Eichhornia crassipes (PROSEA)

Plant Resources of South-East Asia Introduction

List of species

Eichhornia crassipes (Martius) Solms

Protologue: A. DC., Mon. Phan. 4: 527 (1883).

Family: Pontederiaceae

Chromosome number: 2n= 32

Synonyms

• Pontederia crassipes Martius (1823),
• Eichhornia speciosa Kunth (1843).

Vernacular names

• Water hyacinth (En)
• Jacinthe d'eau (Fr)
• Indonesia: eceng gondok (general, Sundanese), kembang bopong (Javanese), kelipuk (Palembang)
• Malaysia: keladi bunting, kemeling telur, bunga jamban
• Philippines: water lily
• Burma (Myanmar): beda-bin, ye-padauk
• Cambodia: kâmplaôk
• Laos: tôb po:ng
• Thailand: phaktop-chawa
• Vietnam: lục bình, bèo nhật bản.

Origin and geographic distribution

Water hyacinth is native to tropical South America. During the latter half of the 19th Century it spread beyond its original habitat as an ornamental and subsequently became naturalized in tropical and subtropical areas around the world. It was first introduced into South-East Asia in 1894 to the Bogor Botanical Garden in Java, from where it spread over the Indonesian Archipelago. It was introduced into Singapore from Hong Kong in 1903 by the Chinese. The plant arrived in the Philippines in 1912. From Bangkok, where it was introduced from Java, water hyacinth spread over the Chao Phraya delta and along the Mekong river and adjacent regions in Vietnam, Cambodia and Laos, where it was already causing concern in 1908. Water hyacinth was first reported from Papua New Guinea in 1962.

Uses

Water hyacinth is considered one of the world's most troublesome weeds because of its rapid growth and formation of dense, impenetrable mats of vegetation which hinder navigation and fishing, obstruct irrigation and drainage of farm land and crowd out other plants. To decrease the costs of water hyacinth control and the negative effects of chemical control, various studies have been carried out on possible ways of using it. However, it is difficult to harvest and process large masses with a very high water content (90-96%) in an economical way. The simplest and most practical routine use of water hyacinth is as green manure, compost and mulch for soil improvement. It is sometimes used as a fodder, and in South and South-East Asia it is common to see water buffaloes grazing it. It is further used in fish traps, where fish are trapped in nets under small clusters of water hyacinth, and to produce paper and biogas by means of anaerobic fermentation. In biogas production the high moisture content in the plants is an advantage, because moisture is needed for the fermentation process. One hectare of water hyacinth produces about 70 000 m³ of biogas, one kg of dry material producing about 370 l. Increasing attention is being given to its potential as a water-clearing agent. The roots trap large amounts of dispersed organic and inorganic particles and efficiently remove minerals, including several heavy metals and radio-active elements. The feasibility of using water hyacinth as a substrate for mushroom cultivation is being studied. In some countries in the temperate zones water hyacinth is cultivated as an indoor plant. In Indonesia a home industry has been established producing handicrafts such as lady handbags, slippers, hats, and vests from the elongated dried petioles of water hyacinth.

Properties

The different organic constituents in water hyacinth are nutritionally comparable to those of any other forage. The protein content varies from 7.4-18.1% on a dry weight basis. The concentration of the basic elements is in the same range as in terrestrial forage plants whereas those of iron, sodium, potassium and calcium are relatively high. Per 100 g dry matter the proximate composition is: Fe 0.3 g, Na 0.4 g, K 4.6 g, Ca 1.3 g. The nitrogen and phosphorous concentration as well as the concentrations of heavy metals are directly correlated with the concentrations in the water. It is advisable to mix water hyacinth with other fodders, because it can contain high levels of K and Cl and its P levels are often inadequate.

Description

• Perennial herb, 30-60 cm tall, rarely taller, floating free or rooting in the mud of shallow waters. Root system mainly composed of adventitious roots (blackish with age) originating from the rhizome and bearing many laterals; rhizome consisting of several nodes and internodes, each node with a leaf, and emitting stolons.
• Leaves consist of a petiole, a thin part between petiole and blade, called isthmus, and a blade; petiole elongated (when plants are rooted in the soil or growing in dense stands) or forming a bulbous float; blade broadly ovate or rhomboid with an almost cordate base.
• Inflorescence a long-peduncled, axillary spike subtended by two bracts, with 5-35 spirally arranged flowers, usually simultaneously expanding and withering.
• Flowers zygomorphic, with a perianth of 6 pale-purple segments; the posterior segment largest, about 3 cm long, with a bright yellow, blue-bordered median blotch; stamens 6, variable in length; ovary superior, conical, trilocular with numerous ovules, style terminated by an almost capitate stigma at medium height between the anthers of long and short filaments.
• Fruit a dehiscent capsule containing a variable number of seeds.
• Seed ovoid, 1 mm x 0.5 mm, ribbed.

Growth and development

Propagation is mainly by vegetative means, i.e. through stolons. Only where it occurs in seasonally dry habitats is multiplication by seed important. Under favourable conditions growth is very rapid. The area under plant cover may double within a period of 6-15 days. In general, water hyacinth flowers profusely, both under long- and short-day conditions. Flowers of water hyacinth are tristylous, the most common form, also in South-East Asia, has 3 long and 3 short stamens and an intermediate style. Other forms, which are mostly absent outside the Amazon basin, have either 3 long and 3 intermediate stamens and a short style or a long style and 3 intermediate and 3 short stamens. In the natural habitat, pollination is carried out by pollen-collecting and nectar-collecting bees. Most effective pollination occurs between flowers of different style length, but fertilization by pollen from the same form occasionally occurs. In areas where water hyacinth has been introduced, pollinators are generally absent and some self-pollination may occur. In South-East Asia fruits are seldom produced if pollination is not carried out artificially. The fruits usually mature under water and in general a period of 20 days is necessary for the production of ripe seed. When the fruit bursts upon maturity, seeds will sink to the bottom of the water. The seed-coat acts as a physical barrier to germination. However, if the seed-coat is cracked, for example by alternate drying and wetting, germination may occur soon after shedding. On the other hand, there are reports of seeds remaining dormant for a period of about 20 years. Seedlings produce 2-3 ligulate leaves in 10 days and 7-8 ligulate plus 1-3 spatulate leaves in 30 days.

Ecology

Water hyacinth thrives in various fresh-water habitats, ranging from shallow ponds, marshes, and small streams to large lakes and rivers. However, strong wave movements will unfavourably affect its growth. When ponds or floodplains dry out, water hyacinth dies rapidly. It is heliophilous and grows best under high light intensity. The present geographic distribution ranges from the Equator to nearly 38°N and 38°S which demonstrates its tolerance of various temperature regimes. Air temperatures may be as low as 1 °C and as high as 40 °C. Leaves are killed by frost, but plants survive until the rhizomes are frozen. Water hyacinth occurs in water having a wide range of pH values, but dense vegetations are mainly found in water with a pH near 7. Although the chemical composition of the water may vary to a large extent, the salt tolerance of water hyacinth is relatively low.

Diseases and pests

In general, water hyacinth is very little affected by diseases and pests outside its natural habitat. However, fungi and arthropods that can be used as biological means of weed control have been identified. Of the few host-specific virulent pathogens, only the fungus Cercospora rodmanii, a native of Florida, has been found suitable for large-scale field application. Various arthropods have been collected in its original habitat in South America and the most promising agents for biological control are the curculionid weevils Neochetina eichhorniae and N. bruchi, and the stem-boring pyralid moth Sameodes albiguttalis. These insects have already been put to practical use and have become established in new habitats following their introduction. They cannot control water hyacinth by themselves, so additional control measures remain needed. Apart from the above-mentioned biological means of control, water hyacinth can be removed physically (manually or mechanically) or killed with herbicides. It should be taken into consideration that chemical control may bring about risks to the environment. The herbicide most commonly used against water hyacinth is 2,4-D (2-5 kg/ha).

Genetic resources and breeding

No substantial germplasm collections are known to be maintained.

Prospects

Water hyacinth is the subject of extensive research, which bodes well for the development of new applications. Its operational use in the treatment of waste water including sewage effluent, removing both dispersed particles and heavy metals is likely to develop further. Attempts are also being made to combine the water treatment potential of water hyacinth with biogas production. Its role as a green manure, mulch and fodder plant will remain important, mainly in conjunction with its control as a weed.

Literature

• Auld, B.A., 1994. Potential of mycoherbicides in Malaysia. In: Caunter, I.G. & Sastroutomo, S.S. (Editors): Appropriate weed control in Southeast Asia. Proceedings of an FAO-CAB International workshop, Kuala Lumpur, Malaysia, 17-18 May 1994. pp. 42-47.
• Gopal, B., 1987. Water hyacinth. Aquatic plant studies 1. Elsevier, Amsterdam, the Netherlands. 471 pp.
• Low, K.S., Lee, C.K. & Tan, K.K., 1995. Biosorption of basic dyes by water hyacinth roots. Bioresource-Technology 52: 79-83.
• Penfound, W.T. & Earle, T.T., 1948. The biology of the water hyacinth. Ecological Monographs 18: 447-472.
• Pieterse, A.H., 1978. The water hyacinth (Eichhornia crassipes) - a review. Abstracts on Tropical Agriculture 4(2): 9-42.
• Pieterse, A.H. & Murphy, K.J. (Editors), 1990. Aquatic weeds, the ecology and management of nuisance aquatic vegetation. Oxford University Press, Oxford, United Kingdom. 593 pp.
• Quinones, N.C. & Bravo, M.V., 1993. Rediscovering the uses of water hyacinth. Canopy International 18(5): 1, 3-4.
• van Thielen, R., Ajuonu, O., Schade, V., Neuenschwander, P., Adité, A. & Lomer, C.J., 1994. Importation, releases, and establishment of Neochetina spp. (Col.: Curculionidae) for the biological control of water hyacinth (Eichhornia crassipes Lil.: Pontederiaceae) in Benin, West Africa. Entomophaga 39: 179-188.
• Yeoh, B.G. & Odegaard, H., 1993. Use of water hyacinth (Eichhornia crassipes) in upgrading small agroindustrial wastewater treatment plants. Water Science and Technology 28: 207-213.

Authors

A.H. Pieterse