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== Characters of Asphodeloideae==
== Characters of Asphodeloideae==


Asphodeloideae is distinguished by a general presence of [[anthraquinones]], simultaneous [[microsporogenesis]], atypical [[ovule]]s [[morphology (biology)|morphology]], and the presence of an [[aril]].<ref name=Chase2000>{{cite journal|last=Chase|first=M.W.|coauthors=A. Y. De Bruijn, A. V. Coz, C. Reeves, P.J. Rudall, M. A. T. Johnson, and L. E. Eguiarte|title=Phylogenetics of Asphodelaceae (Asparagales): An analysis of plastid rbcL and trnL-F DNA sequences|journal=Annals of Botany|year=2000|volume=86|issue=5|pages=935-951}}</ref> Asphodeloideae also has a characteristic [[secondary growth]] by means of a secondary thickening [[meristem]].<ref name=Chase2000/> This character, however, is also found in other [[Asparagales]] families, including [[Agavaceae]], [[Iridaceae]], and [[Xanthorrhoeaceae]]. It is confined to [[Asparagales]] among the [[monocots]] and is believed to have evolved independently in most families.<ref name=Chase2000/>
Asphodeloideae is distinguished by a general presence of [[anthraquinones]], simultaneous [[microsporogenesis]], atypical [[ovule]]s [[morphology (biology)|morphology]], and the presence of an [[aril]].<ref name=Chase2000>{{cite journal|last=Chase|first=M.W.|coauthors=A. Y. De Bruijn, A. V. Coz, C. Reeves, P.J. Rudall, M. A. T. Johnson, and L. E. Eguiarte|title=Phylogenetics of Asphodelaceae (Asparagales): An analysis of plastid rbcL and trnL-F DNA sequences|journal=Annals of Botany|year=2000|volume=86|issue=5|pages=935-951}}</ref> Asphodeloideae also has a characteristic [[secondary growth]] by means of a secondary thickening [[meristem]].<ref name=Chase2000/> This character, however, is also found in other taxa in the [[Asparagales]], including [[Agavaceae]], [[Iridaceae]], and [[Xanthorrhoeoideae]]. It is confined to [[Asparagales]] among the [[monocots]] and is believed to have evolved independently in most families.<ref name=Chase2000/>


⚫
==Phylogeny of Asphodeloideae==
The [[Asparagales]] order is divided into two distinct groups, the ‘lower asparagoids’ and the ‘higher asparagoids’, based on differences in [[microsporogenesis]].<ref name=Rudall2002>{{cite journal|last=Rudall|first=P.J.|title=Unique floral structures and iterative evolutionary themes in Asparagales: Insights from a morphological cladistic analysis|journal=Botanical Review|year=2002|volume=68|issue=4|pages=488-430}}</ref><ref name=Chase2000/> The ‘lower asparagoids’ undergo simultaneous microsporogenesis, that is, the second [[meiosis]] of the [[microspore]] follows immediately after the first, without prior [[cytokinesis]].<ref name=Rudall1997>{{cite journal|last=Rudall|first=P. J.|coauthors=C. A. Furness, M. W. Chase, and M. F. Fay|title=Microsporogenesis and pollen sulcus type in Asparagales (Lilianae)|journal=Canadian Journal of Botany-Revue Canadienne De Botanique|year=1997|volume=75|issue=3|pages=408-430}}</ref> The ‘higher asparagoids’ exhibit successive microsporogenesis, in which [[cytokinesis]] occurs prior to the second [[meiosis]].<ref name=Rudall1997/> Asphodelaoideae is a member of the former group, the ‘lower asparagoids’. Successive microsporogenesis is predominate in all [[monocotyledons]], thus making simultaneous microsporogenesis distinctive of the ‘lower families’.<ref name=Furness1999>{{cite journal|last=Furness|first=C. A.|coauthors=P. J. Rudall|title=Microsporogenesis in monocotyledons|journal=Annals of Botany|year=1999|volume=84|issue=4|pages=475-499}}</ref> Other ‘lower asparagoid’ families include [[Orchidaceae]] (the “orchid family”), and [[Iridaceae]] (the “iris family”), among others.<ref name=Rudall2002/>


⚫
There is agreement among many researchers that Asphodeloideae can be further divided into a [[monophyly|monophyletic]] group, Alooideae, and a non-monophyletic group of the remaining [[genera]].<ref name=Smith1991>{{cite journal|last=Smith|first=G. F.|coauthors=B. E. Van Wyk|title=Generic Relationships in the Alooideae (Asphodelaceae)|journal=Taxon|year=1991|volume=40|issue=4|pages=557-581}}</ref><ref name=Chase2000/><ref name=Treutlein2002>{{cite journal|last=Treutlein|first=J.|coauthors=G. F. Smith, B. E. van Wyl, and M. Wink|title=Evidence for the polyphyly of Haworthia (Asphodelaceae subfamily Alooideae; Asparagales) inferred from nucleotide sequences of rbcL, matK, ITS1 and genomic fingerprinting with ISSR-PCR|journal=Plant Biology|year=2003|volume=5|issue=5|pages=513-521}}</ref> Alooideae are mainly [[rosette (botany)|rosulate]] leaf [[succulents]], while the other genera are non-succulent. The genera in Alooideae are centered in southern [[Africa]], while the other genera have mainly a [[Eurasia]]n distribution.<ref name=Treutlein2002/>
⚫
==Genera of Asphodeloideae==

⚫
There is agreement among many researchers that Asphodeloideae can be further divided into a [[monophyly|monophyletic]] group, Alooideae, and a non-monophyletic group of the remaining [[genera]].<ref name=Smith1991>{{cite journal|last=Smith|first=G. F.|coauthors=B. E. Van Wyk|title=Generic Relationships in the Alooideae (Asphodelaceae)|journal=Taxon|year=1991|volume=40|issue=4|pages=557-581}}</ref><ref name=Chase2000/><ref name=Rudall2002/><ref name=Treutlein2002>{{cite journal|last=Treutlein|first=J.|coauthors=G. F. Smith, B. E. van Wyl, and M. Wink|title=Evidence for the polyphyly of Haworthia (Asphodelaceae subfamily Alooideae; Asparagales) inferred from nucleotide sequences of rbcL, matK, ITS1 and genomic fingerprinting with ISSR-PCR|journal=Plant Biology|year=2003|volume=5|issue=5|pages=513-521}}</ref> Alooideae are mainly [[rosette (botany)|rosulate]] leaf [[succulents]], while the other genera are non-succulent. As well, Alooideae is centered in southern [[Africa]], while the other genera have mainly a [[Eurasia]]n distribution.<ref name=Treutlein2002/>


===Alooideae===
===Alooideae===
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The [[inflorescence]] is compacted into a many-flowered spike, or a simple or branched [[raceme]], and is [[apical (anatomy)|apical]] although can seem [[axillary bud|axillary]]. Stems are [[monopodial]] until an inflorescence is formed, and then it becomes [[sympodial]]; this prevents the [[rosette (botany)|rosette]] from dying as in ''[[Agave]]''. Flowers of all taxa within Alooideae are tubular and have a fusion of petaline [[tepals]], although the amount of fusion varies among [[genera]].<ref name=Smith1991/>
The [[inflorescence]] is compacted into a many-flowered spike, or a simple or branched [[raceme]], and is [[apical (anatomy)|apical]] although can seem [[axillary bud|axillary]]. Stems are [[monopodial]] until an inflorescence is formed, and then it becomes [[sympodial]]; this prevents the [[rosette (botany)|rosette]] from dying as in ''[[Agave]]''. Flowers of all taxa within Alooideae are tubular and have a fusion of petaline [[tepals]], although the amount of fusion varies among [[genera]].<ref name=Smith1991/>


Evidence for [[monophyly]] of Alooideae is based on distinctive [[karyotype]] and characteristic leaf morphology. The ''[[Bulbine]]'' group has characteristics of Alooideae, but is not included in the group due to a lack of tubular flowers. ''[[Kniphofia]]'' is considered an [[outgroup (cladistics)|outgroup]] of Alooideae since it has tubular flowers and a fusion of [[perianth]] segments, but it lacks the necessary [[succulent]] leaves.<ref name=Smith1991/>
Evidence for [[monophyly]] of Alooideae is based on distinctive [[karyotype]] and characteristic leaf morphology. The ''[[Bulbine]]'' group has characteristics of Alooideae, but is not included in the group due to a lack of tubular flowers. ''[[Kniphofia]]'' is considered an [[outgroup (cladistics)|outgroup]] of Alooideae since it has tubular flowers and a fusion of [[perianth]] segments, but it lacks [[succulent]] leaves.<ref name=Smith1991/>


====Aloin cells====
====Aloin cells====
The presence of [[aloin]] cells are a distinctive character of the Alooideae sub-group. These cells are present in all Alooideae but are absent in most of the other genera within Asphodeloideae.<ref name=Chase2000/> There is a well-developed cap of thin-walled [[parenchyma]] cells at the [[phloem]] pole of each [[vascular bundle]].<ref name=Smith1991/> Chase posits that they are involved in [[secondary metabolite]] production,<ref name=Chase2000/> but Beaumont suggests that the cells act as a storage tissue for compounds that are synthesized in the surrounding layer of cells.<ref name=Beaumont>{{cite journal|last=Beaumont|first=J.|coauthors=D.F. Cutler, and T. Reynolds|title=Secretory tissues in the East African shrubby aloes|journal=Botanical Journal of the Linnean Society|year=1986|volume=92|issue=4|pages=399-403}}</ref> The [[aloin]] cells are said to produce the characteristic thick exudate that is produced when the succulent leaf of Aloe is severed.<ref name=Beaumont/> The aloin cells produce [[anthraquinone]] and [[chromone]] derivatives,<ref name=Beaumont/> which may be responsible for the medicinal attributes of ''[[Aloe]]''.
The presence of [[aloin]] cells are a distinctive character of the Alooideae. These cells are present in all Alooideae but are absent in most of the other genera within Asphodeloideae.<ref name=Chase2000/> There is a well-developed cap of thin-walled [[parenchyma]] cells at the [[phloem]] pole of each [[vascular bundle]].<ref name=Smith1991/> Chase posits that they are involved in [[secondary metabolite]] production,<ref name=Chase2000/> but Beaumont suggests that the cells act as a storage tissue for compounds that are synthesized in the surrounding layer of cells.<ref name=Beaumont>{{cite journal|last=Beaumont|first=J.|coauthors=D.F. Cutler, and T. Reynolds|title=Secretory tissues in the East African shrubby aloes|journal=Botanical Journal of the Linnean Society|year=1986|volume=92|issue=4|pages=399-403}}</ref> The [[aloin]] cells are said to produce the characteristic thick exudate that is produced when the succulent leaf of Aloe is severed.<ref name=Beaumont/> The aloin cells produce [[anthraquinone]] and [[chromone]] derivatives,<ref name=Beaumont/> which may be responsible for the medicinal attributes of ''[[Aloe]]''.


==List of genera==
==List of genera==

Revision as of 19:58, 31 December 2011

Asphodeloideae
Yellow Asphodel (Asphodeline lutea)
Scientific classification Edit this classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Monocots
Order: Asparagales
Family: Asphodelaceae
Subfamily: Asphodeloideae
genera

see text

Asphodeloideae is a subfamily of the monocot family Xanthorrhoeaceae in the order Asparagales. It has previously been treated as a separate family, Asphodelaceae.[1] The subfamily name is derived from the generic name of the type genus, Asphodelus. Members of group are native to Africa, central and western Europe, the Mediterranean basin, Central Asia and Australia, with one genus (Bulbinella) having some of its species in New Zealand. The greatest diversity occurs in South Africa.

The genera Aloe, Asphodelus and Kniphofia are perhaps the best known genera from their use in horticulture as ornamental plants.

Eremurus robustus

Characters of Asphodeloideae

Asphodeloideae is distinguished by a general presence of anthraquinones, simultaneous microsporogenesis, atypical ovules morphology, and the presence of an aril.[2] Asphodeloideae also has a characteristic secondary growth by means of a secondary thickening meristem.[2] This character, however, is also found in other taxa in the Asparagales, including Agavaceae, Iridaceae, and Xanthorrhoeoideae. It is confined to Asparagales among the monocots and is believed to have evolved independently in most families.[2]

Phylogeny of Asphodeloideae

There is agreement among many researchers that Asphodeloideae can be further divided into a monophyletic group, Alooideae, and a non-monophyletic group of the remaining genera.[3][2][4] Alooideae are mainly rosulate leaf succulents, while the other genera are non-succulent. The genera in Alooideae are centered in southern Africa, while the other genera have mainly a Eurasian distribution.[4]

Alooideae

Alooideae comprises Aloe, Astroloba, Chamaealoe, Gasteria, Haworthia, Lomatophyllum, and Poellnitzia.[2] The genera within Alooideae have several morphological characters that can be readily distinguished in the field, namely the arrangement and type of leaf and inflorescence.

Alooidae leaves are arranged in strongly tufted terminal (in arborescent species, as in Aloe barberae) or basal rosettes and are arranged in distinct ranks. Leaves are succulent and have distinctive white or concolorous tubercules. This is hypothesized to be a derived condition, possibly as a mechanical defensive mechanism to make the leaf less palatable, or to prevent heat damage in arid conditions. As well, the cross-section of the leaves are distinctly shaped in a cymbiform or crescent-shape, which represents a synapomorphy for all Alooideae taxa.[3]

The inflorescence is compacted into a many-flowered spike, or a simple or branched raceme, and is apical although can seem axillary. Stems are monopodial until an inflorescence is formed, and then it becomes sympodial; this prevents the rosette from dying as in Agave. Flowers of all taxa within Alooideae are tubular and have a fusion of petaline tepals, although the amount of fusion varies among genera.[3]

Evidence for monophyly of Alooideae is based on distinctive karyotype and characteristic leaf morphology. The Bulbine group has characteristics of Alooideae, but is not included in the group due to a lack of tubular flowers. Kniphofia is considered an outgroup of Alooideae since it has tubular flowers and a fusion of perianth segments, but it lacks succulent leaves.[3]

Aloin cells

The presence of aloin cells are a distinctive character of the Alooideae. These cells are present in all Alooideae but are absent in most of the other genera within Asphodeloideae.[2] There is a well-developed cap of thin-walled parenchyma cells at the phloem pole of each vascular bundle.[3] Chase posits that they are involved in secondary metabolite production,[2] but Beaumont suggests that the cells act as a storage tissue for compounds that are synthesized in the surrounding layer of cells.[5] The aloin cells are said to produce the characteristic thick exudate that is produced when the succulent leaf of Aloe is severed.[5] The aloin cells produce anthraquinone and chromone derivatives,[5] which may be responsible for the medicinal attributes of Aloe.

List of genera

According to the AP-website as of May 2011, the subfamily includes some 15 genera in up to 800 species. The genera are listed below.[6] Other treatments combine some of these genera into as few as seven.

For a phylogeny of the family see the phylogenetic tree at Xanthorrhoeaceae. [7]

References

  1. ^ Chase, M.W.; Reveal, J.L.; Fay, M.F. (2009), "A subfamilial classification for the expanded asparagalean families Amaryllidaceae, Asparagaceae and Xanthorrhoeaceae", Botanical Journal of the Linnean Society, 161 (2): 132–136, doi:10.1111/j.1095-8339.2009.00999.x {{citation}}: Unknown parameter |lastauthoramp= ignored (|name-list-style= suggested) (help)
  2. ^ a b c d e f g Chase, M.W. (2000). "Phylogenetics of Asphodelaceae (Asparagales): An analysis of plastid rbcL and trnL-F DNA sequences". Annals of Botany. 86 (5): 935–951. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  3. ^ a b c d e Smith, G. F. (1991). "Generic Relationships in the Alooideae (Asphodelaceae)". Taxon. 40 (4): 557–581. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  4. ^ a b Treutlein, J. (2003). "Evidence for the polyphyly of Haworthia (Asphodelaceae subfamily Alooideae; Asparagales) inferred from nucleotide sequences of rbcL, matK, ITS1 and genomic fingerprinting with ISSR-PCR". Plant Biology. 5 (5): 513–521. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  5. ^ a b c Beaumont, J. (1986). "Secretory tissues in the East African shrubby aloes". Botanical Journal of the Linnean Society. 92 (4): 399–403. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  6. ^ Stevens, P.F. (2001 onwards), Angiosperm Phylogeny Website: Asparagales: Asphodeloideae {{citation}}: Check date values in: |year= (help)
  7. ^ Dion S. Devey, Ilia Leitch, Paula J. Rudall, J. Chris Pires, Yohan Pillon, and Mark W. Chase. "Systematics of Xanthorrhoeaceae sensu lato, with an emphasis on Bulbine". Aliso 22(Monocots: Comparative Biology and Evolution):345-351. ISSN 0065-6275.

External links

Wikimedia Commons has media related to Asphodelaceae.
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