Fanciful the thought might seem, but America will not make it through the rest of this day without corn.

We have nothing else like corn. Not oil. Not gold or uranium. Not wheat or soybeans. Not our assembly lines or our high technology. Corn is our major foodstuff and our major agricultural export. It finds its way into thousands of common industrial products.

Unknown to most Americans, corn has insinuated itself so throughly into food and industrial processes that we would be hard put to go on without it.

Across the nation, but principally in the rich black earth of the Midwest, the seeds are growing on millions of acres, soon to become a bounteous harvest that is the American equivalent of the petroleum wealth of the Persian Gulf. Not even that is an adequate description.

This is not the sweet corn that we eat off the cob, creamed or in kernels. It is field corn: dent corn to the farmer, zea mays to the botanist, maize to the stroybook Indian. It is far more than a staple of the American diet, converted as it is to meat, milk, eggs, meal, starch and sweetners.

Corn had become a great industrial generator, providing the basic ingreidient of innumerable products and stimulating invention and ingenuity in the research laboratories. Beyond that, it will go abroad, bringing $7 billion or more in return, money that helps pay for the oil, the autos, the stereos and other geegaws we cherish.

Other crops -- wheat, for example -- may be more prestigious. But corn is quintessentially American, through our history by romance and legend. Every schoolchild knows how the Spaniard found maize in the New World, how the pre-Columbian natives feified it, how the American pioneer thrived on it. We traded corn, lived off it, boozed with it, embellished out language with it.

But that glorified past doesn't begin to reflect the bread-and-butter side of the humble kernal of corn. A more revealing way to look at corn is to parse its place in daily living.

You wake up on sheets of cotton, wearing pajamas of flannel, both woven with corn starch for sizing. You turn on the transistor radio -- the dry cell batteries contain corn starch. You put on shoes with leather tanned from the lactic acid of corn. Out of bed, you bump into the door and the wall. The plywood and the wallboard contain corn starch. Your bath powder contains corn; your cosmetics, a corn ingredient.

Breakfast begins with corn flakes. The milk came from a cow fed with corn; the eggs, fried in corn oil, from a chicken who got her energy from corn. The pig that became the sausage and bacon grew up on corn. The English muffin is rolled in corn meal. You spread it with margarine, made from pure corn oil, or butter from that corn-fed cow, then smear it with corn-sweetened jelly.

Your car may be driven by gasohol, made from corn distilled to alcohol. Your midmorning soft drink is sweetened with a powerful corn syrup, colored by a caramel from the corn and carbonated by the carbon dioxide from the corn distilling process. The penicillian your taking for that infection is made possible by another corn distillery byproduct.

Lunch is a hamburger, from a cornfed steer. The bun has a wheat base, but it contains corn syrup. The potato chips were fried in corn oil. Dessert is a pie a la mode, with a filling thickened with corn starch and an ice cream topping made with the corn-fed cow's milk. Both filling and the ice cream are sweetened with corn syrup.

At midafternoon, you mail a birthday card to mother. The card was treated with a corn derivative to hold the ink, the stamp and the envelope have a glue made from corn.

For dinner, you don a clean shirt or dress, gently stiffened with corn starch. The cocktail began in a cornfield -- the bourbon is distilled from corn mash, and the mix that made it a whiskey sour is sweetened with corn sugar and blended with a dextrin from the corn.

You dine on ham (from the corn fed hog), sweet potatoes (candied with corn syrup), sweet corn, cornbread (from cornmeal) and salad doused with dressing that flows easier because of a gum extracted from corn. The beer and wine contain corn ingredients. Dessert turns out to be an imitation tapioca, made from corn starch, sweetened with corn syrup, blended with milk and eggs.

Impressive as this inventory might be, it only begins to describe the place of field corn in the American economy.

U.S. Department of Agriculture economists calculate that last year's drought-stricken harvest from 73 million acres was about 6.6 billion bushels of corn. It will be used in two principal ways: 4.1 billion bushels fed to livestock; 2.5 billion to be exported.

About 750 million bushels will be used for human food and for seed and industrial purposes. That corn is available from the reserve of around 1.6 billion bushels left over from the record 1979 crop and a tiny flow of imports.

These numbers keep changing, but the wet-milling industry that makes starch, sweetners, alcohol and animal feed will use about two-thirds of the 750 million bushels. The rest will go to ethyl alcohol (for gasohol), for seed, for flour, meal, grits, flakes; for pet foods, beer and distilled spirits.

The largest overall use of corn, obviously, is for food. The American farmer markets his corn through the meat, eggs and milk he produces. That is, admittedly, not the most efficent use of the grain, for experts say it takes roughly about eight times more corn to produce food this way than the average American might eat by eating the grain directly.

But the adundance of corn and the farmer's steadily rising productivity, made possible by hybrid seed and development and more sophisticated farming techniques, have mooted questions of best-use for the time being.

The center of this prodigious harvest in the Corn Belt, composed of six midwestern states, Iowa, Illinois, Minnesota, Nebraska, Indiana and Ohio, which last year grew about 4.8 billion bushels, or roughly 72 percent of all the nation's corn. Iowa, with 1.46 billion bushels, and Illinois, with 1.06 billion, were far and away the leaders, together outproducing all other major corn-growing countries in the world.

Once that grain leaves the farm, an impressive ripple effect begins, spilling all across American economy in ways seldom perceived. The USDA estimates that 20 percent of all the country's jobs are related to agriculture, which means that corn, as the principal crop, plays a vital role in turning over the dollar.

For every farmer, there is a machinery plant, a truck factory, a fertilizer and pesticide industry, a trading company, a researcher, a seed producer, a railroad, a barge line, an exporter, a miller, a slaughterhouse, a processor and packager of foods who depend on the farmer's success in the field.

There is no reliable dollar figure to quantify the place of corn in that panorama of commerce and industry, but suffice to call it in the multibillions. p

Without wanting to appear too melodramatic about his place in this scheme of things, William (Bill) Fugate, an Illinois farmer who grows corn to feed his hogs, put it this way: "If the farmer doesn't have money to buy a combine or a car, somebody else cannot assemble it. Agriculture really is the backbone of our economy . . . . Everybody wants to eat."

Yet while Americans continue the high-protein diet that Fugate and his corn help make possible, and which other nations try to emulate by buying U.S. grain in massive amounts, a quest goes on for a better, higher-yielding corn and more ways to use it.

Just as the corn spreads its wealth through the economy, it generates scientific inquiry and stimulates processors into wondrous flights of technological fancy. Each new process leads to two more, and the future possibilities seem infinite.

The Archer-Daniels-Midland Co. at Decatur, Ill., for instance, the country's major producer of alcohol from corn, has found a way to utilize the heat and excess carbon dioxide from its corn-refining operations.

The carbon dioxide from its alcohol fermentation is captured, processed and sold -- 200 tons of it a day -- for the fizz in soft drinks, for fire extinguishers, for fast-freezing of food. Waste heat is channeled into two half-acre experimental greenhouses, where garden vegetables are grown hydroponically and sold in local supermarkets. ADM foresees hugh potential for commerical hydroponics, using the waste heat and carbon dioxide to stimulate plant growth.

Not far away, at the USDA's northern Regional Research Center at Peoria, scientists have made formidable discoveries by probing deeper into the potential of corn.

The Peoria researchers discovered xanthan gum in the corn, which is now used widely in processed foods and by dozens of industries to make paint pigments, ceramic glazes, insecticides and herbicides, cosemetics and fire retardants. They found a way to convert corncobs into low-grade methane gas for drying grains, a major expense for farmers using petroleum products.

But the basic corn component they are exploring is the starch, which USDA scientists like Dr. William M. Doane say one day could help pry America away from its dependence on petroleum. "We think we have just scratched the surface of new technologies with starch," Doane said.

The array is impressive already: urethane plastics, for example, as well as a biodegradable plastic film for packaging that replaces plastics derived from petroleum, and a product called Super Slurper, a dust that can absorb 2,000 times its weight in water.

The implications of Super Slurper, now marketed in body powder, adult diapers, seed coatings to induce germination and as a moisture-holder for household and large-scale agricultural plants, are enormous. For example, a typical Corn Belt farmer plants 25,000 costly hybrid corn seeds to get roughly 18,000 seedlings. Treated with the moisture-attracting dust, that same planting may produce 24,000 seedlings, Doane said, boosting yield and cutting production costs.

"It creates a water reservoir," Doane explained, "and it draws water to the seed. It could aid crops in dry areas and it has potential for truck gardens and transplanting. But this is just one product.We have not yet really tapped the potential of starch."

Peoria scientists now are looking at the natural polymers in corn starch as a replacement for the synthetic polyers that come from petroleum.

"We use 1 million barrels of oil or their natural gas equivalent per day to make synthetics," Doane said. "Starch can replace some of that. We grow a lot more starch than what we need for food or animal feed. Less than 2 percent of the U.S. corn crop goes into starch: 2 billion pounds into the paper industry, 1 billion to alcohol and half-a-billion into textiles . . . .

"Technologically, from plant materials we could make all the products we now make from petroleum. The cost still is not feasible, but we continue to search . . . ."

Which is a long way from the traditional notion of corn as a mainstay of the American pantry. But then, maybe it isn't at all.