Aponogetonaceae

Taxonomy

Family name: Aponogetonaceae J. Agardh

Synonym(s): [none]

Common name(s): cape pondweed family

*Number of genera/species: 1/56

List of genera (GRIN-Global)

Disseminule

seed

Description

Fruit a folliclefollicle:
a dry to (rarely) fleshy fruit derived from a single carpel that opens along a single longitudinal suture, derived from a single, superior, simple ovary; the seeds may be arillate or with a fleshy testa
, which are free or nearly free from each other, 2–22 mm long, globoseglobose:
3D shape—more or less spherical
to teardrop shapedteardrop-shaped:
2D shape—widest point is toward one end of the fruit, the other end tapers sharply to a pointed end
, tereteterete:
approximately circular in cross section; width and thickness approximately equal
in transection, beaks distinct and often curvedcurved:
(of embryo) linear embryo is curved into an arch or horseshoe with the ends far apart
, with one to many seeds. Pericarp brown to green, leatheryleathery:
texture—moderately thick, tough, and very pliable
, and decaying at maturity to release seeds. The infructescencesinfructescence:
mature (fruiting) inflorescence
often form underwater.

Seeds cylindricalcylindrical:
3D shape—a cylinder, with parallel sides and a circular cross-section; tubular or rod-shaped
to lens-shapedlens-shaped:
2D shape—round and flattened with two curved (convex) surfaces
, 0.7–18 mm long. Two seed types are present, double-coated seeds with sarcotestassarcotesta:
pulpy or fleshy outer layer of the seed coat, simulates aril
or single-coated. In double-coated seeds, the outer layer is transparent (loose and mucilaginousmucilaginous:
resembling mucilage; moist and sticky
) and veined, and the inner layer is brown. Embryos are not well developed in the double-coated seeds. In single-coated seeds, the seed coat is brown to green, glossyglossy:
shiny
, thick and spongyspongy:
soft, light, discontinuous but cohesive, and somewhat resilient
, and smooth, wrinkledwrinkled:
surface relief—shallow, irregular folds and furrows covering the surface; appearing overall though crumpled and then spread out
, or longitudinally ribbedribbed:
surface relief—wide, prominent, linear ridges that are generally rounded and longitudinally situated on the surface
. The embryo is well developed.

Embryo straight, linearlinear:
(shape) long, narrow, and uniform in width; (of embryo) embryo is straight and much longer than wide
, sometimes green in single-coated seeds.

Endosperm lacking.

Habitat and crop association

Aquatic plants, occurring in stagnant to fast-moving water. Usually not weedy, but Aponogeton distachyos L.f., is established in Australia and occurs in central-coastal and southern California.

Aquarium & Pond Plants of the World tool includes descriptions and images of genera in this family.

Identification features

Fruit
Type	folliclefollicle: a dry to (rarely) fleshy fruit derived from a single carpel that opens along a single longitudinal suture, derived from a single, superior, simple ovary; the seeds may be arillate or with a fleshy testa
Size range	2–22 mm long (includes beakbeak: a usually firm, terminal appendage, sometimes tapered )
Shape(s)	teardrop-shapedteardrop-shaped: 2D shape—widest point is toward one end of the fruit, the other end tapers sharply to a pointed end , oblongoblong: 2D shape—much longer than broad with nearly parallel sides, corners are rounded , globoseglobose: 3D shape—more or less spherical
Texture	leatheryleathery: texture—moderately thick, tough, and very pliable
Surface relief	smooth
Color(s)	reddish brown, green, brown, gray
Unique features	Small, leatheryleathery: texture—moderately thick, tough, and very pliable , folliclesfollicle: a dry to (rarely) fleshy fruit derived from a single carpel that opens along a single longitudinal suture, derived from a single, superior, simple ovary; the seeds may be arillate or with a fleshy testa with beaks, which may be short or long, terminal or laterallateral: (of embryo) embryo lies along the side of the seed, generally towards one end; of, at, or from the side; in grasses, can refer to the sides adjacent to the dorsal and ventral sides , and straight or curvedcurved: (of embryo) linear embryo is curved into an arch or horseshoe with the ends far apart
Seed
Size range	0.7–18 mm long
Shape(s)	oblongoblong: 2D shape—much longer than broad with nearly parallel sides, corners are rounded , cylindricalcylindrical: 3D shape—a cylinder, with parallel sides and a circular cross-section; tubular or rod-shaped , ellipsoidellipsoid: 3D shape—elliptic , lens-shapedlens-shaped: 2D shape—round and flattened with two curved (convex) surfaces , fusiformfusiform: spindle-shaped; broadest at the middle and tapering at both ends
Surface relief	smooth, wrinkledwrinkled: surface relief—shallow, irregular folds and furrows covering the surface; appearing overall though crumpled and then spread out , or ribbedribbed: surface relief—wide, prominent, linear ridges that are generally rounded and longitudinally situated on the surface
Color(s)	brown, purple, green, gray
Other
Embryo	rudimentaryrudimentary: (of embryo) embryo is small and fills less than a quarter of the seed and can be variable in shapes, such as linear, spatulate, or oval or moderately well developed
Nutritive tissue	lacking at maturity

Distribution

Tropical and subtropical regions in Africa, Madagascar, Asia, and Australia.

Distribution map courtesy of Angiosperm Phylogeny Website.

References

Baskin and Baskin 2021Baskin and Baskin 2021:
Baskin C and Baskin J. 2021. Relationship of the lateral embryo (in grasses) to other monocot embryos: A status up-grade. Seed Science Research 31 (3): 199-210. doi:10.1017/S0960258521000209; Dahlgren et al. 1985Dahlgren et al. 1985:
Dahlgren RMT, Clifford HT, and Yeo PF. 1985. The families of the monocotyledons: structure, evolution, and taxonomy. Springer-Verlag, Berlin. 520 pp.; Flora of Australia 2021+Flora of Australia 2021+:
Flora of Australia. Australian Biological Resources Study, Canberra. Accessed January 2021–March 2024. URL: http://www.ausflora.org.au; Kirkbride et al. 2006Kirkbride et al. 2006:
Kirkbride JH, Jr, Gunn CR, and Dallwitz MJ. 2006. Family guide for fruits and seeds, vers. 1.0. Accessed September 2020-January 2022. URL: https://nt.ars-grin.gov/seedsfruits/keys/frsdfam/index.cfm .; Kubitzki et al. 1990+Kubitzki et al. 1990+:
Kubitzki K et al., eds. 1990+. The families and genera of vascular plants. 7+ vols. Berlin etc.; Lye 1989aLye 1989a:
Lye KA. 1989. Aponogetonaceae. In: Polhill RM, ed. Flora of Tropical East Africa. AA Balkema, Rotterdam, Netherlands. 10 pp.; Thiselton-Dyer 1897Thiselton-Dyer 1897:
Thiselton-Dyer WT. 1897. Flora capensis: being a systematic description of the plants of the Cape colony, Caffraria, amp; Port Natal (and neighbouring territories). Vol. 7. L. Reeve, Kent UK. 791 pp. https://doi.org/10.5962/bhl.title.821; van Bruggen 1969van Bruggen 1969:
van Bruggen HWE. 1969. Revision of the genus Aponogeton (Aponogetonaceae). Blumea 16 (1): 143-265.; van Bruggen 1973van Bruggen 1973:
van Bruggen HWE. 1973. Revision of the genus Aponogeton (Aponogetonaceae) VI. The species of Africa. Bulletin du Jardin Botanique National de Belgique/ Bulletin van de Nationale Plantentuin van Belgie 43: 193-233. https://doi.org/10.2307/3667566; Watson and Dallwitz 1992+Watson and Dallwitz 1992+:
Watson L and Dallwitz MJ. 1992+. The families of flowering plants: descriptions, illustrations, identification, and information retrieval. Version: 6th Accessed September 2020-September 2022. URL: delta-intkey.com

*The number of genera and species is based on Christenhusz and Byng 2016Christenhusz and Byng 2016:
Christenhusz MJM and Byng JW. 2016. The number of known plant species in the world and its annual increase. Phytotaxa 261 (3): 201-217. https://doi.org/10.11646/phytotaxa.261.3.1, which may differ from the number of genera in GRIN-Global.