蘚苔類、コケ植物

関: Bryophyta

WordNet

any of numerous plants of the division Bryophyta (同)nonvascular plant
a division of nonflowering plants characterized by rhizoids rather than true roots and having little or no organized vascular tissue and showing alternation of generations between gamete-bearing forms and spore-bearing forms; comprises true mosses (Bryops (同)division Bryophyta

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2015/08/25 01:38:42」(JST)

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Marchantia, a liverwort

Bryophyte is a traditional name used to refer to all embryophytes (land plants) that do not have true vascular tissue and are therefore called "non-vascular plants".^[1] Some bryophytes do have specialized tissues for the transport of water; however, since these do not contain lignin, they are not considered to be true vascular tissue.^[2] As of 2014^[update], it is uncertain whether bryophytes are a natural or monophyletic group or a paraphyletic group, but the name is convenient and remains in use as a collective term for mosses, hornworts, and liverworts. Bryophytes produce enclosed reproductive structures (gametangia and sporangia), but they produce neither flowers nor seeds, reproducing via spores. The term "bryophyte" comes from Greek βρύον, bryon, "tree-moss, oyster-green" + φυτόν – phyton "plant".

Life cycle

Life cycle of a dioicous bryophyte.

Like all land plants (embryophytes), bryophytes have life cycles with alternation of generations. A haploid gametophyte, each of whose cells contains a fixed number of unpaired chromosomes, gives rise to a diploid sporophyte, each of whose cells contains twice the number 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.^[3] 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).

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 create elaborate structures that bear gametangia called gametangiophores. Sperm are flagellated and must swim from antheridia to archegonia. Arthropods may assist in transfer of sperm.^[4] Fertilized eggs become zygotes, which develop into sporophyte embryos inside the archegonia. Mature sporophytes do not branch and 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.

Sexuality

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 stamens (microsporangia) and flowers with pistils (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 is said to have the advantage of emphasizing the difference between bryophyte and seed plant sexuality.^[5]

Monoicous plants are necessarily bisexual (or hermaphroditic), meaning that the same plant has both sexes.^[5] 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).^[5]^[6] Dioicous plants are unisexual, meaning that the same plant has only one sex.^[5] All four patterns (autoicous, paroicous, synoicous and dioicous) occur in species of the moss genus Bryum.^[6]

Classification and phylogeny

Hornworts include those bryophytes that are believed to be the closest living relatives of the vascular plants.

Mosses are one group of bryophytes.

Traditionally, all living land plants without vascular tissues were classified in a single taxonomic group, often a division (or phylum). More recently, phylogenetic research has questioned whether the bryophytes form a monophyletic group and thus whether they should form a single taxon. Although a 2005 study supported the traditional view that the bryophytes form a monophyletic group,^[7] by 2010 a broad consensus had emerged among systematists that bryophytes as a whole are not a natural group (i.e., are paraphyletic), although each of the three extant (living) groups is monophyletic.^[8]^[9]^[10] The three lineages are Marchantiophyta (liverworts), Bryophyta (mosses) and Anthocerotophyta (hornworts).^[11] The vascular plants or tracheophytes are the fourth lineage of living land plants. In this analysis, hornworts are sister to vascular plants and liverworts are sister to all other land plants.^[10]^[12] However, phylogenetic studies continue to produce different results; in particular those based on gene sequences suggest the bryophytes are paraphyletic, whereas those based on the amino acid translations of the same genes suggest they are monophyletic. A 2014 study concluded that composition biases were responsible for the conflicting results and that the bryophytes are monophyletic.^[13] The issue remains unresolved.

Paraphyletic view

embryophytes

liverworts

mosses

	hornworts

	vascular plants

bryophytes

When extinct plants are taken into account, the picture is slightly altered. Some extinct land plants, such as the horneophytes, are not bryophytes, but also are not vascular plants because, like bryophytes, they do not have true vascular tissue. A different distinction is needed. In bryophytes, the sporophyte is a simple unbranched structure with a single spore-forming organ (sporangium). In all other land plants, the polysporangiophytes, the sporophyte is branched and carries many sporangia.^[14]^[15] It has been argued that this contrast between bryophytes and other land plants is less misleading than the traditional one of non-vascular versus vascular plant, since many mosses have well-developed water-conducting vessels.^[16] The contrast is shown in a slightly different cladogram:^[17]

land plants

liverworts

mosses

hornworts

polysporangiophytes

	"protracheophytes", such as Horneophyton or Aglaophyton

	tracheophytes or vascular plants

The term "bryophyte" thus refers to a grade of lineages defined primarily by what they lack: compared to other living land plants, they lack vascular tissue containing lignin; compared to all other land plants, they lack 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).

Other views

An alternative phylogeny, based on amino acids rather than genes, shows bryophytes as a monophyletic group:^[18]

embryophytes

bryophytes

hornworts

	liverworts

	mosses

vascular plants

If this phylogeny proves correct, then the complex sporophyte of living vascular plants might have evolved independently of the simpler unbranched sporophyte present in bryophytes.^[13] Other studies suggest a monophyletic group comprising liverworts and mosses, with hornworts being sister to vascular plants.^[19]

Evolution

Bryophytes are the oldest of all lineages of land plants and are believed to be a vital link in the migration of plants from aquatic environments onto land. A number of physical features link bryophytes to both land plants and aquatic plants. Two distinct adaptations have helped to make the move from water to land possible and forged the way for plants to colonize the Earth's terrestrial environments. A waxy cuticle covering the soft tissue of the plant provides protection and prevents desiccation of the plant's tissues; and the development of gametangia provided further protection specifically for gametes. They also have embryonic development which is a significant adaptation seen in land plants and not green algae. Connections to their aquatic ancestry are also evident through their dependence on water for reproduction and survival. A thin layer of water is required on the surface of the plant to enable the movement of sperm between gametophytes and the fertilization of an egg.^[20]

Comparison

Summary of the differential characteristics of the gametophytes of the three groups of bryophytes:

	Liverworts	Mosses	Hornworts
Structure	Thalloid or foliose	Foliose	Thalloid
Symmetry	Dorsiventral or radial	Radial	Dorsiventral
Rhizoids	Unicellular	Pluricellular	Unicellular
Chloroplasts/cell	Many	Many	One
Protonema	Reduced	Present	Absent
Gametangia (antheridia and archegonia)	Superficial	Superficial	Immersed

Summary of the differential characteristics of the sporophytes of the three groups of bryophytes:

	Liverworts	Mosses	Hornworts
Structure	Small, without chlorophyll	Large, with chlorophyll	Large, with chlorophyll
Growth	Defined	Defined	Continuous
Seta	Present	Present	Absent
Capsule form	Simple	Differentiated (operculum, peristome)	Alongated
Maturation of spores	Simultaneous	Simultaneous	Graduate
Dispersion of spores	Elater	Peristome teeth	Pseudo-elaters
Columella	Absent	Present	Present
Dehiscence	Longitudinal or irregular	Transversal	Longitudinal
Stomata	Absent	Present	Present

References

^ "Reviews glossary". Retrieved 2009-03-26.
^ "What are Bryophytes". Retrieved 2009-05-31.
^ "Bryophytes - introduction". Retrieved 2009-05-31.
^ Cronberg N, Natcheva R, Hedlund K (2006). "Microarthropods Mediate Sperm Transfer in Mosses". Science 313 (5791): 1255. doi:10.1126/science.1128707. PMID 16946062.
^ ^a ^b ^c ^d Glime, J.M. & Bisang, I. (2014). "Sexuality: Its Determination (Ch. 3-1)" (PDF). In Glime, J.M. Bryophyte Ecology. Volume 1 Physiological Ecology. Michigan Technological University and the International Association of Bryologists. Retrieved 2014-11-09.
^ ^a ^b 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.)
^ 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. |accessdate= requires |url= (help)
^ 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.
^ Troitsky AV, Ignatov MS, Bobrova VK, Milyutina IA (December 2007). "Contribution of genosystematics to current concepts of phylogeny and classification of bryophytes". Biochemistry Mosc. 72 (12): 1368–76. doi:10.1134/S0006297907120115. PMID 18205621.
^ ^a ^b Knoop, Volker (2010). "Looking for sense in the nonsense: a short review of non-coding organellar DNA elucidating the phylogeny of bryophytes". Tropical Bryology 31: 51–60.
^ "GLOSSARY B". Retrieved 2009-03-26.
^ Qiu, Y. L., Li, L., Wang, B. et al. (October 2006). "The deepest divergences in land plants inferred from phylogenomic evidence". Proceedings of the National Academy of Sciences 103 (42): 15511–6. Bibcode:2006PNAS..10315511Q. doi:10.1073/pnas.0603335103. PMC 1622854. PMID 17030812.
^ ^a ^b Cox, Cymon J.; Li, Blaise; Foster, Peter G.; Embley, T. Martin & Civáň, Peter (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. PMID 24399481.
^ 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.
^ 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.
^ Crane, P. R.; Herendeen, P. & Friis, E. M. (2004). "Fossils and plant phylogeny". American Journal of Botany 91 (10): 1683–99. doi:10.3732/ajb.91.10.1683. PMID 21652317.
^ Cox et al. 2014, p. 274.
^ 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. PMID 20969798.
^ Purcell, Adam. "Bryophytes". Basic Biology.

Bibliography

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: 1745–1755

External links

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.[1]

English Journal

Tolerance to environmental desiccation in moss sperm.

Shortlidge EE, Rosenstiel TN, Eppley SM.SourceDepartment of Biology and Center for Life in Extreme Environments, Portland State University, PO Box 751, Portland, OR 97207-0751, USA.
The New phytologist.New Phytol.2012 May;194(3):741-50. doi: 10.1111/j.1469-8137.2012.04106.x. Epub 2012 Mar 15.
• Sexual reproduction in mosses requires that sperm be released freely into the environment before finding and fertilizing a receptive female. After release from the male plant, moss sperm may experience a range of abiotic stresses; however, few data are available examining stress tolerance of mos
PMID 22420692

Characterization of the plasma membrane H+-ATPase in the liverwort Marchantia polymorpha.

Okumura M, Inoue SI, Takahashi K, Ishizaki K, Kohchi T, Kinoshita T.Source1 Nagoya University;
Plant physiology.Plant Physiol.2012 Apr 11. [Epub ahead of print]
The plasma membrane H+-ATPase generates an electrochemical gradient of H+ across the plasma membrane that provides the driving force for solute transport and regulates pH homeostasis and membrane potential in plant cells. Recent studies have demonstrated that phosphorylation of the penultimate threo
PMID 22496511

Japanese Journal

日本の貴重なコケの森「奥入瀬渓流」

蘚苔類研究 = Bryological research 11(5), 144-146, 2015-08
NAID 40020573923

Changes in epiphyte diversity in declining forests : implications for conservation and restoration

Landscape and ecological engineering : official journal of the International Consortium of Landscape and Ecological Engineering (ICLEE) 11(2), 283-291, 2015-07
NAID 40020539735