Hydrocharitaceae

Hydrocharitaceae is a flowering plant family including 16 known genera with a total of ca 135 known species (Christenhusz & Byng 2016 [2]), that including a number of species of aquatic plant, for instance the tape-grasses, the well known Canadian waterweed and frogbit Hydrocharis morsus-ranae.

Hydrocharitaceae
Common frogbit, Hydrocharis morsus-ranae
Scientific classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Monocots
Order: Alismatales
Family: Hydrocharitaceae
Juss.[1]
Genera

See text

The family includes both fresh water and marine aquatics. They are found throughout the world in a wide variety of habitats, but are primarily tropical.

Description

The species are annual or perennial, with a creeping monopodial rhizome with the leaves arranged in two vertical rows, or an erect main shoot with roots at the base and spirally arranged or whorled leaves. The leaves are simple and usually found submerged, though they may be found floating or partially emerse. As with many aquatics they can be very variable in shape – from linear to orbicular, with or without a petiole, and with or without a sheathing base.

The flowers are arranged in a forked, spathe-like bract or between two opposite bracts. They are usually irregular, though in some case they may be slightly irregular, and either bisexual or unisexual. The perianth segments are in 1 or 2 series of (2–)3 free segments; the inner series when present are usually showy and petal-like. Stamens 1–numerous, in 1 or more series; the inner ones sometimes sterile. Pollen is globular and free but in the marine genera (Thalassia and Halophila) – the pollen grains are carried in chains, like strings of beads. The ovary is inferior with 2–15 united carpels containing a single locule with numerous ovules on parietal placentas which either protrude nearly to the centre of the ovary or are incompletely developed. Fruits are globular to linear, dry or pulpy, dehiscent or more usually indehiscent and opening by decay of the pericarp. Seeds are normally numerous with straight embryos and no endosperm.

Pollination can be extremely specialised.

The most recent phylogenetic treatment of the family recognizes four subfamilies – Hydrocharitoideae (Hydrocharis, Limnobium), Stratiotoideae (Stratiotes), Anacharioideae (Apalanthe, Appertiella, Blyxa, Egeria, Elodea, Lagarosiphon and Ottelia) and Hydrilloideae (Enhalus, Halophila, Hydrilla, Maidenia, Najas, Nechamandra, Thalassia and Vallisneria).[3]

Hydrilla verticillata
Ottelia alismoides

Uses

Some species have become established ornamental plants, and subsequently serious weeds in the wild (especially Egeria, Elodea and Hydrilla).

Genera
Genera crosses (Hydrocharitaceae)
Kubitzki (ed. 1998[7]) data.kew[8] APWeb (mobot.org)[9] Watson & Dallwitz (delta-intkey)[10]
Hydrocharitaceae
1. OtteliaOttelia Pers. (including Benedictaea Toledo, Boottia Wall.) (excludes Oligolobos Gagnep.)Ottelia Persoon (including Benedictaea Toledo, Boottia Wallich, Oligolobos Gagnepain, Xystrolobus Gagnepain)Ottelia
2. StratiotesStratiotes L.Stratiotes L.Stratiotes
3. HydrocharisHydrocharis L.Hydrocharis L.Hydrocharis
4. LimnobiumLimnobium Rich. (including Hydromystria G.Mey.Limnobium Richard (including Hydromystria G. Meyer)Limnobium
5. BlyxaBlyxa Noronha ex Thouars (excludes Enhydrias Ridl.)Blyxa Richard (including Enhydrias Ridley)Blyxa
6. ApalantheApalanthe Planch.(in Elodea Michaux)Apalanthe
7. EgeriaEgeria Planch.Egeria PlanchonEgeria
8. ElodeaElodea Michx. (including Anacharis Rich., Udora Nutt.)Elodea Michaux (including Anacharis Richard, Apalanthe Planchon, Hydora Besser, Philotria Rafinesque, Serpulica Pursh, Udora Nuttall)Elodea
9. HydrillaHydrilla Rich.Hydrilla RichardHydrilla
10. AppertiellaAppertiella C.D.K.Cook & TriestAppertiella C. D. K. Cook & TriestAppertiella
11. LagarosiphonLagarosiphon Harv.Lagarosiphon HarveyLagarosiphon
12. NechamandraNechamandra Planch.Nechamandra PlanchonNechamandra
13. MaideniaMaidenia RendleMaidenia RendleMaidenia
14. VallisneriaVallisneria L.Vallisneria L.Vallisneria
15. EnhalusEnhalus Rich.Enhalus RichardEnhalus
16. ThalassiaThalassia Banks ex C.KoenigThalassia C. KoenigThalassia
17. HalophilaHalophila ThouarsHalophila ThouarsHalophila
(in Najas, Najadaceae)Najas L.Najas L.(in Najas, Najadaceae)
(name not found)Enhydrias Ridl.(in Blyxa, Hydrocharitaceae)(name not found)
(name not found)Oligolobos Gagnep.(in Ottelia, Hydrocharitaceae)(name not found)
Najadaceae
1. Najas(in Najas, Hydrocharitaceae)(in Najas, Hydrocharitaceae)Najas

References
  1. Angiosperm Phylogeny Group (2009). "An update of the Angiosperm Phylogeny Group classification for the orders and families of flowering plants: APG III". Botanical Journal of the Linnean Society. 161 (2): 105–121. doi:10.1111/j.1095-8339.2009.00996.x.
  2. Christenhusz, M. J. M.; Byng, J. W. (2016). "The number of known plants species in the world and its annual increase". Phytotaxa. Magnolia Press. 261 (3): 201–217. doi:10.11646/phytotaxa.261.3.1.
  3. Les DH, DH; Moody, ML; Soros, CL (2006), "A reappraisal of phylogenetic relationships in the monocotyledon family Hydrocharitaceae (Alismatidae)", Aliso, 22: 211–230, doi:10.5642/aliso.20062201.18
  4. Tanaka, Norio; Setoguchi, Hiroaki; Murata, Jin (1997), "Phylogeny of the family Hydrocharitaceae inferred from rbcL and matK gene sequence data", Journal of Plant Research, 110 (3): 329, doi:10.1007/BF02524931, S2CID 10939773
  5. Les, DH; Cleland, MA; Waycott, M (1997), "Phylogenetic studies in Alismatidae, II: evolution of marine angiosperms (seagrasses) and hydrophily", Systematic Botany, 22 (3): 443, doi:10.2307/2419820, JSTOR 2419820
  6. Genera of Hydrocharitaceae, GRIN Taxonomy for Plants
  7. Kubitzki (ed.) 1998. The families and genera of vascular plants, vol 4, Monocotyledons: Alismatanae and Commelinanae (except Gramineae). Springer-Verlag, Berlin.
  8. Vascular Plant Families and Genera. List of genera in family HYDROCHARITACEAE (accessed 2016-06-02) http://data.kew.org/cgi-bin/vpfg1992/genlist.pl?HYDROCHARITACEAE
  9. VASCULAR PLANT FAMILIES and GENERA. List of Genera in HYDROCHARITACEAE. (accessed 2016-06-02) http://www.mobot.org/mobot/research/apweb/genera/hydrocharitaceaegen.html
  10. Watson & Dallwitz. Hydrocharitaceae. The families of flowering plants. http://delta-intkey.com/angio/www/hydrocha.htm
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