Root gravitropism in a cultivar of Zea mays whose columella cells contain starch-deficient amyloplasts

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Starch occupies 4.2 per cent of the volume of plastids in calyptrogen cells in primary roots of Zea mays L. cv. vp-7 wild type. Plastids in calyptrogen cells are distributed randomly around large, centrally located nuclei. The differentiation of calyptrogen cells into columella cells is characterized by cellular enlargement and the sedimentation of plastids to the bottom of the cells. Although sedimented plastids in columella cells do not contain significantly more starch than those in calyptrogen cells, primary roots are graviresponsive. The onset of root gravicurvature is not associated with a significant change in the distribution of plastids in columella cells. These results indicate that in this cultivar of Z. mays (1) the sedimentation of plastids in columella cells is not based upon their increased density resulting from increased starch content alone, (2) starch-laden amyloplasts need not be present in columella cells for roots to be graviresponsive, and (3) the onset of root gravicurvature does not require a major redistribution of plastids in columella cells.

Original languageEnglish (US)
Pages (from-to)661-666
Number of pages6
JournalAnnals of Botany
Issue number6
StatePublished - Jun 1987
Externally publishedYes

Bibliographical note

Funding Information:
This research was supported by a grant from the University Research Committee of Baylor University and by Grant No. NAGW-734 from the Space Biology Program of the National Aeronautics and Space Administration (NASA). I thank Steve Ransom and Eddie McClelen for their excellent technical assistance, and Dr Bill Toland for providing me with arelease-timefellowship to allow me to pursue this research.

Copyright 2010 Elsevier B.V., All rights reserved.


  • Columella cell
  • Gravitropism (root)
  • Plastids
  • Root cap
  • Zea mays


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