Mechanism of inhibition of cytoplasmic streaming by auxin in root hair cells of Hydrocharis

Motoki Tominaga*, Seiji Sonobe, Teruo Shimmen

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

11 Citations (Scopus)


It has been reported that auxin accelerates cytoplasmic streaming at low concentrations and inhibits it at high concentrations in several plant cells. In the present study, the mechanism of inhibition of cytoplasmic streaming by naphthalene acetic acid (NAA) at high concentrations was analyzed in root hair cells of Hydrocharis. Because the effective concentration of NAA inhibiting cytoplasmic streaming decreased when the extracellular pH (pHo) was lowered, it was hypothesized that cytoplasmic streaming is inhibited by NAA via acidification of the cytoplasm. This possibility was supported by the fact that acetic acid, propionic acid and decanoic acid also inhibited cytoplasmic streaming at low pHo. Acidification of the cytoplasm disturbed the orientation of actin filaments (AFs) and disrupted cortical microtubules (MTs). The effects of NAA were reversible; both cytoplasmic streaming and organization of the cytoskeleton were recovered upon removal of NAA. During the recovery, tracks of cytoplasmic streaming in the subcortical region temporarily showed a helical pattern along the longitudinal direction of the cell. Fluorescence staining of cytoskeletons revealed that both AFs and MTs aligned obliquely to the longitudinal axis of the cell. The helical streaming returned to the original reverse fountain streaming after several hours. The simultaneous changes in the organization of both cytoskeletons supported our previous report that the organization of AFs is regulated by MTs.

Original languageEnglish
Pages (from-to)1342-1349
Number of pages8
JournalPlant and Cell Physiology
Issue number12
Publication statusPublished - 1998 Dec
Externally publishedYes


  • Actin filament
  • Auxin
  • Cytoplasmic streaming
  • Hydrocharis
  • Microtubule
  • Root hair cell

ASJC Scopus subject areas

  • Physiology
  • Plant Science
  • Cell Biology


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