HOME

TheInfoList



The dicotyledons, also known as dicots (or more rarely dicotyls), are one of the two groups into which all the
flowering plant The flowering plants, also known as Angiospermae (), or Magnoliophyta (), are the most diverse group of Embryophyte, land plants, with 64 Order(biology), orders, 416 Family (biology), families, approximately 13,000 known Genus, genera and 300,000 ...

flowering plant
s or angiosperms were formerly divided. The name refers to one of the typical characteristics of the group, namely that the
seed A seed is an embryonic ''Embryonic'' is the twelfth studio album by experimental rock band the Flaming Lips released on October 13, 2009, on Warner Bros. Records, Warner Bros. The band's first double album, it was released to generally positiv ...

seed
has two embryonic leaves or
cotyledon File:Germination-en.svg, 335px, Schematic of epigeal vs hypogeal germination A cotyledon (; ; ; , gen. (), ) is a significant part of the embryo within the seed of a plant, and is defined as "the embryonic leaf in seed-bearing plants, one o ...
s. There are around 200,000 
species In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechanis ...

species
within this group. The other group of flowering plants were called
monocotyledon Monocotyledons (), commonly referred to as monocots, (Lilianae ''sensu'' Chase & Reveal) are grass and grass-like flowering plants (angiosperms), the seeds of which typically contain only one Embryo#Plant embryos, embryonic leaf, or cotyledon. The ...
s or monocots, typically having one cotyledon. Historically, these two groups formed the two divisions of the flowering plants. Largely from the 1990s onwards,
molecular phylogenetic Molecular phylogenetics () is the branch of phylogeny that analyzes genetic, hereditary molecular differences, predominately in DNA sequences, to gain information on an organism's evolutionary relationships. From these analyses, it is possible to ...
research confirmed what had already been suspected, namely that dicotyledons are not a group made up of all the descendants of a common ancestor (i.e. they are not a
monophyletic Image:Monophyly, paraphyly, polyphyly.png, 300px, A cladogram of the primates, showing a ''monophyletic'' taxon: ''the simians'' (in yellow); a ''paraphyletic'' taxon: ''the prosimians'' (in cyan, including the red patch); and a ''polyphyletic'' ...
group). Rather, a number of lineages, such as the
magnoliids Magnoliids (or Magnoliidae or Magnolianae) are a group of flowering plant The flowering plants, also known as Angiospermae (), or Magnoliophyta (), are the most diverse group of Embryophyte, land plants, with 64 Order(biology), orders, 416 Famil ...
and groups now collectively known as the
basal angiosperms '', from the Nymphaeales The basal angiosperms are the flowering plant The flowering plants, also known as Angiospermae (), or Magnoliophyta (), are the most diverse group of Embryophyte, land plants, with 64 Order(biology), orders, 416 Family (b ...
, 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 In taxonomy, a group is paraphyletic if it consists of the group's last common ancestor and all descendants of that ancestor excluding a few—typically only one or two—Monophyly, monophyletic subgroups. The group is said to be paraphyleti ...
group. The
eudicots The eudicots, Eudicotidae or eudicotyledons are a clade A clade (; from grc, , ''klados'', "branch"), also known as a monophyletic group or natural group, is a group of organisms that are monophyly, monophyletic—that is, composed of a com ...
are the largest clade within the dicotyledons. They are distinguished from all other flowering plants by the structure of their
pollen File:Pollen Tube.svg, Pollen Tube Diagram Pollen is a powdery substance consisting of pollen grains which are Sporophyte, microsporophytes of spermatophyta, seed plants, which produce male gametes (sperm cells). Pollen grains have a hard coat ma ...

pollen
. Other dicotyledons and monocotyledons have
monosulcate Pollen Tube Diagram Pollen is a powdery substance consisting of pollen grains which are male microgametophytes of seed plants, which produce male gamete A gamete ( /ˈɡæmiːt/; from Ancient Greek Ancient Greek includes the forms o ...
pollen, or forms derived from it, whereas eudicots have tricolpate pollen, or derived forms, the pollen having three or more pores set in furrows called colpi.


Comparison with monocotyledons

Aside from
cotyledon File:Germination-en.svg, 335px, Schematic of epigeal vs hypogeal germination A cotyledon (; ; ; , gen. (), ) is a significant part of the embryo within the seed of a plant, and is defined as "the embryonic leaf in seed-bearing plants, one o ...
number, other broad differences have been noted between
monocots Monocotyledons (), commonly referred to as monocots, (Lilianae ''sensu'' Chase & Reveal) are grass and grass-like flowering plants (angiosperms), the seeds of which typically contain only one Embryo#Plant embryos, embryonic leaf, or cotyledon. The ...

monocots
and dicots, although these have proven to be differences primarily between monocots and
eudicots The eudicots, Eudicotidae or eudicotyledons are a clade A clade (; from grc, , ''klados'', "branch"), also known as a monophyletic group or natural group, is a group of organisms that are monophyly, monophyletic—that is, composed of a com ...
. Many early-diverging dicot groups have monocot characteristics such as scattered
vascular bundles Cross section of celery stalk, showing vascular bundles, which include both phloem and xylem File:Leitbuendel zea mays.jpg, Detail of vascular bundle: closed, collateral vascular bundles of the stem axis of ''Zea mays'' A vascular bundle is a ...
, trimerous flowers, and non-tricolpate
pollen File:Pollen Tube.svg, Pollen Tube Diagram Pollen is a powdery substance consisting of pollen grains which are Sporophyte, microsporophytes of spermatophyta, seed plants, which produce male gametes (sperm cells). Pollen grains have a hard coat ma ...

pollen
. In addition, some monocots have dicot characteristics such as reticulated leaf veins.


Classification


Phylogeny

The consensus
phylogenetic tree , based on completely sequenced genomes. A phylogenetic tree (also phylogeny or evolutionary tree Felsenstein J. (2004). ''Inferring Phylogenies'' Sinauer Associates: Sunderland, MA.) is a branching diagram or a tree showing the evolution ...

phylogenetic tree
used in the
APG IV systemAPG is an abbreviation with several different meanings: * Aberdeen Proving Ground, a United States Army installation in Aberdeen, Maryland, also ** Phillips Army Airfield, the airfield of the above, from its IATA airport code * Aboriginal Provision ...
shows that the group traditionally treated as the dicots is
paraphyletic In taxonomy, a group is paraphyletic if it consists of the group's last common ancestor and all descendants of that ancestor excluding a few—typically only one or two—Monophyly, monophyletic subgroups. The group is said to be paraphyleti ...
to the monocots:


Historical

Traditionally the dicots have been called the Dicotyledones (or Dicotyledoneae), at any rank. If treated as a class, as in the
Cronquist systemCronquist can refer to: * Arthur J. Cronquist, a North American botanist (1919–1992). * The Cronquist system, a system attributed to Arthur J. Cronquist. Many authors use their own variation of this system, which they also refer to as the ...
, they could be called the Magnoliopsida after the
type genus Type may refer to: Science and technology Computing * Typing Typing is the process of writing or inputting text by pressing keys on a typewriter, computer keyboard, cell phone, or calculator. It can be distinguished from other means of text inpu ...
''
Magnolia ''Magnolia'' is a large genus of about 210The number of species in the genus ''Magnolia'' depends on the taxonomic view that one takes up. Recent molecular and morphology (biology), morphological research shows that former genera ''Talauma'', ''D ...

Magnolia
''. In some schemes, the eudicots were treated as a separate
class Class or The Class may refer to: Common uses not otherwise categorized * Class (biology), a taxonomic rank * Class (knowledge representation), a collection of individuals or objects * Class (philosophy), an analytical concept used differently f ...
, the
Rosopsida Rosopsida (August Batsch, Batsch, 1788) is a botanical name for a group of flowering plants recognized at the rank (botany), rank of class. The name is derived from that of the included family Rosaceae. As used in the Reveal system it is a subset of ...
(type genus ''Rosa''), or as several separate classes. The remaining dicots ( palaeodicots or basal angiosperms) may be kept in a single
paraphyletic In taxonomy, a group is paraphyletic if it consists of the group's last common ancestor and all descendants of that ancestor excluding a few—typically only one or two—Monophyly, monophyletic subgroups. The group is said to be paraphyleti ...

paraphyletic
class, called
Magnoliopsida Magnoliopsida is a valid botanical name for a class of flowering plant The flowering plants, also known as Angiospermae (), or Magnoliophyta (), are the most diverse group of Embryophyte, land plants, with 64 Order(biology), orders, 416 Family ...
, or further divided. Some botanists prefer to retain the dicotyledons as a valid class, arguing its practicality and that it makes evolutionary sense.


APG vs. Cronquist

The following lists show the orders in the Angiosperm Phylogeny Group
APG IV systemAPG is an abbreviation with several different meanings: * Aberdeen Proving Ground, a United States Army installation in Aberdeen, Maryland, also ** Phillips Army Airfield, the airfield of the above, from its IATA airport code * Aboriginal Provision ...
traditionally called dicots, together with the older
Cronquist systemCronquist can refer to: * Arthur J. Cronquist, a North American botanist (1919–1992). * The Cronquist system, a system attributed to Arthur J. Cronquist. Many authors use their own variation of this system, which they also refer to as the ...
.


Dahlgren and Thorne systems

In the Dahlgren and the 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. For each system, only the superorders are listed. The sequence of each system has been altered to pair corresponding taxa, although circumscription of superorders with the same name is not always the same. The Thorne system (1992) as depicted by Reveal is:


See also

* Calyciflorae


References


External links


World list of dicot species (aka 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
{{Authority control Historically recognized angiosperm taxa