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1 January 2005 MODES OF REGENERATION IN PELARGONIUM×HORTORUM (GERANIACEAE) AND THREE CLOSELY RELATED SPECIES
JAREN I. MADDEN, CYNTHIA S. JONES, CAROL A. AUER
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Abstract

Modes of regeneration from hypocotyl explants were studied in Pelargonium×hortorum ‘Scarlet Orbit,’ and three wild relatives, P. zonale, P. alchemilloides, and P. inquinans, on different cytokinin treatments [1 μM thidiazuron (TDZ), 4 μM TDZ, or 8 μM N6-benzylaminopurine (BA) and 1 μM indole-3-acetic acid (IAA)]. P.×hortorum ‘Scarlet Orbit’ and P. zonale showed similar high numbers of easily detached, embryo-like structures in response to 1 μM TDZ; P. alchemilloides and P. inquinans showed weak embryogenic responses to all treatments. To revisit whether P.×hortorum produces somatic embryos, and to examine modes of regeneration in the wild species, the histology of regenerating structures on hypocotyl explants in 1 μM TDZ was examined. Both P.×hortorum and P. zonale produced embryo-like structures from single cell derivatives of epidermal cells. Globular-shaped structures transitioned into heart-shaped structures that had loose attachments to explant surfaces and no vascular connection to the explant. Roots with direct vascular connections to the rest of the embryo-like structures were never observed; root organogenesis appeared to be secondary. We propose that P.×hortorum and P. zonale exhibit partial somatic embryogenesis, in which all of the criteria for somatic embryos are met except formation of a root pole. In both species, explants forming embryo-like structures could also undergo shoot organogenesis, where shoots exhibited a broad base of attachment to the explant and a vascular connection to vascular nodules within the explant. Epidermally derived embryo-like structures were not observed in P. alchemilloides or P. inquinans in response to 1 μM TDZ. Shoot organogenesis occurred in P. alchemilloides but not in P. inquinans.

JAREN I. MADDEN, CYNTHIA S. JONES, and CAROL A. AUER "MODES OF REGENERATION IN PELARGONIUM×HORTORUM (GERANIACEAE) AND THREE CLOSELY RELATED SPECIES," In Vitro Cellular and Developmental Biology - Plant 41(1), 37-46, (1 January 2005). https://doi.org/10.1079/IVP2004605
Received: 4 May 2004; Accepted: 1 September 2004; Published: 1 January 2005
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KEYWORDS
Cytokinin
morphology
partial somatic embryogenesis
Pelargonium alchemilloides
Pelargonium inquinans
Pelargonium zonale
Pelargonium×hortorum
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