Scientific name: Asystasia gangetica
Family: Acanthaceae
Asystasia means inconsistency and relates to the fact that the corolla is more or less regular which is unusual in the family Acanthaceae. The word gangetica is derived from the Ganga river in India where it is presumed the species occurs.
Origin and Distribution:
The species A. gangetica is native to tropical Malaysia, India, and Africa, but has been introduced into tropical areas in North, Central and South America, Hawaii, West Indies, and Australia as an ornamental herb and eventually escapes into natural and disturbed areas.
Sub Species:
- A. g. gangetica, has larger (30–40 mm long) blue or mauve flowers.
- A. g. micrantha, has smaller (up to 25 mm long.) white flowers with purple markings on the lower lip.
Plant Characters:
Stem:
- Ganges primrose is an attractive, fast-growing, spreading, herbaceous ground cover that grows from 30 cm to 60 cm in height. It is semi-hardy, and young plants require protection in areas of heavy frost. In tropical areas it can grow rampantly. The stems root easily at the nodes.
Leaves:
- Leaves are The leaves are simple and opposite and dark green.
Flowers:
- It produces a blue or mauve - coloured flowers in A. g. gangetica and in A. g. micrantha with tessellated purple markings on the palate (lower petal of the corolla) in spring and summer.
- Flowers are produced over a long period.
Fruits:
- Fruits are capsules with brown seeds.
- The fruit is an explosive capsule which starts out green in colour, but dries to brown after opening.
- The seeds are then expelled explosively upon ripening via hooked retinacula.
Climatic requirments:
- Grows best in the humid areas of the tropics.
- It grows in areas where the mean annual rainfall is in the range 1,200 - 2,100mm.
- Plants may not survive without irrigation in areas with a dry season of 4 months or more.
Sunlight:
- This is a shade-loving plant, optimum photosynthesis occurs between 33 - 50% full sunlight and the plant can grow, albeit slowly, with only 10% sunlight.
Soil:
- An easily grown plant, preferring a relatively dry soil and a position in full sun or partial shade.
- Thrives on sedentary soils, coastal alluvium, sandy loams and clays
- Plants can succeed in peat soils with 85% organic matter and a pH as low as 3.5 - 4.5.
- Established plants are drought tolerant.
- Seeds
- Cuttings with 1 - 3 nodes.
- Single-node cuttings, buried in the soil, can produce flowers and fruit within 6 weeks.
- Division of rooted stems.
Uses:
Edible uses:
- Leaves and young shoots - cooked.
- The leaves and flowers are eaten as a pot herb.
- The leaves are consumed as a popular vegetable, mixed with beans, groundnut or sesame paste.
Medicinal uses:
- The plant is used as a traditional medicine in many parts of its range
- Chinese medicine shops sell it as 'kaw kua chai'
- Modern investigation of the plant has shown that it contains several active compounds.
- Phytochemical screening yielded carbohydrates, proteins, alkaloids, tannins, steroidal saponins, flavonoids and triterpenoids. Another study yielded a megastigmane glucoside, asysgangoside, from the aerial parts, with other known compounds.
- The leaf extract has been shown to relax histamine-precontracted trachial strips and to exhibit antiinflammatory activity.
- The study justified its use in Nigerian folk medicine as a treatment for asthma.
- Another study suggests that the leaves provide benefit through a bronchospasmolytic effect of the terpenoid compounds.
- The juice of the plant, combined with lime and onion juice, is recommended for dry coughs with an irritated throat and discomfort in the chest.
- The sap of the plant is used as a vermifuge and is applied externally to swellings and rheumatic joints.
- Sap of the leaf is put up the nostrils to stop a nose-bleed, and is also used as an embrocation on a sore neck.
- A leaf-decoction is used in the treatment of fever-aches, epilepsy, stomach-pains, heart-pains and urethral discharge.
- The pulped leaf is used as a suppository for piles.
- The leaves and flowers are used as intestinal astringent.
- The leaves are used in the treatment of asthma.
- The plant is popularly used in many parts of Africa to ease childbirth. It is boiled and the infusion mixed with peppers then used as a syringe (vaginal douche or enema?) during the later months of pregnancy in order to ease childbirth pains. The infusion is also drunk for the same purpose.
- In Congo leaf-sap is placed on the stomach of women in childbirth to facilitate labour
- The powdered roots are a general remedy for stomach-pains and are used as an emetic in treating snake-bite.
Agro forestry usse:
The plant has weak stems forms a good ground cover and make a dense mat and so form a good, weed-excluding ground cover. The plant is useful in slopes where it can help prevent soil erosion.(The plant is not generally regarded as useful in plantations of crops such as cocoa, oil palm or rubber, nor amongst vegetables or field crops.) It is liked as a naturally occurring plantation cover in some orchards, however, because the bees which pollinate the flowers of fruit trees such as starfruit or durian, are attracted to the orchard by the flowers of this plant.
Some other uses:
The plant is used as a soap-substitute. It froths in water, suggesting the presence of saponins.
Ecological Significance:
- This is an important plant for honeybees, butterflies and other insects.
- In southern Africa there are at least seven species of butterfly and moth that use A. g. micrantha as a larval foodplant; Junonia oenone, Junonia hierta, Junonia natalica, Junonia terea, Protogoniomorpha parhassus, Hypolimnas misippus and Microplexia costimaculalis.
- The vigorous growth of A. g. micrantha in tropical regions makes it a weed which can smother certain indigenous vegetation where it has been introduced.
References:
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