Nelumbo nucifera
Nelumbo nucifera, also known as Indian lotus, sacred lotus, bean of India, Egyptian bean or simply lotus, is one of two extant species of aquatic plant in the family Nelumbonaceae. It is often colloquially called a water lily.
Lotus plants are adapted to grow in the flood plains of slow-moving rivers and delta areas. Stands of lotus drop hundreds of thousands of seeds every year to the bottom of the pond. While some sprout immediately, and most are eaten by wildlife, the remaining seeds can remain dormant for an extensive period of time as the pond silts in and dries out. During flood conditions, sediments containing these seeds are broken open, and the dormant seeds rehydrate and begin a new lotus colony. Under favorable circumstances the seeds of this aquatic perennial may remain viable for many years, with the oldest recorded lotus germination being from seeds 1,300 years old recovered from a dry lakebed in northeastern China.
It has a very wide native distribution, ranging from central and northern India, through northern Indochina and East Asia, with isolated locations at the Caspian Sea. Today the species also occurs in southern India, Sri Lanka, virtually all of Southeast Asia, New Guinea and northern and eastern Australia, but this is probably the result of human translocations. It has a very long history of being cultivated for its edible seeds, and it is commonly cultivated in water gardens. It is the national flower of India and Vietnam.
Classification
The lotus is often confused with the true water lilies of genus Nymphaea, in particular N. caerulea, the "blue lotus". In fact, several older systems, such as the Bentham & Hooker system refer to the lotus by its old synonym of Nymphaea nelumbo.While all modern plant taxonomy systems agree that this species belongs in the genus Nelumbo, the systems disagree as to which family Nelumbo should be placed in, or whether the genus should belong in its own unique family and order. According to the APG IV system, N. nucifera, N. lutea, and their extinct relatives belong in Proteales with the protea flowers due to genetic comparisons. Older systems, such as the Cronquist system, place N. nucifera and its relatives in the order Nymphaeles based on anatomical similarities.
Botany
The roots of lotus are planted in the soil of the pond or river bottom, while the leaves float on the water's surface or are held well above it. The flowers are usually found on thick stems rising several centimeters above the leaves. The leaf stalks can be up to long, allowing the plant to grow in water to that depth, and a horizontal spread of. The leaves may be as large as in diameter, while the showy flowers can be up to in diameter.Researchers report that the lotus has the remarkable ability to regulate the temperature of its flowers to within a narrow range just as humans and other warmblooded animals do. Roger S. Seymour and Paul Schultze-Motel, physiologists at the University of Adelaide in Australia, found that lotus flowers blooming in the Adelaide Botanic Gardens maintained a temperature of, even when the air temperature dropped to. They suspect the flowers may be doing this to attract coldblooded insect pollinators. Studies published in the journals Nature and Philosophical Transactions: Biological Sciences were in 1996 and 1998 important contributions in the field of thermoregulation, heat-producing, in plants. Two other species known to be able to regulate their temperature include Symplocarpus foetidus and Philodendron selloum.
An individual lotus can live for over a thousand years and has the rare ability to revive into activity after stasis. In 1994, a seed from a sacred lotus, dated at roughly 1,300 years old ± 270 years, was successfully germinated.
The traditional Sacred Lotus is only distantly related to Nymphaea caerulea, but possesses similar chemistry. Both Nymphaea caerulea and Nelumbo nucifera contain the alkaloids nuciferine and aporphine.
The genome of the sacred lotus was sequenced in May 2013.
Cultivation
The Sacred Lotus grows in water up to. The minimum water depth should not be less than. In colder climates such a low water level, which heats up more quickly, is helpful for better growth and flowering. Lotus germinates at temperatures above. Most varieties are not cold-hardy. In the growing season from April to September, the average daytime temperature needed is. In regions with low light levels in winter, the sacred lotus has a period of dormancy. The tubers are not cold resistant, but can resist temperatures below if they are covered with an insulating cover of water or soil. During winter time, the roots have to be stored at a frost free place.Planting
The sacred lotus requires a nutrient-rich loamy soil. In the beginning of the summer period, a small part of rhizome with at least one eye is either planted in ponds or directly into a flooded field. There are several other propagation ways via seeds or buds. Furthermore, tissue culture is a promising propagation method for the future to produce high volumes of uniform, true-to-type, disease free materials.First step of the cultivation is to plough the dry field. One round of manure is applied after ten days, before flooding the field. To support a quick initial growth, the water level is held relatively low and is increased when plants grow. Then a maximum of approximately 4000 rhizome pieces per hectare are used to plant directly into the mud below the soil surface.
Harvest
The stolon is ready to harvest two to three months after planting. It must be harvested before the flowering. Harvesting the stolon is done by manual labour, too. For this step, the field is not drained. By pulling and shaking the young leaves in the shallow water, the stolon is pulled out of the water.Three months after planting, the first leaves and flowers can be harvested. Flowers can be picked every two days during summer and every three days during the colder season. Four months after planting, the production of flowers has its climax. The harvest of flowers is usually done by hand during three to four months.
Seeds and seed pods can be harvested when they turn black four to eight months after planting. After sun drying for two to three days, they are processed by mechanical tools to separate seed coats and embryos.
The rhizomes mature to a suitable stage for eating in approximately six to nine months. Early varieties are harvested in July until September and late varieties from October until March, after the ponds or fields are drained. The large, starch rich rhizomes are easy to dig out of the drained soil. In small scale production, they are harvested by hand using fork like tools. In Japan and on bigger farms the manual labour harvesting is fully replaced by machines.
Varieties and cultivars
Lotus varieties have been classified according to their use into three types: rhizome lotus, seed lotus and flower lotus. Varieties that show more than one of these characteristics are classified by the strongest feature. Regarding production area in China, rhizome lotus has the largest area with, followed by seed lotus with.Rhizome lotus
Rhizome lotus cultivars produce a higher yield of and higher quality rhizomes than that of seed or flower lotus cultivars. Furthermore, this group grows the tallest and produces very few to no flowers.Cultivars can be classified by harvest time or by the depth of rhizomes into these types:
- Pre-mature cultivars are harvested before the end of July, serotinous cultivars from September on and mid-serotinous or mid-matutinal cultivars are in between these harvest times. Using pre-mature cultivars, rhizomes can be harvested earlier and therefore be sold for a higher price.
- Ad littoral, deep, and intermediate cultivars are distinguished according to the depth in which the rhizomes grow underground. Adlittoral cultivars range from depth and are often pre-mature. They develop faster due to higher temperature in surface soil layers. When harvested in July, adlittorals have higher yields than deeper growing cultivars, but not necessarily when harvested in September. Rhizomes of adlittoral cultivars are crisp and good for frying purposes. Deep cultivars grow more than deep. They are often serotinous and can harvest high yield. Their rhizomes are starch-rich.
Seed lotus
The characteristics of seed lotus cultivars are a large number of carpels and seed sets as well as large seeds with better nutritional properties. Roots of these varieties are thin, fibrous and do not form good rhizomes. The main popular cultivars for seed production in China are Cunsanlian, Xianglian 1, Zilian 2, Jianlian, Ganlian 62 and Taikong 36. Average yield of these cultivars in China is 1.05–1.9 t/ha of dry seeds and weight of thousand seeds between. Green Jade and Vietnam-Red are recommended cultivars for seed production in Australia.Flower lotus
Flower lotus cultivars are used exclusively for ornamental purpose, produce a large number of flowers and the lowest plant height.Seed production of flower lotus is poor regarding yield and quality. Flower types differ in the number of petals and their colours range from single colour in white, yellow, pink, red to bi-colour, most often of white petals with pink tip or highlights.
Farming
About 70% of lotus for the human consumption is produced in China. In 2005, the cultivation area in China was estimated at. A majority of lotus production takes place in managed farming systems in ponds or flooded fields like rice.The most widely used system is crop rotation with rice and vegetables. This system is applicable if the propagule can be planted early in the year. The rhizomes are harvested in July, after which rice can be planted into the same field. Rice is then harvested in October. From November until March, the field stays either free, or a vegetable, such as cabbage or spinach, is planted. Alternatively, the vegetable can also be planted after the harvest of lotus.
Another alternative way is to not harvest the lotus rhizome, although it is ripe. A terricolous vegetable is planted between the rhizomes into the drained field. The rhizomes are then harvested next March.
A third way is to plant lotus in ponds or fields and raise aquatic animals such as fish, shrimp or crab in the same field. A more efficient use of the water for both, the aquatic animal and the lotus production, has been identified with this planting pattern.
Use
Human consumption
Rhizomes
The rhizomes of lotus are consumed as a vegetable in Asian countries, extensively in China and Japan: sold whole or in cut pieces, fresh, frozen, or canned. They are fried or cooked mostly in soups, soaked in syrup or pickled in vinegar. Lotus rhizomes have a crunchy texture with sweet-tangy flavours and are a classic dish at many banquets where they are deep-fried, stir-fried, or stuffed with meats or preserved fruits. Salads with prawns, sesame oil or coriander leaves are also popular. Unfortunately, fresh lotus root slices are limited by a fast browning rate. Lotus root tea is consumed in Korea.Lotus root is utilized as a popular vegetable in Sri Lanka, where it is often cooked in coconut milk gravy.
Japan is one of the primary users of the rhizomes, representing about 1% of all vegetables consumed. Japan grows its own lotus but still must import 18,000 tons of lotus rhizome each year, of which China provides 15,000 tons yearly.
Rhizomes contain high amounts of starch without characteristic taste or odor. The texture is comparable to a raw potato. The binding and disintegration properties of isolated Nelumbo starch have been compared with maize and potato starch; Nelumbo starch is shown to be superior as an adjuvant in the preparation of tablets. When dried, N. nucifera is also made into flour, another popular use of this vegetable.
Pips
is consumed in Korea.Seeds
Fresh lotus seeds are nutritious but also vulnerable to microbial contamination, especially fungal infections. Therefore, mostly dry lotus seed-based products are found on the market. Traditional sun baking combining with charcoal processing dries the seeds but results in loss of nutrients. Freeze-dried lotus seeds have a longer shelf life and maintain original nutrients , while no differences in flavour are found after rehydration compared to fresh lotus seeds.Dry stored lotus seeds are sensitive to moisture and mold infestation; researchers continue to explore new ways to preserve fresh lotus seeds for example radiation processing.
Lotus seeds can be processed into moon cake, lotus seed noodles and food in forms of paste, fermented milk, rice wine, ice cream, popcorn and others, with lotus seeds as the main raw material. Traditional Eastern medicine claims that fresh lotus seed wine has thirst quenching, spleen healing and anti-diarrheal advantages after drinking, attributed to unspecified bioactive compounds. Lotus seed tea is consumed in Korea, and lotus embryo tea is consumed in China and Vietnam.
Stems
Young lotus stems are used as a salad ingredient in Vietnamese cuisine.In north and eastern regions of India, the stalk of the flower is used to prepare a soup called "Kamal gatte ki Sabji" and starter called "kamal kakdi pakode".In South Indian states, the lotus stem is sliced, marinated with salt to dry, and the dried slices are fried and used as a side dish. In Kerala and Tamil Nadu, this end product is called " Thamara Vathal".
Leaves
In China and Korea, lotus leaf tea is made from the leaves of the lotus. It is also used as a wrap for steaming rice and sticky rice and other steamed dishes in Southeast Asian cuisine, such as lo mai gai in Chinese cuisine or kao hor bai bua, fried rice wrapped in lotus leaf in Thai cuisine.Flowers
In Korea, lotus flower tea is made from the dried petals of the white lotus.The stamens can be dried and made into a fragrant herbal tea, or used to impart a scent to tea leaves. This Vietnamese lotus tea is called trà sen, chè sen, or chè ướp sen.
Risks
The petals, leaves and rhizome can also all be eaten raw, but there is a risk of parasite transmission : it is therefore recommended that they be cooked before eating.Use in water treatment
Nelumbo nucifera shows high potential for usage in wastewater treatment removing polluting compounds and heavy metals. It is able to grow in variable water conditions and in low light intensity. Various studies show the successful use of N. nucifera to counteract water eutrophication. The leaves of the floating lotus reduce sunlight reaching the lower part of the water. This suppresses algae growth in N. nucifera aquatic systems and thus, the oxygen content is up to 20% higher than in other aquatic plant systems. Due to intense agricultural practices, nitrogen and phosphorus pollution are major problems in aquatic systems. N. nucifera is able to assimilate a higher content of phosphorus than aquatic plants currently used for water remediation. It also assimilates nitrogen and creates a habitat for bacterial growth in the water body. Through rhizofiltration, heavy metals – including arsenic, copper and cadmium – can be removed efficiently from the water. The results observed are impressive showing 96% of copper and 85% cadmium metals removed after a seven-day incubation period. The accumulation of heavy metals doesn't show morphological symptoms of metal toxicity; however, the rhizome quality for human consumption needs further study.Storage and commercialization
Currently most rhizomes are consumed fresh and it is not common to store them due to their poor shelf life performance. This limits export possibilities for low-income production countries in Asia. Rhizomes quickly lose water, oxidation occurs and nutrient composition changes within a short time after harvest. Optimal storage temperatures range between. There are three different approaches to storing rhizomes. By stacking the rhizomes, they are storable and remain fresh for about three weeks. Special stacking with silver sand and soil results in five to six layers that prevent water loss, thus the rhizome stays fresh for up to two months. However the method is not suitable for commercialization but rather for home use. Hydrogen sulfide fumigation reduces enzymatic browning and therefore ensures rhizome quality. Dipping the rhizomes in a salt solution prevents oxidation and bacterial reproduction, which allows storage for up to five months and a greater export ability. This treatment is related to high cost and inefficient cleaning process before eating the rhizomes.Use in bioengineering
Nelumbo nucifera contains some thermal-stable proteins that might be useful in protein bio engineering processes. The proteins are characterized by seed longevity used for cell protection and repair under stress. There are also several indications that compounds of N. nucifera are used in drug fabrication in human health research for multiple purposes.Other uses
The distinctive dried seed heads, which resemble the spouts of watering cans, are widely sold throughout the world for decorative purposes and for dried flower arranging.In Asia, the petals are sometimes used for garnish, while the large leaves are used as a wrap for food, not frequently eaten.
A unique fabric from the lotus plant fibers is produced only at Inle lake, Myanmar and in Siem Reap, Cambodia. This thread is used for weaving special robes for Buddha images called kya thingahn.
Chemical composition
The flavonol miquelianin, as well as the alkaloids --coclaurine and --norcoclaurine, can be found in the leaves of N. nucifera. The plant also contains nuciferine, neferine and many other benzylisoquinoline alkaloids with medicinal properties.Health properties and nutrients
Traditional medicine
All parts of Nelumbo nucifera are edible, with the rhizome and seeds being the main consumption parts. Traditionally rhizomes, leaves, and seeds have been used as folk medicines, Ayurveda, Chinese traditional medicine, and oriental medicine. While leaves are used for hematemesis, epistaxis, and hematuria, the flowers are used for lowering blood sugar levels, diarrhea, cholera, fever, and hyperdipsia. Rhizomes are promoted have purported diuretic, antidiabetic, and anti-inflammatory properties. In Chinese medicine, seeds are still used as Lian Zi Xi.Lotus rhizomes and seeds and their processing by-products are widely consumed in Asia, Americas, and Oceania for high content of physiologically active substances. Especially in China, lotus seeds are popular with a cultural history going back about 3000 years. As early as the Han Dynasty, lotus seeds were already recorded as sweet, astringent, nourishing the heart and kidney in "Shen Nong's Herbal Classic". Nowadays there are 22 varieties for the four known Chinese lines, which are found particularly in Jianning and Guangchang.
These days the perennial aquatic herb is gaining popularity because of its nutraceutical and historical importance It will be of economic value if the different parts of lotus can be developed as functional food. Because of the special role in human health and richness in nutrients and bioactive substances, the Chinese Ministry of Health approved the use of N. nucifera as both "food and medicine".
Rhizomes
The rhizomes are long, in diameter, yellowish white to yellowish brown, smooth and with nodes and internodes.The lotus root is used to add seasoning to food. Lotus root is a moderate calorie root vegetable and is composed of several vitamins, minerals, and nutrients: 83.80% water, 0.11% fat, 1.56% reducing sugar, 0.41% sucrose, 2.70% crude protein, 9.25% starch, 0.80% fiber, 0.10% ash and 0.06% calcium. 100 g of root provides 44 mg of vitamin C or 73% of daily recommended values.
Lotus rhizome and its extracts have shown diuretic, psychopharmacological, anti-diabetic, anti-obesity, hypoglycemic, antipyretic and antioxidant activities.
Seeds
Lotus seeds are mostly oval or spherical, with sizes varying according to varieties. They are generally 1.2–1.8 cm long, with diameter ranging from 0.8 to 1.4 cm and a weight of 1.1–1.4 g. After lotus seeds have been decorticated and peeled, they are edible and rich in nutrients, and can be dried for storage. Their nutritional values can differ due to culture environments and varieties.Not only do these seeds contain proteins of high quality and are rich in variety of essential amino acids including high contents of albumin and globulin, they also contain unsaturated fatty acids, carbohydrates, vitamins, calcium, iron, zinc, phosphorus and other trace elements. They also provide water-soluble polysaccharides, alkaloids, flavonoids, superoxide dismutase and other bioactive components.
Lotus seed also contain particularly large amounts of vitamins, including VB1, VB2, VB6 and Vitamin E.
The functional components in N. nucifera seeds can help combatting high blood pressure, diabetes and gallstones. Lotus seed's water-soluble polysaccharides have also been shown to promote lymphocyte transformation and enhance the immune function.
After lotus seed germination, crude protein and fat levels in the endosperm significantly increase. It is therefore an important method to enhance its nutritional quality.