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The Apocynaceae or dogbane family is a family of flowering plants, including trees, shrubs, herbs, or lianas.
Many species are tall trees found in the tropical rainforest, and most are from the tropics and subtropics, but some come from tropical dry, xeric environments. There are also some perennial herbs from temperate zones. Many of these plants have milky sap; and many species are poisonous if ingested. Some genera of Apocynaceae, such as Adenium however, have either clear and milky, latex sap, and others, such as Pachypodium, always have clear sap.
Taxonomy
The family, as currently recognized, includes some 1500 species divided in about 424 genera. The family Asclepiadaceae is now, according to AGP II included in the Apocynaceae (Endress & Bruyns, 2000).
There are five subfamilies:
- Rauvolfioideae
- Apocynoideae
- Periplocoideae
- Secamonoideae
- Asclepiadoideae
The former two sub-families were part of the Apocynaceae sensu stricto, whilst the latter three sub-families used to belong to the Asclepiadaceae. The Apocynaceae is the result of a conflation of the two families.
Distribution
Species in this family are distributed mainly in tropical regions:
- In the rainforests and swamps of India and Malaya: small to very tall evergreen trees, often with buttress roots, such as Alstonia and Dyer.
- In northern Australia: small evergreen trees such as Cerbera and Ochrosia.
- In deciduous forests of Africa and India: smaller trees such as Carissa, Wrightia and Holarrhena.
- In tropical America, India, Myanmar and Malaya: evergreen trees and shrubs, such as Rauwolfia, Tabernaemontana and Acokanthera.
- In Central America: Plumeria, or the frangipani, with its waxy white or pink flowers and a sweet scent.
- In South America, Africa and Madagascar: many lianas such as Landolphia.
- In the Mediterranean region: Nerium, with the well-known oleander or Be-still tree (Nerium oleander).
- The only genera found in temperate Europe away from the Mediterranean are Vinca (Apocynoideae) and Vincetoxicum (Asclepiadoideae).
- In North America: Apocynum, dog bane or Indian hemp, including Apocynum cannabinum, a traditional source of fiber.
- In continental southern Africa (Angola, Botswana, Mozambique, South Africa, Swaziland, and Zimbabwe) and Madgascar, except for the humid evergreen forest of the eastern side of Madgascar, and never above 2000 m for the entire island: Pachypodium.
Characteristics
The leaves are simple, usually opposite and decussate, or whorled; lacking stipules. Flowers are usually showy, radially symmetrical (actinomorphic), aggregated in cymose or racemose inflorescences (rarely fasciculate or solitary). They are perfect (bisexual), with a synsepalous, 5-lobed calyx. Inflorescences are terminal or axillary. The stamens are inserted on the inside of the corolla tube. The ovary is usually superior.
The fruit is a drupe, a berry, a capsule or a follicle.
Genera
Apocynoideae
The following genera used to belong to the family Asclepiadaceae :
- Araujia
- Asclepias (subfamily Asclepiadoideae)
- Caralluma
- Ceropegia
- Cionura
- Cynanchum
- Periploca (Subfamily Periplocoideae)
- Vincetoxicum
Uses
Several plants of this family had economic uses in the past.
The genera Carpodinus, Landolphia, Hancornia, Funtumia and Mascarenhasia were used as a commercial source of inferior rubber.
The juice of Acokanthera species such as A. venenata and the milky juice of the Namibian Pachypodium has been used as venom for arrow tips by the Bushmen. Some sources (Rapananrivo et al. on p. 5) state that Pachypodium do not have a milky sap.
Several genera are grown as ornamental plants, including Amsonia (bluestar), Nerium (oleander), Vinca (periwinkle), Carissa (Natal plum, an edible fruit), Allamanda (golden trumpet), Plumeria (frangipani), Thevetia (lucky nut), Mandevilla (Savannah flower).
Rauvolfia cafra is the Quinine tree. Rauvolfia serpentina or Indian Snakeroot yields the alkaloids reserpine and rescinnamine.
Some are sources of drugs, such as cardiac glycosides, affecting the heart function, including Acokanthera, Apocynum, Cerbera, Nerium, Thevetia and Strophantus.
The genus Apocynum was used as a source of fiber by Native Americans.
References
- Rapanarivo, S.H.J.V; Lavranos, J.J; Leeuwenberg, A.J.M.; AND Röösli, W. revision of the genus Pachypodium. S.H.J.V Rapanarivo and A.J.M Leeuwenberg; habitats of Pachyopdium species. S.H.J.V Rapanarivo; W. Röösli (A.A. Balkema: Rotterdam, Brookfeild, 1999 p. 5) ". . . Adenium species have either clear sap or white latex. Pachypodium . . . always has clear sap".
External links
- Apocynaceae in L. Watson and M.J. Dallwitz (1992 onwards). The families of flowering plants: descriptions, illustrations, identification, information retrieval. http://delta-intkey.com
- UVSC Herbarium - Apocynaceae
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