CORVALLIS - An Oregon State University student whose tomato cell gravity experiment went rocketing into orbit with astronaut John Glenn hopes to repeat his study on an upcoming space shuttle or space station mission.
"The results from the space shuttle Discovery are suggestive, but inconclusive," said Andreas Madlung, a OSU doctoral candidate from Corvallis, whose access to the shuttle was arranged as part of a donation of hardware and space access from Instrumentation Technology Associates' Student Space Education Outreach Program.
The Exton, Penn., firm transferred Madlung's tomato cell cultures and a nutrient-rich agar solution into 10 microwells and sealed them for the nine-day shuttle flight to study the effects of microgravity. The shuttle returned to Earth on Nov. 7.
"There's a trend there," Madlung said, as he scanned results from the shuttle experiment. "What we'd like to do is repeat this experiment on a larger scale. The space station would be a perfect place to do an experiment like that."
Madlung's goal on the Discovery flight was to find out how the plant tissue would react to Discovery's microgravity conditions. Central to the ITA-OSU experiment were tracheary elements - essentially hollow xylem cells which, when formed end-to-end, develop into the water-conducting vessels in plant stems, roots and leaves.
Plants receive most of their water from their roots and then, against the force of gravity, must send the moisture through networks of stems, branches and leaves. The xylem cells perform the water-conducting function as well as provide support for the plant to stand against the force of gravity.
"To our knowledge, it has not been established whether or not gravity plays a direct role in the formation of the tracheary elements, or, the water pipes," Madlung said. "It can only be speculated whether it was necessary for plants to evolve (tracheary elements) and other thickened supporting structures to defy the gravity environment and whether or not gravity induces the formation of tracheary elements directly, possibly via auxin and cytokinins," hormones that are key regulators of plant growth.
"The main focus of this study was to gain insights into this question."
Using cells from both wild-type and mutant cultures, some cultures were laced with auxin and cytokinin, and in other specimens, no hormones were added, Madlung said. The mutant cultures are insensitive to auxin, but produce more than the normal amount of tracheary elements on Earth.
In specimens kept on nutrient agar without hormones, both in flight or on-the-ground, neither the normal or the mutant cultures produced the xylem waterways, Madlung said. During the shuttle flight, the wild-type cells with hormones produced fewer of the water-conducting cells, while the mutant cultures produced even more tracheary elements than while on the ground.
"While the results are encouraging, more research is necessary before conclusions can be drawn," Madlung said.
"I think that the results indicate that our hypothesis is correct," said Terri Lomax an OSU associate professor of botany and plant pathology, and Madlung's doctoral supervisor. "The plants use xylem cells as a response against gravity. The mutant is interesting in that it has a backwards, or reverse response on Earth, which is even more backwards in the absence of gravity. I'm amazed that we saw such results in so little as nine days," she said.
But Lomax also cautions that the results are inconclusive and agrees that further study is needed.
"On the shuttle, we learned a lot about how to carry out the research," Lomax said, comparing the experience to a trial run. "A space station would be an ideal environment" for further research.
"With the preliminary results gained from this flight, we are planning to write a proposal that will allow us to continue this project either on a future space shuttle flight or in the space station that is being built and should be ready for the first experiments in 2004," Madlung said.
He added that private "space firms" such as Instrumentation Technology Associates are making space research more accessible to scientists. Since 1982, ITA has worked to develop multi-year flight arrangements with space agencies and private organizations worldwide and to facilitate access to space flight for industry, research institutions and entrepreneurs. In 1990, ITA created a successful student hands-on outreach program that allows students to develop and fly their own experiments in space. More than 30 educational institutions around the world have flown their own experiments through ITA's donation of hardware and space access.