Searching for Superplants

"Plants are beautifully designed for reproduction," says Richard Mahoney, "but their efficiency as providers of food is just lousy. They never had any intention of feeding humanity." Yet Mahoney, chief of Monsanto Co.'s agricultural products division, and other plant biologists around the globe are all too aware that the world's burgeoning population is ultimately dependent on plants for food. Their solution: to lend nature a hand by 1) finding or creating new plants that yield more food faster, harvest easier and better resist insects, diseases and climatic extremes or 2) by manipulating existing plants into more efficient food production.

Among the new approaches:

NITROGEN FIXATION. At present only legumes such as peas, beans and alfalfa--with the aid of a soil-dwelling bacterium called rhizobium--are known to be naturally capable of fixing nitrogen from the air--joining it to other substances to form compounds necessary for plant growth. Most other plants must obtain their nitrogen from natural and man-made fertilizers. But scientists are seeking to give more plants this nitrogen-fixing ability. At Utah's Brigham Young University, biologists are attempting to "infect" other species of plants with rhizobia. Scientists in England have isolated the segment of the rhizobial DNA that controls the nitrogen-fixing capability. Now they and other scientists are trying to incorporate this gene into the genetic material of plants like corn. These and other efforts to give grain plants the capability of nitrogen fixation could, if successful, increase the yield of plants and reduce the need for chemical fertilizers. Nitrogen fertilizers require large quantities of natural gas and petroleum to produce.

GENETIC MANIPULATION. Botanists have succeeded in mixing plant genes to create some remarkable hybrids, such as the winter wheat and high-yield corns that have helped make the U.S. plains a global granary. Other hybrids are also helping to fight famine around the world. Pearl millet, introduced in 1965, is currently being grown on some 45 million acres in India, Pakistan and Africa; it accounts for 20% of the food increase attributed to the so-called "Green Revolution" in agriculture. Scientists are also seeking, through cell manipulation, to improve the characteristics of plants. Biologists at the USDA laboratory at Beltsville, Md., and at other centers are experimenting with ways to improve the efficiency of both nitrogen fixation and photosynthesis, the processes by which plants produce the proteins necessary for growth. One researcher has already succeeded in showing that plant engineering may some day be practicable. In 1972 Peter Carlson of Brookhaven National Laboratory managed to unite the cells of two species of tobacco and produce a new plant. Carlson, now at Michigan State University, is currently trying to improve food crops such as corn and sorghum. Other researchers are working to produce plants that have greater resistance to cold, an achievement that could expand both growing seasons and areas where crops can be planted.

GROWTH REGULATION. Growth regulators, those hormone-like substances that control the growth patterns of plants and tell them when to ripen, drop their fruit or prepare for the onset of winter, also have potential for increasing production. Thompson seedless grapes are routinely sprayed with a substance called gibberellic acid, which promotes cell growth and helps produce plumper fruit. A Monsanto product called Polaris is being used experimentally to increase sugar production: sprayed on fields, the chemical enhances the ripening of sugar canes. This, it is believed, boosts their sucrose content and may raise their yield of raw sugar by as much as 10%. Researchers are also looking into ways of using growth regulators to synchronize the ripening of field crops so that all can be harvested in a shorter time, a money-saving measure that could mean lower food prices for consumers.

Many plants already in cultivation could be better used to increase food supplies. Spiros Constantinides of the University of Rhode Island has suggested that okra--whose viscid green pods provide the distinctive ingredient in gumbo dishes--could become an important source of protein if cooks would use its ripe seeds as well as its tasty pods. Researchers with the National Academy of Sciences have been studying a protein-rich "winged bean" that grows in New Guinea and Southeast Asia, and believe it could be successfully introduced into other warm rainy areas where the principal crops--yams, cassava, potatoes--are low in protein. "Believe me, the plant tastes good," says Plant Geneticist Theodore Hymowitz of the University of Illinois. "The flowers taste like mushrooms fried in oil. You can eat the whole thing like an ice cream cone."

The costs of these and other efforts to develop superplants and control plant growth will be high, but worth the price. Pesticides and chemical fertilizers have boosted agricultural yields about as far as they can. But demand for food is increasing. The world's population, now around 4 billion, is increasing at the rate of about 2% a year. Unless food supplies can be increased at at least the same rate, millions may starve.

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