Aponogetonaceae J.G. Agardh
Habit and leaf form. Herbs; laticiferous. Perennial; cormous, or rhizomatous. Hydrophytic; rooted. Leaves emergent and floating. Often heterophyllous. Leaves alternate; petiolate; sheathing. Leaf sheaths with free margins. Leaves simple. Lamina parallel-veined; cross-venulate (the tissue between the veins breaks up as the leaf matures, leaving a network with holes). Axillary scales present.
General anatomy. Plants with laticifers (articulated). Accumulated starch exclusively ‘pteridophyte type’.
Leaf anatomy. Stomata present (on floating leaves); paracytic.
Lamina without secretory cavities (assuming that Cronquist’s ‘with well developed secretory canals’ refer to laticifers). The mesophyll containing calcium oxalate crystals. The mesophyll crystals solitary-prismatic (? — no mention of raphides). Minor leaf veins without phloem transfer cells (Aponogeton). Vessels absent.
Stem anatomy. Secondary thickening absent. Xylem without vessels.
Root anatomy. Root xylem with vessels, or without vessels. Vessel end-walls scalariform.
Reproductive type, pollination. Unisexual flowers absent. Plants hermaphrodite. Floral nectaries present. Nectar secretion from the gynoecium (from the sides of the carpels). Entomophilous; via beetles, or via hymenoptera.
Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’ (commonly projected above the water in 1–3 spikes). Inflorescences pseudanthial (sometimes), or not pseudanthial; spatheate (the spathe caducous). Flowers small; usually very irregular; when irregular (i.e. usually), zygomorphic. The floral irregularity involving the perianth. Flowers cyclic, or partially acyclic. Sometimes the gynoecium acyclic. Perigone tube absent.
Perianth of ‘tepals’, or absent; when present, (1–)2(–6); free; 1 whorled; petaloid; when present, white (usually), or blue, or purple.
Androecium 6 (usually 3 + 3), or 25–100 (i.e. sometimes ‘many’). Androecial members branched (when ‘many’), or unbranched; 2–4 whorled. Stamens 6(–50); diplostemonous to polystemonous. Anthers dehiscing via longitudinal slits; extrorse, or latrorse; tetrasporangiate. Endothecium developing fibrous thickenings. The endothecial thickenings spiral. Microsporogenesis successive, or simultaneous. The initial microspore tetrads tetrahedral, or decussate. Anther wall of the ‘monocot’ type. Pollen grains aperturate; 1 aperturate; sulcate; 2-celled, or 3-celled.
Gynoecium (2–)3–6(–9) carpelled. Carpels isomerous with the perianth, or reduced in number relative to the perianth, or increased in number relative to the perianth. Gynoecium apocarpous; eu-apocarpous to semicarpous (basally fused to varying extents); superior. Carpel apically stigmatic; 1–8 ovuled. Placentation basal. The ‘odd’ carpel anterior. Stigmas dry type; papillate; Group II type. Ovules ascending; anatropous; crassinucellate. Embryo-sac development Polygonum-type. Polar nuclei fusing prior to fertilization. Antipodal cells formed; 3; not proliferating; persistent. Synergids pear-shaped. Endosperm formation helobial.
Fruit non-fleshy; more or less an aggregate. The fruiting carpel dehiscent; a follicle. Seeds non-endospermic. Seeds with starch. Cotyledons 1 (bifacial). Embryo chlorophyllous; straight. Testa without phytomelan (?); fleshy or membranous.
Seedling. Germination phanerocotylar. Hypocotyl internode present (short). Seedling collar not conspicuous. Cotyledon hyperphyll elongated; assimilatory; dorsiventrally flattened. Coleoptile absent. Seedling non-macropodous. Seedling cataphylls absent. First leaf dorsiventral. Primary root ephemeral.
Physiology, biochemistry. Not cyanogenic. Alkaloids absent (2 species). Proanthocyanidins present, or absent; when present, cyanidin. Flavonols present; kaempferol and quercetin, or quercetin. Ellagic acid absent. Saponins/sapogenins absent.
Geography, cytology. Sub-tropical and tropical. Palaeotropical and South Africa. X = 8.
Taxonomy. Subclass Monocotyledonae. Superorder Alismatiflorae; Hydrocharitales. APG (1998) Monocot; non-commelinoid; Alismatales. Species 47. Genera 1; only genus, Aponogeton.
Economic uses, etc. Some aquarium and watergarden ornamentals.
Illustrations. • Technical details.
Cite this publication as: ‘L. Watson and M. J. Dallwitz (1992 onwards). The Families of Flowering Plants: Descriptions, Illustrations, Identification, and Information Retrieval. Version: 14th December 2000. http://biodiversity.uno.edu/delta/’. Dallwitz (1980), Dallwitz, Paine and Zurcher (1993, 1995, 2000), and Watson and Dallwitz (1991) should also be cited (see References).
