The first shoot of the plant is formed from the embryonic bud - its main escape, or first order escape.

From the main shoot they form side shoots, or second order shoots, and when repeating branching - third order, etc.

Adventitious shoots are formed from accessory buds.

This is how a system of shoots is formed, represented by the main shoot and lateral shoots of the second and subsequent orders. Escape system increases total area contact of the plant with the air.

Depending on the function performed, shoots are divided into vegetative, vegetative-generative and generative. Vegetative (unmodified) shoots, consisting of a stem, leaves and buds, and vegetative-generative (partially modified) shoots, additionally consisting of a flower or inflorescence, perform the functions air supply and provide the synthesis of organic and inorganic substances. In generative (completely modified) shoots, photosynthesis most often does not occur, but sporangia are formed there, the task of which is to ensure the reproduction of the plant (the flower is one of these shoots).

The shoot on which flowers are formed is called flowering shoot, or peduncle(sometimes the term “peduncle” is understood in a narrower sense - as the section of the stem on which the flowers are located).

Main organs of the shoot

A vegetative unmodified shoot is a single plant organ, consisting of a stem, leaves and buds, formed from a common array of meristem (shoot growth cone) and possessing a single conducting system. Stems and leaves, which are the main structural elements of the shoot, are often considered as its constituent organs, that is, second-order organs. In addition, a mandatory accessory to the shoot is the buds. home external feature What distinguishes a shoot from a root is the presence of leaves.

Monopodial branching

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. The monopodial type of branching is often found among gymnosperms, and is also found in many angiosperms (for example, in many types of palms, as well as plants from the Orchid 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.

Sympodial branching

In plants with a sympodial type of shoot structure, the apical bud, having completed development, dies or gives rise to generative I'll run. 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; sympodial branching is an evolutionarily more advanced type of branching. The word “sympoidal” is derived from the Greek. sym(“together” or “many”) and pod("leg").

Sympodial branching is characteristic of many angiosperms: for example, for lindens, willows and many orchids.

In orchids, in addition to apical ones, some sympodial orchids also form lateral inflorescences, developing from buds located at the base of the shoot (Pafinia comb). The part of the shoot pressed to the substrate is called the rhizome. It is usually located horizontally and does not have true leaves, only scale-like ones. A reduced, almost indistinguishable rhizome occurs in many masdevallias, dendrobiums and oncidiums; clearly distinguishable and thickened - in cattleyas and laelias, elongated - in bulbophyllums and coelogines, reaching 10 or more centimeters. The vertical part of the shoot is often thickened, forming the so-called tuberidium, or pseudobulb. Pseudobulbs can be various shapes- from almost spherical to cylindrical, cone-shaped, club-shaped and elongated, reminiscent of reed stems. Pseudobulbs are storage organs.

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.

Bulbophyllum grandiflorum

Cirrhopetalum macraei. Curtis's botanical magazine vol. 127 ser. 3 nr. 57 tab. 7787, 1901

Oncidium dasystyle. Curtis's botanical magazine vol. 127 ser. 3 nr. 57 tab. 7787, 1901

Dendrobium senile. Curtis's botanical magazine vol. 127 ser. 3 nr. 57 tab. 7787, 1901

Evolution of branching types

Modifications of shoots (metamorphoses)

Escape is the most changeable appearance plant organ. This is due not only to the general multifunctionality of vegetative organs that arose in the process of evolution, but also to changes occurring during plant ontogeny, due to adaptation to a variety of conditions environment, and cultivated plants- under human influence.

The main type of shoot of a green plant is an above-ground (aerial) assimilating shoot, bearing green leaves of the middle formation on its axis. However, assimilating shoots are not the same. Often, along with the main function of photosynthesis, these shoots also have others: deposition of reserves and support function (mostly in perennial stems), vegetative propagation (creeping shoots, lashes).

Modification of underground shoots

Shoots living underground, under the influence of a set of conditions that are sharply different from the terrestrial environment, almost completely lost the functions of photosynthesis and acquired other equally important vital functions, such as organs for surviving unfavorable periods, storing nutrients, vegetative regeneration and plant reproduction. Underground modified shoots include: rhizome, caudex, underground stolon and tuber, bulb, corm.

Caudex- a perennial organ of shoot origin of perennial grasses and subshrubs with a well-developed taproot that persists throughout the life of the plant. Together with the root, it serves as a place for the deposition of reserve substances and bears many renewal buds, some of which may be dormant. There are many caudex plants among the umbelliferous (femoral, ferula), legumes (alfalfa, lupins), and Asteraceae (dandelion, wormwood, rough cornflower).

underground stolon- annual elongated thin underground escape with underdeveloped scale-like leaves. At the thickened ends of stolons, plants can accumulate reserve substances, forming tubers or bulbs (potatoes, rosemary, adoxa).

Stem tuber- a modified shoot with a pronounced storage function of the stem, the presence of scale-like leaves that quickly peel off, and buds that form in the axils of the leaves and are called eyes (potatoes, Jerusalem artichokes).

Bulb- an underground (less often above-ground) highly shortened specialized shoot, in which reserve substances are deposited in leaf scales, and the stem is transformed into a bottom. The bulb is a typical organ of vegetative renewal and reproduction. Bulbs are characteristic of monocotyledonous plants from the family Liliaceae (lily, tulip, onion), Amaryllidaceae (amaryllis, narcissus, hyacinth), etc. As an exception, they are also found in dicotyledons - in some species of sorrel and butterwort.

Corm- a modified underground shortened shoot with a thick stem storing assimilates, adventitious roots growing from the underside of the corm, and preserved dried leaf bases (membranous scales), which together constitute a protective cover. Corms include saffron, gladiolus, and colchicum.

Modifications of aboveground shoots

An unusual lifestyle and/or adaptations to the special conditions of existence of plants lead to various modifications of shoots. In this case, shoots can serve not only for storing nutrients, reproduction and propagation of plants, but also perform other functions. There are frequent cases when not the entire shoot is modified, but only its leaves, and some of their metamorphoses are externally and functionally similar to the metamorphoses of the shoot (spines, tendrils).

Thorn- a highly lignified, leafless, shortened shoot with a sharp tip. The spines of shoot origin perform mainly a protective function. The wild apple, wild pear, laxative buckthorn ( Rhamnus cathartica) shortened shoots that have limited growth and end with a point turn into spines. In honey locust ( Gleditschia triacanthos) powerful branched spines are formed on the trunks from dormant buds. Many hawthorn species have spines that form from the axillary buds of the leaves, which topographically correspond to the lateral shoots.

Cladodius- a modified lateral shoot with the ability for long-term growth, with green, flat, long stems that perform the functions of a leaf. As an organ of photosynthesis, the cladodium has well-developed chlorophyll-bearing tissue located under the epidermis. Plants with cladodes include Mühlenbeckia planiflora ( Muhlenbekia platyclada), Decembrist cactus ( Zygocactus truncates), carmichelia southern ( Carmichaelia australis), collection ( Colletia cruciata) and prickly pear ( Opuntia).

Phyllocladium- a modified leaf-shaped flattened lateral shoot that has limited growth and performs the functions of a leaf. Phyllocladia develop from lateral buds, so they are always found in the axil of a small filmy or scale-like leaf. Performing the function of photosynthesis, phyllocladian shoots also externally acquire a resemblance to a leaf, which is manifested in limited growth and complete loss of metameric structure. The phenomenon of phylloclady is characteristic of plants such as butcher's broom, moss, and species of the genera asparagus ( Asparagus), phyllanthus ( Phyllanthus). Phyllocladies are found not only in angiosperms, but also in some gymnosperms, in particular in coniferous plant from the family Legocladaceae - phyllocladus.

Notes

Literature

  • Korovkin O. A. Anatomy and morphology higher plants: dictionary of terms. - M: Bustard, 2007. - 272 p. - ISBN 978-5-358-01214-1
  • Nukhimovsky E. L. Fundamentals of biomorphology of seed plants: Habitus and growth forms in the organization of biomorphs. - M: Overley, 2002. - T. 2. - 859 p. - 750 copies. - ISBN 5-85493-067-6
  • Botany with basics of phytocenology: Anatomy and morphology of plants: Textbook. for universities / Serebryakova T. I. et al. - M: ICC "Akademkniga", 2007. - P. 341-365. - 2,000 copies. - ISBN 978-5-94628-237-6
  • Timonin A.K. Botany: in 4 volumes - M: Publishing Center "Academy", 2007. - T. 3. - P. 52-69. - 3,000 copies. - ISBN 978-5-7695-3184-2
  • Botany. Textbook for universities: in 4 volumes. T. 1. Cell biology. Anatomy. Morphology. Based on the textbook by E. Strasburger / Ed. A. K. Timonina, V. V. Chuba. - M: Publishing center "Academy", 2007. - T. 1. - P. 261-266. - 3,000 copies. - ISBN 978-5-7695-2744-9
  • Lotova L. I. Botany: Morphology and anatomy of higher plants: Textbook. - M: KomKniga, 2007. - P. 312-321. - 1,500 copies. - ISBN 978-5-484-00698-4
  • Barabanov E.I., Zaichikova S.G. Botany: textbook. for students universities - M: Publishing Center "Academy", 2006. - P. 82-85. - 3,000 copies. - ISBN 5-7695-2656-4
  • Yakovlev G. P., Chelombitko V. A. Botany: textbook. for students universities - St. Petersburg: Spetslit, publishing house SPHFA, 2003. - P. 129-132. - 5,000 copies. - ISBN 5-299-00237-8
  • Andreeva I. I., Rodman L. S. Botany. - M: KolosS, 2005. - P. 172-175. - 3,000 copies. - ISBN 5-9532-0114-1
  • Tropical and subtropical plants. Funds of the Main botanical garden Academy of Sciences of the USSR (Cactaceae-Compositae). M.: Nauka, 1976.
  • Smirnova E.S. Morphology of orchid shoot systems. – M.: Nauka, 1990
Theory for preparation for block No. 4 of the Unified State Exam in biology: with system and diversity of the organic world.

Root

Root- an underground vegetative organ of higher plants with unlimited growth in length.

Root functions

  1. Fixing the plant in the substrate
  2. Suction, conduction of water and minerals
  3. Nutrient supply
  4. Interaction with the roots of other plants, fungi, microorganisms living in the soil (mycorrhiza, legume nodules)
  5. Vegetative propagation
  6. Synthesis of biologically active substances
  7. In many plants, the roots perform special functions (aerial roots, sucker roots)
  8. Modifications and specialization of roots
  9. The roots of some buildings have a tendency to metamorphose

The roots are different, namely, they can change.

Root modifications

  • Root vegetable - a modified succulent root. The main root and Bottom part stem. Most root plants are biennial. Root vegetables consist mainly of storage tissue (turnips, carrots, parsley).
  • Root tubers - root tubers (root cones) are formed as a result of thickening of lateral and adventitious roots (tulips, dahlias, potatoes).
  • Aerial roots are lateral roots that grow downwards. Absorb rainwater and oxygen from the air. Formed in many tropical plants in conditions of high humidity.
  • Mycorrhiza is the cohabitation of the roots of higher plants with fungal hyphae. With this mutually beneficial cohabitation, called symbiosis, the plant receives water with nutrients dissolved in it from the fungus, and the fungus receives organic matter. Mycorrhiza is characteristic of the roots of many higher plants, especially woody ones. Fungal hyphae, entwining the thick lignified roots of trees and shrubs, perform the functions of root hairs.
  • Bacterial nodules on the roots of higher plants - the cohabitation of higher plants with nitrogen-fixing bacteria - are modified lateral roots adapted to symbiosis with bacteria. Bacteria penetrate through the root hairs into young roots and cause them to form nodules.
  • Respiratory roots - in tropical plants - perform the function of additional respiration.


There are:

  • main root
  • lateral roots
  • adventitious roots

The main root develops from the embryonic root. Lateral roots occur on any root as a side branch. Adventitious roots are formed by the shoot and its parts.

The collection of roots of one plant is called the root system.

Types of root systems

  • Rod
  • fibrous
  • Branched

IN core In the root system, the main root is highly developed and clearly visible among other roots (characteristic of dicotyledons). Rod root system usually penetrates deeper into the soil than fibrous.

IN fibrous In the root system, in the early stages of development, the main root, formed by the embryonic root, dies, and the root system is composed of adventitious roots (typical of monocots). The fibrous root system better entwines adjacent soil particles, especially in its upper fertile layer.

IN branchy The root system is dominated by equally developed main and several lateral roots (in tree species, strawberries).


The escape

The escape- This is a stem with leaves and buds located on it.

The components of the shoot are the stem, leaves, and buds. When a seed germinates from the embryonic bud, the first shoot of the plant is formed - its main shoot, or shoot of the first order. From the main shoot, side shoots, or shoots of the second order, are formed, and when branching is repeated - of the third order, etc. Additional shoots are formed from adventitious buds.

This is how a system of shoots is formed, represented by the main shoot and lateral shoots of the second and subsequent orders. The shoot system increases the total area of ​​contact of the plant with the air.

The shoot on which flowers are formed is called a flowering shoot, or peduncle (sometimes the term “peduncle” is understood in a narrower sense - as the section of the stem on which the flowers are located).

A vegetative unmodified shoot is a single plant organ, consisting of a stem, leaves and buds, formed from a common array of meristem (shoot growth cone) and possessing a single conducting system. Stems and leaves, which are the main structural elements of the shoot, are often considered as its constituent organs, that is, second-order organs. In addition, a mandatory accessory to the shoot is the buds. The main external feature that distinguishes a shoot from a root is the presence of leaves.

In seasonal climate temperate latitudes the growth and development of shoots from the buds is periodic. In shrubs and trees, as well as in most perennial grasses, this happens once a year - in spring or early summer, after which the wintering buds of the next year are formed, and at the end of summer - in the fall, shoot growth ends.

Escape structure


A (with leaves). 1 - stem; 2 – sheet; 3 – node; 4 - internode; 5 – leaf axil; 6 – axillary bud; 7 – apical bud.

B (after leaf fall). 1 – apical bud; 2 – kidney rings; 3 – leaf scars; 4 - lateral buds.

Types of shoots


1 – erect; 2 – rising; 3 – creeping; 4 – creeping; 5 – curly; 6 – climbing.

Modifications of shoots

  • The thorn is a highly lignified, leafless, shortened shoot with a sharp tip. The spines of shoot origin perform mainly a protective function. In wild apple, wild pear, and laxative buckthorn (Rhamnus cathartica), shortened shoots that have limited growth and end in a point turn into thorns.
  • A tendril is a rope-like branched or unbranched shoot of a metameric structure, typically devoid of leaves. Stem tendrils, as a highly specialized shoot, perform a supporting function.
  • Rhizome is an underground shoot with scale-like leaves of the lower formation, buds and adventitious roots. Thick, highly branched creeping rhizomes are characteristic of wheatgrass, short and rather fleshy - for kupena, iris, very thick - for egg capsule, water lily.
  • A stem tuber is a modified shoot with a pronounced storage function of the stem, the presence of scale-like leaves that quickly peel off, and buds that form in the axils of the leaves and are called eyes (jerusalem artichoke).
  • A bulb is an underground (less often above-ground) highly shortened specialized shoot, in which reserve substances are deposited in leaf scales, and the stem is transformed into a bottom. The bulb is a typical organ of vegetative renewal and reproduction. Bulbs are characteristic of monocotyledonous plants from the family Liliaceae (lily, tulip, onion), Amaryllidaceae (amaryllis, narcissus, hyacinth), etc. As an exception, they are also found in dicotyledons - in some species of sorrel and butterwort.
  • A corm is a modified underground shortened shoot with a thick stem that stores assimilates, adventitious roots growing from the underside of the corm, and preserved dried leaf bases (membranous scales), which together constitute a protective cover. Corms include colchicum, gladiolus, ixia, and saffron.

Stem

Stem- an elongated shoot of higher plants, serving as a mechanical axis, also serves as a producing and supporting base for leaves, buds, and flowers.

Classification of stems

By location relative to soil level:

above ground

underground

According to the degree of lignification:

  • herbaceous
  • woody (for example, a trunk is the main perennial stem of a tree; the stems of shrubs are called stems)

By direction and nature of growth:

  • erect (for example, sunflower)
  • recumbent (creeping) - stems lie on the surface of the soil without rooting (monetary loosestrife)
  • ascending (ascending) - the lower part of the stem lies on the surface of the soil, and the upper rises vertically (cinquefoil)
  • creeping - stems spread along the ground and take root due to the formation of adventitious roots at the nodes (ivy budra)
  • clinging (climbing) - attached to a support using antennae (peas)
  • climbing - thin stems wrapping around a support (lunasperium)

According to cross-sectional shape:

  • rounded
  • flattened
  • three-, four-, polyhedral (faceted)
  • ribbed
  • grooved (grooved)
  • winged - stems in which flat herbaceous outgrowths stretch along sharp edges (forest phylum) or leaf bases descending onto the stem (comfrey)

Stem structure

Outside, the stem is protected by integumentary tissues. In young stems in spring, the cells of the integumentary tissue are covered with a thin skin. In perennial plants, by the end of the first year of life, the skin is replaced by a multilayer plug consisting of dead cells filled with air. For respiration, the skin (of young shoots) has stomata, and later lentils are formed - large, loosely located cells with large intercellular spaces.

Adjacent to the integumentary tissue is a cortex formed by different tissues. The outer part of the cortex is represented by layers of mechanical tissue cells with thickened membranes and thin-walled cells of the main tissue. The inner part of the cortex is formed by cells of conducting tissue and is called the bast.

The bast consists of sieve tubes through which a downward current flows: organic substances move from the leaves. Sieve tubes consist of cells connected at their ends into a long tube. There are small openings between adjacent cells. Organic substances formed in the leaves move through them, like through a sieve.

Sieve tubes do not remain alive for long, usually 2-3 years, occasionally - 10-15 years. New ones are constantly being formed to replace them. Sieve tubes form a small part in the phloem and are usually collected in bundles. In addition to these bundles, the bast contains cells of mechanical tissue, mainly in the form of bast fibers, and cells of the main tissue.

To the center of the bast in the stem there is another conductive tissue - wood.

Wood is formed by cells of different shapes and sizes and consists of vessels (tracheas), tracheae and wood fibers. An upward current flows through them: water with substances dissolved in it moves from the roots to the leaves.

In the center of the stem lies a thick layer of loose cells of the main tissue, in which reserves of nutrients are deposited - this is the pith.

In some plants (dahlia, tulip, cucumber, bamboo), the core is occupied by an air cavity.

Between the wood and the bast of dicotyledonous plants there is a thin layer of educational tissue cells - the cambium. As a result of the division of cambium cells, the thickness of the stem increases (grows). Cambium cells divide along their axis. One of the daughter cells that appears goes to the wood, and the other goes to the bast. The increase is especially noticeable in wood. The division of cambium cells depends on the seasonal rhythm - in spring and summer it is active (large cells are formed), in autumn it slows down (small cells are formed), and in winter it stops. As a result, an annual growth of wood is formed, clearly visible in many trees, called an annual ring. By the number of growth rings, you can calculate the age of the shoot and the tree as a whole.

Width of tree rings woody plants depends on environmental conditions. Thus, in cold climates, on marshy soils, the size of the annual rings of wood is very small. In favorable climatic conditions, on rich soils the thickness of tree rings increases. By comparing the alternation of wide and narrow growth rings near the trunk, it is possible to determine in what conditions the plant lived, as well as to establish fluctuations weather conditions for many years.


Functions of the stem

  • conductive (main function)

The stem serves as a support for the plant; it bears the weight of the leaves, flowers and fruits on it.

  • supporting

Spare nutrients may be deposited in the stem. This shows the storage function of the stem. With the help of the stem, the shoot brings its leaves and buds to the light during the growth of the plant. This reveals the important axial function of the stem and the growth function.

Sheet

Sheet- one of the most important organs of plants, the main functions of which are photosynthesis, gas exchange and transpiration.

Internal structure of the leaf

The sheet consists of the following fabrics:

  • The epidermis is a layer of cells that protect against the harmful effects of the environment and excessive evaporation of water. Often, on top of the epidermis, the leaf is covered with a protective layer of waxy origin (cuticle).
  • Parenchyma is an internal chlorophyll-bearing tissue that performs the main function of photosynthesis.
  • A network of veins formed by conducting bundles consisting of vessels and sieve tubes for the movement of water, dissolved salts, sugars and mechanical elements.
  • Stomata are special complexes of cells located mainly on the lower surface of leaves; Through them, water evaporation and gas exchange occur.


External leaf structure

The leaf externally consists of:

  • petiole (leaf stalk)
  • leaf blade (blade)
  • stipules (paired appendages located on both sides of the base of the petiole)
  • the place where the petiole joins the stem is called the leaf sheath
  • the angle formed by the leaf (leaf petiole) and the overlying internode of the stem is called the leaf axil
  • in the leaf axil a bud (which in this case is called an axillary bud), a flower (called an axillary flower), an inflorescence (called an axillary inflorescence) can form.

Not all plants have all parts of leaves; in some species, paired stipules are not clearly expressed or are absent; the petiole may be missing, and the leaf structure may not be lamellar.


The escape- this is a part of a plant consisting of a stem and leaves and buds located on it. Instead of leaves or together with them, flowers or inflorescences may develop on the shoot.

In the process of evolution, shoots arose when plants began to grow on land. That is, shoots are characteristic of all living higher plants. U lower plants, which are algae, there are no shoots, since their entire body is not differentiated into organs and is called a thallus (or thallus).

All shoots develop from buds. But the first shoot of the plant develops from the embryonic bud. Such an escape is called the main one. The main escape is a first order escape. From the buds growing on it, shoots of the second order develop, on which shoots of the third order can grow, etc.

An extensive shoot system helps the plant capture more sunlight and the process of photosynthesis proceeded more efficiently in it. That is, the shoot system provides air nutrition to the plants.

On the stem of the shoot, the buds are usually located in nodes, and one bud is located at the top of the shoot. The first ones are called axillary, and the second - apical. However, sometimes buds can grow on internodes, leaves, and roots. This accessory buds.

Axillary buds grow in the leaf axils. But if the leaf has already fallen, then the bud is on the stem without a leaf, only the remaining leaf scar is visible under it.

On the stem of the shoot, the buds have the same arrangement as the leaves. If the leaves are arranged alternately, then the buds (birch, hazel) will also be arranged. If the arrangement of the leaves is opposite, then there will be two buds in each node (lilac, elderberry).

The appearance of the buds and their location on the shoot are characteristic features, by which the type of plant can be determined.

The buds of almost all plants are covered on the outside with modified leaves - kidney scales. Their function is to protect the internal parts of the kidney from mechanical damage and drying out. However, there are plants (for example, buckthorn) whose buds do not have scales. Such buds are called naked.

What is inside the kidney depends on its type. U vegetative buds there is a rudimentary stem with rudimentary leaves and rudimentary buds. In other words, a vegetative bud is a rudimentary vegetative shoot. Inside generative buds the rudimentary stem contains rudimentary buds, and rudimentary leaves may also be present. Generative buds are also called flower buds. From them a flowering shoot with a flower or inflorescence develops.

Typically, generative buds are somewhat larger than vegetative ones and more round.

The organs of flowering plants, the most evolutionarily developed representatives of this kingdom of living nature, have a fairly diverse structure and functions. The underground part of the plant is called the root, the above-ground part is the shoot. It is the plant shoot that carries out the most important functions: gas exchange, photosynthesis, transpiration, vegetative propagation and its optimal location in relation to the sun.

Origin of the escape

In the process of evolution, this organ appears in the first inhabitants of land - rhinophytes. Its stems were creeping and forked because they were still poorly developed. But even with such a primitive structure, the photosynthetic surface increased, which means that the plant organism was better provided with carbohydrates.

in plants

A shoot is the above-ground part of a plant, consisting of a stem and leaves. All these organs are vegetative, providing growth, nutrition and asexual reproduction.

The plant shoot also contains rudimentary organs - buds. There are two types of buds: vegetative and generative. The first type consists of a rudimentary stem and leaf, on top of which there is a growth cone represented. If, in addition to the stem and leaves, the bud contains the rudiments of flowers or inflorescences, it is called generative. By appearance Such buds are distinguished by their larger size and rounded shape.

The place to which a leaf is attached on the stem is called a node, and the distance between the nodes is called an internode. The angle between the stem and the leaf is called the axil.

During the development process, organs responsible for generative (sexual) reproduction also appear on the shoot: flower, fruit and seed.

Development of a shoot from a bud

With the onset of favorable conditions in the spring, the cells of the meristem begin to actively divide. Shortened internodes increase in size, resulting in the appearance of young plant shoots. At the very top of the stem there are apical buds. They ensure the plant grows in length. Axillary and adventitious buds are located in the leaf axil or on the internode, respectively. Due to them, the stem forms lateral shoots, i.e., branches.

Plant branching methods

Depending on the structure, there are several ways to branch shoots:

  1. Dichotomous. Most primitive type branching, in which two growth points develop from one point of growth, from each of them two also develop, etc. This is how some algae and higher spore plants grow: mosses and ferns.
  2. Primopodial. Such branching can be seen both in gymnosperms (pine, spruce) and (oak, maple). For a long time, the plants grew in length with the subsequent formation of lateral branching.
  3. Sympodial. With this method, apical growth, on the contrary, stops. And the side buds are actively growing, forming more and more side shoots. Pear, cherry and other flowering plants are typical examples of this type of growth.

Modifications of shoots

Everyone certainly knows what a plant shoot is and what it looks like. But environmental conditions often require the appearance additional functions. This is easily provided by the organs of flowering plants. The shoot changes, acquiring new structural features, while consisting of parts of a standard shoot.

The main modifications of the escape include:

  • Rhizome - located underground, where it most often grows horizontally. It has elongated internodes and buds, of which on the surface of the earth in favorable period leaves appear. Therefore, plants with rhizomes (lily of the valley, wheatgrass, valerian) are very difficult to get rid of. After tearing off the leaves, the shoot itself remains in the ground, growing more and more.

  • A tuber is a thickened internode with buds - eyes. The most prominent representative The plants that form tubers are potatoes. Because it grows in the ground, it is often confused with a modified root. However, there are also above-ground tubers, for example, kohlrabi.
  • A bulb is a modified shoot of plants with well-developed leaves located on a flat stem - the bottom. Typical for garlic, onion, tulip, lily. Nutrients accumulate in the succulent inner leaves, and the dry outer leaves protect them from damage.
  • Thorns are a protective device of pear, sea buckthorn, hawthorn and other plants. Being in the leaf axil, they reliably protect the plant from animals that want to feast on it.
  • Tendrils are modified climbing shoots that fix plants in a certain position. Cucumber, grapes, pumpkin are the most common plants that use this device.

  • Whiskers are thin shoots with long internodes. Strawberries and wild strawberries reproduce vegetatively with the help of whiskers.

As you can see, a plant shoot consists of parts that are functionally interconnected, can change depending on environmental conditions and give each plant its own unique appearance.

The escape- this is an unbranched stem with leaves and buds located on it - the rudiments of new shoots that arise in a certain order. These primordia of new shoots ensure the growth of the shoot and its branching.

Shoots are vegetative and spore-bearing

The functions of vegetative shoots include: the shoot serves to strengthen the leaves on it, ensures the movement of minerals to the leaves and the outflow of organic compounds, serves as a reproductive organ (strawberry, currant, poplar), serves as a storage organ (potato tuber)

Spore-bearing shoots perform the function of reproduction.

The structure of the shoots:

A bud is an embryonic shoot that produces shoots and leaves

The leaf is a flat lateral organ extending from the stem that performs the function of photosynthesis and gas exchange.

Leaf axil is the angle between the leaf and the stem.

The node is where the leaf leaves the stem

Internode - the area of ​​the stem between adjacent nodes

The root collar is the transition point between the root and the stem.

Types of shoots

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

Main escape- a shoot developed from the bud of a seed embryo.

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

Extended escape- shoot, with elongated internodes.

Shortened escape- shoot with shortened internodes.

Vegetative shoot- a shoot bearing leaves and buds.

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

In the direction of growth relative to the surface:

Orthotropic (erect)

Plagiatropic (growing parallel to the soil)

Along the length of internodes:

With elongated internodes (typical shoot)

With shortened internodes (root branch of strawberry leaves)

According to the location of the shoots in space:

Erect

Curly

Clinging

Creeping

Creeping

Branching- this 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..

Monopodial- growth occurs due to the apical bud

Sympodial- shoot growth continues at the expense of the nearest lateral bud

False dichotomous- after the apical bud dies, shoots grow (lilac, maple)

Dichotomous - from the apical bud two lateral buds are formed, giving two shoots

Tillering - This is branching in which large lateral 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.