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Making the plant/soil/nutrition connection.

Making the Plant/Soil/Nutrition Connection

Even though a pound of chuck roast sold for less than two bits and a pound of navy beans was barely more than a nickel, 1935 was a time when many Americans were malnourished.

Senator John Hollis Bankhead II joined forces with Representative John Marvin Jones of Texas to push passage of the Bankhead-Jones Act on June 29, 1935.

Among the provisions of this act was the establishment of nine regional agricultural research laboratories, including one at Ithaca, New York.

The Ithaca lab--the last of the nine to be funded--had a unique mission: to trace the nutritional connection between soils, plants, and animals. The idea was that improvements to the soils might send beneficial ripples all the way up the food chain.

Funding for what is now the U.S. Plant, Soil, and Nutrition Laboratory was approved by Agriculture Secretary Henry A. Wallace on January 31, 1939. By the end of July 1940, the lab was settled into its new home on Tower Road on the edge of the Cornell University campus, and the search for answers was on.

Today, as the lab completes its first half century, it has many scientific successes--and one Nobel Prize winner--to its credit.

And after 50 years, the lab is busier than ever, according to research leader Darrell R. Van Campen. "This actually may be the only lab of its kind in the world," he says.

The concept behind the founding of the Ithaca lab--the thought that soils could affect the plants that sprouted in them--was considered quite novel in the 1930's according to Kenneth C. Beeson. Now retired and living in Sun City, Arizona, Beeson was a research chemist for the U.S. Department of Agriculture in the late 1930's and went on to be laboratory director of the Ithaca facility from 1949 to 1960.

"In the 1930's, throughout the United States, more attention was being given to the nutritional quality of foods, with particular attention to nutrient elements such as calcium," Beeson recalls.

"A number of people in agricultural experiment stations were analyzing garden produce and finding, for example, that lettuce in Florida might have a different calcium content than lettuce grown in Mississippi."

Beeson's link with the Ithaca lab technically predates the lab itself. While working for USDA's old Bureau of Chemistry and Soils in Washington, D.C., Beeson was assigned in 1937 to begin reviewing world literature on the link between nutritional value of foods and the quality of the soil in which the food was grown.

By the fall of 1940, Beeson had moved to Ithaca to work under the direction of the lab's first research leader, Leonard A. Maynard. Maynard held the reins until 1945 but only served on a part-time basis; he was also director of Cornell University's School of Nutrition.

Across the span of dozens of years and research projects, Beeson still holds a vivid image from those early days in Ithaca.

"The first big project of the lab, by Karl C. Hamner and associates, was a study of fertilizer's effect on carotene content of tomatoes," Beeson says.

"In the spring of 1941, pots of sand covered the entire greenhouse area to test a wide range of fertilization on the tomato's levels of carotene and ascorbic acid. It was a beautiful sight--that big area with pots all growing tomatoes."

The pace was quick at the Ithaca facility. James T. Jardine, chief and director of research for USDA's Office of Experiment Stations, listed many accomplishments in the lab's first annual report, submitted to Agriculture Secretary Claude R. Wickard in October 1941.

Along with mentioning the "several thousand tomato plants," Jardine reported on how the lab, in cooperation with Cornell University, had already discovered that alfalfa grown on soil low in boron contained 20 percent less carotene than alfalfa grown on soils with abundant boron.

In addition, Jardine wrote, the lab had determined that vitamin [B.sub.1] content of food could be determined by a fungus assay that was much quicker than previous methods.

Karl C. Hamner--he of the thousands of tomato plants--succeeded Cornell's Maynard as laboratory director at the Ithaca lab in 1946 and served until 1948, when Beeson took the helm.

Beeson left Ithaca in 1960 to tackle an international research project in the Sudan. His successor as research leader was William H. Allaway, better known to many as "Hub," who served as lab leader until 1976.

Allaway, a veteran of USDA's old Bureau of Plant Industry, had joined the Agricultural Research Service in 1954, the year after ARS was established to administer USDA research.

As laboratory director at the Ithaca facility, Allaway oversaw addition of a wing to the lab, providing much-needed working space for the scientists. The addition was completed in 1963.

On board when Allaway arrived was one Robert Holley, already the co-discoverer of soluble ribonucleic acids (RNA) in protein synthesis.

"It was obvious Holley was on to something pretty important," Allaway says. Time proved Allaway right; in 1968 Holley won the Nobel Prize in Physiology and Medicine for determining the structure of one of the soluble ribonucleic acids, a building block of modern genetic engineering.

The work begun by Holley, now living in La Jolla, California, has been carried in a new direction by plant physiologist John F. Thompson and research chemist James T. Madison.

Madison had worked with Holley on the RNA research, and he and Thompson thought they could combine the knowledge gleaned from those days with newly developed genetic engineering techniques to improve the nutritional quality of plants.

When compared with animal proteins such as those in meat, milk, and eggs, the protein from soybeans and other legumes contains relatively low concentrations of the sulfur-containing amino acid methionine.

The ability of humans and nonruminant animals to utilize legume seed protein is limited by the concentration of sulfur amino acids in those seeds. Once all the sulfur amino acids have been used up, the remaining protein in the seeds is wasted.

Thompson and Madison have concentrated on boosting the amount of methionine in legume seeds, with some success. They have developed techniques that increase the amount of a specific "storage protein" in soybeans that is richer in methionine than other storage proteins, consequently increasing overall methionine content in the beans.

While their technique works well in the lab, it is not yet feasible for commercial soybean production. But the two scientists are now trying to develop a special gene that could be introduced directly into soybeans to increase their content of sulfur-amino acids--and, in turn, their nutritional quality.

Dietary concerns of a different sort occupied the research hours of "Hub" Allaway in his years at the Ithaca facility.

"Selenium toxicity had been a longstanding problem in grazing animals on the Great Plains and in the western United States," Allaway says.

"I worked on selenium research for 12 years. When I started, it was illegal to add it to animal feeds. Now that's routinely done. Our contribution was telling the Food and Drug Administration that by adding selenium to animal feeds in areas where selenium was deficient in the soil, you weren't doing anything that wasn't happening naturally through plants in areas where selenium was adequate in the soil."

Another high point in the history of the Ithaca lab was the production in the 1940's of a map showing the distribution of the mineral cobalt in the soils of the eastern United States.

"For example, there is an area of New Hampshire where the soil was formed from granitic rock, and it contains almost no cobalt," explains Darrell Van Campen, research leader at the Ithaca lab since 1979.

"In that area, grazing animals just didn't do well because of cobalt deficiencies. Cattle and sheep didn't grow well there, and they didn't reproduce well. Ruminant animals such as cows have bacteria in their rumens that use cobalt to make vitamin [B.sub.12], so they must have cobalt.

This lab didn't discover cobalt was an essential element; that came out of Australia in the mid-1930's. But Kenneth Beeson and his group suspected cobalt deficiencies might be the problem in the Northeast, so they went in and sampled the soil and came out with the map showing where it was deficient.

"Today, livestock producers in that area supplement their animals' feed with cobalt, and dairy cattle, beef cattle, and sheep do very well there."

The Ithaca lab has since produced similar maps showing the disposition in soil and forage of molybdenum, selenium, copper, and magnesium. Imbalances of these elements in a grazing animal's diet can cause severe health problems and sometimes death.

But the Ithaca lab is not content to rest on its laurels, say Van Campen.

"For example, one of our scientists, David L. Grunes, acts as a clearinghouse for information on an animal disease called grass tetany that is seen all over the United States. Grass tetany occurs if a grazing animal doesn't have enough magnesium in its diet; it gets sick and can die.

"Dave Grunes has done a lot of research himself on this subject since 1965, but he's also made a major contribution in getting people together and in organizing workshops and symposia on this subject."

Scientists' combined efforts against grass tetany have paid off in a highly visible way. Van Campen says, "Since 1965, there's been about an 80-percent reduction in the incidence of grass tetany through improved treatment and prevention techniques."

Animals Are What They Eat

Microbiologist James B. Russell has also focused part of his research on the animal diet.

"Cows eat grass and other forages because they can digest cellulose," says Russell. "They have bacteria in the rumen that have enzymes called cellulase, and cellulase can break down cellulose."

Since World War II, increasing levels of grain have been fed to beef and dairy cattle. The starch in grain is more digestible than cellulose, so digestion is faster and the cow can produce more meat or milk.

But a problem arose with the grain-laden diet. The rumen became too acidic for the bacteria that digest cellulose.

"We wanted to know if we could perhaps use genetic engineering to construct a bacterium that would digest cellulose under acid conditions in the rumen," Russell recalls.

Experiments have shown the answer may be "yes." Initially, Russell, ARS scientist Osamu Matsushita, and David B. Wilson of Cornell University planned to insert a cellulase gene into a rumen bacteria, Bacteroides ruminicola, that can grow in an acid environment but was thought to produce no cellulase.

However, the researchers found B. ruminicola did produce a cellulase, called CMCase, that could degrade synthetic soluble cellulose but not the native insoluble cellulose in forages.

Cellulases capable of degrading insoluble cellulose must have both an "active site" and a "binding site." The CMCase from B. ruminicola had no binding site.

The solution seems to lie in reconstructing the CMCase gene to include a DNA segment that codes for an appropriate binding site.

More than 18 months of experiments have gone into successfully cloning the entire CMCase gene into E. coli bacteria, then fusing the binding site from another bacterium's cellulase gene to the CMCase gene.

"This reconstructed gene does produce a cellulase, and we're currently studying the gene's activity," Russell says. Plans are to insert the reconstructed gene back into B. ruminicola and return it to the rumen.

Probing Plant Preferences

For plant physiologist Leon V. Kochian, another researcher at the Ithaca lab, the hot topic is the inner workings of plants, not animals. Kochian has used microelectrode probes only 20 millionths of an inch in diameter to explore individual plant cells' preferences in nutrients.

As the tip of the probe is pushed through the outer membrane of the plant cell, the membrane closes around the probe. The probe then allows the researchers to study the cell interior to see when a particular element, such as potassium, moves into or out of the cell.

"If we can learn more about how plant cells regulate the transport of nutrients, we might be able to manipulate the plant into absorbing more of a desirable nutrient, such as calcium," Kochian explains. "This could ultimately affect food quality."

Food quality concerns have also surfaced in Kochian's work with plant physiologist Ross M. Welch at Ithaca. The two are studying a pea plant that could someday play a key role in boosting the nutritional quality of the typical American diet.

The pea plant is a mutant that differs by only one gene from a commercial pea variety Sparkle. But the mutant, E107, behaves quite differently from Sparkle in one vital respect.

"Most plants will take up just as much iron as they need from the soil and then stop," says Welch. "But this mutant never stops taking up iron and will eventually accumulate enough to kill itself."

By studying what's happening in this self-destructive mutant, the scientists might be able to find a way to increase the amount of iron in the edible parts of crop plants. They're now trying to find out which gene is mutated and where the mutation is on that gene. Then they can study what that gene does in a normal plant.

Welch is also studying a mutant gene in corn that could affect nutritional quality of the grain. This gene, opaque-2, is responsible for making corn rich in lysine, an amino acid essential to the human diet.

"In looking at inbred corn that has opaque-2, we've found some that is 20 percent higher in iron content, and 35 percent higher in zinc, and has 25 percent more calcium, 18 percent more magnesium, and 87 percent more sulfur," Welch says.

"We know the improvements are there; now we want to know why."

Animal physiologist William A. House is tackling the equation from another direction, trying to ensure that when a nutrient such as iron is available in food, those who consume the food will derive the maximum benefit from it.

"Iron is essential so the blood can carry oxygen throughout the body," explains House. "But some Indian scientists have found that people drinking certain teas have impaired ability to absorb iron.

"The key appears to be tannins--compounds that you get from different foods. We're finding a lot of dry beans have tannins, and there's a big difference in the quantities. We've found several bean cultivars in which up to 1 percent of the bean weight is actually tannins."

House has conducted experiments in which rats were given iron that could be traced through their bodies, and then were fed diets including a half percent tannin.

In experiments involving slightly anemic rats, whose iron absorption would tend to be greater, the tannin hindered the rats' ability to absorb the iron by as much as 40 percent. In tests where nonanemic rats were used, the rats were only able to absorb about half of the iron because of the tannins' interference.

"What this tells us is that the effects of tannin on iron absorption are affected by the iron status of the animal," House concludes.

Research geneticist Richard W. Zobel's interests are more down to earth--specifically the rhizosphere, that section of earth where plant roots flourish.

"We're looking at root growth in ridge till versus conventional tillage, with manure versus commercial fertilizer, and with herbicide suppression of weeds versus suppression by cultivation," says Zobel. "Our preliminary results suggest all these techniques give different numbers of roots in corn."

Zobel has in hand at Ithaca 11 tomato mutants whose ratio of large support roots to lateral roots he can manipulate. The laterals, called adventitious roots, "do the real exploring in the soil."

"We want to understand whether these different types of roots have different functions--whether some are more efficient at taking up nutrients, others better at taking up water, or some good at both," he says. "But already with these mutants, we're showing we can modify the plant to fit the environment."

Soil scientist Wendell A. Norvell and research chemist Earle E. Cary are also interested in the uptake of nutrients by plants, but in the controlled environment of the lab rather than the field.

In research, scientists have frequently grown plants hydroponically--with plant roots in liquid rather than in soil. This enables them to do more detailed studies of the plant's natural activities.

However, hydroponically grown plants have typically been grown in solutions containing nutrients at much higher levels than are normally found in soil solution (the liquid surrounding soil particles that supplies nutrients for soil-grown plants).

This difference makes it difficult to compare plants grown in nutrient solution with those grown in soil. While systems to continuously monitor and adjust nutrient levels have been developed to more closely simulate conditions in soil solution, these systems are beyond the reach of many scientists' budgets.

Norvell, Cary, and research associate Ron Checkai have created an alternative approach that is much simpler, and less expensive.

Their system circulates the solution through synthetic mineral-binding particles that hold a supply of nutrients for the growing plants. This arrangement offers the best of both worlds: nutrient-supply conditions similar to those found in soil plus the precision and control offered by hydroponics.

For all its variety, the research at the Ithaca lab maintains a constant thread that should reach easily into the next century, says Darrell Van Campen.

"Our emphasis is really trying to understand how plants take up nutrients and how they transport those nutrients to the edible portions of the plant," he says.

"Sometimes we find something for which the practical significance isn't evident until later. But I think we have to keep our eyes open for more opportunities to apply what we know. We have to be ready to take it on to the next step."

PHOTO : A big step toward understanding biology's ultimate mystery--how do cells make protein, the building blocks of life?--came in 1965 when a team of five ARS and three Cornell University scientists determined that the molecular structure of one of the RNA's, ribonucleic acid. The achievement won the research team's leader Robert W. Holley a share of the 1968 Nobel Prize for Medicine or Physiology. Team members (left to right): Robert Holley, Jean Apgar, James Madison, John Penswick, George Everitt, and Susan Merrill.

PHOTO : The goal of chemist Darrell Van Campen (shown checking growth of young soybean plants) and other researchers at the U.S. Plant, Soil, and Nutrition Research Laboratory is to improve the nutritional quality of food and feed plants.

PHOTO : Plant physiologist Ross Welch compares an unusual Mexican white corn (top) that contains a high-lysine gene with a kernel of commercial yellow corn. Lysine is an essential amino acid.

PHOTO : Chemist James Madison (left) and plant physiologist John Thompson inspect a film autoradiograph, which shows that methionine increases the level of messenger RNA for Bowman-Birk protease inhibitor.

PHOTO : Animal physiologist William House observes a laboratory rat fed tannins obtained from different varieties of beans. Under some conditions, tannins lower the adsorption of dietary iron and depress growth.

PHOTO : These lettuce roots never touch soil or a hydroponic liquid. Instead, the plants get their nutrients from an ultrasonically produced fog. Plant geneticist Richard Zobel can simulate drought or other stresses by precisely altering the fog's volume and nutrient content.

PHOTO : Operating at temperatures similar to the sun's surface, an inductively coupled argon plasma atomic emission spectrometer can detect and quantify 34 elements simultaneously. Chemist Earle Cary checks the computer monitor which is showing a signal for aluminum.

PHOTO : Soil scientist Wendell Norvell adjusts flow through mineral nutrients to hydroponically grown barley plants.

PHOTO : Plant physiologist Leon Kochian uses a two-dimensional vibrating voltage microelectrode to map and measure tiny electric fields found around living, plant roots.

Darrell R. Van Campen, David L. Grunes, James B. Russell, Leon V. Kochian, Ross M. Welch, William A. House, James T. Madison, John F. Thompson, Earle E. Cary, Wendell A. Norvell, and Richard W. Zobel are at the U.S. Plant, Soil, and Nutrition Laboratory, Tower Road, Ithaca, NY 14853. Phone (607) 255-5480.
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Title Annotation:Plant, Soil and Nutrition Laboratory
Author:Hays, Sandy Miller
Publication:Agricultural Research
Date:May 1, 1991
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