Dicotyledon

Dicotyledon
	Lamium album (white dead nettle)
Scientific classification
Kingdom:	Plantae
Clade:	Tracheophytes
Clade:	Spermatophytes
Clade:	Angiosperms
Groups included
	Eudicots ; Magnoliids ; Amborella ; Nymphaeales ; Austrobaileyales ; Chloranthales ; Ceratophyllum ;
Cladistically included but traditionally excluded taxa
	Monocots ;
Synonyms
	Dicotyledoneae; Magnoliatae Takht. ;

Last updated July 25, 2023

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.

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.

Comparison with monocotyledons

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]

Feature	In monocots	In dicots
Number 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	Three
Number of cotyledons (leaves in the seed)	One	Two
Arrangement of vascular bundles in the stem	Scattered	In concentric circles
Roots	Are adventitious	Develop from the radicle
Arrangement of major leaf veins	Parallel	Reticulate
Secondary growth	Absent	Often present
Stomata	Present on both the upper and lower epidermis of leaves	More common on the lower epidermis of leaves

Comparison of monocots and dicots

Classification

Phylogeny

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]

	Ceratophyllales

	eudicots

monocots

traditional dicots

Historical

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

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 magnoliids Canellales Laurales Magnoliales Piperales unplaced independent lineage Chloranthales probable sister of eudicots Ceratophyllales eudicots Buxales Proteales Ranunculales Trochodendrales core eudicots Dilleniales Gunnerales superrosids Brassicales Celastrales Crossosomatales Cucurbitales Fabales Fagales Geraniales Huerteales Malpighiales Malvales Myrtales Oxalidales Picramniales Rosales Sapindales Saxifragales Vitales Zygophyllales superasterids Apiales 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 Papaverales Hamamelidae Trochodendrales Hamamelidales Daphniphyllales Didymelales Eucommiales Urticales Leitneriales Juglandales Myricales Fagales Casuarinales Caryophyllidae Caryophyllales Polygonales Plumbaginales Dilleniidae Dilleniales Theales Malvales Lecythidales Nepenthales Violales Salicales Capparales Batales Ericales Diapensiales Ebenales Primulales Rosidae Rosales Fabales Proteales Podostemales Haloragales Myrtales Rhizophorales Cornales Santalales Rafflesiales Celastrales Euphorbiales Rhamnales Linales Polygalales Sapindales Geraniales Apiales Asteridae Gentianales Solanales Lamiales Callitrichales Plantaginales Scrophulariales Campanulales Rubiales Dipsacales Calycerales Asterales

Dahlgren and Thorne systems

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

The Thorne system (1992) as depicted by Reveal is:

Dahlgren system	Thorne system
Magnolianae Ranunculanae	Magnolianae Rafflesianae
Nymphaeanae	Nymphaeanae
Caryophyllanae	Caryophyllanae
Theanae Plumbaginanae Polygonanae Primulanae Ericanae	Theanae
Malvanae	Malvanae
Violanae	Violanae
Rosanae	Rosanae
Proteanae	Proteanae
Myrtanae	Myrtanae
Rutanae	Rutanae Celastranae Geranianae
Santalanae	Santalanae
Balanophoranae	Santalanae
Asteranae	Asteranae
Solananae	Solananae
Cornanae Vitanae	Cornanae Aralianae
Loasanae	Loasanae
Gentiananae Lamianae	Gentiananae

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.

Related Research Articles

<span class="mw-page-title-main">Alismatales</span> Order of herbaceous flowering plants of marshy and aquatic habitats

The Alismatales (alismatids) are an order of flowering plants including about 4,500 species. Plants assigned to this order are mostly tropical or aquatic. Some grow in fresh water, some in marine habitats. Perhaps the most important food crop in the order is the corm of the taro plant, Colocasia esculenta.

Arecales is an order of flowering plants. The order has been widely recognised only for the past few decades; until then, the accepted name for the order including these plants was Principes.

The Dioscoreales are an order of monocotyledonous flowering plants in modern classification systems, such as the Angiosperm Phylogeny Group and the Angiosperm Phylogeny Web. Within the monocots Dioscoreales are grouped in the lilioid monocots, where they are in a sister group relationship with the Pandanales. The Dioscoreales must contain the family Dioscoreaceae which includes the yam (Dioscorea), some species of which are an important food source in many regions. Older systems tended to place all lilioid monocots with reticulate veined leaves in Dioscoreales. As currently circumscribed by phylogenetic analysis using combined morphology and molecular methods, Dioscreales contains many reticulate veined vines in Dioscoraceae, it also includes the myco-heterotrophic Burmanniaceae and the autotrophic Nartheciaceae. The order consists of three families, 22 genera and about 850 species.

Liliales is an order of monocotyledonous flowering plants in the Angiosperm Phylogeny Group and Angiosperm Phylogeny Web system, within the lilioid monocots. This order of necessity includes the family Liliaceae. The APG III system (2009) places this order in the monocot clade. In APG III, the family Luzuriagaceae is combined with the family Alstroemeriaceae and the family Petermanniaceae is recognized. Both the order Lililiales and the family Liliaceae have had a widely disputed history, with the circumscription varying greatly from one taxonomist to another. Previous members of this order, which at one stage included most monocots with conspicuous tepals and lacking starch in the endosperm are now distributed over three orders, Liliales, Dioscoreales and Asparagales, using predominantly molecular phylogenetics. The newly delimited Liliales is monophyletic, with ten families. Well known plants from the order include Lilium (lily), tulip, the North American wildflower Trillium, and greenbrier.

The Magnoliales are an order of flowering plants.

The Nymphaeales are an order of flowering plants, consisting of three families of aquatic plants, the Hydatellaceae, the Cabombaceae, and the Nymphaeaceae. It is one of the three orders of basal angiosperms, an early-diverging grade of flowering plants. At least 10 morphological characters unite the Nymphaeales. One of the traits is the absence of a vascular cambium, which is required to produce both xylem (wood) and phloem, which therefore are missing. Molecular synapomorphies are also known.

Monocotyledons, commonly referred to as monocots, are grass and grass-like flowering plants (angiosperms), the seeds of which typically contain only one embryonic leaf, or cotyledon. They constitute one of the major groups into which the flowering plants have traditionally been divided; the rest of the flowering plants have two cotyledons and are classified as dicotyledons, or dicots.

<span class="mw-page-title-main">Magnoliopsida</span>

Magnoliopsida is a valid botanical name for a class of flowering plants. By definition the class will include the family Magnoliaceae, but its circumscription can otherwise vary, being more inclusive or less inclusive depending upon the classification system being discussed.

Ranunculales is an order of flowering plants. Of necessity it contains the family Ranunculaceae, the buttercup family, because the name of the order is based on the name of a genus in that family. Ranunculales belongs to a paraphyletic group known as the basal eudicots. It is the most basal clade in this group; in other words, it is sister to the remaining eudicots. Widely known members include poppies, barberries, hellebores, and buttercups.

Proteales is an order of flowering plants consisting of three families. The Proteales have been recognized by almost all taxonomists.

Austrobaileya is the sole genus consisting of a single species that constitutes the entire flowering plant family Austrobaileyaceae. The species Austrobaileya scandens grows naturally only in the Wet Tropics rainforests of northeastern Queensland, Australia.

Nelumbonaceae is a family of aquatic flowering plants. Nelumbo is the sole extant genus, containing Nelumbo lutea, native to North America, and Nelumbo nucifera, widespread in Asia. At least five other genera, Nelumbites, Exnelumbites, Paleonelumbo, Nelumbago, and Notocyamus are known from fossils.

The eudicots, Eudicotidae, or eudicotyledons are a clade of flowering plants mainly characterized by having two seed leaves upon germination. The term derives from Dicotyledons.

Chloranthaceae is a family of flowering plants (angiosperms), the only family in the order Chloranthales. It is not closely related to any other family of flowering plants, and is among the early-diverging lineages in the angiosperms. They are woody or weakly woody plants occurring in Southeast Asia, the Pacific, Madagascar, Central and South America, and the West Indies. The family consists of four extant genera, totalling about 77 known species according to Christenhusz and Byng in 2016. Some species are used in traditional medicine. The type genus is Chloranthus. The fossil record of the family, mostly represented by pollen such as Clavatipollenites, extends back to the dawn of the history of flowering plants in the Early Cretaceous, and has been found on all continents.

Trimeniaceae is a family of flowering plants recognized by most taxonomists, at least for the past several decades. It is a small family of one genus, Trimenia, with eight known species of woody plants, bearing essential oils. The family is subtropical to tropical and found in Southeast Asia, eastern Australia and on several Pacific Islands.

Plant taxonomy is the science that finds, identifies, describes, classifies, and names plants. It is one of the main branches of taxonomy.

In plant taxonomy, commelinids is a clade of flowering plants within the monocots, distinguished by having cell walls containing ferulic acid.

Magnoliids are a clade of flowering plants. With more than 10,000 species, including magnolias, nutmeg, bay laurel, cinnamon, avocado, black pepper, tulip tree and many others, it is the third-largest group of angiosperms after the eudicots and monocots. The group is characterized by trimerous flowers, pollen with one pore, and usually branching-veined leaves.

The basal angiosperms are the flowering plants which diverged from the lineage leading to most flowering plants. In particular, the most basal angiosperms were called the ANITA grade, which is made up of Amborella, Nymphaeales and Austrobaileyales.

<span class="mw-page-title-main">Lilioid monocots</span> Grade of flowering plant orders, within Lilianae

Lilioid monocots is an informal name used for a grade of five monocot orders in which the majority of species have flowers with relatively large, coloured tepals. This characteristic is similar to that found in lilies ("lily-like"). Petaloid monocots refers to the flowers having tepals which all resemble petals (petaloid). The taxonomic terms Lilianae or Liliiflorae have also been applied to this assemblage at various times. From the early nineteenth century many of the species in this group of plants were put into a very broadly defined family, Liliaceae sensu lato or s.l.. These classification systems are still found in many books and other sources. Within the monocots the Liliaceae s.l. were distinguished from the Glumaceae.

References

↑ 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
1 2 Monocots versus Dicots, University of California Museum of Paleontology , retrieved 25 January 2012
↑ Cole, Theodor C.H.; Hilger, Hartmut H. & Stevens, Peter F. (2017), Angiosperm Phylogeny Poster - Flowering Plant Systematics (PDF), archived from the original (PDF) on 2017-05-17, retrieved 2017-07-13
1 2 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

External links

This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.

[Takh64-1] 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

[TFD-2] "Dicotyl", The Free Dictionary, retrieved 2 January 2016

[Hamilton2006-3] Hamilton, Alan; Hamilton, Patrick (2006), Plant conservation: An ecosystem approach, London: Earthscan, p. 2, ISBN 978-1-84407-083-1

[Simp11-4] Simpson, Michael G. (2011), "Chapter 7: Diversity and Classification of Flowering Plants", Plant Systematics, Elsevier, p. 139, ISBN 978-0-0805-1404-8

[UCB-5] 1 2 Monocots versus Dicots, University of California Museum of Paleontology , retrieved 25 January 2012

[Cole17-6] Cole, Theodor C.H.; Hilger, Hartmut H. & Stevens, Peter F. (2017), Angiosperm Phylogeny Poster - Flowering Plant Systematics (PDF), archived from the original (PDF) on 2017-05-17, retrieved 2017-07-13

[APGIV-7] 1 2 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

[Stuessy10-8] Stuessy, Tod F. (2010), "Paraphyly and the origin and classification of angiosperms." (PDF), Taxon, 59 (3): 689–693, doi:10.1002/tax.593001

[1]

[2]

[3]

[4]

[5]

[6]

[7]

[8]

Authority control
International	FAST
National	Spain France BnF data Germany Israel United States Latvia Japan Czech Republic