Zea mays

Classification System: APG IV

Superregnum: Eukaryota
Regnum: Plantae
Cladus: Angiosperms
Cladus: Monocots
Cladus: Commelinids
Ordo: Poales

Familia: Poaceae
Subfamilia: Panicoideae
Tribus: Andropogoneae
Subtribus: Tripsacinae
Genus: Zea
Species: Zea sect. Zea
Species: Z. mays
Subspecies: Z. m. subsp. mays – Z. m. subsp. huehuetenangensis – Z. m. subsp. parviglumis
Name

Zea mays L. Sp. Pl. 1: 971 (1753)
Synonyms

Homotypic
Mays zea Gaertn., Fruct. Sem. Pl. 1: 6 (1788), nom. superfl.
Zea segetalis Salisb., Prodr. Stirp. Chap. Allerton: 28 (1796), nom. superfl.
Mays americana Baumg., Enum. Stirp. Transsilv. 3: 281 (1816), nom. superfl.
Mayzea cerealis Raf., Med. Fl. 2: 241 (1830), nom. superfl.
Thalysia mays (L.) Kuntze, Revis. Gen. Pl. 2: 794 (1891)

Distribution
Native distribution areas:

Continental: Southern America
Regional: Central America
Guatemala
Continental: Northern America
Regional: Mexico
Mexico Central, Mexico Southwest
Introduced into:
Afghanistan, Alabama, Albania, Aldabra, Algeria, Amur, Andaman Is., Angola, Argentina Northeast, Arizona, Arkansas, Aruba, Assam, Austria, Azores, Bahamas, Baleares, Baltic States, Bangladesh, Belarus, Belgium, Belize, Benin, Bismarck Archipelago, Bolivia, Borneo, Brazil North, Brazil Northeast, Brazil South, Brazil Southeast, Brazil West-Central, Bulgaria, Burkina, Burundi, California, Cambodia, Cameroon, Canary Is., Caroline Is., Cayman Is., Central African Repu, Central European Rus, Chad, Chagos Archipelago, China North-Central, China South-Central, China Southeast, Christmas I., Colombia, Colorado, Comoros, Connecticut, Corse, Costa Rica, Cuba, Cyprus, Czechoslovakia, Djibouti, Dominican Republic, East European Russia, East Himalaya, Ecuador, Egypt, Equatorial Guinea, Ethiopia, Fiji, Florida, France, French Guiana, Galápagos, Gambia, Georgia, Germany, Ghana, Great Britain, Greece, Guinea, Guinea-Bissau, Gulf of Guinea Is., Hainan, Haiti, Hawaii, Honduras, Hungary, Idaho, Illinois, India, Indiana, Iowa, Iraq, Ireland, Italy, Ivory Coast, Jamaica, Japan, Jawa, Kansas, Kazakhstan, Kentucky, Khabarovsk, Kirgizstan, Korea, Kriti, Krym, Laos, Leeward Is., Lesser Sunda Is., Louisiana, Madagascar, Maine, Malaya, Mali, Maluku, Manchuria, Marianas, Marshall Is., Maryland, Massachusetts, Mauritius, Mexico Gulf, Mexico Northeast, Mexico Northwest, Mexico Southeast, Minnesota, Mississippi, Missouri, Montana, Morocco, Mozambique, Myanmar, Nansei-shoto, Nebraska, Nepal, Netherlands, Netherlands Antilles, Nevada, New Caledonia, New Guinea, New Hampshire, New Jersey, New Mexico, New York, Nicaragua, Niger, Nigeria, Niue, North Carolina, North Caucasus, Northwest European R, Ohio, Oman, Ontario, Oregon, Pakistan, Panamá, Pennsylvania, Peru, Philippines, Pitcairn Is., Poland, Portugal, Primorye, Puerto Rico, Queensland, Québec, Rhode I., Rodrigues, Romania, Rwanda, Réunion, Sakhalin, Samoa, Sardegna, Seychelles, Sicilia, Sierra Leone, Somalia, South Carolina, South European Russi, Spain, Sri Lanka, Sudan, Switzerland, Tadzhikistan, Tanzania, Tennessee, Texas, Thailand, Togo, Transcaucasus, Trinidad-Tobago, Tunisia, Turkey, Turkey-in-Europe, Turkmenistan, Ukraine, Uruguay, Utah, Uzbekistan, Vanuatu, Venezuelan Antilles, Vermont, Vietnam, Virginia, Wake I., Washington, West Himalaya, West Virginia, Western Australia, Windward Is., Wisconsin, Wyoming, Yemen, Yugoslavia, Zambia, Zaïre

References: Brummitt, R.K. 2001. TDWG – World Geographical Scheme for Recording Plant Distributions, 2nd Edition
References
Primary references

Linnaeus, C. 1753. Species Plantarum. Tomus II: 971. Reference page.

Additional references

Clayton, W.D., Harman, K.T. & Williamson, H. (2006). World Grass Species - Synonymy database The Board of Trustees of the Royal Botanic Gardens, Kew.

Links

Govaerts, R. et al. 2013. Zea mays in Kew Science Plants of the World online. The Board of Trustees of the Royal Botanic Gardens, Kew. Published online. Accessed: 2013 Dec. 2. Reference page.
Simon, B.K., Clayton, W.D., Harman, K.T., Vorontsova, M., Brake, I., Healy, D. & Alfonso, Y. 2013. GrassWorld, Zea mays. Published online. Accessed: 2013 Dec. 2.
Tropicos.org 2013. Zea mays. Missouri Botanical Garden. Published online. Accessed: 2 Dec. 2013.
International Plant Names Index. 2013. Zea mays. Published online. Accessed: 2 Dec. 2013.
USDA, ARS, Germplasm Resources Information Network. Zea mays in the Germplasm Resources Information Network (GRIN), U.S. Department of Agriculture Agricultural Research Service.

Vernacular names
Akan: Aburoo
العربية: ذرة (نبات)
asturianu: Maíz
Boarisch: Gugaruz
беларуская: Кукуруза
български: Царевица
bamanankan: Kaba
বাংলা: ভুট্টা
català: Dacsa
čeština: Kukuřice
dansk: Majs
Deutsch: Mais
eʋegbe: Bli
Ελληνικά: Καλαμπόκι
English: Maize
Esperanto: Maizo
español: Maíz
eesti: Mais
فارسی: ذرت
suomi: Maissi
Nordfriisk: Meis
français: Maïs
עברית: תירס
हिन्दी: मक्का
magyar: Kukorica
Bahasa Indonesia: Jagung
Ido: Maizo
íslenska: Maís
italiano: Mais
日本語: トウモロコシ
la .lojban.: Zumri
Jawa: Jagung
latviešu: Parastā kukurūza
македонски: Пченка
Bahasa Melayu: Jagung
Nederlands: Maïs
norsk: Mais
ਪੰਜਾਬੀ: ਮੱਕੀ
polski: Kukurydza
português: Milho
русский: Кукуруза
slovenčina: Kukurica siata
slovenščina: Koruza
српски / srpski: Кукуруз
svenska: Majs
தமிழ்: சோளம்
ไทย: ข้าวโพด
Türkçe: Mısır
ئۇيغۇرچە / Uyghurche: ظات حعشلعق قوناق
vèneto: Formenton
Volapük: Mait
walon: Dinrêye
Yorùbá: Agbado
中文: 玉米

---------------

Maize (Zea mays L. ssp. mays, pronounced /ˈmeɪz/; also known in many English-speaking countries as corn), is a grass domesticated by indigenous peoples in Mesoamerica in prehistoric times. The Aztecs and Mayans cultivated it in numerous varieties throughout central and southern Mexico, to cook or grind in a process called nixtamalization. Later the crop spread through much of the Americas. Between 1250 A.D. and 1700 A.D. nearly the whole continent had gained access to the crop. Any significant or dense populations in the region developed a great trade network based on surplus and varieties of maize crops. After European contact with the Americas in the late 15th and early 16th centuries, explorers and traders carried maize back to Europe and introduced it to other countries through trade. Its ability to grow in distinct climates, and its use were highly valued, thus spreading to the rest of the world.

Maize is the most widely grown crop in the Americas with 332 million metric tons grown annually in the United States alone. Transgenic maize comprised 80% of the maize planted in the United States[1]. While some maize varieties grow up to 7 metres (23 ft) tall,[2] most commercially grown maize has been bred for a standardized height of 2.5 metres (8.2 ft). Sweet corn is usually shorter than field-corn varieties.

Naming conventions
The term maize derives from the Spanish form of the indigenous Taino word maiz for the plant. This was the term used in the United Kingdom and Ireland, where it is now usually called "sweet corn", the most common form of the plant known to people there.[3]

Outside the British Isles, another common term for maize is "corn". This was originally the English term for any cereal crop. In North America, its meaning has been restricted since the 19th century to maize, as it was shortened from "Indian corn."[4] The term Indian corn now refers specifically to multi-colored "field corn" (flint corn) cultivars.[5]

In scientific and formal usage, "maize" is normally used in a global context. Equally, in bulk-trading contexts, "corn" is used most frequently. In the UK, Australia and other English-speaking countries, the word "corn" is often used in culinary contexts, particularly in naming products such as popcorn and corn flakes. "Maize" is used in agricultural and scientific references.[6]

In Southern Africa, maize is commonly referred to as mielie or mealie, from the Portuguese milho.[7] Mielie-meal is the ground form.

Structure and physiology
Maize stems superficially resemble bamboo canes and the internodes can reach 20–30 centimetres (8–12 in). Maize has a distinct growth form; the lower leaves being like broad flags, 50–100 centimetres long and 5–10 centimetres wide (2–4 ft by 2–4 in); the stems are erect, conventionally 2–3 metres (7–10 ft) in height, with many nodes, casting off flag-leaves at every node. Under these leaves and close to the stem grow the ears. They grow about 3 millimetres a day.

The ears are female inflorescences, tightly covered over by several layers of leaves, and so closed-in by them to the stem that they do not show themselves easily until the emergence of the pale yellow silks from the leaf whorl at the end of the ear. The silks are elongated stigmas that look like tufts of hair, at first green, and later red or yellow. Plantings for silage are even denser, and achieve a lower percentage of ears and more plant matter. Certain varieties of maize have been bred to produce many additional developed ears. These are the source of the "baby corn" used as a vegetable in Asian cuisine.

Maize is a facultative long-night plant and flowers in a certain number of growing degree days > 50 °F (10 °C) in the environment to which it is adapted.[8] The magnitude of the influence that long nights have on the number of days that must pass before maize flowers is genetically prescribed and regulated by the phytochrome system.[9] Photoperiodicity can be eccentric in tropical cultivars, while the long days characteristic of higher latitudes allow the plants to grow so tall that they do not have enough time to produce seed before being killed by frost. These attributes, however, may prove useful in using tropical maize for biofuels.[10]
The apex of the stem ends in the tassel, an inflorescence of male flowers. When the tassel is mature and conditions are suitably warm and dry, anthers on the tassel dehisce and release pollen. Maize pollen is anemophilous (dispersed by wind) and because of its large settling velocity most pollen falls within a few meters of the tassel. Each silk may become pollinated to produce one kernel of maize. Young ears can be consumed raw, with the cob and silk, but as the plant matures (usually during the summer months) the cob becomes tougher and the silk dries to inedibility. By the end of the growing season, the kernels dry out and become difficult to chew without cooking them tender first in boiling water. Modern farming techniques in developed countries usually rely on dense planting, which produces one large ear per stalk.

Seeds

The kernel of maize has a pericarp of the fruit fused with the seed coat, typical of the grasses, and the entire kernel is often referred to as the seed. The cob is close to a multiple fruit in structure, except that the individual fruits (the kernels) never fuse into a single mass. The grains are about the size of peas, and adhere in regular rows round a white pithy substance, which forms the ear. An ear contains from 200 to 400 kernels, and is from 10–25 centimetres (4–10 inches) in length. They are of various colors: blackish, bluish-gray, purple, green, red, white and yellow. When ground into flour, maize yields more flour, with much less bran, than wheat does. However, it lacks the protein gluten of wheat and, therefore, makes baked goods with poor rising capability and coherence.

A genetic variant that accumulates more sugar and less starch in the ear is consumed as a vegetable and is called sweet corn.

Immature maize shoots accumulate a powerful antibiotic substance, DIMBOA (2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one). DIMBOA is a member of a group of hydroxamic acids (also known as benzoxazinoids) that serve as a natural defense against a wide range of pests including insects, pathogenic fungi and bacteria. DIMBOA is also found in related grasses, particularly wheat. A maize mutant (bx) lacking DIMBOA is highly susceptible to be attacked by aphids and fungi. DIMBOA is also responsible for the relative resistance of immature maize to the European corn borer (family Crambidae). As maize matures, DIMBOA levels and resistance to the corn borer decline.

Because of its shallow roots, maize is susceptible to droughts, intolerant of nutrient-deficient soils, and prone to be uprooted by severe winds.[11]

Some hazards of maize in the diet
Pellagra
Main article: Pellagra

When maize was first introduced into other farming systems than those used by traditional native-American peoples, it was generally welcomed with enthusiasm for its productivity. However, a widespread problem of malnutrition soon arose wherever maize was introduced as a staple food. This was a mystery since these types of malnutrition were not normally seen among the indigenous Americans, to whom maize was the principal staple food.[12]

It was eventually discovered that the indigenous Americans learned long ago to soak maize in alkali-water—made with ashes by North Americans and lime (calcium oxide) by Mesoamericans—which liberates the B-vitamin niacin, the lack of which was the underlying cause of the condition known as pellagra. This alkali process is known by its Nahuatl (Aztec)-derived name: nixtamalization.

Besides the lack of niacin, pellagra was also characterized by protein deficiency, a result of the inherent lack of two key amino acids in pre-modern maize, lysine and tryptophan. Nixtamalisation was also found to increase the availability of lysine and tryptophan to some extent, but more importantly, the indigenous Americans had learned long ago to balance their consumption of maize with beans and other protein sources such as amaranth and chia, as well as meat and fish, in order to acquire the complete range of amino acids for normal protein synthesis.

Since maize had been introduced into the diet of non-indigenous Americans without the necessary cultural knowledge acquired over thousands of years in the Americas, the reliance on maize in other cultures was often tragic. In the late 19th century pellagra reached epidemic proportions in parts of the deep southern U.S., as medical researchers debated two theories for its origin: the deficiency theory (eventually shown to be true) posited that pellagra was due to a deficiency of some nutrient, and the germ theory posited that pellagra was caused by a germ transmitted by stable flies. In 1914 the U.S. government officially endorsed the germ theory of pellagra, but rescinded this endorsement several years later as evidence grew against it. By the mid-1920s the deficiency theory of pellagra was becoming scientific consensus, and the theory was proved in 1932 when niacin deficiency was determined to be the cause of the illness.

Once alkali processing and dietary variety was understood and applied, pellagra disappeared. The development of high lysine maize and the promotion of a more balanced diet has also contributed to its demise.

Allergy

Maize contains lipid transfer protein, an indigestible protein that survives cooking. This protein has been linked to a rare and understudied allergy to maize in humans.[13] The allergic reaction can cause skin rash, swelling or itching of mucus membranes, diarrhea, vomiting, asthma and, in severe cases, anaphylaxis. It is unclear how common this allergy is in the general population.

Genetics
Many forms of maize are used for food, sometimes classified as various subspecies related to the amount of starch each had:

* Flour corn — Zea mays var. amylacea
* Popcorn — Zea mays var. everta
* Dent corn — Zea mays var. indentata
* Flint corn — Zea mays var. indurata
* Sweet corn — Zea mays var. saccharata and Zea mays var. rugosa
* Waxy corn — Zea mays var. ceratina
* Amylomaize — Zea mays
* Pod corn — Zea mays var. tunicata Larrañaga ex A. St. Hil.
* Striped maize — Zea mays var. japonica

This system has been replaced (though not entirely displaced) over the last 60 years by multi-variable classifications based on ever more data. Agronomic data were supplemented by botanical traits for a robust initial classification, then genetic, cytological, protein and DNA evidence was added. Now the categories are forms (little used), races, racial complexes, and recently branches.

Maize has 10 chromosomes (n=10). The combined length of the chromosomes is 1500 cM. Some of the maize chromosomes have what are known as "chromosomal knobs": highly repetitive heterochromatic domains that stain darkly. Individual knobs are polymorphic among strains of both maize and teosinte.

Barbara McClintock used these knob markers to prove her transposon theory of "jumping genes", for which she won the 1983 Nobel Prize in Physiology or Medicine. Maize is still an important model organism for genetics and developmental biology today.[14]

The Maize Genetics Cooperation Stock Center, funded by the USDA Agricultural Research Service and located in the Department of Crop Sciences at the University of Illinois at Urbana-Champaign, is a stock center of maize mutants. The total collection has nearly 80,000 samples. The bulk of the collection consists of several hundred named genes, plus additional gene combinations and other heritable variants. There are about 1000 chromosomal aberrations (e.g., translocations and inversions) and stocks with abnormal chromosome numbers (e.g., tetraploids). Genetic data describing the maize mutant stocks as well as myriad other data about maize genetics can be accessed at MaizeGDB, the Maize Genetics and Genomics Database.[15]

In 2005, the U.S. National Science Foundation (NSF), Department of Agriculture (USDA) and the Department of Energy (DOE) formed a consortium to sequence the B73 maize genome. The resulting DNA sequence data was deposited immediately into GenBank, a public repository for genome-sequence data. Sequences and genome annotations have also been made available throughout the project's lifetime at the project's official site, MaizeSequence.org.

Primary sequencing of the maize genome was completed in 2008[16]. On November 20, 2009, the consortium published results of its sequencing effort in Science[17]. The genome, 85% of which is composed of transposons, was found to contain 32,540 genes (By comparison, the human genome contains about 2.9 billion bases and 26,000 genes).

Origin

There are several theories about the specific origin of maize in Mesoamerica:[18]

1. It may be a direct domestication of a Mexican annual teosinte, Zea mays ssp. parviglumis, native to the Balsas River valley in south-eastern Mexico, with up to 12% of its genetic material obtained from Zea mays ssp. mexicana through introgression.
2. It may have been derived from hybridization between a small domesticated maize (a slightly changed form of a wild maize) and a teosinte of section Luxuriantes, either Z. luxurians or Z. diploperennis.
3. It may have undergone two or more domestications either of a wild maize or of a teosinte.
4. It may have evolved from a hybridization of Z. diploperennis by Tripsacum dactyloides. (The term "teosinte" describes all species and subspecies in the genus Zea, excluding Zea mays ssp. mays.) In the late 1930s, Paul Mangelsdorf suggested that domesticated maize was the result of a hybridization event between an unknown wild maize and a species of Tripsacum, a related genus. However, the proposed role of tripsacum (gama grass) in the origins of maize has been refuted by modern genetic testing, refuting Mangelsdorf’s model and the fourth listed above.

The first model was proposed by Nobel Prize winner George Beadle in 1939. Though it has experimental support, it has not explained a number of problems, among them:

1. how the immense diversity of the species of sect. Zea originated,
2. how the tiny archaeological specimens of 3500–2700 BC could have been selected from a teosinte, and
3. how domestication could have proceeded without leaving remains of teosinte or maize with teosintoid traits until ca. 1100 BC.

The domestication of maize is of particular interest to researchers — archaeologists, geneticists, ethnobotanists, geographers, etc. The process is thought by some to have started 7,500 to 12,000 years ago. Research from the 1950s to 1970s originally focused on the hypothesis that maize domestication occurred in the highlands between Oaxaca and Jalisco, due to the fact that the oldest known examples of maize were found there. Both archaeological and botanical studies published in 2009 now point to the lowlands of the Balsas River valley, at least 8,700 years ago.[19] The crop wild relative teosinte most similar to modern maize grows in the area of the Balsas River. Some of the earliest pollen remains from Latin America have been found in lake sediments from tropics of southern Mexico and upper Central America, up to Laguna Martinez and have been radiocarbon dated to around 4,700 years ago. Archaeological remains of early maize ears, found at Guila Naquitz Cave in the Oaxaca Valley, date back roughly 6,250 years; the oldest ears from caves near Tehuacan, Puebla, date ca. 2750 BC. Little change occurred in ear form until ca. 1100 BC when great changes appeared in ears from Mexican caves: maize diversity rapidly increased and archaeological teosinte was first deposited.
Perhaps as early as 1500 BC, maize began to spread widely and rapidly. As it was introduced to new cultures, new uses were developed and new varieties selected to better serve in those preparations. Maize was the staple food, or a major staple, of most pre-Columbian North American, Mesoamerican, South American, and Caribbean cultures. The Mesoamerican civilization was strengthened upon the field crop of maize; through harvesting it, its religious and spiritual importance and how it impacted their diet. Maize formed the Mesoamerican people’s identity. During the 1st millennium AD, maize cultivation spread from Mexico into the U.S. Southwest and a millennium later into U.S. Northeast and southeastern Canada, transforming the landscape as Native Americans cleared large forest and grassland areas for the new crop.

It is unknown what precipitated its domestication, because the edible portion of the wild variety is too small and hard to obtain to be eaten directly, as each kernel is enclosed in a very hard bi-valve shell. However, George Beadle demonstrated that the kernels of teosinte are readily "popped" for human consumption, like modern popcorn. Some have argued that it would have taken too many generations of selective breeding in order to produce large compressed ears for efficient cultivation. However, studies of the hybrids readily made by intercrossing teosinte and modern maize suggest that this objection is not well founded.

In 2005, research by the USDA Forest Service indicated that the rise in maize cultivation 500 to 1,000 years ago in what is now the southeastern United States contributed to the decline of freshwater mussels, which are very sensitive to environmental changes.[20]

Perhaps as early as 1500 BC, maize began to spread widely and rapidly. As it was introduced to new cultures, new uses were developed and new varieties selected to better serve in those preparations. Maize was the staple food, or a major staple, of most pre-Columbian North American, Mesoamerican, South American, and Caribbean cultures. The Mesoamerican civilization was strengthened upon the field crop of maize; through harvesting it, its religious and spiritual importance and how it impacted their diet. Maize formed the Mesoamerican people’s identity. During the 1st millennium AD, maize cultivation spread from Mexico into the U.S. Southwest and a millennium later into U.S. Northeast and southeastern Canada, transforming the landscape as Native Americans cleared large forest and grassland areas for the new crop.

It is unknown what precipitated its domestication, because the edible portion of the wild variety is too small and hard to obtain to be eaten directly, as each kernel is enclosed in a very hard bi-valve shell. However, George Beadle demonstrated that the kernels of teosinte are readily "popped" for human consumption, like modern popcorn. Some have argued that it would have taken too many generations of selective breeding in order to produce large compressed ears for efficient cultivation. However, studies of the hybrids readily made by intercrossing teosinte and modern maize suggest that this objection is not well founded.

In 2005, research by the USDA Forest Service indicated that the rise in maize cultivation 500 to 1,000 years ago in what is now the southeastern United States contributed to the decline of freshwater mussels, which are very sensitive to environmental changes.[20]

Maize is widely cultivated throughout the world, and a greater weight of maize is produced each year than any other grain. The United States produces almost half of the world's harvest (~42.5%), other top producing countries includes China, Brazil, Mexico, Argentina, India and France. Worldwide production was around 800 million tonnes in 2007—just slightly more than rice (~650 million tonnes) or wheat (~600 million tonnes). In 2007, over 150 million hectares of maize were planted worldwide, with a yield of 4970.9 kilogram/hectare. Production can be significantly higher in certain regions of the world; 2009 forecasts for production in Iowa were 11614 kg/ha.[21] "There is conflicting evidence to support the hypothesis that maize yield potential has increased" over the past few decades. [22]

Because it is cold-intolerant, in the temperate zones maize must be planted in the spring. Its root system is generally shallow, so the plant is dependent on soil moisture. As a C4 plant (a plant that uses C4 carbon fixation), maize is a considerably more water-efficient crop than C3 plants (plants that use C3 carbon fixation) like the small grains, alfalfa and soybeans. Maize is most sensitive to drought at the time of silk emergence, when the flowers are ready for pollination. In the United States, a good harvest was traditionally predicted if the corn was "knee-high by the Fourth of July," although modern hybrids generally exceed this growth rate. Maize used for silage is harvested while the plant is green and the fruit immature. Sweet corn is harvested in the "milk stage," after pollination but before starch has formed, between late summer and early to mid-autumn. Field maize is left in the field very late in the autumn in order to thoroughly dry the grain, and may, in fact, sometimes not be harvested until winter or even early spring. The importance of sufficient soil moisture is shown in many parts of Africa, where periodic drought regularly causes famine by causing maize crop failure.

Maize was planted by the Native Americans in hills, in a complex system known to some as the Three Sisters. Maize provided support for beans, and the beans provided nitrogen derived from nitrogen-fixing bacteria which live on the roots of beans and other legumes; and squashes provided ground cover to stop weeds and inhibit evaporation by providing shade over the soil. This method was replaced by single species hill planting where each hill 60–120 cm (2.0–3.9 ft) apart was planted with 3 or 4 seeds, a method still used by home gardeners. A later technique was checked maize where hills were placed 40 inches apart in each direction, allowing cultivators to run through the field in two directions. In more arid lands this was altered and seeds were planted in the bottom of 10–12 cm (3.9–4.7 in) deep furrows to collect water. Modern technique plants maize in rows which allows for cultivation while the plant is young, although the hill technique is still used in the maize fields of some Native American reservations.

In North America, fields are often planted in a two-crop rotation with a nitrogen-fixing crop, often alfalfa in cooler climates and soybeans in regions with longer summers. Sometimes a third crop, winter wheat, is added to the rotation.

Many of the maize varieties grown in the United States and Canada are hybrids. Often the varieties have been genetically modified to tolerate glyphosate or to provide protection against natural pests. Glyphosate (trade name Roundup) is an herbicide which kills all plants except those with genetic tolerance. This genetic tolerance is very rarely found in nature.

In midwestern United States, low-till or no-till farming techniques are usually used. In low-till, fields are covered once, maybe twice, with a tillage implement either ahead of crop planting or after the previous harvest. The fields are planted and fertilized. Weeds are controlled through the use of herbicides and no cultivation tillage is done during the growing season. This technique reduces moisture evaporation from the soil and thus provides more moisture for the crop. The technologies mentioned in the previous paragraph enable low-till and no-till farming. Weeds compete with the crop for moisture and nutrients, making them undesirable.

efore about World War II, most maize in North America was harvested by hand (as it still is in most of the other countries where it is grown). This often involved large numbers of workers and associated social events. Some one- and two-row mechanical pickers were in use but the maize combine was not adopted until after the War. By hand or mechanical picker, the entire ear is harvested which then requires a separate operation of a maize sheller to remove the kernels from the ear. Whole ears of maize were often stored in corn cribs and these whole ears are a sufficient form for some livestock feeding use. Few modern farms store maize in this manner. Most harvest the grain from the field and store it in bins. The combine with a maize head (with points and snap rolls instead of a reel) does not cut the stalk; it simply pulls the stalk down. The stalk continues downward and is crumpled in to a mangled pile on the ground. The ear of maize is too large to pass between slots in a plate as the snap rolls pull the stalk away, leaving only the ear and husk to enter the machinery. The combine separates out the husk and the cob, keeping only the kernels.

Genetic Modification

efore about World War II, most maize in North America was harvested by hand (as it still is in most of the other countries where it is grown). This often involved large numbers of workers and associated social events. Some one- and two-row mechanical pickers were in use but the maize combine was not adopted until after the War. By hand or mechanical picker, the entire ear is harvested which then requires a separate operation of a maize sheller to remove the kernels from the ear. Whole ears of maize were often stored in corn cribs and these whole ears are a sufficient form for some livestock feeding use. Few modern farms store maize in this manner. Most harvest the grain from the field and store it in bins. The combine with a maize head (with points and snap rolls instead of a reel) does not cut the stalk; it simply pulls the stalk down. The stalk continues downward and is crumpled in to a mangled pile on the ground. The ear of maize is too large to pass between slots in a plate as the snap rolls pull the stalk away, leaving only the ear and husk to enter the machinery. The combine separates out the husk and the cob, keeping only the kernels.

Genetic Modification

Food

See also Some hazards of maize in the diet (above).

Maize and cornmeal (ground dried maize) constitutes a staple food in many regions of the world. Maize meal is made into a thick porridge in many cultures: from the polenta of Italy, the angu of Brazil, the mămăligă of Romania, to mush in the U.S. or the food called sadza, nshima, ugali, and mealie pap in Africa. Maize meal is also used as a replacement for wheat flour, to make cornbread and other baked products. Masa (cornmeal treated with lime water) is the main ingredient for tortillas, atole and many other dishes of Mexican food.

Popcorn is kernels of certain varieties that explode when heated, forming fluffy pieces that are eaten as a snack. Roasted dried maize cobs with semi-hardened kernels, coated with a seasoning mixture of fried chopped spring onions with salt added to the oil, is a popular snack food in Vietnam. A unleavened bread called Makki di roti is a popular bread eaten in the Punjab region of India and Pakistan.

Chicha and "chicha morada" (purple chicha) are drinks made usually from particular types of maize. The first one is fermented and alcoholic, the second is a soft drink commonly drunk in Peru.

Corn flakes are a common breakfast cereal in North America and the United Kingdom, and found in many other countries all over the world.

Maize can also be prepared as hominy, in which the kernels are soaked with lye in a process called nixtamalization; or grits, which are coarsely ground hominy. These are commonly eaten in the Southeastern United States, foods handed down from Native Americans, who called the dish sagamite.

The Brazilian dessert canjica is made by boiling maize kernels in sweetened milk.

Maize can also be harvested and consumed in the unripe state, when the kernels are fully grown but still soft. Unripe maize must usually be cooked to become palatable; this may be done by simply boiling or roasting the whole ears and eating the kernels right off the cob. Such corn on the cob is a common dish in the United States, Canada, United Kingdom and some parts of South America, but virtually unheard of in some European countries. The cooked unripe kernels may also be shaved off the cob and served as a vegetable in side dishes, salads, garnishes, etc. Alternatively, the raw unripe kernels may also be grated off the cobs and processed into a variety of cooked dishes, such as maize purée, tamales, pamonhas, curau, cakes, ice creams, etc. Sweetcorn, a genetic variety that is high in sugars and low in starch, is usually consumed in the unripe state.

Corn on the cob, as it is usually called in the United States, was hawked on the streets of early 19th-century New York City by poor, barefoot "Hot Corn Girls", who were thus the precursors hot-dog carts, churro wagons, and fruit stands seen on the streets of big cities today.[24]

Maize is a major source of starch. Cornstarch (maize flour) is a major ingredient in home cooking and in many industrialized food products. Maize is also a major source of cooking oil (corn oil) and of maize gluten. Maize starch can be hydrolyzed and enzymatically treated to produce syrups, particularly high fructose corn syrup, a sweetener; and also fermented and distilled to produce grain alcohol. Grain alcohol from maize is traditionally the source of bourbon whiskey. Maize is sometimes used as the starch source for beer.

Within the United States, the usage of maize for human consumption constitutes about 1/40th of the amount of grown in the country. In the United States and Canada maize is mostly grown to feed for livestock, as forage, silage (made by fermentation of chopped green cornstalks), or grain. Maize meal is also a significant ingredient of some commercial animal food products, such as dog food

Maize is also used as a fish bait, called "dough balls". It is particularly popular in Europe for coarse fishing.
Chemicals and medicines

Starch from maize can also be made into plastics, fabrics, adhesives, and many other chemical products.

Stigmas from female maize flowers, known popularly as corn silk, are sold as herbal supplements.

The corn steep liquor, a plentiful watery byproduct of maize wet milling process, is widely used in the biochemical industry and research as a culture medium to grow many kinds of microorganisms.[25]

Biofuel

"Feed maize" is being used increasingly for heating; specialized corn stoves (similar to wood stoves) are available and use either feed maize or wood pellets to generate heat. Maizecobs are also used as a biomass fuel source. Maize is relatively cheap and home-heating furnaces have been developed which use maize kernels as a fuel. They feature a large hopper that feeds the uniformly sized maize kernels (or wood pellets or cherry pits) into the fire.

Maize is increasingly used as a feedstock for the production of ethanol fuel. Ethanol is mixed with gasoline in order to decrease the amount of pollutants emitted when used to fuel motor vehicles. High fuel prices in mid 2007 led to higher demand for ethanol, which in turn lead to higher prices paid to farmers for maize. This led to the 2007 harvest being one of the most profitable maize crops in modern history for farmers. Because of the relationship between fuel and maize, prices paid for the crop now tend to track the price of oil.

The price of food is affected to a certain degree by the use of maize for biofuel production. Transportation, production, and marketing costs are a large portion (80%) of the price of food in the United States. Higher energy costs affect these costs, especially transportation. The increase in food prices the consumer has been seeing is mainly due to the higher energy cost. The affect of biofuel production on other food crop prices is indirect. Use of maize for biofuel production increases the demand, and therefore price of maize. This in turn results in farm acreage being diverted from other food crops to maize production. This reduces the supply of the other food crops and increases their prices.[26][27]

Maize is widely used in Germany as a feedstock for biogas plants. Here the maize is harvested, shredded then placed in silage clamps from which it is fed into the biogas plants.

A biomass gasification power plant in Strem near Güssing, Burgenland, Austria was begun in 2005. Research is being done to make diesel out of the biogas by the Fischer Tropsch method.

Increasingly ethanol is being used at low concentrations (10% or less) as an additive in gasoline (gasohol) for motor fuels to increase the octane rating, lower pollutants, and reduce petroleum use (what is nowadays also known as "biofuels" and has been generating an intense debate regarding the human beings' necessity of new sources of energy, on the one hand, and the need to maintain, in regions such as Latin America, the food habits and culture which has been the essence of civilizations such as the one originated in Mesoamerica; the entry, January 2008, of maize among the commercial agreements of NAFTA has increased this debate, considering the bad labor conditions of workers in the fields, and mainly the fact that NAFTA "opened the doors to the import of maize from the United States, where the farmers who grow it receive multi-million dollar subsidies and other government supports. (...) According to OXFAM UK, after NAFTA went into effect, the price of maize in Mexico fell 70% between 1994 and 2001. The number of farm jobs dropped as well: from 8.1 million in 1993 to 6.8 million in 2002. Many of those who found themselves without work were small-scale maize growers.").[28] However, introduction in the northern latitudes of the U.S. of tropical maize for biofuels, and not for human or animal consumption, may potentially alleviate this.

As a result of the U.S. federal government announcing its production target of 35 billion gallons of biofuels by 2017, ethanol production will grow to 7 billion gallons by 2010, up from 4.5 billion in 2006, boosting ethanol's share of maize demand in the U.S. from 22.6 percent to 36.1 percent.[29]

Ornamental and other uses

Some forms of the plant are occasionally grown for ornamental use in the garden. For this purpose, variegated and colored leaf forms as well as those with colorful ears are used. Additionally, size-superlative varieties, having reached 31 ft (9.4 m) tall, or with ears 24 inches (60.96 cm) long, have been popular for at least a century.[30][31]

Corncobs can be hollowed out and treated to make inexpensive smoking pipes, first manufactured in the United States in 1869.

An unusual use for maize is to create a corn maze (or maize maze) as a tourist attraction. The idea of a maize maze was introduced by Adrian Fisher, one of the most prolific designers of modern mazes, with The American Maze Company who created a maze in Pennsylvania in 1993. Traditional mazes are most commonly grown using yew hedges, but these take several years to mature. The rapid growth of a field of maize allows a maze to be laid out using GPS at the start of a growing season and for the maize to grow tall enough to obstruct a visitor's line of sight by the start of the summer. In Canada and the U.S., these are popular in many farming communities.

Maize kernels can be used in place of sand in a sandbox-like enclosure for children's play.[32]
Further information: Corn construction

Fodder

Maize makes a greater quantity of epigeous mass than other cereal plants, so can be used for fodder. Digestibility and palatability are higher when ensiled and fermented, rather than dried.

Maize as a commodity

Maize as a commodity is bought and sold by investors and price speculators as a tradable commodity. It is referred to as a corn futures contract. Corn futures contracts are traded on the Chicago Board of Trade (CBOT) under ticker symbol C. They are delivered every year in March, May, July, September, and December.[33]

U.S. Usage Breakdown

The breakdown of usage of the 12.1 billion bushel 2008 U.S. corn crop was as follows, according to the World Agricultural Supply and Demand Estimates Report by the USDA.[34]

* 5.25 billion bu. - Livestock feed
* 3.65 billion bu. - Ethanol production
* 1.85 billion bu. - Exports
* 943 million bu. - Production of Starch, Corn Oil, Sweeteners (HFCS,etc.)
* 327 million bu. - Human consumption - grits, corn flower, corn meal, beverage alcohol

In art

Maize has been an essential crop in the Andes since the pre-Columbian Era. The Moche culture from Northern Peru made ceramics from earth, water, and fire. This pottery was a sacred substance, formed in significant shapes and used to represent important themes. Maize represented anthropomorphically as well as naturally.[35]

In the United States, maize itself is sometimes used for temporary architectural detailing when the intent is to celebrate local agricultural productivity and culture. A well-known example of this use is the Corn Palace in Mitchell, South Dakota, which utilizes cobs of colored maize to implement a design that is recycled annually.

A corn stalk with two ripe cobs is depicted on the reverse of the Croatian 1 lipa coin, minted since 1993.[36]

Notes and references

1. ^ http://www.gmo-compass.org/eng/grocery_shopping/crops/18.genetically_modified_maize_eu.html
2. ^ Sources: E. Lewis Sturtevant, 1894 Bulletin of the Torrey Botanical Club, Vol.21, Lancaster, PA August 20, No.8 Notes On Maize, page 1.
3. ^ "Maize". The Oxford English Dictionary, online edition. December 2007. Accessed December 16, 2007.[1]
4. ^ OED, "Corn", II, 3
5. ^ "Corn". The Oxford English Dictionary, online edition. 1989. Accessed December 16, 2007.[2]
6. ^ The growers industry body for the crop in Australia is the Maize Association of Australia, for example, and "maize" is used by government agricultural bodies and research institutes such as the CSIRO. This usage is replicated among the English-speaking countries of Africa. For example, Kenya has the Kenya Maize Consortium and Maize Breeders Network, Nigeria the National Maize Association of Nigeria, Zimbabwe the Zimbabwe Seed Maize Association, and South Africa the Maize Board, until its dissolution in the 1990s. Agricultural and farmers' federations in Burundi, Uganda, Botswana, Ghana etc all call it "maize", as do relevant industry bodies in the UK. In India, there is the Indian Maize Development Association. It is usually if not preferentially called 'maize' in FAO and other international agricultural organizations.
7. ^ http://dictionary.reference.com/browse/mielie
8. ^ Sources: Coligado 1975, Salamini 1985, Poethig 1994, Paliwal 2000.
9. ^ P.V.Nelson 1985.
10. ^ Tropical Maize for Biofuels
11. ^ "Corn Stalk Lodging". Monsanto Imagine. 2008-10-02. http://www.dekalb.ca/content/pdf/corn_stalk_lodging.pdf. Retrieved 2009-02-23.
12. ^ "The origins of maize: the puzzle of pellagra". EUFIC > Nutrition > Understanding Food. The European Food Information Council. December 2001. http://www.eufic.org/web/article.asp?cust=1&lng=en&sid=4&did=16&artid=103. Retrieved September 14, 2006.
13. ^ Corn (maize) Allergy, InformAll Database, http://foodallergens.ifr.ac.uk/food.lasso?selected_food=33#summary, 18 October 2006
14. ^ Brown, David (2009-11-20). "Scientists have high hopes for corn genome". Washington Post. http://www.washingtonpost.com/wp-dyn/content/article/2009/11/19/AR2009111903190.html.
15. ^ MaizeGDB
16. ^ Researchers sequence genome of maize, a key crop
17. ^ The B73 Maize Genome: Complexity, Diversity, and Dynamics (Abstract)
18. ^ Ordish, George; Hyams, Edward (1996). The last of the Incas: the rise and fall of an American empire. New York: Barnes & Noble. p. 26. ISBN 0-88029-595-3.
19. ^ "Wild grass became maize crop more than 8,700 years ago", National Science Foundation, News Release at Eurekalert March 24, 2009
20. ^ http://www.srs.fs.usda.gov/pubs/ja/ja_peacock001.pdf
21. ^ (calculated from 185 bushels per acre at USDA 25.4 kg per bushel) "Iowa corn crop poised to set record". Cedar Rapids Gazette 12 August 2009 http://gazetteonline.com/top-story/2009/08/12/iowa-corn-crop-poised-to-set-record
22. ^ Duvick, D. N. & Cassman, K. G. (1999). "Post-green-revolution trends in yield potential of temperate maize in the north-central United States". Crop Science 39: 1622–1630. http://crop.scijournals.org/cgi/content/abstract/39/6/1622.
23. ^ http://www.gmo-compass.org/eng/grocery_shopping/crops/18.genetically_modified_maize_eu.html
24. ^ Solon Robinson. Hot Corn: Life Scenes in New York Illustrated (Series appearing in 1853 in the NY Tribune, later as a book)
25. ^ Liggett, R. Winston; Koffler, H. (December 1948). "Corn steep liquor in microbiology". Bacteriol Rev. 12 (4): pp. 297–311.
26. ^ Christian Science Monitor
27. ^ Iowa Renewable Fuels Association
28. ^ Revista Envío - Are Free Trade Agreements Free? Are They Development Strategies?
29. ^ IBISWorld
30. ^ http://www.angelfire.com/un/giantcrops/maize.html
31. ^ Sources: Eve. J. Wash. IA 1946, Kempton 1924.
32. ^ "Maize Quest Fun Park: Corn Box". http://www.mazefunpark.com/attractions/details.php?attraction_id=5. Retrieved October 8, 2007.
33. ^ CBOT Corn Futures Contract Overview via Wikinvest
34. ^ http://www.iowacorn.org/User/Docs/2009%20US%20Corn%20Stats.pdf
35. ^ Berrin, Katherine & Larco Museum. The Spirit of Ancient Peru:Treasures from the Museo Arqueológico Rafael Larco Herrera. New York: Thames and Hudson, 1997.
36. ^ Croatian National Bank. Kuna and Lipa, Coins of Croatia: 1 Lipa Coin. – Retrieved on 31 March 2009.

* Aureliano Brandolni, Andrea Brandolini. Il mais in Italia: storia naturale e agricola XII+370 pages and 80 colour pages. CRF press. Bergamo, Italy. [3] 2006
* Ferro, D.N. and Weber, D.C. Managing Sweet Corn Pests in Massachusetts
* ITIS 42268 as of 22 September 2002
* A list of Zea taxonomic names This list is of historical interest to taxonomists. It is largely of no practical use because many or most are based on single-gene mutations and if completed would be thousands of entries long. Modern classifications are available that are of great utility.