Ruppia, also known as the widgeonweeds, ditch grasses or widgeon grass, is the only extant genus in the family Ruppiaceae, with 11 known species. These are aquatic plants widespread over much of the world. The genus name honours Heinrich Bernhard Rupp, a German botanist (1688–1719).Genaust, Helmut (1976). Etymologisches Wörterbuch der botanischen Pflanzennamen They are widespread outside of frigid zones and the tropics.
Description
These plants are aquatic, rhizomatous with roots set in the substratum. 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 estuaries. 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, 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.
Species 11 species are accepted. Ruppia bicarpa – Western Cape, South AfricaIto, Y., Nr. Tanaka, T. Ohi-Toma, J. Murata, and A.M. Muasya (2015) Phylogeny of Ruppia (Ruppiaceae) revisited: Molecular and morphological evidence for a new species from Western Cape, South Africa. Systematic Botany 40(4): 942–949. doi: 10.1600/036364415X689988 Ruppia brevipedunculata – China (Jiangsu) Ruppia cirrhosa (synonym Ruppia spiralis) – 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 and 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 polycarpa – Australia, New Zealand (including Chatham Islands) Ruppia sinensis – China (Jiangsu) Ruppia tuberosa – Australia
Taxonomy The Cronquist system of 1981 placed the family in order Najadales of subclass Alismatidae in class Liliopsida [=monocotyledons] in 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 the 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 in 2008.Zhao L.-C., Wu Z.-Y. (2008) A review on the taxonomy and evolution of Ruppia. Journal of Systematics and Evolution 46: 467–478.
Marine grasses families: Zosteraceae, Cymodoceaceae, Ruppiaceae and Posidoniaceae. Related families: Potamogetonaceae, Zannichelliaceae (not consistently).
+ Families and genera crosses (sea grasses) Kubitzki (ed. 1998Kubitzki (ed.) 1998. The families and genera of vascular plants, vol 4, Monocotyledons: Alismatanae and Commelinanae (except Gramineae). Springer-Verlag, Berlin.) Watson & Dallwitz (delta-intkey)Watson & Dallwitz. Zosteraceae. The families of flowering plants. http://delta-intkey.com/angio/www/zosterac.htm data.kewVascular Plant Families and Genera. List of genera in family CYMODOCEACEAE (accessed 2016-06-02) http://data.kew.org/cgi-bin/vpfg1992/genlist.pl?CYMODOCEACEAE APWeb (mobot.org)VASCULAR PLANT FAMILIES and GENERA. List of Genera in CYMODOCEACEAE (accessed 2016-06-02) http://www.mobot.org/mobot/research/apweb/orders/alismatalesweb.htm#Cymodoceaceael Zosteraceae 1. Zostera L. Zostera Zostera L. Zostera L. (including Heterozostera den Hartog, Macrozostera Tomlinson & Posluzny, Nanozostera Tomlinson & Posluzny, Zosterella J. K. Small) 2. Heterozostera den Hartog Heterozostera Heterozostera (Setch.) Hartog (in Zostera) 3. Phyllospadix Hook. Phyllospadix Phyllospadix Hook. Phyllospadix J. D. Hooker Cymodoceaceae 1. Syringodium Kütz Syringodium Syringodium Kutz. (in Cymodocea) 2. Halodule Endl. Halodule Halodule Endl. Halodule Endlicher 3. Cymodocea König Cymodocea Cymodocea K.Koenig (including Phycoschoenus (Asch.) Nakai ) Cymodocea König (including Amphibolis Agardh ?, Syringodium Kütz. ?, Thalassodendron den Hartog ?) 4. Amphibolis Agardh Amphibolis Amphibolis C.Agardh (including Pectinella J.M.Black) (in Cymodocea) 5. Thalassodendron de Hartog (name not found) Thalassodendron Hartog (in Cymodocea) Ruppiaceae Ruppia L. Ruppia (in Ruppia L. in Potamogetonaceae) Ruppia L. Posidoniaceae Posidonia König Posidonia Posidonia K.Koenig Posidonia König
+ Families and genera crosses (Potamogetonaceae) Kubitzki (ed. 1998) Watson & Dallwitz (delta-intkey)Watson & Dallwitz. Potamogetonaceae. The families of flowering plants. http://delta-intkey.com/angio/www/potamoge.htm data.kewVascular Plant Families and Genera. List of genera in family POTAMOGETONACEAE (accessed 2016-06-02) http://data.kew.org/cgi-bin/vpfg1992/genlist.pl?POTAMOGETONACEAE APWeb (mobot.org)VASCULAR PLANT FAMILIES and GENERA. List of Genera in POTAMOGETONACEAE (accessed 2016-06-02) http://www.mobot.org/mobot/research/apweb/orders/alismatalesweb.htm#Potamogetonaceae Potamogetonaceae 1. Potamogeton L. Potamogeton Potamogeton L. Potamogeton L. (including Coleogeton Les & Haynes, Stuckenia Börner) 2. Groenlandia J. Gray Groenlandia Groenlandia J.Gay Groenlandia J. Gay (in Ruppia in Ruppiaceae) (in Ruppia in Ruppiaceae) Ruppia L. (in Ruppia in Ruppiaceae) (in Althenia: Zannichelliaceae and Lepilaena: Zannichelliaceae) (in Althenia: Zannichelliaceae and Lepilaena: Zannichelliaceae) (in Althenia F.Petit: Zannichelliaceae and Lepilaena J.L.Drumm. ex Harv.:Zannichelliaceae) Althenia Petit (including Lepilaena Harvey) (in Pseudalthenia including Vleisia: Zannichelliaceae) (in Pseudalthenia: Zannichelliaceae and Vleisia: Zannichelliaceae) (Pseudalthenia not found, Vleisia Toml. & Posl.: Zannichelliaceae) Pseudalthenia Nakai (including Vleisia Tomlinson & Posluszny) (in Zannichellia L.: Zannichelliaceae) (in Zannichellia: Zannichelliaceae) (in Zannichellia L.: Zannichelliaceae) Zannichellia L. Zannichelliaceae 1. Zannichellia L. Zannichellia Zannichellia L. (in Zannichellia L.: Potamogetonaceae) 2. Pseudalthenia Nakai (including Vleisia) Pseudalthenia (excluding Vleisia) (name not found) (in Pseudalthenia: Potamogetonaceae) 3. Althenia Petit (excluding Lepilaena Drumm. ex. Harv.) Althenia (excluding Lepilaena) Althenia F.Petit (excluding Lepilaena J.L.Drumm. ex Harv.) Althenia Petit (including Lepilaena Harvey) 4. Lepilaena Drumm. ex. Harv. Lepilaena Lepilaena J.L.Drumm. ex Harv. (in Althenia Petit) (in Pseudalthenia) Vleisia Vleisia Toml. & Posl. (in Pseudalthenia: Potamogetonaceae)
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 and polyploidy 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