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Use of  Rotato/Random Positioning Machine (R/RPM) Technology to Investigate Gravity Sensing and the Gravitropic Motor Response of Maize Roots.   H. Ishikawa, E. Natori, and M.L. Evans

Dept. of Plant Cellular and Molecular Biology, The Ohio State University, Columbus, OH.

   We have merged the capabilities of ROTATO (an imaging/mechanical rotation system capable of maintaining a target such as a root tip in a fixed position during a gravitropic response, Mullen et al. Plant Physiol 123: 665-670) with a 3-D clinostat (Random Positioning Machine, RPM).  The combined system (R/RPM) is capable of automated recording of root growth rate patterns and localized shape changes while simultaneously exposing a selected target region of the root to simulated zero g or simulated hypo-g (e.g. 0.5 g). The approach to simulation of hypo-g is to program the RPM so that the 3-D rotation, instead of being completely random (simulated zero g), favors net orientation of a gravity-sensing region (e.g. root tip) in a particular direction. Thus partial g simulation is achieved through integration of the stimulus over time.  The ROTATO ( R) component of the R/RPM is used to maintain the stimulation target tissue in a fixed orientation so that the integrated stimulus provided by the RPM can be applied to that region.  An early application of the this system is to investigate the effects of simulated zero g and hypo-g on the two key components of the gravitropic response of maize roots (Phase 1 and Phase 2 curvature, see Natori et al., this meeting).  The R/RPM is being used to examine the effects of prestimulation at simulated zero g or hypo g on Phase 1 and Phase 2 curvature with and without maintenance of a constant gravitational stimulus by ROTATO and to examine the effect of transient loss (zero g) or reduction (hypo-g) of the gravistimulus midcourse during a gravitropic response.

(Supported by NASA: NNA04CC65G)