Deepwater rice are varieties of

rice Rice is the seed of the grass species '' Oryza sativa'' (Asian rice) or less commonly ''Oryza glaberrima'' (African rice). The name wild rice is usually used for species of the genera '' Zizania'' and '' Porteresia'', both wild and domesticat ...

(''

Oryza sativa ''Oryza sativa'', commonly known as Asian rice or indica rice, is the plant species most commonly referred to in English as ''rice''. It is the type of farmed rice whose cultivars are most common globally, and was first domesticated in the Yan ...

'') grown in flooded conditions with water more than deep for at least a month.Catling, p. 2. More than people in Southeast Asia including Northeastern India rely on deepwater rice for their sustenance. Two adaptations permit the rice to thrive in deeper water, floating rice and traditional talls. Traditional talls are varieties that are grown at water depths between and have developed to be taller and have longer leaves than standard rice. Floating rice grows in water deeper than 100 cm through advanced elongation ability. This means when a field where rice is growing floods, accelerated growth in the internodal of the stem allows the plant to keep some of its foliage on top of the water. The ''O. s. indica''

cultivar A cultivar is a type of cultivated plant that people have selected for desired traits and when propagated retain those traits. Methods used to propagate cultivars include: division, root and stem cuttings, offsets, grafting, tissue culture ...

is the main type of deepwater rice, although varieties of ''O. s. japonica'' have been found in

Burma Myanmar, ; UK pronunciations: US pronunciations incl. . Note: Wikipedia's IPA conventions require indicating /r/ even in British English although only some British English speakers pronounce r at the end of syllables. As John Wells explai ...

and Assam Plains.Catling, p. 110.

Production

Deepwater rice is a staple food grown on roughly of land. The main areas where it is grown are in

Southeast Asia Southeast Asia, also spelled South East Asia and South-East Asia, and also known as Southeastern Asia, South-eastern Asia or SEA, is the geographical south-eastern region of Asia, consisting of the regions that are situated south of mainlan ...

including Northeastern India, where more than people rely on its production for their livelihood. In South-East Asia, the main area deepwater rice is grown in the

Brahmaputra The Brahmaputra is a trans-boundary river which flows through Tibet, northeast India, and Bangladesh. It is also known as the Yarlung Tsangpo in Tibetan, the Siang/Dihang River in Arunachali, Luit in Assamese, and Jamuna River in Bangla. I ...

valley in

Assam Assam (; ) is a state in northeastern India, south of the eastern Himalayas along the Brahmaputra and Barak River valleys. Assam covers an area of . The state is bordered by Bhutan and Arunachal Pradesh to the north; Nagaland and Manipur ...

, a state in Northeast India and other Northeast Indian states. In other regions of Mainland Southeast Asia, the main areas of cultivation are in Burma in the

Irrawaddy Delta The Irrawaddy Delta or Ayeyarwady Delta lies in the Irrawaddy Division, the lowest expanse of land in Myanmar that fans out from the limit of tidal influence at Myan Aung to the Bay of Bengal and Andaman Sea, to the south at the mouth of the ...

, in

Thailand Thailand ( ), historically known as Siam () and officially the Kingdom of Thailand, is a country in Southeast Asia, located at the centre of the Indochinese Peninsula, spanning , with a population of almost 70 million. The country is b ...

in the

Chao Phraya The Chao Phraya ( or ; th, แม่น้ำเจ้าพระยา, , or ) is the major river in Thailand, with its low alluvial plain forming the centre of the country. It flows through Bangkok and then into the Gulf of Thailand. E ...

and

Mekong The Mekong or Mekong River is a trans-boundary river in East Asia and Southeast Asia. It is the world's twelfth longest river and the third longest in Asia. Its estimated length is , and it drains an area of , discharging of water annual ...

Vietnam Vietnam or Viet Nam ( vi, Việt Nam, ), officially the Socialist Republic of Vietnam,., group="n" is a country in Southeast Asia, at the eastern edge of mainland Southeast Asia, with an area of and population of 96 million, making i ...

and

Cambodia Cambodia (; also Kampuchea ; km, កម្ពុជា, UNGEGN: ), officially the Kingdom of Cambodia, is a country located in the southern portion of the Indochinese Peninsula in Southeast Asia, spanning an area of , bordered by Thailan ...

.Catling, p. 7. In these countries, deepwater rice accounts for more than 25% of the land used to grow rice. Deepwater rice is cultivated less in West Africa than in Asia, with about . Areas it is grown include the

Niger River The Niger River ( ; ) is the main river of West Africa, extending about . Its drainage basin is in area. Its source is in the Guinea Highlands in south-eastern Guinea near the Sierra Leone border. It runs in a crescent shape through ...

basin. Some areas in

Ecuador Ecuador ( ; ; Quechua: ''Ikwayur''; Shuar: ''Ecuador'' or ''Ekuatur''), officially the Republic of Ecuador ( es, República del Ecuador, which literally translates as "Republic of the Equator"; Quechua: ''Ikwadur Ripuwlika''; Shuar: ' ...

grow deepwater rice.De Datta, p. 244.

Cultivation methods

Deepwater rice is grown in

tropical monsoon climate An area of tropical monsoon climate (occasionally known as a sub-equatorial, tropical wet climate or a tropical monsoon and trade-wind littoral climate) is a tropical climate sub-type that corresponds to the Köppen climate classification category ...

s normally around

river delta A river delta is a landform shaped like a triangle, created by deposition of sediment that is carried by a river and enters slower-moving or stagnant water. This occurs where a river enters an ocean, sea, estuary, lake, reservoir, or (more ra ...

s and their

floodplain A floodplain or flood plain or bottomlands is an area of land adjacent to a river which stretches from the banks of its channel to the base of the enclosing valley walls, and which experiences flooding during periods of high discharge.Goudi ...

s mainly in

backswamp In geology, a backswamp is a type of depositional environment commonly found in a floodplain. It is where deposits of fine silts and clays settle after a flood A flood is an overflow of water ( or rarely other fluids) that submerges land tha ...

s and natural levees. The nature of the flood is important for success of deepwater rice, with timing and the rate of rise of water affecting survival and crop density. Generally, the flood water comes from rainfall or rises in the

water table The water table is the upper surface of the zone of saturation. The zone of saturation is where the pores and fractures of the ground are saturated with water. It can also be simply explained as the depth below which the ground is saturated. T ...

. In places with low rainfall, water overspilling from rivers can flood rice-producing areas.

Issues

When seeds are sown directly into the soil, the seeds and young plants can be damaged by

drought A drought is defined as drier than normal conditions.Douville, H., K. Raghavan, J. Renwick, R.P. Allan, P.A. Arias, M. Barlow, R. Cerezo-Mota, A. Cherchi, T.Y. Gan, J. Gergis, D. Jiang, A. Khan, W. Pokam Mba, D. Rosenfeld, J. Tierney, an ...

conditions before floods arrive. During this stage, the plants can also suffer due to competition from weeds. Sudden flooding, where a large volume of water enters the field in a short time, can lead to a high level of seedling death. Floating rice faces additional problems due to the depth and time of the water in which it grows. Water conditions such as

turbulence In fluid dynamics, turbulence or turbulent flow is fluid motion characterized by chaotic changes in pressure and flow velocity. It is in contrast to a laminar flow, which occurs when a fluid flows in parallel layers, with no disruption between ...

and temperature can adversely affect the crop. Natural disasters can also damage or destroy deepwater rice crops.

Tropical cyclone A tropical cyclone is a rapidly rotating storm system characterized by a low-pressure center, a closed low-level atmospheric circulation, strong winds, and a spiral arrangement of thunderstorms that produce heavy rain and squalls. Depen ...

s are particularly a problem in Asia. For example, in 2008,

Cyclone Nargis Extremely Severe Cyclonic Storm Nargis ( my, နာဂစ်, ur, نرگس ) was an extremely destructive and deadly tropical cyclone that caused the worst natural disaster in the recorded history of Myanmar during early May 2008. The cyclone m ...

damaged 122,782 hectares of deepwater rice in Burma. If predicted

sea level Mean sea level (MSL, often shortened to sea level) is an average surface level of one or more among Earth's coastal bodies of water from which heights such as elevation may be measured. The global MSL is a type of vertical datuma standardise ...

rises due to

climate change In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to ...

happen, this would affect the pattern of flooding, causing deeper floods over a wider area and eroding the coast. Deepwater rice emits the least

methane Methane ( , ) is a chemical compound with the chemical formula (one carbon atom bonded to four hydrogen atoms). It is a group-14 hydride, the simplest alkane, and the main constituent of natural gas. The relative abundance of methane on Ea ...

, a greenhouse gas, of the wetland rice ecologies, producing approximately one third of emissions compared to paddy field rice.

Floating rice adaptation

Floating rice is planted in dry ground and allowed to establish as young plants. The area becomes flooded which triggers the rice's elongation ability. This means when a field where rice is growing floods, accelerated growth in the

internodes A stem is one of two main structural axes of a vascular plant, the other being the root. It supports leaves, flowers and fruits, transports water and dissolved substances between the roots and the shoots in the xylem and phloem, stores nutrien ...

of the stem allows the plant to keep some of its

foliage A leaf ( : leaves) is any of the principal appendages of a vascular plant stem, usually borne laterally aboveground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leaves, s ...

on top of the water. The stems are hollow and this allows gas to be exchanged between the plant and the atmosphere. Once the flooding ends, the plant is left lying on the ground. The nodes at the top of the plant then start growing upwards towards due to gravitropic sensitivity. The elongation is triggered when the plant is submerged through a mechanism involving ethylene gas. Ethylene is normally produced by plants and diffused into the air, but when floating rice is submerged in water, this process is disrupted as the gas moves more slowly into water. This leads to a buildup of ethylene in the plant. This triggers the production of a

hormone A hormone (from the Greek participle , "setting in motion") is a class of signaling molecules in multicellular organisms that are sent to distant organs by complex biological processes to regulate physiology and behavior. Hormones are require ...

called

gibberellin Gibberellins (GAs) are plant hormones that regulate various developmental processes, including stem elongation, germination, dormancy, flowering, flower development, and leaf and fruit senescence. GAs are one of the longest-known classes of plan ...

which causes the rapid growth in the plant. When the plant reaches the surface, the ethylene gas can escape as normal and the rapid growth stops. Research continues to enhance the ability to cope with increasing water depth. Rice will drown if submerged for too long.

New cultivars

A recent cultivar named Swarna Sub1 was developed via marker-assisted selection, with the ability to withstand prolonged periods of around 14 days beneath a flooded plain. The submergence tolerance ability of this variety is conferred by the presence of the Sub1A gene, introgressed from the Indian cultivar FR13A into the flood-vulnerable (but high yielding) cultivar Swarna.Climate change-ready rice
, International Rice Research Institute (IRRI). Retrieved October 31, 2013. Swarna Sub1 effectively enters a dormant, energy-conserving state upon being submerged in a flooded rice paddy, a process that involves the finely controlled

metabolism Metabolism (, from el, μεταβολή ''metabolē'', "change") is the set of life-sustaining chemical reactions in organisms. The three main functions of metabolism are: the conversion of the energy in food to energy available to run c ...

of enzymes such amylases, starch phosphorylase and

alcohol dehydrogenase Alcohol dehydrogenases (ADH) () are a group of dehydrogenase enzymes that occur in many organisms and facilitate the interconversion between alcohols and aldehydes or ketones with the reduction of nicotinamide adenine dinucleotide (NAD+) to NA ...

, allowing the plant to survive with limited oxygen and sunlight unlike its standard variety relatives. Given that the presence of the Sub1A gene does not impact upon the quality or quantity of the rice obtained, this variety has been very popular, with 1.7 million hectares of land in

India India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the seventh-largest country by area, the second-most populous country, and the most populous democracy in the world. Bounded by the Indian Ocean on the so ...

having Swarna Sub1 and other flood-resistant varieties used instead of conventional rice crops.Best minds meet to help crops survive flooding
" International Rice Research Institute (IRRI) (2013). Retrieved October 31, 2013.

References

Bibliography

* *{{Cite book, last =De Datta, first =Surajit K. , title =Principles and Practices of Rice Production, publisher =Int. Rice Res. Inst., year = 1981, url =https://books.google.com/books?id=0odDhoWN7DIC&pg=PA244, isbn=978-0-471-09760-0 Rice