Water Mimosa (Ekaithabi) : An underutilised aquatic vegetable

Yengkokpam Ranjana Devi *

Neptunia oleracea Lour. locally known in Manipur as Eshing Ekaithabi and commonly known as Water Sensitive Plant or Water Mimosa, is a wild floating aquatic legume native to several continents of the humid tropics of both hemispheres, particularly in Asia, Africa and South America. It is cultivated as vegetable throughout Southeast Asia, particularly in Indo-China region and Thailand.

Habitat

Neptunia oleracea Lour. grows on the banks or margins of water bodies and then spreads out over the water surface. It prefers lakes, farm dams, ponds and swamps but also grows along slow-moving water ways. The north eastern region of India provides favourable condition for growth and propagation of the plant owing to its ample rainfall, humidity and moderate range of temperature.

EshingEkaiThabi is found cultivated in the ponds and wetlands in valley areas of Imphal, Manipur. It is sold in the markets during its season (June-August) in bundles of 4-5 plants of about 10-15 inches length and costs around 20-30 rupees each.

Morphology

The stems are terete, rarely branched and detached from the primary root system. It forms white spongy fibrous swollen internodes and produce clustered brown fibrous adventitious roots at the nodes when growing in water. The white spongy tissue helps the plant to float in the water. The leaves are bi-pinnate with 2-4 pairs of pinnae with hairless leaflets. The leaves are sensitive to touch and fluctuations in light.

Flowers are bright yellow in colour and have very long peduncles in sub spherical axillary heads. The pods are shortly oblong in umbel like cluster, green in colour. It has an unusual smell that can be used in the identification of the plant. It can be grown via seeds or can be propagated through cuttings. The plant is found abundantly during the rainy season. When the water level falls during the dry season, the plants often perish.

Nutritional Properties

Water Mimosa has been consumed by people from Malaysia, Thailand and Cambodia due to its nutritional values. Meitei, the valley inhabitants of the state of Manipur have the tradition of eating the raw plants of water mimosa, the knowledge of which is handed over from generation to generation through the belief that they get direct nutritional and medicinal benefit by this mode of eating.

The edible portion of the shoot is found to contain (per 100 g): moisture- 89.4%; protein6.4 g; fat- 0.4 g; carbohydrate- 0.8 g; fibre- 1.8 g; ash- 1.2 g; Ca- 887 mg; P-7 mg; Fe- 5.3 mg; Vitamin A-5155 IU; vitamin B1 - 0.12 mg; vitamin B2 - 0.14 mg, niacin- 8.2 mg; vitamin C- 1.8 mg and the energy value of the plant is 184 kJ 100 g-1.

Several authors have reported the presence of Na, K, Ca, Mg, K, Mn, Cu, Zn, Fe, P, Pd and Ni in varying concentrations. A recent study also found that Neptunia oleracea has high in-vitro total antioxidant capacity (TAC) and the content was found to highest in stems (IC50 µg ml-1: 428 ± 5.79) and leaves (IC50 µg ml-1: 403 ± 2.25).

Medicinal Properties

There are different modes of use of Water Mimosa. It is eaten as a vegetable or used for its medicinal properties. The young leaves, shoot tips, ends of stem and young pods are usually eaten raw or in stir-fries. For medicinal benefits, the plant is either consumed fresh or as decoction or for local application and is mainly used for treatment of:

1. Nose bleeding: The pounded leaves and stem of the plant is applied over the nose to treat syphilitic ulcers/necrosis of the nose and hard palate.

2. Dysentery and intestinal infection: The leaf of the plant is eaten raw to treat dysentery and intestinal infection. Alternatively, decoction is prepared by crushing the leaves of the plant with water and given to the person twice a day (morning and evening) until cured.

3. Anthelminthic: Decoction is prepared by crushing the leaves of the plant with water and given to the person twice a day (morning and evening) for three days to treat parasitic worm infections. The decoction is used for treatment of yellow fever and Guinea worm infection in Nigeria.

4. Fever: The plant is also used for treatment of fever by applying the infusion of the whole plant on the body of the patient.

5. Earache: The juice of the stem and leaf is squeezed into the ear to cure earache

6. Reports on use of Neptunia oleracea for treatment of sores on tongue, white discharge and epilepsy has also been documented.

Other Uses

1. As a green manure: The mimosoid legume genus Neptunia has attracted much interest in the last 15 years, largely because of the aquatic habit of some of its species and the ability of some of these to form N2 fixing root nodules on submerged roots.

The use of nodulated wetlands legumes as green manures in the cultivation of lowland rice due to their high ratio of N2 fixation under flooded conditions has been reported so it is cultivated in Asian countries for green manures for rice cultivation.

2. Phytoremediation: Neptunia oleracea has been extensively used as water treatment agent in Asian countries like Thailand, Vietnam, Philippines, Indonesia and Malaysia. The most common contaminant which can be treated by Water Mimosa is heavy metals such as Cd, Cu, Zn and Mn.

The plant is being used as phytoremediation to treat waste and polluted water. It has been established that this phytoremediation method is the most environment friendly method to treat water in addition to it being a low-cost technology.

Disadvantages

However, certain disadvantages are also associated with the plant as this nitrogen-fixing legume releases nitrogen into water bodies leading to increased algal blooms and encourage growth of other weeds such as water hyacinth, water lettuce and salvinia. Excess nitrogen affects water quality and increases water- treatment costs, hence, it is declared as a restricted invasive plant under the Biosecurity Act 2014 in the State of Queensland, Australia.

If Water Mimosa is used for phytoremediation as pollutant cleanup method and remedy, the plant might be unsafe for human consumption and may pose health risk.

Conclusion

Based on the documented multipurpose use of the plant, it can be concluded that Water Mimosa / EshingEkaiThabi is an underutilized aquatic vegetable which is embedded with rich nutrient potentials along with ability to stand against adverse climatic conditions. Due to its high nutritional and medicinal properties, the plant plays an important role against malnutrition in the weaker section of the society.

Due to favourable climatic condition for growth, the large areas of unused wetland in North East of India may be cultivated with the plant which in turn will help generate sustainable income.

The possible reasons for the low utilization of the vegetable in spite of their recognized importance may be the lack of information about their performance, hence, an awareness needs to be created so that the cultivation of the plant may prove to be a boon to all concerned i.e., the growers, consumers and environmentalists, provided that they are tamed properly.

For further details contact :
Public Relations & Media Management Cell,
CAU, Imphal.
Email: [email protected]