Difference between revisions of "Acacia"
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Revision as of 16:06, 30 March 2007
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 Acacia melanoxylon foliage and flowers | ||||||||||||||||
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| About 1,300; see List of Acacia species |
Acacia is a genus of shrubs and trees of Gondwanian origin belonging to the subfamily Mimosoideae of the family Fabaceae, first described from Africa by Linnaeus in 1773.
Acacias are also known as thorntrees or wattles, including the yellow-fever acacia and umbrella acacias.
There are roughly 1300 species of Acacia worldwide, about 950 of them native to Australia, with the remainder spread around the dry tropical to warm-temperate regions of both hemispheres, including Africa, southern Asia, and the Americas.
The genus Acacia however is apparently not monophyletic. This discovery has led to the breaking up of Acacia into five new genera as discussed in list of Acacia species.
General discussion
The northernmost species in the genus is Acacia greggii (Catclaw Acacia), reaching 37°10' N in southern Utah in the United States; the southernmost are Acacia dealbata (Silver Wattle), Acacia longifolia (Coast Wattle or Sydney Golden Wattle), Acacia mearnsii (Black Wattle), and Acacia melanoxylon (Blackwood), reaching 43°30' S in Tasmania, Australia, while Acacia caven (Espinillo Negro) reaches nearly as far south in northeastern Chubut Province of Argentina. Australian species are usually called wattles, while African and American species tend to be known as acacias.
The leaves of acacias are compound pinnate in general. In some species, however, more especially in the Australian and Pacific islands species, the leaflets are suppressed, and the leaf-stalks (petioles) become vertically flattened, and serve the purpose of leaves; these are known as phyllodes. The vertical orientation of the phyllodes protects them from intense sunlight, as with their edges towards the sky and earth they do not intercept light so fully as horizontally placed leaves. A few species (such as Acacia glaucoptera) lack leaves or phyllodes altogether, but possess instead cladodes, modified leaf-like photosynthetic stems functioning as leaves.
The small flowers have five very small petals, almost hidden by the long stamens, and are arranged in dense globular or cylindrical clusters; they are yellow or cream-colored in most species, whitish in some, even purple (as in Acacia purpureapetala) or red (in the recently grown cultivar Acacia leprosa 'Scarlet Blaze').
The plants often bear spines, especially those species growing in arid regions. These sometimes represent branches which have become short, hard and pungent, or sometimes leaf-stipules. Acacia armata is the Kangaroo-thorn of Australia, Acacia giraffae, the Camelthorn of Africa. In the Central American Acacia sphaerocephala, Acacia spadicigera, Acacia cornigera, and Acacia collinsii (collectively known as the bullthorn acacias), the large thorn-like stipules are hollow and afford shelter for ants, which feed on a secretion of sap on the leaf-stalk and small, lipid-rich food-bodies at the tips of the leaflets called Beltian bodies; in return they usually protect the plant against herbivores. Some species of ants will also trim competing p lants around the acacia, while other ant species will do nothing to benefit their host.
In common parlance the term "acacia" is occasionally misapplied to species of the genus Robinia, which also belongs in the pea family. Robinia pseudoacacia, an American species locally known as Black locust, is sometimes called "false acacia" in cultivation in Britain.
In Australia, Acacia species are sometimes used as food plants by the larvae of hepialid moths of the genus Aenetus including A. ligniveren. These burrow horizontally into the trunk then vertically down. Other Lepidoptera larvae which have been recorded feeding on Acacia include Brown-tail, Endoclita malabaricus and Turnip Moth. The leaf-mining larvae of some bucculatricid moths also feed on Acacia: Bucculatrix agilis feeds exclusively on Acacia horrida, Bucculatrix flexuosa feeds exclusively on Acacia nilotica.
Uses
Industrial and medicinal uses
Various species of acacia yield gum. True gum arabic is the product of Acacia Senegal, abundant in dry tropical west Africa from Senegal to northern Nigeria.
Acacia arabica is the gum-arabic tree of India, but yields a gum inferior to the true gum-arabic. The bark of Acacia arabica, under the name of babul or babool, is used in Scinde for tanning. In Ayurvedic medicine, babul is considered a remedy that is helpful for treating premature ejaculation.
The bark of various Australian species, known as wattles, is very rich in tannin and forms an important article of export; important species include Acacia pycnantha (Golden Wattle), Acacia decurrens (Tan Wattle), Acacia dealbata (Silver Wattle) and Acacia mearnsii (Black Wattle). Black Wattle is grown in plantations in South Africa. Most Australian acacia species introduced to South Africa, have become an enormous problem due to their naturally aggressive propagation. The pods of Acacia nilotica (under the name of neb-neb), and of other African species are also rich in tannin and used by tanners.
Most acacia species are used for valuable timber; such are Acacia melanoxylon (Blackwood) from Australia, which attains a great size; its wood is used for furniture, and takes a high polish; and Acacia homalophylla (Myall Wood, also Australian), which yields a fragrant timber, used for ornamental purposes. Acacia formosa supplies the valuable Cuban timber called sabicu. Acacia seyal is thought to be the shittah tree of the Bible, which supplied shittim-wood. This was used in the construction of the Ark of the Covenant. Acacia heterophylla from Réunion island, and Acacia koa from the Hawaiian Islands are excellent timber trees.
Acacia farnesiana is used in the perfume industry due to its strong fragrance.
An astringent medicine, called catechu or cutch, is procured from several species, but more especially from Acacia catechu, by boiling down the wood and evaporating the solution so as to get an extract.
Ornamental uses
A few species are widely grown as ornamentals in gardens; the most popular perhaps is Acacia dealbata (Silver Wattle), with its attractive glaucous to silvery leaves and bright yellow flowers; it is erroneously known as "mimosa" in some areas where it is cultivated, through confusion with the related genus Mimosa.
Culinary uses
Acacia seeds are often used for food and a variety of other products. The seeds of Acacia niopo, for instance, are roasted and used as snuff in South America.
In Burma, Laos and Thailand, the feathery shoots of Acacia pennata (common name cha-om, ชะอม) are used in soups, curries, omelette s, and stir-fries.
Honey made from the acacia flower is considered a delicacy, appreaciated for its mild flowery taste, soft running texture and glass like appearance. Acacia nectar can be an abundant enough to classify the honey as monofloral honey.
Pharmacological uses
Many Acacia species contain some psychoactive alkaloids of which DMT and NMT are the most prominent and useful. The leaves, stems and/or roots can be made into a brew together with some MAOI-containing plant to obtain an effect when taken orally. This could be seen as a kind of Ayahuasca. Maybe in relation to this effect, Egyptian mythology has associated the acacia tree with characteristics of the tree of life (cf. article on the Legend of Osiris and Isis). As a spiritual icon it is also one of the most powerful symbols in freemasonry, representing the eternal soul and purity of the soul.
Alkaloids in different species, from TiHKAL (by Alexander Shulgin): (There remains some question over whether any or all specimens of the following species would contain the alkaloids reported in TIHKAL, but it's a starting point. K Trouts books and notes on Acacia and tryptamines contain more recent information)
| Acacia baileyana | 0.02% tryptamine and β-carbolines, in the leaf |
| Acacia maidenii | DMT and NMT, in the stem bark |
| A. albida | DMT, in the leaf |
| A. confusa | DMT and NMT, in the leaf, stem and bark |
| Acacia cultriformis | tryptamine, in the leaf and stem |
| A. laeta | DMT, in the leaf |
| A. mellifera | DMT, in the leaf |
| Acacia melanoxylon | DMT, in the bark and leaf |
| Acacia nilotica | DMT, in the leaf |
| A. phlebophylla | DMT, in the leaf |
| A. podalyriaefolia | tryptamine, in the leaf |
| A. Senegal | DMT, in the leaf |
| A. seyal | DMT, in the leaf |
| A. sieberiana | DMT, in the leaf) |
| A. simplicifolia | DMT and NMT, in the leaf, stem and trunk bark |
| A. vestita | tryptamine, in the leaf and stem |
Acacia is also a very good and healthy soluble fiber, often used by IBS sufferers Template:Fact.
Species
There are over 1,300 species of Acacia. See List of Acacia species for a complete listing.
