ASGSB 1999 Annual Meeting Abstracts

TURNING ROOT GRAVITROPISM UPSIDE-DOWN: A STUDY OF CONSTANT-STIMULUS RESPONSES IN ARABIDOPSIS USING A FEEDBACK SYSTEM. J.L. Mullen, C. Wolverton, H. Ishikawa, and M.L. Evans. Dept of Plant Biology, The Ohio State University, Columbus.

The study of gravitropism is hindered by the fact that as a root responds, the gravitational stimulus changes. Using a feedback system to connect a rotating stage platform to a video digitizer system, we were able to maintain a constant angle of gravistimulation to Arabidopsis roots for long time periods. The rate of curvature approximated the sine rule for angles of stimulation between 0 and 120. The rate of curvature also remained constant, with no observed attenuation of the response. While previous reports of Arabidopsis root gravitropism suggest latent periods of approximately 30 minutes, we observed a mean time lag of less than 15 min. This more rapid onset of curvature can, in part, be explained by reduced mechanical perturbation during the process of gravistimulation. This suggests that mechanical stimulation may confound investigations of early gravitropic events.

(Supported by NASA: NAG5-6385, NAG2-1190, and the NASA/NSF Joint Program in Plant Biology, Network for Research on Plant Sensory Systems: IBN-9421856)

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