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Corn (Maize)

According to Native American legends of the American Southwest, the Indian people have occupied four (some say five) worlds since the creation of man. The present world is the fourth world and each of the three former worlds lies under the one succeeding it. Some legends say that maize, or corn as Europeans came to call it, was already present in the first world, at the time the first humans were created. The first people are said to have relied on maize for nourishment, and to have thought of the corn plant as a second mother (the first mother being the Earth Mother). Whenever a child was born, custom required that the Corn Mother—a perfect ear of corn with a tip ending in four full kernels—be placed beside the child, where it would remain for 20 days. The Corn Mother was also present at the naming of the child, and remained the child's spiritual mother for the rest of her or his life.

These myths attest to the profound importance of corn for many of the native peoples of the Americas, where corn originated—an importance comparable to that of rice for the peoples of Southeast Asia or of potatoes for the ancient peoples of the Andes Mountains in South America. Today corn is an important crop worldwide, but some rural Native American and Latin American farmers—especially in the highlands of Mexico and Guatemala—still have a special relationship to corn. Hundreds of genetically distinct varieties of corn are cultivated by small farmers in that region. The industrialized world relies on a few, genetically similar varieties of corn planted in very large, uniform fields, which renders its corn crop more vulnerable to weather changes and to blights (such as the virus that destroyed 15% of the U.S. corn crop in 1970); the genetic diversity preserved by the small, rural farmers of Central America is thus a unique asset, the "world's insurance policy," according to the International Maize and Wheat Improvement Center.

Science debates the origin of corn, species name Zea mays. Although some paleobotanists believe that corn developed from a grass known as teosinte in the vicinity of the Tehuacan Valley of Mexico more than 5,000 years ago, most believe that teosinte was itself an offshoot of a wild corn and another species of grass. Other discoveries suggest that corn did not develop in Mexico at all, arguing instead for a South American origin. The prevalent botanical theory today is that corn was domesticated from a wild, now-extinct, corn-like plant. Analyses of what appears to be wild-corn pollen found about 200 ft (60 m) below modern Mexico City have led some paleobotanists to conclude that the pollen came from an extinct wild corn that existed 25,000–80,000 years ago.

The corn plant is uniquely adapted for high productivity for two reasons: it has a very large leaf area, and it has a modified photosynthetic pathway that allows it to survive extended periods of drought. Known as the C4 syndrome, the modified pathway for photosynthesis provides a highly efficient way for the plant to exchange water vapor for atmospheric carbon dioxide.

At a biochemical level, carbon dioxide is converted into a molecule containing four carbon atoms in C4 photosynthesis, whereas in conventional photosynthesis carbon dioxide is converted into a molecule containing three carbon atoms (C3 photosynthesis). Thus C4 photosynthesis permits the corn plant to make more efficient use of carbon dioxide to build the carbon compounds needed to sustain plant growth than can be made by conventional plants. As a result, the corn plant can produce more dry matter (i.e., various combinations of carbohydrates, proteins, oils, and mineral nutrients) per unit of water transpired (released to the atmosphere) than can plants endowed with the conventional C3 photosynthetic pathway. The amount of grain produced by the plant depends upon the rate and length of time of this dry matter accumulation.

Successful cultivation of corn requires proper fertilization during the early stages of corn plant growth. The final size of the leaves, ear, and other plant parts depends largely upon maintaining an adequate supply of nutrients to the plant, especially during this time. Regionally adapted hybrids can be selected to accommodate local growing seasons and particular needs, and to make efficient use of specific types of land. Planting time should be carefully gauged. The highest yields are obtained only where environmental Corn piled high outside of grain elevators, Magnolia, MN. Photograph by Jim Mone. AP/Wide World Photos. Reproduced by permission. conditions are most favorable to growth. Weeds, diseases, and insects all reduce crop yield.

In recent years, genetically engineered (GE) varieties of corn have swiftly become a major fraction of the U.S. corn crop. In 2002, 34% of the corn grown in the United States (most of which was grown for the manufacture of corn syrup for human consumption) was genetically engineered. The most common variety of GE corn is Bt corn, a product of the Monsanto Corporation. Bt corn resists the corn borer, a common insect pest, by producing insecticide in its own tissues. Critics are concerned that Bt-corn-produced insecticide may linger in soil and sediments, threatening nontarget insect populations, and that genes from GE corn may contaminate non-GE varieties with unpredictable consequences. The discovery in 2001 that genes from GE corn (transgenes) had in only a few years' time managed to insinuate themselves into traditional maize varieties in Mexico has enhanced global concern about GE corn and other GE crops. The European Union and Zambia have both refused to accept the importation of GE corn from the United States because of concerns that the genetic changes made to the corn may produce unforeseen health effects. Many scientists argue that such concerns are unfounded, and that the benefits of genetic engineering outweigh the risks; others argue that the risks are too high, and that yields for genetically modified crops have not actually been greater than for traditional varieties.

Many historians believe that the course of American history was shaped more by corn than by any other plant. Their argument derives largely from the observation that for more than 250 years after the settlement of Jamestown, Virginia in 1607, corn remained the staple crop of about 90% of all European-American farmers. Not until 1979 did soybeans surpass corn as the United States' most important crop, and then only temporarily. Currently, more bushels of corn are produced in the United States each year than of any other grain crop. (One bushel = 35.24 L.)

Corn is grown on every continent except Antarctica. This is possible because scientists have developed diverse hybrid varieties of corn that suit growing conditions and locations worldwide. In 1999, the United States led the world in corn production, with a crop valued at 9,437 million bushels. In second place was China with a crop value of 5,039 million bushels, followed by European countries with a crop valued at 1,457 million bushels.

Although U.S. citizens today eat much less corn than they did historically, large amounts of corn are consumed indirectly in the form of products derived from livestock fed a diet rich in corn, including beef, pork, poultry, eggs, milk, and many other food products. Eighty percent of the U.S. corn crop is fed to livestock. As a point of reference, one bushel of corn—56 lb (25 kg)—produces approximately 5.6 lb (2.5 kg) of beef.

Corn is still used for many traditional purposes (e.g., meal, corn on the cob, corn-cob pipes). However, new markets have developed for corn byproducts, including the manufacture of fiberboard panels, nylon products, furfural (used in plastics and solvents), and ethanol as a renewable vehicular fuel. In fact, more than 3,500 different uses have been found for corn products. Some of the more innovative uses include a basis for vitamins and amino acids; a substitute for phosphate for cleaning; a packing-peanut material; an ink base to replace petroleum ink bases; and an absorbent material for diapers and for automobile fuel filters.



Associated Press. "Zambia Bars Altered Corn From U.S." New York Times August 18, 2002.

Dalton, Rex. "Transgenic Corn Found Growing in Mexico." Nature 413 (September 27, 2001): 337.


International Maize and Wheat Improvement Center (CIMMYT). Apartado #370, PO Box 60326, Houston, TX 77205. (650) 833 6655 (in U.S.). <http://www.cimmyt.org/> (cited May 25, 2003).

Randall Frost

Larry Gilman

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Science EncyclopediaScience & Philosophy: Condensation to Cosh