Bryophytes are a proposed taxonomic division containing three groups of non-vascular land plants (embryophytes): the liverworts, hornworts and mosses. They are characteristically limited in size and prefer moist habitats although they can survive in drier environments. The bryophytes consist of about 20,000 plant species. Bryophytes produce enclosed reproductive structures (gametangia and sporangia), but they do not produce flowers or seeds. They reproduce by spore formation . Though bryophytes were considered a paraphyletic group in recent years, almost all of the most recent phylogenetic evidence supports the monophyly of this group, as originally classified by Wilhelm Schimper in 1879. The term "bryophyte" comes from Greek βρύον, bryon "tree-moss, oyster-green" and φυτόν, phyton "plant".
The defining features of bryophytes are:
- Their life cycles are dominated by a multicellular gametophyte stage
- Their sporophytes are unbranched
- They do not have a true vascular tissue containing lignin (although some have specialized tissues for the transport of water)
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 rainforests). Bryophytes can grow where vascularized plants cannot because they do not depend on roots for uptake of nutrients from soil. Bryophytes can survive on rocks and bare soil.
Like all land plants (embryophytes), bryophytes have life cycles with alternation of generations. In each cycle, a haploid gametophyte, each of whose cells contains a fixed number of unpaired chromosomes, alternates with a diploid sporophyte, whose cell 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 meiosis, that grow into gametophytes.
Bryophytes are gametophyte dominant, 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. In bryophytes, the sporophytes are always unbranched and produce a single sporangium (spore producing capsule), but each gametophyte can give rise to several sporophytes at once.
The sporophyte develops differently in the three groups. Both mosses and hornworts have a meristem zone where cell division occur. In hornworts, the meristem starts at the base where the foot ends, and the division of cells is pushing the sporophyte body upwards. In mosses, the meristem is located between the capsule and the top of the stalk (seta), and produce cells downward, elongating the stalk and elevates the capsule. In liverworts the meristem is absent and the elongation of the sporophyte is caused almost exclusively by cell expansion.
Liverworts, mosses and hornworts spend most of their lives as gametophytes. Gametangia (gamete-producing organs), archegonia and 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 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.
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 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 lycophytes, ferns and other cryptogams.
The arrangement of antheridia and 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 monoicous may be used where antheridia and archegonia occur on the same gametophyte and the term dioicous where they occur on different gametophytes.
In seed plants, "monoecious" is used where flowers with anthers (microsporangia) and flowers with ovules (megasporangia) occur on the same sporophyte and "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.
Monoicous plants are necessarily hermaphroditic, meaning that the same plant has both sexes. The exact arrangement of the antheridia and archegonia in monoicous plants varies. They may be borne on different shoots (autoicous or autoecious), on the same shoot but not together in a common structure (paroicous or paroecious), or together in a common "inflorescence" (synoicous or synoecious). Dioicous plants are unisexual, meaning that the same plant has only one sex. All four patterns (autoicous, paroicous, synoicous and dioicous) occur in species of the moss genus Bryum.
Classification and phylogeny
Traditionally, all living land plants without vascular tissues were classified in a single taxonomic group, often a division (or phylum). 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). Although a 2005 study supported this traditional monophyletic view, by 2010 a broad consensus had emerged among systematists that bryophytes as a whole are not a natural group (i.e., are paraphyletic). 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. 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. Nevertheless, phylogenies based on mitochondrial sequences fail to support the monophyletic view.
The three bryophyte clades are the Marchantiophyta (liverworts), Bryophyta (mosses) and Anthocerotophyta (hornworts).. However, it has been proposed that these clades are de-ranked to the classes Marchantiopsida, Bryopsida, and Anthocerotopsida, respectively. There is now strong evidence that the liverworts and mosses belong to a monophyletic clade, called Setaphyta.
The favoured model, based on amino acids phylogenies, indicates bryophytes as a monophyletic group:
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. Furthermore, this view implies that stomata evolved only once in plant evolution, before being subsequently lost in the liverworts.
In this alternative view, the Setaphyta grouping is retained, but hornworts instead are sister to vascular plants. Further evidence may be required to fully reject this hypothesis.
Traditionally, when basing classifications on morphological characters, bryophytes have been disinguished 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. A more useful distinction may lie in the structure of their sporophytes. In bryophytes, the sporophyte is a simple unbranched structure with a single spore-forming organ (sporangium), whereas in all other land plants, the polysporangiophytes, the sporophyte is branched and carries many sporangia. The contrast is shown in the cladogram below:
There have probably been several different terrestrialization events, in which originally aquatic organisms colonized the land, just within the lineage of the Viridiplantae. Between 510 - 630 million years ago, however, land plants evolved from aquatic plants, specifically green algae. Molecular phylogenetic studies conclude that bryophytes are the earliest diverging lineages of the extant land plants. 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.
Similarities to algae and vascular plants
Green algae, bryophytes and vascular plants all have chlorophyll a and b, and the chloroplast structures are similar. Like green algae and land plants, bryophytes also produce starch stored in the plastids and contain cellulose in their walls. 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. The bryophytes and vascular plants (embryophytes) also have embryonic development which is not seen in green algae. While bryophytes have no truly vascularized tissue, they do have organs that are specialized for specific functions, analogous for example to the functions of leaves and stems in vascular land plants.
Bryophytes depend on water for reproduction and survival. In common with ferns and 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.
Summary of the morphological characteristics of the gametophytes of the three groups of bryophytes:
|Structure||Thalloid or foliose||Foliose||Thalloid|
|Symmetry||Dorsiventral or radial||Radial||Dorsiventral|
Summary of the morphological characteristics of the sporophytes of the three groups of bryophytes:
|Structure||Small, without chlorophyll||Large, with chlorophyll||Large, with chlorophyll|
|Maturation of spores||Simultaneous||Simultaneous||Graduate|
|Dispersion of spores||Elaters||Peristome teeth||Pseudo-elaters|
|Dehiscence||Longitudinal or irregular||Transverse||Longitudinal|
- Soil Conditioning
- Moss gardens
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. Bryophytes are used in pollution studies to indicate soil pollution (such as the presence of heavy metals), air pollution, and UV-B radiation. Gardens in Japan are designed with moss to create peaceful sanctuaries. Some bryophytes have been found to produce natural pesticides. The liverwort, Plagiochila, produces a chemical that is poisonous to mice. Other bryophytes produce chemicals that are antifeedants which protect them from being eaten by slugs. When Phythium sphagnum is sprinkled on the soil of germinating seeds, it inhibits growth of "damping off fungus" which would otherwise kill young seedlings.
- Wound Dressing
Peat is a fuel produced from dried bryophytes, typically Sphagnum. Bryophytes' antibiotic properties and ability to retain water make them a useful packaging material for vegetables, flowers, and bulbs. Also, because of its antibiotic properties, Sphagnum was used as a surgical dressing in World War I.
- Anthocerotophyta (hornworts)
- Bryophyta (mosses)
- Marchantiophyta (liverworts)
- Plant sexuality
- List of British county and local bryophyte floras
- Hedges, S. Blair (November 2002). "The origin and evolution of model organisms". Nature Reviews Genetics. 3 (11): 838–849. doi:10.1038/nrg929. PMID 12415314. S2CID 10956647.
- Levetin, Estelle; McMahon, Karen (2012). Plants and Society. New York, NY: McGraw-Hill. p. 139. ISBN 978-0-07-352422-1.
- "Bryophytes (Mosses and liverworts) — The Plant List". www.theplantlist.org. Retrieved 2017-04-11.
- "What are Bryophytes". Southern Illinois University Carbondale.
- Vanderpoorten, Alain; Goffinet, Bernard (2009). Introduction to Bryophytes. Cambridge: Cambridge University Press. p. 3. ISBN 978-0-511-54013-4.
- Schimper, W.P. (1879). "Bryophyta". In Zittel, K.A. (ed.). Handbuch der Palaeontologie. 2. R. Oldenbourg.
- Smith, G.M. (1955). Cryptogamic Botany. 2 (2nd ed.). New York: McGraw-Hill.
- Lucas, William J.; Groover, Andrew; Lichtenberger, Raffael; Furuta, Kaori; Yadav, Shri-Ram; Helariutta, Ykä; He, Xin-Qiang; Fukuda, Hiroo; Kang, Julie; Brady, Siobhan M.; Patrick, John W. (April 2013). "The Plant Vascular System: Evolution, Development and Functions F". Journal of Integrative Plant Biology. 55 (4): 294–388. doi:10.1111/jipb.12041. hdl:10261/76903. PMID 23462277.
- "Habitats - ecology - bryophyte". www.anbg.gov.au. Retrieved 2017-04-12.
- Ligrone, Roberto; Duckett, Jeffrey G.; Renzaglia, Karen S. (April 2012). "Major transitions in the evolution of early land plants: a bryological perspective". Annals of Botany. 109 (5): 851–871. doi:10.1093/aob/mcs017. PMC 3310499. PMID 22356739.
- CM Sean Carrington (2013-11-04). "Bryophytes". Retrieved 2020-03-05.
- Johnson, M G; Shaw, A J (24 February 2016). "The effects of quantitative fecundity in the haploid stage on reproductive success and diploid fitness in the aquatic peat moss Sphagnum macrophyllum". Heredity. 116 (6): 523–530. doi:10.1038/hdy.2016.13. PMC 4868265. PMID 26905464.
- Plant Development and Evolution
- Cronberg, N.; Natcheva, R.; Hedlund, K. (2006). "Microarthropods Mediate Sperm Transfer in Mosses". Science. 313 (5791): 1255. doi:10.1126/science.1128707. PMID 16946062. S2CID 11555211.
- Glime, J.M. & Bisang, I. (2014). "Sexuality: Its Determination (Ch. 3-1)" (PDF). In Glime, J.M. (ed.). Bryophyte Ecology. Volume 1 Physiological Ecology. Michigan Technological University and the International Association of Bryologists. Retrieved 2014-11-09.
|volume=has extra text (help)
- Watson, E.V. (1981). British Mosses and Liverworts (3rd ed.). Cambridge University Press. p. 7. (Watson uses the "oecy" terms rather than the "oicy" terms.)
- de Sousa, Filipe; et al. (2019). "Nuclear protein phylogenies support the monophyly of the three bryophyte groups (Bryophyta Schimp.)". New Phytologist. 222 (1): 565–575. doi:10.1111/nph.15587. hdl:1983/0b471d7e-ce54-4681-b791-1da305d9e53b. PMID 30411803.
- Goremykin, V. V. & Hellwig, F. H. (2005). "Evidence for the most basal split in land plants dividing bryophyte and tracheophyte lineages". Plant Systematics and Evolution. 254 (1–2): 93–103. doi:10.1007/s00606-005-0337-1. S2CID 41403901.
- Konrat, M.; Shaw, A.J.; Renzaglia, K.S. (2010). "A special issue of Phytotaxa dedicated to Bryophytes: The closest living relatives of early land plants". Phytotaxa. 9: 5–10. doi:10.11646/phytotaxa.9.1.3.
- Troitsky, A. V.; Ignatov, M. S.; Bobrova, V. K.; Milyutina, I. A. (December 2007). "Contribution of genosystematics to current concepts of phylogeny and classification of bryophytes". Biochemistry (Moscow). 72 (12): 1368–1376. doi:10.1134/s0006297907120115. PMID 18205621. S2CID 13509400.
- Knoop, Volker (31 December 2010). "Looking for sense in the nonsense: a short review of non-coding organellar DNA elucidating the phylogeny of bryophytes". Bryophyte Diversity and Evolution. 31 (1): 51–60. doi:10.11646/bde.31.1.10.
- Cox, Cymon J.; et al. (2014). "Conflicting Phylogenies for Early Land Plants are Caused by Composition Biases among Synonymous Substitutions". Systematic Biology. 63 (2): 272–279. doi:10.1093/sysbio/syt109. PMC 3926305. PMID 24399481.
- Puttick, Mark N.; et al. (2018). "The Interrelationships of Land Plants and the Nature of the Ancestral Embryophyte". Current Biology. 28 (5): 733–745.e2. doi:10.1016/j.cub.2018.01.063. hdl:1983/ad32d4da-6cb3-4ed6-add2-2415f81b46da. PMID 29456145. S2CID 3269165.
- Leebens-Mack, James H.; et al. (2019). "One thousand plant transcriptomes and the phylogenomics of green plants". Nature. 574 (7780): 679–685. doi:10.1038/s41586-019-1693-2. PMC 6872490. PMID 31645766.
- Zhang, Jian; et al. (2020). "The hornwort genome and early land plant evolution". Nature Plants. 6 (2): 107–118. doi:10.1038/s41477-019-0588-4. PMC 7027989. PMID 32042158.
- Harris, Brogan J.; et al. (2020). "Phylogenomic Evidence for the Monophyly of Bryophytes and the Reductive Evolution of Stomata". Current Biology. 30 (11): P2201–2012.E2. doi:10.1016/j.cub.2020.03.048. hdl:1983/fbf3f371-8085-4e76-9342-e3b326e69edd. PMID 32302587. S2CID 215798377.
- Li, Fay-Wei; et al. (2020). "Anthoceros genomes illuminate the origin of land plants and the unique biology of hornworts". Nature Plants. 6 (3): 259–272. doi:10.1038/s41477-020-0618-2. hdl:10261/234303. PMC 8075897. PMID 32170292.
- Sousa, Filipe; et al. (2020). "The Chloroplast Land Plant Phylogeny: Analyses Employing Better-Fitting Tree- and Site-Heterogeneous Composition Models". Frontiers in Plant Science. 11: 1062. doi:10.3389/fpls.2020.01062. PMC 7373204. PMID 32760416.
- Su, Danyan; et al. (2021). "Large-Scale Phylogenomic Analyses Reveal the Monophyly of Bryophytes and Neoproterozoic Origin of Land Plants". Molecular Biology and Evolution. 38 (8): 3332–3344. doi:10.1093/molbev/msab106. PMC 8321542. PMID 33871608.
- Sousa, Filipe; et al. (2020). "The mitochondrial phylogeny of land plants shows support for Setaphyta under composition-heterogeneous substitution models". PeerJ. 8 (4): e8995. doi:10.7717/peerj.8995. PMC 7194085. PMID 32377448.
- "GLOSSARY B". Archived from the original on 2009-04-02. Retrieved 2009-03-26.
- Cox, Cymon J. (2018). "Land Plant Molecular Phylogenetics: A Review with Comments on Evaluating Incongruence Among Phylogenies". Critical Reviews in Plant Sciences. 37 (2–3): 113–127. doi:10.1080/07352689.2018.1482443. hdl:10400.1/14557. S2CID 92198979.
- Bell, N. E. & Hyvönen, J. (2010). "Phylogeny of the moss class Polytrichopsida (BRYOPHYTA): Generic-level structure and incongruent gene trees". Molecular Phylogenetics and Evolution. 55 (2): 381–398. doi:10.1016/j.ympev.2010.02.004. PMID 20152915.
- Bodribb, T.J.; et al. (2020). "Advanced vascular function discovered in a widespread moss". Nature Plants. 6 (3): 273–279. doi:10.1038/s41477-020-0602-x. PMID 32170283. S2CID 212641738.
- Kenrick, Paul & Crane, Peter R. (1997a). The Origin and Early Diversification of Land Plants: A Cladistic Study. Washington, D.C.: Smithsonian Institution Press. ISBN 978-1-56098-730-7.
- Kenrick, P. & Crane, P.R. (1997b). "The origin and early evolution of plants on land". Nature. 389 (6646): 33–39. Bibcode:1997Natur.389...33K. doi:10.1038/37918. S2CID 3866183.
- Crane, Peter R.; Herendeen, Patrick; Friis, Else Marie (October 2004). "Fossils and plant phylogeny". American Journal of Botany. 91 (10): 1683–1699. doi:10.3732/ajb.91.10.1683. PMID 21652317.
- Gerrienne, Philippe; Servais, Thomas; Vecoli, Marco (April 2016). "Plant evolution and terrestrialization during Palaeozoic times—The phylogenetic context". Review of Palaeobotany and Palynology. 227: 4–18. doi:10.1016/j.revpalbo.2016.01.004.
- Konrat, M.; Shaw, A.J.; Renzaglia, K.S. (2010). "A special issue of Phytotaxa dedicated to Bryophytes: The closest living relatives of early land plants". Phytotaxa. 9: 5–10. doi:10.11646/phytotaxa.9.1.3.
- Karol, Kenneth G.; Arumuganathan, Kathiravetpillai; Boore, Jeffrey L.; Duffy, Aaron M.; Everett, Karin DE; Hall, John D.; Hansen, S.K.; Kuehl, Jennifer V.; Mandoli, Dina F.; Mishler, Brent D.; Olmstead, Richard G.; Renzaglia, Karen S. & Wolf, Paul G. (2010). "Complete plastome sequences of Equisetum arvense and Isoetes flaccida: implications for phylogeny and plastid genome evolution of early land plant lineages". BMC Evolutionary Biology. 10 (1): 321. doi:10.1186/1471-2148-10-321. PMC 3087542. PMID 20969798.
- Shaw, A. Jonathan; Szövényi, Péter; Shaw, Blanka (March 2011). "Bryophyte diversity and evolution: Windows into the early evolution of land plants". American Journal of Botany. 98 (3): 352–369. doi:10.3732/ajb.1000316. PMID 21613131.
- Everet, Ray; Eichhorn, Susan (2013). Biology of Plants. W.H.Freeman and Company Publishers.
- Purcell, Adam. "Bryophytes". Basic Biology.
- Glime, Janice. "Economic and Ethnic Uses of Bryophytes" (PDF). harvard.edu.
- Wolffhechel, H. (April 1988). "The suppressiveness of sphagnum peat to Pythium spp". Acta Horticulturae (221): 217–222. doi:10.17660/actahortic.1988.221.22.
- Lesica, P.; McCune, B.; Cooper, S. V.; Hong, W. S. (1991). "Differences in lichen and bryophyte communities between old-growth and managed second-growth forests in the Swan Valley, Montana". Canadian Journal of Botany. 69 (8): 1745–1755. doi:10.1139/b91-222.
|Wikimedia Commons has media related to Bryophytes.|
|Look up bryophyte in Wiktionary, the free dictionary.|
|Wikisource has the text of the 1911 Encyclopædia Britannica article "Bryophyta".|
- Andrew's Moss Site Photos of bryophytes
- 27-May-2013 Centuries-old frozen plants revived, 400-year-old bryophyte specimens left behind by retreating glaciers in Canada are brought back to life in the laboratory.
- Farge, Catherine La; Williams, Krista H.; England, John H. (22 May 2013). "Regeneration of Little Ice Age bryophytes emerging from a polar glacier with implications of totipotency in extreme environments". Proceedings of the National Academy of Sciences. 110 (24): 9839–9844. Bibcode:2013PNAS..110.9839L. doi:10.1073/pnas.1304199110. PMC 3683725. PMID 23716658.
- 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. Online version: Internet Archive.