Monochoria (PROSEA)

Plant Resources of South-East Asia Introduction

List of species

Monochoria K.B. Presl

Protologue: Reliq. haenk. 1: 127 (1827).

Family: Pontederiaceae

Chromosome number: No basic chromosome number (x) exists. All species show a complex of polyploidy with associated aneuploidy. The most common numbers are 2n= 28 for M. hastata and 2n= 52 for M. vaginalis.

Major species and synonyms

• Monochoria hastata (L.) Solms-Laubach, in: A. DC., Monogr. phan. 4: 523 (1883), synonyms: Pontederia hastata L. (1753), Monochoria hastaefolia K.B. Presl (1827).

• Monochoria vaginalis (N.L. Burman) Kunth, Enum. plant. 4: 134 (1843), synonyms: Pontederia vaginalis N.L. Burman (1768), P. pauciflora Blume (1827), Gomphima vaginalis (N.L. Burman) Rafinesque (1837).

Vernacular names

M. hastata:

• hastate-leaved pondweed, arrow-leaved monochoria (En)
• Indonesia: eceng gede, bia-bia, wewehan
• Malaysia: chacha layar, kangkong air
• Papua New Guinea: maoa
• Philippines: gabi-gabihan (Tagalog), kasal-kasal, payaw-payaw (Bisaya)
• Cambodia: chrach
• Laos: 'ii hin
• Thailand: phaktop-thai, phaktop (central), phakpong (central)
• Vietnam: rau mác.

M. vaginalis:

• oval-leaved pondweed, oval-leaved monochoria, pickerel weed (En)
• Indonesia: eceng padi, eceng leutik, wewehan
• Malaysia: kelayar, keladi agak
• Philippines: biga-bigaan (Tagalog), gabing uwak (Tagalog), bilagut (Ilocano)
• Cambodia: chrach
• Thailand: khakhiat, ninlabon (central), phakhin (north-eastern)
• Vietnam: rau chóc, rau mác lá thon.

Origin and geographic distribution

Monochoria is a small genus comprising 8 species, all native in the warmer parts of the Old World (2 in Africa, 4 in Asia, 2 in Australia). M. hastata is native in tropical South and South-East Asia extending to northern Australia. M. vaginalis is native in South Asia, throughout South-East Asia, extending also to China, Japan, Fiji islands and northern Australia. It has become naturalized in Hawaii, California and in rice fields in Russia and Italy. It is sometimes cultivated as a vegetable.

Uses

In southern and eastern Asia M. vaginalis and to a lesser degree M. hastata are eaten as vegetables. Usually the leaves and stems are cooked but in South-East Asia the inflorescences are sometimes eaten raw. In the Philippines (Luzon) rhizomes of M. vaginalis are said to be eaten, but M. vaginalis is rarely rhizomatous. The rhizomes of M. hastata are cooked for cattle feed in Sulawesi (Indonesia). Both species have also medicinal applications. The pulverized rhizome of M. hastata is applied to relieve itching. The leaves of M. vaginalis pounded and mixed with turmeric (Curcuma longa L.) and Portulaca pilosa L. are applied to boils after they have burst. The juice of the roots is used to treat stomach and liver disturbances and also to cure asthma and toothache. The juice of the leaves is used for curing coughs. Sometimes Monochoria species are planted as ornamentals.

Production and international trade

Both pondweed species are occasionally sold in local markets in Indonesia, Malaysia and Thailand, but production data are not recorded.

Properties

The following composition per 100 g edible portion has been reported for M. vaginalis : water 88.6 g, protein 1.0 g, fat 0.2 g, carbohydrates 3.8 g, vitamin A 1000 IU, vitamin B₁ 0.08 mg, vitamin C 30 mg, Ca 80 mg, P 45 mg, and Fe 3.7 mg. The energy value is 75 kJ/100 g.

Description

• Erect, ascending or occasionally creeping, emergent or floating annual or perennial herbs, growing in fresh water, glabrous.
• Stems sometimes rhizomatous, roots adventitious, fibrous.
• Leaves radical, simple, with long petioles.
• Inflorescences terminal, few- or many-flowered, paniculate, raceme- or umbel-like, borne above or below the leaves on naked, elongated, unbranched inflorescence stalks which terminate with 2 opposed spathes; the lower spathe (bract) leaf-like with sheath, petiole and blade; the upper spathe (bracteole) enclosed within the lower one at anthesis or exposed; the lower spathe often so dominant that the inflorescence appears to burst out of a normal-looking petiole.
• Flowers bisexual, showy, withering within one day; perianth of 6 tepals, free, blue to white with green midribs, persistent in fruit; stamens 6; ovary 3-celled, stigma entire or lobed.
• Fruit a loculicidal capsule, ellipsoidal to subglobular, many seeded.
• Seed cylindrical to ovoid or subglobular with 8-14 longitudinal ribs or wings, brown to black.

M. hastata.

• Rhizomatous perennial with strong and robust stems, 30 cm or more long, up to 2 cm in diameter.
• Petiole up to 90 cm long, bright red below; leaf-blade sagittate to hastate, up to 20 cm × 15 cm.
• Inflorescence sub-umbellate, (10-)20-30(-60)-flowered, appearing to burst out of a normal-looking petiole, peduncle up to 65 cm long; lower spathe with sheath 3-8 cm long, petiole 3-12 cm long, blade sagittate or hastate, 7-18 cm × 4-14 cm; upper spathe without petiole and blade, membranous, up to 5 cm long; pedicel up to 3 cm long; tepals 10-18 mm × 7-8 mm, twisted around the fruit; stamens 6, 5 yellow, 1 blue; style 5-6 mm long.
• Fruit ovoid, 12 mm × 9 mm.
• Seed ovoid, ca. 1 mm × 0.5 mm, 10-ribbed.

M. vaginalis.

• Annual, rarely rhizomatous, stems creeping or ascending.
• Petiole up to 50 cm long; leaf-blade linear or lanceolate to ovate, 2-21 cm × 0.2-10 cm.
• Inflorescence very variable, with (1-)2-7(-20) flowers becoming strongly deflexed in fruit; peduncle 2-50 cm long; lower spathe with sheath 1-3.7 cm long, petiole 0.5-7 cm, blade linear or lanceolate to ovate or cordate, 1.3-10 cm × 0.3-15 cm; upper spathe 1-3.5 cm long; pedicel up to 3 cm long; tepals 8-15 mm × 8 mm; stamens 6, 5 yellow, 1 blue; style 2-5 mm long.
• Fruit ellipsoidal to ovoid, 0.8-1.2 mm × 0.4-0.7 mm.
• Seed ovoid, 0.5-1 mm × 0.3-6 mm with 8-10 narrow wings.

Growth and development

• M. hastata can attain a height of up to 2-3 m during the rains, adjusting its height to the rise of the water level. Inflorescence and leaf-blades are always borne above the water level. Anthesis takes place in the morning. Flowers are self-compatible and largely self-pollinated. The seeds take 10-15 days to develop. Germination takes place under water, but dispersal is mostly by fragmentation of the rhizome. The plants usually grow in clumps. In the subtropics the above-ground parts die off in winter.

• M. vaginalis is extremely variable in height, from 3 cm to over 50 cm. It is usually annual but in permanent water may persist for more than one year. There is no particular flowering period; it flowers as long as the habitat remains wet and the competition with other species is not too strong. Anthesis takes place in the morning, at midday the flowers wither. After fertilization the young infructescence bends downwards and the fruits often develop under water. The capsules are liberated as units. Seeds germinate under water. Large robust plants (in water) tend to have inflorescences bearing 7 or more flowers, while small, terrestrial plants may have only 1 or 2 flowers. Under stress conditions the leaf-blades tend to be linear or lanceolate, normally they are ovate.

Ecology

Both species grow in sweet water swamps, along ditches, in shallow pools, on canal banks, and particularly in flooded rice fields where the plants are often the commonest weeds. M. vaginalis, the most common of the two species, occurs from the plains up to 1500 m, whereas M. hastata occurs up to 700 m altitude. M. vaginalis is commonest in eutrophic water, but may be found also in brackish and oligotrophic water. It is a stress-tolerant ruderal.

Agronomy

Cultivation is hardly practised, but advantage is taken of naturally occurring populations. Both species can be propagated by seed, but more easily by partition, taking off lateral shoots. However, this is hardly necessary in localities where pondweed already occurs, because both species multiply spontaneously. They are typical weeds in irrigated rice. When the fields dry out, pondweed dies off completely, but new plants develop readily from seeds in the following inundation period. In constantly swampy localities, both species can reach old age and may attain large dimensions. At high population densities, pondweed is competitive and can reduce rice yields considerably.

Genetic resources and breeding

No germplasm collections or breeding programmes exist.

Prospects

Intensification of rice cultivation, in particular the use of herbicides, reduces the incidence of weedy companions such as pondweed. It would be worthwhile to try out controlled cultivation as a sole crop or in combination with similar vegetable crops such as Limnocharis flava (L.) Buchenau, possibly in an integrated pisciculture system.

Literature

• Backer, C.A., 1951. Pontederiaceae. In: van Steenis, C.G.G.J. et al. (Editors), 1950- . Flora Malesiana. Series 1. Vol. 4. Noordhoff-Kolff, Djakarta, Indonesia. pp. 255-259.
• Boonkird, K., 1975. Pontederiaceae. Thai Forest Bulletin (Botany) 9: 12-13.
• Cook, C.D.K., 1989. Taxonomic revision of Monochoria (Pontederiaceae). In: Tan, K. (Editor): The Davis & Hedge Festschrift. University Press, Edinburgh, United Kingdom. pp. 149-184.
• 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. 612-614.
• Soerjani, M., Kostermans, A.J.G.H. & Tjitrosoepomo, G., 1987. Weeds of rice in Indonesia. Balai Pustaka, Jakarta, Indonesia. pp. 486-489.

Authors

• T. Boonkerd, B. Na Songkhla & W. Thephuttee