Abstract
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 language | English |
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Pages (from-to) | 465-471 |
Number of pages | 7 |
Journal | Plant Physiology and Biochemistry |
Volume | 43 |
Issue number | 5 |
DOIs | |
Publication status | Published - 2005 May 1 |
Keywords
- 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