Poales
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Poales is an order of flowering plants in the monocotyledons, and includes families of plants such as the grasses, bromeliads, and sedges.
Recent studies (Bremer, 2000) place the origin of the Poales in South America nearly 115 million years ago. The earliest known fossils include pollen and fruits that have been dated to the late Cretaceous. The flowers are typically small, enclosed by bracts, and arranged in an inflorescence (except in the genus Mayaca, with solitary terminal flowers). The flowers of many species are wind pollinated; the seeds usually contain starch.
The APG II system (2003) accepts the order and places it in clade commelinids, in the monocots. It uses this circumscription:
- order Poales
- family Anarthriaceae
- family Bromeliaceae
- family Centrolepidaceae
- family Cyperaceae
- family Ecdeiocoleaceae
- family Eriocaulaceae
- family Flagellariaceae
- family Hydatellaceae (since transferred out of the monocots)
- family Joinvilleaceae
- family Juncaceae
- family Mayacaceae
- family Poaceae
- family Rapateaceae
- family Restionaceae
- family Sparganiaceae
- family Thurniaceae
- family Typhaceae
- family Xyridaceae
The APG system (1998) adopted the same placement, although it used the spelling "commelinoids", and used the following circumscription (i.e., it did not include the plants in families Abolbodaceae, Bromeliaceae and Mayacaceae in the order):
- order Poales
- family Anarthriaceae
- family Centrolepidaceae
- family Cyperaceae
- family Ecdeiocoleaceae
- family Eriocaulaceae
- family Flagellariaceae
- family Hydatellaceae
- family Joinvilleaceae
- family Juncaceae
- family Poaceae
- family Prioniaceae
- family Restionaceae
- family Sparganiaceae
- family Thurniaceae
- family Typhaceae
- family Xyridaceae
The Cronquist system did not include an order named Poales, assigning these families to the orders Bromeliales, Cyperales, Hydatellales, Juncales, Restionales and Typhales.
In early systems an order including the grass family did not go by the name Poales but by a descriptive botanical name such as Graminales in the Engler system (update of 1964) and in the Hutchinson system (first edition, first volume, 1926), Glumiflorae in the Wettstein system (last revised 1935) or Glumaceae in the Bentham & Hooker system (third volume, 1883).
Uses
By far the most important family economically is the family of grasses (Poaceae, syn. Gramineae), which includes barley, maize, millet, rice, and wheat. It is also the largest family in the order, far outnumbering its competitors:
- Poaceae: 12,000 species
- Cyperaceae: 5,000 species
- Bromeliaceae: 1,400 species
- Eriocaulaceae: 1,150 species
References
- Bremer, K. (2000). Gondwanan Evolution of the Grass Alliance of Families (Poales). Evolution 56: 1374-1387. [Available online: Abstract ]
- Judd, W. S., C. S. Campbell, E. A. Kellogg, P. F. Stevens, M. J. Donoghue (2002). Plant Systematics: A Phylogenetic Approach, 2nd edition. pp. 276-292 (Poales). Sinauer Associates, Sunderland, Massachusetts. ISBN 0-87893-403-0 .
- Linder, H. Peter and Paula J. Rudall. 2005. Evolutionary History of the Poales. Annual Review of Ecology, Evolution, and Systematics 36: 107-124.
- Small, J. K. (1903). Flora of the Southeastern United States, 48. New York, U.S.A.