Difference between revisions of "Acanthaceae"
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Revision as of 12:31, 30 August 2007
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The family Acanthaceae (or Acanthus family) is a taxon of dicotyledonous flowering plants containing almost 250 genera and about 2500 species.
Most are tropical herbs, shrubs, or twining vines; some are epiphytes. Only a few species are distributed in temperate regions. The four main centres of distribution are Indonesia and Malaysia, Africa, Brasil and Central America. The representatives of the family can be found in nearly every habitat, including dense or open forests, in scrublands, on wet fields and valleys, at the sea coast and in marine areas, and in swamps and as an element of mangrove woods.
Plants in this family have simple, opposite, decussate leaves with entire (or sometimes toothed, lobed, or spiny) margins, and without stipules. The leaves may contain cystoliths, or calcium carbonate concretions, seen as streaks on the surface. The flowers are perfect, zygomorphic to nearly actinomorphic, these arranged in an inflorescence that is either a spike, raceme, or cyme. Typically there is a colorful bract subtending each flower; in some species the bract is large and showy. The calyx is usually 4-5 lobed; the corolla tubular, 2-lipped or 5-lobed; stamens either 2 or 4 arranged in pairs and inserted on the corolla; and the ovary superior, 2-carpellate, with axile placentation. The fruit is a two-celled capsule, dehiscing somewhat explosively. In most species, the seeds are attached to a small, hooked stalk (a modified funiculus called a jaculator) that ejects them from the capsule.
A species well-known to temperate gardeners is Acanthus mollis or Bear's breeches, a herbaceous perennial plant with big leaves and flower spikes up to 2 m tall. Tropical genera familiar to gardeners include Thunbergia and Justicia.
Avicennia, usually placed in Verbenaceae or in its own family, Avicenniaceae, is included in Acanthaceae by the Angiosperm Phylogeny Group on the basis of molecular phylogenetic studies that show it to be associated with this family.
Selected genera
There are 246 accepted genera according to Germplasm Resources Information Network (GRIN).
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Photo Gallery
Leaf of the Acanthaceae "Nerve Plant", Fittonia verschaffeltii
Chinese Violet (Asystasia gangetica)
Peristrophe speciosa
References
- ↑ Wortley, A.H., Harris, D.J. & Scotland, R.W. (2007). "On the Taxonomy and Phylogenetic Position of Thomandersia.". Systematic Botany 32 (2): 415-444. doi:10.1600/036364407781179716.
- Schwarzbach, Andrea E. and McDade, Lucinda A. (2002). "Phylogenetic relationships of the mangrove family Avicenniaceae based on chloroplast and nuclear ribosomal DNA sequences". Systematic Botany 27: 84–98.
External links
- Acanthaceae in L. Watson and M.J. Dallwitz (1992 onwards). The families of flowering plants: descriptions, illustrations, identification, information retrieval.
- Tree of Life Acanthaceae
