Pisonia (PROSEA)
Introduction |
Pisonia L.
- Protologue: Sp. pl. 2: 1026 (1753); Gen. pl. ed. 5: 451 (1754).
- Family: Nyctaginaceae
- Chromosome number: x= unknown; P. umbellifera: 2n= about 112
Major species
- Pisonia aculeata L.,
- P. grandis R.Br.
Origin and geographic distribution
Pisonia comprises about 35 species, mostly in the Americas (about 20), 1 pantropical (P. aculeata), the others in the Old World tropics, from the Indian Ocean Islands to continental Asia, Malesia and Oceania. In Malesia, 8 species occur, of which 5 also in Australia and/or the Oceanic islands.
Uses
In the Philippines, a decoction of the fresh leaves of P. aculeata is used to wash scabies. In Thailand, the stem is macerated in rice alcohol and taken as a tonic, and the leaves are used for inflammations. In India, the bark and leaves are used as a counterirritant for swellings and rheumatic pains, as are the leaves of P. umbellifera. The juice mixed with other ingredients is given to children suffering from pulmonary complaints. In Mexico, P. aculeata is officially listed in its Pharmacopoeia. Small whole plants are boiled and the decoction used as a bath for patients with fever. The leaves or bark in decoction are taken internally or externally as a treatment for rheumatic and articular pains.
In Indonesia, the leaves of P. grandis cultivar "Alba" are crushed or heated and applied to swellings or open ulcers, corns, calluses, or applied for oedema of the legs. In India, the fresh leaves of "Alba" are considered diuretic and, moistened with eau-de-Cologne, they are used to subdue inflammation caused by filariasis in the limbs. The crushed bark, mixed with vinegar, is rubbed onto legs with cramps, and the root is considered purgative. In India, tea from the boiled bark of P. umbellifera is sometimes given as a tonic to newborn babies.
In Indonesia, the green bark of P. longirostris Teijsm. & Binnend. is sometimes burnt, powdered and mixed with coconut oil to make a balm for fresh wounds. The wood is too soft to be of any use.
In Java, the wild P. grandis has long been considered a plant with magical properties, the flowers being used at the coronation of a sultan, his wife eating them in order to obtain a fortunate son. Young leaves of the cultivar "Alba" are a popular vegetable, cooked with meat but also as a salad. In the Philippines, "Alba" is cultivated as an ornamental tree for its yellow leaves. In India, P. aculeata is also planted as an impenetrable hedge.
In the Philippines, P. umbellifera is also cultivated as an ornamental, because of its numerous fragrant flowers, and in Spain, North America and Australia it is therefore sometimes cultivated as a pot plant.
Small birds and animals can be trapped by the sticky fruits of Pisonia, and sometimes clusters of fruits are therefore placed under trees.
Production and international trade
Most Pisonia are not internationally traded. Only P. grandis cultivar "Alba" has been planted in several Asian countries, and leaves are sold in markets as a vegetable. Statistics on trade are not available.
Properties
From the leaves of P. umbellifera 6 saponins have been isolated; 3 of them are oleanolic acid saponins, and 2 contain an unusual seco-glycopyranosyl moiety. In a general screening, an extract of the leaves showed significant bactericidal activity. From Sri Lanka, toxic effects including vomiting, diarrhoea and abdominal pain from eating the leaves have been reported.
In India, the leaves of P. grandis cultivar "Alba" are given to school children as a calcium supplement. The leaves also contain some other nutrients, e.g. iron, phosphate andβ-carotene.
Description
- Erect shrubs or trees, sometimes dioecious, up to 30 m tall, usually unarmed, sympodially branched, glabrescent; wood and bark soft and spongious, brittle, pith hardly distinct from the wood.
- Leaves (sub)opposite or alternate, simple, dull, midrib flat above; petiole present; stipules absent. Inflorescence normally a small or large, axillary or terminal thyrse, 2-8 times (sub)umbellately branched; pedicel 0.5-10 mm long, bracts caducous.
- Flowers uni- or bisexual, male and female flowers sometimes of different shape; perianth valvate in bud, somewhat fleshy, campanulate, tubular, urceolate or funnel-shaped, 5(-10)-lobed, basal part tubular, coriaceous, persistent, accrescent after anthesis, apical part often whitish, often circumsessile caducous, often with glands; stamens 2-40, in 1-2 whorls, mostly exserted, sterile in female flowers; ovary superior, subsessile, elongate, apex narrowed, style longer than ovary, stigma with short lobes or fimbriate.
- Fruit a coriaceous anthocarp, smooth or 5-ribbed, sometimes viscid through lengthwise rows of glands, sometimes with a long beak.
- Seed oblong, with a deep longitudinal furrow, embryo straight, cotyledons recurved, surrounding the endosperm.
Growth and development
Dispersal of Pisonia is effected through the sticky fruits which attach themselves to birds.
It is suggested that P. grandis can only maintain itself in quantity on islands where bird colonies produce enough guano, as phosphate seems to be a limiting factor for its regeneration. As the root system is shallow, the wood brittle and the leafy crown large, the trees often topple over during storms, but shoots and suckers are frequently formed.
Other botanical information
It is said that the male trees of P. grandis cultivar "Alba" are rarely cultivated as their leaves are darker and look less appetizing. P. grandis, however, has bisexual flowers, and because "Alba" rarely flowers, a darker-leaved specimen could be just a variation. Another explanation could be a synonymy problem, because a synonym of P. grandis is P. excelsa (non Blume) Corner, while P. excelsa Blume is a synonym of P. umbellifera. In older floras the name P. excelsa occurs with "Alba" as a form of it, having male and female flowers. "Alba" could thus well be a cultivar of P. umbellifera, which could explain the occurrence of male and female trees, if the tree is dioecious.
Ecology
Many Pisonia species are coastal, and occur often on (coral) islands in the Pacific. Some prefer (swampy) rainforest though and river banks, often on limestone or sandy clay, at low altitudes. P. grandis is a characteristic component of the Barringtonia formation, a vegetation type important on small coral islands. It does not tolerate shade and can form dominant pioneer groves on bird-inhabited islands.
Propagation and planting
Pisonia is propagated by seed although cultivar "Alba", which rarely flowers, is mainly propagated by stem cuttings, which root easily. In vitro propagation seems to be a good alternative. The axillary buds are cultured on Murashige and Skoog (MS) medium supplemented with the cytokinins benzyladenine and kinetin (1 mg/l each), resulting in 8-10 multiple shoots. Roots were induced on half strength MS medium, fortified with the auxins indole butyric acid and naphthalene acetic acid (0.5-1 mg/l) each. Regenerated plantlets were acclimatized on a sandy soil medium before being transferred to field conditions, where 95% of the plants survived.
Husbandry
For maintaining a continuous supply of young leaves of P. grandis, both the wild type and "Alba" need to be pruned regularly.
Harvesting
The parts of Pisonia used, often the leaves, are harvested when needed.
Genetic resources and breeding
As many Pisonia are restricted to coastal regions, exploitation or disturbance by man of these areas might result in the disappearance of their natural habitat, and of Pisonia as well.
P. grandis cultivar "Alba" is widely cultivated, and does not seem to be at risk of genetic erosion. No breeding programmes of Pisonia for medicinal purposes are known to exist. P. umbellata cv. "Variegata" is cultivated in Europe as a greenhouse ornamental.
Prospects
Since little information is available on the phytochemistry and pharmacology of Pisonia, more research is needed to evaluate its possible medicinal potential.
Literature
- Burkill, I.H., 1966. A dictionary of the economic products of the Malay Peninsula. Revised reprint. Vol. 2. Ministry of Agriculture and Co-operatives, Kuala Lumpur, Malaysia. p. 1755.
- Jagadishchandra, K.S., Rachappaji, S., Gowda, K.R.D. & Tharasaraswathi, K.J., 1999. In vitro propagation of Pisonia alba (L.) Spanoghe (lettuce tree), a threatened species. Phytomorphology 49(1): 43-47.
- Lavaud, C., Beauviere, S., Massiot, G., Le Men Oliver, L. & Bourdy, G., 1996. Saponins from Pisonia umbellifera. Phytochemistry 43(1): 189-194.
- Ochse, J.J. & Bakhuizen van den Brink, R.C., 1980. Vegetables of the Dutch East Indies. 3rd English edition (translation of "Indische groenten", 1931). Asher & Co., Amsterdam, the Netherlands. pp. 537-541.
- Quisumbing, E., 1978. Medicinal plants of the Philippines. Katha Publishing Co., Quezon City, the Philippines. pp. 277-278.
- Stemmerik, J.F., 1964. Pisonia. In: van Steenis, C.G.G.J. (Editor): Flora Malesiana. Series 1, Vol. 6. Noordhoff-Kolff, Djakarta, Indonesia. pp. 457-468.
Selection of species
Authors
- G.H. Schmelzer & N. Bunyapraphatsara