Cabombaceae Rich. ex A.Rich.

Cabombaceae, H. Wild. Flora Zambesiaca 1:1. 1960

Morphology General Habit

Aquatic herbs with perennial rhizomes; stems coated with mucilage

Morphology Leaves

Leaves alternate, floating leaves peltate, sometimes with finely dissected submerged leaves in addition

Morphology Reproductive morphology Flowers

Flowers axillary, solitary, actinomorphic

Morphology Reproductive morphology Flowers Calyx

Sepals 3

Morphology Reproductive morphology Flowers Corolla

Petals 3, hypogynous

Morphology Reproductive morphology Flowers Androecium

Stamens 3–18; anthers extrorse, opening lengthwise

Morphology Reproductive morphology Flowers Gynoecium

Carpels 2–18, free; style very short or absent but with an attenuated, entire stigma; ovules 1–3, pendulous, parietal

Morphology Reproductive morphology Fruits

Fruiting carpels indehiscent

Morphology Reproductive morphology Seeds

Seeds 1–3 with a fleshy endosperm

Aona, L.Y.S. (2009). Neotropical Cabombaceae.

Morphology

Description

Perennial aquatic glabrous plants, rarely annual ; rhizome elongated, fixed to the substrate, stems elongated and submersed to distally floating. Leaves simple , petiolate , heterophyllous, floating, peltate , narrowly elliptic to broadly ovate , the submerse ones (only in Cabomba Aubl.) dissected , palmate ; stipules absent. Flowers on long pedicels, opening above the water, solitary, hermaphrodite , symmetry radial, hypogynous, tepals 6, white, pink, purple or yellow, the inner tepals (petals) with nectariferous auricles near the base; stamens 3-36, free , filaments flattened, anthers oblong , basifixed, with two thecae, extrorse with longitudinal dehiscence, carpels (1- )2-4(-18), free , ovules (1-)2-5, placentation laminar. Fruit achene -like, coriaceous , indehiscent ; seeds 1-5 per fruit , embryo small, endosperm reduced, perisperm abundant.

Distribution

Distribution in the Neotropics

Two genera:

• Cabomba (c. 5 species, widely distributed from the USA to Argentina), leaves heterophyllous, inner tepals bearing nectaries.
• Brasenia schreberi J.F.Gmel., a wind pollinated species with reduced flowers, distributed worldwide and cultivated for its edible shoots.

Diagnostic

Other important characters

• Petals (inner tepals) with auricular nectaries.
• Placentation laminar.

Distinguishing characters (always present)

• Cabombaceae are rather small-flowered 'waterlilies', with few ovules or seeds in each carpel; they have floating stems and all their flower parts are free (Stevens 2008).

Key differences from similar families

Cabombaceae is closely related to the true 'waterlilies', Nymphaeaceae, sharing with it several characters e.g:

• Stem rhizomatous.
• Leaves involute.
• Leaves peltate.
• Secondary veinspalmate, actinodromous, festoon brochidodromous.
• Actinodromous.
• Festoon brochidodromous.
• Margin toothed or entire.
• Flowers are single along the stem.

However, in Cabombaceae the flowers are trimerous, with 6 tepals (vs. sepals 4-6(-12) and petals 6-70 in Nympheaceae), and leaves may be heterophyllous.

Useful tips for generic identification

• Brasenia Schreb. is wind pollinated.
• Cabomba has paired nectaries on its inner tepals and is pollinated by insects (Stevens 2008).

Notable genera and distinguishing features

See above

General Description

Number of genera

See above.

Notes on delimitation

• Cabombaceae is in the order Nympheales together with Nymphaeaceae and Hydatellaceae.
• Saarela et al. (2007) suggest a few additional possible synapomorphies for Nymphaeales, such as hydrolysable tannins which in this group (e.g. in Nuphar Sm.) are different from those found elsewhere (Gottlieb et al. 1993; Ishimatsu et al. 1989) - although of course Hydatellaceae are a poorly known group.

Status

• Both genera are widely distributed and native. Species of the genus Cabomba are often used as aquarium plants.

Literature

Important literature

FERES, F. & AMARAL, M.C.E. 2003. Cabombaceae. In Wanderley, M. G. L., Shepherd, G. J. & Giulietti, A. M. (Eds.). Flora Fanerogâmica do Estado de São Paulo. Vol. 3. São Carlos, Editora RiMA. pp: 09-11.

GOTTLIEB, O., R., Kaplan, M. A. C., & Kubitzki, K. 1993. A suggested role of galloyl esters in the evolution of dicotyledons. Taxon 42: 539-552.

ISHIMATSU, M., Tanaka, T., Nonaka, G., Nishioka, I., Nishizawa, M., & Yamagishi, T. 1989. Tannins and related compounds. LXXIX. Isolation and characterisation of novel dimeric and trimeric hydrolyzable tannins, nuphrins C, D, E and F, from Nuphar japonicum DC. Chem. Pharmac. Bull. 37: 1735-1743.

ORGAARD, M. 1991. The genus Cabomba (Cabombaceae) - a taxonomic study. Nordic J. Bot. 11(2): 179-203.

SAARELA, J. M., Rai, H. S., Doyle, J. A., Endress, P. K., Mathews, S., Marchant, A. D., Briggs, B., & Graham, S. W. 2007. Hydatellaceae identified as a new branch near the base of the angiosperm phylogenetic tree. Nature 446: 312-315.

STEVENS, P. F. 2008. Angiosperm Phylogeny Website. Version 9, June 2008 [and more or less continuously updated since]. http://www.mobot.org/MOBOT/research/APweb/.