Shuttle's corn experiment tests plants' ability to adapt to low gravity

When launched last Friday, the space shuttle Discovery carried a tiny bit of a Midwest farm in its hold: 36 corn seeds, to be exact. The corn is the center of an experiment proposed two years ago by Nebraska high school student Sean Amberg, working with University of Nebraska botany Prof. Eric Davies. Its purpose: to explore further how plants adapt to near-weightlessness.

The topic is of considerable interest to the National Aeronautics and Space Administration (NASA). The ability to grow successive generations of plants in space would brighten prospects for designing space facilities that could recycle air, food, and water, rather than require continual resupply from Earth.

This is not the first time that plants have been carried into space. United States and Soviet missions have done so in the past. The Soviets, more active in this field, have reported that plants will germinate and grow without problems in zero gravity. But the experiments have been short compared to plant life cycles. So it is not known whether the progeny of plants grown in orbit may be adversely affected.

``I don't think this will be the case, but it has to be demonstrated,'' explains Louis Feldman, a botany professor at the University of California at Berkeley, and one of the world's leading experts on root growth. He reviewed the experiment for NASA.

Plant roots, in particular, are sensitive to gravity. In an area called the root cap, special tissue structures called statoliths sense gravity. That's how a root knows to grow downward. Mr. Amberg's experiment starts with corn seeds sprouted a few hours before launch, with the root caps surgically removed. When this is done, the root temporarily loses its gravity-sensing ability. The idea is to see if the root cap regrows naturally.

To make sure the plant doesn't readjust to gravity upon return, engineers at Martin Marietta Aerospace, which sponsored the experiment, spent considerable time designing special compartmented plastic pouches. One compartment has a chemical that kills and preserves the roots. Shortly before the shuttle lands, an astronaut will squeeze the chemical into the pouch holding the seeds.

Once the samples return to Earth, Amberg, now a student at Massachusetts Institute of Technology, and Colorado State University Prof. Paul Kugrens will study the regrown tissue. If the statoliths appear normal, this will be compelling evidence that plants can reproduce satisfactorily in ``zero G,'' Dr. Feldman explains.