ASGSB 1999 Annual Meeting Abstracts

COMPARISON OF AMYLOPLAST POSITION IN ARABIDOPSIS ROOTS IN DIFFERENT GRAVITY ENVIRONMENTS. T. F. B. Kraft and J. Z. Kiss. Department of Botany, Miami University, Oxford OH.

Instruments that attempt to simulate microgravity have been constructed to aid studies that measure the effects of space and microgravity on organisms. Although these devices are less expensive than conducting space flight experiments, the degree to which these simulators provide a true microgravity environment needs to be evaluated in higher plants. In this study, the position of amyloplasts was studied in the roots of Arabidopsis WT that were grown in the following conditions: on Earth, in a two-dimensional clinostat, in a three-dimensional clinostat (also called a random positioning machine or an RPM), and in space (true microgravity). Roots were sectioned with an ultramicrotome and photographed with a light microscope under brightfield optics. The images were then digitized and analyzed with the computer program Image-Pro-Plus. The amyloplasts of plants grown on Earth were found to be concentrated at the distal end of columella cells in the root tip. However, amyloplasts from plants grown on the two-dimensional clinostat, on the RPM, and in space were more scattered throughout the columella cells. Studies are in progress to quantitate the amyloplast position in the various gravity treatments. Based on past studies (e.g., Chara rhizoids), our working hypothesis is that the RPM provides a better simulation of microgravity than does the two-dimensional clinostat. This is the first study to compare plastid position in roots of seedlings grown in true microgravity to plastid position in roots of seedlings grown on both a two-dimensional clinostat and on an RPM. (Special thanks to Jack van Loon of DESC.

Financial support was provided by NASA grant NAG 2-1017 and the Howard Hughes Summer Internship program at Miami University.)

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