New methods to improve symbiotic propagation of temperate terrestrial orchid seedlings from axenic culture to soil
A. L. Batty A B D , M. C. Brundrett A C , K. W. Dixon A and K. Sivasithamparam BA Science Directorate, Botanic Gardens and Parks Authority, Kings Park and Botanic Garden, West Perth, WA 6005, Australia.
B School of Earth and Geographical Sciences (Soil Science Discipline), Faculty of Natural and Agricultural Sciences, The University of Western Australia, Crawley, WA 6009, Australia.
C School of Plant Biology, Faculty of Natural and Agricultural Sciences, The University of Western Australia, Crawley, WA 6009, Australia.
D Corresponding author. Email: abatty@bgpa.wa.gov.au
Australian Journal of Botany 54(4) 367-374 https://doi.org/10.1071/BT04023
Submitted: 12 February 2005 Accepted: 27 October 2005 Published: 22 June 2006
Abstract
This research aimed to improve the success of soil transfer of terrestrial orchid seedlings after symbiotic germination in the laboratory. Three native Western Australian terrestrial orchids (Caladenia arenicola Hopper & A.P.Brown, Diuris magnifica D.L.Jones and Thelymitra crinita Lindley) were used in this study. The key to improved seedling survival on transfer to soil was found to be the use of an intermediate stage between the Petri dish and soil where larger seedlings were grown in an axenic environment with controlled humidity. There was no apparent benefit of pre-inoculating potting medium with appropriate strains of mycorrhizal fungi for subsequent growth of symbiotic seedlings under glasshouse conditions. Initial survival of seedlings in the glasshouse was high. However, some seedlings failed to produce tubers (from modified roots or droppers) necessary for plant survival through the summer dormancy period, and this caused survival to decrease to 40–60% of the glasshouse-grown seedlings in the first year. The initiation of tubers on droppers by C. arenicola was inversely correlated with leaf size, with smaller plants more likely to form tubers. This suggests that leaves and tubers were competing for resources. However, larger seedlings that did tuberise had larger tubers that were more likely to survive summer dormancy. There was no correlation between leaf size and root tuber size in D. magnifica, but the number of tubers produced was greatest in larger plants. As with C. arenicola, plants of D. magnifica and T. crinita with larger tubers were more likely to survive summer dormancy. Methods developed in this study enable the production of both actively growing symbiotic seedlings and dormant tubers which improve the success of translocation of laboratory-grown terrestrial orchids to field sites.
Acknowledgments
The conservation of terrestrial orchids in Western Australia requires further research to help prevent loss of diversity. Western Power, the supplier of electricity for Perth, recognised the plight of the states threatened flora and provided the necessary financial support for this study to help save critically endangered terrestrial orchids. The first two authors were supported by funding from the ARC.
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