Asystasia (PROSEA)
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Introduction |
Asystasia Blume
- Protologue: Bijdr. fl. Ned. Ind.: 796 (1826).
- Family: Acanthaceae
- Chromosome number: x= 13;A. gangeticasubsp.gangetica: 2n= 52,A. gangeticasubsp.micrantha: 2n= 26
Origin and geographic distribution
Asystasia comprises about 70 species, and is distributed in the tropics of the Old World. Few species occur in South-East Asia. A. gangetica is the most widely distributed species; it is planted as an ornamental and has become a pantropical weed.
Uses
A. gangetica is used in traditional medicine to treat swellings, sores, wounds, piles and rheumatism, and as a vermifuge. Also analgesic properties have been attributed to it. The leafy shoots are used in different parts of the world as a vegetable. A. nemorum has been applied to treat dry cough and eye infections.
A. dalzelliana Santapau is used in traditional medicine in India, especially for treating boils and swellings. Asystasia is grazed and easily digested by sheep, goats and cattle. Some species, particularly A. gangetica , are cultivated as an ornamental.
Properties
The presence of flavonoids has been demonstrated in some species, including A. gangetica . The leaves of A. gangetica do not have high levels of minerals and vitamins, but they show a high protein content; they are poor in tannins and oxalates. Both A. gangetica and A. nemorum showed a good complement of amino acids and satisfactory amounts of minerals, sugars, lipids and fibre, whereas antinutritional factors, such as trypsin and chymotrypsin inhibitors and cyanide, were not detected.
Botany
Erect or straggling herbs; stems thickened above the nodes. Leaves decussately opposite, simple and entire, with minute cystoliths, shortly to distinctly petiolate; stipules absent, but leaves connected by transverse ridges. Inflorescence an axillary and/or terminal, lax, spiciform raceme, often with secund flowers; bracts and bracteoles small. Flowers bisexual, 5-merous; calyx deeply partite, with narrow, subequal segments; corolla with cylindrical tube widened in upper part, limb spreading with imbricate, subequal, broadly ovate lobes, white or yellowish to pale blue or violet; stamens 4, inserted in the widened part of the corolla tube, didynamous, basally connate in pairs; ovary superior, 2-celled, style slender, with shortly 2-lobed stigma. Fruit a clavate to ellipsoid, stalked capsule, 4-seeded (sometimes less). Seeds ovate-orbicular, compressed, with sinuately incised margins, rugose or tuberculate, supported by hooked retinaculas.
The flowers are pollinated by insects, especially bees. It takes about one month from floral initiation to seed dispersal. The seeds are thrown as far as 6 m by an explosive mechanism on hot afternoons.
Two subspecies can be distinguished in A. gangetica : subsp. gangetica with pale cream, rosy cream, yellowish to pale or dark purple corolla with tube 2.5-3.5 cm long and spreading lobes, lower not pleated, and subsp. micrantha (Nees) Ensermu (synonym: A. intrusa (Forssk.) Nees) with pure white corolla with a large violet spur on lower part, tube 1.5-2 cm long and reflexed lobes, lower strongly pleated. Both subspecies can act as weeds, but subsp. micrantha is more serious as it is more vigorous and tends to become decumbent, producing a dense carpet of rooting stems and foliage, which smothers the rest of the ground vegetation.
Ecology
A. gangetica and A. nemorum occur in anthropogenic habitats such as roadsides, hedges, thickets, river banks and plantations, usually in more or less shaded localities in the lowland. A. gangetica can be a noxious weed (particularly subsp. micrantha ), especially in pineapple and oil palm, but also in cocoa, rubber and sugar cane plantations.
Management Asystasia can be propagated by seed, cuttings or by division of rooted stems. In-vitro propagation was successful for A. dalzelliana in India. It was regenerated on a Murashige and Skoog medium using callus cultures; rooting of regenerated shoots was achieved on the medium supplemented with 8 mg/l of indole-acetic acid, and the young plants were successfully transferred to soil. Control of weedy forms of A. gangetica can be achieved by controlled cattle grazing.
Genetic resources
Both Asystasia species treated here are not likely to be at risk of genetic erosion. More attention to the different forms of A. gangetica may be desirable, focusing on medicinal properties, weedy characteristics and ornamental value.
Prospects
Asystasia species are interesting medicinal plants, which are used in traditional medicine in different parts of the world. A. gangetica may have good prospects as a healthy vegetable, and perhaps also as an auxiliary plant in agriculture and as a forage species. However, the spreading of some forms as a serious weed needs attention.
Literature
236, 473, 760, 899, 908.
Selection of species
Authors
Sri Endreswari
