Floral ontogeny of Brunonia australis (Goodeniaceae) and Calandrinia sp. (Portulacaceae)
Robyn L. Cave A , Colin J. Birch B , Graeme L. Hammer C , John E. Erwin D and Margaret E. Johnston A EA The University of Queensland, School of Land, Crop and Food Sciences, The Centre for Native Floriculture, Gatton, Qld 4343, Australia.
B Tasmanian Institute of Agricultural Research, University of Tasmania, Burnie, Tas. 7320, Australia (Formerly of The University of Queensland, School of Land, Crop and Food Sciences, Gatton, Qld 4343, Australia).
C The University of Queensland, School of Land, Crop and Food Sciences, St Lucia, Qld 4072, Australia.
D Department of Horticultural Science, University of Minnesota, St Paul, MN 55108, USA.
E Corresponding author. Email: m.johnston@uq.edu.au
Australian Journal of Botany 58(1) 61-69 https://doi.org/10.1071/BT09211
Submitted: 10 November 2009 Accepted: 9 December 2009 Published: 11 March 2010
Abstract
Floral ontogeny of Brunonia australis Sm. ex R.Br. (blue pincushion) and Calandrinia sp. (not yet fully classified) was investigated by scanning electron microscopy to assist further efforts for manipulating flowering of these potential floriculture crops. This is the first work to study floral initiation and the stages of flower development for these species. Floral initiation of B. australis commenced 28 days after seed germination when grown at 25/10 or 35/20°C (day/night) under long days (11 h of ambient light at 553 ± 45 µmol m–2 s–1, plus a 5-h night break at <4.5 µmol m–2 s–1). Leaf number at floral initiation reflected differences in the accumulated thermal time between treatments so that about double the number of leaves formed at 35/20°C. This suggested differing temperature responses for leaf and phenological development, and that leaf number was not a good indicator of floral initiation. For Calandrinia sp., floral initiation commenced 47 days after seed germination when grown at 25/10°C. Hot temperatures (35/20°C) inhibited flowering; indicating a vernalisation requirement. For B. australis, the pattern of floret development was centripetal, with flowers organised into five whorls. Four bracts surrounded each flower, whereas the sepals, petals and stamens showed a pentamerous arrangement. A central style was terminated by an indusial stigmatic presenter. Flowers of Calandrinia sp. consisted of four whorls, namely two sepals, 8–10 petals, numerous stamens produced centrifugally and a central syncarpous gynoecium with four stigmatic branches.
Acknowledgements
This project was funded by The Centre for Native Floriculture, The University of Queensland, Rural Industries and Research Development Corporation, and the Queensland Government Department of Tourism, Regional Development and Industry. We thank the staff at The Centre for Microscopy and Microanalysis, The University of Queensland, St Lucia Campus, and particularly Bronwen Cribb, Kim Sewell, Eunice Grinan and Robyn Webb for their help with sample preparation and equipment use. We are also grateful to Christopher Lambrides and Agnieszka Mudge for comments on the manuscript.
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