Mosses are small, non-vascular flowerless plants in the taxonomic division Bryophyta (, ) ''

sensu stricto ''Sensu'' is a Latin word meaning "in the sense of". It is used in a number of fields including biology, geology, linguistics, semiotics, and law. Commonly it refers to how strictly or loosely an expression is used in describing any particular co ...

''. Bryophyta ('' sensu lato'', Schimp. 1879) may also refer to the parent group bryophytes, which comprise

liverworts The Marchantiophyta () are a division of non-vascular land plants commonly referred to as hepatics or liverworts. Like mosses and hornworts, they have a gametophyte-dominant life cycle, in which cells of the plant carry only a single set of ge ...

, mosses, and

hornwort Hornworts are a group of non-vascular Embryophytes (land plants) constituting the division Anthocerotophyta (). The common name refers to the elongated horn-like structure, which is the sporophyte. As in mosses and liverworts, hornworts have a ...

s. Mosses typically form dense green clumps or mats, often in damp or shady locations. The individual plants are usually composed of simple

leaves A leaf (plural, : leaves) is any of the principal appendages of a vascular plant plant stem, stem, usually borne laterally aboveground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", wh ...

that are generally only one cell thick, attached to a

stem Stem or STEM may refer to: Plant structures * Plant stem, a plant's aboveground axis, made of vascular tissue, off which leaves and flowers hang * Stipe (botany), a stalk to support some other structure * Stipe (mycology), the stem of a mushro ...

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

sporophyte A sporophyte () is the diploid multicellular stage in the life cycle of a plant or alga which produces asexual spores. This stage alternates with a multicellular haploid gametophyte phase. Life cycle The sporophyte develops from the zygote pr ...

s with unbranched stalks topped with single capsules containing spores. They are typically tall, though some species are much larger. ''Dawsonia'', the tallest moss in the world, can grow to in height. There are approximately 12,000 species. Mosses are commonly confused with liverworts, hornworts and

lichen A lichen ( , ) is a composite organism that arises from algae or cyanobacteria living among filaments of multiple fungi species in a mutualistic relationship.division, all of them having the

haploid Ploidy () is the number of complete sets of chromosomes in a cell, and hence the number of possible alleles for autosomal and pseudoautosomal genes. Sets of chromosomes refer to the number of maternal and paternal chromosome copies, respectively ...

gametophyte generation as the dominant phase of the life cycle (though in fact many mosses have advanced vascular systems). This contrasts with the pattern in all vascular plants ( seed plants and pteridophytes), where the

diploid Ploidy () is the number of complete sets of chromosomes in a cell, and hence the number of possible alleles for autosomal and pseudoautosomal genes. Sets of chromosomes refer to the number of maternal and paternal chromosome copies, respectively ...

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 not related to mosses. The main commercial significance of mosses is as the main constituent of peat (mostly 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.

Physical characteristics

Description

Botanically, mosses are

non-vascular plant Non-vascular plants are plants without a vascular system consisting of xylem and phloem. Instead, they may possess simpler tissues that have specialized functions for the internal transport of water. Non-vascular plants include two distantly rel ...

s in the land plant division Bryophyta. They are usually small (a few centimeters tall)

herbaceous Herbaceous plants are vascular plants that have no persistent woody stems above ground. This broad category of plants includes many perennials, and nearly all annuals and biennials. Definitions of "herb" and "herbaceous" The fourth edition of t ...

(non-woody) plants that absorb water and nutrients mainly through their leaves and harvest carbon dioxide and sunlight to create food by photosynthesis. With the exception of the ancient group Takakiopsida, no known mosses form

mycorrhiza A mycorrhiza (from Greek μύκης ', "fungus", and ῥίζα ', "root"; pl. mycorrhizae, mycorrhiza or mycorrhizas) is a symbiotic association between a fungus and a plant. The term mycorrhiza refers to the role of the fungus in the plant ...

, but bryophilous fungi is widespread in moss and other bryophytes, where they live as saprotrophs, parasites, pathogens and mutualists, some of them endophytes. They differ from vascular plants in lacking water-bearing xylem tracheids or

vessels Vessel(s) or The Vessel may refer to: Biology *Blood vessel, a part of the circulatory system and function to transport blood throughout the body *Lymphatic vessel, a thin walled, valved structure that carries lymph *Vessel element, a narrow wat ...

. As in

and

s, the

gametophyte generation is the dominant phase of the life cycle. This contrasts with the pattern in all vascular plants ( seed plants and pteridophytes), where the

generation is dominant. Mosses reproduce using

spore In biology, a spore is a unit of sexual or asexual reproduction that may be adapted for dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores form part of the life cycles of many plants, algae, f ...

s, not seeds, and have no flowers. Moss leaf under microscope

Moss gametophytes have stems which may be simple or branched and upright or prostrate. The early divergent classes Takakiopsida, Sphagnopsida, Andreaeopsida and Andreaeobryopsida either lack

stoma In botany, a stoma (from Greek ''στόμα'', "mouth", plural "stomata"), also called a stomate (plural "stomates"), is a pore found in the epidermis of leaves, stems, and other organs, that controls the rate of gas exchange. The pore is bor ...

ta or have pseudostomata that do not form pores. In the remaining classes, stomata has 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. They do not have proper roots, but have threadlike rhizoids that anchor them to their substrate. Mosses do not absorb water or nutrients from their substrate through their rhizoids. They can be distinguished from

( 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 the polysporangiophytes, which include all vascular plants. The spore-bearing sporophytes (i.e. the

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 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.

Life cycle

Vascular plants have two sets of chromosomes in their vegetative cells and are said to be

, i.e. each chromosome has 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

(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

stage.

The moss life-cycle starts with a haploid

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 the

gametophore Gametophores are prominent structures in seedless plants on which the reproductive organs are borne. The word gametophore and ‘-phore’ (Greek Φορά, "to be carried"). In mosses, liverworts and ferns (Archegoniata), the gametophores support ...

("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 An archegonium (pl: archegonia), from the ancient Greek ''ἀρχή'' ("beginning") and ''γόνος'' ("offspring"), is a multicellular structure or organ of the gametophyte phase of certain plants, producing and containing the ovum or female ga ...

(''sing.''

archegonium An archegonium (pl: archegonia), from the ancient Greek ''ἀρχή'' ("beginning") and ''γόνος'' ("offspring"), is a multicellular structure or organ of the gametophyte phase of certain plants, producing and containing the ovum or female ga ...

) and are protected by a group of modified leaves known as 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 is disrupted by fungal

chitin Chitin ( C8 H13 O5 N)n ( ) is a long-chain polymer of ''N''-acetylglucosamine, an amide derivative of glucose. Chitin is probably the second most abundant polysaccharide in nature (behind only cellulose); an estimated 1 billion tons of chit ...

. Galotto ''et al.'', 2020 apply chitooctaose and find that tips detect and respond to this chitin derivative by changing

gene expression Gene expression is the process by which information from a gene is used in the synthesis of a functional gene product that enables it to produce end products, protein or non-coding RNA, and ultimately affect a phenotype, as the final effect. The ...

. They find this defense response is probably conserved from the most recent common ancestor of bryophytes and tracheophytes. Orr ''et al.'', 2020 find that the

microtubule Microtubules are polymers of tubulin that form part of the cytoskeleton and provide structure and shape to eukaryotic cells. Microtubules can be as long as 50 micrometres, as wide as 23 to 27 nm and have an inner diameter between 11 an ...

s of growing tip cells are structurally similar to F-actin and serve a similar purpose. Mosses can be either

dioicous Dioicy () is a sexual system where archegonia and antheridia are produced on separate gametophytes. It is one of the two main sexual systems in bryophytes. Both dioicous () and monoicous gametophytes produce gametes in gametangia by mitosis rathe ...

(compare

dioecious Dioecy (; ; adj. dioecious , ) is a characteristic of a species, meaning that it has distinct individual organisms (unisexual) that produce male or female gametes, either directly (in animals) or indirectly (in seed plants). Dioecious reproductio ...

in seed plants) or monoicous (compare

monoecious Monoecy (; adj. monoecious ) is a sexual system in seed plants where separate male and female cones or flowers are present on the same plant. It is a monomorphic sexual system alongside gynomonoecy, andromonoecy and trimonoecy. Monoecy is conne ...

). 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 Fertilisation or fertilization (see spelling differences), also known as generative fertilisation, syngamy and impregnation, is the fusion of gametes to give rise to a new individual organism or offspring and initiate its development. Proce ...

occurs, leading to 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 the fertilization distance. After fertilisation, the immature sporophyte pushes its way out of the archegonial venter. It takes about a quarter to half a year for the

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 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 off the ground by compressed air contained in the capsules; the spores are accelerated to about 36,000 times the earth's gravitational acceleration ''g''. Moss Gametophytes Sporophytes

It has recently been found that microarthropods, such as

springtails Springtails (Collembola) form the largest of the three lineages of modern hexapods that are no longer considered insects (the other two are the Protura and Diplura). Although the three orders are sometimes grouped together in a class called Ent ...

and

mites Mites are small arachnids (eight-legged arthropods). Mites span two large orders of arachnids, the Acariformes and the Parasitiformes, which were historically grouped together in the subclass Acari, but genetic analysis does not show clear evid ...

, can effect moss fertilization and that this process is mediated by moss-emitted scents. Male and female

fire moss ''Ceratodon purpureus'' is a dioicous moss with a color ranging from yellow-green to red. The height amounts to 3 centimeters. It is found worldwide, mainly in urban areas and next to roads on dry sand soils. It can grow in a very wide variety o ...

, for example emit different and complex volatile organic scents. Female plants emit more compounds than male plants.

Springtails Springtails (Collembola) form the largest of the three lineages of modern hexapods that are no longer considered insects (the other two are the Protura and Diplura). Although the three orders are sometimes grouped together in a class called Ent ...

were found to choose female plants preferentially, and one study found that springtails enhance moss fertilization, suggesting a scent-mediated relationship analogous to the plant-pollinator relationship found in many seed plants. The stinkmoss species ''

Splachnum sphaericum ''Splachnum sphaericum'', also known as pinkstink dung moss, is a species of moss. This species occurs in North America. It also occurs in upland Britain, where it is known as round-fruited collar-moss and in north temperate and boreal regions of ...

'' 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 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 Asexual reproduction is a type of reproduction that does not involve the fusion of gametes or change in the number of chromosomes. The offspring that arise by asexual reproduction from either unicellular or multicellular organisms inherit the fu ...

, and the genetically identical units can lead to the formation of clonal populations.

Dwarf males

Moss dwarf males (also known as nannandry or phyllodioicy) originate from wind-dispersed male

s that settle and germinate on 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 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 Auxins (plural of auxin ) are a class of plant hormones (or plant-growth regulators) with some morphogen-like characteristics. Auxins play a cardinal role in coordination of many growth and behavioral processes in plant life cycles and are essenti ...

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 is positively associated with the presence of dwarf males in several phyllodioicous species. Dwarf males occur in several unrelated lineages and is showing to be more common than previously thought. For example, it is estimated that between one quarter and half of all

pleurocarps have dwarf males.

DNA repair

The moss '' Physcomitrella patens'' has been used as a

model organism A model organism (often shortened to model) is a non-human species that is extensively studied to understand particular biological phenomena, with the expectation that discoveries made in the model organism will provide insight into the workin ...

to study how plants repair damage to their DNA, especially the repair mechanism known as homologous recombination. If the plant cannot repair DNA damage, e.g., double-strand breaks, in their

somatic cell A somatic cell (from Ancient Greek σῶμα ''sôma'', meaning "body"), or vegetal cell, is any biological cell forming the body of a multicellular organism other than a gamete, germ cell, gametocyte or undifferentiated stem cell. Such cells compo ...

s, 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 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 The MRN complex (MRX complex in yeast) is a protein complex consisting of Mre11, Rad50 and Nbs1 (also known as Nibrin in humans and as Xrs2 in yeast). In eukaryotes, the MRN/X complex plays an important role in the initial processing of double-st ...

, 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.

Classification

More recently, mosses have been grouped with the

and

s 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 the classes Bryopsida, Marchantiopsida, and Anthocerotopsida, respectively. The mosses and liverworts are now considered to belong to a clade called

Setaphyta The Setaphyta are a clade within the Bryophyta which includes Marchantiophytina (liverworts) and Bryophytina (mosses). Anthocerotophytina (hornworts) are excluded. A 2018 study found through molecular sequencing that liverworts are more close ...

. The mosses, (Bryophyta sensu stricto), are divided into eight classes: Haeckel Muscinae

Six of 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 ''Ambuchanania leucobryoides'' is the only species in the monotypic genus ''Ambuchanania''. It is a ''Sphagnum''-like moss endemic to Tasmania. Originally described as a species of ''Sphagnum'', it is now a separate genus named after the origin ...

'' 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, 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 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 ''Polytrichum commune'' (also known as common haircap, great golden maidenhair, great goldilocks, common haircap moss, or common hair moss) is a species of moss found in many regions with high humidity and rainfall. The species can be exceptional ...

'' forming cushions up to high. The tallest land moss, a member of the Polytrichidae is probably ''

Dawsonia superba ''Dawsonia superba'' is a moss in the class Polytrichaceae that is found in Australia, New Guinea, Malaysia and New Zealand. ''D. superba'' is the tallest self-supporting moss in the world, reaching heights of 60 cm. It has analogous structures ...

'', a native to New Zealand and other parts of Australasia.

Geological history

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 The Carboniferous ( ) is a geologic period and system of the Paleozoic that spans 60 million years from the end of the Devonian Period million years ago ( Mya), to the beginning of the Permian Period, million years ago. The name ''Carbonifero ...

mosses. It has further been claimed that tube-like fossils from the

Silurian The Silurian ( ) is a geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at million years ago ( Mya), to the beginning of the Devonian Period, Mya. The Silurian is the shortest period of the Paleozo ...

are the macerated remains of moss

calyptræ In botany, an operculum () or calyptra () is a cap-like structure in some flowering plants, mosses, and fungi. It is a covering, hood or lid, describing a feature in plant morphology. Flowering plants In flowering plants, the operculum, also ...

. 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 CO₂ from the atmosphere and extracted minerals by secreting organic acids that dissolved the rocks they were growing on. These chemically altered rocks in turn reacted with the atmospheric CO₂ 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 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 CO₂ dropped all over the world, allowing the formation of ice caps on the poles.

Ecology

Habitat

File:Mossopolis.jpg, Dense moss colonies in a cool coastal forest File:MossForest.jpg, A cool high altitude/latitude moss forest; the forest floor is covered in moss, beneath conifers File:Route 1 , Between Vik and Kirkjubæjarklaustur - panoramio (7).jpg, Moss colonizes a basalt flow, in Iceland File:Moss (Iceland) 03.jpg, Moss growing along seeps and springs in newly deposited basaltic rock, Iceland. File:Steinerne Rinne bei Obererasbach im Altmühltal.jpg, Moss growing along the stream from a karst spring; travertine deposits from the stream water and the moss overgrows it, forming this ridge, with the stream on top. File:Winter moss.jpg, Moss with sporophytes on brick File:Mech plonnik mlode sporofity.jpg, Young

s of the common moss ''Tortula muralis'' (wall screw-moss) File:Taiwan 2009 JinGuaShi Historic Gold Mine Moss Covered Retaining Wall FRD 8940.jpg, Retaining wall covered in moss File:Michiganmosspatch.jpg, A small clump of moss beneath a conifer (a shady, usually dry place) File:MossOnConcreteWall.jpg, Moss on a concrete wall File:Moss (Bryophyta) on the forest floor in Broken Bow, Oklahoma.jpg, Moss (Bryophyta) on the forest floor in Broken Bow, Oklahoma Since moss gametophytes are autotrophic they require enough

sunlight Sunlight is a portion of the electromagnetic radiation given off by the Sun, in particular infrared, visible, and ultraviolet light. On Earth, sunlight is scattered and filtered through Earth's atmosphere, and is obvious as daylight when t ...

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 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

humus In classical soil science, humus is the dark organic matter in soil that is formed by the decomposition of plant and animal matter. It is a kind of soil organic matter. It is rich in nutrients and retains moisture in the soil. Humus is the Lati ...

y soil, downed logs, burnt stumps, tree trunk bases, upper tree trunks, and tree branches or in

bog A bog or bogland is a wetland that accumulates peat as a deposit of dead plant materials often mosses, typically sphagnum moss. It is one of the four main types of wetlands. Other names for bogs include mire, mosses, quagmire, and muskeg; a ...

s. Moss species growing on or under trees are often specific about the species of trees they grow on, such as preferring

conifers Conifers are a group of cone-bearing seed plants, a subset of gymnosperms. Scientifically, they make up the division Pinophyta (), also known as Coniferophyta () or Coniferae. The division contains a single extant class, Pinopsida. All extan ...

over

broadleaf trees A broad-leaved, broad-leaf, or broadleaf tree is any tree within the diverse botanical group of angiosperms that has flat leaves and produces seeds inside of fruits. It is one of two general types of trees, the other being a conifer, a tree with n ...

, 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 ''Rhytidiadelphus squarrosus'' is a species of moss known as springy turf-moss in the United Kingdom, and square goose neck moss in the United States. It is widespread in Eurasia and North America, and has been introduced to the Southern Hemisph ...

'', 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 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 the year to complete fertilisation. Many mosses can survive

desiccation Desiccation () is the state of extreme dryness, or the process of extreme drying. A desiccant is a hygroscopic (attracts and holds water) substance that induces or sustains such a state in its local vicinity in a moderately sealed container. ...

, sometimes for months, returning to life within a few hours of rehydration. It is generally believed that in the

Northern Hemisphere The Northern Hemisphere is the half of Earth that is north of the Equator. For other planets in the Solar System, north is defined as being in the same celestial hemisphere relative to the invariable plane of the solar system as Earth's Nort ...

, 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 Sunlight is a portion of the electromagnetic radiation given off by the Sun, in particular infrared, visible, and ultraviolet light. On Earth, sunlight is scattered and filtered through Earth's atmosphere, and is obvious as daylight when th ...

on the south side causes a dry environment. The reverse would be true in 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 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.

Relationship with cyanobacteria

In boreal forests, some species of moss play an important role in providing nitrogen for the ecosystem due to their relationship with nitrogen-fixing

cyanobacteria Cyanobacteria (), also known as Cyanophyta, are a phylum of gram-negative bacteria that obtain energy via photosynthesis. The name ''cyanobacteria'' refers to their color (), which similarly forms the basis of cyanobacteria's common name, blu ...

. 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.

Cultivation

Moss is often considered a weed in grass lawns, but 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 Bonsai ( ja, 盆栽, , tray planting, ) is the Japanese art of growing and training miniature trees in pots, developed from the traditional Chinese art form of ''penjing''. Unlike ''penjing'', which utilizes traditional techniques to produce ...

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 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 a few years of exposure to wind and rain. Materials which are porous and moisture retentive, such as

brick A brick is a type of block used to build walls, pavements and other elements in masonry construction. Properly, the term ''brick'' denotes a block composed of dried clay, but is now also used informally to denote other chemically cured cons ...

, 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 Ericaceous may refer to: * Ericaceae, the heather family * Calcifuges, all plants which dislike alkaline (chalky) soil – including heathers, rhododendron and camellia * Ericaceous bed, a bed with acidic soil typically having a pH between 4.5 and 6 ...

. In the cool, humid, cloudy Pacific Northwest, moss is sometimes allowed to grow naturally as a

moss lawn Moss lawns are lawns composed of moss, which occur naturally, but can also be cultivated like grass lawns (see images). They are a defining element in moss gardens. Moss lawns are drought-tolerant and rarely need misting once established (the av ...

, 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 The Bloedel Reserve is a forest garden on Bainbridge Island, Washington, United States. It was created by Virginia and Prentice Bloedel, the vice-chairman of the lumber company MacMillan Bloedel Limited, under the influence of the conservatio ...

on Bainbridge Island, Washington State, 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.

Green roofs and walls

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 the local climate, mosses in green roofs require no irrigation once established and are low maintenance. Mosses are also used on green walls.

Mossery

A passing fad for moss-collecting in the late 19th century led to the establishment of mosseries in many British and American gardens. The mossery is typically constructed out of slatted wood, with a flat roof, open to the north side (maintaining shade). Samples of moss were installed in the cracks between wood slats. The whole mossery would then be regularly moistened to maintain growth.

Aquascaping

Aquascaping Aquascaping is the craft of arranging aquatic plants, as well as rocks, stones, cavework, or driftwood, in an aesthetically pleasing manner within an aquarium—in effect, gardening under water. Aquascape designs include a number of distinct styl ...

uses many aquatic mosses. They do best at low nutrient, light, and heat levels, and propagate fairly readily. They help maintain a water chemistry suitable for aquarium fish. They grow more slowly than many aquarium plants, and are fairly hardy.

Growth inhibition

Moss can be a troublesome weed in containerized nursery operations and greenhouses. Vigorous moss growth can inhibit seedling emergence and penetration of water and fertilizer to the plant roots. Moss growth can be inhibited by a number of methods: * Decreasing availability of water through drainage. * Increasing direct sunlight. * Increasing number and resources available for competitive plants like grasses. * Increasing the

soil pH Soil pH is a measure of the acidity or basicity (alkalinity) of a soil. Soil pH is a key characteristic that can be used to make informative analysis both qualitative and quantitatively regarding soil characteristics. pH is defined as the neg ...

with the application of lime. * Heavy traffic or manually disturbing the moss bed with a rake * Application of chemicals such as ferrous sulfate (e.g., in lawns) or bleach (e.g., on solid surfaces). * In containerized nursery operations, coarse mineral materials such as sand, gravel, and rock chips are used as a fast-draining top dressing in plant containers to discourage moss growth. The application of products containing ferrous sulfate or

ferrous ammonium sulfate Ammonium iron(II) sulfate, or Mohr's salt, is the inorganic compound with the formula (NH4)2Fe(SO4)2(H2O)6. Containing two different cations, Fe2+ and NH4+, it is classified as a double salt of ferrous sulfate and ammonium sulfate. It is a com ...

will kill moss; these ingredients are typically in commercial moss control products and fertilizers.

Sulfur Sulfur (or sulphur in British English) is a chemical element with the symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with a chemical formula ...

and iron are

essential nutrient A nutrient is a substance used by an organism to survive, grow, and reproduce. The requirement for dietary nutrient intake applies to animals, plants, fungi, and protists. Nutrients can be incorporated into cells for metabolic purposes or excret ...

s for some competing plants like grasses. Killing moss will not prevent regrowth unless conditions favorable to their growth are changed.

Uses

Traditional

Preindustrial societies made use of the mosses growing in their areas. Laplanders, North American tribes, and other circumpolar people used mosses for bedding. Mosses have also been used as insulation both for dwellings and in clothing. Traditionally, dried moss was used in some Nordic countries and Russia as an insulator between logs in

log cabin A log cabin is a small log house, especially a less finished or less architecturally sophisticated structure. Log cabins have an ancient history in Europe, and in America are often associated with first generation home building by settlers. Eur ...

s, and tribes of the northeastern United States and southeastern Canada used moss to fill chinks in wooden longhouses. Circumpolar and alpine peoples have used mosses for insulation in boots and mittens. Ötzi the Iceman had moss-packed boots. The capacity of dried mosses to absorb fluids has made their use practical in both medical and culinary uses. North American tribal people used mosses for diapers, wound dressing, and menstrual fluid absorption. Tribes of the Pacific Northwest in the United States and Canada used mosses to clean salmon prior to drying it, and packed wet moss into pit ovens for steaming camas bulbs. Food storage baskets and boiling baskets were also packed with mosses. Recent research investigating the Neanderthals remains recovered from El Sidrón have provided evidence that their diet would have consisted primarily of pine nuts, moss and mushrooms. This is contrasted by evidence from other European locations which point to a more carnivorous diet. In Finland, peat mosses have been used to make bread during

famines A famine is a widespread scarcity of food, caused by several factors including war, natural disasters, crop failure, population imbalance, widespread poverty, an economic catastrophe or government policies. This phenomenon is usually accompani ...

Commercial

There is a substantial market in mosses gathered from the wild. The uses for intact moss are principally in the florist trade and for home decoration. Decaying moss in the genus ''Sphagnum'' is also the major component of peat, which is "mined" for use as a

fuel A fuel is any material that can be made to react with other substances so that it releases energy as thermal energy or to be used for work. The concept was originally applied solely to those materials capable of releasing chemical energy but ...

, as a horticultural soil additive, and in smoking

malt Malt is germinated cereal grain that has been dried in a process known as " malting". The grain is made to germinate by soaking in water and is then halted from germinating further by drying with hot air. Malted grain is used to make beer, wh ...

in the production of

Scotch whisky Scotch whisky (; sco, Scots whisky/whiskie, whusk(e)y; often simply called whisky or Scotch) is malt whisky or grain whisky (or a blend of the two), made in Scotland. All Scotch whisky was originally made from malted barley. Commercial distil ...

. '' Sphagnum'' moss, generally the species ''S. cristatum'' and ''S. subnitens'', is harvested while still growing and is dried out to be used in nurseries and horticulture as a plant growing medium. Some ''Sphagnum'' mosses can absorb up to 20 times their own weight in water.The Plant Underworld, Sphagnum and Water, Australian Botanic Garden
In World War I, ''Sphagnum'' mosses were used as first-aid dressings on soldiers' wounds, as these mosses said to absorb liquids three times faster than cotton, retain liquids better, better distribute liquids uniformly throughout themselves, and are cooler, softer, and be less irritating. It is also claimed to have antibacterial properties. Native Americans were one of the peoples to use ''Sphagnum'' for diapers and napkins, which is still done in Canada. In rural UK, ''

Fontinalis antipyretica ''Fontinalis antipyretica'', greater water-moss, or common water moss, is a species of submerged aquatic moss belonging to the subclass Bryidae. It is found in both still and flowing freshwater in Europe, Asia, Greenland and Africa. In North Ame ...

'' was traditionally used to extinguish fires as it could be found in substantial quantities in slow-moving rivers and the moss retained large volumes of water which helped extinguish the flames. This historical use is reflected in its specific Latin/ Greek name, the approximate meaning of which is "against fire". In Mexico, moss is used as a Christmas decoration. '' Physcomitrella patens'' is increasingly used in biotechnology. Prominent examples are the identification of moss genes with implications for crop improvement or human health and the safe production of complex

biopharmaceuticals A biopharmaceutical, also known as a biological medical product, or biologic, is any pharmaceutical drug product manufactured in, extracted from, or semisynthesized from biological sources. Different from totally synthesized pharmaceuticals, t ...

in the moss

bioreactor A bioreactor refers to any manufactured device or system that supports a biologically active environment. In one case, a bioreactor is a vessel in which a chemical reaction, chemical process is carried out which involves organisms or biochemistry, ...

, developed by

Ralf Reski Ralf Reski (born 18 November 1958 in Gelsenkirchen) is a German professor of plant biotechnology and former dean of the Faculty of Biology of the University of Freiburg. He is also affiliated to the French École supérieure de biotechnologie ...

and his co-workers. London installed several structures called "City Trees": moss-filled walls, each of which is claimed to have "the air-cleaning capability of 275 regular trees" by consuming nitrogen oxides and other types of air pollution and producing oxygen.

References

External links

Information, diagrams and photos

Moss grower's handbook (2.3 9MB PDF file)

The British Bryological Society

World of Mosses – Watercolour paintings of moss by Robert Muma
{{Authority control Extant Carboniferous first appearances Mississippian first appearances