Summary
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.
Similar content being viewed by others
References
Chen, H.-R.; Galston, A. W. Growth and development of Pelargonium pith cells in vitro II. Initiation of organized development. Physiol. Plant. 20:533–539; 1967.
Chow, T. W.; Harney, P. M. Crossability between a diploid Pelargonium × hortorum Bailey cultivar and some of its putative ancestral species. Euphytica 19:338–348; 1970.
Croke, J. T.; Cassells, A. C. Dark induction and genetic stability of somatic embryos of zonal geraniums (Pelargonium × hortorum Baily). Angewandte Bot. 71:119–124; 1997.
Gamborg, O. L.; Miller, R. A.; Ojima, K. Nutrient requirements of suspension cultures of soybean root cells. Exp. Cell. Res. 50:151–158; 1968.
Gill, R.; Gerrath, J. M.; Saxena, P. High-frequency direct somatic embryogenesis in thin layer cultures of hybrid seed geranium (Pelargonium × hortorum). Can. J. Bot. 71:408–413; 1993.
Haccius, B. Question of unicellular origin of non-zygotic embryos in callus culture. Phytomorphology 28:74–81; 1978.
Haensch, K.-T. Morpho-histological study of somatic embryo-like structures in hypocotyl cultures of Pelargonium × hortorum Bailey. Plant Cell Rep. 22:376–381; 2004.
Harney, P. M. The origin, cytogenetics and reproductive morphology of the zonal geranium: a review. HortScience 11:189–194; 1976.
Harney, P. M.; Chow, T. W. Crossability between some Pelargonium species. Euphytica 20:286–291; 1971.
Ho, W.; Vasil, I. K. Somatic embryogenesis in sugarcane (Saccharum officinarum L.) I. The morphology and physiology of callus formation and the ontogeny of somatic embryos. Protoplasma 118:169–180; 1983.
Horn, W. Interspecific crossability and inheritance in Pelargonium. Plant Breed. 113:3–17; 1994.
Huetteman, C. A.; Preece, J. E. Thidiazuron: a potent cytokinin for woody plant tissue culture. Plant Cell Tiss. Organ Cult. 33:105–119; 1993.
Hutchinson, M. J.; KrishnaRaj, S.; Saxena, P. K. Morphological and physiological changes during thidiazuron-induced somatic embryogenesis in geranium (Pelargonium × hortorum Bailey) hypocotyl cultures. Int. J. Plant Sci. 157:440–446; 1996.
Hutchinson, M. J.; KrishnaRaj, S.; Saxena, P. K. Inhibitory effect of GA3 on the development of thidiazuron-induced somatic embryogenesis in geranium (Pelargonium × hortorum Bailey) hypocotyl cultures. Plant Cell Rep. 16:435–438; 1997.
Lis-Balchin, M. A chemotaxonomic reappraisal of the Section Ciconium Pelargonium (Geraniaceae). S. African J. Bot. 62:277–279; 1996.
Lis-Balchin, M. A chemotaxonomic study of the Pelargonium (Geraniaceae) species and their modern cultivars. J. Hort. Sci. 72:791–795; 1997.
Madden, J. I. Structural comparisons of somatic embryos, shoots and explants in Pelargonium × hortorum Bailey and three ancestral species (Geraniaceae). M. S., University of Connecticut, Storrs, CT; 1998.
Maheswaran, G.; Williams, E. G. Origin and development of somatic embryoids formed directly on immature embryos of Trifolium repens in vitro. Ann. Bot. 56:619–630; 1985.
Marsolais, A. A.; Wilson, D. P. M.; Tsujita, M. J.; Senaratina, T. Somatic embryogenesis and artificial seed production in zonal (Pelargonium × hortorum) and regal (Pelargonium × domesticum) geranium. Can. J. Bot. 69:1188–1193; 1991.
Mercure, E. W.; Jones, C. S.; Brand, M. H.; Auer, C. A. Anatomy of shoots and tumors of in vitro habituated Rhododendron ‘Montego’ (Ericaceae) cultures with tissue proliferation. Am. J. Bot. 85:616–628; 1998.
Miller, D. Pelargoniums—a gardener’s guide to the species and their hybrids and cultivars. Portland, OR: Timber Press, Inc.; 1996;21–36.
Murashige, T.; Skoog, F. A revised medium for rapid growth and bioassays with tobacco tissue cultures. Physiol. Plant. 15:473–497; 1962.
Newman, P. O.; KrishnaRaj, S.; Saxena, P. K. Regeneration of tomato (Lycopersicon esculentum Mill.): somatic embryogenesis and shoot organogenesis from hypocotyl explants induced with 6-benzyladenine. Int. J. Plant Sci. 157:554–560; 1996.
O’Brien, T. P.; McCully, M. E. The study of plant structure; principles and selected methods. Melbourne: Termarcarphi Pty. Ltd.; 1981:6–82.
Robichon, M.-P.; Renou, J.-P.; Jalouzot, R. Plant regeneration of ivy leaved geranium through shoot organogensis. Plant Cell Tiss. Organ Cult. 49:209–212; 1997.
Stamp, J. A. Somatic embryogenesis in cassava: the anatomy and morphology of the regeneration process. Ann. Bot. 59:451–459; 1987.
Tanksley, S. D.; McCouch, S. R. Seed banks and molecular maps: unlocking genetic potential from the wild. Science 277:1063–1066; 1997.
Visser, C.; Qureshi, J. A.; Gill, R.; Saxena, P. K..Morphoregulatory role of thidiazuron. Plant Physiol. 99:1704–1707; 1992.
Visser-Tenyenhuis, C.; Murthy, B. N. S.; Odumeru, J.; Saxena, P. K. Modulation of somatic embryogenesis in hypocotyl-derived cultures of geranium (Pelargonium × hortorum Bailey) cv Ringo Rose by a bacterium. In Vitro Cell. Dev. Biol. Plant 30:140–143; 1994.
Wilson, D. P. M.; Sullivan, J. A.; Marsolais, A. A.; Tsujita, M. J. Histology of somatic embryogenesis in regal geranium. J. Am. Soc. Hort. Sci. 119:648–652; 1994.
Wilson, D. P. M.; Sullivan, J. A.; Marsolais, A. A.; Tsujita, M. J.; Senaratna, T. Improvement of somatic embryogenesis in zonal geranium. Plant Cell Tiss. Organ Cult. 47:27–32; 1996.
Wilson, H. D.; Payne, J. S. Crop/weed microgametophyte competition in Cucurbita pepo (Cucurbitaceae). Am. J. Bot. 81:1531–1537; 1994.
Yeung, E. C.; Hafizur Rahman, M.; Thorpe, T. A. Comparative development of zygotic and microspore-derived embryos in Brassica napus L. cv Topas. I. Histodifferentiation. Int. J. Plant Sci. 157:27–39; 1996.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Madden, J.I., Jones, C.S. & Auer, C.A. Modes of regeneration in Pelargonium × hortorum (Geraniaceae) and three closely related species. In Vitro Cell.Dev.Biol.-Plant 41, 37–46 (2005). https://doi.org/10.1079/IVP2004605
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1079/IVP2004605