Eudicots Temporal range: | |
---|---|
Two seed leaves during germination ( Brassica sp.) | |
Scientific classification | |
Kingdom: | Plantae |
Clade: | Streptophyta |
Clade: | Embryophytes |
Clade: | Polysporangiophytes |
Clade: | Tracheophytes |
Clade: | Spermatophytes |
Clade: | Angiosperms |
Clade: | Eudicots |
Clades (APG IV) | |
|
The eudicots, Eudicotidae, or eudicotyledons are a clade of flowering plants (angiosperms) which are mainly characterized by having two seed leaves (cotyledons) upon germination. [1] The term derives from dicotyledon (etymologically, eu = true; di = two; cotyledon = seed leaf). Historically, authors have used the terms tricolpates or non-magnoliid dicots. The current botanical terms were introduced in 1991, by evolutionary botanist James A. Doyle and paleobotanist Carol L. Hotton, to emphasize the later evolutionary divergence of tricolpate dicots from earlier, less specialized, dicots. [2]
Scores of familiar plants are eudicots, including many commonly cultivated and edible plants, numerous trees, tropicals and ornamentals. Among the most well-known eudicot genera are those of the sunflower ( Helianthus ), dandelion ( Taraxacum ), forget-me-not ( Myosotis ), cabbage ( Brassica ), apple ( Malus ), buttercup ( Ranunculus ), maple ( Acer ) and macadamia (Macadamia). Most leafy, mid-latitude trees are also classified as eudicots, with notable exceptions being the magnolias and American tulip tree ( Liriodendron )—which belong to the magnoliids—and Ginkgo biloba , which is not an angiosperm.
The close relationships among flowering plants with tricolpate pollen grains was initially seen in morphological studies of shared derived characters. These plants have a distinct trait in their pollen grains of exhibiting three colpi or grooves paralleling the polar axis. [3]
Later molecular evidence confirmed the genetic basis for the evolutionary relationships among flowering plants with tricolpate pollen grains and dicotyledonous traits. The term means "true dicotyledons", as it contains the majority of plants that have been considered dicots and have characteristics of the dicots. One of the genetic traits which defines the eudicots is the duplication of DELLA protein-encoding genes in their most recent common ancestor. [4] The term "eudicots" has subsequently been widely adopted in botany to refer to one of the two largest clades of angiosperms (constituting over 70% of the angiosperm species), monocots being the other. The remaining angiosperms include magnoliids and what are sometimes referred to as basal angiosperms or paleodicots, but these terms have not been widely or consistently adopted, as they do not refer to a monophyletic group.[ citation needed ]
According to molecular clock calculations, the lineage that led to eudicots split from other plants about 134 million years ago [5] or 155-160 million years ago. [6]
The earlier name for the eudicots is tricolpates, a name which refers to the grooved structure of the pollen. Members of the group have tricolpate pollen, or forms derived from it. These pollens have three or more pores set in furrows called colpi. In contrast, most of the other seed plants (that is the gymnosperms, the monocots and the paleodicots) produce monosulcate pollen, with a single pore set in a differently oriented groove called the sulcus. The name "tricolpates" is preferred by some botanists to avoid confusion with the dicots, a nonmonophyletic group. [7]
The name "eudicots" (plural) is used in the APG systems (from APG system, of 1998, to APG IV system, of 2016) for classification of angiosperms. It is applied to a clade, a monophyletic group, which includes most of the (former) dicots.[ citation needed ]
"Tricolpate" is a synonym for the "Eudicot" monophyletic group, the "true dicotyledons" (which are distinguished from all other flowering plants by their tricolpate pollen structure). The number of pollen grain furrows or pores helps classify the flowering plants, with eudicots having three colpi (tricolpate), and other groups having one sulcus. [8] [7]
Pollen apertures are any modification of the wall of the pollen grain. These modifications include thinning, ridges and pores, they serve as an exit for the pollen contents and allow shrinking and swelling of the grain caused by changes in moisture content. The elongated apertures/ furrows in the pollen grain are called colpi (singular colpus), which, along with pores, are a chief criterion for identifying the pollen classes. [9]
The eudicots can be divided into two groups: the basal eudicots and the core eudicots. [10] Basal eudicot is an informal name for a paraphyletic group. The core eudicots are a monophyletic group. [11] A 2010 study suggested the core eudicots can be divided into two clades, Gunnerales and a clade called Pentapetalae , comprising all the remaining core eudicots. [12]
The Pentapetalae can be then divided into three clades:[ citation needed ]
This division of the eudicots is shown in the following cladogram: [13]
eudicots |
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
The following is a more detailed breakdown according to APG IV, showing within each clade and orders: [14]
The Malpighiales comprise one of the largest orders of flowering plants, containing about 36 families and more than 16,000 species, about 7.8% of the eudicots. The order is very diverse, containing plants as different as the willow, violet, poinsettia, manchineel, rafflesia and coca plant, and are hard to recognize except with molecular phylogenetic evidence. It is not part of any of the classification systems based only on plant morphology. Molecular clock calculations estimate the origin of stem group Malpighiales at around 100 million years ago (Mya) and the origin of crown group Malpighiales at about 90 Mya.
The Magnoliales are an order of flowering plants.
Saxifragales is an order of angiosperms, or flowering plants, containing 15 botanical families and around 100 genera, with nearly 2,500 species. Of the 15 families, many are small, with eight of them being monotypic. The largest family is the Crassulaceae (stonecrops), a diverse group of mostly succulent plants, with about 35 genera. Saxifragales are found worldwide, primarily in temperate to subtropical zones, rarely being encountered growing wild in the tropics; however, many species are now cultivated throughout the world as knowledge of plant husbandry has improved. They can be found in a wide variety of environments, from deserts to fully aquatic habitats, with species adapted to alpine, forested or fully-aquatic habitats. Many are epiphytic or lithophytic, growing on exposed cliff faces, on trees or on rocks, and not requiring a highly organic or nutrient-dense substrate to thrive.
The dicotyledons, also known as dicots, 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. The other group of flowering plants were called monocotyledons, typically each having one cotyledon. Historically, these two groups formed the two divisions of the flowering plants.
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 were classified as dicotyledons, or dicots.
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.
The Crossosomatales are an order, first recognized as such by APG II. They are flowering plants included within the Rosid eudicots.
The Angiosperm Phylogeny Group (APG) is an informal international group of systematic botanists who collaborate to establish a consensus on the taxonomy of flowering plants (angiosperms) that reflects new knowledge about plant relationships discovered through phylogenetic studies.
Dilleniaceae is a family of flowering plants with 11 genera and about 430 known species. Such a family has been universally recognized by taxonomists. It is known to gardeners for the genus Hibbertia, which contains many commercially valuable garden species.
Apertures are areas on the walls of a pollen grain, where the wall is thinner and/or softer. For germination it is necessary that the pollen tube can reach out from the inside of the pollen grain and transport the sperm to the egg deep down in the pistil. The apertures are the places where the pollen tube is able to break through the pollen wall.
The rosids are members of a large clade of flowering plants, containing about 70,000 species, more than a quarter of all angiosperms.
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.
Plant taxonomy is the science that finds, identifies, describes, classifies, and names plants. It is one of the main branches of taxonomy.
The APG II system of plant classification is the second, now obsolete, version of a modern, mostly molecular-based, system of plant taxonomy that was published in April 2003 by the Angiosperm Phylogeny Group. It was a revision of the first APG system, published in 1998, and was superseded in 2009 by a further revision, the APG III system.
Magnoliids, Magnoliidae or Magnolianae 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.
Mesangiospermae is a clade of flowering plants (angiosperms) that contains about 99.95% of all angiosperm species. Mesangiosperms are therefore known as the core angiosperms, in contrast to the earlier-diverging species known as the basal angiosperms. Mesangiospermae includes about 350,000 species, while there are about 175 extant species of basal angiosperms.
The superrosids are members of a large clade of flowering plants, containing more than 88,000 species, and thus more than a quarter of all angiosperms.
In phylogenetic nomenclature, the Pentapetalae are a large group of eudicots that were informally referred to as the "core eudicots" in some papers on angiosperm phylogenetics. They comprise an extremely large and diverse group accounting for about 65% of the species richness of the angiosperms, with wide variability in habit, morphology, chemistry, geographic distribution, and other attributes. Classical systematics, based solely on morphological information, was not able to recognize this group. In fact, the circumscription of the Pentapetalae as a clade is based on strong evidence obtained from DNA molecular analysis data.
The superasterids are members of a large clade of flowering plants, containing more than 122,000 species.