Plant organs: their functions, structure and metamorphoses. Basic plant organs Which plant organ does not perform a function?

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.

Add to bookmarks:

Plant organs are divided into vegetative and generative.

The vegetative organs of plants carry out all the vital processes of the body, with the exception of sexual reproduction, while the generative organs of plants ensure the occurrence of this particular process. The vegetative organs of plants include the root and shoot, and the generative organs of plants include the flower, seed and fruit.

The root is an underground vegetative organ of plants. With the help of roots, plants absorb water and minerals from the soil, are fixed in it, transport water and minerals to the shoot, accumulate nutrients and can carry out vegetative propagation.

Plant roots are divided into main, lateral and adventitious. The main root originates from the seed embryo, and the adventitious roots extend from the shoot. Lateral roots of plants are formed on the main and subordinate roots. The collection of roots of a plant is called the root system. Depending on the severity of the main root, taproot and fibrous root systems are distinguished. In the first of them the main root is well expressed (carrots, cabbage), in the second there is no predominance of one of the roots (wheat, onions).

On a longitudinal section of a plant root, four zones are distinguished: the growth zone, the suction zone and the lateral root zone, as well as the root cap. Since plants are characterized by open growth, constant cell division and elongation occur in the growth zone. The root cap protects the growth zone from damage by solid soil particles. Its outer cells gradually mucus and slough off, facilitating the movement of the root in the soil.

In the suction zone, water and minerals are absorbed from the soil using root hairs, which increase the surface area. In the zone of lateral roots, transport of mineral substances absorbed by water into the shoot occurs. Here, the deposition of reserve substances and the formation of adventitious buds occur, with the help of which vegetative propagation is possible, for example in dahlias.

Plant organs - roots can enter into symbiosis with nodule bacteria and fungal mycelium, forming mycorrhiza. Nodule bacteria form growths on the roots of legumes and some other plants - nodules, and fix atmospheric nitrogen in a form accessible to plants. Mycorrhizal fungi provide minerals to the plant. In return, bacteria and fungi receive organic substances from plants. Modifications of the root are: roots(carrots, beets, radishes), root tubers (dahlia), supporting roots (ficus banyan), trailing root organs (ivy), respiratory roots (swamp cypress), aerial roots of orchids, etc.

A shoot is an above-ground plant organ consisting of a stem, leaves and buds. Ordinary leafy shoots are called vegetative, and those that also bear flowers or fruits are called generative.

Stem- axial part of the shoot. The stem brings leaves to the light, supports generative organs, transports water and substances dissolved in it, reserve substances are deposited in the stem, and it can take part in vegetative propagation. Young stems can perform the function of photosynthesis.

The plant stem is divided into nodes and internodes. At the nodes, leaves and buds are attached to the stem. Leaves can be attached one at a time to a node - this leaf arrangement is called alternate. If there are two leaves at the nodes, then this leaf arrangement is called opposite, and if there are more than two leaves, then this is a whorled leaf arrangement. The part of the stem located between the nodes is called the internode.

The stems are woody and non-woody. On a cross section of the stem of a perennial plant, the bark, represented by the integumentary tissue and underlying cells, phloem, cambium, wood and pith are visible. The bark protects the stem from various types of damage. Lub is a combination of phloem and mechanical tissue, wood is a combination of xylem, mechanical tissue and parenchyma. Cambium is an educational tissue, the cells of which, in the process of division, lay bast cells outward, and wood cells inward.

The core is represented mainly by parenchymal tissue; reserve substances or metabolic products can be deposited in it.

Sheet- organ of aerial nutrition of plants. The main functions of the leaf are photosynthesis, gas exchange, storage of substances and vegetative propagation. The leaf consists of a leaf blade, petiole and stipules. A simple leaf has one leaf blade, while a complex leaf has several leaf blades on one petiole. A cross section shows that the leaf blade is covered with skin or epidermis with a cuticle on top and bottom. The epidermis contains numerous stomata, bounded by two guard cells, between which there is a stomatal fissure. The epidermis may also have hairs. With the help of stomata, hairs and cuticles, the plant regulates the process of water evaporation - transpiration.

The leaf pulp is filled with two types of assimilation tissue. In the upper part of the leaf there is columnar parenchyma, the main function of which is photosynthesis, and in the lower part there is loose or spongy parenchyma, which, in addition to photosynthesis, also carries out gas exchange. The pulp of the leaf is penetrated by veins formed by complexes of conductive and mechanical tissues. The pattern of veins passing through the leaf blade is called venation. Venation can be parallel, arcuate, pinnate, reticulate, etc.

Bud represents a rudimentary shoot. It is covered with kidney scales that protect it from damage. Depending on which shoot rudiment is located in the bud, vegetative and generative buds are distinguished. They are also classified according to their position on the shoot (apical, axillary and lateral buds).

Modifications of the escape are rhizomes(lily of the valley, iris), bulbs (onion, tulip), tubers (potatoes), mustaches (strawberries), etc.

Flower- This is a modified escape. The function of a flower is to ensure sexual reproduction of plants. It consists of a peduncle, receptacle, perianth, stamens and pistil.

The receptacle and peduncle are a modified stem, and all other parts of the flower are derivatives of the leaves. The peduncle attaches the flower to the shoot. All other parts of the flower are attached to the receptacle.
The perianth is divided into a corolla and a calyx. The corolla is formed by petals, and the calyx is formed by sepals. A flower without a perianth is called naked, and one with only a corolla is called corolla, and only a calyx is called calyx.

In the center of the flower there is one or more pistils.
The pistil consists of an ovary, a style and a stigma. Inside the ovary there are one or more ovules containing eggs. The stamen is formed by a filament and anthers held together by a connective tissue. The anther contains pollen grains or pollen. A flower that has both stamens and pistils is called bisexual, a flower that bears only stamens is called male, and a flower that only bears pistils is called female. If both male and female flowers are located on one plant, then such a plant is called monoecious (pumpkin, cucumber), otherwise - dioecious (poplar, sea buckthorn).

For convenience, conventional notations are used in plant taxonomy - formulas and flower diagrams. The flower formula indicates the number of sepals (S), petals (L), stamens (T) and pistils (P). In this case, they take into account whether they are free or fused, and whether the differences between the members of the flower are too great, for example, in the length of the stamens.

Inflorescence called several flowers on one stem. The advantage of an inflorescence is that a large mass of flowers will always be more noticeable to pollinators than a single flower, and the death of one flower in an inflorescence will not lead to the disappearance of the plant's genetic information. Inflorescences are divided into simple and complex. Simple inflorescences include an ear (plantain), an ear (corn), a brush (colza), an earring (birch), a basket (sunflower), a shield (apple tree), a head (clover), an umbrella (onion) and others. Among the complex inflorescences are called a complex spike (wheat), a panicle (oats), a complex umbrella (carrots, dill) and others.

If you notice an error, select the required text and press Ctrl+Enter to report it to the editors

Flowering plants play a special role in the evolution of the organic world. The organs of flowering plants have reached a fairly high level of development, providing this group of organisms with a dominant position on the planet. Today they are found on almost every continent. For comparison, we can cite the statistical data contained in the section of the school botany course “Organs of flowering plants” (grade 6). Namely: among all 850 species there are representatives of gymnosperms, and 250 thousand are flowering plants.

Organs and functions of a flowering plant

Angiosperms are plants that produce flowers and fruit.

All plant organs can be combined into two groups. Vegetative plants include a shoot consisting of a stem and a leaf, as well as an underground part - the root. Flower, fruit and seeds are generative. Only flowering plants have them. The organs of flowering plants, depending on their structural features, perform certain functions. All of them play an important role in the functioning of organisms, determining their viability and adaptation to living conditions.

The organs and functions of a flowering plant are interconnected. Let's look at the structure of each of them in more detail.

Root

In the biology textbook, in the topic “Organs of flowering plants” (grade 6), a definition of the concept “root” is given. This is an underground organ that provides anchorage in the soil, nutrition with minerals, water supply, upward flow and vegetative propagation.

Various have flowering plants. The organs of flowering plants are diverse. There are main and side ones. They combine special structures. Their name is root systems.

Types of root systems

Taxonomists distinguish the tap root and the first is formed by a single main root and lateral roots extending from it. It is typical for representatives of the Dicotyledonous class.

Fibrous grows in a bunch immediately from the shoot. It is characteristic of all representatives of the Monocot family. These are, for example, Cereals, Lilies and Onions. Each system has a number of advantages. For example, plants with a long main root can easily obtain moisture from great depths. And the fibrous system provides a large suction area.

Escape and its modifications

It is flowering plants that are characterized by a large variety of above-ground parts. The organs of flowering plants sometimes change depending on environmental conditions. This is the adaptive ability of escape.

Its axial part is called the stem. The areas where leaves develop are called nodes, and the distances between them are called internodes. The angle between the blade and the stem forms the leaf axil.

The lateral parts of the stem are also very diverse. Leaves with one leaf blade are called simple, while leaves with several are called compound. They can be located differently on the plant. For example, the leaves of birch and sunflower are alternately in a spiral, while those of lilac and maple are opposite each other. Whorled is a leaf arrangement in which the blades develop in numbers of three or more in one node.

All vegetative organs perform the functions of asexual reproduction, mineral nutrition, photosynthesis and transpiration.

Organs of seed reproduction of flowering plants

A special organ of a flowering plant where sexual reproduction cells are formed is the flower. Its main parts are the pistil and stamen. The formation of germ cells occurs in them. The result of their fusion is the seed. It consists of an embryo formed by a root, a stalk, a leaf and a bud, and a shell.

The process of fertilization in flowering plants is preceded by pollination - the transfer of pollen from the stamen to the pistil. This happens with the help of insects, humans or wind. Next, when the female reproductive cell and one sperm merge, an embryo is formed. The second unites with the central germ cell, forming the endosperm. This is a reserve nutrient that the embryo uses to carry out the processes of growth and development.

A seed surrounded by shells is called a fruit. They are also varied. According to the structure of the pericarp, they are divided into dry and juicy, and according to the number of seeds - single- and multi-seeded. With the help of fruits, plants spread and disperse. Humans, in turn, use them as food. He also controls the number of plants used for his own purposes.

Unusual plants

The organs of flowering plants are often impressive in their shape and size.

A representative of the gymnosperms, the amazing Welwitschia visually resembles a ball of snakes. This is exactly what its long, wide leaves look like, reaching a length of up to two meters. The plant grows in deserted open landscapes, where strong wind currents tear the leaves of Welwitschia along. This creates the effect of a snake's nest. And the escape itself is underground.

Under the supporting roots of the ficus banyan tree, which number about 4 thousand, 5,000 people can easily fit.

Sundews and bladderworts are very sticky and have specialized digestive glands or closing traps. The thing is that they are predatory plants capable of assimilating proteins of animal origin. They can feed on small insects, crustaceans and fish fry.

Vegetative and flowering plants have a complex structure, which determines the performance of functions and ensures their predominance on Earth.

In higher plants, organs are distinguished vegetative And generative. TO vegetative organs include root, stem, leaf; To generative – flower, fruit and seed.

The root is the axial vegetative organ of the plant, which has positive geotropism and unlimited growth. It performs the following functions:

Fixes the plant in the soil;

Absorbs water and mineral salt solutions

Serves as a storage place for reserve nutrients;

Participates in breathing;

Synthesizes biologically active substances (hormones, alkaloids, vitamins, amino acids);

Releases various amino acids into the soil;

Carries out symbiosis with various organisms.

The number of roots in one plant can be very large - hundreds, thousands, and sometimes several millions. The degree of their development depends on environmental conditions. The collection of all the roots of one plant is called root system . Three types of roots can be distinguished in it; main, lateral and subordinate ones. Main the root develops from the radicle of the embryo during seed germination. Lateral roots develop on lateral and adventitious roots . Subordinate clauses roots form on the lower part of the stem and on the leaves. The root system in which the main root is expressed is called core . This root system is typical for most dicotyledons plants. If the embryonic root dies early or its growth slows down, then the root system consists of adventitious and lateral roots and is called fibrous. This system is typical for monocots plants. Often the roots perform additional functions and are modified. Modifications of the roots are: roots – modifications of the main root, rich in reserve nutrients (carrots, parsley, beets, radishes); root tubers – thickening of adventitious roots (dahlia). Some plants develop above-ground roots of the following types: 1) aerial - formed Fig. 19. Types of roots: on stems and hanging down, performing the functions of additional - 1-main, 2-lateral, respiration and water supply (orchids); 2) stilts - 3-adnexal shoots from the trunk, reach the soil surface and penetrate into it

(mangrove plants of the tropics); 3) support roots - hanging from tree branches, reaching the soil and strengthening in it, providing additional support and nutrition (banyan tree); 4) clinging (ivy); 5) respiratory - rise above the surface of the yuolot and provide breathing to the roots (marsh plants of the tropics).

Fig. 20. Root systems: Fig. 21: Root zones: Fig. 22 Root 1-stem, 2-fibular hairs

Plant roots have a cellular structure; cells differ in structure and functions. On a longitudinal section of the root, several sections (zones) can be distinguished: root cap, division zone, growth zone, absorption zone, conduction zone. The root tip is covered root cap. Its cells adhere tightly to each other, secrete mucus, perform a protective function and determine the direction of root growth. The cells of the cap do not live long, quickly die, slough off and are replaced by new ones. In the division zone there are small cells with thin walls. They divide intensively - these are cells of educational tissue. Having stopped dividing, the cells of the division zone stretch along the axis of the root and increase in size. They make up the following zone - growth zone or stretching. At a distance of 2 - 3mm from the root tip there is suction zone or zone root hairs . Root hairs visible to the naked eye and look like a white fluff. A root hair is a protrusion (up to 10 mm long) of a root skin cell. It is covered with a cell membrane, under which there are cytoplasm, nucleus, leukoplasts, vacuole with cell sap, and mitochondria. Root hairs live for 10–15 days, then die off and are replaced by new ones. Penetrating between soil particles, they absorb water and minerals dissolved in it. The supply of a solution of mineral salts to the root hair is ensured by the difference in their concentration in the soil and cell sap (through their diffusion and active transport). Next, these solutions move through the parenchyma from cells with less suction force to cells with greater suction force. The magnitude of the suction force is determined by the difference between osmotic and turgor pressure. Turgor pressure - this is the pressure that the living contents of the cell exert on its membrane. The movement of a solution of mineral salts from the root up through the vessels is ensured by root pressure, which forcefully pushes the solution from the root cells into the vessels, and by the evaporation of water by the leaves. Behind the suction zone is venue area.

For normal plant development, the roots must receive moisture, air, and the necessary mineral salts. Plants get all this from soil - the top fertile layer of the earth. The composition of the soil includes humus, sand, clay, air, water, and mineral salts. To increase soil fertility, fertilizers are added to it.

Plants, like all living things, are made up of cells. Hundreds of cells of the same shape and with the same function form a tissue; an organ is made up of several tissues. The main organs of a plant are roots, stem and leaves, each of them performs a very specific function. Important organs for reproduction are flowers, fruits and seeds.

Roots

Roots have two main functions: the first is to nourish the plant, the second is to anchor it in the soil. Indeed, the roots absorb water and mineral salts dissolved in it from the ground, thus ensuring a constant supply of moisture to the plant, which is necessary both for its survival and for its growth. That is why it is so important to prevent the plant from wilting and drying out and watering it regularly during hot and dry times.

The part of the root visible from the outside is the growing, smooth, hairless part where maximum growth occurs. The growing point is covered with a thin protective shell, the root cap, which facilitates the penetration of the root into the ground. The suction zone, located near the growing point, is designed to absorb water and mineral salts needed by the plant; it is covered with thick fluff, which is easy to see with a magnifying glass and which consists of very fine roots called root hairs. The conductive zone of the roots performs the function of transporting nutrients. In addition, they also have a support function; they firmly anchor the plant in the soil. The shape, size, structure and other features of the roots are closely related to these functions and, of course, change depending on the environment in which they have to develop. Roots are usually underground, but aquatic and aerial are also found.

Even plants of the same species have roots of very different lengths, which depend on the type of soil and the amount of water it contains. In any case, the roots are much longer than we think, especially if we take into account the finest root hairs, whose purpose is to absorb; in general, the root apparatus is much more developed than the above-ground part of the plant located on the surface of the earth.

Stem

The main functions of the stem are support for the above-ground part and the connection between the root system and foliage, while the stem regulates the uniform distribution of nutrients throughout all internal organs of the plant. On the stem, where the leaves are attached, quite noticeable thickenings are sometimes visible, which are called nodes; the part of the stem between two nodes is called an internode. The stem has different names depending on its density:

The stem, if it is not very dense, like most herbaceous plants;

The straw, if it is hollow and divided, like cereals, by clearly visible nodes. Typically, such a stem contains a lot of silica, which increases its strength;

The trunk, if it is woody and branched, like most trees; or woody, but not branched, with leaves at the top, like palm trees.

Depending on the density of the stem, plants are divided into:

Herbaceous, which have a tender, non-woody stem;

Subshrubs, in which the stem lignifies the trunk only at the base;

Shrubs, in which all the branches are lignified, branch from the very base;

Arboreal ones, in which the trunk is completely lignified; it has a central axis (the trunk itself), which branches only in the upper part.

Based on the lifespan associated with the life cycle, herbaceous plants are usually classified as follows:

Annuals, or perennials, if they grow only one year and die after they have flowered, produced fruit, and dispersed seeds;

Biennials, or biennials, if they grow for two years (usually in the first year they only have a rosette of leaves, in the second year they bloom, bear fruit, then dry out);

Perennials, or perennials, if they live more than two years, usually bloom and produce fruits every year, and “rest”, that is, their above-ground part dies off in cold or dry times, but the underground part of the plant remains alive. There are plants in which part of the stem can change and turn into a real storage organ. Usually these are underground stems that serve for vegetative propagation, as well as for preserving the plant during unfavorable periods for growth. The most famous of them are tubers (like potatoes), rhizomes (iris) and bulbs (narcissus, hyacinth, onion).

Leaves

Leaves have many different functions, the main one is the already mentioned photosynthesis, that is, a chemical reaction in the leaf tissue, with the help of which not only organic substances are created, but also oxygen, which is necessary for life on our planet. Typically a leaf consists of a petiole, a more or less wide leaf blade supported by veins, and stipules. The petiole connects the leaf to the stem. If there is no petiole, then the leaves are called sessile. Inside the leaf there are vascular-fibrous bundles. They continue in the leaf blade, branching, forming a dense network of veins (nervation), through which the plant juice circulates, in addition, they support the blade, giving it strength. Based on the location of the main veins, different types of venation are distinguished: palmate, pinnate, parallel and arcuate. The leaf blade, depending on which plant it belongs to, has different densities (hard, juicy, etc.) and completely different shapes (round, elliptical, lanceolate, sagittal, etc.). And the edge of the leaf blade gets its name depending on its structure (solid, serrated, serrated, lobed, etc.). If the notch reaches the central vein, then the lobes become independent and can take the form of leaflets, in which case the leaves are called compound, they, in turn, are divided into palmate-compound, pinnate-compound, and so on.

Flowers

The beauty and originality of the shapes and colors of flowers have a very specific purpose. From time to time, nature supplies the flower with all this, that is, the tricks and devices developed over centuries, just so that its species continues. A flower, which has male and female organs, must undergo two most important and necessary processes to achieve this goal: pollination and fertilization. Typically, higher plants have bisexual flowers, that is, they contain both male and female organs. Only in some cases are the sexes separated: in dioecious plants, such as willow, holly, and laurel, male and female flowers are on separate specimens, while in monoecious plants, such as corn and pumpkin, both male and female flowers are placed separately on the same plant. In fact, all the parts that make up a flower are different modifications of the leaf that have evolved to perform different functions.

Above the peduncle you can see a thickening called the receptacle, on which different parts of the flower are located. The double or simple perianth is the outer and most striking part of the flower; the perianth in the truest sense of the word covers the reproductive organs and consists of a calyx and corolla. The calyx consists of leaves, usually green, called sepals, their task, especially during the period when the flower is in the bud stage, is to protect the internal parts. When the sepals are fused together, like in a carnation, the calyx is called fused-petal, and when they are separated, for example, like in a rose, the calyx is septate. The calyx rarely falls off, and in some cases it not only remains, but also grows to better perform its protective function. The corolla - the second element of the perianth - consists of petals, usually brightly colored and sometimes pleasantly scented. Their main function is to attract insects in order to facilitate pollination and, accordingly, reproduction. When the petals are more or less welded together, the corolla is called fusionpetal, and if they are separated, then septate. When there is no obvious difference between the calyx and the corolla, as, for example, in a tulip, the perianth is called simple corolla, and the flower itself is simple. The reproductive male apparatus of a flower, or androecium, consists of a variable number of stamens, consisting of a sterile, thin and elongated stalk called the filament, at the top of which is an anther, which contains pollen sacs. Flower pollen, the fertilizing male element, is usually yellow or orange.

The reproductive female apparatus of a flower, or gynoecium, is formed by one or more pistils. Each of them consists of a lower hollow and swollen part, called the ovary, containing one or more ovules, the upper thread-like part is called the style, and its apex, designed to collect and hold pollen grains, is called the stigma.

Flowers on a plant can be located one at a time, at the top or in the axils of the branches, but more often they are combined into groups, the so-called inflorescences.

Among the inflorescences, the most common are the following: inflorescences formed by flowers on peduncles: a raceme, such as wisteria, a panicle (lilac), an umbel (carrot) and a corymb, like a pear. Inflorescences formed by stemless, that is, sessile flowers: spike (wheat), catkin (hazel), basket (daisy).

Pollination

Very often, wind, water, insects and other animals take an unwitting part in the most important operation of pollination necessary for plant reproduction. Numerous insects, such as bees, bumblebees and butterflies, land on flowers in search of nectar, a sugary substance found in nectaries located in the inside of many flowers. When they touch the stamens, pollen from the ripe anthers falls on them, and they transfer it to other flowers, where the pollen lands on the stigma. This is how fertilization occurs. The bright colors, attractive shape and aroma of flowers have a very specific function of attracting pollinating insects, which transfer pollen from one flower to another.

Pollen, especially very light pollen, which can be very abundant in plants with small flowers without a corolla and therefore not attractive to insects, is also carried by the wind. It is this pollen, carried in huge quantities through the air, that causes most spring allergies.

Fruits and seeds

After fertilization, the walls of the ovary undergo profound changes, become lignified or become fleshy, they form a fruit (or pericarp, testis), and at the same time the ovules develop. Accumulating a supply of nutrients, they turn into seeds. Often, when the fruit is ripe, it is tasty, fleshy, brightly colored and smells pleasant. This attracts animals; by eating it, they help spread the seeds. If the fruit is not brightly colored and fleshy, then its seeds will spread differently. For example, the fruit of the meadow dandelion has light fluffs that resemble a small parachute, and the fruits of maple and linden have wings and are easily carried by the wind; other fruits, for example, burdock, have hooks with which they cling to the wool of sheep and to human clothing.

Among the fleshy fruits, the most famous are the drupe, which contains one seed inside, protected by the pericarp (cherry, plum, olive), and the berry, which usually contains many seeds and is immersed directly in the pulp (grapes, tomato).

Dry fruits are usually divided into dehiscent (cracking) and non-dehiscent (non-cracking) depending on whether they open on their own when ripe or not. For example, the first group includes beans, or legume pods (peas, beans), leaflets (lewkoy, radish, alyssum), capsule (poppy) and achene (wrestler). The fruits of the second group always contain one seed, practically welded to the fruit itself. The most famous examples are the caryopsis in cereals, the lionfish in maple and elm, and the achene with pappus in Asteraceae.

Inside the fruit there is a seed that contains an embryo, practically a future plant in miniature. Once in the soil, where the seed can germinate, it emerges from a state of dormancy, in which it can sometimes remain for several years, and begins to sprout. Thus, the seed completes its function, that is, protecting and nourishing the sprout, which could not exist independently, and a new life begins.

,
,