Vegetative organs of flowering plants. Root

The concept of plant organs

Definition 1

Organ A part of a plant organism adapted to perform one or more functions.

In plants, two groups of organs interconnected into an integral system are distinguished - vegetative and generative.

The vegetative ones include the root and shoot, consisting of a stem, leaves and buds, and the generative ones include a flower, fruit and seed (in spores it is sporangia, in gymnosperms it is a cone).

Vegetative organs of plants

Definition 2

Vegetative organs (from Latin vegetativas - plant) in plants are those that support the basic life processes, that is, perform the main functions of its nutrition and metabolism with the environment.

These organs were formed as a result of the dismemberment of a homogeneous body of lower plants (algae) - thalom. The reason for this was the transition from aquatic to terrestrial way of life.

One of the common features of vegetative organs is their polarity. Each organ has two poles: the upper, or apical, and the lower, or main. Vegetative organs are able to orient themselves in space in a certain way: the root always grows towards the center of the Earth (positive geotropism), the stem - from the center of the Earth (negative geotropism). The axial organs - the stem and root - are located vertically to the Earth's surface (orthotropic organs), and the leaves are at an angle (plagiotropic organs). This specialization is due to two areas of plant nutrition (soil and atmospheric), which means a two-way flow of water with dissolved mineral and organic substances.

The root has unlimited growth, has no leaves. Provides absorption and transportation of water and compounds dissolved in it, synthesis (and often storage) of substances, respiration.

Stem in typical cases - an axial polysymmetrical organ of unlimited growth. The stem provides a connection between the leaves and roots, promotes the formation of a strong assimilation surface of the leaves and their best placement relative to the light, and stores nutrients.

Sheet- a lateral organ of limited growth, grows by the base by intercalary growth (in monocots) or by the entire surface (in dicots). The leaf consists of a leaf blade and petiole, stipules; leaves without a petiole are called sessile (rye). In annual plants, the life span of a leaf is similar to the life span of a stem. Trees and bushes have a temporary organ. The main functions of the leaf: photosynthetic, gas exchange, transpiration, reproduction, protective (thorns), cleansing (leaf fall), nutritious (dew).

Remark 1

Vegetative organs do not take part in sexual reproduction, but still they can contribute to the so-called vegetative method of plant propagation (using rhizomes, tuber bulbs, mustaches, etc.). With this method of reproduction, a new organism grows from the multicellular part of the mother organism.

The division of the body of plants into organs and the formation of a large number of branches, leaves and roots made it possible to develop a huge photosynthetic surface and absorb a sufficient amount of water and mineral elements.

plant generative organs

Definition 3

Generative (reproductive) organs(from lat. genero - give birth) plants arose much later than vegetative ones. The flower, the seed and the fruit that are formed from it, are considered the highest achievement of the process of reproduction in the plant world. Thanks to the generative organs, the process of sexual reproduction is ensured.

The generative organs of flowering plants are flowers, due to which fruits with seeds are formed. The process of sexual reproduction of flowering plants occurs when the plant blooms (flowers open).

In shape, size, color and structural features, flowers are very diverse. However, the basic structure and processes of flower development are identical in all plants. The flower has stamens, pistils and perianth (petals and calyx). The main function of the stamens is the formation of pollen grains with male sex cells (sperms). In the pistils are the seed rudiments, and in them are the female sex cells (ova).

As a result of fertilization, a seed is formed from the seed germ, inside of which there is an embryo and endosperm under the skin. The seeds are surrounded by a pericarp, which was formed from the walls of the ovary. Together, the seeds and the pericarp form the fruit. After a dormant period, the seeds germinate under favorable conditions and a young plant develops from them.

Remark 2

The generative organs of spore plants - mosses, horsetails, ferns - have a different structure.

Vegetative and generative organs of plants.pptx

All plant organisms have common features, both distinguishing them from representatives of other kingdoms of the organic world, and bringing them closer to them. The hallmarks of the plant kingdom are as follows:

- relative immobility of the organism and its connection with the substrate;

- the presence of plastids - chloroplasts, chromoplasts and leukoplasts in cells;

– branching of the absorbing surface of the body;

- constant growth;

- manifestation of irritability;

- the presence of a cellulose cell membrane;

- the ability to photosynthesis - autotrophic nutrition.

Brings together plant organisms with representatives of other kingdoms of wildlife cellular structure, general mechanisms of growth, development, reproduction, metabolism.

Plants are capable of photosynthesis due to the presence of chlorophyll in their green organs, stems of young and herbaceous plants, and leaves. By accumulating organic matter in the process of photosynthesis, plants create the main biomass reserve on planet Earth, i.e. are producers. Oxygen released by plants during photosynthesis serves as a source of aerobic respiration and forms the ozone layer of the atmosphere.

Plants appeared on Earth about 2 billion years ago. Initially, the development of plant organisms took place in the aquatic environment, which led to the appearance of algae. Then the plants began to master the land. This was facilitated by the emergence of the following aromorphoses:

- the emergence of photosynthesis;

- the emergence of a eukaryotic structure of cells;

- occurrence of meiosis and fertilization;

- the emergence of multicellularity and differentiation of cells with the formation of tissues and organs;

– occurrence of alternation of haploid and diploid generations;

- the emergence of a seed;

- the emergence of a flower.

The evolution of plants went in the direction from spore to seed, from lower to higher. Lower plants do not have true tissues and organs. They occupy an aquatic habitat.

The body of higher plants is divided into vegetative and generative organs; they have conductive tissues and occupy three habitats: water, soil and air.

Tissues of higher plants

fabrics- These are stable complexes of cells, similar in structure, origin and functions. Prokaryotes and primitive algae do not have tissues. Cellular differentiation begins in brown algae and reaches its maximum in angiosperms. There are the following main groups of tissues: educational, basic, conductive, integumentary, mechanical, excretory.

Vegetative organs of flowering plants. Root

Organ is a part of the body, consisting of various tissues, having a certain shape and performing certain functions. Vegetative organs provide metabolism and plant growth. These include the root and shoot, consisting of a stem, leaves and buds.

Root –plant organ that performs the functions of fixing the plant in the soil, soil nutrition with water and minerals, storage of organic substances, vegetative propagation by underground parts.

The root is an axial organ with radial symmetry. The top of the root is covered root cap , under which there is an educational tissue that provides root growth.

Root types: main, lateral, accessory. The totality of all the roots of one plant forms root system. The root systems of dicotyledonous plants are usually rod , the root systems of monocotyledonous plants, as a rule, fibrous .

On a longitudinal section of a young root, 4 zones are visible:

– dividing zone, forming a cone root growth. This group of cells forms root cap cells and mucus that protect the root and facilitate its movement in the soil.

– root hair zone(suction zone) is formed by outgrowths of cells of the primary, single-layer suction tissue of the root;

Water transport from the soil to the root occurs passively, due to the difference in osmotic pressure between the cytoplasm of root hairs and aqueous solutions of the soil. And this pressure difference, in turn, is created actively, at the expense of energy consumption. From the cells of the suction zone, water rises into the conductive elements of the root as a result of an increase in osmotic pressure. In the vessels of the root, the pressure rises to 3 atmospheres. It is created by the expenditure of energy by the plant. Up the stem, water rises due to the evaporation of water in the leaves.

Many plants have modified roots: root crops (for radishes, radishes, beets, etc.), root tubers (for dahlias, sweet potatoes). The roots of many plants enter into symbiosis with fungi, forming mycorrhiza or fungal roots. The roots of leguminous plants enter into symbiosis with azotobacteria. As a result, nodules are formed. Bacteria fix atmospheric nitrogen and provide it to plants.

The escape

- opposite - two kidneys come out of one node;

- next - one kidney per node;

- whorled - 3 or more kidneys in one node;

- spiral - the kidneys are arranged in a spiral.

Shoot elements are formed from a common apical

educational tissue and have a single conducting system. Shoot formation is one of the largest aromorphoses that determined the emergence of plants on land.

Bud

- a shortened rudimentary shoot - consists of a rudimentary stem and rudimentary leaves (vegetative bud) or rudimentary flowers (generative bud). Buds that carry both leaves and flowers are called mixed.Apical budsprovide shoot growth in length,lateral(axillary) provide branching of the shoot. The buds that form on the leaves and in the internodes are called accessory buds. "dormant buds» develop after the death of the overlying buds, damage to plants. These buds provide plant regeneration. The kidneys may be protected by the scales of the kidneys and are then called closed. Kidneys without scales are called open.

Stem - axial vegetative organ with radial symmetry. Possesses apical growth. The main stem develops from the bud of the seed embryo. Stem functions: supporting, conducting, storage, photosynthetic, plant growth and branching, vegetative reproduction.

The structure of the stem. Stem grassy plants consists of the epidermis and the main tissue - parenchyma. It contains vascular fibrous bundles containing elements of xylem and phloem. In the stems of woody plants, the xylem and phloem are separated by the cambium. Cambium- this is an educational tissue that ensures the growth of the stem in thickness. On a cross section of such a stem, the following are visible: the core, wood with annual rings, cambium, bark. The cortex is the entire layer located outward from the cambium. The inner layer of the cortex, adjacent to the cambium, is formed by the bast or phloem.

By the nature of the direction of growth, the stems are divided into erect (pine), creeping (cucumber), clinging (meadow rank), climbing (creepers), climbing (bindweed).

Modified stems form rhizomes, tubers, bulbs.

Sheet - This is a lateral organ of a plant that has bilateral symmetry and provides the functions of photosynthesis, transpiration and gas exchange. The leaf consists of a leaf blade and a petiole. Depending on the number of leaf blades, leaves are simple (with one leaf blade on the petiole) and complex (with several leaf blades that have their own petioles). The shape of the leaves and their arrangement on the stem, type of venation are important systematic features.

1 - forked; 2 - pinnate; 3 - arc; 4 - parallel (veins run parallel along the entire leaf, from its base to the tip, which is typical for monocot plants such as grasses); 5 - palmate (several main veins diverge radially near the base of the petiole, for example, in a maple)

Leaves that do not have a petiole are called sessile. Leaves with petioles - petiolate.

The leaf is covered with epidermis on both sides. On the underside of the leaf are stomata that provide gas exchange and transpiration. In aquatic plants, stomata are located on the upper side of the leaf. The flesh of the leaf is called parenchyma or mesophyll.

The leaf skeleton is formed by vascular fibrous bundles and mechanical tissue. Through the petiole, the conducting elements of the leaf are connected to the stem. By the nature of the arrangement of the veins, there are leaves with reticulate, arcuate and parallel venation. Reticulate venation is most characteristic of dicotyledonous plants, arcuate and parallel - for monocots.

Photosynthesis takes place in columnar And spongy parenchymal tissues. Columnar tissue adjoins the upper skin, and spongy - to the lower.

Depending on the habitat, the leaves have developed various adaptations. In plants of arid places, adaptation is associated with a decrease in evaporation and the accumulation of moisture reserves. In plants in wet habitats, adaptations are associated with increased transpiration.

Depending on the nature of the adaptations, leaf modifications arose: thorns (barberry, cactus), antennae (pea), trapping apparatus (nepenthes), fleshy scales (onion), dense cuticle (agave).

Flower and its functions. Inflorescences and their biological significance

Flower- This is a modified generative shoot that serves for seed reproduction. Based on the structure of the flowers, plants are assigned to a particular family.

The flower develops from a generative bud. The stem part of the flower is shown pedicel And receptacle . The rest of the parts - cup , whisk , stamens , pestle are modified leaves. The combination of calyx and corolla is called perianth . A perianth not subdivided into calyx and corolla is called simple. Perianth with calyx and corolla is called double.

The main parts of a flower stamens And pestle . The stamen consists of a filament and an anther, inside which the pollen matures. Pestle (carpel) consists of a stigma, style and ovary. Inside the ovary is the ovule ( ovule), from which the seed develops after fertilization. From the walls of the ovary develops fetus. Flowers that have both pistils and stamens are called bisexual. same-sex flowers contain either stamens or pistils. Plants that have both staminate and pistillate flowers are called monoecious. Plants that develop either staminate or pistillate flowers are called dioecious.

Inflorescences are more visible to pollinators, easier to pollinate by wind. On plants bearing inflorescences, the number of ripening fruits is much greater than on single flowers.

inflorescences are divided into simple And complex. Simple inflorescences have flowers on the main axis, complex ones have simple inflorescences. Simple inflorescences - brush (lupine), ear (plantain), cob (corn), simple umbrella (cherry), head (clover), basket (aster), shield (mountain ash). Complex inflorescences - a complex brush or panicle (lilac), a complex umbrella (parsley), a complex ear (wheat), a complex shield (tansy).

Seed, fruit. Seed- an organ formed as a result of sexual reproduction of flowering plants and serving for the resettlement of plants. It develops from the ovule. The seed consists of the embryo, endosperm and seed coat. The embryo consists of a root, a kidney and one or two cotyledons. Monocots have one cotyledon, and the supply of nutrients is contained in the endosperm. Dicots have two cotyledons. The supply of nutrients they have is in the cotyledons. The seed coat is formed from the integument of the ovule and protects the embryo from drying out. For seed germination, a certain temperature, humidity, and air are necessary. Seed dormancy is an important adaptive property that prevents premature germination.

Fruit - organs of protection and distribution of seeds. The fruit is the final stage of flower development. It develops from the ovary of a flower. The walls of the ovary form the pericarp. Depending on the type of pericarp, the fruits are divided into dry and juicy, and on the number of seeds - into multi-seeded and single-seeded.

Dry fruits. From left to right: walnut, bean (pea), boll (poppy), achene (sunflower), caryopsis (wheat), lionfish (maple)

Dry one-seeded fruits- achene, caryopsis, walnut (sunflower, rye, hazel).

Juicy one-seeded- drupe (cherry, plum, apricot).

Juicy multi-seeded- berry (grape, tomato).

Special types of juicy multi-seeded fruits:

- apple - the ovary is immersed in the tissue of the receptacle (apple, pear, quince);

- pumpkin - hard pericarp, formed from the lower ovary (cucumber, melon);

- orange - a multi-celled fruit formed from the upper ovary (orange, lemon, tangerine).

Fruits formed from several flowers are called infructescences.

Complex fruits: multi-nut, polydrupe, strawberry(strawberry pulp is a receptacle, and real fruits are nuts on the surface of strawberries).

Adaptations of fruits for distribution are associated with the method of distribution - animals, wind, water. Hooks, hooks, color, taste, flyers, parachutes, and other devices ensure the resettlement of plants.

EXAMPLES OF TASKS

Part A

A1. The root system of a plant is made up of roots.

1) rod 3) accessory

A2. What function do roots not perform?

1) fixing the plant in the soil

2) absorption of mineral salt solutions

3) storage of organic matter

4) the formation of organic substances

A3. A cut poplar branch placed in water will develop roots.

1) subordinate 3) main

2) lateral 4) all types of roots

A4. Root cap protects the area

1) conduct 3) growth

2) suction 4) fission

A5. Flowers develop from buds

1) vegetative 3) apical

2) generative 4) sleeping

A6. If 3 or more leaves develop in one node of the shoot, then the arrangement of leaves on this shoot is called

1) regular 3) whorled

2) opposite 4) spiral

A7. The similarity between the root and the stem is manifested in the fact that both organs

1) grow from a kidney

2) are divided into the same functional areas

3) have kidneys

4) grow with their tip

A8. Leaves are called simple

1) mesh venation

2) one petiole and one leaf blade

plant organs

In plants, the following organs are distinguished: root, shoot, consisting of a stem, leaves and buds, flower, seed, fruit. All of the above organs are found only in angiosperms; gymnosperms do not have a flower and fruit, ferns lack a flower, seed and fruit, bryophytes have only an escape. The root and shoot are vegetative organs, the rest are generative. The vegetative organs are responsible for the nutrition and metabolism of the plant, i.e. ensure its existence. Generative organs carry out seed propagation of plants. Sometimes the term "reproductive organs" is encountered - these are organs that serve for reproduction, i.e. they include both vegetative and generative organs.

ROOT

A root is a vegetative axial organ of a plant, which has radial symmetry and is most often found in the soil. Plant roots never form generative organs and leaves.

Functions :

Absorption of water and minerals.
Support.
Supply of nutrients.
Synthesis of organic substances (phytohormones, alkaloids).

Root types

Chief (develops from the germinal root of the seed).
Adnexal (develop on the underground or aboveground parts of the shoot).
Lateral (occur during lateral branching of the roots, i.e. they develop on the main, adventitious and lateral roots).

All plant roots form root system- rod or fibrous. Dicotyledonous plants have a tap root system (excl.: large plantain), monocotyledonous plants have a fibrous root system. Rod - the main root is clearly expressed (beans, maple). The tap root system is formed mainly by the main and lateral roots. Fibrous - the main root is poorly developed or absent (wheat, onion). The fibrous root system is mainly formed by adventitious and lateral roots.

Root structure. The structure of the root in a longitudinal section. The top of the root is covered with a root cap (these are living cells that protect the apical meristem of the root). Starting from the top of the root, the following zones are distinguished:

The division zone is located immediately under the cover.
Growth zone.
suction zone.
The conduction zone in which the formation of lateral roots occurs.

Root structure in cross section. In the division zone, there are cells of the educational tissue, which ensure the growth of the root in length. In the growth zone, individual cells continue to divide, and the differentiation of the integumentary, main, and conductive tissues of the root also begins.

In the absorption zone, rhizodermal cells have outgrowths - root hairs, through which plant roots absorb water and minerals from the soil. Thanks to the root hairs, the suction surface increases by 10 or more times. There is a large vacuole in the root hair, the nucleus is displaced to the tip of the hair. Under the rhizoderm is a bark consisting of thin-walled living cells. In the center of the root is a central cylinder made of bast and wood. The core is not formed in the root.

In the conduction zone between the wood and the bast, a cambium arises, which is responsible for the growth in thickness. The tissues of the cortex cannot follow the secondary thickening and die, and due to the work of phellogen, a new integumentary tissue appears on the surface of the root - a cork.

Absorption of water and mineral salts by roots occurs in all root zones, but is most active in the absorption zone. From the root hairs, water and mineral salts enter the root bark, and from it into the wood, through which further transport to the stem is carried out. There are two ways for water and substances dissolved in it to enter: through the cell walls or through the living contents of the cells. Osmosis is the suction of water into a cell with a more concentrated solution. Osmosis creates root pressure- the force that contributes to the one-way movement of water along the xylem from the bottom up (from the root to the stem).

Root breath. The root absorbs oxygen and releases carbon dioxide during respiration. This is confirmed by the following experiment: if a plant root is placed in a test tube for a while, then it is removed and a burning match is lowered into the test tube, the match will go out almost instantly.

Root modifications

A root crop is an organ in the formation of which the lower part of the stem and the main root (carrots, beets, turnips, radishes) participate. The main function of the root crop is the storage of nutrients.
Root tubers or root cones are a thickening of adventitious roots (dahlia, sweet potato, chistyak). The main function is the supply of nutrients and vegetative reproduction.
Bacterial nodules (legumes) are thickenings on the roots, inside which bacteria are located. Bacteria convert nitrogen from the atmosphere into substances that are absorbed by the plant; the plant provides bacteria with organic substances, i.e. this is an example of symbiosis.

Human influence on plant root systems

Soil cultivation. When digging, the soil structure improves, the roots are located in the entire plowed horizon, where they receive the necessary amount of water and air. When loosening the top layer of soil (cultivation), the soil crust is destroyed, the water and air regime improves.

Watering. Should be equal and sufficient. In agriculture, there is a direction - hydroponics, when plants are grown in aqueous nutrient solutions without soil.

Pick - removal of the top of the main root. The root system becomes more powerful and develops in the upper, most fertile horizon.

Fertilizers. There are mineral and organic fertilizers. Minerals are divided into nitrogen (saltpeter, urea), phosphorus (superphosphate, double superphosphate), potassium (potassium sulfate, potassium chloride), complex (contain phosphorus, nitrogen and potassium, such as nitrophoska) and microfertilizers (contain trace elements - zinc, iron, boron). , molybdenum). Organic include manure, peat, bird droppings (guano). Nitrogen fertilizers are responsible for the growth and faster development of plants (increase in vegetative mass). Potassium helps to improve the quality of fruits, increase the resistance of plants to certain diseases, increase frost resistance and drought resistance. Phosphoric improve the growth of the root system, increase the yield and improve its quality, accelerate the maturation of plants, increase their resistance to drought. Microfertilizers contribute to the synthesis in the plant of substances necessary for growth and development. All fertilizers are applied in a strictly defined amount. Nitrogen fertilizers are applied in the spring, potash and phosphorus - usually in the fall. The use of fertilizers is possible in dry form (in the spring before sowing or in the autumn when digging) and in liquid form - root and foliar top dressing (solutions with a concentration of not more than 10% and 1%, respectively) during the growing season.

THE ESCAPE

This is an organ consisting of a stem, leaves and buds and is most often located in the ground-air environment. Knot- this is the section of the stem on which the leaf and axillary bud are located. internode is the section of the stem between two neighboring nodes. The angle formed by the leaf and the stem above is called leaf axil.

Shoot types

Upright - the stem is in a vertical position.
Creeping - the stem occupies a horizontal position.
Creeping - the stem occupies a horizontal position, and adventitious roots (meadow tea) are formed on it.
Curly (beans).
Clinging (rank).
Depending on the severity of the internodes: shortened and elongated.

Bud

The kidney is a rudimentary shoot.

Types of kidneys

According to the position on the stem, there are apical (at the top of the shoot) and lateral or axillary buds (located in the axils of the leaves).
By the presence or absence of kidney scales - closed (there are kidney scales - oak, poplar, linden) or open kidneys (there are no kidney scales - clover, buckthorn, elodea).
By the nature of the internal content - vegetative, generative (floral, cherry) and mixed buds (elder, lilac). Vegetative buds contain the rudiments of only vegetative organs, generative - only generative, mixed - both generative and vegetative.
Accessory kidneys. They are located on the internodes of the stems, on the leaves and on the roots.
Sleeping buds located on the stem, but not opening immediately after formation. They are, as it were, a reserve of escape (it is precisely because of the presence of dormant poplar buds that new shoots form after heavy pruning).

The structure of the kidney. Outside, most kidneys are covered with kidney scales, which protect the kidney and prevent its internal contents from drying out. Inside are the rudiments of all organs of the plant: rudimentary leaves, rudimentary stem, rudimentary buds. Also inside the kidney may contain the beginnings of future flowers. At the top of the rudimentary stem there is a cone of growth - this is an educational tissue.

SHEET

A leaf is a vegetative organ of a plant that occupies a lateral position and carries out air nutrition of plants. Unlike other vegetative organs, the leaf is not characterized by unlimited (i.e., throughout life) growth. Functions: f otosynthesis, water evaporation, gas exchange.

External leaf structure. The leaf consists of a base, petiole, leaf blade and stipules. Stipules can grow together, covering the stem - this forms a bell (sorrel). The base is the part of the leaf that attaches the leaf to the stem. If the base grows and covers the stem, then a leaf sheath is formed (wheat, corn, wheatgrass).

Leaf types. Depending on the number of leaf blades, the leaves are divided into simple(one leaf blade, there is no articulation between it and the petiole) and complex(one or many leaf blades isolated from a common petiole). Among the compound leaves, there are: trifoliate (clover, strawberry, oxalis), palmate (horse chestnut), paired (yellow acacia) and odd-pinnate (ash, mountain ash, dog rose).

Venation is the arrangement of vascular bundles (veins) in a leaf blade. Happens:

Cirrus (lilac, birch, linden).
Palmate (cuff, maple).
Arc (large plantain, lily of the valley).
Parallel (rye, corn, bluegrass).

leaf arrangement is the order in which the leaves are placed on the stem. Distinguish:

The next leaf arrangement - only one leaf departs from each node (birch, poplar, oak).
Opposite leaf arrangement - two leaves depart from each node (lilac, maple, elderberry).
Whorled leaf arrangement - three or more leaves depart from each node (oleander, raven eye, elodea).

Leaf mosaic. Leaf mosaic is the arrangement of plant leaves in one plane. The leaves in the mosaic are arranged horizontally, while the leaves have different sizes and practically do not obscure each other, which allows the maximum use of solar energy.

The internal structure of the leaf. Outside is the integumentary tissue - the epidermis. Stomata are located mainly on the underside of the leaf (in aquatic plants with floating leaves (water lily), on the contrary, stomata are mainly located on the upper side of the leaves). The integumentary tissue of the leaf secretes a special layer consisting of waxes - the cuticle, which reduces evaporation from the leaf surface.

Between the upper and lower epidermis is the main leaf tissue, which consists of columnar and spongy parenchyma. The columnar (palisade) parenchyma is located under the upper epidermis and is formed by cells elongated in a perpendicular direction to the epidermis. The spongy parenchyma is located under the columnar tissue and consists of loosely arranged cells with a large number of intercellular spaces.

Leaf veins (conductive bundles) do not contain cambium. The wood is located closer to the upper surface of the sheet, and the bast is closer to the bottom. Outside the conducting bundle is usually a mechanical tissue.

Processes in the leaf

Photosynthesis – This is the process of formation of organic substances from inorganic substances with the help of sunlight.
Gas exchange in plants takes place in the leaves through stomata. During the day, both carbon dioxide and oxygen enter the plant, and both oxygen and carbon dioxide are released, i.e. In the daytime, two processes run in parallel in plant cells - photosynthesis and respiration. At night, photosynthesis does not occur, respiration occurs in the cells (mainly due to the oxygen contained in the intercellular spaces).
Evaporation of water. The release of water by the plant occurs through the stomata of the epidermis. In this case, the plant is cooled, which saves from overheating, in addition, a continuous flow of water from the roots to the leaves is maintained. Plants can be protected from excessive evaporation in the following ways: reduction and (or) modification of the leaf blade (feather grass, cactus); well-developed cuticle (agave); a large number of hairs in the epidermis (saintpaulia).
Leaf fall is the natural fall of leaves. In this regard, plants are divided into deciduous and evergreen. Evergreens are characterized by perennial leaves (pine leaves live 2-4 years, spruce - 5-7 years). In deciduous plants, at the end of the growing season, all leaves (oak, birch, maple) fall annually. By the end of summer - the beginning of autumn, the leaves begin to age, the metabolic rate decreases in them, chlorophyll and chloroplasts begin to break down, the leaves acquire a different color (not for all plants: for example, lilac leaves remain green). Between the base of the leaf and the stem, a separating layer of cells begins to form, consisting of dead cork cells. In the axil of the leaf, a bud is finally formed at this time, after which the leaf falls off. The trace of a fallen leaf on the stem is called a leaf scar. The value of leaf fall: removal of unnecessary substances from the body; reduction of evaporation, which is especially important in winter, when the flow of water from the soil practically stops; a decrease in the mass of shoots and their area, which reduces the amount of snow lingering on the branches, therefore, the probability of breakage of the shoots is reduced.

Leaf modifications

Spines - develop in plants that live in conditions of insufficient moisture (cactus)
Antennae (peas, rank).
Trapping devices of insectivorous plants (dew).
Scales - small, underdeveloped leaves (lily of the valley, peas).

Stem

The stem is the axial part of the shoot. Functions: support, transport of substances, supply of substances, photosynthesis (in young stems of trees and shrubs, as well as in herbs).

The internal structure of the stem (for example, linden)

The primary structure of the stem:

a) Primary cortex. Outside is the epidermis, under which the main photosynthetic tissue is located. In addition to these tissues, the composition of the primary cortex also includes mechanical tissues (often collenchyma).

b) The central cylinder, in which conductive tissues and the core are isolated. Conductive tissues are represented by xylem and phloem; they form conductive bundles. The core is made up of living cells.

Secondary structure of the stem. Its appearance is associated with the laying of the cambium and the replacement of one type of integumentary tissue (epidermis) with another (periderm). The secondary structure of the stem includes the following sections: secondary bark (cork and bast), cambium, wood and pith.

Development of an escape from the kidney. Branching. In the spring, sap flow begins in plants, and the necessary substances enter the kidneys. The cells of the cone of growth begin to actively divide, the rudimentary stem increases, the renal scales move apart and gradually fall off, and a renal ring forms in their place. The shoot grows and develops, new leaves and new buds form on it. A shoot that develops from a bud in one growing season is called an annual growth.

During the development of the shoot, its branching occurs. Branching is the formation of new shoots located at an angle to each other. There are two types of branching: apical and lateral. Apical branching is carried out due to the division of the apical educational tissue into two parts (the so-called dichotomous branching) and is characteristic of Lycopods. With lateral branching, new shoots arise from lateral buds. A variation of lateral branching is tillering, in which the formation of new shoots occurs from axillary buds located at the base of the main shoot (cereals, shrubs).

Stem growth. In length, it is carried out due to the division and subsequent growth of cells of the apical and (or) intercalated educational tissues. In thickness, growth occurs due to the activity of the cambium. The work of the cambium is periodic: in spring and early summer it is intense, and by the end of the growing season it subsides. The cambium deposits more cells towards the wood. At the beginning of the growing season, the cambium forms vessels with a large lumen, few mechanical elements are formed, by the end of the growing season, the lumen of newly formed vessels decreases and more mechanical elements are formed. On the transverse saw cut of a tree, these differences are visible to the naked eye in the form of growth rings. The annual ring is the increase in wood per year along the thickness of the stem. The growth rings can be used to determine the age of a plant.

Transport of substances

Water moves along the wood with substances dissolved in it (mainly mineral substances, but organic substances that are synthesized or accumulated in the roots also move) from the bottom up. At the beginning of spring, a solution with a predominance of organic substances moves through the wood.
Dissolved organic substances move along the bast in both directions: from leaves to roots (top to bottom) and from leaves to fruits and flowers (bottom to top).

Escape modifications:Elevated

Thorns (hawthorn) - perform protective functions.
A tendril is a modified leaf (pea) or the entire shoot (grape). Function: twisting around the support, holding the shoot in a vertical position.
The above-ground stolon is an elongated creeping shoot. It lives less than a year and performs the function of vegetative reproduction: a shortened shoot (“rosette”) is formed at the top of the stolon, which takes root, and a new plant develops from it (survival, strawberry).
A head of cabbage is a modified kidney (cabbage).

Underground

Underground stolon. Performs the function of resettlement and vegetative reproduction. Formed from buds at the base of the stem; usually white with colorless scale-like leaves. In plants such as potatoes, sedumnik, a tuber is formed at the end of the stolon.
The tuber is a strongly thickened underground shoot (potato, Jerusalem artichoke, corydalis, septenary). It performs the function of a supply of nutrients, ensures the survival of adverse conditions, vegetative propagation and renewal.
Bulb - an underground shoot with a very short flattened stem (bottom) and succulent leaves (lily, tulip, onion). Functions: supply of nutrients, survival of adverse conditions, renewal, vegetative reproduction.
A corm is an underground shoot of a plant. It has dry, membranous leaves, and reserve nutrients are deposited in the stem (crocus, gladiolus, colchicum).
Rhizome - an underground or above-ground modified perennial shoot with scaly or green leaves. Responsible for reproduction, resettlement, supply of nutrients, renewal and waiting for adverse environmental conditions (wheatgrass, lily of the valley, iris).

An organ is a part of a plant that has a certain external (morphological) and internal (anatomical) structure in accordance with its function. There are vegetative and reproductive organs of a plant.

The main vegetative organs are the root and shoot (stem with leaves). They provide the processes of nutrition, conduction and substances dissolved in it, as well as vegetative reproduction.

Reproductive organs (spore-bearing spikelets, strobili or cones, flower, fruit, seed) perform functions associated with sexual and asexual reproduction of plants and ensure the existence of the species as a whole, its reproduction and distribution.

The dismemberment of the body of plants into organs, the complication of their structure occurred gradually in the process of development of the plant world. The body of the first land plants - rhinophytes, or psilophytes - was not divided into roots and leaves, but was represented by a system of branching axial organs - telomes. As plants emerged onto land and adapted to life in air and soil environments, telomes changed, which led to the formation of organs.

In algae, fungi and lichens, the body is not differentiated into organs, but is represented by a thallus, or thallus of a very diverse appearance.

During the formation of organs, some general patterns are found. With the growth of the plant, the size and weight of the body increase, cells divide and stretch in a certain direction. The first stage of any neoplasm is the orientation of cellular structures in space, i.e. polarity. In higher seed plants, polarity is already found in the zygote and the developing embryo, where two rudimentary organs are formed: a shoot with an apical bud and a root. The movement of many substances occurs along the conductive paths polarly, i.e. in a certain direction.

Another pattern is symmetry. It manifests itself in the location of the side parts in relation to the axis. There are several types of symmetry: radial - two (or more) planes of symmetry can be drawn; bilateral - only one plane of symmetry; at the same time, dorsal (dorsal) and ventral (abdominal) sides are distinguished (for example, leaves, as well as organs growing horizontally, i.e. having plagiotropic growth). , growing vertically - orthotropic - have radial symmetry.

In connection with the adaptation of the main organs to new specific conditions, their functions change, which leads to their modifications, or metamorphoses (tubers, bulbs, spines, buds, flowers, etc.). In plant morphology, homologous and similar organs are distinguished. Homologous organs have the same origin, but may differ in form and function. Similar organs perform the same functions and have the same appearance, but are different in their origin.

The organs of higher plants are characterized by oriented growth ( , which is a response to the unilateral action of external factors (light, gravity, humidity). The growth of axial organs towards the light is defined as positive (shoots) and negative (main root) phototropism. Oriented growth of the axial organs of a plant, caused by the unilateral action of the force of gravity, is defined as geotropism.Positive geotropism of the root causes its directed growth towards the center, negative geotropism of the stem - from the center.

The shoot and root are in their infancy in the embryo in the mature seed. The embryonic shoot consists of an axis (embryonic stalk) and cotyledon leaves, or cotyledons. The number of cotyledons in the embryo of seed plants ranges from 1 to 10-12.

At the end of the axis of the embryo is the growth point of the shoot. It is formed by the meristem and often has a convex surface. This is the cone of growth, or apex. At the top of the shoot (apex), the rudiments of leaves are laid in the form of tubercles or ridges following the cotyledons. Typically, leaf buds grow faster than the stem, with young leaves covering each other and the growing point, forming a bud of the embryo.

The part of the axis where the bases of the cotyledons are located is called the cotyledon node; the rest of the germinal axis, below the cotyledons, is called the hypocotyl, or hypocotyl knee. Its lower end passes into the germinal root, represented so far only by a cone of growth.

When the seed germinates, all the organs of the embryo gradually begin to grow. The germinal root emerges first from the seed. It strengthens the young plant in the soil and begins to absorb water and minerals dissolved in it, giving rise to the main root. The area on the border between the main root and the stem is called the root collar. In most plants, the main root begins to branch, while lateral roots of the second, third and higher orders appear, which leads to the formation of a root system. On the hypocotyl, on old parts of the root, on the stem, and sometimes on the leaves, adventitious roots can form quite early.

Almost simultaneously, a first-order shoot, or main shoot, develops from the germinal bud (apex), which also branches, forming new shoots of the second, third and higher orders, which leads to the formation of the main shoot system.

As for the higher spore shoots (mosses, horsetails, ferns), their body (sporophyte) develops from the zygote. The initial stages of the life of a sporophyte take place in the tissues of the outgrowths (gametophytes). An embryo develops from a zygote, consisting of a rudimentary shoot and a root pole.

So, the body of any higher plant consists of shoot and (except mossy) root systems, built from repeating structures - shoots and roots.

In all organs of a higher plant, three tissue systems - integumentary, conductive and main - continuously continue from organ to organ, reflecting the integrity of the plant organism. The first system forms the outer protective cover of plants; the second, including phloem and xylem, is immersed in the system of basic tissues. The fundamental difference in the structure of the root, stem and leaf is determined by the different distribution of these systems.

During the primary growth, which begins near the tops of the roots and stems, primary ones are formed that make up the primary body of the plant. The primary xylem and primary phloem and their associated parenchymal tissues form the central cylinder, or stele, of the stem and root of the primary plant body. There are several types of steles.

ROOT

A root is an axial vegetative organ of a plant that has unlimited apical growth, positive geotropism, has a radial structure and never bears leaves. The top of the root is protected by a root cap.

The value of the root is the fixation of the plant in the soil, the absorption of water and mineral salts, the storage of organic substances, the synthesis of amino acids and hormones, respiration, symbiosis with fungi and nodule bacteria, vegetative reproduction (in root plants).

The main root is the root that develops from the germinal root.

An adventitious root is a root that develops from a stem or leaf.

Lateral root - a branch of the main, lateral or adventitious root.

The main root system is the main root with all lateral roots and their branches.

Adventitious root system - adventitious roots with all lateral roots and their branches.

Tap root system - a root system with a well-defined main root of the tap form.

Fibrous root system - a root system represented mainly by adventitious roots, in which the main root is not distinguished.

A root crop is a modified, thickened main root that carries a shortened shoot at the base and performs the function of storing nutrients (carrots).

Root tuber - a modified thickened lateral or adventitious root that performs the function of storing nutrients (dahlia).

Root zones are structures that successively replace each other as the root grows in length.

The division zone is a cone of growth, represented by the apical educational tissue, which ensures the growth of the root in length due to continuous cell division.

The elongation zone is the zone of the root where the cell size increases and their specialization begins.

The suction zone is a zone that moves with growth, where cells specialize in various tissues and absorb water from the soil with the help of root hairs.

The conduction zone is the root zone located above the absorption zone, where water and mineral salts move through the vessels, and carbohydrates through the sieve tubes. The root in this zone is covered with cork cloth.

Root cap - a protective, constantly renewing cell formation at the top of a growing root

STEM

The stem is an axial vegetative organ of a plant with apical unlimited growth, positive heliotropism, radial symmetry, bearing leaves and buds. It connects the two poles of plant nutrition - roots and leaves, brings the leaves to the light, stores nutrients.

A tree is a life form of a plant with one perennial woody stem - a trunk, on the branches of which (in the crown) there are renewal buds.

A shrub is a life form of a plant with several perennial woody stems bearing renewal buds.

Perennial grass is a life form of a plant that bears one or more non-woody shoots, the above-ground part of which dies off in autumn, and the underground part with renewal buds hibernates.

An annual grass is a life form of a plant in which the life cycle continues from seed germination to the formation of its own seeds and death, that is, one growing season.

The main stem is the stem that develops from the bud of the seed germ.

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

A node is a section of a stem from which a leaf emerges.

An internode is the section of a stem between two nodes.

Subcotyledon knee - the lower part of the stem between the cotyledon node and the root.

Supra-cotyledon - the section of the stem between the node of the first true leaf and the cotyledon.

Apical growth - the growth of the stem in length due to the work of the growth cone of the apical bud.

Intercalated growth - the growth of the stem in length due to the work of the educational tissue at the bases of the internodes.

An upright stem is a stem that grows upward perpendicular to the ground.

A creeping stem is a stem that spreads along the surface of the soil and takes root with the help of adventitious roots.

A climbing stem is a stem that wraps around a support.

Clinging stem - a stem that rises up, clinging to a support with the help of antennae.

BUD

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

Apical bud - a bud located at the top of the stem, due to the development of which the shoot grows in length.

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

Adnexal bud - a bud that forms outside the sinus (on a stem, root or leaf) and gives an adnexal (random) shoot.

Leaf bud - a bud consisting of a shortened stem with rudimentary leaves and a growth cone.

Flower bud - a bud, represented by a shortened stem with the beginnings of a flower or inflorescence.

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

A regeneration bud is a wintering bud of a perennial plant from which a shoot develops.

A dormant bud is a bud that has been dormant for several growing seasons.

THE ESCAPE

Escape - a stem with leaves, buds, formed during one summer.

The main shoot is the shoot that developed from the bud of the seed germ.

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

An elongated shoot is a shoot with elongated internodes.

Shortened shoot - shoot with shortened internodes.

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

A flower-bearing shoot is a shoot that bears reproductive organs - flowers, then fruits and seeds.

INTERNAL STRUCTURE OF THE STEM

The internal structure of the stem of a woody plant is a structure, on the cross section of which the following parts are distinguished: cork, bast, cambium, wood, core.

Cork is an integumentary tissue consisting of several layers of dead cells; formed on the surface of overwintering stems.

Bast (bark) - a complex of conductive (sieve tubes), mechanical (bast fibers) and basic tissues located outside of the cambium; serves to carry carbohydrates from the leaves to the roots.

The cambial ring is an educational tissue consisting of a single layer of dividing cells; lays bast cells outward, wood cells inward.

Wood is an annually growing complex of conductive (vessels), mechanical (wood fibers) and basic tissues located inward from the cambium; is a stem support and serves to conduct water and mineral salts from the roots to the leaves.

Annual ring - a layer of wood formed due to the work of the cambium during one summer.

The core is the main tissue located in the center of the stem; performs a storage function.

MODIFIED SHOOTS

A modified shoot is a shoot in which the stem, leaves, buds (or all together) irreversibly change shape and function, which is a consequence of adaptive changes in the course of evolution. Similar modifications appear in representatives of different systematic groups of plants, which indicates convergence (homology) in homogeneous environmental conditions.

Rhizome - a modified perennial underground shoot with nodes, internodes, scaly leaves and buds, which serves for vegetative propagation, renewal and storage of nutrients (couch grass, horsetail, lily of the valley).

A tuber is a modified underground shoot that forms at the top of a stolon, stores nutrients in a thickened stem part and serves for vegetative propagation (potato, Jerusalem artichoke). Bears axillary kidneys.

Stolon is an elongated creeping one-year-old shoot that forms a tuber (potato) at the top.

The bulb is a shortened shoot, the stem part of which is represented by a flat thickening - the bottom. Nutrients are stored in succulent scaly leaves. The lateral axillary buds, growing, are separated. Serves for vegetative propagation and renewal (onion, garlic, tulip).

SHEET

A leaf is a lateral vegetative organ of a plant, growing from the stem, having bilateral symmetry and growing at the base. Serves for photosynthesis, gas exchange and transpiration. Leaf growth is limited.

The leaf base is the part of the leaf that connects the leaf to the stem. Here is the educational tissue that gives rise to the leaf blade and petiole. The leaf base sometimes takes the form of a tubular sheath or forms paired stipules.

Leaf blade - an extended, usually flat part of the leaf, performing the function of photosynthesis, gas exchange, transpiration and, in some species, vegetative reproduction.

The petiole is a narrowed part of the leaf that connects the leaf blade to the base and regulates the position of the leaf in relation to the light source. Leaves with petioles are called petiolate, and those without petioles are called sessile.

Stipules are leaf-shaped formations at the base of the leaf that serve to protect the young leaf and axillary bud.

Leaf axil - the angle between the leaf petiole and the stem, usually occupied by the lateral axillary bud.

Leaf fall is a natural fall of leaves in woody plants and shrubs, associated with the preparation of plants for winter and due to a change in the length of the day. At the base of the petiole, a separating layer is formed, due to which the leaf comes off. The cork layer protects the leaf scar.

A simple leaf is a leaf consisting of one leaf blade and one petiole and falling entirely.

A compound leaf is a leaf that includes several leaf blades (leaves) located on a common petiole and falling off separately.

Whole leaf - a leaf having an undivided leaf blade.

A lobed leaf is a leaf whose blade is dissected into lobes up to 1/3 of the half-leaf width.

Separate sheet - a sheet with a plate, dissected up to 1/2 of the width of the half-sheet.

Dissected leaf - a leaf, the plate of which is dissected to the main vein or to the base of the leaf.

Leaf veins - a system of vascular bundles that bind the leaf into a single whole, serve as a support for the leaf pulp and connect it to the stem.

Leaf venation is the arrangement of veins in a leaf blade. With pinnate venation, the main vein is expressed, from which the lateral veins depart in both directions, with palmate - the main vein is not expressed, several large veins enter the leaf, from which the lateral ones depart.

Reticulate venation - venation of pinnate and palmate types. With parallel venation along the plate, several identical veins run parallel to each other from the base of the leaf to its top.

Leaf arrangement - the arrangement of leaves on the stem, most conducive to the fulfillment of their function. With the next leaf arrangement, one leaf is attached to each node of the stem, with the opposite - in each node there are two leaves opposite each other, with whorled, several leaves develop in the stem node.

The edge of the leaf blade is solid, serrated (right angles), serrated (sharp angles), crenate (rounded protrusions), notched (rounded notches).

INTERNAL STRUCTURE OF THE LEAF

The upper skin is the integumentary tissue on the side of the leaf facing the light, often covered with hairs, cuticles, and wax.

The lower skin is the integumentary tissue on the underside of the leaf, usually bearing stomata.

Stomata - a slit-like opening in the skin of a leaf, surrounded by two guard cells. Serves for gas exchange and transpiration.

Columnar tissue - the main tissue, the cells of which are cylindrical, tightly adjacent to each other and located on the upper side of the leaf (facing the light). Serves for photosynthesis.

Spongy tissue is the main tissue, the cells of which are rounded, located loosely (many intercellular spaces), closer to the lower skin of the leaf. Serves for photosynthesis, gas exchange and transpiration.

The wood of the vein is part of the conductive bundle of the leaf, consisting of vessels through which water with minerals enters the leaf from the stem.

Vein bast - part of the vascular bundle of the leaf, consisting of sieve tubes, through which carbohydrates (sugar, glucose) move from the leaf to the stem.