The dicotyledons, also known as dicots (or, more rarely, dicotyls),[2] are one of the two groups into which all the flowering plants (angiosperms) were formerly divided. The name refers to one of the typical characteristics of the group: namely, that the seed has two embryonic leaves or cotyledons. There are around 200,000 species within this group.[3] The other group of flowering plants were called monocotyledons (or monocots), typically each having one cotyledon. Historically, these two groups formed the two divisions of the flowering plants.
Dicotyledon plantletYoung castor oil plant showing its prominent two embryonic leaves (cotyledons), which differ from the adult leaves
Largely from the 1990s onwards, molecular phylogenetic research confirmed what had already been suspected: that dicotyledons are not a group made up of all the descendants of a common ancestor (i.e., they are not a monophyletic group). Rather, a number of lineages, such as the magnoliids and groups now collectively known as the basal angiosperms, diverged earlier than the monocots did; in other words, monocots evolved from within the dicots, as traditionally defined. The traditional dicots are thus a paraphyletic group.[4]
The eudicots are the largest monophyletic group within the dicotyledons. They are distinguished from all other flowering plants by the structure of their pollen. Other dicotyledons and the monocotyledons have monosulcate pollen (or derived forms): grains with a single sulcus. Contrastingly, eudicots have tricolpate pollen (or derived forms): grains with three or more pores set in furrows called colpi.
Aside from cotyledon number, other broad differences have been noted between monocots and dicots, although these have proven to be differences primarily between monocots and eudicots. Many early-diverging dicot groups have monocot characteristics such as scattered vascular bundles, trimerous flowers, and non-tricolpate pollen.[5] In addition, some monocots have dicot characteristics such as reticulated leaf veins.[5]
Traditionally, the dicots have been called the Dicotyledones (or Dicotyledoneae), at any rank. If treated as a class, as they are within the Cronquist system, they could be called the Magnoliopsida after the type genusMagnolia. In some schemes, the eudicots were either treated as a separate class, the Rosopsida (type genus Rosa), or as several separate classes. The remaining dicots (palaeodicots or basal angiosperms) may be kept in a single paraphyletic class, called Magnoliopsida, or further divided. Some botanists prefer to retain the dicotyledons as a valid class, arguing its practicality and that it makes evolutionary sense.[8]
APG vs. Cronquistedit
The following lists show the orders in the Angiosperm Phylogeny Group APG IV system traditionally called dicots,[7] together with the older Cronquist system.
Under the Dahlgren and Thorne systems, the subclass name Magnoliidae was used for the dicotyledons. This is also the case in some of the systems derived from the Cronquist system. These two systems are contrasted in the table below in terms of how each categorises by superorder; note that the sequence within each system has been altered in order to pair corresponding taxa
There exist variances between the superorders circumscribed from each system. Namely, although the systems share common names for many of the listed superorders, the specific list orders classified within each varies. For example, Thorne's Theanae corresponds to five distinct superorders under Dahlgren's system, only one of which is called Theanae.
^Cole, Theodor C.H.; Hilger, Hartmut H. & Stevens, Peter F. (2017), (PDF), archived from the original (PDF) on 2017-05-17, retrieved 2017-07-13
^ abAngiosperm Phylogeny Group (2016), "An update of the Angiosperm Phylogeny Group classification for the orders and families of flowering plants: APG IV", Botanical Journal of the Linnean Society, 181 (1): 1–20, doi:10.1111/boj.12385
^Stuessy, Tod F. (2010), "Paraphyly and the origin and classification of angiosperms." (PDF), Taxon, 59 (3): 689–693, doi:10.1002/tax.593001
Wikispecies has information related to Magnoliopsida.
External linksedit
Wikispecies has information related to Magnoliopsida.
World list of dicot species (a.k.a. Magnoliopsida) from the Catalogue of Life, 253,406 species.
Tree browser for dicot orders, families and genera with species counts and estimates via the Catalogue of Life
February 16, 2024
dicotyledon, dicotyledons, also, known, dicots, more, rarely, dicotyls, groups, into, which, flowering, plants, angiosperms, were, formerly, divided, name, refers, typical, characteristics, group, namely, that, seed, embryonic, leaves, cotyledons, there, aroun. The dicotyledons also known as dicots or more rarely dicotyls 2 are one of the two groups into which all the flowering plants angiosperms were formerly divided The name refers to one of the typical characteristics of the group namely that the seed has two embryonic leaves or cotyledons There are around 200 000 species within this group 3 The other group of flowering plants were called monocotyledons or monocots typically each having one cotyledon Historically these two groups formed the two divisions of the flowering plants DicotyledonLamium album white dead nettle Scientific classificationKingdom PlantaeClade TracheophytesClade SpermatophytesClade AngiospermsGroups includedEudicots Magnoliids Amborella Nymphaeales Austrobaileyales Chloranthales CeratophyllumCladistically included but traditionally excluded taxaMonocotsSynonymsDicotyledoneae Magnoliatae Takht 1 Dicotyledon plantletYoung castor oil plant showing its prominent two embryonic leaves cotyledons which differ from the adult leavesLargely from the 1990s onwards molecular phylogenetic research confirmed what had already been suspected that dicotyledons are not a group made up of all the descendants of a common ancestor i e they are not a monophyletic group Rather a number of lineages such as the magnoliids and groups now collectively known as the basal angiosperms diverged earlier than the monocots did in other words monocots evolved from within the dicots as traditionally defined The traditional dicots are thus a paraphyletic group 4 The eudicots are the largest monophyletic group within the dicotyledons They are distinguished from all other flowering plants by the structure of their pollen Other dicotyledons and the monocotyledons have monosulcate pollen or derived forms grains with a single sulcus Contrastingly eudicots have tricolpate pollen or derived forms grains with three or more pores set in furrows called colpi Contents 1 Comparison with monocotyledons 2 Classification 2 1 Phylogeny 2 2 Historical 2 3 APG vs Cronquist 2 4 Dahlgren and Thorne systems 3 See also 4 References 5 External linksComparison with monocotyledons editAside from cotyledon number other broad differences have been noted between monocots and dicots although these have proven to be differences primarily between monocots and eudicots Many early diverging dicot groups have monocot characteristics such as scattered vascular bundles trimerous flowers and non tricolpate pollen 5 In addition some monocots have dicot characteristics such as reticulated leaf veins 5 Feature In monocots In dicotsNumber of parts of each flower In threes flowers are trimerous In fours or fives tetramerous or pentamerous Number of furrows or pores in pollen One ThreeNumber of cotyledons leaves in the seed One TwoArrangement of vascular bundles in the stem Scattered In concentric circlesRoots Are adventitious Develop from the radicleArrangement of major leaf veins Parallel ReticulateSecondary growth Absent Often presentStomata Present on both the upper and lower epidermis of leaves More common on the lower epidermis of leavesComparison of monocots and dicots nbsp Classification editPhylogeny edit The consensus phylogenetic tree used in the APG IV system shows that the group traditionally treated as the dicots is paraphyletic to the monocots 6 7 angiosperms AmborellalesNymphaealesAustrobaileyalescore angiosperms ChloranthalesmagnoliidsCeratophyllales eudicotsmonocots traditional dicotsHistorical edit Traditionally the dicots have been called the Dicotyledones or Dicotyledoneae at any rank If treated as a class as they are within the Cronquist system they could be called the Magnoliopsida after the type genus Magnolia In some schemes the eudicots were either treated as a separate class the Rosopsida type genus Rosa or as several separate classes The remaining dicots palaeodicots or basal angiosperms may be kept in a single paraphyletic class called Magnoliopsida or further divided Some botanists prefer to retain the dicotyledons as a valid class arguing its practicality and that it makes evolutionary sense 8 APG vs Cronquist edit The following lists show the orders in the Angiosperm Phylogeny Group APG IV system traditionally called dicots 7 together with the older Cronquist system APG IV paraphyletic Cronquist system classis Magnoliopsida Amborellales Austrobaileyales Nymphaeales magnoliidsCanellales Laurales Magnoliales Piperalesunplaced independent lineageChloranthalesprobable sister of eudicotsCeratophyllaleseudicotsBuxales Proteales Ranunculales Trochodendrales core eudicotsDilleniales Gunnerales superrosidsBrassicales Celastrales Crossosomatales Cucurbitales Fabales Fagales Geraniales Huerteales Malpighiales Malvales Myrtales Oxalidales Picramniales Rosales Sapindales Saxifragales Vitales ZygophyllalessuperasteridsApiales Aquifoliales Asterales Berberidopsidales Boraginales Bruniales Caryophyllales Cornales Dipsacales Ericales Escalloniales Garryales Gentianales Icacinales Lamiales Metteniusales Paracryphiales Santalales Solanales Vahliales Magnoliidae mostly basal dicots Magnoliales Laurales Piperales Aristolochiales Illiciales Nymphaeales Ranunculales PapaveralesHamamelidae Trochodendrales Hamamelidales Daphniphyllales Didymelales Eucommiales Urticales Leitneriales Juglandales Myricales Fagales CasuarinalesCaryophyllidae Caryophyllales Polygonales PlumbaginalesDilleniidae Dilleniales Theales Malvales Lecythidales Nepenthales Violales Salicales Capparales Batales Ericales Diapensiales Ebenales PrimulalesRosidae Rosales Fabales Proteales Podostemales Haloragales Myrtales Rhizophorales Cornales Santalales Rafflesiales Celastrales Euphorbiales Rhamnales Linales Polygalales Sapindales Geraniales ApialesAsteridae Gentianales Solanales Lamiales Callitrichales Plantaginales Scrophulariales Campanulales Rubiales Dipsacales Calycerales Asterales dd dd Dahlgren and Thorne systems edit Under the Dahlgren and Thorne systems the subclass name Magnoliidae was used for the dicotyledons This is also the case in some of the systems derived from the Cronquist system These two systems are contrasted in the table below in terms of how each categorises by superorder note that the sequence within each system has been altered in order to pair corresponding taxaThe Thorne system 1992 as depicted by Reveal is Dahlgren system Thorne systemMagnolianaeRanunculanae MagnolianaeRafflesianaeNymphaeanae NymphaeanaeCaryophyllanae CaryophyllanaeTheanaePlumbaginanaePolygonanaePrimulanaeEricanae TheanaeMalvanae MalvanaeViolanae ViolanaeRosanae RosanaeProteanae ProteanaeMyrtanae MyrtanaeRutanae RutanaeCelastranaeGeranianaeSantalanae SantalanaeBalanophoranae SantalanaeAsteranae AsteranaeSolananae SolananaeCornanaeVitanae CornanaeAralianaeLoasanae LoasanaeGentiananaeLamianae GentiananaeThere exist variances between the superorders circumscribed from each system Namely although the systems share common names for many of the listed superorders the specific list orders classified within each varies For example Thorne s Theanae corresponds to five distinct superorders under Dahlgren s system only one of which is called Theanae See also editCalycifloraeReferences edit Takhtajan A June 1964 The Taxa of the Higher Plants above the Rank of Order Taxon 13 5 160 164 doi 10 2307 1216134 JSTOR 1216134 Dicotyl The Free Dictionary retrieved 2 January 2016 Hamilton Alan Hamilton Patrick 2006 Plant conservation An ecosystem approach London Earthscan p 2 ISBN 978 1 84407 083 1 Simpson Michael G 2011 Chapter 7 Diversity and Classification of Flowering Plants Plant Systematics Elsevier p 139 ISBN 978 0 0805 1404 8 a b Monocots versus Dicots University of California Museum of Paleontology retrieved 25 January 2012 Cole Theodor C H Hilger Hartmut H amp Stevens Peter F 2017 Angiosperm Phylogeny Poster Flowering Plant Systematics PDF archived from the original PDF on 2017 05 17 retrieved 2017 07 13 a b Angiosperm Phylogeny Group 2016 An update of the Angiosperm Phylogeny Group classification for the orders and families of flowering plants APG IV Botanical Journal of the Linnean Society 181 1 1 20 doi 10 1111 boj 12385 Stuessy Tod F 2010 Paraphyly and the origin and classification of angiosperms PDF Taxon 59 3 689 693 doi 10 1002 tax 593001 nbsp Wikispecies has information related to Magnoliopsida External links edit nbsp Wikispecies has information related to Magnoliopsida World list of dicot species a k a Magnoliopsida from the Catalogue of Life 253 406 species Tree browser for dicot orders families and genera with species counts and estimates via the Catalogue of Life Retrieved from https en wikipedia org w index php title Dicotyledon amp oldid 1174256590, wikipedia, wiki, book, books, library,
