Journal Article

Reduced Gravitropism in Hypocotyls of Starch-Deficient Mutants of <i>Arabidopsis</i>

John Z. Kiss, Mary M. Guisinger, Allison J. Miller and Kathi S. Stackhouse

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 38, issue 5, pages 518-525
Published in print January 1997 | ISSN: 0032-0781
Published online January 1997 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/oxfordjournals.pcp.a029199
Reduced Gravitropism in Hypocotyls of Starch-Deficient Mutants of Arabidopsis

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Gravitropism was examined in dark- and light-grown hypocotyls of wild-type (WT), two reduced starch mutants (ACG 20 and ACG 27), and a starchless mutant (ACG 21) of Arabidopsis. In addition, the starch content of these four strains was studied with light and electron microscopy. Based on time course of curvature and orientation studies, the graviresponse in hypocotyls is proportional to the amount of starch in a genotype. Furthermore, starch mutations seem to primarily affect gravitropism rather than differential growth since both phototropic curvature and growth rates among the four genotypes are approximately equal. Our results suggest that gravity perception may require a greater plastid mass in hypocotyls compared to roots. The kinetics of gravitropic curvature also was compared following reorientation at 45°, 90°, and 135°. As has been reported for other plant species, the optimal angle of reorientation is 135° for WT Arabidopsis and the two reduced starch mutants, but the magnitude of curvature of the starchless mutant appears to be independent of the initial angle of displacement. Taken together, the results of the present study and our previous experiments with roots of the same four genotypes [Kiss et al. (1996) Physiol. Plant. 97: 237] support a plastid-based hypothesis for gravity perception in plants.

Keywords: Arabidopsis; Gravity perception; Plastids; Shoots; Space biology; Statolith

Journal Article.  0 words. 

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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