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Construction and Testing of a Ground-Based Hypogravity Simulator. H. Ishikawa, E. Natori and M.L. Evans  Dept. of Plant Cellular and Molecular Biology, The Ohio State University, Columbus, OH.

   It has been possible to simulate 0g in ground-based experiments using the random positioning machine (RPM, 3-D clinostat) and to impose hypergravity using centrifugation. However, no method is available for simulating partial g forces (gravitational forces between 0g and 1g).  We are constructing an R-RPM, a new device designed to simulate partial g on Earth.  The approach is to program an RPM so that the 3D rotation, instead of being completely random, favors net orientation of a gravity-sensing region (e.g. root tip) in a particular direction. Thus partial g simulation is achieved through a programmed integration of the stimulus over time.  For example, a statistical shift in favor of a given orientation for 20% of the integrated rotation pattern would mimic 0.2g in that direction.  Programming the RPM to apply a specific vectorial partial g exposure, however, requires that the target remain in a fixed orientation. To accomplish this we are mounting a ROTATO system on the RPM (constructing an “R-RPM”).  ROTATO is a combined video imaging/mechanical rotation system capable of maintaining a target such as a root tip in a fixed position during a gravitropic response (2000 Mullen et al. Plant Physiol 123: 665-670).  Using the combined capabilities of ROTATO and the RPM we can apply partial g exposures along defined vectors within the root cap.  Preliminary results from such experiments will be presented. 

(supported by NASA: NNA04CC65G)