Basic plant organ systems. Basic terms and concepts (Vegetative organs of plants)

TICKET No. 1

Floriculture, role and tasks.

List the main plant organs, their functions and significance.

1. Floriculture as an integral part of green building is intended to play an important role in improving the landscapes of residential and industrial areas.

Floriculture as a branch of plant growing is based on the principles of modern biology. The biological basis of floriculture is knowledge of the characteristics of the growth and development of flower crops, their needs for environmental factors in order to develop the most rational agricultural techniques. The final task is to study the patterns of formation of the maximum yield of flower products with high quality indicators and the lowest costs. Modern floriculture is an industrial branch of plant growing.

Floriculture is one of the most profitable branches of agriculture.

2. Root- the vegetative organ of a plant, which first appears during seed germination. The root grows, branches and forms a root system.

The root system is the totality of all the roots of one plant. It comes in 3 types:

1) Rod;

2) fibrous;

3) Mixed.

A plant with a rod system does not tolerate transplantation well. Plants grown by seedlings always have a fibrous root system. The junction of the root and the stem is root neck.

Root functions:

1)Keeps the plant in the soil;

2) Absorbs water and nutrients dissolved in it;

3) Can be a place of deposition of nutrients;

4) The root breathes, absorbs oxygen.

Root modifications:

Root vegetable- this is a modified root containing a supply of nutrients (carrots, beets)

Pip- this is an underground modified root (dahlia)

Aerial roots, they absorb moisture from the air, serve for support and additional nutrition (monstera)

Nodules formed in leguminous plants, they absorb free nitrogen from the air and convert them into complex compounds necessary for plant nutrition.

Stem- vegetative organ.

Functions of the stem:

1) Connects the above-ground and underground parts of the plant

2) Is a conductor of nutrients

3) Distribution and educational function

4) May be a reproductive organ

The structure of the stem can be lignified, semi-lignified, or green. According to the nature of growth, the stem can be: erect, clinging, climbing, creeping, climbing. A stem with leaves and buds is called escape.

Parts of the shoot: the junction of the leaf and the stem is called knot, the distance between nodes is called internode, the angle between the stem and the leaf is called sinus leaf.

Bud- this is a greatly shortened shoot with the rudiments of leaves or flowers.

Rhizome- This is an underground stem with modified leaves and buds.

Tuber- This is an underground stem containing a large supply of nutrients.

Corm- This is an underground stem with noticeable round internodes.

Thorn- a modified stem located in the axil of the leaf.

The stem can perform the function of a leaf, then the leaf is reduced to a scale; if the stem performs the function and is similar to a leaf, this modification is called phylloclady.. If the stem performs a function and does not look like a leaf, then such a modification is called Cladodia.

Sheet- a vegetative organ, it consists of a leaf blade, petiole and stipule. Leaves can be simple or compound. The petiole serves to attach the leaf to the stem. If the leaf does not have a petiole, it is called sessile. Leaf arrangement: alternate, when the leaves follow each other, opposite, when the leaves are located opposite each other, whorled, the leaves are arranged in a bunch.

Sheet functions:

Photosynthesis- formation of organic substances from inorganic ones.

Gas exchange, i.e. the leaf simultaneously absorbs and releases oxygen and carbon dioxide.

Transpiration- this is evaporation that protects the plant from overheating.

Flower- this is a greatly shortened shoot with modified leaves adapted for sexual reproduction.

Main properties: decorative, formation of seeds and fruits.

Concept of plant organs

Definition 1

Organ- this is a part of a plant organism adapted to perform one or more functions.

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

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

Vegetative organs of plants

Definition 2

Vegetative organs (from the Latin vegetativas - plant) in plants are those that support the basic life processes, that is, they 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 an aquatic to a 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 always grows from the center of the Earth (negative geotropism). The axial organs - stem and root - are located vertically to the surface of the Earth (orthotropic organs) and the leaves - at an angle (plagiotropic organs). This specialization is due to two areas of plant nutrition (soil and atmospheric), and therefore, a two-way flow of water with dissolved minerals and organic substances.

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

Stem in typical cases - an axial polysymmetric 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 at the base by intercalary growth (in monocots) or over 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 the leaf is similar to the life span of the stem. In trees and bushes it is a temporary organ. The main functions of the leaf: photosynthesis, gas exchange, transpiration, reproduction, protective (spines), cleansing (leaf fall), nutrition (sundew).

Note 1

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

The division of the plant body 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.

Generative organs of plants

Definition 3

Generative (reproductive) organs(from lat. genero - giving birth) plants arose much later than vegetative ones. The flower, seed and 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 and seeds are formed. The process of sexual reproduction in flowering plants occurs when the plant flowers (the flowers open).

Flowers are very diverse in shape, size, color and structural features. 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 reproductive cells (sperms). The pistils contain the seed buds, and they contain the female reproductive cells (eggs).

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

Note 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 that both distinguish them from representatives of other kingdoms of the organic world and bring them closer to them. The following can be considered distinctive features of the Plant kingdom:

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

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

– branching of the absorbing surface of the body;

– constant growth;

– manifestation of irritability;

– the presence of a cellulose cell membrane;

– ability to photosynthesis – autotrophic nutrition.

What brings plant organisms closer to representatives of other kingdoms of living nature is their cellular structure, common mechanisms of growth, development, reproduction, and 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 through the process of photosynthesis, plants create the main supply of biomass 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 occurred in an aquatic environment, which led to the appearance of algae. Then the plants began to colonize the land. This was facilitated by the emergence of the following aromorphoses:

– the emergence of photosynthesis;

– the emergence of a eukaryotic cell structure;

– occurrence of meiosis and fertilization;

– the emergence of multicellularity and cell differentiation with the formation of tissues and organs;

– the occurrence of alternation of haploid and diploid generations;

– emergence of the seed;

- the appearance of a flower.

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

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 a maximum in angiosperms. The following main groups of fabrics are distinguished: 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 stem, leaves and buds.

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

The root is an axial organ with radial symmetry. The root apex is covered root cap , under which there is educational tissue that ensures root growth.

Types of roots: main, lateral, subordinate. 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 .

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

– division zone, forming a cone root growth. This group of cells forms the root cap cells and mucilage, which protect the root and facilitate its advancement in the soil.

– root hair zone(absorption zone) is formed by outgrowths of cells of the primary, single-layer absorptive 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, due to the expenditure of energy. From the cells of the suction zone, water rises into the conducting elements of the root as a result of an increase in osmotic pressure. In the root vessels, the pressure rises to 3 atmospheres. It is created by the expenditure of energy by the plant. Water rises up the stem due to the evaporation of water in the leaves.

Many plants have modified roots: root vegetables (radishes, radishes, beets, etc.), root tubers (dahlia, sweet potato). The roots of many plants enter into symbiosis with fungi, forming mycorrhizae 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 buds emerge from one node;

– next – one bud per node;

– whorled – 3 or more buds in one node;

– spiral – the buds are arranged in a spiral.

The shoot elements are formed from a common apical

educational tissue and have a single conductive system. The formation of a shoot is one of the largest aromorphoses that determined the emergence of plants onto land.

Bud

– shortened embryonic shoot – consists of a rudimentary stem and rudimentary leaves (vegetative bud) or rudimentary flowers (generative bud). Buds that contain both leaves and flowers are called mixed buds.Apical budsensure shoot growth in length,lateral(axillary) provide branching of the shoot. Buds formed on leaves and in internodes are called adventitious buds. "Dormant buds» develop after the death of overlying buds and damage to plants. These buds ensure the restoration of plants. The buds can be protected by renal scales and are then called closed. Buds without scales are called open.

Stem – an axial vegetative organ with radial symmetry. Has apical growth. The main stem develops from the bud of the seed embryo. Functions of the stem: supporting, conducting, storing, photosynthesizing, plant growth and branching, vegetative propagation.

The structure of the stem. Stem herbaceous plants consists of epidermis and ground tissue - parenchyma. It contains conducting vascular-fibrous bundles containing elements of xylem and phloem. In the stems of woody plants, xylem and phloem are separated by the cambium. Cambium- This is an educational tissue that ensures the growth of the stem in thickness. A cross section of such a stem reveals: the pith, wood with annual rings, cambium, and bark. The bark is the entire layer located outward from the cambium. The inner layer of bark adjacent to the cambium is formed by phloem or phloem.

According to the nature of the direction of growth, the stems are divided into erect (pine), creeping (cucumber), clinging (meadow chin), climbing (lianas), climbing (convolvulus).

Modified stems form rhizomes, tubers, and bulbs.

Sheet 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 can be simple (with one leaf blade on a petiole) or complex (with several leaf blades having their own petioles). The shape of the leaves and their location on the stem, vein type are important systematic features.

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

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

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

The leaf skeleton is formed by vascular-fibrous bundles and mechanical tissue. Through the petiole, the conductive elements of the leaf are connected to the stem. According to the nature of the arrangement of the veins, leaves with reticulate, arcuate and parallel venation are found. Reticulate venation is most typical for dicotyledonous plants, arcuate and parallel - for monocotyledonous plants.

Photosynthesis occurs in columnar And spongy parenchyma tissues. The columnar tissue is adjacent to the upper skin, and the spongy tissue is adjacent to the lower skin.

Depending on the environment, the leaves have evolved various adaptations. In plants in arid places, adaptations are associated with a decrease in evaporation and the accumulation of moisture reserves. In plants in humid habitats, adaptations are associated with increased transpiration.

Depending on the nature of the adaptations, modifications of the leaves arose: spines (barberry, cactus), tendrils (peas), hunting apparatus (Nepenthes), fleshy scales (onion), dense cuticle (agagave).

Flower and its functions. Inflorescences and their biological significance

Flower is a modified generative shoot used for seed propagation. Based on the structure of the flowers, plants are classified into a specific family.

The flower develops from a generative bud. The stem part of the flower is represented peduncle And receptacle . Other parts - cup , whisk , stamens , pestle are modified leaves. The combination of the calyx and corolla is called perianth . A perianth that is not divided into a calyx and corolla is called simple. The perianth with a calyx and corolla is called double.

The main parts of a flower are stamens And pestle . The stamen consists of a filament and an anther, inside which the pollen ripens. Pestle (carpel) consists of stigma, style and ovary. Inside the ovary there is an ovule ( ovule), from which the seed develops after fertilization. It develops from the walls of the ovary 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 produce either staminate or pistillate flowers are called dioecious.

The inflorescences are more visible to pollinators and are more easily pollinated by the 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, while complex ones have simple inflorescences. Simple inflorescences - brush (lupine), ear (plantain), cob (corn), simple umbrella (cherry), head (clover), basket (aster), scutellum (rowan). Complex inflorescences - a complex raceme or panicle (lilac), a complex umbrella (parsley), a complex spike (wheat), a complex corymb (tansy).

Seed, fruit. Seed- an organ formed as a result of sexual reproduction of flowering plants and serving for plant dispersal. Develops from the ovule. A seed consists of an embryo, endosperm and seed coat. The embryo consists of a root, a bud and one or two cotyledons. Monocots have one cotyledon, and the supply of nutrients is contained in the endosperm. Dicotyledons have two cotyledons. Their supply of nutrients 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 required. Seed dormancy is an important adaptive property that protects against premature germination.

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

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

Dry single-seeded fruits– achene, grain, nut (sunflower, rye, hazel).

Succulent single-seeded– drupes (cherry, plum, apricot).

Succulent multi-seeded– berry (grapes, 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 multilocular fruit formed from the superior ovary (orange, lemon, tangerine).

Fruits formed from several flowers are called infructescences.

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

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

EXAMPLES OF TASKS

Part A

A1. The root system of a plant is formed by roots

1) core 3) subordinate clauses

A2. Which function do roots not perform?

1) fixing the plant in the soil

2) absorption of mineral salt solutions

3) storage of organic substances

4) formation of organic substances

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

1) subordinate clauses 3) main

2) lateral 4) all types of roots

A4. The root cap protects the area

1) carrying out 3) growth

2) suction 4) division

A5. Flowers develop from buds

1) vegetative 3) apical

2) generative 4) dormant

A6. If 3 or more leaves develop in one shoot node, 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 bud

2) divided into identical functional zones

3) have kidneys

4) grow with their tip

A8. Leaves with

1) reticulate venation

2) one petiole and one leaf blade

Plant organs

Plants have the following organs: root, shoot, consisting of stem, leaves and buds, flower, seed, fruit. All of the above organs are found only in angiosperms; Gymnosperms have no flower and fruit, ferns have no flower, seed and fruit, and bryophytes have only a shoot. The root and shoot are vegetative organs, the rest are generative. 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 used - these are organs used for reproduction, i.e. These 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. Generative organs and leaves never form on plant roots.

Functions:

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

Types of roots

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

All roots of the plant form root system- rod or fibrous. Dicotyledonous plants have a tap root system (except: great plantain), while monocotyledonous plants have a fibrous system. Taproot - the main root is clearly defined (bean, maple). The taproot 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. Root structure in a longitudinal section. The root apex is covered with a root cap (these are living cells that protect the apical meristem of the root). Starting from the root apex, the following zones are distinguished:

The division zone is located immediately under the cover.
Growth zone.
Suction zone.
The conduction zone in which lateral roots form.

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

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

In the conduction zone between the wood and the bast, a cambium appears, which is responsible for growth in thickness. The bark tissues cannot follow the secondary thickening and die, and thanks to the work of phellogen, a new covering tissue, a plug, appears on the root surface.

Absorption of water and mineral salts by roots occurs in all zones of the root, 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 takes place to the stem. There are two ways for water and substances dissolved in it to enter: through cell walls or through the living contents of cells. Osmosis is the absorption of water by a more concentrated solution into the cell. Thanks to osmosis, it is created root pressure– a force that promotes the one-way movement of water along the xylem from bottom to top (from root to stem).

Breathing of roots. The root absorbs oxygen and releases carbon dioxide during respiration. This is confirmed by the following experiment: if you place the root of a plant in a test tube for a while, then take it out and put a burning match into the test tube, the match will go out almost instantly.

Root modifications

A root vegetable 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 vegetable is to store nutrients.
Root tubers or root cones are thickening of adventitious roots (dahlia, sweet potato, chistyak). The main function is the supply of nutrients and vegetative propagation.
Bacterial nodules (legumes) are thickenings on the roots that contain bacteria. 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 throughout the plowed horizon, where they receive the required amount of water and air. When loosening the top layer of soil (cultivation), the soil crust is destroyed and the water and air conditions improve.

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

Picking – 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. Mineral fertilizers are divided into nitrogen (nitrate, urea), phosphorus (superphosphate, double superphosphate), potassium (potassium sulfate, potassium chloride), complex (contain phosphorus, nitrogen and potassium, for example nitrophoska) and microfertilizers (contain microelements - zinc, iron, boron , molybdenum). Organic materials include manure, peat, and bird droppings (guano). Nitrogen fertilizers are responsible for the growth and faster development of plants (increase in vegetative mass). Potash helps improve the quality of fruits, enhances plant resistance to certain diseases, and increases frost resistance and drought resistance. Phosphorus improves the growth of the root system, increases the yield and improves its quality, accelerates the ripening of plants, and increases their resistance to drought. Microfertilizers promote the synthesis in the plant of substances necessary for growth and development. All fertilizers are applied in strictly defined quantities. Nitrogen fertilizers are applied in the spring, potassium and phosphorus fertilizers are usually applied in the fall. The use of fertilizers is possible in dry form (in the spring before sowing or in the fall when digging) and in liquid form - root and foliar feeding (solutions with a concentration of no 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- this is the section of the stem between two adjacent nodes. The angle formed by the leaf and the stem located above is called leaf axil.

Types of shoots

Erect - the stem occupies a vertical position.
Creeping - the stem occupies a horizontal position.
Creeping - the stem takes a horizontal position, and adventitious roots form on it (meadow tea).
Curly (beans).
Clinging (ranks).
Depending on the severity of the internodes: shortened and elongated.

Bud

A bud is an embryonic shoot.

Types of kidneys

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

Kidney structure. On the outside, most buds are covered with bud scales, which protect the bud and protect its internal contents from drying out. Inside are the rudiments of all plant organs: rudimentary leaves, rudimentary stem, rudimentary buds. Also inside the bud may contain the rudiments of future flowers. At the top of the embryonic stem there is a growth cone - this is educational tissue.

SHEET

A leaf is a vegetative organ of a plant, occupying a lateral position and providing aerial nutrition to the plants. Unlike other vegetative organs, the leaf is not characterized by unlimited (i.e. throughout its life) growth. Functions: f otosynthesis, water evaporation, gas exchange.

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

Types of leaves. Depending on the number of leaf blades, leaves are divided into simple(one leaf blade, there is no articulation between it and the petiole) and complex(one or many leaf blades separated from the common petiole). Among the compound leaves there are: trifoliate (clover, strawberry, oxalis), palmate (horse chestnut), paripirnate (yellow acacia) and imparipinnate (ash, rowan, rose hip).

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

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

Leaf arrangement- This is the order in which the leaves are placed on the stem. There are:

Regular leaf arrangement - only one leaf emerges from each node (birch, poplar, oak).
Opposite leaf arrangement - two leaves emerge from each node (lilac, maple, elderberry).
Whorled leaf arrangement - three or more leaves emerge from each node (oleander, raven's eye, elodea).

Sheet 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 shade each other, which allows for maximum use of solar energy.

Internal structure of the leaf. On the outside there is a covering tissue - the epidermis. The stomata are located mainly on the lower side of the leaf (in aquatic plants with floating leaves (water lily), on the contrary, the 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 surface of the leaf.

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

The leaf veins (vascular bundles) do not contain cambium. The wood is located closer to the upper surface of the leaf, and the bast is closer to the lower surface. Mechanical tissue is usually located outside the conductive bundle.

Processes occurring in the sheet

Photosynthesis – This is the process of formation of organic substances from inorganic substances using sunlight.
Gas exchange in plants occurs 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. During the day, two processes occur 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. This cools the plant, which prevents overheating; in addition, a continuous flow of water from the roots to the leaves is maintained. Plants can protect themselves 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 falling of leaves. In this regard, plants are divided into deciduous and evergreen. Evergreen plants are characterized by perennial leaves (pine leaves live 2-4 years, spruce leaves - 5-7 years). Deciduous plants lose all their leaves annually at the end of the growing season (oak, birch, maple). By the end of summer - beginning of autumn, the leaves begin to age, the intensity of metabolism in them decreases, chlorophyll and chloroplasts begin to break down, the leaves acquire a different color (not in all plants: for example, lilac leaves remain green). A separating layer of cells consisting of dead cork cells begins to form between the base of the leaf and the stem. At this time, a bud is finally formed in the leaf axil, after which the leaf falls off. The mark left by a fallen leaf on a stem is called a leaf scar. The meaning 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; reducing the mass of shoots and their area, which reduces the amount of snow retained on the branches, therefore reducing the likelihood of shoot breakage.

Leaf modifications

Spines – develop in plants living in conditions of insufficient moisture (cactus)
Antennae (peas, chin).
Trapping devices of insectivorous plants (sundew).
Scales are small, underdeveloped leaves (lily of the valley, peas).

Stem

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

Internal structure of the stem (using the example of linden)

Primary structure of the stem:

a) Primary cortex. On the outside is the epidermis, under which the main photosynthetic tissue is located. In addition to these tissues, the primary cortex also includes mechanical tissues (usually collenchyma).

b) A central cylinder in which conductive tissue and core are isolated. Conductive tissues are represented by xylem and phloem; they form conducting bundles. The core consists 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 shoot from the bud. Branching. In spring, sap flow begins in the plants, and the necessary substances enter the buds. The cells of the growth cone begin to actively divide, the rudimentary stem increases, the bud scales move apart and gradually fall off, and a bud ring forms in their place. The shoot grows and develops, new leaves and new buds form on it. A shoot that has developed from a bud in one growing season is called 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 the lateral buds. A type 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) intercalary educational tissues. Growth in thickness 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 the newly formed vessels decreases and more mechanical elements are formed. On a cross-section of a tree, these differences are visible to the naked eye in the form of growth rings. The annual ring is the growth of wood over the year based on the thickness of the stem. The age of the plant can be determined by the growth rings.

Transport of substances

Water moves through 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 through the bast in both directions: from leaves to roots (top to bottom) and from leaves to fruits and flowers (bottom to top).

Modifications of shoots:Overhead

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

Underground

Underground stolon. Performs the function of dispersal and vegetative propagation. Formed from buds at the base of the stem; usually white in color with colorless scale-like leaves. In plants such as potatoes and rosemary, a tuber is formed at the end of the stolon.
Tuber is a highly thickened underground shoot (potato, Jerusalem artichoke, corydalis, sedum). Performs the function of a supply of nutrients, ensures survival of unfavorable conditions, vegetative propagation and renewal.
A bulb is an underground shoot with a very short, flattened stem (bottom) and succulent leaves (lily, tulip, onion). Performs functions: supply of nutrients, survival of unfavorable conditions, renewal, vegetative propagation.
A corm is an underground shoot of a plant. It has dry, filmy leaves, and reserve nutrients are deposited in the stem (crocus, gladiolus, colchicum).
Rhizome is an underground or aboveground modified perennial shoot with scale-like or green leaves. Responsible for reproduction, settlement, supply of nutrients, renewal and waiting out unfavorable 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 the function it performs. There are vegetative and reproductive organs of the plant.

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

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 division of the plant body into organs and 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 reached land and adapted to life in the air and soil, their 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 revealed. As the plant grows, the size and weight of the body increase, cell division occurs and they 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 detected 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 conductive paths in a polar manner, 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; in this case, a distinction is made between the dorsal (dorsal) and ventral (ventral) sides (for example, leaves, as well as organs that grow 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, a change in their functions occurs, 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 shape 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 reaction to the unilateral action of external factors (light, gravity, humidity). The growth of axial organs towards light is defined as positive (shoots) and negative (main root) phototropism. Oriented growth of axial organs of a plant, caused by the unilateral action 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 present in rudimentary form in the embryo located in the mature seed. The embryonic shoot consists of an axis (embryo 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 embryo axis there is a shoot growth point. It is formed by a 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, the leaf primordia grow faster than the stem, with the young leaves covering each other and the growth 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 remaining portion of the embryonic axis, below the cotyledons, is called the hypocotyl, or subcotyledon. Its lower end passes into the embryonic root, which is so far represented only by a growth cone.

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

Almost simultaneously, a first-order shoot, or main shoot, develops from the embryonic 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 (moss mosses, horsetails, ferns), their body (sporophyte) develops from the zygote. The initial stages of the life of the sporophyte take place in the tissues of the growths (gametophytes). An embryo develops from the zygote, consisting of a rudimentary shoot and a root pole.

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

In all organs of a higher plant, three tissue systems - integumentary, conductive and basal - continue continuously 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 primary growth, which begins near the tips of the roots and stems, the primary ones are formed, which make up the primary body of the plant. Primary xylem and primary phloem and associated parenchyma tissues form the central cylinder, or stele, of the stem and root of the primary plant body. There are several types of steles.