ASGSB 1999 Annual Meeting Abstracts

RESTORATION OF GRAVITROPIC SENSITIVITY IN STARCH-DEFICIENT MUTANTS OF ARABIDOPSIS BY HYPERGRAVITY. K. J. Fitzelle and J. Z. Kiss. Department of Botany, Miami University, Oxford, OH 45056.

Plant gravitropism has been extensively studied, yet there have been few experiments which have utilized hypergravity as a tool to investigate graviperception in higher plants. Previous research has shown that starch-deficient mutants of Arabidopsis are less sensitive to gravity compared to their wild-type (WT). In this report, the question being addressed is whether hypergravity can restore the sensitivity of these starch-deficient mutants of Arabidopsis. The strains examined include a starchless (pgm) mutant (ACG 21) and two reduced starch mutants (ACG 20 & ACG 27). Vertical orientation studies with dark-grown seedlings indicate that increased centrifugal force improves orientation relative to the gravity vector for all strains, even the WT. For roots, growth of seedlings under constant 5-g force restored the starchless mutant to a WT level of orientation. For hypocotyls, approximately 10-g is required to restore the orientation of the starchless mutant to WT levels. In addition, seed germination and growth rates of the hypergravity-grown plants were similar to those grown at 1 g. Time course of curvature experiments and examination of plastid position studies are currently in progress. These experiments should help resolve issues regarding the theories of graviperception in plants. (Financial support was provided by NASA grant NAG 2-1017).

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