Authors: Madden, Jaren; Jones, Cynthia; Auer, Carol

Source: In Vitro Cellular and Development Biology - Plant, Volume 41, Number 1, January 2005 , pp. 37-46(10)

Publisher: Springer

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 N<sup>6</sup>-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.

Keywords: cytokinin; morphology; partial somatic embryogenesis; Pelargonium alchemilloides; Pelargonium inquinans; Pelargonium × hortorum; Pelargonium zonale; shoot organogenesis

Document Type: Research article

DOI: http://dx.doi.org/10.1079/IVP2004605

Affiliations: 1: Email: cjones@uconnvm.uconn.du

Publication date: 2005-01-01

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