is called next . If there are two leaves on a node, then the leaves are located opposite (lilac, elderberry, chickweed ). If a node has three or more leaves, then this whorled leaf arrangement ( raven eye, lily ).

Determine how the leaves are arranged. (Interactive task)

biological game

The arrangement of the leaves on the stem ensures that they receive a stream of sunlight. In conditions of insufficient lighting in indoor plants ( balsam, ivy), on the lower branches of trees ( linden, maple) leaf petioles are bent, leaves are displaced, smaller ones fit between large ones.

Leaf mosaic

As a result, all leaves, regardless of the type of leaf arrangement, turn towards the light. Such a phenomenon is calledsheet mosaic .

Escape in a leafless state. In most woody plants, the leaves fall in autumn, and the shoots become leafless. Traces of fallen leaves are clearly visible under each bud. They are calledleaf scars . In place of last year's apical bud remains renal ring .

In winter, trees and shrubs can be easily recognized not only by the shape of the crown, but also by the shape and size of the buds and leaf scars, the color and shape of the stem.

All plants have special characteristics. For example, at alder kidneys sit on special legs. In addition, she has clearly visible earrings and small bumps - fruits. Bud and you covered with a cap. And at buckthorn the kidneys do not have covering scales at all. kidneys mountain ash pubescent. kidneys poplars sticky and resinous. Many plants can be identified by smell. Pleasant, fresh scent poplars, and here at elderberry there is no such smell. You can’t confuse the smell of twigs with anything black currant .

Escape variety. Shoots with well-defined internodes are calledelongated . The internodes do not always elongate (there is no interstitial growth), as a result of which the shoot will consist only of nodes, leaves and buds. Such escapes are called shortened . They are found in both trees and grasses. The short shoots of grasses are called socket (strawberry, dandelion, plantain ).

The shoot emerging from the seedling grows vertically upwards. He - upright (A) (trees and shrubs, as well as many herbaceous plants -rye, bluebell, aster ). But in the future, shoots are formed from its buds, which can grow in different directions. In accordance with the location in space, there are rising (B) (blackhead, carnation grass ), recumbent (bird buckwheat, wood lice ), creeping (D) (hoof, budra, meadow tea ) shoots; creepers: curly (AT) ( bindweed, lemongrass, beans ), clinging (G) (peas, chin, grapes ), climbing (ivy, blackberry).

One type of plant can have different types of shoots. For example, at woodlice there are both rising and lying shoots.

The tips of the elongated shoots during growth make circular movements. In climbing plants, the scope of circular movements is especially large. Having found support, the shoot wraps around it. Interestingly, some types of plants wrap around the support clockwise, while others wrap it counterclockwise. If such an escape does not find support, then its winding stem will fall to the ground. The tendrils of climbing shoots can be formed from a leaf or part of it ( peas, peas), from side shoots ( grape). Blackberry clings to the support with spikes - outgrowths on the stem, and ivy- short adventitious roots. The botanical names of some plant species reflect the structure of their shoots:creeping clover, creeping ranunculus .

Interactive lesson simulator. (Go through all the pages of the lesson and complete all the tasks)

Shoot - a complex organ of a plant, consisting of a stem, buds and leaves. The structure of the shoot ensures the fulfillment of its main function - air supply. Shoots can be not only vegetative, but also generative. The stem part of the shoot consists of nodes and internodes. The nodes contain leaves and buds.

The escape- this is a stem with leaves and buds located on it, formed during one summer:

The main one - developed from the kidney of the seed germ

Lateral - developed from the lateral axillary kidney

Elongated - with elongated internodes (cucumber, tomato)

Shortened - with shortened internodes (radical rosette in radishes, carrots)

Vegetative - bearing leaves and buds

Flower-bearing - bearing reproductive organs (flowers, fruits, seeds)

Bud - a rudimentary shoot, at the top of which there is a growing cone:

apical bud(1) - a bud at the top of the stem, including a growth cone, the reproduction of cells of which ensures the growth of the stem in length

lateral(2) - in the axil of the leaf, lateral shoots are formed from it.

adnexal- outside the sinus (on the stem, root, leaf), gives an adnexal shoot

sheet- consists of a shortened stem with rudimentary leaves and a growth cone

floral- consists of a shortened stem with the beginnings of a flower or inflorescence

mixed- consists of a shortened stem with rudimentary leaves and flowers

kidney renewal- wintering bud of a perennial plant, from which an escape develops

sleeping - dormant for several growing seasons.

4 - leaf scar,

6 - the limit of annual growth,

7 - lentils,

8 - leaf traces (conductive bundles in the leaf, after leaf fall),

9 - annual growth.

Stem - axial vegetative organ of a plant with positive heliotropism, unlimited growth, radial structure, bearing leaves and buds; the part of the shoot that makes the connection between the roots and leaves, bringing the leaves to the light; storing nutrients.

main stem- develops from the bud of the seed embryo.

Increasing cone - a multicellular array of apical educational tissue, which, due to constant cell division, forms all the tissues and organs of the shoot.

The part of the stem from which the leaf (or leaves) extends - node- 5, and the distance between neighboring nodes - internode - 3.

branching shoots - the formation of lateral shoots, due to which the entire above-ground "body" of plants is formed:

apical branching the most simple and ancient, found in different groups of plants - from algae to club mosses. The top of the main axis of the plant branches dichotomously and gives rise to two axes of the following order

lateral branching - lateral axes extend from the main axis of the plant

at monopodial lateral branching, the apical bud is active throughout the life of the plant and the main axis has unlimited apical growth (typical for many gymnosperms and some herbaceous angiosperms)

most angiosperms have sympodial type of branching - the apical bud dies off or stops growing, while the lateral shoots develop intensively, the ground part of the shrubs and tree crowns are formed.

Escape forms:

in the direction of growth: upright, curly, climbing, creeping shoots

according to the degree of lignification: lignified (trees and shrubs) and herbaceous plants.

The structure of the stem of a woody plant - structure, on the cross section of which parts are distinguished:

outside - crust - 1 - a complex of dead tissues that cover tree trunks and protect them from frostbite and water loss. Young (annual) stems are covered on the outside skinned , which is then replaced cork. In woody plants, the outer layers of the bark gradually turn into a crust. Cork- integumentary tissue consisting of several layers of dead cells

bast (bark, phloem) - 2 - a complex of conductive (sieve tubes), mechanical (bast fibers) and basic tissue, located outward from the cambium; to carry carbohydrates from leaves to roots

cambium - 3 - educational tissue, 1 layer of dividing cells; bast cells are deposited outside, wood cells are deposited inside.

wood (xylem) - 4,5 - an annually growing complex of conductive (vessels), mechanical (wood fibers) and basic tissues located inward from the cambium. Annual ring - a layer of wood formed due to the work of the cambium during one summer.

core -6 - the main tissue, located in the center of the stem, performs a storage function. 7 - core beam.

Stem performs functions support, transport, storage of substances, vegetative reproduction of plants and protection of them from being eaten. Stem modifications- tubers, bulbs, rhizomes, spines.

Sheet - lateral vegetative organ growing from the stem, having bilateral symmetry and a growth zone at the base.

Functions :

photosynthesis

gas exchange

transpiration (evaporation)

water storage (aloe, young)

vegetative reproduction (begonia, gloxinia)

Catching insects (sunflower, venus flytrap)

Protection against damage (camel thorn cacti)

Attachment to a support (pea)

4-lateral veins,

5-main

vein (conducting bundle),

6-top of the sheet,

7 notched edge,

8-sheet base

By structure leaf includes lamina-3 and petiole-2.

Without petiole - sedentary leaves.

In some species, at the base of the petiole, they develop stipules(paired leaf-like formations at the base of the leaf, protecting the lateral axillary buds and the intercalated educational tissue of the leaf - the meristem) -1 (apple, linden, rose, pea).

By shape leaves are rounded, lanceolate, swept, etc. Leaves subdivide on the:

simple – from leaf blade and petiole. Simple leaves can be whole(characteristic of many trees) and bladed(the plate is dissected into blades).

complex – several leaf blades on one petiole; can be attached at one point ( palmately complex chestnut, lupine); pinnate leaves (in which leaf blades are attached along the entire length of the petiole). Pinnate leaves are of two types: parotinate(end with a pair of leaf blades, like peas) and pinnate ( one leaf (rowan).

1-stipules,

2-leaves,

3-antennae,

4th axis of the sheet (rachis).

Rachis –

1) the axis of a compound leaf, bearing leaflets, in seed plants and leaf (fronds) of ferns;

2) the axis of a complex ear; the main axis of the reproductive shoot; bed of a basket of Compositae (rarely).

leaf arrangement – the arrangement of leaves on the stem, most conducive to the performance of their function:

regular (1 knot - 1 leaf; apple tree, cucumber)

opposite (1 knot - 2 leaves opposite each other; lilac, carnation)

whorled (1 knot - several leaves; raven eye, lily, horsetail).

leaf structure :

upper epidermis(1) - integumentary tissue on the upper side of the leaf (facing the light), often covered with hairs, cuticles, wax

columnar fabric(2) - the main tissue, its cells are cylindrical, tightly adjacent to each other, on the side of the leaf facing the light, they contain many chloroplasts that carry out photosynthesis.

lower epidermis(4) - integumentary tissue from the underside of the sheet,

usually carries stomata(5), consisting of two guard cells of the epidermis and a gap that opens depending on the magnitude of the turgor pressure in the cells, for gas exchange and transpiration

spongy tissue(3) - the main tissue of cells of irregular shape with intercellular spaces, closer to the underside of the leaf. There are fewer chloroplasts in spongy tissue cells; in addition to the photosynthetic function, this tissue performs the function of gas exchange and water evaporation (through stomata)

6 - vein bast - part of the conductive leaf bundle, consists of sieve tubes

7-wood vein - part of the conductive leaf bundle, consists of vessels

8-main vein (vascular fibrous vascular bundle); leaf veins- a system of conductive bundles that connects the leaf into a single whole, serves as a support for the pulp of the leaf, connects it to the stem. Venation- the order of the veins in the leaf blade:

parallel

mesh

pinnate - the main vein is expressed, lateral ones depart from it

palmate - the main vein is not expressed, there are several large veins and lateral ones.

The mechanism of the stomata.

Stomata (closed - a) have semicircular guard cells (1), between them there is a stomatal gap (2). The side that faces the gap is thicker than the other thin walls. It contains chloroplasts (3) capable of photosynthesis. As a result, carbohydrates accumulate, their concentration increases, respectively, the water concentration decreases, and at this time water begins to flow from the surrounding cells. Since the guard cells of the stomata are differently thickened, they protrude in the direction where the wall is thicker. This is how the stomata open (b), carbon dioxide enters there, oxygen is released, that is, gas exchange occurs.

4-adjacent cells of the skin of the leaf,

5-thickened cell wall,

6-thin cell wall.

The process of evaporation of water by leaves promotes the movement of water and substances dissolved in it from the roots to the leaves, cooling the plant and serving as protection against overheating. The mechanical fabric provides the resilience and elasticity of the sheet.

Leaf modifications:

thorns (cactus, spurge, barberry, white locust)

antennae (peas, vetch)

juicy scales (onion, garlic)

covering scales

trapping devices (venus flytrap, nepenthes, sundew)