Edited by Ho Dinh Hai Long An - Vietnam Updated: 25/4/2015
1- Introduction to the Order Poales
1.1- Overview The Poales are a large order of flowering plants in the monocotyledons, and includes families of plants such as the grasses, bromeliads, and sedges. The earliest fossils attributed to the Poales date to the late Cretaceous period about 66 million years ago, though some studies (e.g., Bremer, 2002) suggest the origin of the group may extend to nearly 115 million years ago, likely in South America. The earliest known fossils include pollen and fruits. The flowers are typically small, enclosed by bracts, and arranged in inflorescences (except in the genus Mayaca, with solitary terminal flowers). The flowers of many species are wind pollinated; the seeds usually contain starch.
1.2- Scientific classification + Early Systems In earlysystems, an order including the grass family did not go by the name Poales but by adescriptive botanical namesuch asGlumaceaein theBentham & Hooker system(third volume, 1883), theHutchinson system (first edition, first volume, 1926), the Glumifloraein the Wettstein system(last revised 1935) and the Graminalesin theEngler system(update of 1964). The morphology-basedCronquist systemdid not include an order named Poales, assigning these families to the ordersBromeliales,Cyperales,Hydatellales,Juncales, RestionalesandTyphales. The Poales are the most economically important order of monocots and possibly the most important order of plants in general. Within the order, by far the most important family economically is the family of grasses (Poaceae, syn. Gramineae), which includesbarley, maize,millet,rice, andwheat. It is also the largest family in the order, far outnumbering the other families: Poaceae: 12,070 species Cyperaceae: 5,500 species Bromeliaceae: 3,170 species Eriocaulaceae: 1,150 species + The Earlier APG System (1998) The earlierAPG 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 Bromeliaceae and Mayacaceae in the order): Order Poales Family Anarthriaceae Family Centrolepidaceae Family Cyperaceae Family Ecdeiocoleaceae Family Eriocaulaceae Family Flagellariaceae Family Hydatellaceae (now transferred out of the monocots; recently discovered to be an 'early-diverging' lineage of flowering plants.) Family Joinvilleaceae Family Juncaceae Family Poaceae FamilyPrioniaceae Family Restionaceae Family Sparganiaceae (now included in family Typhaceae) Family Thurniaceae Family Typhaceae Family Xyridaceae + The APG III System (2009) TheAPG III system(2009) accepts the order and places it in a clade calledcommelinids, in themonocots.Sixteen plant families are currently recognized by botanists to be part of Order Poales: Order Poales 1- FamilyAnarthriaceae 2- FamilyBromeliaceae 3- FamilyCentrolepidaceae 4- FamilyCyperaceae 5- FamilyEcdeiocoleaceae 6- FamilyEriocaulaceae 7- FamilyFlagellariaceae 8- FamilyJoinvilleaceae 9- FamilyJuncaceae 10- FamilyMayacaceae 11- FamilyPoaceae 12- FamilyRapateaceae 13- FamilyRestionaceae 14- FamilyThurniaceae 15- FamilyTyphaceae 16- FamilyXyridaceae
2- The Families in Order Poales (depending on APG III System)
2.1- Family Anarthriaceae + Overview TheAngiosperm Phylogeny Group (APG system, of 1998) and the APG II system of 2003, does recognize this family, and assigns it to the orderPoalesin the cladecommelinids, in the monocots. The family Anarthriaceae is accepted in theAngiosperm Phylogeny Group's classification system,APG III system, but is not considered a separate family in many other taxonomic systems.The three genera are herbaceous but differ greatly in characteristics. + Genera The family contains three genera and 10 species, and is found inSouthwest Australia. Three genera: 1- Genus Anarthria. 2- GenusHopkinsia 3- Genus Lyginia.
2.2- Family Bromeliaceae + Overview The Bromeliaceae (the bromeliads) are a family of monocotflowering plants of around 3,170 species native mainly to the tropicalAmericas, with a few species found in the American subtropics and one in tropical west Africa, Pitcairnia feliciana. They are among the basal families within the Poales and are unique because they are the only family within the order that has septal nectaries and inferior ovaries. These inferior ovaries characterize the Bromelioideae, a subfamily of the Bromeliaceae. The family includes both epiphytes, such as Spanish moss (Tillandsia usneoides), and terrestrial species, such as the pineapple (Ananas comosus). Many bromeliads are able to store water in a structure formed by their tightly-overlapping leaf bases. However, the family is diverse enough to include the tank bromeliads, grey-leaved epiphyteTillandsia species that gather water only from leaf structures called trichomes, and a large number of desert-dwelling succulents. The largest bromeliad is Puya raimondii, which reaches 3-4 m tall in vegetative growth with a flower spike 9-10 m tall, and the smallest is Spanish moss. + Subfamilies The family Bromeliaceae is organized into three subfamilies: 1- Bromelioideae (32 genera, 861 species) 2- Pitcairnioideae (16 genera, 1030 species) 3- Tillandsioideae (9 genera, 1277 species)
2.4- Family Cyperaceae + Overview TheCyperaceaeare afamilyof monocotyledonousgraminoidflowering plants known assedges, which superficially resembl egrassesorrushes. The family is large, with some 5,500 species described in about 109genera, the largest being theCarexgenus of "true sedges"with over 2,000 species.These species are widely distributed, with the centers of diversity for the group occurring in tropical Asia and tropicalSouth America. While sedges may be found growing in almost all environments, many are associated withwetlands, or with poor soils.Ecological communitiesdominated by sedges are known as sedgelands. Features distinguishing members of the sedge family from grasses or rushes are stems with triangular cross-sections (with occasional exceptions) and leaves that are spirally arranged in three ranks (grasses have alternate leaves forming two ranks). Some well-known sedges include the water chestnut (Eleocharis dulcis) and the papyrus sedge (Cyperus papyrus), from which the Ancient Egyptianwriting material was made. This family also includes cotton-grass (Eriophorum), spike-rush (Eleocharis), sawgrass (Cladium), nutsedge or nutgrass (Cyperus rotundus, a common lawn weed), and white star sedge (Rhynchospora colorata).
2.7- Family Flagellariaceae + Overview The family Flagellariaceae has historically been recognized by few taxonomists. TheAPG II system, of 2003 (unchanged from theAPG system, 1998), does recognize such a family, and assigns it to the orderPoalesin the clade commelinids, in themonocots. Robust, bamboo-like, climbing herbs. Leaves linear, grass-like, with firm, coiled apices by which the plant climbs. Flowers usually in panicles, bisexual with 6 membranous perianth parts in 2 whorls, and 6 stamens. Fruit a drupe with a bony 'stone' and a thin, fleshy outer layer. This small family from the Old World tropics. + Taxonomy - Genus: Flagellariais the sole genus in theflowering plantfamilyFlagellariaceae. - Species: Flagellariaconsists of only four known species, found in the tropical and subtropical regions of Asia,Africa, Australia, and various island of the PacificandIndian Oceans. 1- Flagellaria giganteaHook.f.-Bismarck Archipelago,Samoa,Niue,Fiji 2- Flagellaria guineensisSchumach.- tropical and southernAfrica,Madagascar 3- Flagellaria indicaL.-Asia,Papuasia, Australia,Micronesia,Madagascar, Seychelles,Mauritius,Réunion,Rodrigues Island,Mozambique,Tanzania 4- Flagellaria neocaledonicaSchltr.-Solomon Islands,New Caledonia,Fiji
2.8- Family Joinvilleaceae + Overview TheJoinvilleaceaeare afamilyofflowering plants. TheAPG II system, of 2003 (unchanged from theAPG system, 1998) assigns it to the orderPoalesin the cladecommelinidsin the monocots. The family consists of one genus with four currently accepted species, distributed from theMalay Peninsulato theCaroline Islandsand high islands in thePacific Ocean. It is evolutionarily significant as arelictualgroup closely related tograsses. They closely resemble large grass plants, in both general appearance and microanatomy, but possess fleshy fruits. + Taxonomy - Genus The family consists of one genus: Joinvillea - Species 1- Joinvillea ascendensGaudich. ex Brongn. & Gris - Hawaiian Islands. 2- Joinvillea borneensisBecc. - WesternMalesiato Caroline Islands. 3- Joinvillea bryaniiChristoph.Samoa. 4- Joinvillea plicata(Hook.f.) Newell & B.C.Stone- Solomon Islands to New Caledonia and southwest Pacific
2.9- Family Juncaceae - Rush family + Overview The Juncaceae, the rush family, are a monocotyledonous family of flowering plants of eight genera and about 400 species. Members of the Juncaceae are slow-growing, rhizomatous, herbaceous plants, and they may superficially resemble grasses and sedges. They often grow on infertile soils in a wide range of moisture conditions. The most well-known and largest genus is Juncus. Most of the Juncus species grow exclusively in wetland habitats. A few rushes are annuals, but most are perennials. The leaves are evergreen and well-developed in a basal aggregation on an erect stem. They are alternate and tristichous (i.e., with three rows of leaves up the stem, each row of leaves arising one-third of the way around the stem from the previous leaf). Only in the genus Distichia are the leaves distichous. The rushes of the genus Juncus have flat, hairless leaves or cylindrical leaves. The leaves of the wood-rushes of the genus Luzula are always flat and bear long white hairs. The plants are hermaphroditic or, rarely, dioecious. The small flowers are arranged ininflorescences of loose cymes, but also in rather dense heads or corymbs at the top of the stem or at its side. This family typically has reducedperianth segments called tepals. These are usually arranged in two whorls, each containing three thin, papery tepals. They are not bright or flashy in appearance, and their color can vary from greenish to whitish, brown, purple, black, or hyaline. The three stigmas are in the center of the flowers. As is characteristic of monocots, all of the flower parts appear in multiples of three. The fruit is usually a nonfleshy, three-sectioned dehiscentcapsule containing many seeds. + Genera: 1- Andesia 2- Distichia 3- Juncus - Rush 4- Luzula - Woodrush 5- Marsippospermum 6- Oxychloe 7- Patosia 8- Rostkovia.
2.10- Family Mayacaceae + Overview TheMayacaceaeare afamilyof monocotyledonousflowering plantsin the order Poales, commonly known as thepipewort family. The family is small, with 7-8 species described in 1 genera. + Taxonomy - Genus The familyMayacaceaehas only one genus: Mayaca Mayacais agenusofflowering plants, often placed in its ownfamily, theMayacaceae.In theAPG II systemof 2003, it is assigned to the orderPoalesin the cladecommelinids. The Cronquist system, of 1981, also recognised such a family and placed it in the orderCommelinales in the subclassCommelinidae. The group is widely distributed inLatin America fromMexicotoArgentina, as well as in theWest Indies, the southeasternUnited States, and centralAfrica. - Species of the Genus Mayaca Eighteen or so species names have been proposed, but only 6 are generally accepted as distinct. 1- Species Mayaca baumiiGürke- In Congo-Brazzabille, Zaïre, Angola, Zambia 2- Species Mayaca fluviatilisAubl. - In southeastern United States from Texas to North Carolina; West Indies (Cuba, Jamaica, Trinidad); Latin America from central Mexico to Argentina 3- Species Mayaca kunthiiSeub. in C.F.P.von Martius & auct. suc. - In Venezuela, Brazil, Uruguay 4- Species Mayaca longipesMart.exSeub. - In Venezuela, Brazil, Colombia, the Guianas 5- Species Mayaca madida(Vell.)Stellfeld - In Costa Rica, Venezuela, Brazil, Colombia, the Guianas, Peru, Ecuador, Bolivia, Argentina 6- Species Mayaca wrightiiGriseb. - In Cuba
2.11- Family Poaceae + Overview The Poaceae (also called Gramineae or true grasses) are a large and nearly ubiquitous family of monocotyledonousflowering plants. With more than 10,000 domesticated and wild species, the Poaceae are the fifth-largest plant family, following the Asteraceae, Orchidaceae, Fabaceae, and Rubiaceae. Though commonly called "grasses", seagrasses, rushes, and sedges fall outside this family. The rushes and sedges are related to the Poaceae, being members of the orderPoales, but the seagrasses are members of order Alismatales. Grasslands are estimated to constitute 20% of the vegetation cover of the Earth. Poaceae live in many other habitats, including wetlands, forests, and tundra. Domestication of poaceous cereal crops such as maize (corn), wheat, rice, barley, and millet lies at the foundation of sedentary living and civilization around the world, and the Poaceae still constitute the most economically important plant family in modern times, providing forage, building materials (bamboo, thatch) and fuel (ethanol), as well as food. + Classification Recent classifications of the grass family recognize 12 subfamilies and a small number of taxa with uncertain placements: 1- Subfamily Anomochlooideae (including 2 tribes and 2 genera) 2- Subfamily Aristidoideae (including 1 tribe and 3 genera) 3- Subfamily Arundinoideae (including 1 tribe and 3 genera) 4- Subfamily Bambusoideae (including 13 tribes and 70-91 genera) 5- Subfamily Chloridoideae (including 6 tribes and 140 genera) 6- Subfamily Danthonioideae (including 1 tribe and 24 genera) 7- Subfamily Ehrhartoideae (including 4 tribes and 21 genera, 111 species) 8- Subfamily Micrairoideae (including 3 tribes and 8 genera, 185 species) 9- Subfamily Panicoideae (including 6 tribes and 257 genera) 10- Subfamily Pharoideae (including 1 tribe and 2 genera) 11- Subfamily Pooideae (including 12-13 tribes) 12- Subfamily Puelioideae (including 2 tribes and 2 genera)
2.13- Family Restionaceae + Overview TheRestionaceae, also calledrestiadsandrestios, are afamilyof perennial, evergreen rush-likeflowering plantsnative to the Southern Hemisphere; they vary from 10 cm to 3 m in height. Based on evidence from fossil pollens, the Restionaceae likely originated more than 65 million years ago during theLate Cretaceous period, when the southern continents were still part ofGondwana. The family consists of tufted or rhizomatous, herbaceous plants,rush-likeorbamboo-likein overall appearance. They belong to a group of monocotyledonsthat includes several similar families, such as thesedges,rushes, andtrue grasses. They have green, photosynthetic stems and leaves that have been reduced to sheaths. Their flowers are extremely small and in spikelets, which in turn make up the inflorescences. Male and female flowers are on separate plants and, like grasses, are wind-pollinated. Plants in the family are distributed on all the southern continents -South America(1 sp., Apodasmia chilensis),Africasouth of the Equator and includingMadagascar(about 330 spp.) andAustralia(about 150 spp.) - inNew Zealand(four spp.) and widely distributed in Southeast Asia(one sp.). + Classification The Family Restionaceae has been recognized by most taxonomists. TheCronquist systemof 1981 also recognized this family and placed it in the order Restionales, in the subclassCommelinidaein classLiliopsidain divisionMagnoliophyta. TheAPG II systemof 2003 (unchanged from theAPG system, 1998), recognizes this family and assigns it to the orderPoales, in the cladecommelinidsof themonocots. The AP-Website (May 2006) assumes 58 genera and 520 species, which agrees well with the Flora of China.
2.14- Family Thurniaceae + Overview TheThurniaceaeare afamilyofflowering plants. Thebotanical namehas been recognized by most taxonomists. TheWettstein system, last updated in 1935, placed the family in orderLiliiflorae. TheCronquist systemof 1981 also recognized such a family and placed it in the orderJuncalesin the subclassCommelinidaein classLiliopsidain divisionMagnoliophyta. This represents a slight change from theAPG system, 1998, which treated the two genera as each constituting their own family (Prioniaceaeand Thurniaceae), both placed in the order Poales. TheAPG II system, of 2003, also recognizes such a family, and assigns it to the orderPoalesin the cladecommelinids, in themonocots. + Genera The family consists of two genera, totalling only a few species, perennial plants of wet habitats in South America.
2.16- Family Xyridaceae + Overview TheXyridaceaeare afamilyofflowering plants. Thebotanical namehas been recognized by many taxonomists and is known as the yellow-eyed grass family. TheWettstein system, last updated in 1935, placed the family in orderEnantioblastae. TheCronquist systemof 1981 also recognized such a family and placed it in the order Commelinalesin the subclassCommelinidaein classLiliopsidain divisionMagnoliophyta. TheAPG II system, of 2003 (unchanged from the APG systemof 1998), also recognizes this family, and assigns it to the orderPoalesin the clade commelinids, in themonocots. This treatment in APG II represents a slight change from the APG system of 1998, which had recognized the family Abolbodaceaefor some of the plants included here; that family was unplaced as to order, but was assigned to this same clade (although APG used the spelling "commelinoids"). + Taxonomy The family contains almost 300 species in five genera, but most of the species are found in the genusXyris(see alsoAbolboda). The species are mostly tropical and subtropical. Xyris torta, twisted yellow-eyed grass, is on Minnesota'sendangered specieslist. Genera: Abolboda Achlyphila Aratitiyopea Orectanthe Xyris .