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Potamogetonaceae

Potamogetonaceae
Potamogetonaceae image
Paul Rothrock
  • FNA
  • Resources
Robert R. Haynes; C. Barre Hellquist in Flora of North America (vol. 22)
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.

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 Recent molecular evidence (D. H. Les, unpublished), combined with existing morphologic evidence, indicates that Potamogeton in the broad sense actually represents two separate lineages.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.

<< 51 - 100 taxa >>
Potamogeton interior
Media resource of Potamogeton interior
Potamogeton interruptus
Media resource of Potamogeton interruptus
Potamogeton lanceolatus
Media resource of Potamogeton lanceolatus
Potamogeton longiligulatus
Media resource of Potamogeton longiligulatus
Potamogeton lucens
Media resource of Potamogeton lucens
Potamogeton luxurians
Media resource of Potamogeton luxurians
Potamogeton maackianus
Media resource of Potamogeton maackianus
Potamogeton malaianus
Media resource of Potamogeton malaianus
Potamogeton mandschuriensis
Media
not available
Potamogeton marianensis
Media
not available
Potamogeton marinus
Media resource of Potamogeton marinus
Potamogeton montevidensis
Media resource of Potamogeton montevidensis
Potamogeton montezumawellensis
Media resource of Potamogeton montezumawellensis
Potamogeton mucronatus
Media resource of Potamogeton mucronatus
Potamogeton mysticus
Media resource of Potamogeton mysticus
Potamogeton natans
Media resource of Potamogeton natans
Potamogeton nodosus
Media resource of Potamogeton nodosus
Potamogeton nuttallii
Media resource of Potamogeton nuttallii
Potamogeton oakesianus
Media resource of Potamogeton oakesianus
Potamogeton oblongus
Media resource of Potamogeton oblongus
Potamogeton obtusifolius
Media resource of Potamogeton obtusifolius
Potamogeton ochreatus
Media resource of Potamogeton ochreatus
Potamogeton octandrus
Media resource of Potamogeton octandrus
Potamogeton ogdenii
Media resource of Potamogeton ogdenii
Potamogeton oxyphyllus
Media resource of Potamogeton oxyphyllus
Potamogeton paramoanus
Media resource of Potamogeton paramoanus
Potamogeton pennsylvanicus
Media resource of Potamogeton pennsylvanicus
Potamogeton perfoliatus
Media resource of Potamogeton perfoliatus
Potamogeton polygonifolius
Media resource of Potamogeton polygonifolius
Potamogeton porsildiorum
Media resource of Potamogeton porsildiorum
Potamogeton porteri
Media resource of Potamogeton porteri
Potamogeton praelongus
Media resource of Potamogeton praelongus
Potamogeton pulcher
Media resource of Potamogeton pulcher
Potamogeton purshii
Media resource of Potamogeton purshii
Potamogeton pusillus
Media resource of Potamogeton pusillus
Potamogeton rectifolius
Media resource of Potamogeton rectifolius
Potamogeton richardii
Media
not available
Potamogeton richardsonii
Media resource of Potamogeton richardsonii
Potamogeton robbinsii
Media resource of Potamogeton robbinsii
Potamogeton rotundatus
Media resource of Potamogeton rotundatus
Potamogeton schweinfurthii
Media resource of Potamogeton schweinfurthii
Potamogeton scoliophyllus
Media resource of Potamogeton scoliophyllus
Potamogeton sibiricus
Media
not available
Potamogeton spathuliformis
Media resource of Potamogeton spathuliformis
Potamogeton spirillus
Media resource of Potamogeton spirillus
Potamogeton strictifolius
Media resource of Potamogeton strictifolius
Potamogeton subnitens
Media resource of Potamogeton subnitens
Potamogeton suboblongus
Media resource of Potamogeton suboblongus
Potamogeton subrufus
Media resource of Potamogeton subrufus
Potamogeton subsessilis
Media resource of Potamogeton subsessilis
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