Today we will look at the simplest and most ancient method of home preparation...
Landscape design and planning
Questions for the colloquium on the topic
for 2nd year biology students
What is an ovule? List its components in Gymnosperms. Ovule ovule(lat. ovulum) - the formation in seed plants from which (usually after fertilization) the seed develops. It is the female sporangium (megasporangium) of seed plants. In gymnosperms - on the surface of the seed scales in female cones, located openly in the axil of the megasporophyll. In the central part of the ovule (nucellus), four megaspores are formed as a result of meiosis of the spore mother cell, then three of them die, and a female gametophyte is formed from one megaspore. In gymnosperms, it is sometimes called endosperm because it stores nutrients in the mature seed.
S. consists of a nucellus (central part containing a megasporocyte), one or two integuments (integuments) and an achene (funicular). At the top of the S. the integument usually does not close, leaving a narrow opening - the micropyle.
What is nucellus? How does the formation and development of the ovule occur?
Nutsellus(from Latin nucella - nut), the central part (core) of the ovule of seed plants; homologous megasporangia ferns. Includes nutritional tissue and a membrane-covered embryo sac with a small opening called
micropylem.
Theories of the origin of the ovule integument.
Telomnaya
The integument is the result of the fusion of peripheral initially vegetative bodies around one spore-bearing body. This theory is consistent with paleobotanical findings that relate to proto-gymnosperms and the extinct gymnosperms - seed ferns.
Synangial
According to this hypothesis, first put forward by the English paleobotanist Margarita Benson (1908), the integument is a ring of sterilized, fused and fused sporangia surrounding the central functioning megasporangium, and the micropyle corresponds to the original gap between the tips of the sporangia. In other words, the ovule is actually a synangium in which all sporangia except one have been sterilized and formed the integument of a single, fertile sporangium. A good confirmation of the “synangial” hypothesis is the primitive ovules of seed ferns, which often retain very clear traces of their synangial origin. The ovules of a number of seed ferns had segmented integuments with a vascular bundle in each segment (chamber).
Micropylar and chalazal poles of the ovule
The two poles of the embryo correspond to the root and shoot poles.
In the embryo: hypocotyl and cotyledons
Features of the ovule as a modified megasporangium of seed plants in comparison with the megasporangium of higher spore plants.
Seed is a new type of diaspore.
Megasporogenesis process
There are 2 ovules on the scales of female cones. The ovule consists of a nucellus (nucleus) and integument (cover). A small hole remains at the top - the micropyle (pollen passage). In late spring, the scales of the female cone open and pollen falls through the micropyle inside onto the nucellus. After this, the seed scales are compressed, forming protection for the ovules. During pollination, there are still no male gametes in the dust grain, and the prothallus with archegonia is not yet developed in the ovule. A month after pollination, one of the nucellus cells begins to divide by meiosis. As a result, 4 haploid (n) cells are formed - megaspores. 3 die, and 1 turns into a shoot (n). The female gametophyte is a colorless multicellular thallus. ^ There are many storage substances in the tissue. 14-15 months after pollination, two archegonia are formed on the gametophyte. The archegonium consists of a large egg cell with a large nucleus, above which lies an early disappearing ventral tubule cell, and a neck of eight small cells. At this time, the pollen tube grows very slowly inside the nucellus. After the pollen tube with two sperm reaches the archegonium, one of the sperm fuses with the egg and the other dies. An embryo develops from a zygote. The ovule turns into a seed. The vegetative body of the female gametophyte becomes the primary endosperm (n). A filmy peel is formed from the nuceus, and a woody peel is formed from the integument. Thus, parts of 3 generations can be distinguished in the seed:
Woody and filmy peel – old sporophyte (2n)
Endosperm – gametophyte (n)
Embryo – new sporophyte (2n)
Typical development of the female gametophyte of Gymnosperms
What structures are homologous to the anthers and pollen grains of Gymnosperms?
Anther - microsporangium, dust grain - pollen grain
10. 2 variants of the structure of a mature male gametophyte, its cellular elements
11. The further fate of the male gametophyte of Gymnosperms.
12. Does a pollen grain always leave the anther mature? Which option is more progressive?
13. Pollination (definition)
In plants, pollen is transferred from the anthers to the stigma (in flowering plants) or to the ovule (in gymnosperms). After O., a pollen tube develops from a speck of dust, the edge grows towards the ovary and is delivered by the husband. sex cells - sperm - to the egg located in the ovule, where fertilization and development of the embryo occurs.
14. Fertilization of the cycad type, its features
After pollination, the ovules begin to enlarge and soon reach the size of a seed, although fertilization has not yet occurred in them. This period, from pollination to fertilization, is very long and usually takes six months (for example, in the cycad, pollination occurs in December - January, and fertilization in May - June).
Microspores that enter the pollen chamber with a drop of pollinating fluid germinate. At the same time, the exine bursts, and the haustorium cell grows through the gap, stretching the intine (Fig. 168, 13). It penetrates the wall of the pollen chamber and sucks nutrients from the nucellus tissue (Fig. 168, 13). At this time, the generative cell divides into two, and one of the resulting cells - spermatogenic - begins to grow rapidly. In it, male gametes - spermatozoa - are formed, not immediately, but after several months (Fig. 168, 15).
By the time of fertilization, the expanded spermatogenic cell is in close proximity to the entrance to the archegonia. The sperm released from it only have to “swim” in the liquid that was poured out with them from the spermatogenic cell, only a short distance to the archegonium, in which the contents of the sperm merge with the egg (Fig. 168, 17).
Thus, in cycads, two mechanisms are combined in a single process, one of which - the formation of a motile sperm - is characteristic of distant ancestors fertilized with the help of water, and the second - the formation of a pollen tube (an expanding spermatogenic cell) - is typical of all others standing higher on the “evolutionary ladder” » seed plants.
15. Siphonogamy
(pine type fertilization) – fertilization using a pollen tube; the sexual process takes place inside the ovules and does not depend on the presence of moisture. The function of delivering male gametes is carried out by special cells.
16. How are these fertilization options fundamentally different in Gymnosperms?
17. What cells (or their features) in the first and second cases can be called atavistic?
The seed develops on the surface of the seed scale. It is a multicellular structure that combines storage tissue - endosperm, embryo and special protective cover (seed coat). Before fertilization, the central part of the ovule contains a nucellus, which is gradually replaced by the endosperm. The endosperm is haploid and is formed from the tissues of the female gametophyte.
U cycads And ginkgo outer layer of the seed coat ( sarcotesta) soft and fleshy, middle layer ( sclerotest) is hard, and the inner layer (endotesta) is filmy at the time the seed ripens. The seeds are dispersed by various animals, which eat the sarcotesta without damaging the sclerotesta.
U yew And podocarpus the seeds are surrounded by fleshy arillus- highly modified scales of a female cone. The succulent and brightly colored aryllus attracts birds, which spread the seeds of these conifers. Arilluses of many species of podocarpus are also edible for humans.
19. From what structures of the ovule do the corresponding parts of the seed develop?
20. The structures of which stages of the life cycle does a seed include?
22. Compare the structure of ginkgo and pine seeds. What are the signs of the primitiveness of the first?
The developed pendulum characteristic of pines degenerates by the time the embryo is fully developed. A pine seed consists of an embryo, a seed coat and a megagametophyte, which is a reserve of nutrients.
In cycads and ginkgo, the outer layer of the seed coat (sarcotesta) is soft and fleshy, the middle layer (sclerotesta) is hard, and the inner layer (endotesta) is filmy at the time the seed ripens.
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platyspermic ginkgo ovules |
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Additional structures are grouped under the term angiospermization |
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The pollen chamber is unitegmal |
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Fertilization after abscission |
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23. What is the primary endosperm of a seed? What does its name come from?
The primary endosperm of gymnosperms is formed BEFORE FERTILIZATION from a megaspore and corresponds to the female gametophyte. The endosperm cells of gymnosperms are initially haploid, then, as a result of nuclear fusion, they become polyploid.
Secondary endosperm- tissue formed in the seeds of most flowering plants DURING FERTILIZATION.
24. Evolutionary advantages of seed propagation.
Seeds are more viable, thanks to animals, wind, and water they can be transported over long distances. There is a supply of nutrients, the embryo is protected by the seed coats. Reproduction is not associated with water.
ovule
(ovule), a multicellular formation in the ovary of seed plants, from which the seed develops after fertilization. Usually consists of outer and inner integuments (instruments). They do not close, leaving a narrow opening - the pollen duct (micropyle). The integument covers a multicellular closed layer - the nucellus, which encloses the embryo sac. It, in turn, consists of an egg apparatus - three cells concentrated at the end closest to the pollen tube. One of them, with a larger nucleus, is the egg (female gamete), the other two are auxiliary cells, or sinerigudes. At the end opposite the pollen tube, 3 antipodal cells develop. In the middle of the embryo sac there is a central cell. The egg cell and the central cell are involved in fertilization.
Encyclopedia Biology. 2012
See also interpretations, synonyms, meanings of the word and what OVILE is in Russian in dictionaries, encyclopedias and reference books:
- ovule
the same as... - ovule in the Big Russian Encyclopedic Dictionary:
ovule, same as ovule... - ovule in the dictionary of Synonyms of the Russian language.
- ovule in Lopatin’s Dictionary of the Russian Language:
seed cell, ... - ovule in the Complete Spelling Dictionary of the Russian Language:
ovule,... - ovule in the Spelling Dictionary:
seed cell, ... - ovule in the Modern Explanatory Dictionary, TSB:
the same as... - CONIFEROS in the Encyclopedia Biology:
, class of gymnosperms; the largest and most widespread group of them. Includes 7 families, approx. 55 births and more than 560... - OVULE in the Encyclopedia Biology:
, the same as the ovule... - PLACENTA in the Encyclopedia Biology:
1) in placental animals and humans - an organ that provides (through the umbilical cord) communication and metabolism between the body of the mother and the fetus... - FERTILIZATION in the Encyclopedia Biology:
, the fusion of male and female reproductive cells (gametes) in plants, animals and humans, resulting in the formation of a fertilized egg (zygote), ... - OVULE in the Big Encyclopedic Dictionary:
(ovule) the formation in seed-bearing plants from which (usually after fertilization) the seed develops. In angiosperms, the ovule is located in the ovary cavity, ... - PLACENTA in the Big Encyclopedic Dictionary:
(Latin placenta from Greek plakus - flat cake) (children’s place), 1) an organ that carries out communication and metabolism between the mother’s body and ... - POLLINATION in the Big Encyclopedic Dictionary:
transfer of pollen from the anther to the stigma of the pistil in flowering plants or to the ovule in gymnosperms. Precedes fertilization. Pollination within... - Yew
(Taxaceae), family of gymnosperms. Evergreen trees and shrubs, usually highly branched, most with needle-shaped, linear or linear-lanceolate, often asymmetrical... - OVULE in the Great Soviet Encyclopedia, TSB:
ovule, a multicellular formation in seed plants from which the seed develops. The main parts of S. are nucellus, integument (or integuments) ... - SEED bud in the Great Soviet Encyclopedia, TSB:
ovule, same as ovule... - POLLINATION in the Modern Encyclopedic Dictionary:
- POLLINATION in the Encyclopedic Dictionary:
transfer of pollen from anthers to the stigma of a pistil in flowering plants or to the ovule in gymnosperms. This is done mainly through...
ovule
Cycad ovules differ in size (from 5-6 cm in length in some cycad species to 5-7 mm in dwarf zamia) and in shape. But at the same time, they are quite similar in the main features of development and internal structure. Openly sitting on the “petiole” of the leaf-shaped megasnorophyll in cycads, hanging on the underside of the thyroid scales in zamias, covered with more or less flat megastrobil scales in other genera, the ovules always consist of a nucellus (ovule nucleus) and an integument covering it.
This thick cover firmly grows together with the nucellus, departing from it only at the apex of the ovule. Here, in the center of the cone-shaped protrusion formed by the integument, there is a micropyle opening, and under it there is a cavity called the pollen chamber. The main part of the ovule is the nucellus. This is the megasporangium itself, which, unlike the open microsnorangia of cycads, like other gymnosperms, is enclosed in a protective cover.
The only functioning megaspore formed in the nucellus as a result of meiosis quickly grows at the expense of the other three, soon dying spores of the tetrad and surrounding cells of the nucellus and produces a well-defined two-layer shell, as is typical for spores of seedless higher plants carried by air currents.
But the megaspore of cycads never leaves the megasporangium, and the named feature of its structure has been preserved as a relic of the past, inherited from distant ancestors who settled with the help of spores. In cycads, the outer shell of the megaspore is in addition impregnated with cutin, which obviously gives it an even more archaic character.
So, sporogenesis is completed. By this time, the integument of the enlarged ovule has already been differentiated into three layers: fleshy outer and inner and hard middle, consisting of dead cells. Both fleshy layers are permeated by a whole system of vascular bundles that provide the growing ovule with the necessary nutrients.
The megaspore formed in the nucellus immediately germinates, forming a female gametophyte. This process was figuratively described by Charles Chamberlain. Following the first nuclear division, many repeated nuclear divisions occur without the formation of cell walls (Fig.
168, 5). Numerous free nuclei (their number, for example, dioona, can reach up to a thousand) end up in a thin wall layer of cytoplasm. Subsequently, gametophyte cells begin to separate, first along the periphery, then closer and closer to the center of the megaspore, until it is all filled with multicellular tissue (Fig. 168, 6).
In terms of total volume and the number of constituent cells, the female gametophyte of cycads is not inferior to even the largest free-living gametophytes (thallusts) of ferns. The female gametophyte develops as a storage tissue (primary endosperm). As it grows, it displaces the nucellus (Fig. 168, 7), then consumes substances from the inner fleshy layer of the integument until this layer turns into a thin film on the inside of the hard “shell.”
The endosperm cells are gradually filled with reserve materials, among which starch predominates (up to 6570% in terms of dry weight in species macrosamia). Fatty oils also accumulate in the endosperm (in the drooping cycad their content can reach up to 23%), as well as proteins. Finally, leukoplasts are found in the cells of the female gametophyte.
Although the female gametophyte of cycads lost during evolution the ability to exist independently outside the ovule, it surprisingly retained the ability to develop chlorophyll (greening) in the light when extracted from the megasporangium. The transformation of leucoplasts into chloroplasts was also observed on ovules, in which it did not occur.
In this case, the gametophyte grew through the micropyle and its protruding end turned green in the light. In this regard, experiments on growing explants (pieces of tissue) from the female gametophyte of cycads in a sterile culture are interesting. Depending on the ratio of various growth stimulants in the nutrient medium, the growing cell mass of the gametophyte forms either roots, then stem buds, then, finally, embryo-like formations (embryoids), i.e.
e. exhibits the features of morphogenesis characteristic of a sporophyte. In the upper part of a normally formed female gametophyte, the female genital organs of archegonia develop under the micropyle (Fig. 168, 7, 16). There are many mother cells of archegonia, and this is another archaic feature of cycads. True, they usually have no more than ten fully developed archegonia.
Absolutely exceptional in this regard microcycas, in which several dozen archegonia are formed. The egg in the archegonia reaches enormous sizes (in microcycas it is up to 6 mm long). The nucleus of the egg is also unusually large; being sometimes up to 500 microns in diameter, it is visible to the naked eye as a dot. On the contrary, the neck of the archegonium is small and usually consists of two small cells, which, at the time of fertilization, mucus, allowing access to the egg.
By this time, a rather large cavity appears between the micropyle and the upper part of the gametophyte (the pollen and archegonial chambers merge when the megaspore shell breaks through), into which wind-borne pollen grains fall. .
help with the lab please! Where are the gills of fish? What organ system are they located in? Where is the two-chamber heart located?its location in the body cavity. What organ system does it belong to? Where are the kidneys located in fish, in what body cavity? What organ system do they belong to? What function do they perform?
1. where are the lungs? what is their structure?2.Why is each lung in a hermetically sealed space?
3. The pulmonary pleura has elasticity: it continuously stretches and contracts. What kind of fabric makes this possible?
4.what is common and what is the difference between gas exchange in the lungs and tissues?
1. What is called escape?
a) a plant without roots; b) method of plant propagation; c) a stem with leaves and buds located on it; d) plant science; e) flowering at least once in life.
2. What attracts pollinating insects to a flower?
a) stamens and pistils; b) pestle; c) calyx; d) calyx and corolla; e) calyx and peduncle.
3. What is indicated by the number 4?
a) flower; b) stem; c) leaf; d) roots; d) seeds.
4. Who invented the first microscope?
a) Leonardo da Vinci; b) Aristotle; c) I. P. Pavlov; d) Antonio Van Leeuwenhoek; d) Democritus.
5. What is the name of the simplest magnifying device that gives a magnification of 2-25 times?
a) magnifying glass; b) electron microscope; c) magnifying glass; d) microscope; d) eyepiece.
6. What is indicated by the number 4?
a) shell; b) core; c) vacuole; d) cytoplasm; d) pores.
7. What are the green plastids called?
a) cytoplasm; b) core; c) chloroplasts; d) pores; e) vacuole.
8. What number indicates vacuoles?
a) 1; b) 2; at 3; d) 4; d) 5.
9. What is the name of the root that develops from the root of the embryo?
a) subordinate clause; b) lateral; c) main; d) additional; d) embryonic.
10. What is soil?
a) plant habitat; b) the place where the roots of flowering plants grow; c) a mixture of clay, humus, sand; d) the top, loose, fertile layer of soil on which plants grow; e) the upper, loose, fertile layer of the lithosphere.
11. Which plant has a fibrous root system?
a) peas; b) beans; c) beans; d) wheat; d) carrots.
12. What is indicated by the number 4?
a) kidney scales; b) embryonic stem; c) rudimentary leaf; d) embryonic shoot; d) embryonic bud.
13. Due to the division of which cells does apical and intercalary growth of plant shoots occur?
a) internodes; b) growth cone; c) growth cone and internodes; d) growth cone and leaf bases; d) root.
14. What is the function of leaves?
a) air nutrition and gas exchange; b) reproduction and storage of substances; c) transport of substances and reproduction; d) evaporation of water and transport of substances; d) attracting insects.
15. What number indicates the stomatal fissure?
a) 14 b) 2; at 3; d) 4; d) 5.
16. What is a growth ring?
a) all layers of wood formed in spring, summer and autumn;
b) plant growth in one year; c) rings on a tree cut; d) a narrow layer of cells with thin membranes; e) a layer of cells under the cortex.
17. In what part of the woody stem does accumulation of reserve substances occur?
a) in the cambium; b) in wood; c) in the core; d) in the cortex; d) in the bast.
18. What is the function of the skin and cork?
a) protective; b) educational; c) storing; d) mechanical.
19. What is shown in the figure by number 4?
a) stigma; b) pestle; c) column; d) calyx; d) anther.
20. Where are the ovules (ovules) located?
a) in the stamens; b) in the receptacle; c) in the ovary; d) in the stigma; d) in the petals.
