Alexa Oliveira-Paes Coelho
Universidade Estadual de Feira de Santana, Bahia, Brazil.
Annual or perennial herbs, shrubs or small trees, sometimes with thickened and succulent stem base, caudex or underground storage; roots swollen and tuberous in several species. Stipules absent but hairs, bristles or scales present in leaf-axils of many species, these generally interpreted as reduced stipules, axillary pubescence copious in some species. Leaves alternate or occasionally opposite, sometimes in the form of perfoliate umbrella-like structures (Montia L.); petioles poorly defined; blades flattened to terete, normally glabrous, sometimes succulent, base usually narrow, margins entire. Inflorescences of solitary flowers or paniculate, but commonly described as dichasia converting distally into monochasia, monochasia frequently straightened to resemble racemes or spikes, axes sometimes reduced, resulting in condensed head -like inflorescences. Flowers actinomorphic or slightly zygomorphic (Montia), bisexual or rarely unisexual, small to large and showy, short-lived, often cleistogamus; sepals usually 2 (-3) or many (Lewisia Pursh), imbricate, persistent or deciduous (Talinum Adans.); petals (2-) 5 (12 or rarely more), free or sometimes connate at base; stamens 1 (Monocosmia Fenzl) - numerous, opposite petals, often grouped in bundles when numerous, filaments usually free, sometimes fused basally to perianth base, anthers basifixed, longitudinally dehiscent; pollen spinose, endexine poorly developed; gynoecium syncarpous, ovary superior or inferior or semi-inferior (Portulaca L.), carpels (2) 3 (8), 1-locular throughout or initially plurilocular and becoming 1-locular distally (Portulaca), style cleft to various lengths, branches and/or stigmas as many as carpels; placentation basal or free -central, ovules 1-many, mostly campylotropous. Fruits dry capsules dehiscing circumscissilely or by longitudinal valves (3-6), valves in some genera longitudinally involute. Seeds (1) 3- numerous, cochleate-reniform to angular or rounded, testa often distinctly sculptured; sarcotesta present, surrounding seed; embryo slightly curved to almost circular, endosperm absent or almost absent; perisperm often abundant.
Notes on delimitation
- The Portulacaceae were placed in the Caryophyllales by Cronquist.
- The family is one of those strongly nested among the other betalain-producing families of the Caryophyllideae and as currently circumscribed is closely allied with the Cactaceae, Basellaceae and Didieraceae.
- The close alliance of Cactaceae with Portulacaceae has been demonstrated with morphological data (hairs or scales present in leaf-axils) and molecular data.
Distribution in the Neotropics
- The Portulacaceae are cosmopolitan, with 25-30 genera and 450-500 species. Most genera and species occur in the west of North America, South America and Africa with some representatives in Europe and Asia.
- In tropical America and the bordering regions there are about 11 genera and probably 170 species.
Of the 11 tropical and subtropical American genera:
- Calandrinia s.l. (Calandrinia Kunth, Baitaria Ruiz & Pav. and Cistanthe Spach) is found throughout the Andes.
- Monocosmia Fenzl is restricted to north Argentina and Chile.
- Mona O. Nilsson is restricted to Colombia and Venezuela.
- Lenzia Philippi is an endemic of Chile.
- Talinaria Brandegee and Talinopsis A.Gray are restricted to Mexico.
- Talinum Adans. s.l. is found throughout tropical America.
- Portulaca L. is cosmopolitan.
Distinguishing characters (always present)
- Herbs, shrubs or subshrubs, often succulent.
- Hairs or scales present in leaf-axils.
- Fruits capsules, dehiscing circumscissilely or by longitudinal valves.
- Seeds often distinctly sculptured.
Other important characters
- Leaves alternate or apparently opposite and simple.
- Flowers usually with 2 sepals; petals usually 5; locule 1; placentation basal or free -central.
Key differences from similar families
- Portulacaceae are characterized by the presence of the herbs succulent, leaves alternate or apparently opposite, flowers with 2 sepals and 5 petals and fruit capsules. Sometimes they can be confused with Aizoaceae (herbs succulent and fruit capsules) but they have the leaves opposite, less often alternate; flowers with 3-8 tepals and fruit capsules loculicidal, rarely septicidal or circumscissile.
Number of genera
Eleven Neotropical genera:
- Calandrinia (Calandrinia) (10 species)
- Calandrinia (Cistanthe) (25 species)
- Calandrinia ( Baitaria) (40 species)
- Grahamia Gill. (1 species)
- Lenzia (1 species)
- Lewisia (2 species)
- Mona (1 species)
- Monocosmia (1 species)
- Montia (12 species)
- Portulaca (40 species)
- Talinopsis (1 species)
- Talinum (14 species)
- Talinaria (1 species)
Useful tips for generic identification
Notable genera and distinguishing features
- Calandrinia s.l.: sepals persistent, style free and capsules indehiscent.
- Portulaca: inferior or semi inferior ovary; circumscissile capsules.
- Talinum: sepals deciduous.
- Most of genera are endemic to the Neotropics.
- Portulaca is cosmopolitan.
- Talinum occurs in America and Africa.
- Some species are widespread as weeds.
- Portulaca grandiflora Hook. is cultivated in numerous colour forms including double flowers.
- Portulaca oleracea L. was formerly cultivated as a salad and spice plant.
- Talinum triangulare (Jacq.) Willd. is cultivated as a salad plant.
APG II, 2003. An update of the Angiosperm Phylogeny group classification for the orders and families of flowering plants: APG II. Botanical Journal of the Linnean Society 141(4): 399-436.
Applequist, W.L. and Wallace, R.S. 2001. Phylogeny of the Portulacaceous Cohort Based on ndhF Sequence Data. Syst. Bot. 26 (2): 406-419.
Behnke, H.D. and Mabry, T.J. 1994. (eds.) Caryophyllales Evolution and Systematics. Springer-Verlag, Berlin, 334 pp.
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Carolin, R.C. 1993. Portulacaceae, pp. 544-555. In: K. Kubitzki, J.B. Rhower and V. Bittrich (eds.). The Families and Genera of Vascular Plants, vol. II. Springer-Verlag, Berlin.
Coelho, A.A.de O.P. and Giulietti, A.M. 2006. Revisão Taxonômica das Portulaca L. (Portulacaceae) no Brasil. Tese de doutorado. Programa de Pós-Graduação em Botânica. Universidade Estadual de Feira de Santana, Bahia, Brasil. 196pp.
Eggli, U. and Hartmann, H.E.K. 2002. Portulacaceae, pp. 370-433. Illustrated Handbook of Succulent Plants. Springer-Verlag, Berlin.
Eliasson, U. 2004. Portulacaceae, pp. 310-312. In: Smith, N., Mori, S.A., Henderson, A., Stevenson, D.W. and Heald, S.V. (eds). Flowering Plants of the Neotropics. Princeton University Press, Princeton.
Judd, W.S., Campbell, S.C., Kellogg, E.A. and Stevens, P.F. 1999. Portulacaceae, pp. 248-250. Plant Systematics: A Phylogenetic Approach. Sinauer Associates, Sunderland.
Legrand, C.D. 1962. Las Especies Americanas de Portulaca. An. del Mus. de Hist. Nat. de Montevideo 7(3): 9-147.
Nyananyo, B.L. 1990. Tribal and generic relationship in the Portulacaceae (Centrospermae). Feddes Repertorium 101:237-241.
How to cite
Coelho, A.O.-P. (2009). Neotropical Portulacaceae. In: Milliken, W., Klitgård, B. & Baracat, A. (2009 onwards), Neotropikey - Interactive key and information resources for flowering plants of the Neotropics. http://www.kew.org/science/tropamerica/neotropikey/families/Portulacaceae.htm.
Click images to enlarge
Flower of Portulaca oleracea © Alexa Oliveira-Paes Coelho, Universidade Estadual de Feira de Santana, Bahia, Brasil.
Flower of Portulaca werdermannii © Alexa Oliveira-Paes Coelho, Universidade Estadual de Feira de Santana, Bahia, Brasil.
Flower of Talinum sp. © J.Wood, Darwin Initiative project
Flower of Talinum sp. © J.Wood, Darwin Initiative project