This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Taylor, J. S. Articles by Pharis, R. P. Search for Related Content PubMed PubMed Citation Articles by Taylor, J. S. Articles by Pharis, R. P. Agricola Articles by Taylor, J. S. Articles by Pharis, R. P.

Development and Growth Regulation

Cytokinins in the Phloem Sap of White Lupin (Lupinus albus L.) ¹

Botany Department, University of Western Australia, Nedlands, Western Australia 60009, Australia, Plant Physiology Research Group, Department of Biological Sciences, University of Calgary, Calgary, Alberta T2N 1N4, Canada

Cytokinin-like activity in samples of xylem and phloem sap collected from field-grown plants of white lupin (Lupinus albus L.) over a period of 9 to 24 weeks after sowing was measured using the soybean hypocotyl callus bioassay following paper chromatographic separation. The phloem sap was collected from shallow incisions made at the base of the stem, the base of the inflorescence (e.g. stem top), the petioles, and the base and tip of the fruit. Xylem sap was collected as root exudate from the stump of plants severed a few centimeters above ground level. Concentration of cytokinin-like substances was highest in phloem sap collected from the base of the inflorescence and showed an increase over the entire sampling period (from week 10 [61 nanogram zeatin equivalents] to week 24 [407 nanogram zeatin equivalents]). Concentrations in the xylem sap and in the other phloem saps were generally lower. Relatively high concentrations of cytokinin-like substances in petiole phloem sap (70 to 130 nanogram zeatin equivalents per milliliter) coincided in time with high concentrations in sap from the base of the inflorescence (see above). Concentrations in sap (phloem or xylem) from the base of the stem were very much lower. This finding is consistent with movement of cytokinins from leaves into the developing inflorescence and fruit, rather than direct input to the fruit from xylem sap. However, an earlier movement of cytokinins from roots into leaves via the xylem cannot be ruled out. Sap collected at an 18-week harvest was additionally separated by sequential C₁₈ reversed-phase high performance liquid chromatography NH₂ normal phase high performance liquid chromatography, bioassayed, and then analyzed by electron impact gas chromatography-mass spectrometry. Identification of zeatin riboside and dihydrozeatin as two of the major cytokinins in combined sap samples was accomplished by gas chromatography-mass spectrometry-selected ion monitoring.

¹ Supported by Natural Sciences and Engineering Research Council of Canada Grant No. A-2585 (R.P.P.), and Australian Research Grants Scheme Grant (J.S.P).

This article has been cited by other articles:

				R. Aloni, M. Langhans, E. Aloni, E. Dreieicher, and C. I. Ullrich Root-synthesized cytokinin in Arabidopsis is distributed in the shoot by the transpiration stream J. Exp. Bot., June 1, 2005; 56(416): 1535 - 1544. [Abstract] [Full Text] [PDF]

				R.J. N. Emery, Q. Ma, and C. A. Atkins The Forms and Sources of Cytokinins in Developing White Lupine Seeds and Fruits Plant Physiology, August 1, 2000; 123(4): 1593 - 1604. [Abstract] [Full Text]