Corn

I

Introduction

Corn or Maize, common name for the cereal grass widely grown for food and livestock fodder. Corn ranks with wheat and rice as one of the world’s chief grain crops, and it is the largest crop of the United States (see Crop Farming).

II

Description

The corn plant has an erect, solid stem, rather than the hollow one of most other grasses. It varies widely in height, some dwarf varieties being little more than 60 cm (2 ft) at maturity, whereas other types may reach heights of 6 m (20 ft) or more. The average is 2.4 m (8 ft). The leaves, which grow alternately, are long and narrow. The main stalk terminates in a staminate (male) inflorescence, or tassel. The tassel is made up of many small flowers termed spikelets, and each spikelet bears three small anthers, which produce the pollen grains, or male gametes. The pistillate (female) inflorescence or ear is a unique structure with up to 1,000 seeds borne on a hard core called the cob. The ear is enclosed in modified leaves called husks. The individual silk fibers that protrude from the tip of the ear are the elongated styles, each attached to an individual ovary. Pollen from the tassels is carried by the wind and falls onto the silks, where it germinates and grows down through the silk until it reaches the ovary. Each fertilized ovary grows and develops into a kernel.

III

History

Corn is native to the Americas and was the staple grain of the region for many centuries before Europeans reached the New World. The origin of corn remains a mystery. Conclusive evidence exists, from archaeological and paleobotanical discoveries, that cultivated corn has existed in the southwestern United States for at least 3,000 years. Wild corn was once thought to have existed in the Tehuacán Valley of southern Mexico 7,000 years ago. More recent evidence puts the appearance of corn in that region at a much later date, about 4,600 years ago. Early wild corn was not much different in fundamental botanical characteristics from the modern corn plant.

IV

Varieties

The many varieties of corn show widely differing characteristics. Some varieties mature in 2 months; others take as long as 11 months. The foliage varies in intensity of color from light to dark green, and it may be modified by brown, red, or purple pigments. Mature ears vary in length from less than 7.5 cm (3 in) to as much as 50 cm (20 in). The number of rows of kernels ranges from 8 to 36 or more. Six general groups of varieties are differentiated by the characteristics of the kernel. Dent corn is the leading type of corn grown on U.S. farms. The sides of the kernel consist of hard, so-called horny starch, and the crown contains soft starch. As the grain matures, this soft starch shrinks, forming the characteristic dent.

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In flint corn, the horny starch extends over the top of the kernel, so that there is no denting. Some varieties of flint corn, which are used for the same purposes as dent corn, are favored in cold climates because of their ability to germinate at low temperatures, or in tropical climates because of their resistance to attack by weevils. Popcorn is a light, highly popular snack throughout the United States, a variant of flint corn with small kernels of great hardness. When heated, the moisture in the kernels expands, causing the kernels to pop open.

Flour corn contains a preponderance of soft or less densely packed starch, and it is readily ground into meal. It is grown extensively in the Andean regions of South America that were part of the Inca Empire. Sweet corn is the type commonly grown in the United States for human consumption as a vegetable. The sugar produced by the sweet-corn plant is not converted to starch during growth, as it is in other types. The seeds are characteristically wrinkled when the plant is allowed to mature. Pod corn is seldom used as food but is often grown as a decorative plant; each kernel is enclosed in its own set of diminutive husks. Another decorative corn, commonly called Indian corn, consists of multicolored varieties of flour and flint types.

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