Polyamines in Relation to Cell Division and Xylogenesis in Cultured Explants ofHelianthus tuberosus: Lack of Evidence for Growth-Regulatory Action

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Abstract
Phillips, R., Press, M. C. and Eason, A. 1987. Polyamines in relation to cell division and xylogenesis in cultured explants of Helianthus tuberosus: lack of evidence for growth-regulatory action.—J. exp. Bot. 38: 164–172. The polyamines spermidine, diaminopropane, and cadaverine were found to accumulate in cultured tuber explants of H. tuberosus (Jerusalem artichoke). Rapid increases in all amines occurred during the initial 24 h corresponding to the period of activation and the onset of mitosis. Levels then declined during the following phases of rapid cell proliferation and xylem differentiation. The type and distribution of polyamines was not markedly affected by changes in medium or culture conditions, and the inhibitor MGBG did not alter cell division rates or polyamine content markedly although xylem differentiation was substantially depressed. Exogenously supplied spermidine and putrescine did not substantially alter the cellular responses of explants cultured in the presence of auxin. In the absence of supplied auxin, spermidine at 1·0 mol m–3 produced an increase in cell division, although this was small in comparison with auxin-stimulated responses. The implications of these findings on the possibility that polyamines act as growth regulators in plants is discussed.