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Background: Orchid seeds are reputed to be relatively short-lived, although comparative studies across a wide range of storage temperatures and moisture contents are few., Objective: To explore how a wide range of temperature and moisture contents affects seed longevity in the orchid genus Cattleya., Materials and Methods: Seeds of three Brazilian orchid species in the genus Cattleya (C. amethystoglossa, C. kautskyana and C. tigrina) were subjected to controlled deterioration (CD) and seeds at three moisture levels were stored for up to 270 days at temperatures as low as -196 degree C. Seed ageing curves were constructed and seed quality assessed as germination level and speed index in vitro, and by tetrazolium staining. Seed morphometry, lipid content and composition were also determined., Results: Seeds were found to be lipid rich (54-70% DW) and short-lived under CD, with P50s varying less than two-fold (42 to 69 h) at 41 degree C. At cold (5 degree C) to ultracold (-196 degree C) temperatures longevity was greatest after pre-drying seeds to 15% RH, with germination varying by c. 6% after 270 days storage at these temperature limits. However, storage at -20 degree C resulted in a 5-46% reduction in germination, indicating a dry-seed sensitivity to conventional seed bank temperature. Ultra-dry (silica gel) and high humidity (82% RH) storage, in combination with various temperatures, compromised viability in one or more species. Overall, seed longevity in C. kautskyana > C. tigrina > C. amethystoglossa, which also reflected the pattern of embryo volume. The prospect that the generally shorter lifespans in orchid seeds may relate to stochastic processes the negative impact of which reach criticality sooner in smaller embryos requires further testing., Conclusion: Further evidence is provided that cryobiotechnology provides a biobanking option for orchid seeds with relatively short lifespans.

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.