Zea mays

Zea mays. It is a large annual grass domesticated by indigenous peoples in Mesoamerica in prehistoric times. The plant has a stout, solid stem and produces large, separate inflorescences for pollen and seed. Its cultivation and subsequent global spread following the Columbian Exchange has made it one of the world's most crucial cereal crops.

Description and morphology

The plant typically grows to heights between 2 and 3 meters, supported by a distinctive, unbranched culm with prominent nodes. The leaves are long and broad, with a prominent midvein and a characteristic ligule at the junction with the stem. The reproductive structures are monoecious, with the male inflorescence, or tassel, borne at the apex of the stem, producing copious amounts of pollen. The female inflorescences, or ears, develop from axillary buds mid-stem and are enveloped by modified leaves called husks; each ear consists of a cob from which rows of ovules develop into kernels upon fertilization from wind-blown pollen captured by the silks.

Taxonomy and evolution

The species was formally described and named by Carl Linnaeus in his seminal work Species Plantarum. It belongs to the tribe Andropogoneae within the grass family Poaceae, and its closest wild relative is the Mexican teosinte (*Zea mays* ssp. *parviglumis*). The dramatic morphological evolution from the small-seeded, multi-branched teosinte to the modern plant is a classic study in plant genetics and domestication syndrome, largely controlled by a small number of key genetic loci, such as *teosinte branched1*. Research led by scientists like George Beadle and more recently by teams at institutions like the International Maize and Wheat Improvement Center has elucidated this profound evolutionary transition.

Cultivation and uses

As a C4 plant, it is highly efficient in warm, sunny climates and is cultivated from the American Midwest and the North China Plain to the Pampas of Argentina. Major producers include the United States, China, and Brazil. Beyond direct human consumption as a vegetable (sweet corn) or ground into flour (e.g., masa for tortillas), a vast proportion of the global harvest is used for livestock feed and industrial products. These include high-fructose corn syrup, bioethanol (prominently in programs like the U.S. Renewable Fuel Standard), starch, and bioplastics.

Genetics and breeding

It has a large and complex genome, approximately 2.3 gigabases in size, which was fully sequenced through a collaborative effort involving the Maize Genetics Cooperation Stock Center and published in the journal *Nature*. Traditional selective breeding over millennia established the major cultivar groups like flint, dent, and popcorn. The 20th century saw the revolutionary adoption of hybrid varieties, pioneered by researchers such as George H. Shull, which dramatically increased yields. Modern breeding incorporates techniques like marker-assisted selection and genetic engineering, with traits such as insect resistance (from *Bacillus thuringiensis*) and herbicide tolerance being widespread in countries like the United States and Argentina.

Economic and cultural importance

It is a cornerstone of global agriculture, with annual production exceeding one billion metric tonnes, making it the highest-production cereal worldwide. Its price and supply are critical to global commodity markets, traded on exchanges like the Chicago Board of Trade. Culturally, it holds profound significance as a staple food across the Americas; it is central to the cuisine and mythology of civilizations from the Maya and Aztecs to modern Hopi and other Pueblo peoples. Its image is deeply embedded in the art and society of the United States, symbolized by the vast Corn Belt and celebrated in festivals like the Iowa State Fair. Internationally, organizations like the Food and Agriculture Organization monitor its role in global food security.

Category:Poaceae Category:Cereals Category:Crops originating from the Americas