Hei-kak: An aquatic cash crop in Manipur

Dr N Irabanta Singh *

Hei-kak (in Manipuri)/ water chesnut or water caltrop (in English)/ Singhara (in Hindi) is botanically known as Trapa bisponasa Roxb. (Synonym. Trapa natans var. spinosa Roxb. makino) [Family Trapaceae].

Description: An aquatic floating herb with dimorphic submerged pinnately divided opposite leaves, petiole swollen and spongy at the top. Flowers white, tetramerous, fruit with 2 lateral sharp spines (D.B. Deb’s Collections No. 2495. Bull. Bot. Surr. India Vol I (3 & 4), PP 253-350,1961).

Ecology: The plant is grown in ponds, marshes, seasonal and perennial lakes like Loktak. More than two-third of the plant remains submerged in the water. The upper leaves float on the surface of the water while the lower ones remain submerged just beneath the surface, giving a mat like appearance to the water surface.

The petioles or leaf stalks are swollen and contain air to keep the upper leaves afloat. The plant has no primary roots, while the secondary adventitious roots are of two types, viz 1) the root fixes the plant to muddy substrate while 2) float free, being attached to the underside of the leaf base. These have photosynthetic activity as well.

The flowers open above the surface. After pollination they submerged themselves so that the fruit can develop. Therefore, the fruit of the Hei-kak is always found under the leaves and when it is matured, it drops off on its own and is fished out with the aid of net.

Cultivation and seed character: Hei-kak is cultivated in India, Pakistan, Bangladesh, Sri Lanka, Indonesia, Thailand, China, Taiwan and Australia. But in Loktak lake of Manipur, it grows wild. The plant requires full sunlight for good growth and water with a rich organic content (source may be phumdi) with low concentration of salts.

It has two short, thick, blunt projections of seed coat. Seed is triangular in shape. Seed coat of raw Hei-kak is difficult to remove with fingers. It can either be removed by slicing it into two pieces or by boiling the fruit which makes the seed coat soft enough to remove by hand. The seed coat colours the hand black, when one handles the fruit and available in green, red or blant of these two colours.

Nutrient values and nutritional benefits: 100 gm of fruit contain water (48.2gm), protein (3.4gm), fat (0.2gm), carbohydrate (32.1gm), sugar (3.3gm), energy (730 calories), dietary fibre (14.9gm), calcium (17.6mg), zinc (0.4mg), iron (0.7mg), sodium (0.8mg), potassium (468mg) [Source: lifestyle.iloveindia.com lounge].

Gluten free, low in fat, cholesterol free, low in sodium, high in potassium, rich in minerals like calcium, iron, zinc and phosphorous, contains moderate amount of fibre and good source of energy.

Health benefit: Hei-kak is very nutritive and offers numerous health benefits. It is used in Ayurveda to cure various diseases. It is known as charak which is given for infertility, impotency, painful urination, excessive urination, cough and as a tonic to cure weakness and fatigue.

As it is cooling effect, it helps in bleeding disorders, hemorrhages and abdominal bleeding from uterus. Hei-kak is very beneficial for women due to its nutritive, strengthening and cooling properties, it increases fertility and chances of conception. It also helps to stabilize pregnancy and prevent abortion.

It is also used for treating diarrhea, dysentery, thyroid problem and bronchitis. It is a natural anti-oxidant, prevents wrinkles and protect from ultra-violet rays.

Economics of Hei-kak: The harvesting season of hei-kak (seed of Trapa bispinosa) starts from early July and ends in mid-October. It is widely available in Loktak lake (Manipur) and doesn’t require any maintenance. Hence the cost of cultivation is basically nil.

Generally, seasonal labourers would harvest the Hei-kak from Loktak Lake with the help of net and brings to the nearby Moirang Bazaar. His labour charge is Rs.200 per cement bag (weigh nearly 20kg). The wholesaler imas (mother) sell it to the retailer ima at Kwairamband Bazaar @ Rs. 80/kg for raw and Rs. 100/kg for boiled.

These retailer imas sell Rs.100/kg for raw and Rs.120/kg for boiled. Whereas during September, October months the rate decreases due to its pletiness. The wholesaler imas sell to the retailer imas @Rs.30/kg for raw and Rs.50/kg for boiled. The retailers sell to the consumers @Rs.50/kg for raw and Rs.70/kg for boiled.

Conclusion and recommendations: Consumption of hei-kak is useful for infertility, impotency, painful urination, excessive urination, cough and as a tonic to cure weakness and fatigue.

One may eat 20-50 gm per day depending on digestive strength of the person to get its health benefits. Excess eating of hei-kak may cause stomach pain. Those who are suffering from constipation should not eat hei-kak. Regular eating of hei-kak increases body weight and should avoid drinking water after eating hei-kak.