Yi Li has a special interest in the space shuttle Discovery. It will be carrying his tomato seeds when it takes off on Oct. 29.

A green thumb is not a prerequisite for John Glenn or any one of his shuttle colleagues who will be responsible for the 60 genetically engineered tomato seeds, says Li, an assistant professor of plant science.

The seeds will travel millions of miles during their nine-day space trip, to help Li and other scientists understand how microgravity affects tomato plants that have a genetically altered concentration of ethylene, a stress hormone in plants.

When plants are under unfavorable conditions, says Li, stress is unavoidable. "And if the stress hormone is at high concentrations, plants will not grow well."

Once plants enter space's atmosphere, they produce high levels of the stress hormone because plants grown on earth are constantly exposed to gravity whereas in space gravity is at proportions that plants are not used to, he says.

Li believes a reduction in ethylene production in his genetically enhanced seeds will make plants grow better in space.

The seeds will be contained in growth chambers at 23 degrees celsius. All one of the astronauts will be required to do is press a button that will fill the chambers with enough water to enable the seeds to germinate and grow. But before Discovery returns to earth, a crew member will press another button to release a solution onto the plants that will kill them and preserve them as well, so they maintain the shape, texture and composition they had in space.

The short trip on Discovery will give Li's seeds just enough time to grow roots so that he can run tests once the plants return to earth and are shipped back to his lab.

"If the genetically engineered plants are successful," Li says, "It should give tomato plants a better opportunity to produce in space. Green plants are an important component of the bio-regenerati ve life support system to support crews in extraterrestrial environments, because of their ability to consume carbon dioxide, remove pollutants and generate oxygen."

Li says green plants have to be a food source made available to astronauts, "especially if space travel gets to a point where it can last for a couple of years. Canned goods are not a healthy diet," he says.

Controlling production of the stress hormone in plants in space has the potential to benefit a shuttle crew, but it can also serve as a foundation to reduce the amount of stress a plant puts itself through on earth.

Genetically engineered tomato plants that will experience minimal amounts of the stress hormone have also been tested on earth, Li says, and the fruits produced from these plants have longer shelf-lives.

Li, who joined UConn this year from Kansas State University, has conducted plant experiments on space shuttles seven times. "I am excited," he says, "because every space expedition that I have been involved in has produced new information that scientists are able to use."

His experiment on Columbia in 1997 enabled Li to gain a better understanding of effects if microgravity on the concentration and distribution of the growth hormone auxin within the plants.

Pharmaceutical companies are also keeping an eye on the growth habits of plants in space. If experiments by Li and other scientists are successful, pharmaceutical companies may be able to use the plants as bio-reactors for pharmaceutical products.

"Production of taxol, an anti-cancer compound from a tree named the Pacific Yew, can be enhanced when the plants are cultured in space shuttles," Li says. "If we can improve the growth rate of plants inspace, it can lead to ways of increasing the production of these anti-cancer compounds."

Luis Mocete