Storage of orchid pollinia with varying lipid thermal fingerprints
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ORIGINAL ARTICLE
Storage of orchid pollinia with varying lipid thermal fingerprints Ceci Castilho Custodio 1 & Nelson B. Machado-Neto 1 Philip T. Seaton 3 & Timothy R. Marks 3
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Rodrigo B. Singer 2
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Hugh W. Pritchard 3
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Received: 13 December 2019 / Accepted: 12 May 2020 # Springer-Verlag GmbH Austria, part of Springer Nature 2020
Abstract Orchid pollinia have the potential to make a valuable contribution to current techniques of germplasm storage and assisted reproduction, yet information regarding their preservation and their ability to remain viable over time is currently limited. Dactylorhiza fuchsii and Disa uniflora were used as models for investigating potential techniques for storing orchid pollinia. Initially, freshly harvested pollinia of Dact. fuchsii were incubated at 25 °C and 100% RH (relative humidity) for up to 7 days and germinated in vitro. For pollinia from both species, moisture sorption isotherms were constructed and thermal fingerprints generated using differential scanning calorimetry (DSC). Pollinia were stored at three temperatures (5, − 18 and − 196 °C) after equilibration at four different RHs (5, 33, 50 and 75%) and germinated. The isotherms and DSC results varied between species. Compared with D. uniflora, pollinia of Dact. fuchsii consistently equilibrated at higher moisture content (MC) for each RH, had less detectable lipids by DSC and had shorter lifespans, remaining viable after 3–4 months only at − 20 and − 196 °C and at low RH (5 and 33%). Both species’ pollinia stored well at − 20 °C and − 196 °C, although there was some evidence of a small loss of viability under cryopreservation. In conclusion, pollen of these two species can be stored successfully for at least 3–4 months, and to maximize the pre-storage quality, it is recommended that fresh pollen is collected from flowers just prior to anthesis. Keywords Pollen germination . Germplasm . Conservation . Orchidaceae
Introduction Orchidaceae is one of the largest Angiosperm families, with around 736 genera and more than 29,199 species (Govaerts et al. 2016) making up around 6.5 to 7% of flowering plant species (Lughadha et al. 2016). Orchids display considerable floral diversity (Cozzolino and Widmer 2005) and are found in a wide range of habitats, from warm and humid tropical moist forests to the low temperatures of the Páramo and the below-freezing winter temperatures of Northern Europe. Handling Editor: Dorota Kwiatkowska * Nelson B. Machado-Neto [email protected] 1
Agronomy College, UNOESTE, Rodovia Raposo Tavares, km 572, Presidente Prudente, São Paulo 19067-175, Brazil
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Departamento Botânica, Instituto de Biociências, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil
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Department of Comparative Plant and Fungal Biology, Royal Botanic Gardens, Kew, Wakehurst Place, Ardingly, West Sussex RH17 6TN, UK
Because of their high endemism rate and complex life cycles, many of them are used as flagship species in support of plant conservation (Seaton et al. 2013, 2015). Ex situ strategies for germp
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