Uh, Houston: This Spud's for You

IT'S one small step for potatoes, and one giant leap for curly fries in space.

Alongside more exotic experiments aboard the space shuttle Columbia, scheduled for launch today, sits a high-tech package of potato cuttings that researchers hope will sprout tiny spuds during the 16-day mission.

The experiment is one of several funded by the National Aeronautics and Space Administration to find ways to keep space-station astronauts and scientists well-fed.

''If a space station is put into orbit, it will be too expensive to shuttle groceries back and forth,'' says Judith Croxdale, a botanist at the University of Wisconsin at Madison and a member of the team conducting the experiment. ''So, we're attempting to grow food in space.''

The experiment also bears on the long-term use of space habitats. Planners envision using plants to help regulate humidity, replenish oxygen, and remove carbon dioxide from the atmospheres of manned structures in space.

Food species such as wheat have been used in past space experiments, Dr. Croxdale says. But these studies looked at stages of plant growth that fell short of actually producing what people eat. By using Earth-grown cuttings for the potato experiment, ''all of the plants' structural elements are in place'' for food production.

One of the main objectives is to see whether tiny tubers form at all, and if they do, what shape they take. A potato's cells are arranged in a honeycomb pattern, while the skin's cells are stacked like bricks. Absent significant amounts of gravity, she says, it is unclear how the cells will arrange themselves. The cuttings' buds might form tubers, or they might just form new leafy branches.

Another issue involves the nutritional value of a space-grown spud.

Some experiments, Croxdale says, have indicated that a potato plant's ability to make starch falls in weak gravity. If that proves true, the options may be either to boost the size of the galley's mashed-potato serving or genetically engineer potatoes to produce adequate carbohydrates under microgravity conditions.

One of the key challenges was developing the on-orbit nursery for nurturing plants. Star Trek notwithstanding, ''You can't take a watering can into space,'' Croxdale quips.

The device for growing the potatoes has been refined over four previous shuttle flights. Developed by Wisconsin's Center for Space Automation and Robotics, the ''Astroculture'' system uses two chambers the size of half-gallon milk cartons to hold the plants. The device also uses porous tubes buried in the planting medium to deliver nutrients and help plants recycle water. ''One of the biggest costs of life support is transporting and disposing of water on space missions,'' says Raymond Bula, director o f the space-robotics center and one of two other members of the research team. ''If you can develop a way to recycle the water, that's a very significant contribution. And plants can do that.''

To reduce unwanted heat and to keep electricity consumption low, the system uses red and blue light-emitting diodes instead of incandescent bulbs. Light at these wavelengths improves the speed with which the plant turns light into food through photosynthesis. Small video cameras in the chambers will allow the research team to monitor the progress of the experiment.

Some of these subsystems already have found commercial uses, according to Dr. Bula. The lighting modules are being used for photosynthesis research and in some medical applications.