ASGSB 1999 Annual Meeting Abstracts

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THE INFLUENCE OF SPACEFLIGHT AND MICROGRAVITY ON COLUMELLA CELL STRUCTURE IN ARABIDOPSIS. J. Z. Kiss and M.M. Guisinger. Department of Botany, Miami University, Oxford, OH

The ultrastructure of root cap columella cells was studied by morphometric analysis in wild-type, a reduced-starch mutant, and a starchless mutant of Arabidopsis grown in microgravity (F-µg) and compared to ground 1g (G-1g) and flight 1g (F-1g) controls. These experiments were flown on the European Space Agency’s Biorack module during Space Shuttle mission STS-84 in May 1997. Seedlings of the wild-type and reduced-starch mutant that developed during the experiment in space (both the F-µg samples and the F-1g control) exhibited a decreased starch content in comparison to the G-1g control. For example, in the second story columella cells of WT roots, both flight samples had approximately 70% of the starch content as the ground control. These results suggest that some factor associated with spaceflight (and not microgravity per se) affects starch metabolism. Elevated levels of ethylene (1.1 - 1.6 ppm) were found during the experiments on the Space Shuttle, and analysis of ground controls with added ethylene demonstrated that this gas was responsible for decreased starch levels in the columella cells. This is the first study to use an on-board centrifuge as a control when quantifying starch in spaceflight-grown plants. Furthermore, our results show that ethylene levels must be carefully considered and controlled when designing experiments with plants for the International Space Station. 

(Financial support was supplied by NASA grant NAG 2-1017 to JZK.)

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