NASA has awarded Kiss more than $1 million over the past six years for "Tropi, Analysis of a Novel Sensory Mechanism in Root Phototropism," an experiment to study how plant roots respond to varying levels of both light and gravity.

Insights gained from Tropi can help create sustainable plant-based life support systems for long-term space missions, part of NASA's exploration agenda. Plants will be needed as a food source and as oxygen producers on long-range trips to Mars, for example.

Tropi consists of dry Arabidopsis thaliana - thale cress - seeds stored in small seed cassettes, Kiss explained. The seed cassettes will be flown inside the European Modular Cultivation System, an experiment facility for biological investigations under microgravity.

A 655-pound incubator, EMCS provides control over atmosphere, lighting and humidity of growth chambers.

Tropi will be the first experiment performed in the EMCS, which was developed by ESA. The experimental containers were developed by Kiss' group at Miami University of Ohio and NASA, based on a design by project co-principal investigator Richard Edelmann, director of Miami's electron microscopy facility.

Discovery will deliver supplies, equipment and a new crew member - ESA astronaut Thomas Reiter - to the ISS. Once on board, Tropi experiments will be performed automatically inside the EMCS, requiring minimal involvement by the Expedition 13 crew members.

According to Kiss, spaceflight procedures require loading the ECs into the EMCS, replacing videotapes and harvesting plants when they are grown. Harvested plants will be stored in the Minus Eighty Degree Laboratory Freezer until their return to Earth.

When the samples from Tropi arrive back on Earth - estimated to be by the end of the year - data analysis will begin. Plant germination, growth and curvature will be analyzed from the videotapes, and DNA analysis will be conducted on the frozen plant samples to determine how the different light and gravity treatments affect gene expression.

Kiss and Edelmann also had experiments on gravitropism - how plants respond to gravity - on two space shuttle missions in 1997.

Plants may be able to be used in bioregenerative life support on Mars, Kiss said. They can be engineered to grow under the stresses of long-term space flight such as water deficits and high ethylene concentrations, or under stresses unique to other planets such as Mars.

Coincidentally, just last week, astrophysicist Stephen Hawking stated in a lecture in Hong Kong that for the survival of the species, humans should develop space settlements that can continue without support from Earth.

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