Potamogeton nodosus

Taxonomy

Unambiguous Synonyms:

1. Potamogeton americanus Cham. & Schlecht.
2. Potamogeton fluitans Roth

Notes:

Publishing author: Roth

Publishing author: Roem. & Schult. Publication: Syst. iii. 509

Name Status: Accepted Name. Latest taxonomic scrutiny: 15-Mar-2000

Place of publication: Encycl. suppl. 4:535. 1816

Name verified on 28-Apr-2000 by ARS Systematic Botanists. Last updated: 10-Mar-2003

Physical Description

Family Potamogetonaceae:

Herbs, perennial or rarely annual, rhizomatous or not rhizomatous, caulescent; turions absent or present. Leaves alternate or nearly opposite, submersed or both submersed and floating, sessile or petiolate; sheath not persisting longer than blade, not leaving circular scar when shed, ligulate, not auriculate, or rarely auriculate; intravaginal squamules scales, more than 2. Inflorescences terminal or axillary, spikes, capitate spikes, or panicles of spikes, not subtended by spathe, pedunculate; peduncle not elongating, not spiraling following fertilization. Flowers bisexual; subtending bracts absent; tepals 4 in 1 series; stamens [2 or] 4, epitepalous, in 1 series; anthers distinct, dehiscing vertically; pollen spheric; pistils 1 or 4, mostly not stipitate, rarely short-stipitate; ovules marginal, orthotropous. Fruits drupaceous. Seeds 1; embryo curved.

Genera 3, species ca. 90 (2 genera, 37 species in the flora) : nearly worldwide.

The family has historically been considered to consist of two genera, Potamogeton and Groenlandia. Recent molecular evidence (D. H. Les, unpublished), combined with existing morphologic evidence, indicates that Potamogeton in the broad sense actually represents two separate lineages. We recognize those lineages at the generic level, Potamogeton in the strict sense and Stuckenia. Consequently, we accept three genera in the family, Potamogeton, Stuckenia, and Groenlandia.

Members of Potamogetonaceae have been variously combined with members of Zosteraceae, Cymodoceaceae, Zannichelliaceae, and Najadaceae to comprise compose Zosteraceae, Najadaceae, or Potamogetonaceae. Potamogetonaceae, as here interpreted, are separated from the other families by their bisexual flowers, the absence of spathelike bracts, and in some species, the presence of turions.

Aquatic vascular plants are known for their phenotypic plasticity (R. R. Haynes 1974) . Plasticity may result from the varied environmental conditions in which the populations grow or from morphologic changes in individuals of a population during the growing season (R. R. Haynes 1975) . Individuals in fruit have relatively consistent morphology within a species. Regardless of phenotypic plasticity, collections of Potamogetonaceae (and aquatic vascular plants in general) are often taken with little attention to the presence or absence of reproductive structures.

Reproductive features are most important in separating species of Potamogeton (R. R. Haynes 1978), and we include the entire family here. The keys may not always utilize reproductive features, but they are based on fruiting individuals. We strongly recommend that no one collect specimens of Potamogetonaceae that are lacking reproductive structures.

Leaves of Potamogetonaceae are stipulate. The stipules form a tubular sheath (stipular sheath) around the stem, free from or adnate to the base of the blade. In some species the leaf and sheath of submersed leaves are adnate for part of their length, and the leaf appears to have a sheathing base with an adaxial ligule at the junction of sheath and blade or petiole.

Fruits of Potamogetonaceae are drupaceous. The fruits do have endocarps but do not have fleshy mesocarps. Mesocarps exist but never become fleshy. Consequently, the fruits are not true drupes, they are drupaceous.

Many species of Potamogetonaceae undergo extensive vegetative reproduction either by turions or stem fragmentation. Turions are excellent modes of vegetative reproduction. The structures are produced at the stem tips and eventually fall to the substrate, either by a portion of the stem breaking off or by the stem itself falling to the substrate. The turions survive an unfavorable season, germinate, and grow into new plants during the next growing season. Because the unfavorable season is usually winter in North America, turions have been called "winter buds." At least one species, Potamogeton crispus, produces turions in early summer, and the turions survive the unfavorable season (summer, in this instance), germinating in the fall. The plant then survives the winter as a young individual, only a few centimeters long, even under ice, and begins growth as the water warms in the following spring. "Winter bud" is certainly not the correct term for P. crispus. The term "turions" designates all such structures, regardless of the unfavorable season.^[1]

Genus Potamogeton:

Herbs: rhizomes present or absent; tubers absent; turions present or absent. Stems terete or compressed, nodes occasionally with oil glands; turions with extremely shortened internodes, divided into outer and inner leaves; outer leaves 1--5 per side, similar to vegetative leaves or occasionally corrugate near base; inner leaves 1--10, rolled into fusiform structure, unmodified, or shortened and oriented at 90° angles to outer leaves. Leaves submersed or both submersed and floating, alternate to nearly opposite; stipules connate or not, if not, then convolute, tubular, sheathing stem and young inflorescences. Submersed leaves sessile or petiolate; stipules either free from or adnate to base of leaf blade for less than ½ length of stipule, if adnate, then extending past adnation as free ligule; blade translucent, linear to orbiculate, not channeled, flattened, base acute to perfoliate, margins entire or serrate, rarely crispate, apex subulate to obtuse; veins 1--35. Floating leaves petiolate, rarely nearly sessile; stipules free from base of leaf blade; blade elliptic to ovate, leathery, base cuneate to rounded or cordate, margins entire, apex acute to obtuse; veins 1--51. Inflorescences spikes or panicles of spikes, submersed or emersed, capitate or cylindric; peduncles stiff, if long enough then projecting inflorescence above surface of water. Flowers: pistils 1 or 4. Fruits abaxially rounded or keeled, flattened to turgid, beaked; embryo coiled 1 or more times. x = 13 or 14.

Species ca. 100: nearly worldwide.

Potamogeton is one of the most important genera in the aquatic environment, especially as food or habitat for aquatic animals (R. R. Haynes 1975). A few species become slightly weedy, but not significantly so. Plants of Potamogeton are important in stabilizing substrates and removing particulate matter from the water column.

The genus has been divided into several sections and numerous subsections (predominantly by J. O. Hagström 1916; see also R. R. Haynes 1975, 1985 for in-depth coverage of three subsections). After studying thousands of specimens over at least five continents, we believe that recognition of the many infrageneric categories is unwarranted. Consequently, we are not including infrageneric classification here.

Hybridization is common among members of the genus (J. O. Hagström 1916). Numerous hybrids were proposed, using intermediate stem anatomy as evidence of hybrid origin. We list all the hybrids that Hagström proposed for species that occur in North America. An additional 26 hybrids have been recognized for the British Isles (C. D. Preston 1995).

Vegetative and reproductive morphology varies considerably in the genus. Two types of stems occur, rhizomes and erect stems. Some species have both, others have only erect stems. Two types of leaves exist, submersed and floating. Floating leaves have well-developed epidermis abaxially and adaxially, and well-developed cuticle at least adaxially. Floating leaves may be similar in shape to that of the submersed, or they may differ considerably. Submersed leaves have no cuticle and do not have well-developed epidermis. All species of Potamogeton have submersed leaves; some also have floating leaves. Occasionally, individuals of floating-leaved species lose their submersed leaves because of decay or wave action. Leaves of Potamogeton may be sessile or petiolate and are divided into at least blade and stipule. The stipule may be adnate to the blade for 1/3 or less the length of the stipule. Venation in the stipule is parallel, and veins may appear coarse as distinct ridges on the stipule (fibrous), or they may be much less obvious, even difficult to observe (delicate). Stipular tissue between veins of fibrous stipules decays, leaving strands of fibers, whereas veins and the tissue between them decay in delicate stipules.

Many species have oil glands on the stem at the node of submersed leaves. These glands are especially common on species with sessile leaves. Circular and ranging from green to golden to white, they are present at most nodes, sometimes at all, or possibly only occasionally present. The glands (or nodal glands) are best observed with dried specimenses, a good light source, and magnification of at least 15&#180, although they can be observed under less ideal conditions.

Inflorescences may be either emergent or submersed. Emergent inflorescences are elongate and almost always terminal on the stem, whereas submersed inflorescences are globular and axillary. Most species have either emergent inflorescences or submersed inflorescences, but not both (monomorphic). Other species have both types of inflorescences on one plant (dimorphic).

All specimens should be collected when in fruit. Fruiting characteristics are extremely important in the genus, although they are not always given in the key. Vegetative features during fruiting are distinctive for the species; consequently, they are included in the key. Important features of the fruit include presence or absence of lateral and abaxial wings, ribs, ridges, or keels. Here, "ribbed" indicates a raised "vein" on a rounded surface; "ridged,"; a ridge with an obtuse angle; "keeled," a ridge with an acute angle; and "winged," a ridge that appears to have a wing distally.^[2]

Habit: Forb/herb

Images:

Distribution

Range and Population

Caribbean

Native: .

Reproduction

Duration: Perennial

Similar Species

Members of the genus Potamogeton:

There are approximately 811 species, subspecies, varieties, forms, and cultivars in this genus. Here are just 100 of them: P. alpinus tenuifolius · P. berchtoldii groenlandicus · P. berchtoldii tenuissimus · P. coloratus subflavus · P. filiformis occidentalis · P. lucens sinicus · P. octandrus limosellifolius · P. pectinatus chakassiensis · P. pusillus argentinus · P. pusillus friesii · P. pusillus mucronatus · P. pusillus sturrockii · P. apertus · P. attenuatus · P. bennettii · P. billupsii · P. biwaensis · P. champlainii · P. cognatus · P. cooperi · P. haynesii · P. inbaensis · P. kamogawaensis · P. meinshausenii · P. perplexus · P. pusilliformis · P. scoliophyllus · P. subnitens · P. subrufus · P. subsessilis · P. sudermanicus · P. suecicus · P. undulatus · P. variifolius · P. acifolius · P. acuminatus · P. acutifolius · P. affinis · P. alatus · P. alpino-natans · P. alpinus (Alpine Pondweed) · P. alpinus var. faxoni · P. amblyophyllus · P. americanus var. novaeboracensis · P. amplifolius (Large-Leaf Pondweed) · P. amplifolius f. homophyllus · P. amplifolius var. ovalifolius · P. anadyrensis · P. anglicus · P. anguillanus · P. angustatus · P. angustifolium · P. angustifolium var. connecticutensis · P. angustifolius f. longipedunculatus · P. angustifolius var. connecticutensis · P. angustifolius var. lucens · P. angustifolius var. methyensis · P. angustissimus · P. annulatus · P. antaicus · P. apicalis · P. applanatus · P. argutulus (Pondweed) · P. argutulus var. nodosifolius · P. aschersonii · P. aschersonii f. pusilloides · P. asiaticus · P. asplundi · P. attenuatus · P. attenuatus var. polygoniformis · P. augustani · P. augustanus · P. aulacophyllus · P. australiensis · P. australis · P. austriacus · P. austroeuropaeus · P. austrosibiricus · P. badiovirens · P. baenitzii · P. balatonicus · P. bambergensis · P. bashkiricus · P. berchtoldi · P. berchtoldii subsp. groenlandicus · P. berchtoldii subsp. tenuissimus · P. berghtoldii · P. berteroanus · P. besczeulicus · P. bicupulatus (Snailseed Pondweed) · P. bifolius · P. biformis · P. billotii · P. biwaensis · P. borealis · P. borysthenicus · P. bottnicus · P. bracteatus · P. brasiliensis · P. brechtoldii

Bibliography

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• Davidse, G. et al., eds. 1994. Flora mesoamericana. (F Mesoamer)
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• Hagström, J. O. 1916. Critical researches on the potamogetons. Kungl. Svenska Vetenskapsakad. Handl., n. s. 55(5): 1--281.
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Notes

Contributors:

• Bisby, F.A., Y.R. Roskov, M.A. Ruggiero, T.M. Orrell, L.E. Paglinawan, P.W. Brewer, N. Bailly, J. van Hertum, eds (2007). Species 2000 & ITIS Catalogue of Life: 2007 Annual Checklist. Species 2000: Reading, U.K.
• Brands, S.J. (comp.) 1989-2007. Systema Naturae 2000. The Taxonomicon. Universal Taxonomic Services, Amsterdam, The Netherlands. Accessed March 31, 2007.
• Global Biodiversity Information Facility. Accessed November 22, 2007. http://www.gbif.org Mediated distribution data from 29 providers.
• The International Plant Names Index. Accessed Jan 19, 2007.
• USDA, ARS, National Genetic Resources Program. Germplasm Resources Information Network - (GRIN) [Online Database]. National Germplasm Resources Laboratory, Beltsville, Maryland. URL (April 30, 2008)

Data Sources:

Accessed through GBIF Data Portal November 22, 2007:

• Conservatoire botanique national du Bassin parisien, Conservatoire botanique national du Bassin parisien
• Missouri Botanical Garden, Missouri Botanical Garden
• NLBIF, Limnodata
• Oregon State University, Vascular Plant Collection
• The Swedish Museum of Natural History
• , Lund Botanical Museum
• Tiroler Landesmuseum Ferdinandeum, Tiroler Landesmuseum Ferdinandeum
• USDA PLANTS, USDA PLANTS Database
• University of Alabama Biodiversity and Systematics, Herbarium

Identifiers:

• Integrated Taxonomic Information System (ITIS) Taxonomic Serial Number (TSN): 39009
• Global Biodiversity Information Facility Taxonkey: 13751082
• Globally Unique Identifier: urn:lsid:ipni.org:names:603330-1
• U.S.D.A. Plant Symbol: POAM11
• Zipcode Zoo Species Identifier: 57833

Footnotes:

1. Robert R. Haynes ,C. Barre Hellquist "Potamogetonaceae". in Flora of North America Vol. 22. Oxford University Press. Online at EFloras.org.
2. "Potamogeton". in Flora of North America Vol. 22. Oxford University Press. Online at EFloras.org.