Monochoria vaginalis (Burm. f.) C. Presl - PONTEDERIACEAE - Monocotyledon

Common name : Monochoria
Common name in Bengali : Panee kachu
Common name in Hindi : Panpatta, meerthomari

Habit - © Juliana PROSPERI - Cirad Apex leaf acuminate and the base heart-shaped - © Juliana PROSPERI - Cirad Violet to lilac blue flowers - © Juliana PROSPERI - Cirad Inflorescence arising from a thickened bundle of leaves stalk - © Juliana PROSPERI - Cirad Young flower - © Juliana PROSPERI - Cirad Detail of the inflorescence - © Juliana PROSPERI - Cirad Roots - © Juliana PROSPERI - Cirad

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Diagnostic characters Biology Ecology and distribution Nuisance Weed control Botany Uses/Remark References

Diagnostic characters :

Monochoria refers to the one separate stamen in plants of this genus. M. vaginalis is a semi-aquatic (the plant roots in mud and its upper portions grow above water), annual or perennial herb of 10 to 50cm tall. It is fleshy and glabrous and has a shiny appearance. The leaves with long petiole radiate from a short rhizome; they are very variable in shape, being lanceolate to cordate or sagittate. The inflorescence, opposite the floral leaf, has a long stalk of about 30cm, with violet to lilac blue flowers. After flowering, the inflorescences bend downward to become capsules that will mature below the water surface. Old plants often form large clumps.

Biology :

Little is known of the biology of M. vaginalis. The most helpful work on its biology was done in Japan by Noda and Eguchi (1965). They studied seedling emergence in early, ordinary and late plantings of rice; they also studied the seasonal variations in germination and the effects of soil moisture. The greatest number of seedling emerged in the early planted fields. 35 percent more seedlings emerged from the saturated soil than they did from submerged or dry soil in the early planting. A striking change in germination pattern was shown under submerged conditions. The majority of the seedlings emerged in a very short time, the peak being between 15 and 25 days; whereas in saturated or dried soil there was a tendency toward gradual emergence through the season. Other studies suggested that submergence of the fruits after pollination was benefical for seed development.

Ecology and distribution :

M. vaginalis is native to tropical Asia and Africa, where it is not a weed. It is clearly very serious weed in Southeast Asia, where it is widely distributed from the tropical to temperate regions. It occurs in Korea and Japan, reaches downward through the Pacific Islands, to the mainland of Southeast Asia, and across to India.
It occurs in marshy places, fresh water pools, mudflats, ditches along canal banks and in rice fields. It is predominentaly an annual in flooded ricefields, dying when the fields dry out, and developing again later from seeds.

Nuisance :

It is a very serious weed in the rice fields of eastern and southeastern Asia. In India it is considered a common weed in rice cultures. M. vaginalis does not compete seriously for light and that, because it is shallow rooted, the deeper rooted rice plants may be able to compete more vigorously for nutrients.

Weed control :

- Biological
Little is recorded about the natural enemies of M. vaginalis; referring to insects, in India are present Gesonula punctifrons (Orthoptera family); Spodoptera litura, Nymphula fregonalis and Hippotion echeclus (Lepidoptera family) all polyphagous.
- Chemical
Post-emergence application of 2_4-D at 500 g.i/ha or Allmix g/ha.
Following the studies brought in Japan, it seems that a single herbicide treatement early in the season would be futile. The majority of the weeds might germinate after the herbicide had broken down, permitting a heavy seeding for the next crop.

Botany :

Smooth tufted aquatic herb with a very short rhizome; its size vary from 10 to 50cm tall. Annual or pseudoannual in flooded ricefields, but may grow as perennial in constantly flooded areas. Old plants often forming large clumps, but this are not connected.
Fibrous roots at the base of petioles.
Very short rhizome unbranched.
The leaves have variable size, 2 to 12.5cm long, and 0.5 to 10cm wide. In very young plants without lamina; leaves somewhat older plants with a floating linear, or lanceolate blade; leaves of still older plants, ovate-oblong to broadly ovate, sharply acuminate, the base heart-shaped or rounded, shiny, deep green in color, with longitudinal veins; petioles soft, hollow, growing from buds at the base. Leaf sheaths twisted together at the base, slightly reddish when young; crown appears bulbous.
Spikelike, basally opposite the sheath of the floral, with a large bract arising from a thickened bundle of leaves stalk, about two-thirds of the way up the stalk from the base; flowers 3 to 25, opening simultaneously or in quick succession; on pedicels 4 to 25mm long; perianth 11 to 15mm long; petals six, violet or lilac blue, spreading at flowering, afterwards spirally contorted; stamens six, one with a lateral obliquely erect tooth; ovary with a long stile. After flowering, the inflorescences bend downward.
Capsule of about 1cm diameter, splitting between the partitions into three valves. The fruit may mature below the water surface.
Numerous seeds longitudinally ribbed.
The seedlings are easily distinguished by their purple roots.

Uses/Remark :

M. vaginalis and M. hastata (L.) Solms, are similar in appearance and often mistaken for one another, but they can be distinguished. M. hastata is larger, also it has a well developed, branched rhizome which form a network of plants, whereas M. vaginalis has a short rhizome. M. hastata has predominantly sagittate or hastate leaves; M. vaginalis has leaves which are usually heart-shaped. M. hastata has more flowers in the raceme. Flowers in M. vaginalis are less per spike, more colored than those of M. hastata. The flowers also open nearly simultaneously, those of M. hastata do not. The lower pedicels of flowers on M. hastata are elongated, whereas all pedicels in M. vaginalis are less than 1cm long. Finally M. hastata is not as common as M. vaginalis.
The leaves of both species are eaten as food. M. vaginalis is used in traditional medicine against cough.

References :

- Holm L. G., Plucknett D. L., Pancho J. V., Herberger J. P. 1991. The world’s worst weeds. Distribution and Biology. East-West Center by the University Press. Hawaii.
-Harada J. and Association for international cooperation of agriculture & forestry. 1996. Weeds in the tropics. Association for international cooperation of agriculture & forestry, Japan. 304p.
- Waterhouse D. F. 1994. Biological control of weeds: Southeast Asian prospects. ACIAR Monograph No. 26, 302pp.

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