Regeneration of roots, shoots and embryos: physiological, biochemical and molecular aspects |
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Authors: | G-J De Klerk B Arnholdt-Schmitt R Lieberei K-H Neumann |
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Institution: | (1) Centre for Plant Tissue Culture Research, Po Box 85, 2160 Ab Lisse, the Netherlands;(2) Institute of Plant Nutrition, Justus-Liebig University, Südanlage 6, 35390 Giessen, Germany;(3) Institute of Applied Botany, University of Hamburg, Marseiller Str. 7, 20355 Hamburg, Germany |
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Abstract: | When the proper stimuli are given, somatic plant cells may form adventitious embryos, roots or shoots. The three pathways
of regeneration show apparent similarities. They consist of three analogous phases: 1) dedifferentiation (during which the
tissue becomes competent to respond to the organogenic/embryogenic stimulus), 2) induction (during which cells become determined
to form either a root, a shoot or an embryo), and 3) realization (outgrowth to an organ or an embryo). The first phase may
involve a period of callus growth (indirect regeneration), but often cells present in the explant become competent without
cell division or without cell division at a large scale (direct regeneration). In an explant, only very few cells show the
organogenic/embryogenic response. In direct regeneration, the three regenerative pathways start from cells in different tissues.
This is most obvious when the different types of regeneration occur in the same explant. The hormonal trigger for the dedifferentiation
phase is a general one, probably auxin. During the induction phase, each pathway requires specific hormonal triggers. During
the realization phase, hormones should be absent or at low concentration. The successive steps in the regeneration process
coincide with events on the molecular and biochemical levels, but so far no coherent picture has emerged. In particular during
the early stages of regeneration, research on these levels is hampered by a technical problem, viz., the very low proportion
of cells that participate in the process of regeneration. New methods may overcome this problem.
This revised version was published online in July 2006 with corrections to the Cover Date. |
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Keywords: | biotechnology callus micropropagation plant hormones tissue culture |
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