maize

While some maize varieties grow 7 m (23 ft) tall at certain locations, commercial maize has been bred for a height of 2.5 m (8 ft).

Maize physiology

The stems superficially resemble bamboo canes and the joints (nodes) are about 20–30 cm (8–12 in) apart. Maize has a very distinct growth form, the lower leaves being like broad flags, 50–100 cm long and 5–10 cm wide (2–4 ft by 2–4 in); Maize planted individually develops 2 to 4 ears. Certain varieties of maize have been bred to produce additional developed ears, and these are the source of the "baby corn" that is used as a vegetable in Asian cuisine.

Maize cultivars grown in the temperate zone are considered day-neutral and flower after a certain number of days at > However, maize cultivars from tropical locations typically have a short-day requirement for flowering and generally do not produce seed in the long summer days at higher latitudes. Each silk may become pollinated to produce one kernel of corn. When ground into flour, maize yields more flour, with much less bran, than wheat does.

Immature maize shoots accumulate a powerful antibiotic substance, DIMBOA (2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one). A maize mutant (bx) lacking DIMBOA is highly susceptible to attack 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.

Genetics

Many forms of maize are used for food, once classified as various subspecies:

Maize has 10 chromosomes (n=10). Some of the maize chromosomes have what are known as "chromosomal knobs". Individual knobs are polymorphic among strains of both maize and teosinte.

There is a stock center of maize mutants, 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. 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.

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 maize genome. (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:

The domestication of maize is of particular interest to researchers—archaeologists, geneticists, ethnobotanists, geographers, etc. Recent genetic evidence suggests that maize domestication occurred 9000 years ago in central Mexico, perhaps in the highlands between Oaxaca and Jalisco. The wild teosinte most similar to modern maize grows in the area of the Balsas River. Archaeological remains of early maize cobs, found at Guila Naquitz Cave in the Oaxaca Valley, date back roughly 6,250 years (corrected; 1100 BC when great changes appeared in cobs 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. Maize was the staple food, or a major staple, of most the pre-Columbian North American, Mesoamerican, South American, and Caribbean cultures. During the 1st millennium CE (AD), maize cultivation spread from Mexico into the U.S. Southwest and a millennium later into northeastern U.S. and southeast Canada, transforming the landscape as Native Americans cleared large forest and grassland areas for the new crop. Gavin Menzies, in his book 1421 - The Year China Discovered the World, claims to show that Maize was most likely transplanted from the Americas by the Chinese during their great voyages of the 15th century (although this claim is widely disputed ). 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 the southeastern United States contributed to the decline of freshwater mussels, which are very sensitive to environmental changes.

Cultivation

Maize is widely cultivated throughout the world, and a greater weight of maize is produced each year than any other grain. In 2004, close to 33 million hectares of maize were planted worldwide, with a production value of more than $23 billion.

Because it is cold-intolerant, in the temperate zones maize must be planted in the spring. As a C4 plant (a plant that uses C4 photosynthesis), maize is a considerably more water-efficient crop than C3 plants 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. Maize used for silage is harvested while the plant is green and the fruit immature. Field corn 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: beans used the corn plant for support, and squashes provided ground cover to stop weeds. Modern technique plants maize in rows which allows for cultivation while the plant is young. Nearly all maize cultivars grown in the United States and Canada are hybrids.

Before about World War II, most maize was harvested by hand. Some modern farms store maize in this manner and later shell it for sale in the off-season to capture better prices. The combine with a corn head (with points and snap rolls instead of a reel) cuts the stalk near the base and then separates the ear of corn from the stalk so that only the ear and husk enter the machinery.

Pellagra

When maize was first introduced outside of the Americas it was typically welcomed enthusiastically by farmers everywhere for its productivity. However, a widespread problem of malnutrition soon arose wherever maize was introduced.

It was eventually discovered that the indigenous Americans learned long ago to add alkali---in the form of ashes among North Americans and lime (calcium carbonate) among Mesoamericans---to corn meal to liberate the B-vitamin niacin, the lack of which was the underlying cause of the condition known as pellagra.

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. Nixtamalization was also found to increase the lysine and tryptophan content of maize 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 elsewhere was often tragic. The development of high lysine maize and the promotion of a more balanced diet has also contributed to its demise.

Pests of maize

Insect pests

The susceptibility of maize to the European corn borer, and the resulting large crop losses, led to the development of transgenic expressing the Bacillus thuringiensis toxin. Maize Dwarf Mosaic Virus Stewart's Wilt (Pantoea stewartii) Common Rust (Puccinia sorghi) Goss's Wilt (Clavibacter michiganese) Grey Leaf Spot Mal de Río Cuarto Virus (MRCV)

Uses for maize

In the United States and Canada, the primary use for maize is as a feed for livestock, forage, silage or grain. Grain alcohol from maize is traditionally the source of bourbon whiskey.

Maize can also be prepared as hominy, in which the kernels are bleached with lye; Another common food made from maize is corn flakes. The floury meal of maize (cornmeal or masa) is used to make cornbread and Mexican tortillas. Maize is relatively cheap and home-heating furnaces have been developed which use maize kernels as a fuel.

An unusual use for maize is to create a Maize Maze as a tourist attraction. This is a maze cut into a field of maize. The idea of a Maize Maze was introduced by Adrian Fisher, one of the most prolific designer of modern mazes, with The American Maze Company who created a maze in Pennsylvania in 1993. 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 1983, Barbara McClintock received the Nobel Prize in Physiology or Medicine for discovery of transposons while studying maize. Maize is still an important model organism for genetics and developmental biology today.

Maize is sometimes used as a biomass fuel, such as ethanol .

Maize is also used as fish bait.

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