Avicennia L.

Avicennia is a genus of flowering plants currently placed in the bear's breeches family, Acanthaceae. It contains mangrove trees, which occur in the intertidal zones of estuarine areas and are characterized by aerial roots. It is commonly known as api api which in the Malay language means "fires", a reference to the fact that fireflies often congregate on these trees.^[2] Species of Avicennia occur worldwide south of the Tropic of Cancer.

The taxonomic placement of Avicennia is contentious. In some classifications it has been placed in the family Verbenaceae, but more recently has been placed by some botanists in the monogeneric family Avicenniaceae. Recent phylogenetic studies have suggested that Avicennia is derived from within Acanthaceae, and the genus is included in that family in the Angiosperm Phylogeny Group system.

Designation of species is made difficult by the great variations in form of Avicennia marina. Between eight and ten species are usually recognised, with Avicennia marina further divided into a number of subspecies.

The generic name honours Persian physician Avicenna (980-1037).^[3]

Description[edit]

Members of the genus are among the most salt tolerant mangroves and are often the first to colonise new deposits of sediment. The sap is salty and excess salt is secreted through the leaves. The spreading root system provides stability in shifting substrates. There are vertical roots called pneumatophores projecting from the mud. These are used in gas exchange as there is very little oxygen available in the mud. The flowers are fragrant and rich in nectar and are pollinated by insects. The embryos exhibit cryptovivipary, a process where they start to develop before the seed is shed but do not break through the outside of the fruit capsule.^[4]

Selected species[edit]

Propagule of Avicennia sp.

• Avicennia africana P.Beauv.
• Avicennia alba Blume
• Avicennia bicolor Standl.
• Avicennia eucalyptifolia (Valeton) Moldenke
• Avicennia germinans (L.) L. — Black Mangrove
• Avicennia integra N.C.Duke
• Avicennia marina (Forssk.) Vierh. — White or Grey Mangrove
• Avicennia nitida Jacq.
• Avicennia officinalis L.
• Avicennia rumphiana Hallier f.
• Avicennia schaueriana^[5]

See also[edit]

• Mangroves

References[edit]

Wikimedia Commons has media related to Avicennia.

Wikispecies has information related to: Avicennia

Further reading[edit]

• Boland, D. J. (1984). Forest Trees of Australia (Fourth edition revised and enlarged). CSIRO Publishing, Collingwood, Victoria, Australia. ISBN 0-643-05423-5. .
• Duke, N.C. (1991). "A Systematic Revision of the Mangrove Genus Avicennia (Avicenniaceae) in Australasia". Australian Systematic Botany 4 (2): 299–324. doi:10.1071/SB9910299. 
• 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 (abstract here).