Adventitious Root Initiation in De-bladed Petioles from the Juvenile and Mature Phases of English Ivy

in Journal of the American Society for Horticultural Science
Authors:
Robert L. GeneveDepartment of Horticultural Science and Landscape Architecture, University of Minnesota, St. Paul, MN 55108

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Wesley P. HackettDepartment of Horticultural Science and Landscape Architecture, University of Minnesota, St. Paul, MN 55108

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Bert T. SwansonDepartment of Horticultural Science and Landscape Architecture, University of Minnesota, St. Paul, MN 55108

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Abstract

An in vitro system has been developed to study adventitious root initiation in the juvenile and mature phases of English ivy (Hedera helix L.). The system uses de-bladed petiole explants cultured in a defined liquid medium. Adventitious roots are visible macroscopically after 18 days. Juvenile petiole explants show a dose-response to auxin application with optimal root initiation at 100 μM NAA or IAA. With optimal auxin concentration, root initials form in juvenile petiole explants directly from cortical parenchyma cells, which involves induction (1–6 days), meristem organization (6–9 days), and root elongation stages (9–18 days). Sucrose is required for outgrowth of root primordia but not for initiation of primordia. Mature petiole explants respond to auxin with random cell divisions in cortical parenchyma cells; root initials form at a low frequency from callus resulting from this cortical cell division. Distribution of 14C at various times after administration of 14C-labeled NAA is similar in juvenile and mature petioles. Because of their difference in rooting potential, coupled with similarity in anatomical organization, distribution of 14C from NAA, and identical genotype, juvenile and mature petioles provide an excellent experimental system for analyzing the morphogenetic, physiological, and genetic basis of rooting potential. Chemical names used: 1-napthaleneacetic acid (NAA); 1H-indoIe-3-acetic acid (IAA).

Contributor Notes

Present address: Dept. of Horticulture and Landscape Architecture, Univ. of Kentucky, Lexington, KY 40546.

Received for publication 20 Aug. 1987. The cost of publishing this paper was defrayed in part by the payment of page charges. Under postal regulations, this paper therefore must be hereby marked advertisement solely to indicate this fact.

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