Editing Moss (section)

===Life cycle===
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Vascular [[plant]]s have two sets of [[chromosome]]s in their vegetative cells and are said to be [[diploid]], i.e. each chromosome has a partner that contains the same, or similar, genetic information. By contrast, mosses and other [[bryophyte]]s 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.

[[File:Lifecycle moss svg diagram.svg|thumb|300px|Life cycle of a typical moss (''[[Polytrichum commune]]'')]]

The moss life-cycle starts with 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 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 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.<ref name="vanderVelde2001" />

Gametophore tip growth is disrupted by fungal [[chitin]].<ref name="Delaux-Schornack-2021">{{cite journal | last1=Delaux | first1=Pierre-Marc | last2=Schornack | first2=Sebastian | title=Plant evolution driven by interactions with symbiotic and pathogenic microbes | journal=[[Science (journal)|Science]] | publisher=[[American Association for the Advancement of Science]] (AAAS) | volume=371 | issue=6531 | date=2021-02-19 | issn=0036-8075 | doi=10.1126/science.aba6605 | pages=1–10 | pmid=33602828 | s2cid=231955632| url=https://hal.archives-ouvertes.fr/hal-03327916/file/Delaux%20Schornack%20-%20HAL.pdf }}</ref><ref name="Bibeau-et-al-2021">{{cite journal | last1=Bibeau | first1=Jeffrey P. | last2=Galotto | first2=Giulia | last3=Wu | first3=Min | last4=Tüzel | first4=Erkan | last5=Vidali | first5=Luis | title=Quantitative cell biology of tip growth in moss | journal=[[Plant Molecular Biology]] | publisher=[[Springer Science+Business Media|Springer]] | volume=107 | issue=4–5 | date=2021-04-06 | issn=0167-4412 | doi=10.1007/s11103-021-01147-7 | pages=227–244| pmid=33825083 | pmc=8492783 | bibcode=2021PMolB.107..227B }}</ref><ref name="Sun-et-al-2020">{{cite journal | last1=Sun | first1=Guiling | last2=Bai | first2=Shenglong | last3=Guan | first3=Yanlong | last4=Wang | first4=Shuanghua | last5=Wang | first5=Qia | last6=Liu | first6=Yang | last7=Liu | first7=Huan | last8=Goffinet | first8=Bernard | last9=Zhou | first9=Yun | last10=Paoletti | first10=Mathieu | last11=Hu | first11=Xiangyang | last12=Haas | first12=Fabian B. | last13=Fernandez-Pozo | first13=Noe | last14=Czyrt | first14=Alia | last15=Sun | first15=Hang | last16=Rensing | first16=Stefan A. | last17=Huang | first17=Jinling | title=Are fungi-derived genomic regions related to antagonism towards fungi in mosses? | journal=[[New Phytologist]] | publisher=New Phytologist Foundation ([[Wiley publishing|Wiley]]) | volume=228 | issue=4 | date=2020-07-31 | issn=0028-646X | doi=10.1111/nph.16776 | pages=1169–1175 | pmid=32578878 | s2cid=220047618| doi-access=free | bibcode=2020NewPh.228.1169S }}</ref> Galotto ''et al.'', 2020 applied [[chitooctaose]] and found that tips detected and responded to this chitin derivative by changing [[gene expression]].<ref name="Delaux-Schornack-2021" /><ref name="Bibeau-et-al-2021" /><ref name="Sun-et-al-2020" /> They concluded that this defense response was probably [[conserved sequence|conserved]] from the [[most recent common ancestor]] of [[bryophyte]]s and [[tracheophytes]].<ref name="Delaux-Schornack-2021" /> Orr ''et al.'', 2020 found that the [[microtubule]]s of growing tip cells were structurally similar to [[F-actin]] and served a similar purpose.<ref name="Bibeau-et-al-2021" />

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 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.<ref name="vanderVelde2001">{{Cite journal|title = The reproductive biology of Polytrichum formosum: clonal structure and paternity revealed by microsatellites|last1 = van der Velde|first1 = M.|journal = Molecular Ecology|doi = 10.1046/j.0962-1083.2001.01385.x|pmid = 11742546|issue = 10|pages = 2423–2434|last2 = During|first2 = H. J.|last3 = van de Zande|first3 = L.|last4 = Bijlsma|first4 = R.|volume = 10|year = 2001| bibcode=2001MolEc..10.2423V |s2cid = 19716812}}</ref>

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 (Botany)|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.{{citation needed|date=April 2023}}

Most mosses rely on the wind to disperse the spores. In the [[genus]] ''[[Sphagnum]]'' the [[Sphagnum#Spore dispersal|spores are projected]] about {{Convert|10-20|cm|4 = 0|abbr = on}} off the ground by compressed air contained in the capsules; the spores are accelerated to about 36,000 times the [[Gravity of Earth|earth's gravitational acceleration ''g'']].<ref>{{cite journal|doi= 10.1126/science.1193047|author= Johan L. van Leeuwen |title= Launched at 36,000''g'' |journal=Science|pages= 395–6|issue= 5990 |volume= 329 |date= July 23, 2010|pmid= 20651138|s2cid= 206527957 }}</ref><ref>{{cite journal|doi= 10.1126/science.1190179|author1=Dwight K. Whitaker  |author2=Joan Edwards  |name-list-style=amp |title= ''Sphagnum'' Moss Disperses Spores with Vortex Rings |journal=Science|page= 406|issue= 5990 |volume= 329 |date= July 23, 2010|pmid= 20651145|bibcode=2010Sci...329..406W |s2cid=206526774 }}</ref>

[[File:Moss Gametophytes Sporophytes.JPG|thumb|300px|A patch of moss showing both gametophytes (the low, leaf-like forms) and sporophytes (the tall, stalk-like forms)]]

It has recently been found that microarthropods, such as [[springtails]] and [[mites]], can effect moss fertilization<ref name="cronberg2006">{{Cite journal | last1 = Cronberg | first1 = N. | last2 = Natcheva | first2 = R. | last3 = Hedlund | first3 = K. | doi = 10.1126/science.1128707 | title = Microarthropods Mediate Sperm Transfer in Mosses | journal = Science | volume = 313 | issue = 5791 | pages = 1255 | year = 2006 | pmid =  16946062| s2cid = 11555211 }}</ref> and that this process is mediated by moss-emitted scents. Male and female [[fire moss]], for example, emit different and complex volatile organic scents.<ref name="rosenstiel2012">{{Cite journal | last1 = Rosenstiel | first1 = T. N. | last2 = Shortlidge | first2 = E. E. | last3 = Melnychenko | first3 = A. N. | last4 = Pankow | first4 = J. F. | last5 = Eppley | first5 = S. M. | title = Sex-specific volatile compounds influence microarthropod-mediated fertilization of moss | doi = 10.1038/nature11330 | journal = Nature | volume = 489 | issue = 7416 | pages = 431–433 | year = 2012 | pmid =  22810584| bibcode = 2012Natur.489..431R | s2cid = 4419337 }}</ref> 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 a scent-mediated relationship analogous to the plant-pollinator relationship found in many seed plants.<ref name="rosenstiel2012" /> 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 is the favoured habitat of the species of this genus.<ref name=vaizey>{{cite journal | last1 = Vaizey | first1 = J. R. | year = 1890 | title = On the Morphology of the Sporophyte of ''Splachnum luteum'' | journal = Annals of Botany | volume = 1 | pages = 1–8 | doi = 10.1093/oxfordjournals.aob.a090623 }}</ref>

In many mosses, e.g., ''Ulota phyllantha'', green vegetative structures called [[gemma (botany)|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 [[cloning|clonal]] populations.