Squash xylem sap has activities that inhibit proliferation and promote the elongation of tobacco BY-2 cell protoplasts

Takeshi Kuroha, Masato Sakurai, Shinobu Satoh

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)


To elucidate the physiological functions of the substances in xylem sap, we analyzed the biological activities of xylem sap from squash (Cucurbita maxima Duch.) root using tobacco BY-2 (Nicotiana tabacum L. cv. Bright Yellow 2) cell protoplasts. When BY-2 cell protoplasts were cultivated with the total substance of squash xylem sap, the protoplasts elongated remarkably, and cell division was inhibited. Although trans-zeatin riboside (ZR), the most abundant cytokinin in squash xylem sap, had a concentration-dependent effect similar to that of total squash xylem sap, ZR concentrations several orders of magnitude greater than those found endogenously in squash xylem sap (i.e. 2 × 10 -8:M) were required to affect the growth of BY-2 cell protoplasts. The ability to stimulate cell elongation and inhibit cell division in BY-2 cell protoplasts was observed for the ethyl acetate phase fraction (pH 2) of squash xylem sap and an acetonitrile-eluate fraction from reverse-phase chromatography. The xylem sap also showed inhibitory activity for auxin-induced elongation of excised cucumber hypocotyls. These results suggest that an organic substance other than ZR is produced in the root and transported to above-ground organs through the xylem via the transpiration stream, where it is involved in regulating cell proliferation and elongation in the shoot, possibly as an auxin antagonist.

Original languageEnglish
Pages (from-to)465-471
Number of pages7
JournalPlant Physiology and Biochemistry
Issue number5
Publication statusPublished - 2005 May
Externally publishedYes


  • Cell division
  • Cell elongation
  • Root
  • Squash (Cucurbita maxima Duch.)
  • Tobacco BY-2 (Nicotiana tabacum L. cv. Bright Yellow 2)
  • Xylem sap

ASJC Scopus subject areas

  • Physiology
  • Genetics
  • Plant Science


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