Mšeno ( Czech pronunciation: [ˈm̩ʃɛno] ; German : Wemschen ) is a town in Mělník District the Central Bohemian Region of the Czech Republic . It has about 1,400 inhabitants. The historic town centre is well preserved and is protected by law as an urban monument zone .
86-502: The villages of Brusné 2.díl, Hradsko, Olešno, Ráj, Romanov, Sedlec, Skramouš and Vojtěchov are administrative parts of Mšeno. The name is derived from the Czech word mech , i.e. ' moss '. Mšeno is located about 14 kilometres (9 mi) northeast of Mělník and 37 km (23 mi) north of Prague . It lies on the border between the Jizera Table and Ralsko Uplands . The highest point
172-409: A central cell that contains two nuclei. In select angiosperms, special cases occur in which the female gametophyte is not 7 celled with 8 nuclei. On the small end of the spectrum, some species have mature female gametophytes with only 4 cells, each with one nuclei. Conversely, some species have 10-celled mature female gametophytes consisting of 16 total nuclei. Once double fertilization occurs,
258-520: A stem that may be branched or unbranched and has only a limited role in conducting water and nutrients. Although some species have conducting tissues, these are generally poorly developed and structurally different from similar tissue found in vascular plants . Mosses do not have seeds and after fertilisation develop sporophytes with unbranched stalks topped with single capsules containing spores . They are typically 0.2–10 cm (0.1–3.9 in) tall, though some species are much larger. Dawsonia ,
344-407: A challenge. While seed plant gametophyte tissue is typically composed of mononucleate haploid cells (1 x n), specific circumstances can occur in which the ploidy does vary widely despite still being considered part of the gametophyte. In gymnosperms , the male gametophytes are produced inside microspores within the microsporangia located inside male cones or microstrobili . In each microspore,
430-643: A cuticle with stomata, but were much smaller. In bryophytes ( mosses , liverworts , and hornworts ), the gametophyte is the most visible stage of the life cycle. The bryophyte gametophyte is longer lived, nutritionally independent, and the sporophytes are attached to the gametophytes and dependent on them. When a moss spore germinates it grows to produce a filament of cells (called the protonema ). The mature gametophyte of mosses develops into leafy shoots that produce sex organs ( gametangia ) that produce gametes. Eggs develop in archegonia and sperm in antheridia . In some bryophyte groups such as many liverworts of
516-425: A direct tube cell path from the pollination site to the egg is not needed. In most species the germ cell can be more specifically described as a sperm cell which mates with the egg cell during fertilization, though that is not always the case. In some Gnetophyta species, the germ cell will release two sperm nuclei that undergo a rare gymnosperm double fertilization process occurring solely with sperm nuclei and not with
602-407: A few years of exposure to wind and rain. Materials which are porous and moisture retentive, such as brick , wood , and certain coarse concrete mixtures, are hospitable to moss. Surfaces can also be prepared with acidic substances, including buttermilk , yogurt , urine , and gently puréed mixtures of moss samples, water and ericaceous compost . In the cool, humid, cloudy Pacific Northwest , moss
688-916: A garden weed in Vancouver and Seattle areas; Bryum argenteum , the cosmopolitan sidewalk moss, and Ceratodon purpureus , red roof moss, another cosmopolitan species. A few species are wholly aquatic, such as Fontinalis antipyretica , common water moss; and others such as Sphagnum inhabit bogs, marshes and very slow-moving waterways. Such aquatic or semi-aquatic mosses can greatly exceed the normal range of lengths seen in terrestrial mosses. Individual plants 20–30 cm (8–12 in) or more long are common in Sphagnum species for example. But even aquatic species of moss and other bryophytes needs their mature capsules to be exposed to air by seta elongation or seasonal lowering of water level to be able to reproduce. Wherever they occur, mosses require liquid water for at least part of
774-408: A haploid spore that germinates to produce a protonema ( pl. protonemata), which is either a mass of thread-like filaments or thalloid (flat and thallus-like). Massed moss protonemata typically look like a thin green felt, and may grow on damp soil, tree bark, rocks, concrete, or almost any other reasonably stable surface. This is a transitory stage in the life of a moss, but from the protonema grows
860-524: A member of the Polytrichidae is probably Dawsonia superba , a native to New Zealand and other parts of Australasia . The fossil record of moss is sparse, due to their soft-walled and fragile nature. Unambiguous moss fossils have been recovered from as early as the Permian of Antarctica and Russia, and a case has been made for Carboniferous mosses. It has further been claimed that tube-like fossils from
946-469: A new generation of gametophytes. In some multicellular green algae ( Ulva lactuca is one example), red algae and brown algae , sporophytes and gametophytes may be externally indistinguishable (isomorphic). In Ulva , the gametes are isogamous , all of one size, shape and general morphology. In land plants , anisogamy is universal. As in animals, female and male gametes are called, respectively, eggs and sperm. In extant land plants, either
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#17328833732071032-414: A partner that contains the same, or similar, genetic information. By contrast, mosses and other bryophytes have only a single set of chromosomes and so are haploid (i.e. each chromosome exists in a unique copy within the cell). There is a period in the moss life cycle when they do have a double set of paired chromosomes, but this happens only during the sporophyte stage. The moss life-cycle starts with
1118-438: A scent-mediated relationship analogous to the plant-pollinator relationship found in many seed plants. The stinkmoss species Splachnum sphaericum develops insect pollination further by attracting flies to its sporangia with a strong smell of carrion, and providing a strong visual cue in the form of red-coloured swollen collars beneath each spore capsule. Flies attracted to the moss carry its spores to fresh herbivore dung, which
1204-412: A similar purpose. Mosses can be either dioicous (compare dioecious in seed plants) or monoicous (compare monoecious ). In dioicous mosses, male and female sex organs are borne on different gametophyte plants. In monoicous (also called autoicous) mosses, both are borne on the same plant. In the presence of water, sperm from the antheridia swim to the archegonia and fertilisation occurs, leading to
1290-418: A single egg cell. The gametophyte becomes a food storage tissue in the seed. In angiosperms, the megagametophyte is reduced to only a few cells, and is sometimes called the embryo sac . A typical embryo sac contains seven cells and eight nuclei, one of which is the egg cell. Two nuclei fuse with a sperm nucleus to form the primary endospermic nucleus which develops to form triploid endosperm , which becomes
1376-429: A single gametophyte is produced, consisting of four haploid cells produced by meiotic division of a diploid microspore mother cell. At maturity, each microspore-derived gametophyte becomes a pollen grain. During its development, the water and nutrients that the male gametophyte requires are provided by the sporophyte tissue until they are released for pollination. The cell number of each mature pollen grain varies between
1462-465: A single kind of gametophyte. However, not all heteromorphic gametophytes come from heterosporous plants. That is, some plants have distinct egg-producing and sperm-producing gametophytes, but these gametophytes develop from the same kind of spore inside the same sporangium; Sphaerocarpos is an example of such a plant. In seed plants, the microgametophyte is called pollen. Seed plant microgametophytes consists of several (typically two to five) cells when
1548-435: Is deliberately encouraged to grow under aesthetic principles exemplified by Japanese gardening . In old temple gardens, moss can carpet a forest scene. Moss is thought to add a sense of calm, age, and stillness to a garden scene. Moss is also used in bonsai to cover the soil and enhance the impression of age. Rules of cultivation are not widely established. Moss collections are quite often begun using samples transplanted from
1634-448: Is disrupted by fungal chitin . Galotto et al. , 2020 applied chitooctaose and found that tips detected and responded to this chitin derivative by changing gene expression . They concluded that this defense response was probably conserved from the most recent common ancestor of bryophytes and tracheophytes . Orr et al. , 2020 found that the microtubules of growing tip cells were structurally similar to F-actin and served
1720-545: Is famous for its moss garden. The moss garden was created by removing shrubby underbrush and herbaceous groundcovers, thinning trees, and allowing mosses to fill in naturally. Mosses are sometimes used in green roofs . Advantages of mosses over higher plants in green roofs include reduced weight loads, increased water absorption, no fertilizer requirements, and high drought tolerance. Since mosses do not have true roots, they require less planting medium than higher plants with extensive root systems. With proper species selection for
1806-437: Is known as a microgametophyte . Species which produce egg and sperm on separate gametophytes plants are termed dioicous , while those that produce both eggs and sperm on the same gametophyte are termed monoicous . In heterosporous plants (water ferns, some lycophytes, as well as all gymnosperms and angiosperms), there are two distinct types of sporangia , each of which produces a single kind of spore that germinates to produce
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#17328833732071892-446: Is positively associated with the presence of dwarf males in several phyllodioicous species. Dwarf males occur in several unrelated lineages and may be more common than previously thought. For example, it is estimated that between one quarter and half of all dioicous pleurocarps have dwarf males. The moss Physcomitrium patens has been used as a model organism to study how plants repair damage to their DNA, especially
1978-499: Is sometimes allowed to grow naturally as a moss lawn , one that needs little or no mowing, fertilizing or watering. In this case, grass is considered to be the weed. Landscapers in the Seattle area sometimes collect boulders and downed logs growing mosses for installation in gardens and landscapes. Woodland gardens in many parts of the world can include a carpet of natural mosses. The Bloedel Reserve on Bainbridge Island, Washington State,
2064-432: Is successful, the male gametophyte continues to develop. If a tube cell was not developed in the microstrobilus, one is created after pollination via mitosis. The tube cell grows into the diploid tissue of the female cone and may branch out into the megastrobilus tissue or grow straight towards the egg cell. The megastrobilus sporophytic tissue provides nutrients for the male gametophyte at this stage. In some gymnosperms,
2150-451: Is the sexual phase in the life cycle of plants and algae. It develops sex organs that produce gametes , haploid sex cells that participate in fertilization to form a diploid zygote which has a double set of chromosomes. Cell division of the zygote results in a new diploid multicellular organism, the second stage in the life cycle known as the sporophyte . The sporophyte can produce haploid spores by meiosis that on germination produce
2236-534: Is the dominant phase of the life cycle . This contrasts with the pattern in all vascular plants ( seed plants and pteridophytes ), where the diploid sporophyte generation is dominant. Mosses reproduce using spores , not seeds , and have no flowers. Moss gametophytes have stems which may be simple or branched and upright (acrocarp) or prostrate (pleurocarp). The early divergent classes Takakiopsida, Sphagnopsida, Andreaeopsida and Andreaeobryopsida either lack stomata or have pseudostomata that do not form pores. In
2322-545: Is the favoured habitat of the species of this genus. In many mosses, e.g., Ulota phyllantha , green vegetative structures called gemmae are produced on leaves or branches, which can break off and form new plants without the need to go through the cycle of fertilization. This is a means of asexual reproduction , and the genetically identical units can lead to the formation of clonal populations. Moss dwarf males (also known as nannandry or phyllodioicy ) originate from wind-dispersed male spores that settle and germinate on
2408-487: Is the hill Uhelný vrch at 451 m (1,480 ft) above sea level. A large part of the municipal territory lies in the Kokořínsko – Máchův kraj Protected Landscape Area. The Slavic people settled the town area probably in the 5th–6th centuries. The first written mention of Mšeno is from 1306, in a document signed by Wenceslaus III awarding the then-village to aristocrat Hynek of Dubá. He, and his son after him, ensured
2494-547: The Silurian are the macerated remains of moss calyptræ . Mosses also appear to evolve 2–3 times slower than ferns, gymnosperms and angiosperms . Recent research shows that ancient moss could explain why the Ordovician ice ages occurred. When the ancestors of today's moss started to spread on land 470 million years ago, they absorbed CO 2 from the atmosphere and extracted minerals by secreting organic acids that dissolved
2580-466: The Southern Hemisphere . Some naturalists feel that mosses grow on the damper side of trees and rocks. In some cases, such as sunny climates in temperate northern latitudes, this will be the shaded north side of the tree or rock. On steep slopes, it may be the uphill side. For mosses that grow on tree branches, this is generally the upper side of the branch on horizontally growing sections or near
2666-408: The gametophore ("gamete-bearer") that is structurally differentiated into stems and leaves. A single mat of protonemata may develop several gametophore shoots, resulting in a clump of moss. From the tips of the gametophore stems or branches develop the sex organs of the mosses. The female organs are known as archegonia ( sing. archegonium ) and are protected by a group of modified leaves known as
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2752-410: The polysporangiophytes , which include all vascular plants. The spore-producing sporophytes (i.e. the diploid multicellular generation) are short-lived and usually capable of photosynthesis, but are dependent on the gametophyte for water supply and most or all of its nutrients. Also, in the majority of mosses, the spore-bearing capsule enlarges and matures after its stalk elongates, while in liverworts
2838-433: The anther. This creates a 2 or 3 celled male gametophyte which becomes known as the pollen grain once dehiscing occurs. One cell is the tube cell, and the remaining cell/cells are the sperm cells. The development of the three celled male gametophyte prior to dehiscing has evolved multiple times and is present in about a third of angiosperm species allowing for faster fertilization after pollination. Once pollination occurs,
2924-502: The atmosphere. Small organisms feeding on the nutrients created large areas without oxygen, which caused a mass extinction of marine species, while the levels of CO 2 dropped all over the world, allowing the formation of ice caps on the poles. Moss gametophytes are autotrophic and require sunlight to perform photosynthesis . Shade tolerance varies by species, just as it does with higher plants. In most areas, mosses grow chiefly in moist, shaded areas, such as wooded areas and at
3010-430: The capsule enlarges and matures before its stalk elongates. Other differences are not universal for all mosses and all liverworts, but the presence of a clearly differentiated stem with simple-shaped, non-vascular leaves that are not arranged in three ranks, all point to the plant being a moss. Vascular plants have two sets of chromosomes in their vegetative cells and are said to be diploid , i.e. each chromosome has
3096-407: The capsule is mature. Within the capsule, spore-producing cells undergo meiosis to form haploid spores, upon which the cycle can start again. The mouth of the capsule is usually ringed by a set of teeth called peristome. This may be absent in some mosses. Most mosses rely on the wind to disperse the spores. In the genus Sphagnum the spores are projected about 10–20 cm (4–8 in) off
3182-752: The clade that includes Ophioglossaceae and Psilotaceae , the gametophytes are subterranean and subsist by forming mycotrophic relationships with fungi. Homosporous ferns secrete a chemical called antheridiogen . Extant lycophytes produce two different types of gametophytes. In the homosporous families Lycopodiaceae and Huperziaceae , spores germinate into bisexual free-living, subterranean and mycotrophic gametophytes that derive nutrients from symbiosis with fungi. In Isoetes and Selaginella , which are heterosporous, microspores and megaspores are dispersed from sporangia either passively or by active ejection. Microspores produce microgametophytes which produce sperm. Megaspores produce reduced megagametophytes inside
3268-449: The classes Bryopsida, Marchantiopsida, and Anthocerotopsida, respectively. The mosses and liverworts are now considered to belong to a clade called Setaphyta . The mosses, (Bryophyta sensu stricto), are divided into eight classes: vascular plants hornworts liverworts Takakiopsida Sphagnopsida Andreaeopsida Andreaeobryopsida Oedipodiopsida Polytrichopsida Tetraphidopsida Bryopsida Six of
3354-539: The crotch. In cool, humid, cloudy climates, all sides of tree trunks and rocks may be equally moist enough for moss growth. Each species of moss requires certain amounts of moisture and sunlight and thus will grow on certain sections of the same tree or rock. Some mosses grow underwater, or completely waterlogged. Many prefer well-drained locations. There are mosses that preferentially grow on rocks and tree trunks of various chemistries. In boreal forests , some species of moss play an important role in providing nitrogen for
3440-415: The dominant sporophyte tissue for nutrients and water. With the exception of mature pollen , if the gametophyte tissue is separated from the sporophyte tissue it will not survive. Due to this complex relationship and the small size of the gametophyte tissue—in some situations single celled—differentiating with the human eye or even a microscope between seed plant gametophyte tissue and sporophyte tissue can be
3526-413: The eastern edge of the town. The stadium is used for speedway and football. There is also a clay tennis court. The stadium is the home venue for the team PDK Mšeno . A valuable and numerous set of two-storey timbered and half-timbered small-town architecture is typical for the outskirts of the town. Most of the older buildings on the square disappeared during a large fire in 1867. The current appearance of
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3612-405: The ecosystem due to their relationship with nitrogen-fixing cyanobacteria . Cyanobacteria colonize moss and receive shelter in return for providing fixed nitrogen. Moss releases the fixed nitrogen, along with other nutrients, into the soil "upon disturbances like drying-rewetting and fire events", making it available throughout the ecosystem. Moss is often considered a weed in grass lawns, but
3698-585: The edges of streams, but they can grow anywhere in cool, humid, cloudy climates, and some species are adapted to sunny, seasonally dry areas like alpine rocks or stabilized sand dunes. Choice of substrate varies by species as well. Moss species can be classed as growing on: rocks, exposed mineral soil, disturbed soils, acid soil, calcareous soil, cliff seeps and waterfall spray areas, streamsides, shaded humusy soil, downed logs, burnt stumps, tree trunk bases, upper tree trunks, and tree branches or in bogs . Moss species growing on or under trees are often specific about
3784-507: The egg cell becomes the zygote which is then considered sporophyte tissue. Scholars still disagree on whether the fertilized central cell is considered gametophyte tissue. Some botanists consider this endospore as gametophyte tissue with typically 2/3 being female and 1/3 being male, but as the central cell before double fertilization can range from 1n to 8n in special cases, the fertilized central cells range from 2n (50% male/female) to 9n (1/9 male, 8/9th female). However, other botanists consider
3870-613: The eight classes contain only one or two genera each. Polytrichopsida includes 23 genera, and Bryopsida includes the majority of moss diversity with over 95% of moss species belonging to this class. The Sphagnopsida, the peat-mosses, comprise the two living genera Ambuchanania and Sphagnum , as well as fossil taxa. Sphagnum is a diverse, widespread, and economically important one. These large mosses form extensive acidic bogs in peat swamps. The leaves of Sphagnum have large dead cells alternating with living photosynthetic cells. The dead cells help to store water. Aside from this character,
3956-420: The exception of the ancient group Takakiopsida , no known mosses form mycorrhiza , but bryophilous fungi is widespread in moss and other bryophytes, where they live as saprotrophs, parasites, pathogens and mutualists, some of them endophytes . Mosses differ from vascular plants in lacking water-bearing xylem tracheids or vessels . As in liverworts and hornworts , the haploid gametophyte generation
4042-407: The female gametophyte stays singled celled. Mitosis does occur, but no cell divisions are ever made. This results in the mature female gametophyte in some Gnetophyta having many free nuclei in one cell. Once mature, this single celled gametophyte is 90% smaller than the female gametophytes in other gymnosperm orders. After fertilization, the remaining female gametophyte tissue in gymnosperms serves as
4128-472: The female shoot where their growth is restricted to a few millimeters. In some species, dwarfness is genetically determined, in that all male spores become dwarf. More often, it is environmentally determined in that male spores that land on a female become dwarf, while those that land elsewhere develop into large, female-sized males. In the latter case, dwarf males that are transplanted from females to another substrate develop into large shoots, suggesting that
4214-468: The females emit a substance which inhibits the growth of germinating males and possibly also quickens their onset of sexual maturation. The nature of such a substance is unknown, but the phytohormone auxin may be involved Having the males growing as dwarfs on the female is expected to increase the fertilization efficiency by minimizing the distance between male and female reproductive organs. Accordingly, it has been observed that fertilization frequency
4300-443: The fertilization distance. After fertilisation, the immature sporophyte pushes its way out of the archegonial venter. It takes several months for the sporophyte to mature. The sporophyte body comprises a long stalk, called a seta, and a capsule capped by a cap called the operculum . The capsule and operculum are in turn sheathed by a haploid calyptra which is the remains of the archegonial venter. The calyptra usually falls off when
4386-416: The fertilized endospore as sporophyte tissue. Some believe it is neither. In heterosporic plants, there are two distinct kinds of gametophytes. Because the two gametophytes differ in form and function, they are termed heteromorphic , from hetero - "different" and morph "form". The egg-producing gametophyte is known as a megagametophyte , because it is typically larger, and the sperm producing gametophyte
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#17328833732074472-401: The fins on a heat sink. These carry out photosynthesis and may help to conserve moisture by partially enclosing the gas exchange surfaces. The Polytrichopsida differ from other mosses in other details of their development and anatomy too, and can also become larger than most other mosses, with e.g., Polytrichum commune forming cushions up to 40 cm (16 in) high. The tallest land moss,
4558-407: The fusion of developed cells. After fertilization is complete in all orders, the remaining male gametophyte tissue will deteriorate. The female gametophyte in gymnosperms differs from the male gametophyte as it spends its whole life cycle in one organ, the ovule located inside the megastrobilus or female cone. Similar to the male gametophyte, the female gametophyte normally is fully dependent on
4644-402: The gametophyte is free-living and develops outside of the spore wall. Exosporic gametophytes can either be bisexual, capable of producing both sperm and eggs in the same thallus ( monoicous ), or specialized into separate male and female organisms (dioicous). In heterosporous vascular plants (plants that produce both microspores and megaspores), the gametophytes develop endosporically (within
4730-636: The genus Sphagnum ), although they are also used for decorative purposes, such as in gardens and in the florist trade. Traditional uses of mosses included as insulation and for the ability to absorb liquids up to 20 times their weight. Moss is a keystone genus and benefits habitat restoration and reforestation . Botanically, mosses are non-vascular plants in the land plant division Bryophyta. They are usually small (a few centimeters tall) herbaceous (non-woody) plants that absorb water and nutrients mainly through their leaves and harvest carbon dioxide and sunlight to create food by photosynthesis . With
4816-614: The ground by compressed air contained in the capsules; the spores are accelerated to about 36,000 times the earth's gravitational acceleration g . It has recently been found that microarthropods, such as springtails and mites , can effect moss fertilization and that this process is mediated by moss-emitted scents. Male and female fire moss , for example emit different and complex volatile organic scents. Female plants emit more compounds than male plants. Springtails were found to choose female plants preferentially, and one study found that springtails enhance moss fertilization, suggesting
4902-473: The growing prosperity of the area. In 1367, Charles IV promoted Mšeno to a town. During the Thirty Years' War the town suffered, but in the 17th and 18th centuries, the town prospered and the population grew. In 1879, the railroad was built, and in 1901, the school was opened. Mšeno is located on the railway line Mělník – Mladějov . The Mšeno Speedway Stadium is a motorcycle speedway track located on
4988-549: The gymnosperm orders. Cycadophyta have 3 celled pollen grains while Ginkgophyta have 4 celled pollen grains. Gnetophyta may have 2 or 3 celled pollen grains depending on the species, and Coniferophyta pollen grains vary greatly ranging from single celled to 40 celled. One of these cells is typically a germ cell and other cells may consist of a single tube cell which grows to form the pollen tube, sterile cells, and/or prothallial cells which are both vegetative cells without an essential reproductive function. After pollination
5074-664: The leaf can be smooth or it may have teeth. There may be a distinct type of cell defining the edge of the leaf, distinct in shape and/or colour from the other leaf cells. Moss has threadlike rhizoids that anchor them to their substrate, comparable to root hairs rather than the more substantial root structures of spermatophytes . Mosses do not absorb water or nutrients from their substrate through their rhizoids. They can be distinguished from liverworts ( Marchantiophyta or Hepaticae) by their multi-cellular rhizoids. Spore-bearing capsules or sporangia of mosses are borne singly on long, unbranched stems, thereby distinguishing them from
5160-452: The local climate, mosses in green roofs require no irrigation once established and are low maintenance. Mosses are also used on green walls . Gametophyte A gametophyte ( / ɡ ə ˈ m iː t ə f aɪ t / ) is one of the two alternating multicellular phases in the life cycles of plants and algae . It is a haploid multicellular organism that develops from a haploid spore that has one set of chromosomes. The gametophyte
5246-599: The main urban spaces is determined by the late Neoclassical and eclectic buildings. In 1842, the town hall was built, then it was rebuilt and raised in the neo-Gothic style in 1864. The predecessor of today's parish church was allegedly the Romanesque Church of Saint Wenceslaus. In 1876–1879, the Church of Saint Martin was built. It has a high tower and it is the main urban and landscape landmark. Moss Mosses are small, non-vascular flowerless plants in
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#17328833732075332-557: The male gametophyte and soon degrade. The female gametophyte of angiosperms develops in the ovule (located inside the female or hermaphrodite flower ). Its precursor is a diploid megaspore that undergoes meiosis which produces four haploid daughter cells. Three of these independent gametophyte cells degenerate and the one that remains is the gametophyte mother cell which normally contains one nucleus. In general, it will then divide by mitosis until it consists of 8 nuclei separated into 1 egg cell, 3 antipodal cells , 2 synergid cells , and
5418-467: The mature female gametophyte varies drastically between gymnosperm orders. In Cycadophyta, Ginkgophyta, Coniferophyta, and some Gnetophyta, the single celled female gametophyte undergoes many cycles of mitosis ending up consisting of thousands of cells once mature. At a minimum, two of these cells are egg cells and the rest are haploid somatic cells , but more egg cells may be present and their ploidy, though typically haploid, may vary. In select Gnetophyta,
5504-552: The nutrient source for the developing zygote (even in Gnetophyta where the diploid zygote cell is much smaller at that stage, and for a while lives within the single celled gametophyte). The precursor to the male angiosperm gametophyte is a diploid microspore mother cell located inside the anther . Once the microspore undergoes meiosis, 4 haploid cells are formed, each of which is a singled celled male gametophyte. The male gametophyte will develop via one or two rounds of mitosis inside
5590-472: The order Marchantiales , the gametes are produced on specialized structures called gametophores (or gametangiophores). All vascular plants are sporophyte dominant, and a trend toward smaller and more sporophyte-dependent female gametophytes is evident as land plants evolved reproduction by seeds. Those vascular plants, such as clubmosses and many ferns, that produce only one type of spore are said to be homosporous. They have exosporic gametophytes — that is,
5676-426: The pattern in all vascular plants ( seed plants and pteridophytes ), where the diploid sporophyte generation is dominant. Lichens may superficially resemble mosses, and sometimes have common names that include the word "moss" (e.g., " reindeer moss " or " Iceland moss "), but they are fungal symbioses and not related to mosses. The main commercial significance of mosses is as the main constituent of peat (mostly
5762-480: The perichaetum (plural, perichaeta). The archegonia are small flask-shaped clumps of cells with an open neck (venter) down which the male sperm swim. The male organs are known as antheridia ( sing. antheridium ) and are enclosed by modified leaves called the perigonium ( pl. perigonia). The surrounding leaves in some mosses form a splash cup, allowing the sperm contained in the cup to be splashed to neighboring stalks by falling water droplets. Gametophore tip growth
5848-476: The pollen grains exit the sporangium. The megagametophyte develops within the megaspore of extant seedless vascular plants and within the megasporangium in a cone or flower in seed plants. In seed plants, the microgametophyte (pollen) travels to the vicinity of the egg cell (carried by a physical or animal vector) and produces two sperm by mitosis. In gymnosperms, the megagametophyte consists of several thousand cells and produces one to several archegonia , each with
5934-538: The principal sensor of DNA double-strand breaks) showed that these genes are necessary for repair of DNA damage as well as for normal growth and development. More recently, mosses have been grouped with the liverworts and hornworts in the division Bryophyta ( bryophytes , or Bryophyta sensu lato ). The bryophyte division itself contains three (former) divisions: Bryophyta (mosses), Marchantiophyta (liverworts) and Anthocerotophyta (hornworts); it has been proposed that these latter divisions are de-ranked to
6020-464: The production of a diploid sporophyte. The sperm of mosses is biflagellate, i.e. they have two flagellae that aid in propulsion. Since the sperm must swim to the archegonium, fertilisation cannot occur without water. Some species (for example Mnium hornum or several species of Polytrichum ) keep their antheridia in so called 'splash cups', bowl-like structures on the shoot tips that propel the sperm several decimeters when water droplets hit it, increasing
6106-418: The remaining classes, stomata have been lost more than 60 times. Their leaves are simple, usually only a single layer of cells with no internal air spaces, often with thicker midribs (nerves). The nerve can run beyond the edge of the leaf tip, termed excurrent. The tip of the leaf blade can be extended as a hair point, made of colourless cells. These appear white against the dark green of the leaves. The edge of
6192-557: The repair mechanism functions in plants. For example, a study of P. patens mutants defective in Rp RAD51, a gene that encodes a protein at the core of the recombinational repair reaction, indicated that homologous recombination is essential for repairing DNA double-strand breaks in this plant. Similarly, studies of mutants defective in Ppmre11 or Pprad50 (that encode key proteins of the MRN complex ,
6278-565: The repair mechanism known as homologous recombination . If the plant cannot repair DNA damage, e.g., double-strand breaks , in their somatic cells , the cells can lose normal functions or die. If this occurs during meiosis (part of sexual reproduction), they could become infertile. The genome of P. patens has been sequenced, which has allowed several genes involved in DNA repair to be identified. P. patens mutants that are defective in key steps of homologous recombination have been used to work out how
6364-442: The rocks they were growing on. These chemically altered rocks in turn reacted with the atmospheric CO 2 and formed new carbonate rocks in the ocean through the weathering of calcium and magnesium ions from silicate rocks. The weathered rocks also released significant amounts of phosphorus and iron which ended up in the oceans, where it caused massive algal blooms, resulting in organic carbon burial, extracting more carbon dioxide from
6450-473: The species of trees they grow on, such as preferring conifers over broadleaf trees , oaks over alders , or vice versa. While mosses often grow on trees as epiphytes , they are never parasitic on the tree. Mosses are also found in cracks between paving stones in damp city streets, and on roofs. Some species adapted to disturbed, sunny areas are well adapted to urban conditions and are commonly found in cities. Examples would be Rhytidiadelphus squarrosus ,
6536-399: The spore wall). These gametophytes are dioicous , producing either sperm or eggs but not both. In most ferns , for example, in the leptosporangiate fern Dryopteris , the gametophyte is a photosynthetic free living autotrophic organism called a prothallus that produces gametes and maintains the sporophyte during its early multicellular development. However, in some groups, notably
6622-496: The spore wall. At maturity, the megaspore cracks open at the trilete suture to allow the male gametes to access the egg cells in the archegonia inside. The gametophytes of Isoetes appear to be similar in this respect to those of the extinct Carboniferous arborescent lycophytes Lepidodendron and Lepidostrobus . The seed plant gametophyte life cycle is even more reduced than in basal taxa (ferns and lycophytes). Seed plant gametophytes are not independent organisms and depend upon
6708-518: The sporophyte or the gametophyte may be reduced (heteromorphic). No extant gametophytes have stomata , but they have been found on fossil species like the early Devonian Aglaophyton from the Rhynie chert . Other fossil gametophytes found in the Rhynie chert shows they were much more developed than present forms, resembling the sporophyte in having a well-developed conducting strand, a cortex, an epidermis and
6794-417: The surrounding sporophytic tissue for nutrients and the two organisms cannot be separated. However, the female gametophytes of Ginkgo biloba do contain chlorophyll and can produce some of their own energy, though, not enough to support itself without being supplemented by the sporophyte. The female gametophyte forms from a diploid megaspore that undergoes meiosis and starts being singled celled. The size of
6880-433: The tallest moss in the world, can grow to 50 cm (20 in) in height. There are approximately 12,000 species. Mosses are commonly confused with liverworts, hornworts and lichens . Although often described as non-vascular plants , many mosses have advanced vascular systems. Like liverworts and hornworts, the haploid gametophyte generation of mosses is the dominant phase of the life cycle . This contrasts with
6966-486: The taxonomic division Bryophyta ( / b r aɪ ˈ ɒ f ə t ə / , / ˌ b r aɪ . ə ˈ f aɪ t ə / ) sensu stricto . Bryophyta ( sensu lato , Schimp . 1879 ) may also refer to the parent group bryophytes , which comprise liverworts , mosses, and hornworts . Mosses typically form dense green clumps or mats, often in damp or shady locations. The individual plants are usually composed of simple leaves that are generally only one cell thick, attached to
7052-458: The tube cell grows in size and if the male gametophyte is only 2 cells at this stage, the single sperm cell undergoes mitosis to create a second sperm cell. Just like in gymnosperms, the tube cell in angiosperms obtains nutrients from the sporophytic tissue, and may branch out into the pistil tissue or grow directly towards the ovule. Once double fertilization is completed, the tube cell and other vegetative cells, if present, are all that remains of
7138-453: The tube cell will create a direct channel from the site of pollination to the egg cell, in other gymnosperms, the tube cell will rupture in the middle of the megastrobilus sporophyte tissue. This occurs because in some gymnosperm orders, the germ cell is nonmobile and a direct pathway is needed, however, in Cycadophyta and Ginkgophyta, the germ cell is mobile due to flagella being present and
7224-496: The unique branching, thallose (flat and expanded) protonema, and explosively rupturing sporangium place it apart from other mosses. Andreaeopsida and Andreaeobryopsida are distinguished by the biseriate (two rows of cells) rhizoids, multiseriate (many rows of cells) protonema, and sporangium that splits along longitudinal lines. Most mosses have capsules that open at the top. Polytrichopsida have leaves with sets of parallel lamellae, flaps of chloroplast-containing cells that look like
7310-458: The wild in a water-retaining bag. Some species of moss can be extremely difficult to maintain away from their natural sites with their unique requirements of combinations of light, humidity, substrate chemistry, shelter from wind, etc. Growing moss from spores is even less controlled. Moss spores fall in a constant rain on exposed surfaces; those surfaces which are hospitable to a certain species of moss will typically be colonised by that moss within
7396-504: The year to complete fertilisation. Many mosses can survive desiccation , sometimes for months, returning to life within a few hours of rehydration. It is generally believed that in the Northern Hemisphere , the north side of trees and rocks will generally have more luxuriant moss growth on average than other sides. The reason is assumed to be because sunshine on the south side causes a dry environment. The reverse would be true in
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