View source for Biology:Bryophyte

{{short description|Terrestrial plants that lack vascular tissue}}
[[File:MarchantiophytaSp.NonDéterminéeFL3.jpg|thumb|''Marchantia'', an example of a liverwort (Marchantiophyta)]]
[[File:Moss (Bryophyta) on the forest floor in Broken Bow, Oklahoma.jpg|thumb|An example of moss (Bryophyta) on the forest floor in Broken Bow, Oklahoma]]

'''Bryophytes''' ({{IPAc-en|'|b|r|aI|%|oU|f|aI|t|s}}) are a group of land plants, sometimes treated as a taxonomic [[Biology:Division|division]], that contains three groups of non-vascular land plants ([[Biology:Embryophyte|embryophyte]]s): the [[Biology:Marchantiophyta|liverworts]], [[Biology:Hornwort|hornwort]]s and [[Biology:Moss|moss]]es.<ref name="pmid12415314">{{Cite journal |last=Hedges |first=S. Blair |date=November 2002 |title=The origin and evolution of model organisms |journal=Nature Reviews Genetics |volume=3 |issue=11 |pages=838–849 |doi=10.1038/nrg929 |pmid=12415314 |s2cid=10956647}}</ref> In the [[Biology:Sensu#Common qualifiers|strict sense]], '''Bryophyta''' consists of the mosses only. Bryophytes are characteristically limited in size and prefer moist habitats although they can survive in drier environments.<ref name="McMahon2012">{{Cite book |last1=Levetin |first1=Estelle |title=Plants and Society |last2=McMahon |first2=Karen |publisher=McGraw-Hill |year=2012 |isbn=978-0-07-352422-1 |location=New York, NY |page=139}}</ref> The bryophytes consist of about 20,000 plant species.<ref>{{Cite web |title=Bryophytes (Mosses and liverworts) — The Plant List |url=http://www.theplantlist.org/browse/B/ |access-date=2017-04-11 |website=theplantlist.org}}</ref><ref name="WhatrBryo">{{Cite web |title=What are Bryophytes |url=http://bryophytes.plant.siu.edu/bryojustified.html |url-status=dead |archive-url=https://web.archive.org/web/20181019163320/http://bryophytes.plant.siu.edu/bryojustified.html |archive-date=2018-10-19 |access-date=2009-05-31 |website=Southern Illinois University Carbondale}}</ref> Bryophytes produce enclosed reproductive structures (gametangia and sporangia), but they do not produce [[Biology:Flower|flower]]s or [[Biology:Seed|seed]]s. They reproduce sexually by [[Biology:Spore|spore]]s and asexually by fragmentation or the production of [[Biology:Gemma (botany)|gemmae]].<ref name="Vanderpoorten">{{Cite book |last1=Vanderpoorten |first1=Alain |title=Introduction to Bryophytes |last2=Goffinet |first2=Bernard |publisher=Cambridge University Press |year=2009 |isbn=978-0-511-54013-4 |location=Cambridge |page=3}}</ref> Though bryophytes were considered a paraphyletic group in recent years, almost all of the most recent [[Biology:Phylogenetics|phylogenetic]] evidence supports the [[Biology:Monophyly|monophyly]] of this group, as originally classified by Wilhelm Schimper in 1879.<ref name="Schimp">{{Cite book |last=Schimper |first=W.P. |title=Handbuch der Palaeontologie |publisher=R. Oldenbourg |year=1879 |editor-last=Zittel |editor-first=K.A. |volume=2 |chapter=Bryophyta}}</ref> The term ''bryophyte'' comes {{etymology|grc|''βρύον'' (brúon)|tree moss, liverwort||''φυτόν'' (phutón)|plant}}.

==Features==
The defining features of bryophytes are:
* Their life cycles are dominated by a multicellular [[Biology:Gametophyte|gametophyte]] stage
* Their [[Biology:Sporophyte|sporophyte]]s are unbranched
* They do not have a true [[Biology:Vascular tissue|vascular tissue]] containing [[Biology:Lignin|lignin]] (although some have specialized tissues for the transport of water)<ref name="Lucasetal">{{Cite journal |last1=Lucas |first1=William J. |last2=Groover |first2=Andrew |last3=Lichtenberger |first3=Raffael |last4=Furuta |first4=Kaori |last5=Yadav |first5=Shri-Ram |last6=Helariutta |first6=Ykä |last7=He |first7=Xin-Qiang |last8=Fukuda |first8=Hiroo |last9=Kang |first9=Julie |last10=Brady |first10=Siobhan M. |last11=Patrick |first11=John W. |date=April 2013 |title=The Plant Vascular System: Evolution, Development and Functions F |journal=Journal of Integrative Plant Biology |volume=55 |issue=4 |pages=294–388 |doi=10.1111/jipb.12041 |pmid=23462277 |hdl-access=free |hdl=10261/76903}}</ref>

== Habitat ==
Bryophytes exist in a wide variety of habitats. They can be found growing in a range of temperatures (cold arctics and in hot deserts), elevations (sea-level to alpine), and moisture (dry deserts to wet rain forests). Bryophytes can grow where vascularized plants cannot because they do not depend on roots for uptake of [[Biology:Plant nutrients in soil|nutrients from soil]]. Bryophytes can survive on rocks and bare soil.<ref name="anbg">{{Cite web |last=Lepp |first=Heino |date=28 February 2008 |title=Habitats |url=https://www.anbg.gov.au/bryophyte/ecology-habitats.html |website=Australian Bryophytes |publisher=Australian National Botanic Gardens}}</ref>

==Life cycle==
[[File:Moss alternation of generations 03-2012.png|thumb|550px|The life cycle of a dioicous bryophyte. The gametophyte (haploid) structures are shown in green, the sporophyte (diploid) in brown.]]

Like all land plants (embryophytes), bryophytes have [[Biology:Biological life cycle|life cycle]]s with [[Biology:Alternation of generations|alternation of generations]].<ref name="Duckett">{{Cite journal |last1=Ligrone |first1=Roberto |last2=Duckett |first2=Jeffrey G. |last3=Renzaglia |first3=Karen S. |date=April 2012 |title=Major transitions in the evolution of early land plants: a bryological perspective |journal=Annals of Botany |volume=109 |issue=5 |pages=851–871 |doi=10.1093/aob/mcs017 |pmc=3310499 |pmid=22356739}}</ref> In each cycle, a [[Biology:Haploid|haploid]] [[Biology:Gametophyte|gametophyte]], each of whose cells contains a fixed number of unpaired [[Biology:Chromosome|chromosome]]s, alternates with a diploid [[Biology:Sporophyte|sporophyte]], whose cells contain two sets of paired chromosomes. Gametophytes produce haploid sperm and eggs which fuse to form diploid zygotes that grow into sporophytes. Sporophytes produce haploid spores by [[Biology:Meiosis|meiosis]], that grow into gametophytes.

Bryophytes are gametophyte dominant,<ref name="Carrington">{{Cite web |last=C.M. Sean Carrington |date=2013-11-04 |title=The Bryophytes |url=http://ecflora.cavehill.uwi.edu/bio_courses/bl14apl/bryo1.htm |publisher=The University of the West Indies |access-date=2020-03-05 |archive-date=2020-02-05 |archive-url=https://web.archive.org/web/20200205160203/http://ecflora.cavehill.uwi.edu/bio_courses/bl14apl/bryo1.htm |url-status=dead }}</ref> meaning that the more prominent, longer-lived plant is the haploid gametophyte. The diploid sporophytes appear only occasionally and remain attached to and nutritionally dependent on the gametophyte.<ref>{{Cite journal |last1=Johnson |first1=M G |last2=Shaw |first2=A J |date=24 February 2016 |title=The effects of quantitative fecundity in the haploid stage on reproductive success and diploid fitness in the aquatic peat moss Sphagnum macrophyllum |journal=Heredity |volume=116 |issue=6 |pages=523–530 |doi=10.1038/hdy.2016.13 |pmc=4868265 |pmid=26905464}}</ref> In bryophytes, the sporophytes are always unbranched and produce a single [[Biology:Sporangium|sporangium]] (spore producing capsule), but each gametophyte can give rise to several sporophytes at once.

Liverworts, mosses and hornworts spend most of their lives as gametophytes. Gametangia (gamete-producing organs), [[Biology:Archegonium|archegonia]] and [[Biology:Antheridium|antheridia]], are produced on the gametophytes, sometimes at the tips of shoots, in the axils of leaves or hidden under thalli. Some bryophytes, such as the liverwort ''[[Biology:Marchantia|Marchantia]]'', create elaborate structures to bear the gametangia that are called gametangiophores. Sperm are flagellated and must swim from the antheridia that produce them to archegonia which may be on a different plant. Arthropods can assist in transfer of sperm.<ref name="Cronberg">{{Cite journal |last1=Cronberg |first1=N. |last2=Natcheva |first2=R. |last3=Hedlund |first3=K. |year=2006 |title=Microarthropods Mediate Sperm Transfer in Mosses |journal=Science |volume=313 |issue=5791 |page=1255 |doi=10.1126/science.1128707 |pmid=16946062 |s2cid=11555211}}</ref>

Fertilized eggs become zygotes, which develop into sporophyte embryos inside the archegonia. Mature sporophytes remain attached to the gametophyte. They consist of a stalk called a seta and a single sporangium or capsule. Inside the sporangium, haploid spores are produced by [[Biology:Meiosis|meiosis]]. These are dispersed, most commonly by wind, and if they land in a suitable environment can develop into a new gametophyte. Thus bryophytes disperse by a combination of swimming sperm and spores, in a manner similar to [[Biology:Lycophyte|lycophyte]]s, [[Biology:Fern|fern]]s and other cryptogams.

The sporophyte develops differently in the three groups. Both mosses and hornworts have a [[Biology:Meristem|meristem]] zone where cell division occurs. In hornworts, the meristem starts at the base where the foot ends, and the division of cells pushes the sporophyte body upwards. In mosses, the meristem is located between the capsule and the top of the stalk (seta), and produces cells downward, elongating the stalk and elevating the capsule. In liverworts the meristem is absent and the elongation of the sporophyte is caused almost exclusively by cell expansion.<ref>{{Cite book |last=Ueli Grossniklaus |url=https://books.google.com/books?id=romCDwAAQBAJ&dq=%22Schematic+representation+of+sporophyte+development+in+the+three+lineages+of+bryophytes%22&pg=PA13 |title=Plant Development and Evolution |date=2019 |publisher=Academic Press |isbn=9780128098059 |page=13}}</ref>


===Sexuality===
The arrangement of [[Biology:Antheridium|antheridia]] and [[Biology:Archegonium|archegonia]] on an individual bryophyte plant is usually constant within a species, although in some species it may depend on environmental conditions. The main division is between species in which the antheridia and archegonia occur on the same plant and those in which they occur on different plants. The term '''[[Biology:Monoicy|monoicous]]''' may be used where antheridia and archegonia occur on the same [[Biology:Gametophyte|gametophyte]] and the term '''[[Biology:Dioicy|dioicous]]''' where they occur on different gametophytes.<ref name=GlimBisa14/>

In [[Biology:Seed plant|seed plant]]s, "[[Biology:Plant reproductive morphology|monoecious]]" is used where flowers with anthers (microsporangia) and flowers with [[Biology:Ovule|ovule]]s (megasporangia) occur on the same [[Biology:Sporophyte|sporophyte]] and "[[Biology:Dioecy|dioecious]]" where they occur on different sporophytes. These terms occasionally may be used instead of "monoicous" and "dioicous" to describe bryophyte gametophytes. "Monoecious" and "monoicous" are both derived from the Greek for "one house", "dioecious" and "dioicous" from the Greek for two houses. The use of the "-oicy" terminology refers to the gametophyte sexuality of bryophytes as distinct from the sporophyte sexuality of seed plants.<ref name="GlimBisa14">{{Cite book |last1=Glime |first1=J.M. |url=http://www.bryoecol.mtu.edu |title=Bryophyte Ecology |last2=Bisang |first2=I. |date=2014 |publisher=Michigan Technological University and the International Association of Bryologists |editor-last=Glime |editor-first=J.M. |volume=1 Physiological Ecology |chapter=Sexuality: Its Determination (Ch. 3-1) |access-date=2014-11-09 |chapter-url=http://www.bryoecol.mtu.edu/chapters_VOL1/3-1Sexuality%20Its%20Determination.pdf |name-list-style=amp}}</ref>

Monoicous plants are necessarily hermaphroditic, meaning that the same plant produces gametes of both sexes.<ref name=GlimBisa14/> The exact arrangement of the antheridia and archegonia in monoicous plants varies. They may be borne on different shoots (autoicous), on the same shoot but not together in a common structure (paroicous or paroecious), or together in a common "inflorescence" (synoicous or synoecious).<ref name=GlimBisa14/><ref name="Wats81">{{Cite book |last=Watson |first=E.V. |title=British Mosses and Liverworts |date=1981 |publisher=Cambridge University Press |isbn=9780521285360 |edition=3rd |page=7}} (Watson uses the "oecy" terms rather than the "oicy" terms.)</ref> Dioicous plants are '''unisexual''', meaning that an individual plant has only one sex.<ref name=GlimBisa14/> All four patterns (autoicous, paroicous, synoicous and dioicous) occur in species of the moss genus ''[[Biology:Bryum|Bryum]]''.<ref name=Wats81/>

==Classification and phylogeny==
[[File:Hornwort (3144429129).jpg|thumb|Hornworts (Anthocerophyta) were once believed to be the closest living relatives of the vascular plants.]]
[[File:Bryophyte sp Moss 3.jpg|thumb|Mosses are one group of bryophytes.]]

Traditionally, all living land plants without vascular tissues were classified in a single taxonomic group, often a [[Biology:Phylum|division]] (or phylum). The term "Bryophyta" was first suggested by Braun in 1864.<ref>{{Cite web |title=Phylum Bryophyta – Hierarchy |url=http://taxonomicon.taxonomy.nl/TaxonTree.aspx?src=0&id=3593 |publisher=Taxonomicon}}</ref> As early as 1879, the term Bryophyta was used by German bryologist Wilhelm Schimper to describe a group containing all three bryophyte clades (though at the time, hornworts were considered part of the liverworts).<ref name= Sousa2019/><ref name=Schimp/> G.M. Smith placed this group between Algae and [[Biology:Pteridophyte|Pteridophyta]].<ref name="GMSmith">{{Cite book |last=Smith |first=G.M. |url=https://archive.org/details/cryptogamicbotan030182mbp |title=Cryptogamic Botany |date=1955 |publisher=McGraw-Hill |edition=2nd |volume=2 |location=New York}}</ref> Although a 2005 study supported this traditional monophyletic view,<ref>{{Cite journal |last1=Goremykin |first1=V. V. |last2=Hellwig |first2=F. H. |name-list-style=amp |year=2005 |title=Evidence for the most basal split in land plants dividing bryophyte and tracheophyte lineages |journal=Plant Systematics and Evolution |volume=254 |issue=1–2 |pages=93–103 |doi=10.1007/s00606-005-0337-1 |s2cid=41403901}}</ref> by 2010 a broad consensus had emerged among systematists that bryophytes as a whole are not a natural group (i.e., are paraphyletic).<ref name="Konrat">{{Cite journal |last1=Konrat |first1=M. |last2=Shaw |first2=A.J. |last3=Renzaglia |first3=K.S. |year=2010 |title=A special issue of ''Phytotaxa'' dedicated to Bryophytes: The closest living relatives of early land plants |journal=Phytotaxa |volume=9 |pages=5–10 |doi=10.11646/phytotaxa.9.1.3 |doi-access=free}}</ref><ref name="pmid18205621">{{Cite journal |last1=Troitsky |first1=A. V. |last2=Ignatov |first2=M. S. |last3=Bobrova |first3=V. K. |last4=Milyutina |first4=I. A. |date=December 2007 |title=Contribution of genosystematics to current concepts of phylogeny and classification of bryophytes |journal=Biochemistry (Moscow) |volume=72 |issue=12 |pages=1368–1376 |doi=10.1134/s0006297907120115 |pmid=18205621 |s2cid=13509400}}</ref><ref name="Knoop">{{Cite journal |last=Knoop |first=Volker |date=31 December 2010 |title=Looking for sense in the nonsense: a short review of non-coding organellar DNA elucidating the phylogeny of bryophytes |journal=Bryophyte Diversity and Evolution |volume=31 |issue=1 |pages=51–60 |doi=10.11646/bde.31.1.10}}</ref> However, a 2014 study concluded that these previous phylogenies, which were based on nucleic acid sequences, were subject to composition biases, and that, furthermore, phylogenies based on amino acid sequences suggested that the bryophytes are monophyletic after all.<ref name="CoxLiFostEmbl14" /> Since then, partially thanks to a proliferation of genomic and transcriptomic datasets, almost all phylogenetics studies based on nuclear and chloroplastic sequences have concluded that the bryophytes form a monophyletic group.<ref name="CoxLiFostEmbl14">{{Cite journal |last=Cox |first=Cymon J. |display-authors=0 |year=2014 |title=Conflicting Phylogenies for Early Land Plants are Caused by Composition Biases among Synonymous Substitutions |journal=Systematic Biology |volume=63 |issue=2 |pages=272–279 |doi=10.1093/sysbio/syt109 |pmc=3926305 |pmid=24399481}}</ref><ref name="Puttick2018">{{Cite journal |last=Puttick |first=Mark N. |display-authors=0 |year=2018 |title=The Interrelationships of Land Plants and the Nature of the Ancestral Embryophyte |journal=Current Biology |volume=28 |issue=5 |pages=733–745.e2 |doi=10.1016/j.cub.2018.01.063 |pmid=29456145 |hdl-access=free |s2cid=3269165 |hdl=1983/ad32d4da-6cb3-4ed6-add2-2415f81b46da}}</ref><ref name="Sousa2019">{{Cite journal |last=de Sousa |first=Filipe |display-authors=0 |year=2019 |title=Nuclear protein phylogenies support the monophyly of the three bryophyte groups (Bryophyta Schimp.) |journal=New Phytologist |volume=222 |issue=1 |pages=565–575 |doi=10.1111/nph.15587 |pmid=30411803 |hdl-access=free |hdl=1983/0b471d7e-ce54-4681-b791-1da305d9e53b |s2cid=53240320}}</ref><ref name="LeebensMack2019">{{Cite journal |last=Leebens-Mack |first=James H. |display-authors=0 |year=2019 |title=One thousand plant transcriptomes and the phylogenomics of green plants |journal=Nature |volume=574 |issue=7780 |pages=679–685 |doi=10.1038/s41586-019-1693-2 |pmc=6872490 |pmid=31645766}}</ref><ref name="Zhang2020">{{Cite journal |last=Zhang |first=Jian |display-authors=0 |year=2020 |title=The hornwort genome and early land plant evolution |journal=Nature Plants |volume=6 |issue=2 |pages=107–118 |doi=10.1038/s41477-019-0588-4 |pmc=7027989 |pmid=32042158}}</ref><ref name="Harris2020">{{Cite journal |last=Harris |first=Brogan J. |display-authors=0 |year=2020 |title=Phylogenomic Evidence for the Monophyly of Bryophytes and the Reductive Evolution of Stomata |journal=Current Biology |volume=30 |issue=11 |pages=P2201–2012.E2 |doi=10.1016/j.cub.2020.03.048 |pmid=32302587 |hdl-access=free |hdl=1983/fbf3f371-8085-4e76-9342-e3b326e69edd |s2cid=215798377}}</ref><ref name="Li2020">{{Cite journal |last=Li |first=Fay-Wei |display-authors=0 |year=2020 |title=Anthoceros genomes illuminate the origin of land plants and the unique biology of hornworts |journal=Nature Plants |volume=6 |issue=3 |pages=259–272 |doi=10.1038/s41477-020-0618-2 |pmc=8075897 |pmid=32170292 |hdl-access=free |hdl=10261/234303}}</ref><ref name="Sousa2020a">{{Cite journal |last=Sousa |first=Filipe |display-authors=0 |year=2020 |title=The Chloroplast Land Plant Phylogeny: Analyses Employing Better-Fitting Tree- and Site-Heterogeneous Composition Models |journal=Frontiers in Plant Science |volume=11 |page=1062 |doi=10.3389/fpls.2020.01062 |pmc=7373204 |pmid=32760416 |doi-access=free}}</ref><ref name="Su2021">{{Cite journal |last=Su |first=Danyan |display-authors=0 |year=2021 |title=Large-Scale Phylogenomic Analyses Reveal the Monophyly of Bryophytes and Neoproterozoic Origin of Land Plants |journal=Molecular Biology and Evolution |volume=38 |issue=8 |pages=3332–3344 |doi=10.1093/molbev/msab106 |pmc=8321542 |pmid=33871608}}</ref> Nevertheless, phylogenies based on mitochondrial sequences fail to support the monophyletic view.<ref name="Sousa2020b">{{Cite journal |last=Sousa |first=Filipe |display-authors=0 |year=2020 |title=The mitochondrial phylogeny of land plants shows support for Setaphyta under composition-heterogeneous substitution models |journal=PeerJ |volume=8 |issue=4 |page=e8995 |doi=10.7717/peerj.8995 |pmc=7194085 |pmid=32377448 |doi-access=free }}</ref>

The three bryophyte [[Biology:Clade|clade]]s are the [[Biology:Marchantiophyta|Marchantiophyta]] (liverworts), [[Biology:Moss|Bryophyta]] (mosses) and [[Biology:Anthocerotophyta|Anthocerotophyta]] (hornworts).<ref name="glossary">{{Cite web |title=GLOSSARY B |url=http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookglossB.html |url-status=dead |archive-url=https://web.archive.org/web/20090402235253/http://www.emc.maricopa.edu/faculty/farabee/biobk/BioBookglossB.html |archive-date=2009-04-02 |access-date=2009-03-26}}</ref> However, it has been proposed that these clades are de-ranked to the classes Marchantiopsida, Bryopsida, and Anthocerotopsida, respectively.<ref name="Sousa2019" /> There is now strong evidence that the liverworts and mosses belong to a monophyletic clade, called [[Biology:Setaphyta|Setaphyta]].<ref name="Puttick2018" /><ref name=Sousa2020b/><ref name="Cox2018">{{Cite journal |last=Cox |first=Cymon J. |year=2018 |title=Land Plant Molecular Phylogenetics: A Review with Comments on Evaluating Incongruence Among Phylogenies |journal=Critical Reviews in Plant Sciences |volume=37 |issue=2–3 |pages=113–127 |doi=10.1080/07352689.2018.1482443 |hdl-access=free |hdl=10400.1/14557 |s2cid=92198979}}</ref>

===Monophyletic view===
The favored model, based on amino acids phylogenies, indicates bryophytes as a monophyletic group:<ref name=CoxLiFostEmbl14/>

{{Clade|style=line-height:100%;
|label1=[[Biology:Embryophyte|embryophyte]]s
|1={{Clade
   |label1=bryophytes
   |1={{clade
      |label1=[[Biology:Setaphyta|setaphyte]]s     
      |1={{clade
         |1=liverworts
         |2=[[Biology:Moss|moss]]es}}
     |2=[[Biology:Hornwort|hornwort]]s
         }}
   |2=[[Biology:Vascular plant|vascular plant]]s
   }}
}}

Consistent with this view, compared to other living land plants, all three lineages lack vascular tissue containing lignin and branched sporophytes bearing multiple sporangia. The prominence of the gametophyte in the life cycle is also a shared feature of the three bryophyte lineages (extant vascular plants are all sporophyte dominant). However, if this phylogeny is correct, then the complex sporophyte of living vascular plants might have evolved independently of the simpler unbranched sporophyte present in bryophytes.<ref name=CoxLiFostEmbl14/> Furthermore, this view implies that stomata evolved only once in plant evolution, before being subsequently lost in the liverworts.<ref name=Puttick2018/><ref name=Harris2020/>

===Paraphyletic view===
{{Barlabel
|size=4
|at1=2|bar1=green|label1=bryophytes
|cladogram=
{{Clade
|label1=embryophytes
|1={{Cladex
   |label1=[[Biology:Setaphyta|setaphytes]]
   |1={{Cladex
       |1=[[Biology:Liverworts|liverworts]]|barbegin1=green
       |2=mosses|bar2=green   }}   
   |2={{Cladex
       |1=hornworts|barend1=green
       |2=vascular plants
         }}
      }}
   }}
}}

[[File:Thallose liverwort (Marchantia and Lunularia spp.) showing clonal plantlets in gemma cups.jpg|thumb|Liverworts are included in the bryophyte group]]
In this alternative view, the Setaphyta grouping is retained, but hornworts instead are sister to vascular plants.<ref name="Cox2018" /> (Another paraphyletic view involves hornworts branching out first.)<ref name=Sousa2020b/>

===Traditional morphology{{anchor|Taxonomy}}===
Traditionally, when basing classifications on morphological characters, bryophytes have been distinguished by their lack of vascular structure. However, this distinction is problematic, firstly because some of the earliest-diverging (but now extinct) non-bryophytes, such as the horneophytes, did not have true vascular tissue, and secondly because many mosses have well-developed water-conducting vessels.<ref name="Bell">{{Cite journal |last1=Bell |first1=N. E. |last2=Hyvönen |first2=J. |name-list-style=amp |year=2010 |title=Phylogeny of the moss class Polytrichopsida (BRYOPHYTA): Generic-level structure and incongruent gene trees |url=https://zenodo.org/record/1065524 |journal=Molecular Phylogenetics and Evolution |volume=55 |issue=2 |pages=381–398 |doi=10.1016/j.ympev.2010.02.004 |pmid=20152915}}</ref><ref name="Bodribbetal">{{Cite journal |last=Bodribb |first=T.J. |display-authors=0 |year=2020 |title=Advanced vascular function discovered in a widespread moss |journal=Nature Plants |volume=6 |issue=3 |pages=273–279 |doi=10.1038/s41477-020-0602-x |pmid=32170283 |s2cid=212641738}}</ref> A more useful distinction may lie in the structure of their [[Biology:Sporophyte|sporophyte]]s. In bryophytes, the sporophyte is a simple unbranched structure with a single spore-forming organ ([[Biology:Sporangium|sporangium]]), whereas in all other land plants, the [[Biology:Polysporangiophyte|polysporangiophyte]]s, the sporophyte is branched and carries many sporangia.<ref name="Kenrick1997a">{{Cite book |last1=Kenrick |first1=Paul |title=The Origin and Early Diversification of Land Plants: A Cladistic Study |last2=Crane |first2=Peter R. |publisher=Smithsonian Institution Press |year=1997a |isbn=978-1-56098-730-7 |location=Washington, D.C. |name-list-style=amp}}</ref><ref name="Kenrick1997b">{{Cite journal |last1=Kenrick |first1=P. |last2=Crane |first2=P.R. |name-list-style=amp |year=1997b |title=The origin and early evolution of plants on land |journal=Nature |volume=389 |issue=6646 |pages=33–39 |bibcode=1997Natur.389...33K |doi=10.1038/37918 |s2cid=3866183}}</ref> The contrast is shown in the cladogram below:<ref name="Crane2004">{{Cite journal |last1=Crane |first1=Peter R. |last2=Herendeen |first2=Patrick |last3=Friis |first3=Else Marie |date=October 2004 |title=Fossils and plant phylogeny |journal=American Journal of Botany |volume=91 |issue=10 |pages=1683–1699 |doi=10.3732/ajb.91.10.1683 |pmid=21652317 |doi-access=free}}</ref>

{{clade|style=line-height:100%;
|label1=land&nbsp;plants
|1={{clade
|1=bryophytes
|2={{clade
|label1=polysporangiophytes
|1={{clade
  |1="protracheophytes", such as ''[[Biology:Horneophyton|Horneophyton]]'' or ''[[Biology:Aglaophyton|Aglaophyton]]''
  |2=tracheophytes or vascular plants
}}
}}
}}
}}

==Evolution==
There have probably been several different terrestrialization events, in which originally aquatic organisms colonized the land, just within the lineage of the [[Viridiplantae]].<ref name="Gerrienne">{{Cite journal |last1=Gerrienne |first1=Philippe |last2=Servais |first2=Thomas |last3=Vecoli |first3=Marco |date=April 2016 |title=Plant evolution and terrestrialization during Palaeozoic times—The phylogenetic context |journal=Review of Palaeobotany and Palynology |volume=227 |pages=4–18 |doi=10.1016/j.revpalbo.2016.01.004}}</ref> Between 510–630 million years ago, however, land plants emerged within the [[Biology:Green algae|green algae]].<ref>{{Cite journal |last1=Delwiche |first1=Charles F. |last2=Timme |first2=Ruth E. |date=2011-06-07 |title=Plants |journal=Current Biology |volume=21 |issue=11 |pages=R417–R422 |doi=10.1016/j.cub.2011.04.021 |issn=0960-9822 |pmid=21640897 |s2cid=235312105|doi-access=free }}</ref> Molecular phylogenetic studies conclude that bryophytes are the earliest diverging lineages of the extant land plants.<ref name="Konrat2">{{Cite journal |last1=Konrat |first1=M. |last2=Shaw |first2=A.J. |last3=Renzaglia |first3=K.S. |year=2010 |title=A special issue of ''Phytotaxa'' dedicated to Bryophytes: The closest living relatives of early land plants |journal=Phytotaxa |volume=9 |pages=5–10 |doi=10.11646/phytotaxa.9.1.3 |doi-access=free}}</ref><ref name=pmid12415314/><ref name="KaroArumBoorDuff102">{{Cite journal |last1=Karol |first1=Kenneth G. |last2=Arumuganathan |first2=Kathiravetpillai |last3=Boore |first3=Jeffrey L. |last4=Duffy |first4=Aaron M. |last5=Everett |first5=Karin DE |last6=Hall |first6=John D. |last7=Hansen |first7=S.K. |last8=Kuehl |first8=Jennifer V. |last9=Mandoli |first9=Dina F. |last10=Mishler |first10=Brent D. |last11=Olmstead |first11=Richard G. |name-list-style=amp |year=2010 |title=Complete plastome sequences of Equisetum arvense and Isoetes flaccida: implications for phylogeny and plastid genome evolution of early land plant lineages |journal=BMC Evolutionary Biology |volume=10 |issue=1 |page=321 |doi=10.1186/1471-2148-10-321 |pmc=3087542 |pmid=20969798 |last12=Renzaglia |first12=Karen S. |last13=Wolf |first13=Paul G. |doi-access=free }}</ref><ref name="Shaw">{{Cite journal |last1=Shaw |first1=A. Jonathan |last2=Szövényi |first2=Péter |last3=Shaw |first3=Blanka |date=March 2011 |title=Bryophyte diversity and evolution: Windows into the early evolution of land plants |journal=American Journal of Botany |volume=98 |issue=3 |pages=352–369 |doi=10.3732/ajb.1000316 |pmid=21613131}}</ref> They provide insights into the migration of plants from aquatic environments to land. A number of physical features link bryophytes to both land plants and aquatic plants.<ref>{{Cite journal |last1=Donoghue |first1=Philip C. J. |last2=Harrison |first2=C. Jill |last3=Paps |first3=Jordi |last4=Schneider |first4=Harald |date=11 October 2021 |title=The evolutionary emergence of land plants |url=https://research-information.bris.ac.uk/en/publications/the-evolutionary-emergence-of-land-plants |journal=Current Biology |volume=31 |issue=19 |pages=R1281–R1298 |doi=10.1016/j.cub.2021.07.038 |pmid=34637740 |hdl=1983/662d176e-fcf4-40bf-aa8c-5694a86bd41d |s2cid=238588736|doi-access=free |hdl-access=free }}</ref>

=== Similarities to algae and vascular plants ===

Green algae, bryophytes and vascular plants all have chlorophyll a and b, and the chloroplast structures are similar.<ref name="Evert" /> Like green algae and land plants, bryophytes also produce starch stored in the plastids and contain cellulose in their walls.<ref name="Evert" /> Distinct adaptations observed in bryophytes have allowed plants to colonize Earth's terrestrial environments. To prevent desiccation of plant tissues in a terrestrial environment, a waxy cuticle covering the soft tissue of the plant may be present, providing protection. In hornworts and mosses, stomata provide gas exchange between the atmosphere and an internal intercellular space system. The development of gametangia provided further protection specifically for gametes, the zygote and the developing sporophyte.<ref name="Bryophytes">{{Cite web |last=Purcell |first=Adam |title=Bryophytes |url=http://basicbiology.net/plants/lycophytes/bryophytes.php |website=Basic Biology}}</ref> The bryophytes and vascular plants ([[Biology:Embryophyte|embryophyte]]s) also have embryonic development which is not seen in green algae.<ref name="Evert" /> While bryophytes have no truly vascularized tissue, they do have organs that are specialized for transport of water and other specific functions, analogous for example to the functions of leaves and stems in vascular land plants.<ref name="Evert">{{Cite book |last1=Evert |first1=Ray |title=Biology of Plants |last2=Eichhorn |first2=Susan |publisher=W.H.Freeman and Company Publishers |year=2013}}</ref>

Bryophytes depend on water for reproduction and survival. In common with ferns and [[Biology:Lycopodiopsida|lycophytes]], a thin layer of water is required on the surface of the plant to enable the movement of the flagellated sperm between gametophytes and the fertilization of an egg.<ref name="Bryophytes" />

==Comparative morphology==
Summary of the morphological characteristics of the [[Biology:Gametophyte|gametophyte]]s of the three groups of bryophytes:
{| class="wikitable"
|-
! 
! Liverworts
! Mosses
! Hornworts
|-
!scope=row| Structure
| Thalloid or foliose
| Foliose
| Thalloid
|-
!scope=row| Symmetry
| [[Biology:Dorsiventral|Dorsiventral]] or [[Biology:Symmetry in biology#Radial symmetry|radial]]
| Radial
| Dorsiventral
|-
!scope=row| Rhizoids
| Unicellular
| Pluricellular
| Unicellular
|-
!scope=row| Chloroplasts/cell
| Many
| Many
| One
|-
!scope=row| [[Biology:Protonema|Protonema]]ta
| Reduced
| Present
| Absent
|-
!scope=row| Gametangia<br>(antheridia<br>and archegonia)
| Superficial
| Superficial
| Immersed
|}

Summary of the morphological characteristics of the [[Biology:Sporophyte|sporophyte]]s of the three groups of bryophytes:

{| class="wikitable"
|-
! 
! Liverworts
! Mosses
! Hornworts
|-
!scope=row| Stomata
| Absent
| Present
| Present
|-
!scope=row| Structure
| Small, without chlorophyll
| Large, with chlorophyll
| Large, with chlorophyll
|-
!scope=row| Persistence
| Ephemeral
| Persistent
| Persistent
|-
!scope=row| Growth
| Defined
| Defined
| Continuous
|-
!scope=row|Apical growth<ref>[https://academic.oup.com/plphys/article/190/1/100/6623418?login=false How was apical growth regulated in the ancestral land plant? Insights from the development of non-seed plants]</ref>
|Absent
|Present
|Absent
|-
!scope=row| [[Biology:Seta|Seta]]
| Present
| Present
| Absent
|-
!scope=row| Capsule form
| Simple
| Differentiated<br>([[Biology:Operculum (botany)|operculum]], [[Biology:Peristome|peristome]])
| Elongated
|-
!scope=row| Maturation of spores
| Simultaneous
| Simultaneous
| Gradual
|-
!scope=row| Dispersion of spores
| [[Biology:Elater|Elater]]s
| Peristome teeth
| Pseudo-elaters
|-
!scope=row| [[Biology:Columella (botany)|Columella]]
| Absent
| Present
| Present
|-
!scope=row| [[Biology:Dehiscence (botany)|Dehiscence]] 
| Longitudinal or irregular
| Transverse
| Longitudinal 
|}

== Uses ==
{{prose|date=April 2017}}

'''Environmental'''
* Soil Conditioning
* Bioindicators
* Moss gardens 
* Pesticides 
Characteristics of bryophytes make them useful to the environment. Depending on the specific plant texture, bryophytes have been shown to help improve the water retention and air space within soil.<ref name="Glime">{{Cite web |last=Glime |first=Janice |title=Economic and Ethnic Uses of Bryophytes |url=http://flora.huh.harvard.edu/FloraData/001/WebFiles/fna27/FNA27-Chapter2.pdf |website=harvard.edu}}</ref> Bryophytes are used in pollution studies to indicate soil pollution (such as the presence of heavy metals), air pollution, and UV-B radiation.<ref name="Glime" /> Gardens in Japan are designed with moss to create peaceful sanctuaries.<ref name="Glime" /> Some bryophytes have been found to produce natural pesticides. The liverwort, ''Plagiochila,'' produces a chemical that is poisonous to mice.<ref name="Glime" /> Other bryophytes produce chemicals that are antifeedants which protect them from being eaten by slugs.<ref name="Glime" /> When ''Phythium sphagnum'' is sprinkled on the soil of germinating seeds, it inhibits growth of "damping off fungus" which would otherwise kill young seedlings.<ref name="Wolffhechel">{{Cite journal |last=Wolffhechel |first=H. |date=April 1988 |title=The suppressiveness of sphagnum peat to ''Pythium'' spp |journal=Acta Horticulturae |issue=221 |pages=217–222 |doi=10.17660/actahortic.1988.221.22}}</ref>
[[File:Schultz Sphagnum Peat Moss.jpg|thumb|Moss peat is made from ''Sphagnum'']]
'''Commercial'''
* Fuel
* Packaging
* Wound Dressing
[[Earth:Peat|Peat]] is a fuel produced from dried bryophytes, typically ''[[Biology:Sphagnum|Sphagnum]].'' Bryophytes' antibiotic properties and ability to retain water make them a useful packaging material for vegetables, flowers, and bulbs.<ref name="Glime" /> Also, because of its antibiotic properties, ''[[Biology:Sphagnum|Sphagnum]]'' was used as a surgical dressing in World War I.<ref name="Glime" />

== See also ==
* Plant sexuality
* List of British county and local bryophyte floras
* Thallophyta

== References ==
{{reflist|2}}

==Bibliography==
* {{Cite journal |last1=Lesica |first1=P. |last2=McCune |first2=B. |last3=Cooper |first3=S. V. |last4=Hong |first4=W. S. |year=1991 |title=Differences in lichen and bryophyte communities between old-growth and managed second-growth forests in the Swan Valley, Montana |journal=Canadian Journal of Botany |volume=69 |issue=8 |pages=1745–1755 |doi=10.1139/b91-222}}

== External links ==

* [http://www.andrewspink.nl/mosses/ Andrew's Moss Site] Photos of bryophytes
*27-May-2013 [https://www.bbc.co.uk/news/science-environment-22656239 ''Centuries-old frozen plants revived''], 400-year-old bryophyte specimens left behind by [[Earth:Retreat of glaciers since 1850|retreating glaciers]] in Canada are brought back to life in the laboratory.
*{{Cite journal |last1=Farge |first1=Catherine La |last2=Williams |first2=Krista H. |last3=England |first3=John H. |date=22 May 2013 |title=Regeneration of Little Ice Age bryophytes emerging from a polar glacier with implications of totipotency in extreme environments |journal=Proceedings of the National Academy of Sciences |volume=110 |issue=24 |pages=9839–9844 |bibcode=2013PNAS..110.9839L |doi=10.1073/pnas.1304199110 |pmc=3683725 |pmid=23716658 |doi-access=free}}
* Magill, R. E., ed. (1990). ''Glossarium polyglottum bryologiae. A multilingual glossary for bryology''. Monographs in Systematic Botany from the Missouri Botanical Garden, v. 33, 297 pp. [https://web.archive.org/web/20041209031512/http://www.mobot.org/MOBOT/tropicos/most/Glossary/glosefr.html Online version: Internet Archive].

{{Botany}}
{{Plant classification}}


[[Category:Bryophytes| ]]
[[Category:Cryptogams]]
[[Category:Paraphyletic groups]]

{{Sourceattribution|Bryophyte}}