''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. They can be annual (commonly) or perennial (rarely); stem growth is conspicuously sympodial, but sometimes is not. These species are adapted to be in brackish 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 Polysiphonous describes an algal Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included org ...

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 of 1981 placed the family in order Najadales of subclass Alismatidae in class Liliopsida monocotyledonsin division Magnoliophyta angiosperms The APG II system of 2003 (unchanged from the APG system of 1998) does recognize such a family and places it in the order Alismatales, in the clade monocots. According to th
AP-Website
the family is doubtfully distinct from the family Cymodoceaceae: the plants in the three families Cymodoceaceae, Posidoniaceae, 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''* - 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'' 66: 167-171 # '' Ruppia didyma'' - Mexico, West Indies # '' Ruppia drepanensis'' - western + central Mediterranean # '' Ruppia filifolia'' - southern South America, Falkland Islands # '' Ruppia maritima'' - seashores and lakeshores around the world # '' Ruppia megacarpa'' - 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'' 97: 1156-1167Ito, 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'' - Canada, USA # '' Ruppia polycarpa'' - Australia, New Zealand (incl Chatham Islands) # '' Ruppia spiralis'' - seashores and lakeshores around the world # '' Ruppia tuberosa'' - Australia Marine grasses families: Zosteraceae, Cymodoceaceae, Ruppiaceae and Posidoniaceae. 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'', w ...

(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 events as well as

chloroplast capture Chloroplast capture is an evolutionary process through which inter-species Hybrid (biology), hybridization and subsequent backcrossing, backcrosses yield a plant with new genetic combination of nuclear and chloroplast genomes. For instance, 1) speci ...

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