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moss

moss / môs/ • n. 1. a small flowerless green plant that lacks true roots, growing in low carpets or rounded cushions in damp habitats and reproducing by means of spores released from stalked capsules: the trees are overgrown with vines and moss | the bog is home to rare mosses. • Class Musci, division Bryophyta. ∎  used in names of algae, lichens, and higher plants resembling moss, e.g., reindeer moss, Ceylon moss, Spanish moss. 2. Scot. & N. English a bog, esp. a peat bog. • v. [usu. as adj.] (mossed) cover with moss. DERIVATIVES: moss·like / -ˌlīk/ adj.

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moss

moss Any of c.14,000 species of small, simple non-flowering green plants that typically grow in colonies, often forming dense carpets. They reproduce by means of spores produced in a capsule on a long stalk. The spores germinate into branching filaments, from which buds arise that grow into moss plants. Mosses grow on soil, rocks and tree trunks in a wide variety of habitats, especially in shady, damp places. See also alternation of generations; bryophyte

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moss

moss
A. (dial.) bog, swamp OE.
;
B. small plant of the class Musci. XIV. OE. mos = MLG., (M)Du., OHG. mos (G. moos) bog, moss:- Gmc. *musam, rel. to ON. mosi wk. m. bog, moss, and further to OE. mēos, OHG. mios (G. mies) moss (:- Gmc. *meus-), ON. mýrr MIRE, and outside Gmc. to L. muscus, OSl. mǔchǔ moss:- IE. *mus-). The application in Eng. to the plant may be due to ON. mosi.

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Moss (city, Norway)

Moss (môs), city (1995 pop. 25,253), capital of Østfold co., SE Norway, a port on the Oslofjord. It is a commercial, industrial, and tourist center, with shipyards, sawmills, textile factories, metalworks, and breweries. On Aug. 14, 1814, the convention establishing the personal union of Sweden and Norway was signed there.

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moss (in botany)

moss, any species of the class Bryopsida, in which the liverworts are sometimes included. Mosses and liverworts together comprise the division Bryophyta, the first green land plants to develop in the process of evolution. It is believed that they evolved from certain very primitive vascular plants and have not given rise to any other type of plant. Their rootlike rhizomes and leaflike processes lack the vascular structure (xylem and phloem) of the true roots, stems, and leaves found in higher plants. Although limited to moist habitats because they require water for fertilization, bryophytes are usually extremely hardy and grow everywhere except in the sea. Mosses, the more complex class structurally, usually grow vertically rather than horizontally, like the liverworts. The green moss plant visible to the naked eye, seldom over 6 in. (15.2 cm) in height, is the gametophyte generation (see reproduction). Except for the commercially valuable sphagnum or peat moss, mosses are of little direct importance to humans. They are of some value in soil formation and filling in of barren habitats (e.g., dried lakes) prior to the growth of higher plants and also provide food for certain animals. Unrelated plants sharing the name moss include the club moss, flowering moss, or pyxie (of the diapensia family), Irish moss, or carrageen (see algae), reindeer moss (a lichen), and Spanish moss. Mosses are classified in the division Bryophyta, class Bryopsida.

See A. J. Grout, Moss Flora of North America (3 vol., 1928–39, repr. 1972).

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moss

moss The common name for a plant belonging to the class Musci.

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moss

mossacross, boss, Bros, cos, cross, crosse, doss, dross, emboss, en brosse, floss, fosse, gloss, Goss, joss, Kos, lacrosse, loss, moss, MS-DOS, Ross, toss •LaosÁyios Nikólaos, chaos •Eos • Helios •Chios, Khíos •Lesbos • straw boss • Phobos • rooibos •extrados • kudos • reredos • intrados •Calvados • Argos • Lagos • logos •Marcos • telos •Delos, Melos •Byblos • candyfloss •tholos, Vólos •bugloss • omphalos • Pátmos •Amos, Deimos, Sámos •Demos • peatmoss • cosmos • Los Alamos • Lemnos • Hypnos • Minos •Mykonos • tripos • topos • Atropos •Ballesteros, pharos, Saros •Imbros • criss-cross • rallycross • Eros •albatross • monopteros • Dos Passos •Náxos • Hyksos • Knossos • Santos •benthos •bathos, pathos •ethos • Kórinthos

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Moss

Moss

Bryophyte characteristics

Moss characteristics

Life cycle

Habitat and ecology

Evolution

Importance to humans

Resources

The mosses are the largest of the three classes in the plant phylum Bryophyta. They have been divided into three subclasses: the true mosses (Bryideae), the peat mosses (Sphagnideae), and the granite mosses (Andreaeideae). The familiar small, green, and leafy moss plant is known as the gametophyte. This haploid multicellular phase is dominant in the moss life cycle. The mosses are the most broadly distributed of the three classes of bryophytes (which also includes liverworts and hornworts). There are more than 15,000 species of mosses worldwide.

Bryophyte characteristics

Mosses share numerous features with the two other classes of bryophytes. They are more complex than algae yet simpler than the higher vascular plants. Like higher plants, bryophytes use chlorophyll-a, chlorophyll-b, and carotenoids as photosynthetic pigments. Their food reserves are stored as starch. Cellulose is found in their cell walls (cell-produced rigid structures that are external to the plasma membrane) and they form cell plates (structures made of membranes representing the site of newly created cells) during cell division. Their spores, units capable of maturation, develop as a tetrad (a group of four cells) by meiosis, divisions of the cell nucleus that halve the number of chromosomes.

Two features of bryophytes tend to restrict them to moist environments, such as bogs and woodlands. First, unlike vascular plants, bryophytes lack a system with xylem and phloem for efficient transport of water and food. Second, the male sperm cells of bryophytes must swim through water to reach the female egg cells.

Bryophytes also differ from higher plants in that the sporophyte, the spore-producing diploid tissue, is nutritionally dependent on the dominant haploid gametophyte. In higher plants the gametophyte is dependent on the dominant sporophyte.

Moss characteristics

Mosses have several characteristics that distinguish them from other bryophytes. Only mosses have a multicellular rhizoid, a root like subterranean tissue that absorbs water and nutrients from the soil. Liverworts and hornworts have single celled rhizoids. Mosses have radial symmetry, in that a cut down the long axis of an individual gives two similar halves. Hornworts and mosses are unique bryophytes in that they have stomata, cells specialized for photosynthetic gas exchange, on their sporophytes. Liverwort sporophytes lack stomata. In addition mosses do not have true leaves or stems. Their leaf like structures are called phyllids. They are typically only one cell thick, although phyllids in some species are several cells thick.

Life cycle

A haploid moss spore germinates and gives rise to a protonema, a green multicellular tissue that superficially resembles a filamentous green alga. Under appropriate conditions, other moss cells can also be induced to form protonema. The protonema is typically subterranean and is rarely seen.

Buds form on the protonema producing the familiar leafy moss plant. Male and female reproductive organs typically grow near the tips of the leafy gametophyte. These are termed antheridia and archegonia, respectively. Most species are monoecious, in that antheridia and archegonia are on the same individual. Other species are dioecious in that antheridia and archegonia are on different individuals.

The archegonium is multicellular and produces a single immobile egg. The antheridium is also multicellular but it makes many motile sperm cells each with two flagella. A sperm cell swims through water to reach the archegonium. Then it travels down a tube in the archegonium to fertilize the egg and form a diploid zygote.

The zygote undergoes repeated cell division and elongates to become a multicellular sporophyte while still attached to the leafy gametophyte. The thin stalk of the sporophyte is called the seta and the enlarged tip is called the capsule. The moss sporophyte is photosynthetic early in development, but later depends on the gametophyte for nutrition. Late in development, the sporophyte dries out and turns brown. Then the operculum (lid) comes off the capsule and haploid spores are released to the environment. The subclass of true mosses (Bryideae) are unique in having special peristome teeth inside the cap, which regulate spore dispersal.

Habitat and ecology

Mosses are typically found in moist environments although most species can withstand prolonged periods of desiccation. In terrestrial ecosystems, mosses are important in preventing soil erosion. Numerous species of moss are found in fresh water but there are no salt water species.

Mosses are particularly prominent in the tropics, however, they have a significant presence in the boreal forest, the woodlands of the temperate zones, and tundra regions. In the arctic tundra, mosses can constitute 50-90% of the ecosystems biomass.

Evolution

The earliest known moss fossil is from the early Carboniferous period, about 320 million years ago. Mosses are not well-represented in the fossil record because their soft tissue is not well preserved. An examination of extant species indicates that bryophytes are a polyphyletic group. They appear to have evolved from more than one ancestral line.

Most botanists believe that mosses evolved from aquatic ancestors but there is debate about their evolutionary ancestry. It is commonly accepted by most botanists that mosses evolved from a simpler filamentous green alga. Although bryophytes appear intermediate in complexity between algae and vascular plants, they are unlikely to be an evolutionary missing link between these two groups.

Importance to humans

Compared to other groups of plants, mosses are not very economically important. However, Sphagnum moss has a long history of diverse uses and is certainly the moss of greatest importance to humans. In its natural habitat, sphagnum selectively absorbs certain ions and secretes others. The bogs in which it grows become acidic and anaerobic over time, and the decomposition-rate by bacteria is particularly slow in these bogs. Organisms buried in sphagnum bogs remain well-preserved for a very long time.

Currently, the most common use of Sphagnum is by gardeners. They often mix dried sphagnum (peat moss) with soil to improve the water-holding capacity of soil. The American white cedar grows in sphagnum bogs. This tree has been used for a long time to make shingles for houses because its wood resists rotting. In the 1700s, most of Americas white cedar came from sphagnum bogs in the Pine Barrens of New Jersey. After all the standing trees were cut down, trees that were buried deep in the bogs for up to 1,000 years were dug up and used. These cedar trees had been preserved by the anaerobic and acidic environment created by sphagnum moss. Cedar was mined from New Jerseys sphagnum bogs until the 1850s.

Sphagnum has antiseptic properties and can hold up to 20 times its weight in water, much more than cotton. Sphagnum was used as a bandage for soldiers wounded in the Russo-Japanese War (1904-1905) and World War I. By using sphagnum for bandages, cotton could be saved for making gun powder.

Peat derived largely from sphagnum is important as a fossil fuel, particularly in Scotland and Ireland. In Scotland, sphagnum also has an important role in the making of scotch whiskey. Many scotches are made from grains are steeped in water from a sphagnum bog during the malting procedure. Later, the malted grains are boiled over a fire of burning sphagnum peat. These uses of sphagnum peat impart a characteristic flavor and aroma to scotch whiskey.

Many conservationists have been concerned with the irreversible loss of valuable wetlands due to peat moss harvesting. The process of peat harvesting includes draining the sphagnum bog, after which specialized machines clear the drained bog of large vegetation. Next, ditches are dug that lower the water table, allowing peat to dry. Heavy vacuuming equipment is then used to remove the dried peat. In recent years, peat harvesting has increased because new uses for peat have been discovered. An especially important use is as a natural oil absorbent to clean up oil spills. However, the concerns of environmentalists have created codes of practice for harvesting peat, so that it will remain a sustainable resource.

It is estimated that peat can reform at a rate of about 0.1-0.7 inch (1-2 mm) per year. Therefore, it is believed that harvested peatlands can be restored to ecologically balanced systems within 20 years after harvesting. Many efforts have been made to ensure the survival of bogs. In Canada for instance, millions of acres of bogs have been protected by creating natural parks that are not harvested. Also, new understanding of wetland ecology has started to help accelerate the restoration of sphagnum bogs after peat harvest. Some hope to accelerate the process from 20 years to as little as five years by transplanting live sphagnum moss back into harvested areas, and by spreading sphagnum spores to encourage growth.

There are also several vernacular plant names in which the word moss is misused. Spanish moss is a flowering plant and relative of the pineapple. Reindeer moss is a lichen. Moss pink is a garden flower in the Phlox genus. Irish moss is a red alga. Club moss is a simple vascular plant.

KEY TERMS

Biomass Total weight, volume, or energy equivalent of all living organisms within a given area.

Cytokinesis The physical division of the cytoplasm of a eukaryotic cell to form two daughter cells, each housing a newly formed nuclei.

Diploid Nucleus or cell containing two copies of each chromosome generated by fusion of two haploid nuclei.

Gametophyte The haploid, gamete-producing generation in a plants life cycle.

Haploid Nucleus or cell containing one copy of each chromosome.

Meiosis Division of the cells nucleus in which the number of chromosomes is reduced by half; typically from the diploid to the haploid.

Sporophyte The diploid, spore-producing generation in a plants life cycle.

Resources

BOOKS

Greenaway, T. Mosses and Liverworts. Austin, TX: Raintree Steck-Verlag, 1992.

Margulis, Lynn, and Karlene V. Schwartz. Five Kingdoms New York: W.H. Freeman, 1988.

Richardson, D.H.S. The Biology of Mosses New York: Wiley, 1981.

OTHER

Ohio State University, Horticulture and Crop Science Bryophyta <http://hcs.osu.edu/hcs300/liver2.htm> (accessed December 4, 2006).

University of California Museum of Paleontology. Introduction to the Bryophyta <http://www.ucmp.berkeley.edu/plants/bryophyta/bryophyta.html> (accessed December 4, 2006).

Peter A. Ensminger

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Moss

Moss

The mosses are the largest of the three classes in the plant phylum Bryophyta. They have been divided into three subclasses: the true mosses (Bryideae), the peat mosses (Sphagnideae), and the granite mosses (Andreaeideae). The familiar small, green, and "leafy" moss plant is known as the gametophyte. This haploid multicellular phase is dominant in the moss life cycle. The mosses are the most broadly distributed of the three classes of bryophytes (which also includes liverworts and hornworts). There are more than 15,000 species of mosses worldwide.


Bryophyte characteristics

Mosses share numerous features with the two other classes of bryophytes. They are more complex than algae yet simpler than the higher vascular plants. Like higher plants, bryophytes use chlorophyll-a, chlorophyll-b, and carotenoids as photosynthetic pigments. Their food reserves are stored as starch. Cellulose is found in their cell walls (cell-produced rigid structures that are external to the plasma membrane ) and they form cell plates (structures made of membranes representing the site of newly created cells) during cell division . Their spores, units capable of maturation, develop as a tetrad (a group of four cells) by meiosis , divisions of the cell nucleus that halve the number of chromosomes.

Two features of bryophytes tend to restrict them to moist environments, such as bogs and woodlands. First, unlike vascular plants, bryophytes lack a system with xylem and phloem for efficient transport of water and food. Second, the male sperm cells of bryophytes must swim through water to reach the female egg cells.

Bryophytes also differ from higher plants in that the sporophyte, the spore-producing diploid tissue , is nutritionally dependent on the dominant haploid gametophyte. In higher plants the gametophyte is dependent on the dominant sporophyte.

Moss characteristics

Mosses have several characteristics that distinguish them from other bryophytes. Only mosses have a multicellular rhizoid, a root-like subterranean tissue that absorbs water and nutrients from the soil . Liverworts and hornworts have single celled rhizoids. Mosses have radial symmetry , in that a cut down the long axis of an individual gives two similar halves. Hornworts and mosses are unique bryophytes in that they have stomata, cells specialized for photosynthetic gas exchange, on their sporophytes. Liverwort sporophytes lack stomata. In addition mosses do not have true leaves or stems. Their leaf-like structures are called phyllids. They are typically only one cell thick, although phyllids in some species are several cells thick.


Life cycle

A haploid moss spore germinates and gives rise to a protonema, a green multicellular tissue that superficially resembles a filamentous green alga. Under appropriate conditions, other moss cells can also be induced to form protonema. The protonema is typically subterranean and is rarely seen.

Buds form on the protonema producing the familiar "leafy" moss plant. Male and female reproductive organs typically grow near the tips of the "leafy" gametophyte. These are termed antheridia and archegonia, respectively. Most species are monoecious, in that antheridia and archegonia are on the same individual. Other species are dioecious in that antheridia and archegonia are on different individuals.

The archegonium is multicellular and produces a single immobile egg. The antheridium is also multicellular but it makes many motile sperm cells each with two flagella . A sperm cell swims through water to reach the archegonium. Then it travels down a tube in the archegonium to fertilize the egg and form a diploid zygote.

The zygote undergoes repeated cell division and elongates to become a multicellular sporophyte while still attached to the 'leafy' gametophyte. The thin stalk of the sporophyte is called the seta and the enlarged tip is called the capsule. The moss sporophyte is photosynthetic early in development, but later depends on the gametophyte for nutrition . Late in development, the sporophyte dries out and turns brown. Then the operculum (lid) comes off the capsule and haploid spores are released to the environment. The subclass of true mosses (Bryideae) are unique in having special peristome teeth inside the cap, which regulate spore dispersal.


Habitat and ecology

Mosses are typically found in moist environments although most species can withstand prolonged periods of desiccation. In terrestrial ecosystems, mosses are important in preventing soil erosion . Numerous species of moss are found in fresh water but there are no salt water species.

Mosses are particularly prominent in the tropics, however, they have a significant presence in the boreal forest, the woodlands of the temperate zones, and tundra regions. In the arctic tundra, mosses can constitute 50-90% of the ecosystem's biomass .


Evolution

The earliest known moss fossil is from the early Carboniferous period, about 320 million years ago. Mosses are not well-represented in the fossil record because their soft tissue is not well preserved. An examination of extant species indicates that bryophytes are a polyphyletic group. They appear to have evolved from more than one ancestral line.

Most botanists believe that mosses evolved from aquatic ancestors but there is debate about their evolutionary ancestry. It is commonly accepted by most botanists that mosses evolved from a simpler filamentous green alga. Although bryophytes appear intermediate in complexity between algae and vascular plants, they are unlikely to be an evolutionary "missing link" between these two groups.


Importance to humans

Compared to other groups of plants, mosses are not very economically important. However, Sphagnum moss has a long history of diverse uses and is certainly the moss of greatest importance to humans. In its natural habitat , sphagnum selectively absorbs certain ions and secretes others. The bogs in which it grows become acidic and anaerobic over time , and the decomposition rate by bacteria is particularly slow in these bogs. Organisms buried in sphagnum bogs remain well-preserved for a very long time.

Currently, the most common use of Sphagnum is by gardeners. They often mix dried sphagnum (peat moss) with soil to improve the water-holding capacity of soil. The American white cedar grows in sphagnum bogs. This tree has been used for a long time to make shingles for houses because its wood resists rotting. In the 1700s, most of America's white cedar came from sphagnum bogs in the Pine Barrens of New Jersey. After all the standing trees were cut down, trees that were buried deep in the bogs for up to 1,000 years were dug up and used. These cedar trees had been preserved by the anaerobic and acidic environment created by sphagnum moss. Cedar was mined from New Jersey's sphagnum bogs until the 1850s.

Sphagnum has antiseptic properties and can hold up to twenty times its weight in water, much more than cotton . Sphagnum was used as a bandage for soldiers wounded in the Russo-Japanese War (1904-05) and World War I. By using sphagnum for bandages, cotton could be saved for making gun powder.

Peat derived largely from sphagnum is important as a fossil fuel, particularly in Scotland and Ireland. In Scotland, sphagnum also has an important role in the making of scotch whiskey. Many scotches are made from grains are steeped in water from a sphagnum bog during the malting procedure. Later, the malted grains are boiled over a fire of burning sphagnum peat. These uses of sphagnum peat impart a characteristic flavor and aroma to scotch whiskey.

Many conservationists have been concerned with the irreversible loss of valuable wetlands due to peat moss harvesting. The process of peat harvesting includes draining the sphagnum bog, after which specialized machines clear the drained bog of large vegetation. Next, ditches are dug that lower the water table, allowing peat to dry. Heavy vacuuming equipment is then used to remove the dried peat. In recent years, peat harvesting has increased because new uses for peat have been discovered. An especially important use is as a natural oil absorbent to clean up oil spills . However, the concerns of environmentalists have created codes of practice for harvesting peat, so that it will remain a sustainable resource.

It is estimated that peat can reform at a rate of about 0.1-0.7 in (1-2 mm) per year. Therefore, it is believed that harvested peatlands can be restored to ecologically balanced systems within twenty years after harvesting. Many efforts have been made to ensure the survival of bogs. In Canada for instance, millions of acres of bogs have been protected by creating natural parks that are not harvested. Also, new understanding of wetland ecology has started to help accelerate the restoration of sphagnum bogs after peat harvest. Some hope to accelerate the process from twenty years to as little as five years by transplanting live sphagnum moss back into harvested areas, and by spreading sphagnum spores to encourage growth.

There are also several vernacular plant names in which the word moss is misused. Spanish moss is a flowering plant and relative of the pineapple. Reindeer moss is a lichen. Moss pink is a garden flower in the Phlox genus. Irish moss is a red alga. Club moss is a simple vascular plant.


Resources

books

Greenaway, T. Mosses and Liverworts. Austin, TX: Raintree Steck-Verlag, 1992.

Margulis, Lynn, and Karlene V. Schwartz. Five Kingdoms New York: W.H. Freeman, 1988.

Richardson, D.H.S. The Biology of Mosses New York: Wiley, 1981.


Peter A. Ensminger

KEY TERMS

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Biomass

—Total weight, volume, or energy equivalent of all living organisms within a given area.

Cytokinesis

—The physical division of the cytoplasm of a eukaryotic cell to form two daughter cells, each housing a newly formed nuclei.

Diploid

—Nucleus or cell containing two copies of each chromosome generated by fusion of two haploid nuclei.

Gametophyte

—The haploid, gamete-producing generation in a plant's life cycle.

Haploid

—Nucleus or cell containing one copy of each chromosome.

Meiosis

—Division of the cell's nucleus in which the number of chromosomes is reduced by half; typically from the diploid to the haploid.

Sporophyte

—The diploid, spore-producing generation in a plant's life cycle.

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