Seeds of flowering plants are diverse in shape and sizes: can reach several tens of centimeters (palm trees) and be almost indistinguishable (orchid, infection).
In shape - spherical, elongated ball, cylindrical. Thanks to this form, the minimum contact of the seed surface with environmental. This allows seeds easier to carry adverse conditions.
Semen
Outside the seed is covered with seed peel. The surface of the seed is usually smooth, but it may be rough, with spikes, ribs, hairs, papillats and other growth of seed peel. All these formations - device to the spread of seed.
On the surface of the seeds are noticeable rutters and dust. Rubber - a trace of seeds, with the help of which the seed was attached to the wall of the wound, dusty Saved in the form of a small opening in the seed peel.
Under the leather is the main part of the seed - germ. Many plants in seeds have a specialized flat fabric - endosperm. For those seeds where there is no endosperma, nutrients are postponed in the seeds of the embryo.
Tripping seeds monodo and dichomotor plants Not equally. A typical dual-hearth plant is beans, one-barrel - rye.
The main difference in the structure of seeds of monocoons and dysdootilic plants is the presence of two cotyledons in the bud in two-bedroom and one-in-bedroom plants.
Their functions are different: in the seeds of dwaround seeds contain nutrients, they are thick, fleshy (beans).
The monocycle is the only semi-silder - a shield - a thin plate located between the embryo and endosperm of the seed and tightly adjacent to the endosperma (rye). In the germination of the seed of the cell, the nutrients from the endosperma are absorbed and the germin is supplied. The second seedle is reduced or missing.
Terms of germination of seeds
Seeds of flowering plants can carry adverse conditions for a long time, keeping the embryo. Germinate and give rise to a new plant can seeds with alive embryo, they are called survise. Seeds with the dead germs become nonsense They can not germinate.
For germination of seeds requires a set favorable conditions: The presence of a certain temperature, water, air access.
Temperature. The range of temperature fluctuations in which the seeds can germinate depends on their geographic origin. For "Northerners" need more low temperaturethan for immigrants from southern countries. Thus, wheat seeds germinate at a temperature of from 0 ° to + 1 ° C, and corn - at + 12 ° C. This must be taken into account when setting in sowing.
The second condition for germination of seed is water availability. Again can only be moisturized seeds. The need for water for swelling seeds depends on the composition of nutrients. The greatest amount of water absorbs seeds rich in proteins (peas, beans), the smallest is rich in fats (sunflower).
Water, penetrating through the semi-semi-dust and through the seed peel, displays a seed from the state of rest. It is primarily intensifying breathing and enzymes are activated. Under the influence of enzymes, spare nutrients turn into a movable, easily digestible form. Fats and starch are converted into organic acids and sugars, and proteins in amino acids.
Breathing seeds
For the active breathing of swelling seeds, oxygen is needed. During breathing, heat is highlighted. Freshly seeds breathing more active than dry. If raw seeds are folded with a thick layer, they are quickly warmed up, their embryos die. Therefore, only dry seeds fall asleep for storage and store them in well-ventilated rooms. For sowing should be selected larger and most complete seeds without impurities of seeds of weighing plants.
Cleaning and sorting seeds produced on sorting and grain cleaning machines. Before sowing, the quality of seeds check: germination, vitality, humidity, infection by pests and diseases.
When crops, it is necessary to take into account the depth of seed seed into the soil. Small seeds should be sowned to a depth of 1-2 cm (onions, carrots, dill), large - on 4-5 cm (beans, pumpkin). The depth of seed seal depends on the type of soil. The sandy soil is somewhat deeper, and in clay - smaller. In the presence of a complex of favorable conditions, the seeds are beginning to germinate and give rise to new plants. Young plants that develop from the seed embryo are called seedlings.
In the seeds of any plants, germination begins to lengthen the germinal root and its exit through the dust. At the time of germination, the embryo does heterotrophino, using nutrient reserves prisoners in the seed.
In some plants, at the germination of the seedlies, they are taken over the surface of the soil and become the first assimilative leaves. it overhead Type of germination (pumpkin, maple). Other semi-silders remain underground and are a source of food seedlings (peas). Autotrophic nutrition begins after the appearance of escapes with green leaves above the ground. it underground Type of germination.
Palm tree order (Bincipes)
Palma Family (Palmae, or AreCaceae)
Trees, sometimes lianas with unreasonable trunks, without secondary thickening and the crown of finger-or cross-disseated leaves. Flowers small, Obroat, Right, simple or complex, often very large inflorescences, Sitting or, often immersed in fleshy axes. The perianth is simple, 3-membered, in 2 circles, sometimes spiral, separately or somewhat aggregate. Stamens 6 in 2 circles, often 9 or more. Stagging threads are free or at the base struck in the ring or tube. Owner's ovary, 1-3-nest with 1 anatrical seed with 2 integments. Column. Placentating Central Corner. Fruit - berry or kitty. Seeds are large, with endosperm, often closely threw out with endocarp.
235 clans and about 3,400 species in the tropics and subtropics, especially Asia and America.
The endowment of the tropics is rightly associated with palm trees. They are often determined by tropical landscapes. They even say about the "palm belt", having in mind the coconut cultivation zone, between 20 ° latitude north and south of the equator. These latitudes approximately accumulate tropics from subtropics. Especially rich in palm trees on alluvial soils of large rivers such as Amazon and Orinoco. But a lot of palm trees in savannah, and in mountain subtropical forests, where they can reach the borders of frosts. The only European look hammerops low (Chamaerops Humilis), in the south of Spain and Italy, withstand even the temperature in -7 ° C. The geographical distribution of palm trees is generally wonderful. In America, 92 kind and 1140 species are known. In the Australian-Asian space of species only a few more - 1150, but clans 167, which is explained by the high number of births endemic for individual islands. But Africa has only 50 species of 15 types.
For many, palm trees are characterized by high column-like trunks with a height of 20-30 m, but possessing throughout the same thickness, and sometimes the trunk at the top is even thicker than at the base due to the remaining leaf stuffs. The secondary thickening of the palm trees, as practically all single-bedroom, is absent, but the primary thickening flows very intense. Below the point of growth is formed a large number of Quickly dividing cells and is laid quite a lot of incorrectly arranged vascular beams with powerful sclerorenchive plates. As palm trees grow, the primary thickening can progress, and then fluff out again. This leads to some species to the fracture of the trunk in the middle part (reminiscent of the fishing that swallowed large prey).
Palm trunks are not branched, with the exception of the kind hiphen (Hyphaene), which assumes this dichotomic branching. Along with high-vehicle species, there are many short-barreled and almost basic species whose leaves socket leaves as it were from under the ground. Very peculiar climbing so-called "rathang" palm trees kalamus (Calamus), inhabitants in the tropics of the old world. Rotans have relatively thin flexible trunks are seated with strong bent spines. Curly leaves in a clearly regular location (not typical of palm trees!), Have several pairs of lateral segments, as well as densely dodied Rakhis spiny, which is presented top part Sheet. The length of the Rotang trunks reaches 100-200 m.
Leaves palm trees of two main types. The initial is the peristicular type (Fig. 204). Calm-disseated palm leaves reach maximum for leaves of size 10 m or more, but conventional dimensions - 3-5 m. The leaf popping with noise of such palm can seriously embed. The finger-disseated sheet in the phylogenetic attitude was seconded and arose as a result of the growth of Rakhis growth. The segments of the palphet sheet to a greater or lesser extent resulting at the base. The trunks of many palm trees (and more often the cutters of the leaves) are the strongly connected.
Interesting the problem of herbarization of palm trees. Of course, you can collect flowers for herbarium, often fruits or pieces of inflorescence. And what about the leaves, inflore the whole form or with a barrel? Here, the Herbarium is largely replaced by sketching, accompanied by the necessary quantitative measurements, such as the width of the cutter, the number of segments, etc.
The inflorescences of many species are often intensively branched and achieve significant sizes, sometimes up to 1.5 m or more. Thes of them are often thickened and brightly painted. Surprisingly, always small flowers Palms form
Fig. 204. Palms. Cocos (Cocos Nucifera): 1 - general form; 2 - inflorescence with male (a) and female (b) flowers; 3 - Male flower (ChL - CHELSELISTICS); 4 - Fruit (coconut) in the context. Calipotrocalix (Calyptrocalyx Spicatus): 5 - the upper part of the plant with fruits. Sabal (Sabal Mauritiiformis): 6 - general view with inflorescences. Bactris (BACTRIS GUINEENSIS): 7 - part of the plant with fruits. Seychelles Palma (Lodoicea Maldivica): 8 - part female plant with fruits; 9 - Two-hand endocrium with seed. Calamus (Calamus Longiseetus): 10 - transverse section of the wound
sometimes such large fruits like coconut (Cocos Nucifera) or seychelles Palma (Lodoicea Maldivica). The latter fruits are the largest among wood plants, and the seeds are generally the largest. So in these relations, palm trees act as record holders.
The value of palm trees in the life of the population of tropical countries is difficult to overestimate. Folded-disseated leaves of many species - the usual material that goes on the roofs of the so-called palm huts. From stems sagovy Palma (MetroxyLon) mining starch contained in parenchymal cells and going for the manufacture of this Sago. One of the most important world-scale oilseeds is undoubtedly oil palm (Elaeis Guineensis). Fats in exceptionally high concentrations are postponed by this palm tree not in endosperm, but in pericarpium, so that they cannot be used by a seedlings, but undoubtedly attract animals that spread fruits. This perched palm of African origin is cultivated in many areas of the tropics. In biologically, it is interesting in that it has separate inflorescences that dissolve undisaded. In men's inflorescences, there are up to 140,000 flowers, in women - no more than 5,000. There are also purely doubtful varieties.
Peristological species include, perhaps, the most famous among palm trees. coconut palm, or coconut, especially abundant in coastal areas. The landscape of the coastal regions of India, South Vietnam, Cuba, Ceylon is largely determined by coconut palm. It is assumed that the birthplace of the plant is the islands of Polynesia, from where it applied not only by means of man, but also by transferring fruits on water. The average pericarpium layer is represented by an air layer. Seeds are capable of germination through 3 and even 4 months of swimming. The fruit of coconut is not quite common. Inside the powerful, 3-layer pericarpium is a "shell" from an endosperm with a thickness of 1 cm, to which a tiny embryo is adjacent. The middle of the fetus is filled with protein-rich muddy liquid - "coconut milk" (the taste of it, however, with milk does not have anything in common). With full maturation of "nuts", 9-11 months after flowering, liquid solidifies. One inflorescence brings 8-10 "nuts", and the tree gives a harvest for at least 25-30 years. Endosperm coconut (the so-called copra) is a valuable product that is coming for the manufacture of coconut oil, as well as confectionery. The processing of coconut "nuts" is poorly amenable to mechanistence and is still manually, a qualified worker reveals on the day of 2000 "nuts".
In a huge family of palm trees, only a few species form like coconut edible fruits. Dates are also among the latter - fruits palm tree (Phoenix Dactylifera). The origin of it is unclear, but there is no doubt that it refers to the number of oldest cultural plants. For the appearance, the palm palm like a little bit like coconut, but the last trunk is smooth, and at the palm tree, he is thickly covered with remnants of the pets of dead leaves. Coconut palm tree divorces in the conditions of a wet seaside climate, the palm palm, on the contrary, can grow in dry places, up to the oasis of the desert. Her root system It can achieve deep groundwater. Date palm bounceman. On plantations are located predominantly female trees, and inflorescences from men's palm trees that serve the subject of trade are tied in crowns of women's individuals. Fruits - dates - single-bedned berries with juicy sugar mesocarpium.
Special use has palm trees ageki. (ARECA CATECHU). They are sold on any market of South Asia in abundance and go to prepare
a narcotic chewing makeup - Bethel, which also includes the leaves of one type of black pepper and lime. The arcaeloids contained in the fruits strongly excite the central nervous system And brand the activity of the heart.
We see in such a way that the palm trees find the most various applications. Let's give some more examples. From young inflorescence wine Palma (Raphia Vinifera) Get Sweet Juice, which is on the manufacture of palm wine. By the way, the leaves from one of the species of this kind reach 15 and even 20 m lengths, from the petioles of the leaves of many species of palm trees, fiber mines for the manufacture of ropes, networks, etc.
Palms are solely decorative. They decorate the boulevards and embankments of cities, up to the coasts of the Mediterranean and Black Seas (however, only the most cold-resistant species can grow here. Some species of palm trees can be seen on national coat of arms and flags. Royal Palma (Roystonea Regia), adorning the Central Square of Havana, - National Cuba Tree, and the highest of palm trees - cercastic Andjian (Ceroxylon Andicola), reaching 60 meters of height, is the national emblem of Columbia.
Palms - undoubtedly, an ancient family, which confirms the paleobotanic. Most scientists believe that palm trees have general origin With Lilyna. However, except for some general signs, characteristic of single-bedroom, palm trees, at least with modern Lily, have little in common. Important features Palm, like the next family, is a tendency to aggregation of flowers in complex inflorescences and complete absence boxes. In any case, the position of palm trees in the system is quite separate.
A lot of different concepts are being studied in the course of nerds. One of them is endosperm. What is it, what functions in the plant performs this structure? These and other questions you will find the answer in this article.
Endosperm is part of the embryo
People have long surprised the ability of a tiny seed to give rise to an entire body. It turns out that this is due to its unique consist of germinal root, stalk, kidney and leaflet. These embryonic structures are surrounded by a nutrient connective tissue. It is an endosperm. Outside seed has additional defense - peel.
This term comes from two Greek words "Endo" - inside, "sperm" - seed. In fact, the substances necessary for the development of the nucleus tissue.
Nutrient value
Endosperm is a fabric that is formed in the fertilization process. By chemical composition, it is a combination of carbohydrate starch, proteins and vegetable oils. Therefore, a person uses seeds as an energy source and vitamins. But beneficial features They remain only in raw form. In terms of heat treatment, the macromolecules of organic substances occurs.
Endosperm vote
Nutrient fabric of plants can be primary and secondary. The voted endosperm is formed before the process of merging Games - fertilization. It develops from megapor, which is a motherboard with a haploid set of chromosomes. Primary endosperm is a cloth formed in a seed. As a result of its development, the formation of a female inlet, or Gametophyte.
Double fertilization of plants
In seeds, coated with endosperm is formed during fertilization. During this process, two sperms are involved, which are in the anthers of the stamens. The marking of the pestle contains one female game and a central germinal cell. Fertilization occurs here. One sperm merges with an egg, forming a seed embryo. The other is connected to the germinal cell. The result of the last process is endosperm. This type of formation is called secondary. Endosperm is located around the embryo, warming and eating it, creating conditions for germination of the seed.
How is it formed?
Endosperm is formed in two ways. In the first case fertilized kernel germ sack It shares many times. The resulting structures are located along its walls. This type of endosperm formation is called nuclear. In this case, the feed fabric seeds is liquid. For example, coconut milk.
But most coated after nuclear division occurs cellular. It changes the aggregate condition of the nutrient tissue. At the same time, cells are formed during each division. So, if collecting fruits of corn during the nuclear fission period, it will be juicy and sweet. Then the transformation of simple carbohydrates in polysaccharides. This chemical transformation accompanies cell division.
So, endosperm, which is the nutrient of the seed embryo, performs essential functions. These include the provision of embryos of energy, vitamins and microelements, transportation of solutions of mineral substances from an adult plant. The regulation of the process of differentiation of cells of the embryo in organs, which occurs due to cytokinins of the endosperma.
59 ..8. Seed, fruit, hoping
SEED. If the lowest and many higher plants multiply disputes that do not have multicellular covers, then seed plants multiply seeds.
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Only harsh algae, the developing zygota (dispute) is surrounded by several spiral-surrounding vegetative coat cells of Archegononia. In this state, this plant is experiencing a rest period and can effectively settle.
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Seed - body of sexual reproduction and resettlement of seed plants, usually developing from a fertilized sector.
The voted seeds are developing directly on the surface of the macrosphell (on seed scales), and the coated seeds are enclosed in the fetal cavity. Unlike disputes - units of settlement of dispute plants - the seed has a number of features resulting from progressive evolution. First of all, the seed is a multicellular structure that combines sparecloth tissue, a similar subsidiary (germin) and a special protective cover. This seed is significantly different from the dispute, where everything necessary for the development of the future Gametophyt plant is contained in the only cell.
In their physiology, the dispute and seed also differ significantly. The dispute germinates immediately upon admission to moisture into the cell. Many seeds have a different duration of a period of physiological peace, during which they are not capable of active livelihoods and formation of a seedling. In other words, seeds as units of plant settlement in all respects are significantly more reliable and universal than disputes.
Fig. 105 Seeds with endosperm surrounding the embryo - A (Mac-Papaver Somniferum); with endosperm adjacent to the germin, - b (wheat-trifficum aestivum); with spare stuff stuffed in semi-units, in (peas - Pisum Sativum); with endosperm surrounding the embryo, and a powerful perisperm - g (pepper - Piper Nigrum); With Perisperm: - D (Kupz - Agro-Stemma Gjfhago):
1 - seed peel, 2 - endosperm. Parts of the embryo: 3 - spine, 4 - stalks, 5-kids, 6 - semi-silders, 7 - okolothennik, 8-perisisterm
The development of seed begins with the fact that the zygota, located in the seed, is drawn up in length and shares across the partition. One of. The cells forms the so-called suspension, or suspensor, the other -_ proper germin. The suspension contributes to the nutrition of the embryo, immersing it in the endosperm, and often acquires the properties of the Gaustoria - suction cups. The second cell is repeatedly mothotically divided and ultimately forms the embryo.
In the voted endosper, the haploid and formed by the fabrics of the female Gametophyte. The coated margin on the endosperm gives a triploid core, resulting from the merger of the diploid secondary nucleus of the germ bag and one of the sperm. The division of this nucleus gives the whole mass of nutrient tissue - endosperma. The degree of endosperma development from different taxas is not the same. As a rule, than more primitive in evolutionaries, the systematic group, the better its endosperm is developed. The endosperma reduction is usually associated with an increase in the relative size of the embryo. With an increase in its size, spare substances usually accumulate in the germ itself (Fig. 105).
In the process of developing a female gamethophyt, and then the embryo and endosperm of megasoprangiy, that is, nicknoles of the nephery, usually destroyed, and its spare substances are used. However, in some taxa, this tissue is partially preserved, turning into a nutrient tissue, a physiologically similar endosperm. It is called Perisperm and marked for seeds of representatives of the family of peppers, cloves and a number of others.
The main structural parts of a mature seed: seed peel, nutritious (stocking) cloth and germ.
Testa. Seed peel, or spermodema, is formed mainly due to the integrations of the family, less often - due to the growth of the tissue of the Halaza. Most plants have seed peel closely surrounds the seed and serves as the main protective cover that prevents its drainage and premature saturation of moisture. The structural features of the seminal peel are associated with the ways of distribution and germination of seeds. They have great importance For systematics. Seeds developing in open fruits, in family peel is often formed protective layer from sclerized cells. Sometimes the outer layer of the peel becomes fleshy and juicy (sarcotest), which attracts birds and mammals and contributes to the spread of seeds.
Fig. 106 Phaseolus vulgarfs beans seed (A - general view, b - germ): 1 - Trail Chalaza, 2 - Trail micropilene, 3-rings, 4 - seed seam, 5 - seed skin (sperm), 6 - HUMEN, 7 - seed
On the surface of the seed, the rubber is usually well noticeable - a trail remaining at the site of attaching a seed to the funicular (Fig. 106). Morphological features of the Rubber - Form, Dimensions, Color, etc. - are of great importance in plant systematics, as well
Widely used in seeds when characterizing and determining seeds.
The channel, or a deepening in the seed peel, which is the residue of the micropower of the nephery, is called a micropilar trail, the balance of the chalaza is the opposite end of the seed is called a chalazal one. Through the microplar trail during the germination of the seed comes out the root. In addition to the scooter, microfilar and colazal traces on the seed peel, you can usually notice a special thickening, called the edge of the seed or its seam. The seam occurs in that part of the funicular, which in some types of geeks merges with the icon.
Many seeds of flowering plants are characterized by a special education, having a type of fleshy growth, films or fringe. It develops in various parts of the seed and received the name of the award or arylla. The nature of the designer is different. Sometimes it arises as a result of the growth of the tissues of the funicular, the seed is in effect partially or completely, tightly adjacent to seed peel, but does not grow up with her. In other cases, Arylwus is a derivative of the outdoor integment of the seed. The desperators located near the micropalized seed trace are known as the Karunkula. Sentians for the most part Brightly painted and contain sugars, fats and proteins. These appendages often attract certain animals, usually birds or ants that contribute to the spread of seeds and plant resettlement.
Nutritional fabrics. A nutrient cloth in the seeds can be endosperm and perisperm. More often in the seeds occurs endosperm, less often perisperm, even less often - both nutrient tissues at the same time. In some taxa, special nutrient tissues are completely absent and then spare substances are postponed directly in the embryo.
The consistency of the nutrient tissue is different: solid, liquid, mucous, etc. Solid, but equipped with deep folds and furrows endosperm is called a man. Most often, carbohydrates are accumulated in nutrient tissue in the form of grains of secondary starch, less often lipids in the form of droplets of oily oil. In addition, seeds always have spare proteins, which is especially important in germination, and phosphoric phytin compound, which is attributed to the role of the stimulator in metabolic processes committed during germination.
Depending on the chemical composition The prevailing spare substances seeds are divided into starchy (wheat, corn, rice and many other cereals), oilseeds (sunflower, flax, peanuts, soy) and protein (most legumes).
Germ. The embryo is usually formed from a fertilized egg and is a succession of a new individual. The embryo is a miniature sporophyte. The process of forming the embryo (embryogenesis) is complicated and divided into several periods. This process has its own characteristics. Seeds of most plants enter into one embryo. It is most often blunt, less often painted and then contains chlorophyll. The degree of morphological dismemberment of the embryo is different in different systematic groups. The embryo is largely made of meristematic cells. For the most primitive taxa, the so-called underdeveloped germ is characteristic. It is very small, point and formed late, for the period of seed germination. In evolutionarily more advanced groups, the germ is well developed, nutrients can be laid in its parts, and special nutrient tissues (endosperm and perisperm) are reduced or completely disappeared. In most flowering plants, the axis of the embryo consists of embryonic root and stem. Semidols are attached to the top of the stalk. Part of the stem, located below the cotyledon, is called a hypocotyl, above the epicotyl (see Fig. 51). The top of the stalk ends with a kidney, or a meadow, the desire of the main escape of the plant. In the seed root always sent to the trail of the micropile. It forms the main root of a new plant. Part of seeds hypocotyl and epicotyl during germination are able to lengthen and endure seedlies to the surface. The number of cotyledons is different. In bicycle collections, there are usually two, very rarely three or four, only one in one-bedroom, among them is most often somewhat (from 2 to 15). Sejdoli - the first leaves of the plant, developing in the seed, not yet differentiated nucleus. It is believed that single-sided-germs originated from the two evolution in the process of evolution. With the above-ground germination of the semi-silders, they are green and capable of photosynthesis, and under the underground serve mainly by the storage of nutrients, for example, with sucks or oak. In other cases, Semi-aidoli (in cereals) perform the role of the Gaustoria, absorbing the endosperm nutrients and transmitting them to the above-ground part of the seedlings.
Physiology of seed and its germination. Seed growth usually ends shortly before the completion of its full physiological development. A slightly later ending the influx of nutrients and the activity of plant hormones is reduced. As the activity of hormones and enzymes decreases to a minimum, the humidity of the seed falls. Seed covers undergo significant changes: their fabrics are partially die off, compacted and often decorate. Such mature seeds are capable of carrying adverse environmental conditions and can continue (sometimes up to several tens of years) to maintain the ability to germinate. Such mature seeds are in physiological peace, in this state there are metabolic processes, breathing, sometimes "ripening" the embryo, but the ability to swell during the arrival of moisture and germination often inhibit.
The degree of depth of physiological peace and its duration of unequal. Seeds are outlined from the state of rest in various ways. Some seeds, especially annual plants, it is easy to swell and germinate under the influence of moisturizing. Cold stratification is required to germinate other and normal development, that is, long-term maintenance of them under reduced temperature, in a humid environment and in good aeration. Finally, there is another group of so-called "solid vehicles", seed peel which is due to her structural features Waterproof. Such seeds germinate only after scarification - an artificial disruption of the integrity of the peel with the help of tadacrapazias, sanding, overwhelming boiling water, etc. In nature, such seeds swell and germinate usually under the influence of a sharp shift temperature modescontributing to the disruption of the integrity of the shell.
Seed germination is called their transition from the state of peace to the vegetative growth of the embryo and the formation of a seedling out of it. Germination begins with optimal for each type of combination of humidity and medium temperature, with free oxygen access.
Seed germination is accompanied by complex biochemical and morphophysiological processes. When water intakes in the seeds, the respiratory process is sharply enhanced, enzymes are activated, the spare substances are activated in an easily dismantled, movable shape, polyribosomes are formed and the synthesis of protein and other substances begins. The growth of the embryo usually begins with a breakthrough of covers with extension germinal root and hypocotyl in the microfilarist area. After the appearance of the root of the kidney develops into escape, on which the real leaves are deployed (see Fig. 51). In the practice of agriculture, the viability and quality of seeds are characterized by an eyeling, that is, the percentage of seeds that gave normal seedlings in the optimal conditions for them for a certain period. For field crops, this period is 6-10 days, for woody - up to 2 months.
Seed - plant reproduction body, developing after fertilization from a nephery.
In the formation of seed and fetus, one of the sperm merges with an egg, forming diploid zygot (fertilized egg). In the future, the zygotes is expanding repeatedly, and as a result, a multicellular embryo plant is developing. The central cell, which fastened with the second sperm, is also repeatedly divided, but the second embryo does not occur. A special fabric is formed - endosperm. Endosperm cells accumulate nutrient reserves required for the development of the embryo. Child covers grow and turn into seed peel.
Thus, as a result double fertilization A seed is formed, which consists of an embryo, sparkling fabric (endosperma) and seed peel. The wall of the fetus is formed from the wall of the waters, called the ocoplodnik.
Types of seeds
1. With endosperm (the seed consists of three parts: seed peel, endosperm and embryo. Seed with endosperm is inherent in single-grade, but can occur in dicotyledtic - poppy, grated, umbrella);
2. With endosperm and perisperm (usually a rare type of structure, when the seed is germin, endosperm and perisperm. It is characteristic of the lotus, nutmeg);
3. With perisperm (endosperm is fully spent on the formation of the embryo. Seeds of this type are characteristic of cloves);
- without endosperma and perisperma (the embryo occupies the entire cavity of the germ bag, and the spare nutrients accumulate in the semi-units of the embryo. Together, the seed consists of two parts: seed peel and the embryo. Such a structure is peculiar to bean, pumpkin, rose, nut, bukov, etc.)
Perisperm - stocking diploid cloth of the seed in which nutrients are laid. Arises from the nomalus.
Endosperm - Large-milking Flashing fabric, main power supply for developing embryo. At first, he actively conveys the germ of the substance coming from the parent organism, and then serves as a tank for laying nutrients.
Fig. Seeds
16. Classification of fruits. SPLATE .
The fruit of the reproduction of the coated bridges, which is formed from one flower and employee for the formation, protection and distribution of seeds in it. Many fruits-valuable food, raw materials for drugs, coloring substances, etc.
Classification of fruits
In most classifications, fruits are usually divided into real(Forming from the outstanding promise) and false(Other organs participate in their education).
Real fruits are divided into simple (formed from one pistil) and sophisticated (arising from the polynomial of the apocarpical guinesey).
Simple divide on the consistency of the octopulodnik on dry and juicy.
Among dry distinguishes single-seat (for example, a grain, walnut) and multispical. Multivine fruits are divided into open (bob, box, bag, pod, etc.) and unbroken. Invisible dry multifreemary fruits are divided into segic (segmenty bob, segmental pod) and fractional (tubing, double-straw, etc.)
Among juicy fruits Also highlight multi-semen (tsykina, Apple, Berry) and single-stage (Kostyanka).
Complicated are called, based on the names of simple fruits (multicast, multi-perts, etc.).
In contrast to the fetus (simple or complex), the nozzle is formed not from a single flower, but from a whole inflorescence or its parts. In any case, the axis of inflorescences participate in the formation of the hodge. The nozzle is a product of modification (after fertilization) not only flowers, but also the axes of the inflorescence. In typical cases, the nozzle imitates the fruit and matches it functionally. Classic example - pineapple hoping.
17, vegetative reproduction of plants and its biological Value of vegetative reproduction of plants(from lat. vegetativas. - Vegetable) is the reproduction of plants with the help of vegetative organs (root, stem, sheet) or their parts. Vegetative plant reproduction is based on regeneration phenomenon. During such a method of reproduction, all properties and hereditary qualities in subsidiaries are fully saved.
Distinguish natural and artificial vegetative reproduction. The excellent reproduction occurs constantly in nature through the impossibility of or difficult seed breeding. It is based on the separation from the parent plant of viable vegetative organs or parts capable of regeneration to restore a whole plant from its part. The whole combination of the individuals thus obtained is called clone. Clone(from Greek. CLON - sprout, branch) - population of cells or individuals, which is formed as a result of the forgeless division from one cell or individual. Vegetative reproduction of plants in nature carried out by:
Separation (single-cell);
Root sprouts (cherry, apple tree, raspberries, blackberry, rosehip);
Korebolbami (orchid, dahlia);
Messengers (currants, gooseberry);
Mustache (strawberries, sludge creeping);
Owls (drink, reed);
Tubers (potatoes);
Bulbs (tulip, onions, garlic);
Brood kidneys on the leaves (broofіlyum).
Biological significance Vegetative reproduction:a) one of the devices for the formation of descendants where there is no favorable conditions for sexual reproduction; b) the descendants are repeated by the genotype of the parent form, which is important to maintain signs of the variety; c) one of the ways to maintain valuable varieties and properties; d) with vegetative reproduction, the plant can be kept under the conditions of impossibility of seed reproduction; e) a preferred method of reproduction of decorative plants; e) When vaccinated - in the submitted plant, resistance to external conditions increases. The following are the shortcomings of vegetative reproduction: a) negative features b) are transmitted to the diseases of the parent organism.
18. Casual reproduction, its role and form Reproduction is a universal property of all living organisms, the ability to reproduce themselves like. With it, it is saved in time of species and life in general. The life of the cells, much shorter than the life of the body itself, so its existence is supported only by the reproduction of cells. There are two methods of reproduction - cull and sex. With a bunch of reproduction, the main cellular mechanism ensuring an increase in the number of cells is mitosis. The parent is one part. The offspring is an accurate genetic copy of the parent material. 1) the biological role of the powerful reproduction maintenance of adaptability enhances the value of the stabilizing natural selection; Provides rapid pace of reproduction; Used in practical selection. 2) Forms of non-cellular reproduction in single-celled organisms allocate the following forms of cull breeding: division, endogonium, sisogonia and binding, spore formation. The division is characteristic of amoeba, infusoria, flagella. First, the mitotic division of the nucleus occurs, then the cytoplasm is divided into half an increasingly deepening hauling. In this case, the daughter cells receive about the same amount of cytoplasm and organoids. Endogonia (internal kinding) is characteristic of toxoplasm. In the formation of two subsidiaries, the maternal gives only two descendants. But there may be an internal multiple binding, which will lead to sizogonia. It is found in disputes (malaria plasmodium) and others. There is a multiple division of the kernel without cytokinesis. From one cell a lot of subsidiaries are formed. Burning (in bacteria, yeast mushrooms, etc.). At the same time, a small tubercle containing a subsidiary (nucleoid) is originally formed on the maternal cell. The kidney grows, reaches the size of the maternal individual, and then separated from it. Spore formation (at the highest spore plants: mosses, ferns, plane, horsages, algae). A child organism develops from specialized cells - disputes containing a haploid set of chromosomes. 3) The vegetative form of reproduction is characteristic of multicellular organisms. At the same time, the new organism is formed from a group of cells separated from the parent organism. Plants are breeding with tubers, rhizomes, bulbs, cornklubs, rootpods, root pigs, tanks, cuttings, broken kidneys, leaves. In animals, vegetative reproduction occurs in the lowest organized forms. The cilia worms are divided into two parts, and in each of them the missing authorities are restored by disordered cell division. Killed worms can restore a whole body from one piece. This type of division underlies the regeneration - restoration of lost tissues and parts of the body (in ring worms, lizards, salamander)
19 sexual reproduction - associated with the merger of specialized genital cells - Games with the formation of zygota. Gamets may be the same and different in morphological terms. Isogimy - merging the same heams; heterogamia - the merger of different Games; Oogamia is the fusion of a movable sperm with a large stationary egg.
For some plants groups, the alternation of generations is characterized, in which the sexual generation produces sex cells (Gametophyte), and the contradianship (sporophyte) is disputes.
Fertilization - this is an association of nuclei of male and female genital cells - Games, leading to the formation of the zygota and the subsequent development of the new (subsidiary) organism.
Gamete - This is a reproductive cell having a single (or haploid) a set of chromosomes involved in sexual reproduction. That is, in other words, the egg cell and spermatozoa are gates with a set of chromosomes of 23 each.
Zygote - This is the result of the fusion of two heams. That is, the zygota is formed as a result of the merger of the female egg and a male spermatozoa. In consequence, it develops into a person (in our case, in a person) with the hereditary signs of both human organisms.
Isogami
If the merging machines morphologically do not differ from each other, the magnitude, structure and chromosomal set, they are called izoatami, or cullless gates. Such gametes are mobile, can carry flavors or be amosides. Isimy is typical for many algae.