Jump to content

Hornwort

From Wikipedia, the free encyclopedia
The name hornwort also refers to aquatic plants of the genusCeratophyllum,in the family Ceratophyllaceae

Hornwort
Temporal range:90–0MaUpperCretaceous(but see text) topresent
Phaeoceros laevis(L.)Prosk.
Scientific classificationEdit this classification
Kingdom: Plantae
Clade: Embryophytes
Division: Anthocerotophyta
Stotler & Stotl.-Crand., 1977[1]
Classes and orders
Leiosporocerotopsida
Anthocerotopsida

seeClassification.

Synonyms

Anthocerotae

Hornwortsare a group ofnon-vascularEmbryophytes(land plants) constituting the divisionAnthocerotophyta(/ˌænθoʊˌsɛrəˈtɒfətə,-təˈfaɪtə/). The common name refers to the elongated horn-like structure, which is thesporophyte.As inmossesandliverworts,hornworts have agametophyte-dominant life cycle, in which cells of the plant carry only a single set of genetic information; the flattened, green plant body of a hornwort is thegametophytestage of the plant.

Hornworts may be found worldwide, though they tend to grow only in places that are damp or humid. Some species grow in large numbers as tiny weeds in the soil of gardens and cultivated fields. Large tropical andsub-tropicalspecies ofDendrocerosmay be found growing on the bark of trees.

The total number of species is still uncertain. While there are more than 300 published species names, the actual number could be as low as 100-150 species.[2]

Description[edit]

Like all bryophytes, the dominant life phase of a hornwort is thehaploidgametophyte.This stage usually grows as a thinrosetteor ribbon-likethallusbetween one and five centimeters in diameter. Hornworts have lost twoplastiddivision-associated genes, ARC3 and FtsZ2, and have just a singlechloroplastpercell(monoplastidy), with the exception of the genusMegacerosand some species in the generaNothocerosandAnthoceros,which have more than one chloroplast per cell (polyplastidy). In the polyplastidic species, and also some of the monoplastidic species, a cellular structure called apyrenoidis absent.[3][4]Thepyrenoid,which is both a food storing organ and enables a more efficient photosynthesis, has evolved independently five to six times in hornworts and is present in half of the roughly 200 species.[5]It is formed by the fusion of the chloroplast with otherorganellesand is composed predominantly ofRuBisCO,the key enzyme in carbon fixation. By using inorganic carbon transporters and carbonic anhydrases, up to a 50-fold increase in CO2levels can be achieved.[6]This particular feature is very unusual in landplants,unique to hornworts, but is common amongalgae.[7][8]They are also the only group of land plants whereflavonoidsare completely absent.[9]

Many hornworts develop internalmucilage-filled cavities or canals when groups of cells break down. These cavities secrete hormogonium-inducing factors (HIF) that stimulate nearby, free-livingphotosyntheticcyanobacteria,especially species ofNostoc,to invade and colonize these cavities.[10]Such colonies of bacteria growing inside the thallus give the hornwort a distinctive blue-green color. Symbioticcyanobacteriahave not been reported inMegacerosorFolioceros.[11]There may also be smallslime poreson the underside of thethallus.These pores superficially resemble thestomataof other plants.

The horn-shapedsporophytegrows from anarchegoniumembedded deep in the gametophyte. The growth of the hornwort sporophyte happens from a persistent basalmeristem,in contrast to the sporophyte of moss (apical growth) and liverworts (intercalary growth).[12]Unlikeliverworts,hornworts have truestomataon their sporophyte as most mosses do. The exceptions are the speciesFolioceros incurvus,the genusNotothylasand the three closely related generaMegaceros,NothocerosandDendroceros,which do not have stomata.[13][14]Notothylasalso differ from other hornworts in having a reduced sporophyte only a few millimeters tall. The sporophyte in hornworts is unique among bryophytes in being long-lived with a persistent photosynthetic capacity.[15]The sporophyte lacks anapical meristem,anauxin-sensitive point of divergence with other land plants some time in theLate Silurian/Early Devonian.[16][17]

When the sporophyte is mature, it has a multicellular outer layer, a central rod-likecolumellarunning up the center, and a layer oftissuein between that produces spores andpseudo-elaters.The pseudo-elaters are multi-cellular, unlike the elaters ofliverworts.They havehelicalthickenings that change shape in response to drying out; they twist and thereby help to disperse the spores. Hornwort spores are relatively large forbryophytes,measuring between 30 and 80μmin diameter or more. The spores are polar, usually with a distinctive Y-shaped tri-radiate ridge on theproximalsurface, and with adistalsurface ornamented with bumps or spines.

Life cycle[edit]

The life of a hornwort starts from ahaploidspore. The spores can be yellow, brown or green. Yellow and brown spores have a thicker wall and contain oils that both protect against desiccation and function as a nutrient storage, allowing them to survive for years. The speciesFolioceros fuciformisand the generaMegaceros,NothocerosandDendroceroshave short-lived spores with thin and colorless walls that appear green due to the presence of a chloroplast.[18][19]In most species, there is a single cell inside the spore, and a slender extension of this cell called thegerm tubegerminates from the proximal side of the spore.[20]The tip of the germ tube divides to form anoctant (solid geometry)of cells, and the firstrhizoidgrows as an extension of the original germ cell.[clarification needed]The tip continues to divide new cells, which produces a thalloidprotonema.By contrast, species of the familyDendrocerotaceaemay begin dividing within the spore, becomingmulticellularand evenphotosyntheticbefore the spore germinates.[20]In either case, the protonema is a transitory stage in the life of a hornwort.

Life cycle of a typical hornwortPhaeoceros.Click on the image to enlarge.

From the protonema grows the adultgametophyte,which is the persistent and independent stage in the life cycle. This stage usually grows as a thinrosetteor ribbon-likethallusbetween one and five centimeters in diameter, and several layers of cells in thickness. It is green or yellow-green from thechlorophyllin its cells, or bluish-green when colonies of cyanobacteria grow inside the plant.

When the gametophyte has grown to its adult size, it produces the sex organs of the hornwort. Most plants aremonoecious,with both sex organs on the same plant, but some plants (even within the same species) aredioecious,with separate male and female gametophytes. The female organs are known asarchegonia(singular archegonium) and the male organs are known asantheridia(singular antheridium). Both kinds of organs develop just below the surface of the plant and are only later exposed by disintegration of the overlying cells.

The biflagellatespermmust swim from the antheridia, or else be splashed to the archegonia. When this happens, the sperm and egg cell fuse to form azygote,the cell from which the sporophyte stage of the life cycle will develop. Unlike all other bryophytes, the first cell division of the zygote islongitudinal.Further divisions produce three basic regions of the sporophyte.

At the bottom of thesporophyte(closest to the interior of the gametophyte), is a foot. This is a globular group of cells that receives nutrients from the parent gametophyte, on which the sporophyte will spend its entire existence. In the middle of the sporophyte (just above the foot), is ameristemthat will continue to divide and produce new cells for the third region. This third region is thecapsule.Both the central and surface cells of the capsule are sterile, but between them is a layer of cells that will divide to producepseudo-elatersandspores.These are released from the capsule when it splits lengthwise from the tip.

Evolutionary history[edit]

While the fossil record ofcrown grouphornworts only begins in the upperCretaceous,the lower DevonianHorneophytonmay represent a stem group to the clade, as it possesses asporangiumwith central columella not attached at the roof.[21]However, the same form of columella is also characteristic of basal moss groups, such as theSphagnopsidaandAndreaeopsida,and has been interpreted as a character common to all early land plants withstomata.[22]The divergence between hornworts andSetaphyta(mosses and liverworts) is estimated to have occurred 479–450 million years ago,[23]and the last common ancestor of present-day hornworts lived in middle Permian about 275 million years ago.[24]Chromosome-scale genome sequencing of three hornwort species corroborates that stomata evolved only once during land plant evolution. It also shows that the three groups ofbryophytesshare a common ancestor that branched off from the other landplants early in evolution, and thatliverwortsandmossesare more closely related to each other than to hornworts.[25]Unlike other land plants, the hornwort genome has the low-CO2inducible B gene (LCIB), which is also found in some species of algae. Because the diffusion rate of carbon dioxide is 10,000-fold higher in air than in water, aquatic algae require a mechanism to concentrate CO2in chloroplasts so as to allow the photosyntheticRuBisCoprotein to function efficiently. LCIB is one component of this CO2-concentrating mechanism.[26]

Classification[edit]

The hornwortDendroceroscrispusgrowing on the bark of a tree.

Hornworts were traditionally considered a class within the division Bryophyta (bryophytes). Later on, the bryophytes were consideredparaphyletic,and hence the hornworts were given their own division,Anthocerotophyta(sometimes misspelledAnthocerophyta). However, the most recent phylogenetic evidence leans strongly towards bryophyte monophyly,[27]and it has been proposed that hornworts are de-ranked to the original classAnthocerotopsida.[28]

Traditionally, there was a single class of hornworts, called Anthocerotopsida, or olderAnthocerotae.More recently, a second class Leiosporocertotopsida has been segregated for the singularly unusual speciesLeiosporoceros dussii.All other hornworts remain in the class Anthocerotopsida. These two classes are divided further into fiveorders,each containing a singlefamily.

Among land plants, hornworts are one of the earliest-diverging lineages of the early land plant ancestors;[25]cladistic analysis implies that the group originated prior to theDevonian,around the same time as the mosses and liverworts. There are about 200speciesknown, but new species are still being discovered. The number and names ofgeneraare a current matter of investigation, and several competing classification schemes have been published since 1988.

Structural features that have been used in the classification of hornworts include: the anatomy of chloroplasts and their numbers within cells, the presence of apyrenoid,the numbers ofantheridiawithin androecia, and the arrangement of jacket cells of the antheridia.[29]

Phylogeny[edit]

Recent studies of molecular, ultrastructural, and morphological data have yielded a new classification of hornworts.[30][31]

Class Leiosporocerotopsida

Leiosporocerotales

Class Anthocerotopsida

Anthocerotales
Notothyladales
Phymatocerotales
Dendrocerotales
Leiosporocerotopsida
Leiosporocerotales
Leiosporocerotaceae

Leiosporoceros

Anthocerotopsida
The currentphylogenyand composition of the Anthocerotophyta.[30][32][33][34]

See also[edit]

References[edit]

  1. ^Stotler, Raymond E.; Barbara J. Candall-Stotler (1977). "A checklist of the liverworts and hornworts of North America".The Bryologist.80(3). American Bryological and Lichenological Society: 405–428.doi:10.2307/3242017.JSTOR3242017.
  2. ^Lepp, Heino (12 September 2012)."What is a hornwort?".Australian Bryophytes.Australian National Botanic Gardens.
  3. ^MacLeod, Alexander I.; Raval, Parth K.; Stockhorst, Simon; Knopp, Michael R.; Frangedakis, Eftychios; Gould, Sven B. (2022)."Loss of Plastid Developmental Genes Coincides with a Reversion to Monoplastidy in Hornworts".Frontiers in Plant Science.13.bioRxiv10.1101/2022.01.11.475830.doi:10.3389/fpls.2022.863076.PMID35360315.
  4. ^Hornworts: An Overlooked Window into Carbon-Concentrating Mechanisms - Villarreal Lab
  5. ^Villarreal, Juan Carlos; Renner, Susanne S. (2012-11-13)."Hornwort pyrenoids, carbon-concentrating structures, evolved and were lost at least five times during the last 100 million years".Proceedings of the National Academy of Sciences.109(46): 18873–18878.Bibcode:2012PNAS..10918873V.doi:10.1073/pnas.1213498109.PMC3503201.PMID23115334.
  6. ^Meyer, Moritz T.; McCormick, Alistair J.; Griffiths, Howard (2016). "Will an algal CO2-concentrating mechanism work in higher plants? ".Current Opinion in Plant Biology.31:181–188.doi:10.1016/j.pbi.2016.04.009.PMID27194106.
  7. ^Villarreal, Juan Carlos; Renner, Susanne S. (2012-11-13)."Hornwort pyrenoids, carbon-concentrating structures, evolved and were lost at least five times during the last 100 million years".Proceedings of the National Academy of Sciences.109(46): 18873–18878.Bibcode:2012PNAS..10918873V.doi:10.1073/pnas.1213498109.PMC3503201.PMID23115334.
  8. ^BTI researchers unlocking hornworts' secrets | EurekAlert! Science News
  9. ^Davies, Kevin M.; Jibran, Rubina; Zhou, Yanfei; Albert, Nick W.; Brummell, David A.; Jordan, Brian R.; Bowman, John L.; Schwinn, Kathy E. (2020)."The Evolution of Flavonoid Biosynthesis: A Bryophyte Perspective".Frontiers in Plant Science.11:7.doi:10.3389/fpls.2020.00007.PMC7010833.PMID32117358.
  10. ^Meeks, JC (1998)."Symbiosis between nitrogen-fixing cyanobacteria and plants".BioScience.48(4): 266–276.doi:10.2307/1313353.JSTOR1313353.
  11. ^Srivastava, Ashish Kumar; Rai, Amar Nath; Neilan, Brett A. (2013).Stress Biology of Cyanobacteria: Molecular Mechanisms to Cellular Responses.CRC Press.ISBN978-1-4665-0478-3.
  12. ^Fouracre, Jim P; Harrison, C Jill (2022-08-29)."How was apical growth regulated in the ancestral land plant? Insights from the development of non-seed plants".Plant Physiology.190(1): 100–112.doi:10.1093/plphys/kiac313.ISSN0032-0889.PMC9434304.PMID35771646.
  13. ^Renzaglia, K. S.; Villarreal, J. C.; Piatkowski, B. T.; Lucas, J. R.; Merced, A. (2017)."Hornwort Stomata: Architecture and Fate Shared with 400-Million-Year-Old Fossil Plants without Leaves".Plant Physiology.174(2): 788–797.doi:10.1104/pp.17.00156.PMC5462037.PMID28584065.
  14. ^Classification of the Phylum Anthocerotophyta Stotl. & Crand.-Stotl.
  15. ^Qiu, Yin-Long; Li, Libo; Wang, Bin; Chen, Zhiduan; Knoop, Volker; Groth-Malonek, Milena; Dombrovska, Olena; Lee, Jungho; Kent, Livija; Rest, Joshua; Estabrook, George F.; Hendry, Tory A.; Taylor, David W.; Testa, Christopher M.; Ambros, Mathew (2006-10-17)."The deepest divergences in land plants inferred from phylogenomic evidence".Proceedings of the National Academy of Sciences.103(42): 15511–15516.Bibcode:2006PNAS..10315511Q.doi:10.1073/pnas.0603335103.PMC1622854.PMID17030812.
  16. ^Cooke, Todd J; Poli, DorothyBelle; Cohen, Jerry D (2003). "Did auxin play a crucial role in the evolution of novel body plans during the Late Silurian-Early Devonian radiation of land plants?".The Evolution of Plant Physiology.Elsevier.pp. 85–107.doi:10.1016/b978-012339552-8/50006-8.ISBN978-0-12-339552-8.
  17. ^Friedman, William E.; Moore, Richard C.; Purugganan, Michael D. (2004)."The evolution of plant development".American Journal of Botany.91(10).Botanical Society of America(Wiley): 1726–1741.doi:10.3732/ajb.91.10.1726.ISSN0002-9122.PMID21652320.
  18. ^Bryophyte Biology
  19. ^NEW CLASSIFICATION OF ANTHOCEROTAE - J-Stage
  20. ^abChopra, R. N.; Kumra, P. K. (1988).Biology of Bryophytes.New York: John Wiley & Sons.ISBN0-470-21359-0.
  21. ^Qiu, Y.L.; Li, L.; Wang, B.; Chen, Z.; Knoop, V.; Groth-malonek, M.; Dombrovska, O.; Lee, J.; Kent, L.; Rest, J.; et al. (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.PMC1622854.PMID17030812.
  22. ^Kenrick, Paul; Peter R. Crane (1997).The Origin and Early Diversification of Land Plants: A Cladistic Study.Washington, D. C.: Smithsonian Institution Press. pp. 55–56.ISBN1-56098-730-8.
  23. ^Harris, Brogan J.; Clark, James W.; Schrempf, Dominik; Szöllősi, Gergely J.; Donoghue, Philip C. J.; Hetherington, Alistair M.; Williams, Tom A. (2022)."Divergent evolutionary trajectories of bryophytes and tracheophytes from a complex common ancestor of land plants".Nature Ecology & Evolution.6(11): 1634–1643.Bibcode:2022NatEE...6.1634H.doi:10.1038/s41559-022-01885-x.PMC9630106.PMID36175544.
  24. ^Zhang, Jian; Fu, Xin-Xing; Li, Rui-Qi; Zhao, Xiang; Liu, Yang; Li, Ming-He; Zwaenepoel, Arthur; Ma, Hong; Goffinet, Bernard; Guan, Yan-Long; Xue, Jia-Yu; Liao, Yi-Ying; Wang, Qing-Feng; Wang, Qing-Hua; Wang, Jie-Yu; Zhang, Guo-Qiang; Wang, Zhi-Wen; Jia, Yu; Wang, Mei-Zhi; Dong, Shan-Shan; Yang, Jian-Fen; Jiao, Yuan-Nian; Guo, Ya-Long; Kong, Hong-Zhi; Lu, An-Ming; Yang, Huan-Ming; Zhang, Shou-Zhou; Van De Peer, Yves; Liu, Zhong-Jian; Chen, Zhi-Duan (2020)."The hornwort genome and early land plant evolution".Nature Plants.6(2): 107–118.doi:10.1038/s41477-019-0588-4.PMC7027989.PMID32042158.
  25. ^abLi, F-W.; Nishiyama, T.; Waller, M.; et, al. (2020)."Anthocerosgenomes 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.PMC8075897.PMID32170292.
  26. ^Frangedakis, Eftychios; Shimamura, Masaki; Villarreal, Juan Carlos; Li, Fay-Wei; Tomaselli, Marta; Waller, Manuel; Sakakibara, Keiko; Renzaglia, Karen S.; Szövényi, Péter (January 2021)."The hornworts: morphology, evolution and development".New Phytologist.229(2): 735–754.doi:10.1111/nph.16874.PMC7881058.PMID32790880.
  27. ^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.PMC8321542.PMID33871608.
  28. ^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.PMID30411803.S2CID53240320.
  29. ^D. Christine Cargill; Karen S. Renzaglia; Juan Carlos Villarreal; R. Joel Duff (2005), "Generic concepts within hornworts: Historical review, contemporary insights and future directions",Australian Systematic Botany,18:7–16,doi:10.1071/sb04012
  30. ^abDuff, R. Joel; Juan Carlos Villarreal; D. Christine Cargill; Karen S. Renzaglia (2007). "Progress and challenges toward a phylogeny and classification of the hornworts".The Bryologist.110(2): 214–243.doi:10.1639/0007-2745(2007)110[214:PACTDA]2.0.CO;2.S2CID85582943.
  31. ^Cole, Theodor C. H.; Hilger, Hartmut H.; Goffinet, Bernard."Bryophyte phylogeny poster: systematics and Characteristics of Nonvascular Land Plants (Mosses, Liverworts, Hornworts)".2021.Retrieved6 December2022.
  32. ^Villareal, J. C.; Cargill, D. C.; Hagborg, A.; Söderström, L.; Renzaglia, K. S. (2010)."A synthesis of hornwort diversity: Patterns, causes and future work"(PDF).Phytotaxa.9:150–166.doi:10.11646/phytotaxa.9.1.8.
  33. ^Peñaloza-Bojacá, Gabriel Felipe; Villarreal-Aguilar, Juan Carlos; Maciel-Silva, Adaíses Simone (2019)."Phylogenetic and morphological infrageneric classification of the genus Dendroceros (Dendrocerotaceae; Anthocerotophyta), with the addition of two new subgenera".Systematics and Biodiversity.17(7): 712–727.Bibcode:2019SyBio..17..712P.doi:10.1080/14772000.2019.1682080.S2CID209591279.
  34. ^Brinda, John C.; Atwood, John J."The Bryophyte Nomenclator".7 December 2022.Retrieved7 December2022.
  • Grolle, Riclef (1983). "Nomina generica Hepaticarum; references, types and synonymies".Acta Botanica Fennica.121:1–62.
  • Hasegawa, J. (1994). "New classification of Anthocerotae".Journal of the Hattori Botanical Laboratory.76:21–34.
  • Renzaglia, Karen S. (1978). "A comparative morphology and developmental anatomy of the Anthocerotophyta".Journal of the Hattori Botanical Laboratory.44:31–90.
  • Renzaglia, Karen S. & Vaughn, Kevin C. (2000). Anatomy, development, and classification of hornworts. In A. Jonathan Shaw & Bernard Goffinet (Eds.),Bryophyte Biology,pp. 1–20. Cambridge:Cambridge University Press.ISBN0-521-66097-1.
  • Schofield, W. B. (1985).Introduction to Bryology.New York: Macmillan.
  • Schuster, Rudolf M. (1992).The Hepaticae and Anthocerotae of North America, East of the Hundredth Meridian.Vol. VI. Chicago:Field Museum of Natural History.
  • Smith, Gilbert M. (1938).Cryptogamic Botany, Volume II: Bryophytes and Pteridophytes.New York: McGraw-Hill Book Company.
  • Watson, E. V. (1971).The Structure and Life of Bryophytes(3rd ed.). London: Hutchinson University Library.ISBN0-09-109301-5.
Retrieved from "https://en.wikipedia.org/w/index.php?title=Hornwort&oldid=1228335429"