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''Ruppia'', also known as the widgeonweeds, ditch grasses or widgeon grass, is the only extant genus in the family Ruppiaceae, with eight known species. These are aquatic plants widespread over much of the world. The genus name honours
Heinrich Bernhard Rupp Heinrich Bernhard Rupp (or Ruppius) (born 22 August 1688 in Giessen, died 7 March 1719 in Jena) was a German botanist. He first studied Medicine in 1704 and met then Johann Jacob Dillenius (1684-1747). He first studied in Iena in 1711, then in Leid ...
, a German botanist (1688-1719). They are widespread outside of frigid zones and the tropics.


Description

The leaf is simple and not
rhizomatous In botany and dendrology, a rhizome (; , ) is a modified subterranean plant stem that sends out roots and shoots from its nodes. Rhizomes are also called creeping rootstalks or just rootstalks. Rhizomes develop from axillary buds and grow ho ...
. They can be annual (commonly) or perennial (rarely); stem growth is conspicuously
sympodial Sympodial growth is a bifurcating branching pattern where one branch develops more strongly than the other, resulting in the stronger branches forming the primary shoot and the weaker branches appearing laterally. A sympodium, also referred to a ...
, but sometimes is not. These species are adapted to be in
brackish Brackish water, sometimes termed brack water, is water occurring in a natural environment that has more salinity than freshwater, but not as much as seawater. It may result from mixing seawater (salt water) and fresh water together, as in estua ...
water (and salt marshes). The leaves are small or medium-sized. Their disposition can be alternate, opposite, or whorled (usually alternate except when subtending an inflorescence). Even, lamina keep entire and are setaceous or linear. The leaf just shows one vein without cross-venules. Stomata are not present. The mesophyll leaks calcium oxalate crystals. The minor leaf veins do not present phloem transfer cells and leaks vessels. These plants have stems without secondary thickening and xylem without vessels. The sieve-tube plastids are P-type. The root xylem does not present vessels. These plants are hermaphroditic, with anemophilous or hydrophilous pollination. The flowers are ebracteate, small, and regular. Commonly, the flowers are aggregated in ‘inflorescences’, but sometimes they are solitary. Often, they grow in racemes, spikes, or umbels. The scapiflorous inflorescences are terminal, in short spikes, or subumbelliform racemes, sometimes one- or few-flowered. They do not have hypogynous disks. These flowers do not have perianth absent, except when small staminal appendages are regarded as perianth segments. The androecial members are all equal. The androecium just presents two fertile stamens with sessile anthers dehiscing by longitudinal slits. The pollen is polysiphonous and its grains are three-celled and nonaperturate. The gynoecium (2–)4(–16) is superior, carpelled, and euapocarpous. The carpel is not stylate, apically stigmatic with the stigma peltate, or umbonate. These flowers only present one ovule pendulous, nonarillate, campylotropous, bitegmic, and crassinucellate. The placentation is apical and embryo-sac development is of the polygonum type. Before fertilization, they fuse polar nuclei. The fruit is drupaceous and fleshy, forming an aggregate. The fruiting carpel is indehiscent, commonly on a long, spirally twisted peduncle, with each drupelet becoming very long-stalked. The fruit contains one nonendospermic seed with starch. The embryo can be straight or slightly curved. Membranous testa do not have phytomelan.


Taxonomy

The
Cronquist system The Cronquist system is a taxonomic classification system of flowering plants. It was developed by Arthur Cronquist in a series of monographs and texts, including ''The Evolution and Classification of Flowering Plants'' (1968; 2nd edition, 1988) ...
of 1981 placed the family in order
Najadales Najadales is the botanical name of an order of flowering plants. A well-known system that used this name is the Cronquist system (1981), which used this name for an order in subclass Alismatidae with this circumscription: * order Najadales ** fa ...
of subclass
Alismatidae {{Short description, Subclass of flowering plants Alismatidae is a botanical name at the rank of subclass. Circumscription of the subclass will vary with the taxonomic system being used (there are many such systems); the only requirement being th ...
in class
Liliopsida Liliopsida Batsch (synonym: Liliatae) is a botanical name for the class containing the family Liliaceae (or Lily Family). It is considered synonymous (or nearly synonymous) with the name monocotyledon. Publication of the name is credited to Scopol ...
monocotyledons Monocotyledons (), commonly referred to as monocots, ( Lilianae '' sensu'' Chase & Reveal) are grass and grass-like flowering plants (angiosperms), the seeds of which typically contain only one embryonic leaf, or cotyledon. They constitute one of ...
in division
Magnoliophyta Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek words ('container, vessel') and ('seed'), and refers to those plants t ...
angiosperms Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek words ('container, vessel') and ('seed'), and refers to those plants ...
The
APG II system The APG II system (Angiosperm Phylogeny Group II system) of plant classification is the second, now obsolete, version of a modern, mostly molecular-based, system of plant taxonomy that was published in April 2003 by the Angiosperm Phylogeny Gr ...
of 2003 (unchanged from the
APG system The APG system (Angiosperm Phylogeny Group system) of plant classification is the first version of a modern, mostly molecular-based, system of plant taxonomy. Published in 1998 by the Angiosperm Phylogeny Group, it was replaced by the improved A ...
of 1998) does recognize such a family and places it in the order
Alismatales The Alismatales (alismatids) are an order of flowering plants including about 4,500 species. Plants assigned to this order are mostly tropical or aquatic. Some grow in fresh water, some in marine habitats. Description The Alismatales compr ...
, in the clade
monocots Monocotyledons (), commonly referred to as monocots, ( Lilianae '' sensu'' Chase & Reveal) are grass and grass-like flowering plants (angiosperms), the seeds of which typically contain only one embryonic leaf, or cotyledon. They constitute one of ...
. According to th
AP-Website
the family is doubtfully distinct from the family
Cymodoceaceae Cymodoceaceae is a family of flowering plants, sometimes known as the "manatee-grass family", which includes only marine species. The 2016 APG IV does recognize Cymodoceaceae and places it in the order Alismatales, in the clade monocots. The fam ...
: the plants in the three families
Cymodoceaceae Cymodoceaceae is a family of flowering plants, sometimes known as the "manatee-grass family", which includes only marine species. The 2016 APG IV does recognize Cymodoceaceae and places it in the order Alismatales, in the clade monocots. The fam ...
,
Posidoniaceae ''Posidonia'' is a genus of flowering plants. It contains nine species of marine plants ("seagrass"), found in the seas of the Mediterranean and around the south coast of Australia. The APG system (1998) and APG II system (2003) accept this gen ...
, and Ruppiaceae form a monophyletic group. A genus-level taxonomy was briefly revised by Zhao and Wu, including the following species in the world: ;species # '' Ruppia bicarpa'' - Western Cape, South Africa # ''
Ruppia cirrhosa ''Ruppia cirrhosa'' is a species of aquatic plant Aquatic plants are plants that have adapted to living in aquatic environments (saltwater or freshwater). They are also referred to as hydrophytes or macrophytes to distinguish them from algae ...
''* - temperate regions: Europe, Asia, north + south (but not tropical) Africa, North America, West Indies, Argentina *The name is a homotypic synonym of ''R. maritima''Ito, Y., T. Ohi-Toma, C. Nepi, A. Santangelo, A. Stinca, N. Tanaka, & J. Murata (2017
Towards a better understanding of the ''Ruppia maritima'' complex (Ruppiaceae): Notes on the correct application and typification of the names ''R. cirrhosa'' and ''R. spiralis''
''
Taxon In biology, a taxon ( back-formation from '' taxonomy''; plural taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular n ...
'' 66: 167-171
# ''
Ruppia didyma ''Ruppia'', also known as the widgeonweeds, ditch grasses or widgeon grass, is the only extant genus in the family Ruppiaceae, with eight known species. These are aquatic plants widespread over much of the world. The genus name honours Heinrich ...
'' - Mexico, West Indies # ''
Ruppia drepanensis ''Ruppia drepanensis'' is a species of plant in the family Ruppiaceae ''Ruppia'', also known as the widgeonweeds, ditch grasses or widgeon grass, is the only extant genus in the family Ruppiaceae, with eight known species. These are aquatic p ...
'' - western + central Mediterranean # ''
Ruppia filifolia ''Ruppia'', also known as the widgeonweeds, ditch grasses or widgeon grass, is the only extant genus in the family Ruppiaceae, with eight known species. These are aquatic plants widespread over much of the world. The genus name honours Heinrich ...
'' - southern South America, Falkland Islands # ''
Ruppia maritima ''Ruppia maritima'' is an aquatic plant species commonly known as beaked tasselweed, ditch grass, tassel pondweed and widgeon grass. Despite its scientific name, it is not a marine plant; is perhaps best described as a salt-tolerant freshwat ...
'' - seashores and lakeshores around the world # ''
Ruppia megacarpa ''Ruppia megacarpa'' is a submerged herb species in the genus '' Ruppia'' found in shallow brackish waters. It is a common on Australasian coasts, including Australia (NSW; SA; Vic Vic (; es, Vic or Pancracio Celdrán (2004). Diccionario ...
'' - Australia, New Zealand, Asia (Korea, Japan, and Russia)Ito, Y., T. Ohi-Toma, J. Murata & Nr. Tanaka (2010
Hybridization and polyploidy of an aquatic plant, ''Ruppia'' (Ruppiaceae), inferred from plastid and nuclear DNA phylogenies
''
American Journal of Botany The ''American Journal of Botany'' is a monthly peer-reviewed scientific journal which covers all aspects of plant biology. It has been published by the Botanical Society of America since 1914. The journal has an impact factor of 3.038, as of 2019 ...
'' 97: 1156-1167
Ito, Y., T. Ohi-Toma, A. V. Skriptsova, M. Sasagawa, Nr. Tanaka, and J. Murata (2014) ''Ruppia megacarpa'' (Ruppiaceae): a new species to the floras of Japan, Korea, and Russia. ''Botanica Pacofica'' 3: 49–52 # ''
Ruppia occidentalis ''Ruppia'', also known as the widgeonweeds, ditch grasses or widgeon grass, is the only extant genus in the family Ruppiaceae, with eight known species. These are aquatic plants widespread over much of the world. The genus name honours Heinrich ...
'' - Canada, USA # ''
Ruppia polycarpa ''Ruppia polycarpa'' is a submerged aquatic herb species in the genus '' Ruppia'' found in shallow brackish waters. It is a common submerged herb on Australasian coasts, including Australia (NSW; SA; Vic; WA) and New Zealand (type locality). ...
'' - Australia, New Zealand (incl Chatham Islands) # ''
Ruppia spiralis ''Ruppia spiralis'' is an aquatic plant species in the genus ''Ruppia'' of Ruppiaceae. This name was synonymized under ''R. cirrhosa'',Grande, L. 1918. ''Note di Floristica. Bull. Orto Bot. Regia Univ. Napoli'' 5: 55–67. but is resurrected for ...
'' - seashores and lakeshores around the world # '' Ruppia tuberosa'' - Australia Marine grasses families: Zosteraceae,
Cymodoceaceae Cymodoceaceae is a family of flowering plants, sometimes known as the "manatee-grass family", which includes only marine species. The 2016 APG IV does recognize Cymodoceaceae and places it in the order Alismatales, in the clade monocots. The fam ...
, Ruppiaceae and
Posidoniaceae ''Posidonia'' is a genus of flowering plants. It contains nine species of marine plants ("seagrass"), found in the seas of the Mediterranean and around the south coast of Australia. The APG system (1998) and APG II system (2003) accept this gen ...
. Related families:
Potamogetonaceae The Potamogetonaceae, commonly referred to as the pondweed family, is an aquatic family of monocotyledonous flowering plants. The roughly 110 known species are divided over six genera. The largest genus in the family by far is ''Potamogeton'', w ...
,
Zannichelliaceae The Potamogetonaceae, commonly referred to as the pondweed family, is an aquatic family of monocotyledonous flowering plants. The roughly 110 known species are divided over six genera. The largest genus in the family by far is '' Potamogeton'', ...
(not consistently).


Phylogeny and evolution

The first molecular phylogeny of the monogeneric family discerned three distinct species, ''R''. ''tuberosa'', ''R''. ''megacarpa'', and ''R''. ''polycarpa'', and one species complex comprising six lineages. The species complex, named ''R''. ''maritima'' complex, was later updated as a group of eight lineages.Ito, Y., T. Ohi-Toma, J. Murata & Nr. Tanaka (2013
Comprehensive phylogenetic analyses of the ''Ruppia'' ''maritima'' complex focusing on taxa from the Mediterranean
'' Journal of Plant Research'' 126: 753-762
These studies revealed that multiple
hybridization Hybridization (or hybridisation) may refer to: *Hybridization (biology), the process of combining different varieties of organisms to create a hybrid *Orbital hybridization, in chemistry, the mixing of atomic orbitals into new hybrid orbitals *Nu ...
and
polyploidy Polyploidy is a condition in which the biological cell, cells of an organism have more than one pair of (Homologous chromosome, homologous) chromosomes. Most species whose cells have Cell nucleus, nuclei (eukaryotes) are diploid, meaning they ha ...
events as well as chloroplast capture have occurred in the evolution of the genus.


Phytochemistry

These plants present an anatomy non-C4 type. Seven labdanes have been identified from this genus: :* ''ent''-14,15-Dinor-8(17)-labden-13-one :* Methyl ester of (''ent-12S'')-15,16-Epoxy-12-hydroxy-12-oxo-8(17),13(16),14-labdatrien-19-oic acid. :* (-)-15,16-epoxy-8(17),13(16),14-labdatrien-19-ol. :* Methyl ester of (-)-15,16-epoxy-8(17),13(16),14-labdatrien-19-oic acid. :* (-)-15,16-Epoxy-8(17),13(16),14-labdatrien-19-al. :* (-)-15,16-Epoxy-8(17),13(16),14-labdatrien-19-yl acetate :* (''ent-13E'')-8(17),13-Labdadien-15-ol Three steroids have been also isolated: :* (''3β,5α,6β,7α,22E,24R'')-Ergosta-8(14),22-diene-3,6,7-triol. :* (3β,5α,6β,7α,22E,24R)-Ergosta-8,22-diene-3,6,7-triol :* (24R)-Ergost-4-ene-3,6-dione.


References


External links


Ruppiaceae in the ''Flora of North America''

NCBI Taxonomy Browser

links at CSDL, Texas
{{Taxonbar, from=Q157048 Brackish water plants Alismatales genera