Basic terms and concepts (Vegetative organs of plants). Vegetative organs Lateral organ of a plant
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
Vegetative organs – organs that perform functions related to the individual life of each plant, providing mineral nutrition, photosynthesis, respiration, vegetative reproduction, etc. These include the root, stem, leaf and most of their modifications, or metamorphoses (bulb, tuber, rhizome, etc.). The root, stem and leaf are already embedded in the embryo of the seed. They are main bodies higher plants.
Root
Root– an axial vegetative organ of plants of unlimited growth with positive geotropism, the main functions of which are the absorption of water and minerals from the soil and the fixation of the plant in the substrate. Thanks to the formation of adventitious buds, the roots can serve as organs of vegetative propagation. Organic compounds can be synthesized in the roots and various substances (sugars, starch, etc.) can be stored. Through the roots, certain metabolic products are released and the plant interacts with other organisms, including bacteria and fungi.
Plants have a main root, as well as adventitious and lateral roots. main root develops from the root of the seed embryo, grows vertically downwards, it is usually thicker and longer than other roots. Adventitious roots occur on the stem and other plant organs. They are formed in the lower part of the stem during the hilling of many flower crops, as well as on creeping stems (lesser periwinkle, loosestrife), on the bottom of bulbs (hyacinth, narcissus, tulip), during rooting of mustaches and plant cuttings. Thanks to adventitious roots, vegetative propagation of plants is possible - by cuttings, rhizomes, layering, and bulbs. On the main root are formed lateral roots. Lateral roots extending from the main one are called first-order roots. Roots of the second order depart from them, etc.
Root system – This is the totality of all the roots of a plant. There are taproot, fibrous and mixed root systems.
Tap root system has a well-defined main root, growing faster than the lateral ones, and is characteristic mainly of dicotyledonous plants (levy, salvia, eschscholzia, etc.).
Fibrous root system formed by adventitious roots extending from the lower part of the stem. The main root does not develop or is poorly developed and does not differ in appearance from other roots. This root system is characteristic mainly of monocots (for example, ornamental grasses) and some dicotyledonous plants (for example, marigolds).
Mixed root system formed with the participation of the main, lateral and adventitious roots (creeping tenacious).
When growing young plants from seeds, they practice pinching the tip of the main root, as a result of which the growth of lateral roots is enhanced and a branched root system is formed. This technique is widely used for seed propagation of annual and biennial open ground crops and some beautiful flowering potted plants. During vegetative propagation of flower crops (begonia, carnation, chrysanthemum, etc.), a fibrous root system is formed, because adventitious roots develop.
Some ornamental plants, along with ordinary ones, form modified roots: storage, aerial, root-trailers, etc.
Storage roots are formed from lateral or adventitious roots and are called root tubers or root cones. They are thick, fleshy and perform the function of storing nutrients (dahlia, night violet).
Aerial roots- these are adventitious roots on stems that are brown or yellow in color and hang freely in the air in the form of cords (monstera, orchids, tetrastigma). On the surface of the aerial roots, a special tissue is formed - velamen, which is capable of absorbing rain moisture and retaining it for a long time. The flat or flattened roots of epiphytic plants (such as many tropical orchids) can attach to the above-ground parts of other plants, contain chloroplasts, and participate in photosynthesis. The ability to form aerial roots is retained in such plants even when grown in greenhouses or indoor cultivation.
Trailer roots often formed in vines (for example, common ivy). They are modified adventitious roots that help lift the stem along the support (tree trunks, walls, slopes, etc.), which allows the use of vines for vertical gardening.
Stilt roots are formed from numerous adventitious roots in the lower part of the trunks of tropical trees that live along the banks of rivers, on the coastal shallows of the oceans, and swamps. Such roots take on an arched shape, raising the trunk above the water, protecting it from flooding by tides (some types of palm trees, ficus bengal, etc.).
Retractors, or contractile, roots are formed in young bulbous (tulip), corm (gladiolus, crocus, freesia), and some rhizomatous (hybrid iris) plants. These are thickened, transversely wrinkled roots that are easily distinguished from ordinary roots. Due to the ability to contract in the longitudinal direction, they pull the bulb, corm or rhizome deep into the soil, thus ensuring that they survive unfavorable periods, for example, cold or dry periods.
Stem
Stem is an axial vegetative organ of unlimited growth with negative geotropism, which bears buds, leaves, flowers and fruits. During seed germination, the stem develops from the embryonic bud. During vegetative propagation of plants, it is formed from buds formed on the organ of vegetative propagation (rhizome, corm, cutting, etc.).
Functions of the stem are diverse: supporting, conducting, storing, photosynthesizing, protective, etc. The stem provides the most favorable placement of photosynthetic organs to light sources. Water with minerals dissolved in it moves along the stem from the roots to the leaves (upward current), and organic substances move from the leaves to the roots (downward current). The stems can store nutrients such as starch (cycads) and water (cacti). Storage stems can take different shapes: bulbous, round, cylindrical, or others. In most herbaceous plants, the stem is green in color, contains chlorophyll and is involved in photosynthesis. The stems also serve to protect plants from being eaten by animals (hawthorn).
The stems of ornamental plants are varied in structure and life expectancy, the nature of the surface, cross-sectional shape, placement in space, height and other characteristics. In ornamental woody plants (hydrangea, palm, rose, lilac), they are perennial, woody, have a cambium (educational tissue consisting of actively dividing cells) and live from several tens to several hundred and even thousands of years. In ornamental herbaceous plants, the stems usually die off in the winter, do not have a cambium, or it exists in rudimentary form. Such stems live for 1 year, less often – 2–3 years.
By the nature of the surface stems can be smooth (most flower crops) and pubescent (some types of lilies, hybrid rudbeckia, Drummond phlox, etc.).
According to cross-sectional shape in floral and ornamental plants, round or cylindrical stems are more common, less often triangular (sedge), tetrahedral (thyme, sage), multifaceted (cereus), flattened (prickly pear), winged (ammobium, china), etc.
By location in space There are different types of stems:
– erect – grow vertically upward and do not need support (most plants);
– creeping – are located on the surface of the earth, easily take root in nodes with the help of adventitious roots (small periwinkle);
– creeping (lying) – are adjacent to the soil along the entire length, but do not take root (royal begonia);
– rising– mostly lie on the substrate, and a much smaller part of them rises (false sedum);
– ascending– have a base lying on the soil surface, and a much larger part of them rises (tricolor violet, Evers sedum);
– climbing – cling with tendrils or adventitious roots to a support, due to which they rise upward (common ivy, tetrastigma Voinier, fragrant china);
– curly – spirally wrap around a support (purple morning glory, fire red beans). Plants with climbing and twining stems are called vines and are widely used in vertical gardening.
Stems height largely determines the size of the entire plant. The stems of buzulnik, Volzhanka, delphinium, mallow, and strelitzia have the greatest height (up to 200 cm) among herbaceous ornamental plants during the flowering period. Stems up to 20 cm high are characteristic of small-bulbous (crocus, snowdrop, scilla) and many ground cover (aubrieta, awl-shaped phlox, etc.) perennial plants.
Despite the diversity of stems, their growth is most often carried out due to the division and growth of cells of the growth cone (apical bud) - apical growth. Some flower crops (aquilegia, astilbe, gerbera, calceolaria, primrose, etc.) develop shortened stem. In this case, the leaves form a basal rosette, above which flower-bearing shoots with flowers or inflorescences rise. Such stems usually grow from the base - intercalary growth– and are often leafless (arrow stems). Intercalary growth is also characteristic of the stems of ornamental cereals (gray fescue, maned barley, etc.).
With the development of apical and lateral buds, new shoots are formed, resulting in stem branching, which determines the growth pattern of the aerial part and its appearance. Shoots developing from the buds of the main stem are called first-order shoots. Shoots that are formed from buds located on shoots of the first order are shoots of the second order, etc.
Sheet
Sheet is a lateral vegetative organ of limited growth that grows at the base (monocots) or the entire surface (dicots).
Basic Sheet Functions– photosynthesis (synthesis of organic substances from carbon dioxide and water using solar energy), transpiration (evaporation of water) and gas exchange. Leaves can store nutrients and succulents can store water. In some plants (begonia, saintpaulia), the leaf is an organ of vegetative propagation. The leaves of most herbaceous floral and ornamental plants live no more than one growing season, evergreens - 1-5 years, and sometimes (araucaria) - up to 10-15 years.
In most plants, a leaf consists of a blade and a petiole. Plate- the extended flat part of the sheet that performs its main functions. petiole- the stem-shaped part of the leaf, with the help of which the blade is attached to the stem. Depending on the method of attachment of the leaf to the stem, there are petiolate And sedentary leaves.
In some flowering and ornamental plants (white cinquefoil, fragrant china, etc.) at the base of the petiole there are stipules, most often paired, herbaceous or filmy, performing protective or photosynthetic functions.
Leaf sizes Floral and ornamental plants are very diverse. Their length varies from a few millimeters (aubrieta, soleirolia) to 10–20 m or more (some types of palm trees).
Leaf color is the most important decorative feature. Based on this feature, the following types of leaves are distinguished: plain(leaf blades are green on both sides); colored(leaf blades are painted any color except green); colorful(the upper and lower sides of the leaf blade are painted in different colors); spotted(there are spots of different sizes and colors that differ from the main color of the leaves); variegated(separate sections of the leaf blade are painted in different colors); bordered(there is a stripe of a different color along the edge of the leaf blade).
By consistency distinguish between grassy leaves (thin, soft); filmy (small, translucent, dry); leathery (dense, hard); fleshy, or juicy (thick, juicy), and by the nature of the surface– bare (matte or glossy), pubescent (covered with hairs), with a waxy coating.
According to the features of the external structure There are simple and compound leaves.
Simple sheet have one leaf blade, whole or dissected. A leaf is called dissected if the cuts along the edge of the leaf blade reach ¼ of the width or more. In herbaceous plants, simple leaves most often die off along with the stems, while in woody plants they usually fall off in the fall.
Simple leaves with a whole blade in turn classified by:
– plate shape– round, ovoid, lanceolate, oblong, linear, etc.;
– the shape of the top of the plate– blunt, sharp, pointed, pointed, notched, etc.;
– plate base shape– heart-shaped, round, wedge-shaped, arrow-shaped, spear-shaped, etc.;
– shape of the edge of the plate– entire, serrated, doubly serrated, jagged, crenate, notched, etc.
Simple leaves with a dissected blade classified:
– by excavation depth– lobed (cuts with a depth of no more than ¼ of the width of the leaf blade), separate (cuts more than ¼ of the width of the leaf blade, but do not reach the main vein or base of the leaf), dissected (cuts reach the main vein or base of the leaf);
– according to the location of the recesses– trifoliate, palmate, pinnate.
Sometimes the plate is cut twice (cosmea), three times (eschscholzia) or multiple times (yarrow).
Complex sheet consists of several (two or more) leaves, which are attached to a common petiole - rakhis. In such a leaf, the leaves first fall off, and then the rachis. Compound leaves are classified according to the arrangement of leaflets on the rachis:
– palmate compound– leaflets are located at the end of a common petiole in the same plane and diverge more or less radially; a variety of such leaves are trifoliate, or trifoliate leaves, consisting of three leaflets;
– pinnately– the leaves sit in pairs on a common petiole, and at its apex there can be one (opipirpinnate) or two leaflets (paripirnate). Pinnate leaves can have a more complex structure when two (double-pinnate), three (tri-pinnate) or more (multi-pinnate) leaves sit on a common petiole.
Depending on environmental conditions and the functions performed by the leaf, its modifications, or metamorphoses, occur in floral and ornamental plants:
– spines, which perform a protective function and are characteristic of plants in arid habitats (cacti);
– mustache, performing a supporting function in liana plants (fragrant vine);
– sepals, petals, stamens, pistils, which are parts of a flower of leaf origin and perform various functions: sepals and petals - protective and signaling, attract pollinators; stamens and pistils participate in the formation of female and male gametes;
– scales protect buds, bulbs or corms from adverse weather conditions, and also serve to accumulate nutrients in the bulb (hyacinth, narcissus, tulip).
The escape
The escape- this is a stem with leaves and buds or only buds, representing the annual end of the branches.
The part of the stem that bears leaves (buds) is called knot, and the section of the stem between adjacent nodes is internode. Internodes can be long ( elongated shoots) or short ( shortened shoots). The angle between the stem and the leaf is called leaf axil. The placement of leaves on the shoot can be regular (spiral) And two-row)– when there is only one leaf in a node (begonia, petunia); opposite– when there are two leaves in a node, one opposite the other (verbena, fuchsia) and whorled– each node contains three or more leaves (oleander).
Bud It is a rudimentary shoot with shortened internodes, which is in a state of relative dormancy. The first shoot of the plant develops from the bud of the seed embryo. The escape usually ends apical, or apical bud. Located in the leaf axils axillary, or lateral buds, from which side shoots develop. The placement of buds on the shoot, as a rule, corresponds to the leaf arrangement.
Based on the characteristics of the internal structure (content), vegetative, generative and mixed buds are distinguished. From vegetative (growth) buds a shoot with leaves is formed from generative (floral)- flowers or inflorescences, from mixed- leafy shoot with flowers. The generative buds of many flowering and ornamental plants differ from the vegetative ones in size and shape; they are usually larger and rounder (lily of the valley, lilac).
When unfavorable weather conditions occur, in temperate latitudes in autumn, and in the tropics during dry periods, the buds of perennial plants enter into seasonal dormancy, which can last several months. Such kidneys are called resting, or wintering. On the outside they are usually covered with dense covering scales, performing a protective function. The buds of some shrubs and trees of the humid tropics, as well as most herbaceous plants, do not have protective scales.
Some of the buds on the shoot, usually located near its base, do not germinate in the spring, but can remain dormant for a long time (for oak up to 100 years, for birch - up to 50, for hawthorn - up to 25 years). Such kidneys are called sleeping. They awaken and begin to grow when plants are damaged or pruned and are of great importance in restoring the decorative qualities of trees and shrubs.
An equally important role is played accessory (adventitious) buds, which, unlike dormant ones, can be formed on different parts of the plant - in the nodes and internodes of the stem, on the roots, rhizomes and even leaves. Their formation is also associated with damage or pruning of plants or exposure to any irritant. The ability of plants to form adventitious buds and develop new shoots from them is widely used in practice for vegetative propagation of plants and their restoration after exposure to damaging factors.
Along with typical shoots, floral and ornamental plants often develop modified shoots, which is associated with their performance of certain functions - storing nutrients and water, securing the plant to a support, protection from unfavorable conditions and from being eaten by animals, etc. Modified shoots can be underground or aboveground. TO underground modified shoots include rhizome, tuber, bulb, corm, etc.
Rhizome – this is a modified underground shoot that can grow horizontally (aspidistra, hybrid iris, chrysanthemum) or vertically (zantedeshia, Siberian iris, primrose). Unlike the root, the rhizome has nodes, underdeveloped scale-like leaves and internodes. Adventitious roots are formed along the entire length of the rhizome, and above-ground shoots, leaves, and peduncles develop at the nodes. The young part of the rhizome ends with an apical bud. The rhizome lives from 2 to 25 years or more; it often accumulates reserve nutrients in the form of soluble sugars or starch (Alstroemeria).
WITH tolons- intensively growing underground shoots that quickly separate from the mother plant and end with a bud that gives rise to a new plant (zantedeshia, crocus, lilac, freesia, chrysanthemum).
Caudex (stem root) develops in some perennial floral and ornamental plants, together with the root it performs the function of accumulating nutrients and forms a large number of renewal buds (heuchera, delphinium, peony, paniculate phlox).
Tuber- This is a modified underground shoot of a rounded shape with a very thickened stem, in which reserve substances (starch, less often - oils) accumulate. It is formed as a result of thickening of the subcotyledon (hypocotyl). The top of the tuber is covered with dense covering tissue; the base and top can be easily distinguished from it. In the upper (apical) part of the tuber, most of the buds are concentrated, from which leaves and peduncles develop. Tubers of stem origin are characteristic of tuberous begonia, gloxinia, and cyclamen.
Bulb is a modified underground shoot in which the leaves have turned into bulbous scales attached to a shortened stem (the bottom of the bulb). In the juicy fleshy scales, reserve nutrients (soluble carbohydrates) accumulate. At the top of the bottom there is an apical (central) bud, from which a flowering stem with a flower or inflorescence, as well as leaves, develops. In the axils of the succulent scales, lateral buds are formed, giving rise to baby bulbs. Adventitious roots grow from the bottom of the bulb.
There are filmy and imbricated bulbs. Membranous bulb the top is covered with dry protective scales, and its succulent scales completely cover one another (hyacinth, daffodil, tulip). In a dormant state, such a bulb loses its adventitious roots. imbricated bulb devoid of protective scales, its succulent scales are arranged in a tiled pattern, and the roots do not die off (lily).
Corm – a modified underground shoot that stores nutrients in a thickened and shortened stem base, covered on top with filmy or leathery scales (gladiolus, crocus, freesia). The corm is usually shorter and wider than the bulb. In shape and internal structure, the corm resembles a tuber, but on top, like the bulb, it is covered with the bases of dead leaves, which cover it and protect it from drying out and damage. The roots grow from the base of the corm, which is usually concave in shape. In the axil of each leaf on the surface of the corm there is a bud. Their buds, located in the upper part of the corm, develop a flowering shoot.
Some floral and ornamental plants develop aboveground modified shoots. In this case, both individual parts of the shoot (stem, leaves, buds) and the shoot as a whole can change. In plants growing in arid areas, shoots often serve the function of storing water. Such plants are called succulents(from Latin succus - juice, juicy). According to the organ that stores water, they are distinguished stem(cacti, spurge) and leafy(aloe, young, sedum, crassula) succulents. The stems of cacti are 90% formed by large cells of water-storing tissue, which not only serve as a kind of water reservoir, but also participate in photosynthesis.
Phyllocladia– stems or whole shoots that perform the function of leaves and have their shape (ferns). In this case, one gets the false impression that the flower formed on a leaf, like, for example, butcher's broom.
Cladodes– stems that perform the function of leaves, but do not have their characteristic shape (asparagus).
spines They are formed, as a rule, due to moisture deficiency and also perform a protective function. The spines are of stem (rose) or leaf (cacti) origin and often protect the plant from being eaten by animals.
Mustache They are modified side shoots and serve to attach plants to a support (tetrastigma, cissus).
Scourge– shoots that grow horizontally and take root at the nodes (periwinkle).
Mustache– horizontally growing shoots with long internodes, which usually take root at the apical buds and form a rosette of leaves (creeping tenacious).
Bulbs (bulbs) arise as aboveground modified shoots in the axils of leaves (tiger, white, bulbous lilies) or in inflorescences. They have the appearance of small spherical formations, contain reserve substances, due to which they can serve as organs of vegetative reproduction.
An organ is a part of a biological multicellular organism that performs one or more functions that ensure its vital activity. According to its main purpose, it can be vegetative or generative. The vegetative part of plants includes the root, the main stem with shoots, buds, and leaves. Generative is represented by flowers, fruits and seeds.
Vegetative organs
The Latin word vegetatio means excitement, revitalization, growth. The growing season is the time period from awakening to the beginning of the plant's dormant period, during which its active growth occurs. At this time, the body of plant organisms is formed. It consists of vegetative organs that support the life of the plant, providing it with water supply, nutrition, controlling photosynthesis and other metabolic processes with the environment.
Biologists believe that vegetative organs were formed through the evolution of the thallus of unicellular algae in the process of adaptation to the conditions of a terrestrial lifestyle when areas of land and sea changed during fluctuations in the earth's surface.
General features of the structure of vegetative organs include:
polarity, when the top and base of the plant are in opposite directions of one straight line, that is, at different poles;
geotropism is the ability of various plant organs to sense the gravity of the earth and grow in a certain direction in relation to the center of the globe.
The roots are characterized by positive geotropism, since the direction of their growth coincides with the direction of gravity. The ground parts are negative, since they grow in the opposite direction from the action of gravity.
Orthotropic organs - the main shoot and the main root. They always grow vertically upward and vertically downward, respectively. Plagiotropic organs are lateral shoots and lateral roots that are located parallel to the plane of the earth or at an angle to the orthotropic ones. This arrangement of parts allows the plant to provide itself with the necessary nutrients, carbon dioxide, and lighting.
An underground vegetative organ, the root, is characterized by unlimited growth. Its main functions include providing the plant body with nutrition, water, and fixation in the substrate.
The stem is an axial above-ground vegetative organ of unlimited apical growth. In many cases it is characterized by polysymmetry. It serves as a support for the leaves, ensures the delivery of nutrition in the form of solutions of essential minerals and optimal placement relative to light sources.
The leaf is a lateral vegetative organ of limited growth. It consists of a leaf blade, stipules, and petiole. Sessile leaves without petioles are common. In monocotyledonous plants it grows at the base, in dicotyledonous plants it grows over the entire surface. The length of its life in annual plants is equal to the life expectancy of the entire above-ground part. On trees and shrubs it is a temporary, renewable organ. The main purpose of the leaf is to ensure the processes of photosynthesis, water evaporation, and gas exchange. In different species they can serve as sources of food and water supply. Perform a protective function with the help of spines, a cleansing function during leaf fall.
Vegetative plant parts - tendrils, rhizomes, bulbs, tubers, cuttings - are the main materials for the vegetative method of propagation, when a new plant organism is formed from the multicellular part of the maternal one.
The plant body, consisting of a large number of vegetative organs, is able to provide itself with the necessary photosynthetic surface, water and minerals in the required volume.
Generative organs
Reproductive or generative (from Latin generare - to produce) organs are a group of plant organs that ensure sexual reproduction. They appeared in the process of evolution much later than vegetative ones.
The main representatives of the group are flowers. They are different in shape and color, but are united by a common pattern of structure and fertilization. In its structure, a flower has a pistil, a stamen, a perianth, consisting of petals and a calyx. The process of sexual reproduction begins during flowering. During this period, pollen grains with male reproductive cells are formed on the stamens. They fall on the pistil, which contains seed buds with female eggs.
Fertilization occurs, which results in a seed with an embryo and endosperm. It is surrounded by a pericarp formed from the walls of the ovary. A fruit is formed. Once the seeds have gone through a period of dormancy, they are ready to germinate and form a new plant.
The described reproduction scheme is characteristic only of flowering plants, which do not include mosses, horsetails, and ferns. Their generative organs are arranged differently.
ROOT
The root is the axial vegetative organ of a plant, which has unlimited apical growth, positive geotropism, has a radial structure and never bears leaves. The apex of the root is protected by the root cap.
The meaning of the root is the anchoring of the plant in the soil, absorption of water and mineral salts, storage of organic substances, synthesis of amino acids and hormones, respiration, symbiosis with fungi and nodule bacteria, vegetative propagation (in root-sprouting plants).
The main root is the root that develops from the embryonic root.
An adventitious root is a root that develops from a stem or leaf.
Lateral root is a branch of the main, lateral or adventitious root.
The main root system is the main root with all the lateral roots and their branches.
Adventitious root system - adventitious roots with all lateral roots and their branches.
Taproot system is a root system with a well-defined taproot.
A fibrous root system is a root system represented mainly by adventitious roots, in which the main root is not distinguished.
Root vegetable is a modified, thickened main root that bears a shortened shoot at the base and performs the function of storing nutrients (carrots).
Root tuber is 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 growth cone, 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 size of cells increases and their specialization begins.
The suction zone is a zone that moves as it grows, where cells specialize into various tissues and water is absorbed from the soil using 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 area is covered with cork tissue.
The root cap is a protective, constantly renewing cell formation at the top of the growing root.
STEM
Stem is an axial vegetative organ of a plant, possessing unlimited apical 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, and 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-lignified shoots, the above-ground part of which dies in the fall, and the underground part with renewal buds overwinters.
An annual grass is a life form of a plant whose life cycle continues from seed germination to the formation of its own seeds and death, i.e. one growing season.
The main stem is the stem that develops from the bud of the seed embryo.
The growth cone 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 the stem from which a leaf emerges.
An internode is a section of a stem between two nodes.
The subcotyledon is the lower portion of the stem between the cotyledon node and the root.
The epicotyledon is the section of the stem between the node of the first true leaf and the cotyledon.
Apical growth - growth of the stem in length due to the work of the growth cone of the apical bud.
Intercalary growth is the growth of the stem in length due to the work of educational tissue at the bases of the internodes.
An erect stem is a stem that grows upward perpendicular to the surface of the earth.
A creeping stem is a stem that spreads along the surface of the soil and takes root with the help of adventitious roots.
Climbing stem – a stem that twines around a support.
A clinging stem is a stem that rises up, clinging to a support with the help of tendrils.
BUD
A bud is a rudimentary, not yet developed 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 is a bud that appears in the axil of a leaf, from which a lateral branching shoot is formed.
An adventitious bud is a bud formed outside the axil (on a stem, root or leaf) and giving rise to an adventitious (random) shoot.
Leaf bud – a bud consisting of a shortened stem with rudimentary leaves and a growth cone.
A flower bud is a bud represented by a shortened stem with the rudiments of a flower or inflorescence.
Mixed bud – a bud consisting of a shortened stem, rudimentary leaves and flowers.
Renewal bud is an overwintering bud of a perennial plant from which a shoot develops.
A dormant bud is a bud that remains dormant for several growing seasons.
THE ESCAPE
A shoot is a stem with leaves and buds, formed during one summer.
The main shoot is a shoot that develops from the bud of the seed embryo.
Lateral shoot is a shoot that appears from a lateral axillary bud, due to which the stem branches.
An elongated shoot is a shoot with elongated internodes.
A shortened shoot is a shoot with shortened internodes.
A vegetative shoot is a shoot that bears leaves and buds.
A flowering 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, in a cross section of which the following parts are distinguished: cork, bast, cambium, wood, pith.
Cork is a covering tissue consisting of several layers of dead cells; forms on the surface of wintering stems.
Bast (bark) is a complex of conductive (sieve tubes), mechanical (bast fibers) and main tissues located outward from the cambium; serves to carry carbohydrates from leaves to 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 the support of the stem and serves to conduct water and mineral salts from the roots to the leaves.
The growth ring is a layer of wood formed due to the work of the cambium during one summer.
The pith 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 during evolution. Similar modifications appear in representatives of different systematic groups of plants, which indicates convergence (homology) under homogeneous environmental conditions.
Rhizome is a modified perennial underground shoot with nodes, internodes, scale-like leaves and buds, serving for vegetative propagation, renewal and storage of nutrients (wheatgrass, horsetail, lily of the valley).
Tuber is a modified underground shoot formed at the top of the stolon, storing nutrients in the thickened stem part and serving for vegetative propagation (potatoes, Jerusalem artichokes). Bears axillary buds.
A stolon is an elongated creeping annual 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 scale-like leaves. The lateral axillary buds, growing, separate. 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 growth to the leaf blade and petiole. The base of the leaf sometimes takes the form of a tubular sheath or forms paired stipules.
The leaf blade is an expanded, usually flat part of the leaf that performs the functions of photosynthesis, gas exchange, transpiration and, in some species, vegetative propagation.
Petiole is a narrowed part of a 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, while those without petioles are called sessile.
Stipules are leaf-shaped structures at the base of the leaf that serve to protect the young leaf and axillary bud.
Leaf axil is the angle between the leaf petiole and the stem, usually occupied by a lateral axillary bud.
Leaf fall is the natural falling of leaves in woody plants and shrubs, associated with the preparation of plants for winter and due to changes in day length. A separating layer is formed at the base of the petiole, 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 off entirely.
A compound leaf is a leaf that includes several leaf blades (leaflets) located on a common petiole and falling off individually.
Whole leaf - a leaf that has an undivided leaf blade.
Lobed leaf – a leaf whose blade is divided into lobes up to 1/3 of the width of the half-leaf.
A split sheet is a sheet with a plate divided to 1/2 the width of the half sheet.
A dissected leaf is a leaf whose blade is dissected to the main vein or to the base of the leaf.
Leaf veins are a system of conductive bundles that bind the leaf into a single whole, serve as support for the pulp of the leaf and connect it to the stem.
Leaf venation is the order in which the veins are arranged in the leaf blade. With pinnate venation, the main vein is pronounced, from which the lateral veins extend in both directions; with palmate venation, the main vein is not expressed; the leaf includes several large veins, from which the lateral veins extend.
Reticulate venation – venation of the pinnate and palmate types. With parallel venation, several identical veins run parallel to each other along the blade from the base of the leaf to its tip.
Leaf arrangement is the arrangement of leaves on the stem that is most conducive to the performance of their function. With an alternate leaf arrangement, one leaf is attached to each node of the stem; with an opposite leaf arrangement, each node has two leaves opposite each other; with a whorled leaf arrangement, several leaves develop at a stem node.
The edge of the leaf blade is entire, jagged (right corners), serrated (sharp corners), crenate (rounded projections), notched (rounded notches).
INTERNAL STRUCTURE OF LEAF
The outer skin is the covering tissue on the side of the leaf facing the light, often covered with hairs, cuticle, and wax.
The lower skin is the covering tissue on the underside of the leaf, usually bearing stomata.
Stomata is a slit-like opening in the skin of a leaf, surrounded by two guard cells. Serves for gas exchange and transpiration.
Columnar tissue is the main tissue, the cells of which are cylindrical in shape, 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 round in shape, located loosely (many intercellular spaces), closer to the lower skin of the leaf. Serves for photosynthesis, gas exchange and transpiration.
Vein wood is part of the conductive bundle of the leaf, consisting of vessels through which water and minerals flow from the stem to the leaf.
The bast vein is part of the conductive bundle of the leaf, consisting of sieve tubes through which carbohydrates (sugars, glucose) move from the leaf to the stem.
Plants consist of organs such as vegetative and reproductive. Each of them is responsible for certain functions. Vegetative organs are responsible for development and nutrition, and the reproductive organs of plants are involved in reproduction. These include flower, seed and fruit. They are responsible for the “birth” of offspring.
Vegetative organs
The appearance of vegetative organs was associated with the need to obtain nutrients from the soil. These include:
- The root is the main organ of every plant growing in the ground.
- The escape.
- Stem.
- Leaves responsible for photosynthesis.
- Kidneys.
The root is characteristic of all plants, as it holds them and nourishes them, extracting useful substances from the water. It is from this that the shoots come from which the leaves grow.
When sowing seeds, the root is the first to sprout. It is the main organ of the plant. After the root gains strength, a shoot system appears. Then a stem is formed. It bears side shoots in the form of leaves and buds.
The stem supports the leaves and conducts nutrients from the roots to them. It can also store water during droughts.
Leaves are responsible for photosynthesis and gas exchange. In some plants they also perform other functions, such as storing substances or reproduction.
During the process of evolution, organs change. This allows plants to adapt and survive in nature. New species are appearing, which are increasingly unique and unpretentious.
Root
The vegetative organ that holds the stem is involved in the process of absorbing water and nutrients from the soil throughout the life of the plant.
It arose after the advent of sushi. The root helped plants adapt to changes in the earth. In the modern world, there are still rootless ones - moss and psilot-like ones.
In angiosperms, root development begins with the embryo entering the ground. As it develops, a stable organ appears from which a shoot sprouts.
The root is protected by a sheath, which helps to obtain nutrients. This is due to its structure and the content of a large amount of starch.
Stem
Axial vegetative organ. The stem bears leaves, buds and flowers. It is a conductor of nutrients from the root system to other plant organs. The stem of herbaceous species is also capable of photosynthesis, like the leaves.
It is capable of performing the following functions: storage and reproduction. The structure of the stem is a cone. The epidermis, or tissue, is the primary bark of some plant species. In peduncles it is looser, while in shoots, such as sunflower, it is lamellar.
The function of photosynthesis is performed due to the fact that the stem contains a chloroplast. This substance converts carbon dioxide and water into organic products. The supply of substances occurs due to starch, which is not consumed during the growth period.
Interestingly, in monocotyledonous plants the stem retains its structure throughout the entire life cycle. In dicotyledons it changes. This can be seen in the cut of trees where growth rings form.
Sheet
This is a lateral vegetative organ. Leaves vary in appearance, structure and function. The organ is involved in photosynthesis, gas exchange and transpiration.
- Brush - bird cherry, lily of the valley.
- The cob is of corn.
- Basket - chamomile or dandelion.
- Umbrellas are at the cherry tree.
- The shield is near the pear.
Complex inflorescences are represented by several simple ones. Their origin is related to the function of fertilization. The greater the number of flowers, the faster the pollen is transferred.
Fetus
The reproductive organs of plants primarily perform the function of reproduction. The fruit protects the seeds from their premature dissemination. They can be dry or juicy. Seeds are formed inside the fruit, gradually ripening. Some of them are equipped with devices that help them spread, for example, a dandelion scatters in the wind.
Main types of fruits:
- Single-seeded with three layers - cherry, apricot, peach.
- Multi-seeded with pulp - grapes.
A dry multi-seeded fruit comes with a partition - cabbage, and without it - peas. Oak has one seed.
The reproductive organs of flowering plants are designed so that seeds are dispersed in several ways:
- On water.
- By air.
- With the help of animals.
- Self-spreading.
The organs are designed so that plants undergo the process from root formation to reproduction. The fruits have adapted to be carried by animals. This is ensured by such devices as holds, parachutes, color accents and pleasant taste.
Seed
Knowing which plant organs are reproductive, you can understand exactly how they reproduce. The seed reproduces offspring and disperses them for subsequent cultivation. It consists of the peel, the germ and nutrients coming from the stem.
The seed contains proteins, fats and carbohydrates. In fact, the embryo is the rudiments of the stem, root and leaves. It is the main part of the seed and comes with one or two cotyledons.
Seeds also come in several different types. Some have nutrients in the endosperm, while others have no tissue for storage.
The seed coat protects from the external environment, wind and animals. Once mature, it helps disperse the plant. Some species store nutrients in the peel.
Seeds are food for people and animals. Their importance on earth is quite high, just like that of the fruit. These plant organs participate in the life cycle of insects and animals, thereby providing them with food.
Higher plants
In the plant world, everything is arranged so that organisms have the opportunity to grow constantly. Higher plants have organs such as shoots and roots. They differ in that during the process of fertilization an embryo appears.
The reproductive organs of higher plants, interacting with vegetative ones, change their life phases. They include four departments:
- Ferns grow in moist places. These include horsetails and mosses. Their structure includes root, stem and leaves.
- Bryophytes are an intermediate group. Their body consists of tissue, but they do not have blood vessels. They live in both wet and dry soil. Moss reproduces not only by spores, but also by sexual and vegetative means.
- Gymnosperms. The most ancient plants. Most often these include coniferous trees and shrubs. They do not bloom, and their fruits form a cone with seeds inside.
- Angiosperms. The most common plants. They differ in that the seeds are securely hidden under the skin of the fruit. Reproduction occurs in several ways. They differ in that they have female and male genital organs in their structure.
All these plants have been growing and developing on earth for quite a long time. They differ from each other in the method of reproduction and the presence of certain organs. However, it should be noted that vegetation has a great influence on human life.
Flowering plants
This species is the most numerous in the plant world. Flowering plants, or angiosperms, have grown on the planet since ancient times. In the process of evolution, ferns have divided into many species.
The main reproductive organs of flowering plants are the seeds. They are protected by the fruit, which helps them to be better preserved until they spread. Interestingly, this group of plants is the only one that can form multi-tiered communities. In turn, flowers are divided into two subspecies: monocotyledons and dicotyledons.
The main difference between flowering plants is that the reproductive organs of plants are the flower, fruit and seed. Pollination occurs through wind, water, insects and animals. In the structure of the plant there is a female and male prothallus, and double fertilization also occurs.
During germination, the seed is saturated with water and swells, then the reserve substances are broken down and provide energy for germination. From the embryo a sprout emerges, which later becomes a flower, tree or grass.
Gymnosperms
These include not only coniferous, but also deciduous trees. In the deserts of Kenya there grows an amazing plant that has only two large leaves. Its relative is ephedra. It is a gymnosperm plant that has small round berries.
Pollination process
As you know, the reproductive organs of a plant include the flower, fruit and seed. For the fertilization process to occur, pollination is necessary, which helps the emergence of offspring.
In angiosperms, fusion of male and female cells occurs. This is achieved through the cross-transfer process of pollen from one flower to another. In some cases, self-pollination occurs.
Helpers are needed for cross-pollination. First of all, these are insects. They feast on sweet pollen and transfer it from flower to flower on their stigmas and wings. After this, the reproductive organs of plants begin their work. Flowers that are pollinated by insects are painted in bright and rich shades. After coloring, they are attracted by the scent. Insects smell the flower when they are at a sufficiently large distance from it.
Wind-pollinated plants are also equipped with special adaptations. Their anthers are quite loosely located, so the wind carries the pollen. For example, poplar blooms during winds. This makes it possible to spread pollen from one tree to another without obstacles.
There are plants that small birds help in pollination. Their flowers do not have a strong aroma, but are bright red in color. This attracts birds to drink the nectar and pollination occurs at the same time.
Evolution of plants
After the advent of sushi, nature changed. Plants gradually evolved, and ferns were replaced by flowers, shrubs and trees. This happened due to the appearance of the root system, tissues and cells.
Due to the diversity of the reproductive organs of angiosperms, more and more species and subspecies appeared. For reproduction, spores and seeds containing reproductive cells began to appear.
Gradually shoots, leaves and fruits appeared. After reaching land, plants developed in two directions. Some (gametophytic) had two phases of development, others (sporophytic) passed from one cycle to another.
Plants adapted and evolved. Spore species began to reach 40 meters in height. More and more new reproductive organs of plants began to appear. Their evolution depended on the influence of the external environment.
An embryo was formed inside the seed, which germinated after fertilization and atomization. Once in the ground, it fed on useful substances and turned into a sprout.
The evolution of the fertilization process led to the emergence of angiosperms, in which the seeds were protected by the fruit.
The importance of plants for humans
The benefits of the natural world to people are priceless. Plants not only emit gases, salts and water, but also transform inorganic substances into those necessary for life. Gas exchange occurs with the help of the root system, shoots and leaves.
Green plants accumulate valuable organic substances, clean the air from carbon dioxide, while saturating it with oxygen.
Thanks to natural resources, people receive more valuable products necessary for life. Plants become food for animals and humans. They are used to treat various diseases and in the production of cosmetics.
Since the reproductive organ of a plant is the fruit and seed, they have become indispensable in human nutrition. Almost everyone loves berries that grow on bushes. Interestingly, coal and oil also came from vegetation. Peat bogs are the birthplace of algae and ferns.
The vegetative and reproductive organs of flowering plants play an important role in their life. They are responsible for nutrition, development and reproduction. When the life cycle ends, the seeds spread around and new plants sprout.
