Difference between revisions of "Dicotyledon" - New World Encyclopedia

From New World Encyclopedia
(Fixed taxobox)
(updated to most recent Wikipedia version)
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{{Taxobox_begin | color = lightgreen | name = Magnoliopsida (Dicotyledons)}}
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{{Taxobox
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{{Taxobox_image | image = [[Image:magnolia.jpg|250px]]  | caption = Magnolia [[flower]]}}
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| color = lightgreen
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{{Taxobox_begin_placement | color = lightgreen }}
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| name = Magnoliopsida (Dicotyledons)
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{{Taxobox_regnum_entry | taxon = [[Plant]]ae}}
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| image = magnolia.jpg
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{{Taxobox_divisio_entry | taxon = [[Flowering plant|Magnoliophyta]]}}
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| image_width = 250px
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{{Taxobox classis entry | taxon = '''Magnoliopsida'''}}<br/>{{Taxobox authority new | authority = [[Alexandre Brongniart|Brongniart]]}}
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| image_caption = [[Magnolia]] [[flower]]
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{{Taxobox_end_placement}}
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| regnum = [[Plant]]ae
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{{Taxobox_section_subdivision | color = lightgreen | plural_taxon = [[Order (biology)|Orders]]}}
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| divisio = [[Flowering plant|Magnoliophyta]]
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see text
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| classis = '''Magnoliopsida'''
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{{Taxobox_end}}
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| classis_authority = [[Alexandre Brongniart|Brongniart]]
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| subdivision_ranks = [[Order (biology)|Orders]]
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| subdivision =
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See text.
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}}
 
[[Image:Young castor bean plant showing prominent cotyledons.jpg|left|thumb|200px|Young [[castor oil plant]] showing its prominent two embryonic leaves ([[cotyledons]]), that differ from the adult leaves]]
 
[[Image:Young castor bean plant showing prominent cotyledons.jpg|left|thumb|200px|Young [[castor oil plant]] showing its prominent two embryonic leaves ([[cotyledons]]), that differ from the adult leaves]]
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'''Dicotyledons''' or '''"dicots"''' is a name for a group of [[flowering plant]]s whose [[seed]] typically contains two embryonic leaves or [[cotyledon]]s. There are some 199,350 [[species]] within this group [http://www.redlist.org/info/tables/table1]. Flowering plants that are not dicotyledons are [[monocotyledon]]s, typically having one embryonic leaf.
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'''Dicotyledons''' or '''"dicots"''' is a name for a group of [[flowering plant]]s whose [[seed]] typically contains two embryonic leaves or [[cotyledon]]s. There are around 199,350 [[species]] within this group [http://www.redlist.org/info/tables/table1]. Flowering plants that are not dicotyledons are [[monocotyledon]]s, typically having one embryonic leaf.
  
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It is now accepted, thanks to the [[Angiosperm Phylogeny Group]], that monocotyledons evolved from within the dicotyledons, and as such the latter form a [[paraphyletic]] group. This means that dicotyledons no longer are regarded as a "good" group, and the names "dicotyledons" and "dicots" are no longer to be used, at least in a taxonomic sense. The vast majority of the former dicots, however, form a [[monophyletic]] group called the [[eudicots]] or tricolpates. These may be distinguished from all other flowering plants by the structure of their [[pollen]]. Other dicotyledons and monocotyledons have [[monosulcate]] 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.
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The dicotyledons no longer are regarded as a "good" group, and the names "dicotyledons" and "dicots" are no longer to be used at least in a taxonomic sense. The vast majority of the former dicots, however, form a [[monophyletic]] group called the [[eudicots]] or tricolpates. These may be distinguished from all other flowering plants by the structure of their [[pollen]]. Other dicotyledons and monocotyledons have [[monosulcate]] 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.
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Traditionally the dicots have been called the Dicotyledones (or Dicotyledoneae), at any rank. If treated as a class, as in the Cronquist system, they may be called the Magnoliopsida after the [[biological type|type genus]] ''[[Magnolia]]''. In some schemes, the eudicots are treated as a separate class, the Rosopsida (type genus ''Rosa''), or as several separate classes. The remaining dicots ([[palaeodicots]]) may be kept in a single paraphyletic class, called Magnoliopsida, or further divided.
 
  
 +
Traditionally the dicots have been called the Dicotyledones (or Dicotyledoneae), at any rank. If treated as a class, as in the Cronquist system, they may be called the Magnoliopsida after the [[type (botany)|type genus]] ''[[Magnolia]]''. In some schemes, the eudicots are treated as a separate class, the [[Rosopsida]] (type genus ''Rosa''), or as several separate classes. The remaining dicots ([[palaeodicots]]) may be kept in a single paraphyletic class, called Magnoliopsida, or further divided.
 +
<div style="clear: both"></div>
 
The following lists are of the orders formerly placed in the dicots, giving their new placement in the [[Angiosperm Phylogeny Group|APG]]-system and that under the older [[Cronquist system]], which is still in wide use.
 
The following lists are of the orders formerly placed in the dicots, giving their new placement in the [[Angiosperm Phylogeny Group|APG]]-system and that under the older [[Cronquist system]], which is still in wide use.
 
<p clear="right">
 
<p clear="right">
 
<table width=100%><tr>
 
<table width=100%><tr>
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<td>'''[[Angiosperm Phylogeny Group| APG II]]'''</td>
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<td>'''[[Angiosperm Phylogeny Group|APG II]]'''</td>
 
<td>'''[[Cronquist system]]'''</td>
 
<td>'''[[Cronquist system]]'''</td>
 
</tr><tr valign="top">
 
</tr><tr valign="top">
 
<td>
 
<td>
 
<!-- Phylogenetic —>
 
<!-- Phylogenetic —>
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'[[Palaeodicots]]': basal orders
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[[Amborellaceae]]
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* [[Amborella]]les
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* [[Nymphaeales]]
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[[Nymphaeaceae]] [+ [[Cabombaceae]]]
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* [[Austrobaileyales]]
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* [[Chloranthaceae|Chloranthales]]
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[[Austrobaileyales]]
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* [[Ceratophyllum|Ceratophyllales]]
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'Palaeodicots': [[Magnoliid]] complex
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[[Chloranthaceae]]
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 +
[[Ceratophyllales]]
 +
 
 +
[[Magnoliid]]s
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* [[Canellales]]
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* [[Piperales]]
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* [[Laurales]]
 
* [[Magnoliales]]
 
* [[Magnoliales]]
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* [[Laurales]]
 
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* [[Piperales]]
 
 
* [[Aristolochiaceae|Aristolochiales]]
 
* [[Aristolochiaceae|Aristolochiales]]
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* [[Canellales]]
 
 
'''[[Eudicots]]'''
 
'''[[Eudicots]]'''
  
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</td></tr></table>
 
</td></tr></table>
  
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===Compared to [[Monocotyledons]]===
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===Compared to Monocotyledons===
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The schoolbooks list the differences between monocotyledons and dicotyledons as follows (obviously this is a broad sketch only, not to be taken literally):
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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. In addition, some monocots have "dicot" characteristics such as reticulated leaf veins.
  
 
'''Seeds:''' The embryo of the monocot has one [[cotyledon]] while the embryo of the dicot has two.
 
'''Seeds:''' The embryo of the monocot has one [[cotyledon]] while the embryo of the dicot has two.
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'''Flowers:''' The flower parts in monocots are multiples of three while in dicots are multiples of four or five.
 
'''Flowers:''' The flower parts in monocots are multiples of three while in dicots are multiples of four or five.
  
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'''Stems:''' In monocots, the [[Plant stem|stem]] [[vascular]] [[bundles]] are [[scattered]], while in dicots they are in a [[wiktionary:ring|ring]].
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'''Stems:''' In monocots, the [[Plant stem|stem]] [[vascular bundle]]s are [[scattered]], while in dicots they are in a [[wiktionary:ring|ring]].
 +
 
 +
'''Secondary growth:''' In monocots, stems rarely show secondary growth; in dicots, stems frequently have secondary growth.
  
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'''Pollen:''' In monocots, pollen has one [[furrow]] or [[pore]] while in dicots they have three.
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'''Pollen:''' In monocots, pollen has one [[furrow]] or [[stoma|pore]] while in dicots they have three.
  
 
'''Roots:''' The roots are [[adventitious]] in monocots, while in dicots they develop from the [[radicle]].
 
'''Roots:''' The roots are [[adventitious]] in monocots, while in dicots they develop from the [[radicle]].
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{{credit|61187163}}
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{{credit|118849612}}
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[[Category:Life sciences]]
 
[[Category:Life sciences]]

Revision as of 21:58, 2 April 2007

Magnoliopsida (Dicotyledons)
Magnolia flower
Scientific classification
Kingdom: Plantae
Division: Magnoliophyta
Class: Magnoliopsida
Brongniart
Orders

See text.

Young castor oil plant showing its prominent two embryonic leaves (cotyledons), that differ from the adult leaves

Dicotyledons or "dicots" is a name for a group of flowering plants whose seed typically contains two embryonic leaves or cotyledons. There are around 199,350 species within this group [1]. Flowering plants that are not dicotyledons are monocotyledons, typically having one embryonic leaf.

The dicotyledons no longer are regarded as a "good" group, and the names "dicotyledons" and "dicots" are no longer to be used at least in a taxonomic sense. The vast majority of the former dicots, however, form a monophyletic group called the eudicots or tricolpates. These may be distinguished from all other flowering plants by the structure of their pollen. Other dicotyledons and monocotyledons have monosulcate 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.

Traditionally the dicots have been called the Dicotyledones (or Dicotyledoneae), at any rank. If treated as a class, as in the Cronquist system, they may be called the Magnoliopsida after the type genus Magnolia. In some schemes, the eudicots are treated as a separate class, the Rosopsida (type genus Rosa), or as several separate classes. The remaining dicots (palaeodicots) may be kept in a single paraphyletic class, called Magnoliopsida, or further divided.

The following lists are of the orders formerly placed in the dicots, giving their new placement in the APG-system and that under the older Cronquist system, which is still in wide use.

APG II Cronquist system

Amborellaceae

Nymphaeaceae [+ Cabombaceae]

Austrobaileyales

Chloranthaceae

Ceratophyllales

Magnoliids

  • Canellales
  • Piperales
  • Laurales
  • Magnoliales
  • Aristolochiales

Eudicots

Basal eudicots

  • Ranunculales
  • Buxales
  • Trochodendrales
  • Proteales
  • Gunnerales
  • Berberidopsidales
  • Dilleniales
  • Caryophyllales
  • Saxifragales
  • Santalales
  • Vitales

Rosids

Basal rosids

  • Crossosomatales
  • Geraniales
  • Myrtales

Eurosids I

  • Zygophyllales
  • Celastrales
  • Malpighiales
  • Oxalidales
  • Fabales
  • Rosales
  • Cucurbitales
  • Fagales

Eurosids II

  • Brassicales
  • Malvales
  • Sapindales

Asterids

Basal asterids

  • Cornales
  • Ericales

Euasterids I

  • Garryales
  • Solanales
  • Gentianales
  • Lamiales
  • Unplaced: Boraginaceae

Euasterids II

  • Aquifoliales
  • Apiales
  • Dipsacales
  • Asterales

Magnoliopsida

Magnoliidae (mostly basal dicots)

  • Magnoliales
  • Laurales
  • Piperales
  • Aristolochiales
  • Illiciales
  • Nymphaeales
  • Ranunculales
  • Papaverales

Hamamelidae

  • Trochodendrales
  • Hamamelidales
  • Daphniphyllales
  • Didymelales
  • Eucommiales
  • Urticales
  • Leitneriales
  • Juglandales
  • Myricales
  • 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
  • Polygalales
  • Sapindales
  • Geraniales
  • Apiales

Asteridae

  • Gentianales
  • Solanales
  • Lamiales
  • Callitrichales
  • Plantaginales
  • Scrophulariales
  • Campanulales
  • Rubiales
  • Dipsacales
  • Calycerales
  • Asterales

Compared to 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. In addition, some monocots have "dicot" characteristics such as reticulated leaf veins.

Seeds: The embryo of the monocot has one cotyledon while the embryo of the dicot has two.

Flowers: The flower parts in monocots are multiples of three while in dicots are multiples of four or five.

Stems: In monocots, the stem vascular bundles are scattered, while in dicots they are in a ring.

Secondary growth: In monocots, stems rarely show secondary growth; in dicots, stems frequently have secondary growth.

Pollen: In monocots, pollen has one furrow or pore while in dicots they have three.

Roots: The roots are adventitious in monocots, while in dicots they develop from the radicle.

Leaves: In monocots, the major leaf veins are parallel, while in dicots they are reticulated.


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