Planta

, Volume 177, Issue 2, pp 198–206

Amyloplasts are necessary for full gravitropic sensitivity in roots of Arabidopsis thaliana

  • John Z. Kiss
  • Rainer Hertel
  • Fred D. Sack
Article

DOI: 10.1007/BF00392808

Cite this article as:
Kiss, J.Z., Hertel, R. & Sack, F.D. Planta (1989) 177: 198. doi:10.1007/BF00392808

Abstract

The observation that a starchless mutant (TC7) of Arabidopsis thaliana (L.) Heynh. is gravitropic (T. Caspar and B.G. Pickard, 1989, Planta 177, 185–197) raises questions about the hypothesis that starch and amyloplasts play a role in gravity perception. We compared the kinetics of gravitropism in this starchless mutant and the wild-type (WT). Wild-type roots are more responsive to gravity than TC7 roots as judged by several parameters: (1) Vertically grown TC7 roots were not as oriented with respect to the gravity vector as WT roots. (2) In the time course of curvature after gravistimulation, curvature in TC7 roots was delayed and reduced compared to WT roots. (3) TC7 roots curved less than WT roots following a single, short (induction) period of gravistimulation, and WT, but not TC7, roots curved in response to a 1-min period of horizontal exposure. (4) Wild-type roots curved much more than TC7 roots in response to intermittent stimulation (repeated short periods of horizontal exposure); WT roots curved in response to 10 s of stimulation or less, but TC7 roots required 2 min of stimulation to produce a curvature. The growth rates were equal for both genotypes. We conclude that WT roots are more sensitive to gravity than TC7 roots. Starch is not required for gravity perception in TC7 roots, but is necessary for full sensitivity; thus it is likely that amyloplasts function as statoliths in WT Arabidopsis roots. Furthermore, since centrifugation studies using low gravitational forces indicated that starchless plastids are relatively dense and are the most movable component in TC7 columella cells, the starchless plastids may also function as statoliths.

Key words

AmyloplastArabidopsisGravitropismGravityMutant (gravitropism)Plastid and graviperceptionStarch and graviperceptionStatolith

Abbreviations

S2

story two

S3

story three

WT

wild-type

Copyright information

© Springer-Verlag 1989

Authors and Affiliations

  • John Z. Kiss
    • 1
  • Rainer Hertel
    • 2
  • Fred D. Sack
    • 1
  1. 1.Department of BotanyOhio State UniversityColumbusUSA
  2. 2.Institut für Biologie III der UniversitätFreiburg/Br.FRG