Structure, functions and types of kidneys. Diversity of buds, development of shoots from the bud

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§ 22. Escape and buds

1. What structure does the seed embryo have? 2. What kind of fabric is called educational?

The escape. The stem with leaves and buds located on it is called escape. The stem is the axial part of the shoot, the leaves are the lateral parts. The areas of the stem where leaves develop are called nodes, and the sections of the stem between the two nearest nodes of one shoot - internodes.

Many plants have two types of shoots: some with long and others with short internodes.

The angle between the leaf and the internode above is called leaf axils.

Leaf arrangement . Most plants have next, or spiral, leaf arrangement, in which the leaves grow one at a node and are arranged alternately on the stem in a spiral. For example, birch and willow have this arrangement of leaves. If the leaves grow two at a node - one leaf against the other, for example in maple, lilac, then this arrangement is called opposite. In plants with whorled Due to the arrangement of the leaves, they develop in threes or more at the nodes, as, for example, in elodea and oleander.

When a seed germinates, a shoot is formed from the bud of the seed embryo. In perennial plants, shoots develop from a bud.

73. Leaf arrangement

74. Apple tree shoots

Kidneys. At the top of the shoot there is usually apical bud, and in the axils of the leaves - axillary buds. Buds that do not develop in the leaf axil (on internodes, leaves, roots) are called subordinate clauses.

The arrangement of axillary buds repeats the arrangement of leaves on the stem. Poplar, cherry, birch, bird cherry, hazel have an alternate arrangement of buds.

The buds are located opposite on the shoots of lilac, elderberry, jasmine, honeysuckle and indoor plants fuchsia, pilea, coleus, which are characterized by the same leaf arrangement.

After the leaves fall, they remain on the shoots leaf scars, above which the axillary buds are located.

Each type of plant is characterized by a certain location of buds on the shoots, their shape, size, color, and pubescence. Based on these and some other signs, you can determine the name of a tree or shrub even in winter.

Kidney structure . On the outside, the buds are covered with dense, leathery bud scales that protect them from exposure to adverse environmental conditions.

Through a magnifying glass, a longitudinal section of the kidney is clearly visible rudimentary stem, at the top of which is cone growth, consisting of cells of educational tissue.

There are very small rudimentary leaves. In the axils of these leaves are rudimentary buds; they are so small that they can only be seen with a magnifying glass. Thus, the kidney is rudimentary shoot.

75. Structure of chestnut buds

Inside some buds on the rudimentary stem there are only rudimentary leaves. Such kidneys are called vegetative, or leafy. Generative, or floral, buds are rudimentary buds or inflorescences; they are larger than vegetative ones and have a more rounded shape.

The structure of the kidneys. Location of buds on the stem

1. Consider the shoots of different plants. Determine how the buds are located on the stem and sketch them.

2. Separate the buds from the shoot and examine their external structure. What adaptations help the kidneys withstand adverse conditions?

3. Cut the vegetative bud lengthwise and examine it under a magnifying glass. Using the drawing, find the scales, rudimentary stem, rudimentary leaves and growth cone. Draw a cross-section of a vegetative bud and label the names of its parts.

4. Study the generative bud. What do vegetative and floral buds have in common and how do they differ? Use the picture for comparison in the textbook.

5. Compare the structure of the bud and shoot. Draw a conclusion.

Growth and development of the shoot. You have established that a bud is a rudimentary shoot that has not yet developed. The development of the shoot begins with the opening of the buds . When the bud scales fall off, intensive shoot growth begins. The shoot lengthens due to the division of cells of the growth cone (educational tissue). Young cells grow, forming new sections of the stem with leaves and buds. As you move away from the apical point of growth, the ability of cells to divide weakens and is soon completely lost. New cells turn into cells of the integumentary, main, mechanical or conductive tissue of the shoot, depending on their location.

76. Development of shoot from the bud

The growth and development of shoots can be controlled. If you remove the apical bud, the shoot stops growing in length, but it begins to develop side shoots. If you cut off the top of a side shoot, it will also stop growing in length and begin to branch.

By pruning shoots, skillful gardeners often give trees and shrubs bizarre, beautiful shapes. It has been established that the longevity and productivity of fruit trees, as well as the quality of the fruit, depend on the shape of the crown.

THE ESCAPE. BUD. Apical, axillary, accessory buds. VEGETATIVE, GENERATIVE KIDNEYS. GROWTH CONE. KNOT. INTERNODE. LEAF AXIS. REGULAR, OPPOSITE, whorled leaf arrangement

1. What is an escape? What parts does it consist of? 2. What types of leaf arrangement do you know? 3. What is a kidney? 4. How are kidneys distinguished? 5. How are the buds located on the shoots? 6. What is the structure of a vegetative bud? 7. How do generative buds differ from vegetative ones? 8. How does the shoot grow in length?

Place a branch of a tree or shrub in the water and watch the development of shoots from the buds. Write down when the branch is placed in the water, when its buds swell, its scales open, a shoot appears and leaves bloom.

In addition to apical growth, most plants experience elongation of shoot internodes due to intercalary growth. For example, in wheat, bamboo and other cereals, intercalary growth occurs as a result of the division and growth of cells located at the bases of all internodes. Thanks to this, the young stems of some plants grow very quickly. For example, bamboo stems can grow more than a meter in a day.

1. Sprout two bean or pea seeds in a pot of soil. When the stems of the plants reach 7-10 cm in height, cut off the top of one of them. Observe what happens to the plants after one to two weeks.

2. Trim the top of your ficus or other indoor plant. Watch the shoots grow.

Try to determine the names of trees and shrubs growing near your home and school by the characteristic features of their buds.

By the location of the buds, their shape, size, color, pubescence and some other characteristics, even in winter we can determine which tree or shrub is in front of us.

The buds are usually located directly on the stem. The exception is alder: its buds sit on special legs. By this characteristic, as well as by the earrings and small cones, alder can be easily distinguished from other trees before the leaves bloom.

Poplar is recognized by its sticky, resinous, pointed buds, which have a peculiar, pleasant odor.

The willow bud is covered with only one cap-like scale.

Buckthorn has no kidney scales at all.

77. Buds on the shoots of various trees and shrubs

The oblong large buds of rowan are pubescent and therefore clearly distinguishable from the buds of other trees .

Bird cherry and black currant buds have a pleasant smell. The oppositely located elderberry buds, on the contrary, have an unpleasant odor. By smelling them, you will immediately distinguish elderberry from other shrubs.

§ 23. External structure of the leaf

1. What vegetative organs are distinguished in a flowering plant? 2. On which organ of a flowering plant are the leaves located? 3. Are the sizes and shapes of leaves the same in different plants?

The leaf is part of the shoot. It performs three main functions - photosynthesis(formation of organic substances), gas exchange and evaporation of water.

Leaf shape. Although the leaves of different plants vary greatly in appearance, there are many similarities between them. Most of the leaves are green in color and consist of two parts: leaf blade And petiole. The petiole connects the leaf blade to the stem. Such leaves are called petiolate. Apple, cherry, maple, and birch have petiolate leaves. The leaves of plants such as aloe, wheat, chicory, flax do not have petioles; they are attached to the stem at the base of the leaf blade. They are called sedentary.

At the base of the petiole, outgrowths sometimes develop - stipules

78. Attaching leaves to stem

The shape of the leaves is round, oval, heart-shaped, needle-shaped, etc. The shape of the edge of the leaf blade is also varied. For example, a leaf of an apple tree has a serrated edge, an aspen leaf has a serrated edge, and a lilac leaf has a whole edge. .

The leaves are simple and compound. Simple leaves consisting of one leaf blade, characteristic of birch, maple, oak, bird cherry and other plants .

Compound Leaves consist of several leaf blades connected to a common petiole by small petioles. These are the leaves of ash, rowan and many others. .

79. Different shapes of leaf edges

80. Simple leaves

81. Leaves are compound

82. Leaf venation

Venation . Leaf blades are pierced in different directions conductive bundles, which are called veins.

The veins not only conduct nutrient solutions, but also give the leaf strength.

If the veins are located parallel to one another, as in many monocotyledonous plants (wheat, rye, barley, onions and some others), such venation is called parallel.

The wider leaves of the lily of the valley and the houseplant aspidistra have arc venation, which is also typical for monocots.

Reticulate venation typical of the leaves of dicotyledonous plants, the veins in them, as a rule, branch repeatedly and form a continuous network. But there are exceptions: for example, the dicot plantain has arcuate venation, and the leaves of the monocot raven's eye plant have reticulate venation.

Leaves are simple and compound, their veining and leaf arrangement

1. Examine the leaves of indoor plants and herbarium specimens. Select simple leaves. On what basis do you select them?

2. Select compound leaves. On what basis are you doing this? What kind of veining does the leaves you selected have?

3. What leaf arrangement do the plants you looked at have?

4. Fill out the table.

LEAF PLATE, PETILE. LEAVES PETOILE AND SESSIONAL. LEAVES SIMPLE AND COMPLEX. VENATION RETICULAR, PARALLEL, ARC

1. What is the external structure of the leaf? 2. Which leaves are called complex and which are simple? 3. How do monocots differ from dicots in leaf venation? 4. What is the function of leaf veins?

Make a herbarium of leaves with different shapes of leaf blades and different veins.

The tropical resident Victoria Amazonica, related to our water lilies, has a leaf so large that a three-year-old child can sit on it, like a raft, and the leaf holds him on the water.

The weed plant chickweed has leaves smaller than a fingernail, but they contain a large amount of vitamins. Therefore, they are useful to give to parrots and other birds in your living area.

§ 24. Cellular structure of the leaf

1. What is the function of the integumentary tissue? 2. What structural features do the cells of the integumentary tissue have? 3. What function do the cells of the main tissue perform and where are they located? 4. What are intercellular spaces?

Getting to know the internal structure of the leaf blade will help you better understand the importance of green leaves in plant life.

Skin structure. The top and bottom of the leaf are covered with a thin transparent skin; its cells protect the leaf from damage and drying out. Peel - one of the types of plant integumentary tissue.

Among the colorless and transparent skin cells there are located in pairs closing cells whose cytoplasm contains green plastids - chloroplasts. There is a gap between them. These cells and the gap between them are called stomata Air enters the leaf through the stomatal fissure and water evaporates.

In most plants, stomata are located mainly on the skin of the underside of the leaf blade. On the leaves of aquatic plants floating on the surface of the water, stomata are found only on the upper side of the leaf, and on underwater leaves there are no stomata at all. The number of stomata is huge. So, on a linden leaf there are more than a million of them, and on a cabbage leaf there are several million stomata.

83. Stomata with surrounding skin cells

Leaf skin structure

1. Take a piece of clivia leaf (amaryllis, pelargonium, tradescantia), break it and carefully remove a small section of thin transparent skin from the underside. Prepare the preparation in the same way as the onion skin preparation. Examine under a microscope. (You can use ready-made leaf peel preparations.)

2. Look for discolored skin cells. Consider their shape and structure. What cells are they similar to that you already know?

3. Find stomatal cells? How are stomatal cells different from other onion skin cells?

4. Sketch the onion skin under a microscope. Separately sketch the stomata. Write captions for the drawings.

5. Draw a conclusion about the meaning of the leaf skin.

The structure of the leaf pulp. Under the skin is the pulp of the leaf, consisting of cells of the main tissue . Two or three layers directly adjacent to the upper skin are formed by elongated cells tightly adjacent to each other. They resemble columns of almost the same size, so the upper part of the main leaf tissue is called columnar. There are especially many chloroplasts in the cytoplasm of these cells.

Beneath the columnar tissue lie more rounded or irregularly shaped cells. They do not fit tightly to each other. The intercellular spaces are filled with air. There are fewer chloroplasts in these cells than in the cells of columnar tissue. These cells form spongy tissue.

84. Internal structure of a leaf

The structure of leaf veins. If you examine a cross section of a leaf blade under a microscope, you can see conductive bundles leaf - veins consisting of vessels, sieve tubes And fibers Strongly elongated cells with thick walls - fibers - give the sheet strength. Water and minerals dissolved in it move through the vessels. Sieve tubes, unlike vessels, are formed by living long cells. The transverse partitions between them are pierced by narrow channels and look like sieves. Solutions of organic substances move through sieve tubes from the leaves.

Cellular structure of the leaf

1. Study the finished micropreparations of a leaf cut. Find the cells of the upper and lower skin, stomata.

2. Examine the leaf pulp cells. What shape do they have? How are they located?

3. Find intercellular spaces. What is their significance?

4. Find the conductive bundles of the sheet. What cells are they formed by? What functions do they perform? Compare the microscopic slides with the textbook picture.

5. Draw a cross section of the sheet and label all parts.

LEAF SKIN. STOMA. CHLOROPLAST. Columnar and spongy tissues. LEAF PULP. CONDUCTING BAND. VESSELS. SIEVE TUBES. FIBERS

1. What cells form the leaf blade? 2. What is the significance of the leaf skin? What tissue cells is it formed from? 3. What are stomata and where are they located? 4. What structure do the leaf pulp cells have? What type of fabric are they? 5. Which leaf cells contain the most chloroplasts? 6. What function do the conducting bundles of the leaf perform? What tissue cells are they formed by?

Place two onions in jars of water so that the water touches the base. Place one jar in a dark place and the other in a lighted one. Watch the leaves grow. How are they different? Why?

The number and location of stomata on the upper and lower surfaces of leaves is associated with the conditions in which the plants grow.

The number of stomata in different plants per 1 mm2 of leaf surface

The more polluted the air, the lower the number of stomata: leaves collected from trees growing in suburbs, where the air is relatively clean, have 10 times more stomata per unit of leaf surface than leaves from trees in heavily polluted industrial areas.

§ 25. The influence of environmental factors on the structure of the leaf. Leaf modifications

1. What does ecology study? 2. What environmental factors can affect the plant? 3. Remember the differences between dandelions growing in the open with a lack of moisture and in the shade on well-moistened soil.

The shape, size and structure of the leaves largely depend on the living conditions of the plants.

Leaves and humidity factor. The leaves of plants in humid areas are usually large with a large number of stomata. A lot of moisture evaporates from the surface of these leaves. Such plants include monstera, ficus, and begonia, which are often grown in rooms.

The leaves of plants in arid places are small in size and have adaptations that reduce evaporation. This is dense pubescence, a waxy coating, a relatively small number of stomata, etc. Some plants, for example aloe, agave, have soft and succulent leaves. They store water.

Leaves and lighting conditions. The leaves of shade-tolerant plants have only two or three layers of rounded cells, loosely adjacent to each other. Large chloroplasts are located in them so that they do not shade each other. Shade leaves tend to be thinner and darker green in color because they contain more chlorophyll.

In plants in open areas, the leaf pulp contains several layers of columnar cells tightly adjacent to each other. They contain less chlorophyll, so light leaves are lighter in color. Both leaves can sometimes be found in the crown of the same tree. .

85. Light and shadow lilac leaves

86. Modifications of leaves

Leaf modifications. In the process of adapting to environmental conditions, the leaves of some plants have changed because they began to play a role that is not characteristic of typical leaves. For example, some of the leaves of barberry have changed into spines. Turned into thorns and leaves of cacti. They evaporate less moisture and protect plants from being eaten by herbivores .

In peas, the upper parts of the leaves are turned into tendrils. They serve to maintain the plant stem in an upright position.

The leaves of insectivorous plants that live on soils poor in nitrogenous substances are interesting. A small sundew plant grows on peat bogs . Its leaf blades are covered with hairs that secrete a sticky liquid. The sticky droplets, shiny like dew, attract insects. Insects that land on the leaf become stuck in the sticky liquid. First, the hairs, and then the leaf blade, bend and envelop the victim. When the leaf blade and hairs unfold again, only its integument will remain of the insect. The plant leaf will “digest” and absorb all the living tissues of the insect.

87. Round-leaved sundew

LIGHT LEAVES. SHADOW LEAVES. SHEET CHANGES

1. Is it possible to distinguish between plants in humid places and dry areas by appearance? 2. Prove that the structure of the leaf is related to the living conditions of the plants. 3. Why do floating leaves of aquatic plants have stomata only on the upper side of the leaf, while leaves submerged in water have no stomata at all? 4. What is the significance of modified leaves in plant life? Give examples of such leaves. 5. Explain why in the crown of one tree the light leaves are similar in structure to the leaves of plants in open areas, and the shadow leaves are similar to the leaves of shade-tolerant plants.

Consider a few indoor plants. Try to determine the conditions under which they grew in their homeland. Based on what signs did you draw your conclusion?

Prepare and examine under a microscope preparations of leaves of aloe, tradescantia, uzambar violet and other plants.

Among cacti, only Peirescia (often grown indoors) has true leaves that fall off during drought.

In such typical steppe and semi-desert plants as feather grass, stomata are located on the upper side of the leaf, and the leaf, under conditions of lack of moisture, is capable of curling into a tube. The stomata are then inside the tube and isolated from the surrounding dry air. In the cavity of the tube, the concentration of water vapor increases, which leads to a weakening of evaporation .

88. Feather grass leaf

§ 26. Structure of the stem

1. What is called an escape? 2. What functions do mechanical, conductive, and integumentary tissue perform? 3. What stems do plants you know have? 4. How are the stems of trees, shrubs, and grasses different?

Stem - the axial part of the plant shoot, it conducts nutrients and carries leaves to the light. Spare nutrients may be deposited in the stem. Leaves, flowers, fruits with seeds develop on it.

89. Variety of stems

Variety of stems. There are two main types of stems: herbaceous and woody.

herbaceous stems usually exist for one season. These are tender flexible stems of grasses and young shoots of tree species. Woody stems acquire hardness due to the deposition of a special substance in the membrane of their cells - lignin. Lignification occurs in the stems of trees and shrubs starting in the second half of summer of the first year of their life.

Herbaceous plants are better adapted to changing environmental conditions; their forms are very diverse. They grow in water and in very dry places, in the hot tropics and in permafrost areas.

According to the direction of growth, stems are divided into erect, climbing, climbing, and creeping. .

Most plants have stems erect, they grow vertically upward. Erect stems have well-developed mechanical tissue; they can be woody (birch, apple tree) or herbaceous (sunflower, corn).

90. Layers on a cut tree trunk

Curly the stems, rising upward, wrap around the support (field bindweed, beans, hops).

climbing the stems rise upward, clinging to the support with tendrils (grapes, peas) or adventitious roots growing from the stem (ivy).

Creeping stems spread along the ground and can take root at nodes (strawberry, cinquefoil).

Internal structure of the stem. On a cross section of a branch or cut of a tree, the following areas can be easily distinguished: bark, cambium, wood and pith .

Young (annual) stems are covered on the outside peel, which is then replaced by a plug consisting of dead cells filled with air. The skin and cork are integumentary tissues. They protect the deeper cells of the stem from excessive evaporation, various damage, and from the penetration of atmospheric dust with microorganisms that cause plant diseases.

In the skin of the stem, as in the skin of the leaf, there are stomata through which gas exchange occurs. Developing in a traffic jam lentils - small tubercles with holes, clearly visible from the outside, especially in elderberry, oak and bird cherry. Lentils are formed by large cells of the main tissue with large intercellular spaces. Gas exchange occurs through them .

91. Cross section of a branch under a microscope

Some trees develop thick layers traffic jams. A particularly powerful cork develops on the trunk of the cork oak tree. It is used for various household needs.

There are cells under the skin and cork bark, which may contain chlorophyll is the main tissue. The inner layer of the cortex is called bast

It consists of sieve tubes, thick-walled bast fibers and groups of cells of the main tissue.

Sieve tubes - this is a vertical row of elongated living cells, the transverse walls of which are pierced with holes (like a sieve), the nuclei in these cells have collapsed, and the cytoplasm is adjacent to the membrane. This is a conductive bast tissue through which solutions of organic substances move.

bast fibers, elongated cells with destroyed contents and lignified walls represent the mechanical tissue of the stem. In the stems of flax, linden and some other plants, bast fibers are especially well developed and very strong. Linen cloth is made from flax bast fibers, and bast and matting are made from linden bast fibers.

92. The influence of living conditions on the growth of a tree in thickness

The dense, widest layer that lies deeper is wood - main part of the stem. It is formed by cells of different shapes and sizes: vessels of conductive tissue, wood fibers of mechanical tissue and cells of the main tissue.

All layers of wood cells formed in spring, summer and autumn make up the annual growth ring.

The small autumn cells are different from the large spring wood cells of the following year that are next to them. Therefore, the boundary between adjacent annual rings on a cross section of wood in many trees is clearly visible. By counting the number of growth rings using a magnifying glass, you can determine the age of a felled tree or cut branch.

By the thickness of the growth rings you can find out in what conditions the tree grew in different years of its life. Narrow growth rings indicate a lack of moisture, shading of the tree and its poor nutrition .

Lies between bark and wood cambium. It consists of narrow long cells of educational tissue with thin membranes. It cannot be detected with the naked eye, but can be felt by tearing off part of the bark from the surface of the wood and running your fingers over the exposed area. The cambium cells rupture and their contents flow out, moistening the wood.

In spring and summer, the cambium divides vigorously, and as a result, new bast cells are deposited towards the bark, and new wood cells are deposited towards the wood. The stem grows in thickness. When the cambium divides, much more wood cells are formed than bast. In autumn, cell division slows down, and in winter it stops completely.

In the center of the stem there is a looser layer - core, in which reserves of nutrients are deposited, clearly visible, for example, in aspen, elderberry and some other plants. In birch and oak it is very dense, and the border with the wood is difficult to see. The core consists of large cells of the main tissue with thin membranes. Some plants have large intercellular spaces between cells. This core is very loose.

From the core in the radial direction through the wood and bast pass medullary rays. They consist of cells of the main tissue and perform storage and conducting functions.

Internal structure of a tree branch

1. Examine the branch, find lentils (tubercles with holes). What role do they play in the life of a tree?

2. Prepare transverse and longitudinal sections of the branch. Use a magnifying glass to examine the layers of the stem in the sections. Using the tutorial, determine the name of each layer.

3. Use a needle to separate the bark, try to bend it, break it, stretch it. Read in your textbook what the outer layer of the bark is called. What is bast, where is it located, what is its significance for the plant?

4. In a longitudinal section, examine the bark, wood, and pith. Test each layer for strength.

5. Separate the bark from the wood, run your finger along the wood. How do you feel? Read the tutorial about this layer and its meaning.

6. Draw transverse and longitudinal sections of the branch and label the names of each part of the stem.

7. Find wood on a cut tree stem, use a magnifying glass to count the number of growth rings and determine the age of the tree.

8. Consider the growth rings. Are they the same thickness? Explain how wood formed in the spring differs from wood formed later in the year.

9. Determine which layers of wood are older - those lying closer to the middle or to the bark. Explain why you think so.

The structure of the stem of herbaceous plants differs from the structure of the stem of tree species. In herbaceous plants, cells do not become lignified, and mechanical tissues are poorly developed. In the stems of grasses, the cells of the main tissue are well developed.

The stems of dicotyledons have cambium tissue, but the stems of monocots do not have cambium, so they hardly grow in thickness.

GRASS STEM. WOODY STEM. UPREAM, CLIMBING, CLIMBING, CREEPING STEMES. LENTILS. CORK. BARK. LUB. SIEVE TUBES. BAT FIBERS. CAMBIUM. WOOD. CORE. MEDIUM RAYS

1. What is the internal structure of the stem of a tree or shrub? 2. What is the significance of the skin and the cork? 3. Where is the phloem located and what cells does it consist of? 4. What is cambium? Where it is located? 5. What layers are visible on a cross section of a stem when viewed with the naked eye and with a microscope? 6. What are tree rings? What can you tell from the growth rings? Why are the growth rings of many tropical plants not visible?

1. Look at the lentils on the branches of elderberry, bird cherry, oak and other trees and shrubs.

2. Determine the age of any cut tree by its growth rings. Make a drawing of the saw cut. Indicate in the picture the side that the tree faced north.

3. Take branches of apple tree, wild rosemary (Siberian rhododendron), cherry and place them in a vessel with water in a warm, bright room. Add fresh water to the container. In one and a half to two weeks, flowers will bloom on the branches. Use them when studying the structure of a flower.

In most trees, the smooth cork is replaced by a cracked bark. It consists of alternating layers of cork and other dead bark tissues.

In fruit trees, the crust usually forms on the 6th–8th year, in linden – on the 10th–12th year, in oak – on the 25th–30th year of life. Some trees (sycamore, eucalyptus) do not form a crust at all.

Dwarf juniper trees in the tundra have a trunk only 8 cm thick, American sequoias reach 10 m in diameter at the base of the trunk, and our oaks are over 1 m.

Based on the growth rings, it was possible to establish that the most durable trees can be considered baobab and dracaena; specimens were found in Africa whose age is about 6 thousand years.

In our country, cypress trees are the most durable - 3 thousand years; oaks, chestnuts, cedars – 2 thousand years; spruce – 1.6 thousand years; linden – 1 thousand years.

Bud. This is a rudimentary shoot that has not yet developed. The bud consists of a shortened stem with closely adjacent rudimentary leaves. At the top of the stem there is a growth cone (apical meristem). Due to its activity, the stem grows in length, leaves and axillary buds are formed. Flower primordia may appear at the top of the growth cone or in the leaf axils.

On the outside, the buds are protected by bud scales. These are modified lower leaves of the embryonic shoot, located on very close nodes. Dense brownish bud scales protect the tissues of the embryonic shoot from drying out and sunburn. In winter, they almost completely block the access of air inside the kidney.

Kidney scales are often covered with a layer of cuticle and sometimes cork. In poplar, birch, and horse chestnut, the impenetrability is enhanced by resinous sticky secretions; Willow scales are densely covered with hairs.

The development of bud scales is very characteristic of overwintering buds. This closed kidneys, unlike open, or naked, devoid of renal scales And. Of our plants, only a few species have bare overwintering buds. These are, for example, the buds of barberry, brittle buckthorn, and viburnum.

In non-wintering buds, which form on annual shoots of grasses and develop during the same growing season, the bud scales do not have protective devices. Tropical plants do not have them either.

Based on their composition and function, buds are classified into vegetative, floral and mixed. From vegetative shoots develop from the buds floral- flowers or inflorescences, from mixed- stems with leaves, buds and flowers.

According to their location, the buds are apical and lateral. At the ends of the main and side shoots there are apical kidneys Lateral buds can be axillary or adventitious.

Axillary the buds are located one at a time in the leaf axil. Some plants develop not one, but several buds. They can be located one above the other (serial buds - for example, in honeysuckle, walnut, amorpha) or located nearby (collateral buds - in cherry, sea buckthorn, wolf's bast, acacia).

Serial buds are characteristic of dicotyledonous plants, collateral buds are characteristic of monocotyledonous plants (gladiolus, crocus). In dicotyledonous plants, a collateral arrangement of buds can result from the branching of one axillary bud (for example, in potatoes).

In tree and shrub plants, buds are formed on aboveground perennial shoots; annual shoots develop from them, ensuring further growth and development of lateral branches.

In herbaceous perennial plants, the buds are formed on the underground parts of the shoots or underground modified shoots (rhizomes, tubers, etc.). When they unfold, new annual shoots of the herbaceous plant appear - renewal shoots(its above-ground part is restored).

Clover fields are used in crop rotation two to three years after sowing. Every year, plants grow back as a result of the deployment of renewal buds in the ground and underground parts of the stems.

The fate of the buds that are formed each year is different. Some form shoots in the same growing season, others the next year. Some of the buds do not sprout for a long time. Such axillary buds in tree species turn into sleeping. They grow annually with their stem part by the amount of annual growth.

When frosting, biting, or cutting off branches, dormant buds can sprout. On old thick trunks they are called water shoots, or tops.

Water shoots grow very quickly and are distinguished by larger than usual leaves. They develop especially often on oak, elm, maple, and poplar.

The ability of dormant buds to produce shoots is widely used in growing fruit trees and shrubs, growing ornamental plants and creating hedges. Intensive pruning or shearing of shoots causes the awakening of dormant buds and the formation of a dense, compact crown with a large number of fruiting branches.

The apical and lateral axillary buds are formed from the meristem of the growth cone and differ only in location.

But buds can also arise in other ways - from the cambium in the lower parts of the stems, from the pericycle on the roots, from the surface layers of the parenchyma on the leaves and in the upper part of the stem. This subordinate clauses kidneys Their appearance is possible anywhere in the internodes of the stem, on the roots and leaves.

When cutting down many tree species, adventitious buds are formed on the stumps, producing stump shoots (in oak, elm, birch, linden, ash). The growth of shoots here is faster and the leaves are larger than on ordinary branches, since the shoots use ready-made reserves of nutrients.

Trees that have developed from stump growth are usually characterized by less durability and less durable wood that rots easily. In birch, maple, and walnut, groups of adventitious buds sometimes grow, branching inside the stem without reaching the surface. Nodules are formed - “burls” with a very beautiful wood pattern. They are used to make furniture and decorative items.

Adventitious buds on the roots (Fig. 8) form root shoots, or root shoots(aspen, cherry, plum, raspberry, lilac, horseradish).

Rice. 8 Adventitious buds on raspberry roots (A) and sea buckthorn (b). Microphotographs of cross sections

When plowing or harrowing, when the roots of weeds such as thistle, thistle, bindweed are torn, the increased formation and germination of adventitious buds begins on them, which leads to clogging of the fields.

In a few plants (gloxinia, begonia, Saintpaulia, or Uzumbara violet), adventitious buds are also formed on the leaves, often after wounding. This property is used for vegetative propagation.

Escape development. When a seed germinates from the bud of the embryo, the first shoot of the plant is formed - main escape, or escape of the first order.

From the lateral axillary buds of the main shoot develop side shoots- shoots of the second order, on them - shoots of the third order, etc. Happens branching, a system of shoots is formed, consisting of the main shoot and lateral shoots of the second and subsequent orders. Branching and the formation of a shoot system increases the overall surface of the plant.

The spring growth of shoots begins with the opening of buds: the bud scales fall off, leaving closely spaced scars at the site of their attachment, marking the base of the annual shoot. These scars make it possible to determine the boundaries of annual growth in woody plants.

After the buds open and the scales fall off, intensive growth of the shoot begins. Elongation of the shoot occurs as a result of apical and intercalary (intercalary) growth.

The annual shoots of most of our plants have one growth period - from April–May to June–July. The growth of the shoot ends with the formation of a flower, inflorescence or apical bud.

But in some cases, after a short period of dormancy, shoot growth resumes in July - so-called Ivanov shoots are formed. They are usually found in oak, less often in maple and spruce. In subtropical plants, such as citrus fruits, an even greater number of annual increments are observed.

Leaf arrangement – the order in which the leaves are placed on the stem. If one leaf extends from each node, this leaf arrangement is called next, or spiral(rye, wheat, buckwheat, apple tree). If two leaves come from each node (maple, lilac, sage) - this is opposite leaf arrangement, three or more leaves (oleander, raven's eye) – whorled.

The leaves are located on the shoot so that they do not shade each other. Different lengths and bends of petioles, unequal leaf sizes, twisting of internodes lead to the formation sheet mosaic. This arrangement allows for the best use of space and incident light.

Growth of shoots. Plants are characterized by long-term growth with the formation of new organs. Growth, elongation of the shoot occurs due to the growth cone without increasing the number of axes. In the process of evolution, two methods of growth have been developed: monopodial and sympodial.

Monopodial growth is characterized by unlimited apical growth of the shoot. The apical bud produces an annual shoot, which in turn ends in an apical bud. And so on every year. In this way, the main shoot is formed - the axis of the first order.

Shoots developed from lateral buds always lag behind the main one in growth. Each lateral branch also has monopodial branching. This type of branching is well expressed in spruce, fir, aspen, and meadow clover (Fig. 9).

Rice. 9 Rise:

A – monopodial (a – diagram, b – pine branch); B – sympodial (c – diagram, d – bird cherry branch); C – false dichotomous (d – diagram, f – lilac branch); 1...4 – axes of the first and subsequent orders

Sympodial growth is characterized by early cessation of apical growth. The apical bud either dies or gives weak growth. The lateral bud closest to it begins to grow. The escape that developed from it is, as it were, a continuation of the main thing. The apical bud of this shoot again ceases activity, and a new “main” shoot arises from the underlying lateral bud, etc.

With sympodial branching, the entire stem consists of separate sections, as if made up of lateral shoots (linden, willow, apple, potato, strawberry). A so-called reversal occurs.

A special case of sympodial growth is false dichotomous. It occurs when the leaves and, consequently, the buds are opposite. In this case, both upper buds begin to grow and two apical shoots appear. This type of growth is characteristic of lilac and horse chestnut, in which the apical bud forms inflorescences, as well as of carnation.

Sympodial growth occurs in most trees, shrubs and herbs. The ability to replace dead apical shoots with lateral ones, due to which growth continues, is of great biological importance. It increases the vitality of the plant, promotes the expansion of lateral buds, which leads to the formation of more branches, leaves, and flowers.

Freezing, which is so common in the middle zone, drying out, breaking off or biting the apical buds does not lead to the death of the shoot or a delay in its growth.

Branching. It is characteristic of the shoots of most plants. Branching is of two types: apical and lateral. With apical dichotomous branching the growth cone bifurcates (branches), giving rise to two axes of the next order. Each of them, in turn, gives two axes, etc. This is the most ancient branching. It is found in algae, some club mosses and ferns. Lateral branching carried out by lateral buds with the formation of a shoot system.

Tillering- a special type of branching found in herbaceous and woody plants. During tillering, lateral shoots (tillering shoots) develop only from the ground and underground buds of the mother shoot.

The internodes at the base of the shoot are shortened, therefore, many lateral buds are located in close proximity to each other.

The area of ​​shortened internodes where tillering shoots are formed is called tillering zone, or tillering node. The tillering zone is especially clearly expressed in cereals. Adventitious roots develop on tillering shoots.

Main article: Escape

Bud in plants

Apical bud

Lateral bud (axillary)

In the axils of the leaves there are lateral (axillary) buds. Axillary buds are located on the stem alternately (willow, linden, alder, aspen) or oppositely (elderberry, maple, lilac, ash) (Fig. 113).

Accessory buds

Sometimes buds may develop not in the leaf axil, but on the internodes of the stem, roots or leaves. Such buds are called accessory buds.

Overwintering buds

In temperate latitudes in mid-summer or autumn, in the tropics with the onset of the dry period, the apical and axillary buds enter seasonal dormancy. In temperate latitudes, such buds are called overwintering or dormant. The outer leaves of these buds turn into dense covering bud scales, almost hermetically covering the inner parts of the bud. Covering scales reduce the evaporation of water from the surface of the internal parts of the buds, and also protect the buds from freezing, pecking by birds, etc.

Dormant buds

Not all buds laid in the previous year bloom on trees and shrubs. Many axillary buds remain dormant for a long time, sometimes for many years. Such buds are called dormant (Fig. 116). In oak they “sleep” for up to 100 years, in birch - up to 50, in aspen - 40, in honeysuckle - 35, in hawthorn - up to 25 years.

When the apical bud disappears (due to freezing, biting, cutting), the dormant buds begin to grow and grow into elongated shoots. Such shoots especially often develop on oak, elm, maple, rowan, poplar, and apple trees.

Dormant buds are of great importance for restoring the crown when it is damaged by spring frosts and during decorative pruning of trees and shrubs. In cities, the crowns of poplars are often severely pruned, leaving only the trunk or several large side branches. In spring, many young shoots appear on the pruned parts of the tree, which develop from dormant buds (Fig. 117).

Structure of plant buds

Vegetative bud

A vegetative bud consists of a rudimentary stem and rudimentary leaves located on it. In the axils of the leaves you can find tiny rudimentary axillary buds. On the outside, the buds are protected by bud scales. Material from the site http://wiki-med.com

Inside the bud at the apex of the stem there is a growth cone consisting of cells of the apical educational tissue. Thanks to the division, growth and change of its cells, the stem grows, new leaves and buds are formed (Fig. 114).

In the generative (floral) buds on the stem, in addition to the rudimentary leaves, there are the rudiments of flowers or one flower. This is clearly visible in elderberry (see Fig. 114) and chestnut. lilac. The generative buds of many woody plants differ from the vegetative ones in size and shape: they are larger and often rounded.

• pastenia with wintering buds

• vegetative buds of plants

• Which apple tree buds are vegetative or generative?

• , structure, classification of the kidney

• kidneys that remain dormant for a long time are called

Questions for this article:

• What is the function of the kidneys?

• How do kidneys develop?

Structure and types of kidneys

1. The escape

knot, internode.

leaf axil.

axillary bud.

Closed node

Open node

Types of shoots

Elongated shoots have long internodes. During bud development, internodes develop rapidly. They perform the function of supporting or skeletal organs.

Short shoots have very close internodes.

Internodes hardly grow. In herbaceous plants, the leaves sit very close, forming a rosette (primrose, plantain, dandelion). In woody forms, such shoots often bear flowers and fruits.

According to their functions, shoots are:

Vegetative

Generative (floriferous)

Main escape

Side shoots

Annual shoots

Elementary shoots

Escape structure

A

1 - apical bud;

2 - axillary bud;

3 - internode;

4 - leaf scar;

5 - node;

6

annual growth);

7

conductive bundles);

B

Structure and types of kidneys

Bud

Types of kidneys:

4 – rudimentary leaves.

Apical–(

Axillary buds

The bud consists of a stem with short internodes and rudimentary leaves or flowers. The top of the bud is covered with protective covering scales. The bud ensures long-term growth of the shoot and its branching, i.e.

formation of a shoot system.

Vegetative buds floral (generative) mixed,

Wintering

Open buds- naked, devoid of scales.

Stem

Stem

rounded, but also angular, three-, four- or multifaceted, ribbed, grooved, sometimes completely flat, flattened winged.

Branching of shoots

dichotomous, monopodial, sympodial.

At dichotomous

Dichotomous in lower plants ).

There are so-called isotomic anisotomous

At monopodial

Monopodial branching is the next stage in the evolution of shoot branching. In plants with a monopodial type of shoot structure, the apical bud is retained throughout the life of the shoot.

Monopodial branching is common among gymnosperms and is also found in many angiosperms (e.g., many palm species, as well as plants from Orchidaceae family–). Some of them have a single vegetative shoot (for example, Phalaenopsis pleasant).

Monopodial plants

At sympodial

In plants with sympodial depending on the type of shoot structure, the apical bud, having completed development, dies or gives rise to a generative shoot.

After flowering, this shoot no longer grows, and a new one begins to develop at its base. The shoot structure of plants with a sympodial type of branching is more complex than that of plants with a monopodial type; sympodial branching is an evolutionarily more advanced type of branching. The word “sympodial” is derived from ancient Greek. συν- (“together”) and πούς (“leg”).

Plant buds

Sympodial .

Sympodial plants- a term most often used in describing plants of tropical and subtropical flora, as well as in popular scientific literature on indoor and greenhouse floriculture.

Such equal dichotomy (isotomy) represents the original type of dichotomous branching. It was characteristic of some rhyniophytes, but is also found in some modern lycophytes and pteridophytes, as well as in Psilotum.

As a result of the unequal growth of the two daughter branches, when one of the branches is somewhat ahead of the other, the equal dichotomy turns into an unequal dichotomy (anisotomy), very well expressed in the primitive extinct Devonian genus Horneophyton.

Types of shoot branching(according to L.I.

B – sympodial (birch);

Anatomy Classification of the kidneys

Kidneys are classified according to:

Location on the escape: apical(terminal) and lateral.

Kidney (botany)

A shoot of the first order (main shoot) develops from the apical shoots, and shoots of the second, third, fourth, etc., that is, lateral shoots, develop from the lateral shoots.

2. Origin: there are axillary and extra-axillary. Axillaries are located in the leaf axil and are formed exogenously (in the form of tubercles).

Οʜᴎ there are single(located singly in the leaf axil) and group(several pieces each). Groups can be serial (several buds are located above each other) and collateral (located nearby).

Extra-axillary buds are located on the internodes and are formed on an already formed shoot endogenously (from the cambium, pericycle, phellogen, phloem parenchyma).

Broods called such buds that sprout into a small plant that falls away from the mother and moves on to independent existence ( bryophyllum).

81. Lilac branch:

A – general view, B – shoot tip, C – buds (longitudinal section):

1 – lateral bud, 2 – leaf scar, 3 – annual growth limit

4 – bud scales, 5 – rudimentary inflorescence, 6 – growth cone.

3. According to their significance in life, plants are classified into:

- dormant buds - formed at the end of the growing season and at rest tolerate unfavorable conditions (cold, heat), and with the onset of favorable conditions they give rise to shoot growth;

- enrichment bud, which gives growth immediately after initiation, during the same growing season, forming enrichment shoots (increase the photosynthetic surface);

— dormant buds that, having become established, do not begin to grow for a number of years.

Such a bud annually forms a certain number of metamers; they are always located on the surface of the stem. When pruning and aging of the shoot system, they give growth and restore the shoot system of plants.

Based on their structural features, they are classified into:

- vegetative, consisting of a rudimentary stem and rudimentary leaves;

- vegetative-generative, in addition to the rudimentary stem and leaves, contain the rudiments of inflorescences and flowers;

- generative - contain the rudiments of inflorescences and flowers;

- closed, which are covered with dense kidney scales;

- open, without dense kidney scales.

Structure and types of kidneys

Types of macro- and microscopic structure of the stem

1. The escape- part of the stem that has grown in one growing season along with the leaves and buds located on it. This is an organ that arises from the apical meristem and is divided at an early stage of morphogenesis into specialized parts: stem, leaves, buds.

Its main function is photosynthesis.

Parts of the shoot can also serve for vegetative propagation, accumulation of reserve products and water.

The area of ​​the stem at the level of leaf origin is called knot, and the section of the stem between two nodes is internode.

The angle between the leaf petiole and the stem is called leaf axil.

Forms above the node in the leaf axil axillary bud.

Closed node– a leaf or whorl of leaves completely surrounds the stem with its bases.

Open node– bears a leaf that does not completely cover the stem.

Types of shoots

In the case of clearly defined internodes, the shoot is called elongated.

If the nodes are close together and the internodes are almost invisible, then this is a shortened shoot (fruit, rosette).

According to the development of internodes, there are shoots.

Elongated shoots have long internodes.

During bud development, internodes develop rapidly. They perform the function of supporting or skeletal organs.

Short shoots have very close internodes. Internodes hardly grow. In herbaceous plants, the leaves sit very close, forming a rosette (primrose, plantain, dandelion). In woody forms, such shoots often bear flowers and fruits.

According to their functions, shoots are:

Vegetative– provide aerial nutrition to plants.

Generative (floriferous)- perform the function of reproduction, bearing flowers or fruits.

Main escape– the first shoot of a plant that develops from an embryonic shoot.

Side shoots– shoots of the second order, develop on the main shoot.

Annual shoots(growth) – grow from the buds in one growing season (once a year).

Elementary shoots– are formed in one growth cycle, but there are several of them per year.

Escape structure

A- horse chestnut shoot without leaves:

1 - apical bud;

2 - axillary bud;

3 - internode;

4 - leaf scar;

5 - node;

6 - place of attachment of the bud scales (border

annual growth);

7 - leaf traces (ends of torn

conductive bundles);

B- elongated annual shoot of aspen

Structure and types of kidneys

Bud- a shortened embryonic shoot, in a state of relative dormancy.

Types of kidneys: A – vegetative; 1 – embryonic shoot;

B – generative; 2 – kidney scales;

B – vegetative-generative; 3 – rudimentary flowers;

4 – rudimentary leaves.

Apical–( terminal) bud formed at the top of the shoot and causing the stem to grow in length.

Axillary buds-formed in the leaf axil and causing the development of lateral shoots.

The bud consists of a stem with short internodes and rudimentary leaves or flowers. The top of the bud is covered with protective covering scales. The bud ensures long-term growth of the shoot and its branching, i.e. formation of a shoot system.

Vegetative buds– form shoots with leaves; floral (generative)– form flowers or inflorescences; mixed,(vegetative - generative) buds - form leafy shoots with flowers.

Wintering(closed) or dormant buds have hard covering bud scales, which reduce evaporation from the surface of the internal parts of the buds, and also protect them from freezing, pecking by birds, etc.

Open buds- naked, devoid of scales.

Accessory (adventitious) buds are formed on any plant organs and do not differ in structure from others; they ensure active vegetative regeneration and reproduction of plants (raspberry, aspen, sow thistle, dandelion).

Stem

Stem– the main structural part of the shoot, consisting of nodes and internodes.

The stem has the following functions:

1. conductive - ascending and descending currents of substances move between the roots and leaves in the stem.
2. mechanical (supporting) - carries leaves, buds, flowers and fruits.
3. assimilation - the green part of the stem is capable of performing the function of photosynthesis.
4. storage of nutrients and water.

The stem is usually cylindrical in shape and is characterized by radial symmetry in the arrangement of tissues.

However, in cross section it can be not only rounded, but also angular, three-, four- or multifaceted, ribbed, grooved, sometimes completely flat, flattened, or bearing protruding flat ribs - winged.

Types of stems by cross-sectional shape: 1 – rounded; 2 – flattened; 3 – triangular; 4 – tetrahedral; 5 – multifaceted; 6 – ribbed; 7 – grooved; 8, 9 – winged.

Types of stems by position in space: 1 – erect; 2 – rising; 3 – creeping; 4 – creeping; 5 – curly; 6 – climbing (clinging).

Branching of shoots

Branching is the process of formation of new shoots and the nature of their relative arrangement on the stem, perennial branches and rhizome.

Since the shoot is an axial organ, it has an apical meristem, which ensures unlimited growth in length.

Such growth is accompanied by more or less regular branching of the shoot. In lower plants, as a result of branching, a branched thallus (thallus) appears, in higher plants, systems of shoots and roots are formed. Branching allows you to repeatedly increase the photosynthetic surface and provide the plant with organic substances.

Several types of branching are observed in different plants: dichotomous, monopodial, sympodial.

At dichotomous During branching, the growth cone splits in two (mosses).

Dichotomous branching is the most primitive type of branching, observed as in lower plants, and in some higher plants (for example, Bryophyta, Lycopodiophyta, some Pteridophyta).

With dichotomous branching, the growth cone is divided in two, the newly formed apexes are also divided in two, and so on.

There are so-called isotomic dichotomous branching (the resulting branches are equal in size) and anisotomous (in which the resulting branches are unequal)

At monopodial During branching, the apical bud functions throughout life, forming the main shoot (first-order axis), on which second-order axes develop in acropetal sequence, third-order axes on them, etc.

Monopodial branching is the next stage in the evolution of shoot branching. In plants with a monopodial type of shoot structure, the apical bud is retained throughout the life of the shoot. Monopodial branching is common among gymnosperms and is also found in many angiosperms (e.g., many palm species, as well as plants from Orchidaceae family–gastrochilus, phalaenopsis and others).

Some of them have a single vegetative shoot (for example, Phalaenopsis pleasant).

Monopodial plants- a term most often used in describing plants of tropical and subtropical flora, as well as in popular scientific literature on indoor and greenhouse floriculture.

Monopodial plants can vary significantly in appearance. Among them there are rosettes, with elongated shoots, and bush-like ones.

At sympodial During branching, one of the upper axillary buds forms a second-order axis, which grows in the same direction as the first-order axis, displacing its dying part to the side.

This division was first proposed by the German botanist Pfitzer at the end of the 19th century.

In plants with sympodial depending on the type of shoot structure, the apical bud, having completed development, dies or gives rise to a generative shoot. After flowering, this shoot no longer grows, and a new one begins to develop at its base. The shoot structure of plants with a sympodial type of branching is more complex than that of plants with a monopodial type; sympodial branching is an evolutionarily more advanced type of branching. The word “sympodial” is derived from ancient Greek.

συν- (“together”) and πούς (“leg”). Sympodial branching is characteristic of many angiosperms: for example, for lindens, willows and many orchids.

Sympodial plants- a term most often used in describing plants of tropical and subtropical flora, as well as in popular scientific literature on indoor and greenhouse floriculture.

In the first stages of evolution, the apical meristems of both branches of each fork grow at the same rate, which leads to the formation of identical or almost identical daughter branches.

Such equal dichotomy (isotomy) represents the original type of dichotomous branching.

Structure and types of kidneys

It was characteristic of some rhyniophytes, but is also found in some modern lycophytes and pteridophytes, as well as in Psilotum. As a result of the unequal growth of the two daughter branches, when one of the branches is somewhat ahead of the other, the equal dichotomy turns into an unequal dichotomy (anisotomy), very well expressed in the primitive extinct Devonian genus Horneophyton.

Types of shoot branching(according to L.I.

Lotova): A – dichotomous (moss);

B – monopodial (spruce, leaves removed);

B – sympodial (birch);

I-III – serial numbers of increments;

1 – apical bud; 2 – lateral buds; 3 – dead upper parts of shoots.

Escape structure

The organism of a flowering plant is a system of roots and shoots. The main function of above-ground shoots is to create organic substances from carbon dioxide and water using solar energy. This process is called air feeding of plants.

A shoot is a complex organ consisting of a stem, leaves, and buds formed during one summer.

The main shoot is the shoot that develops from the bud of the seed embryo.

Lateral shoot is a shoot that appears from a lateral axillary bud, due to which the stem branches.

An elongated shoot is a shoot with elongated internodes.

Shortened shoot - a shoot with shortened internodes.

A vegetative shoot is a shoot that bears leaves and buds.

Generative shoot - a shoot bearing reproductive organs - flowers, then fruits and seeds.

Branching and tillering of shoots

Branching is the formation of lateral shoots from axillary buds.

A highly branched system of shoots is obtained when lateral shoots grow on one (“mother”) shoot, and on them, the next lateral shoots, and so on. In this way, as much air supply as possible is captured.

The branched crown of the tree creates a huge leaf surface.

Tillering is branching in which large side shoots grow from the lowest buds located near the surface of the earth or even underground. As a result of tillering, a bush is formed. Very dense perennial bushes are called turfs.

Types of shoot branching

During evolution, branching appeared in thallus (lower) plants; in these plants the growing points simply bifurcate.

This branching is called dichotomous; it is characteristic of pre-shoot forms - algae, lichens, liverworts and anthocerotic mosses, as well as thickets of horsetails and ferns.

With the appearance of developed shoots and buds, monopodial branching occurs, in which one apical bud retains its dominant position throughout the life of the plant.

Such shoots are orderly and the crowns are slender (cypress, spruce). But if the apical bud is damaged, this type of branching is not restored, and the tree loses its typical appearance (habitus).

The most recent type of branching in terms of time of occurrence is sympodial, in which any nearby bud can develop into a shoot and replace the previous one.

Structure and types of kidneys

Trees and shrubs with this type of branching can easily be pruned, crown formed, and after a few years they grow new shoots without losing their habit (linden, apple, poplar).

A type of sympodial branching is false dichotomous, which is characteristic of shoots with opposite leaves and buds, so instead of the previous shoot, two grow at once (lilac, maple, chebushnik).

Kidney structure

A bud is a rudimentary, not yet developed shoot, at the top of which there is a growth cone.

Vegetative (leaf bud) - a bud consisting of a shortened stem with rudimentary leaves and a growth cone.

Generative (floral) bud is a bud represented by a shortened stem with the rudiments of a flower or inflorescence.

A flower bud containing 1 flower is called a bud.

Apical bud - a bud located at the top of the stem, covered with young leaf buds overlapping each other.

Due to the apical bud, the shoot grows in length. It has an inhibitory effect on the axillary buds; removing it leads to the activity of dormant buds. Inhibitory reactions are disrupted and the buds bloom.

At the top of the embryonic stem there is the growth part of the shoot - the growth cone. This is the apical part of the stem or root, consisting of educational tissue, the cells of which constantly divide through mitosis and give the organ an increase in length.

At the top of the stem, the growth cone is protected by bud scale-like leaves; it contains all the elements of the shoot - stem, leaves, buds, inflorescences, flowers. The root growth cone is protected by a root cap.

Lateral axillary bud is a bud that appears in the axil of a leaf, from which a lateral branching shoot is formed.

The axillary buds have the same structure as the apical one. The lateral branches, therefore, also grow at their apices, and on each lateral branch the terminal bud is also apical.

At the top of the shoot there is usually an apical bud, and in the axils of the leaves there are axillary buds.

In addition to apical and axillary buds, plants often form so-called accessory buds.

These buds do not have a certain regularity in location and arise from internal tissues. The source of their formation can be the pericycle, cambium, parenchyma of the medullary rays. Adventitious buds can form on stems, leaves, and even roots. However, in structure, these buds are no different from ordinary apical and axillary ones. They provide intensive vegetative regeneration and reproduction and are of great biological importance.

In particular, root shoot plants reproduce with the help of adventitious buds.

Dormant buds. Not all buds realize their ability to grow into a long or short annual shoot. Some buds do not develop into shoots for many years. At the same time, they remain alive, capable, under certain conditions, of developing into leafy or flowering shoots.

They seem to be sleeping, which is why they are called sleeping buds.

When the main trunk slows down its growth or is cut down, the dormant buds begin to grow, and leafy shoots grow from them. Thus, dormant buds are a very important reserve for shoot regrowth. And even without external damage, old trees can “rejuvenate” due to them.

Dormant buds, very characteristic of deciduous trees, shrubs and a number of perennial herbs.

These buds do not develop into normal shoots for many years; they often remain dormant throughout the life of the plant. Typically, dormant buds grow annually, exactly as much as the stem thickens, which is why they are not buried by growing tissues.

The stimulus for awakening dormant buds is usually the death of the trunk. When cutting down a birch, for example, stump growth is formed from such dormant buds. Dormant buds play a special role in the life of shrubs.

The shrub differs from a tree in its multi-stemmed nature. Typically, in shrubs the main mother stem does not function for long, several years.

When the growth of the main stem subsides, dormant buds awaken and daughter stems are formed from them, which outstrip the mother in growth. Thus, the shrub form itself arises as a result of the activity of dormant buds.

Mixed bud - a bud consisting of a shortened stem, rudimentary leaves and flowers.

A renewal bud is an overwintering bud of a perennial plant from which a shoot develops.

Vegetative propagation of plants

Way	Drawing	Description	Example
Creeping shoots		Creeping shoots or tendrils, in the nodes of which small plants with leaves and roots develop	Clover, cranberry, chlorophytum
Rhizome		With the help of horizontal rhizomes, plants quickly cover a large area, sometimes several square meters. The older parts of the rhizomes gradually die and are destroyed, and individual branches separate and become independent.	Lingonberries, blueberries, wheatgrass, lily of the valley
Tubers		When there are not enough tubers, you can propagate by parts of the tuber, bud eyes, sprouts and tops of tubers.	Jerusalem artichoke, potatoes
Bulbs		From the lateral buds on the mother bulb, daughter buds are formed, which are easily separated. Each daughter bulb can produce a new plant.	Bow, tulip
Leaf cuttings		The leaves are planted in wet sand, and adventitious buds and adventitious roots develop on them	Violet, sansevieria
By layering		In spring, bend the young shoot so that its middle part touches the ground and the top is directed upward. On the lower part of the shoot under the bud, you need to cut the bark, pin the shoot to the soil at the cut site and cover it with damp soil. By autumn, adventitious roots are formed.	Currants, gooseberries, viburnum, apple trees
Shoot cuttings		A cut branch with 3-4 leaves is placed in water, or planted in wet sand and covered to create favorable conditions. Adventitious roots form on the lower part of the cutting.	Tradescantia, willow, poplar, currant
Root cuttings		A root cutting is a piece of root 15-20 cm long. If you cut off a piece of dandelion root with a shovel, adventitious buds will form on it in the summer, from which new plants will form	Raspberry, rosehip, dandelion
Root suckers		Some plants are able to form buds on their roots
Grafting with cuttings		First, annual seedlings called wildflowers are grown from seeds. They serve as a rootstock. Cuttings are taken from a cultivated plant - this is a scion. Then the stem parts of the scion and rootstock are connected, trying to connect their cambium. This way the tissues grow together more easily.	Fruit trees and shrubs
Kidney grafting		An annual shoot is cut from a fruit tree. Remove the leaves, leaving the petiole. Using a knife, an incision is made in the bark in the shape of the letter T. A developed bud from a cultivated plant, 2-3 cm long, is inserted. The grafting site is tightly tied.	Fruit trees and shrubs
Tissue culture		Growing a plant from educational tissue cells placed in a special nutrient medium. 1. Plant 2. Educational fabric 3. Cell separation 4. Growing a cell culture on a nutrient medium 5. Obtaining a sprout 6. Landing in the ground	Orchid, carnation, gerbera, ginseng, potato

Modifications of underground shoots

Rhizome is an underground shoot that performs the functions of deposition of reserve substances, renewal, and sometimes vegetative propagation.

The rhizome has no leaves, but has a well-defined metameric structure; nodes are distinguished either by leaf scars and remains of dry leaves, or by leaf scars and remains of dry leaves, or by living scale-like leaves and the location of axillary buds. Adventitious roots can form on the rhizome. From the buds of the rhizome, its lateral branches and above-ground shoots grow.

Rhizomes are characteristic mainly of herbaceous perennials - hoofweed, violet, lily of the valley, wheatgrass, strawberry, etc., but are also found in shrubs and shrubs.

The lifespan of rhizomes ranges from two or three to several decades.

Tubers are thickened, fleshy parts of the stem, consisting of one or more internodes. There are above-ground and underground.

Aboveground - thickening of the main stem and side shoots. Often have leaves. Aboveground tubers are a reservoir of reserve nutrients and serve for vegetative propagation; they may contain metamorphosed axillary buds with leaf buds, which fall off and also serve for vegetative propagation.

Underground tubers - thickening of the subcotyledon or underground shoots.

On underground tubers, the leaves are reduced to scales that fall off. In the axils of the leaves there are buds - eyes. Underground tubers usually develop on stolons - daughter shoots - from buds located at the base of the main shoot, look like very thin white stems bearing small colorless scale-like leaves, grow horizontally.

Tubers develop from the apical buds of stolons.

A bulb is an underground, less often above-ground, shoot with a very short thickened stem (bottom) and scaly, fleshy, succulent leaves that store water and nutrients, mainly sugar. Aboveground shoots grow from the apical and axillary buds of the bulbs, and adventitious roots form on the bottom.

Depending on the placement of leaves, bulbs are classified as scaly (onion), imbricated (lily) and compound or complex (garlic). In the axil of some scales of the bulb there are buds from which daughter bulbs develop - children. Bulbs help the plant survive in unfavorable conditions and are an organ of vegetative propagation.

Corms are similar in appearance to bulbs, but their leaves do not serve as storage organs; they are dry, filmy, often the remains of sheaths of dead green leaves.

The storage organ is the stem part of the corm; it is thickened.

Aboveground stolons (lashes) are short-lived creeping shoots used for vegetative propagation.

Found in many plants (drupes, bentgrass, strawberries). They usually lack developed green leaves, their stems are thin, fragile, with very long internodes. The apical bud of the stolon, bending upward, produces a rosette of leaves that easily takes root. After the new plant takes root, the stolons are destroyed. The popular name for these above-ground stolons is mustache.

Spines are shortened shoots with limited growth. In some plants they form in the axils of the leaves and correspond to the side shoots (hawthorn) or are formed on the trunks from dormant buds (locust locust).

Characteristic for plants in hot and dry growing areas. Perform a protective function.

Succulent shoots are above-ground shoots adapted to store water. Typically, the formation of a succulent shoot is associated with the loss or metamorphosis (transformation into spines) of leaves. The succulent stem performs two functions - assimilation and water storage. Characteristic of plants living in conditions of prolonged lack of moisture.

Stem succulents are most represented in the cactus and euphorbia family.

Main article: Escape

Bud in plants- this is a rudimentary shoot. A vegetative bud has a rudimentary stem with a growth cone and rudimentary leaves. The flower bud contains rudimentary flowers. The outside of the buds is covered with bud-like scales. After a period of rest, the buds open. The expansion of shoots from the buds is associated with the growth of internodes and leaves.

Types of plant buds

Apical bud

At the top of the shoot there is usually an apical bud.

Lateral bud (axillary)

In the axils of the leaves there are lateral (axillary) buds.

Axillary buds are located on the stem alternately (willow, linden, alder, aspen) or oppositely (elderberry, maple, lilac, ash) (Fig. 113).

Accessory buds

Sometimes buds may develop not in the leaf axil, but on the internodes of the stem, roots or leaves.

Such buds are called accessory buds.

Overwintering buds

In temperate latitudes in mid-summer or autumn, in the tropics with the onset of the dry period, the apical and axillary buds enter seasonal dormancy. In temperate latitudes, such buds are called overwintering or dormant. The outer leaves of these buds turn into dense covering bud scales, almost hermetically covering the inner parts of the bud. Covering scales reduce the evaporation of water from the surface of the internal parts of the buds, and also protect the buds from freezing, pecking by birds, etc.

Dormant buds

Not all buds laid in the previous year bloom on trees and shrubs. Many axillary buds remain dormant for a long time, sometimes for many years.

Tree structure. From cells to roots

Such buds are called dormant (Fig. 116). In oak they “sleep” for up to 100 years, in birch - up to 50, in aspen - 40, in honeysuckle - 35, in hawthorn - up to 25 years.

When the apical bud disappears (due to freezing, biting, cutting), the dormant buds begin to grow and grow into elongated shoots.

Such shoots especially often develop on oak, elm, maple, rowan, poplar, and apple trees.

Dormant buds are of great importance for restoring the crown when it is damaged by spring frosts and during decorative pruning of trees and shrubs. In cities, the crowns of poplars are often severely pruned, leaving only the trunk or several large side branches. In spring, many young shoots appear on the pruned parts of the tree, which develop from dormant buds (Fig.

Structure of plant buds

Based on their structure, buds are distinguished between vegetative and generative (floral).

Vegetative bud

A vegetative bud consists of a rudimentary stem and rudimentary leaves located on it.

In the axils of the leaves you can find tiny rudimentary axillary buds. On the outside, the buds are protected by bud scales. Material from the site http://wiki-med.com

Inside the bud at the apex of the stem there is a growth cone consisting of cells of the apical educational tissue.

Thanks to the division, growth and change of its cells, the stem grows, new leaves and buds are formed (Fig. 114).

Generative bud (floral)

In the generative (floral) buds on the stem, in addition to the rudimentary leaves, there are the rudiments of flowers or one flower. This is clearly visible in elderberry (see Fig. 114) and chestnut.

lilac. The generative buds of many woody plants differ from the vegetative ones in size and shape: they are larger and often rounded.

On this page there is material on the following topics:

• plant bud biology external and internal structure

• axillary and accessory buds

• internal structure and external buds of poplar

• plant bud functions

• bud structure in plants

Questions for this article:

• What are kidneys?

• What is the function of the kidneys?

• How do generative buds differ from vegetative ones?

• How do kidneys develop?

• What are dormant buds and what function do they perform?

Material from the site http://Wiki-Med.com

A bud is a greatly shortened shoot with rudimentary leaves or reproductive organs. The buds can be vegetative, having shoot and leaf buds; generative, bearing the primordia of a flower or inflorescence, mixed. Based on their location, they distinguish between apical buds (at the end of the shoot) and axillary buds (at the nodes between the leaf petiole and the stem).

According to their functional significance, dormant buds are distinguished, which do not bloom annually and remain alive for many years. And they wake up when the upper part of the stem is removed. From them shoots are formed. Adventitious buds are formed inside stems, leaves, and roots from cells of various tissues and provide vegetative propagation. Dormant buds are formed on those organs that do not die off during the winter or during periods of drought. They require a period of rest, then they ensure the perennial existence of woody or herbaceous plants.

When a seed germinates, a shoot develops from the bud of the seed embryo. In perennial plants, a shoot starts from a bud. A bud is an embryonic shoot. It consists of a shortened stem with closely spaced rudimentary leaves. At the top of the stem there is a growth cone consisting of educational tissue. Due to the division of cells of the growth cone, the stem grows in length, the formation of leaves and outer buds. Outside, the bud is protected by bud scales, which are modified lower leaves of the shoot. According to their location on the shoot, the buds are apical and lateral.

Apical bud

This is the bud located at the top of the shoot, the rest of the buds are lateral. They are divided into axillary and accessory.

Axillary buds

They regularly appear in the axils of young leaf primordia near the top of the mother shoot. Their arrangement exactly corresponds to the leaf arrangement. Therefore, in winter, the location of the leaves can be determined by the buds.

Lateral buds

They develop outside the axil on internodes, roots and leaves and are called adventitious. They often provide vegetative propagation of plants. Adventitious buds on the leaves immediately develop into small plants with adventitious roots, which fall off the leaf of the mother plant and grow into new individuals. These buds are called brood buds (bryophyllium, sundews). They can appear in the leaf axil and change into bulbs (tiger lily) and nodules (viviparous knotweed).

The kidneys are not the same in structure. In most plants they are closed (protected), because on the outside they have bud scales, glued with resin (in conifers), other adhesive substances (poplar), some are often omitted. There are plants with open (unprotected, bare) buds. They lack bud scales (viburnum, buckthorn).

Based on their internal structure, the following types of kidneys are distinguished:

1) vegetative - consist of a rudimentary stem, scales, rudimentary leaves and a growth cone;
2) generative - floral, consisting of a rudimentary stem, scales and primordia of a flower or inflorescence (red elderberry);
3) mixed - consist of a rudimentary stem, scales, rudimentary leaves and rudiments of a flower or inflorescence (apple tree, spirea).

Generative and mixed the buds are larger and more rounded than the vegetative ones.

Buds that remain dormant (autumn - winter) and then unfold and produce new shoots are called overwintering or renewal buds. Due to them, shoots grow.

Dormant buds

They remain dormant for a number of years. The stimulus for their awakening is damage to the trunk.



Table: Shoot (leaf, stem, bud)

THE ESCAPE

The escape- This is the above-ground part of the plant. A vegetative shoot is formed during the development of the embryo, in which it is represented by a bud. Kidney- these are the stem and leaf buds, can be considered the first bud of the plant. During the development of the embryo, the apical meristem of the bud forms new leaves, and the stem lengthens and differentiates into nodes and internodes.

The escape- a complex organ consisting of a stem, leaves, and buds. The stem has nodes and internodes. Knot- the section of the stem on which the leaf and bud are located. The area of ​​the stem between the nodes is internode. The angle formed by the leaf and the stem above the node is called leaf sinus. Buds occupying a lateral position on a node are called lateral (or axillary). At the top of the stem there is an apical bud.

Escape modifications can perform various functions: storage and vegetative propagation (tubers, rhizomes, bulbs), protective (spines), serve as an attachment organ (antennae), etc.

• Tubers- shortened and thickened underground shoots with buds (potatoes).
• Rhizome- an underground shoot that resembles a root, bears scale-like leaves and buds, and often forms above-ground shoots and adventitious roots (wheatgrass).
• Bulb- a shortened stem (bottom), surrounded by succulent leaves (onion).
• spines- means of protection (wild apple tree).
• Mustache- means of attachment (grapes).

SHEET

Sheet- flat lateral organ of the shoot.

External leaf structure. In dicotyledonous plants, the leaf consists of a flat, expanded blade and a stem-like petiole with stipules. The leaves of monocotyledonous plants are characterized by the absence of petioles; the base of the leaf is expanded into a sheath that encloses the stem. In cereals, the vagina covers all internodes: The leaves of dicotyledonous plants are simple and complex. Simple leaves have one leaf blade, sometimes strongly divided into lobes. Compound leaves have several leaf blades with pronounced cuttings. Pinnate leaves have an axial petiole, on both sides of which there are leaflets. Palmate leaves have leaflets fanning out from the top of the main petiole.

Internal structure of the leaf. On the outside of the leaf there is a skin of colorless cells, covered with a wax-like substance - cuticle. Located under the skin cells columnar parenchyma containing chlorophyll. Deeper are the cells of spongy parenchyma with intercellular spaces filled with air. The parenchyma contains the vessels of the vascular bundle. On the lower surface of the leaves, the skin has stomatal cells involved in the evaporation of water. Evaporation of water occurs to prevent overheating of the leaf through the stomata of the epidermis (skin). This process is called transpiration and ensures a constant flow of water from the roots to the leaves. Transpiration rate depends on humidity air, temperature, light, etc.

Under the influence of these factors, the turgor of the guard cells of the stomata changes, they close or close, delaying or increasing the evaporation of water and gas exchange. During the process of gas exchange, oxygen is supplied to cells for respiration or released into the atmosphere during photosynthesis.

Cellular structure of the leaf.

Leaf modifications: tendrils - serve to secure the stem in a vertical position; needles (of cactus) play a protective role; scales - small leaves that have lost their photosynthetic function; catching apparatus - the leaves are equipped with columnar glands that secrete mucus, which is used to capture small insects that fall on the leaf.

STEM

The stem is the axial part of the shoot, bearing leaves, flowers, inflorescences and fruits. This is the supporting function of the stem. Other functions of the stem include; transport - carrying water with substances dissolved in it from the root to the ground organs; photosynthetic; storage - deposition of proteins, fats, carbohydrates in its tissues.

Stem tissues:

1. Conductive: the inner part of the bark consists of sieve tubes and companion cells of the phloem; wood cells (xylem) are located closer to the center, through which the transport of substances.
2. Pokrovnaya- skin on young stems and cork on old woody stems.
3. Storage- specialized cells of bast and wood.
4. Educational(cambium) - constantly dividing cells that supply attack to all tissues of the stem. Due to the activity of cambium the stem grows in thickness, and tree rings are formed.

Modifications of stems: tuber - storage underground shoot; the entire mass of the tuber consists of storage parenchyma together with conductive tissue (potato); bulb - a shortened conical stem with numerous modified leaves - scales and a shortened stem - bottom (onion, lily); corms (gladiolus, crocus, etc.); head of cabbage - a greatly shortened stem with thick, overlapping leaves.

Cellular structure of the stem:

BUD

Bud- a rudimentary shortened shoot from which new shoots (vegetative buds) or flowers (generative buds) can develop. New shoots grow from the bud in the spring. There are apical, axillary, (located in the axils of the leaves) and accessory buds. Accessory buds are formed due to the activity of the cambium and other educational tissues in different places - on the roots, stems, leaves.

Vegetative bud consists of a shortened stem and rudimentary leaves; sometimes covered with protective modified leaves - bud scales. There are apical and lateral (axillary) vegetative buds. The apical bud is located at the top of the stem and consists of cells of the growth cone and ensures the growth of the shoot in length, as well as the formation of leaves and lateral buds. Lateral buds are formed in the axils of the leaves. With the help of phytohormones that are formed in the apical bud, the growth and development of lateral (dormant) buds, which begin to grow only when the apical bud is damaged or dies, is inhibited.

Generative buds larger than vegetative ones; they bear fewer rudimentary leaves, and at the top of the rudimentary stem are the rudiments of a flower or inflorescence. The generative bud containing one flower is called a bud. Adventitious buds can form on the internodes of the stem, roots and leaves, allowing for vegetative propagation.