The possible involvement of root-cap mucilage in gravitropism and calcium movement across root tips of Allium cepa L

Randy Moore, W. Mark Fondren

Research output: Contribution to journalArticlepeer-review

14 Scopus citations

Abstract

Roots of Allium cepa L. grown in aerated water elongate rapidly, but are not graviresponsive. These roots (1) possess extensive columella tissues comprised of cells containing numerous sedimented amyloplasts, (2) lack mucilage on their tips, and (3) are characterized by a weakly polar movement of calcium (Ca) across their tips. Placing roots in humid air correlates positively with the (1) onset of gravicurvature, (2) appearance of mucilage on tips of the roots, and (3) onset of the ability to transport Ca polarly to the lower side of the root tip. Gravicurvature of roots previously submerged in aerated water is more rapid when roots are oriented vertically for 1-2 h in humid air prior to being oriented horizontally. The more rapid gravicurvature of these roots correlates positively with the accumulation of mucilage at the tips of roots during the time the roots are oriented vertically. Therefore, the onset of gravicurvature and the ability of roots to transport Ca to the lower sides of their tips correlate positively with the presence of mucilage at their tips. These results suggest that mucilage may be important for the transport of Ca across root caps.

Original languageEnglish (US)
Pages (from-to)381-387
Number of pages7
JournalAnnals of Botany
Volume58
Issue number3
DOIs
StatePublished - Sep 1986

Bibliographical note

Funding Information:
This research was supported by grants from the National Aeronautics and Space Administration (NASA) and the University Research Committee of Baylor University. We thank Eddie McClelen and Paula Davidson for their helpful discussions and technical assistance. We also thank Dr William G. Toland for providing R. M. with release time to conduct this research.

Keywords

  • Allium cepa
  • Calcium
  • Onion
  • Root gravitropism
  • Root mucilage

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