Comparative seed cryopreservation of indonesian and new zealand epiphytic and terrestrial orchids.

BACKGROUND: The atypical seed storage behaviour reported in several orchid species justifies cryopreservation as a complementary conservation strategy to conventional seed banking. OBJECTIVE: This study aimed to assess the seed cryopreservation potential of five orchid species; two tropical epiphytic, Indonesian species (Dendrobium strebloceras, D. lineale), one temperate epiphytic, New Zealand species (D. cunninghamii) and two temperate terrestrial, New Zealand species (Pterostylis banksii, Thelymitra nervosa). MATERIALS AND METHODS: Seeds were cryopreserved by direct immersion in liquid nitrogen (LN) and through the application of a cryoprotectant vitrification method. For the latter, seeds were exposed to Plant Vitrification Solution 2 (PVS2) for 0, 20, 50, and 70 min, at either room temperature or on ice, prior to immersion in LN. RESULTS: Seeds of all the studied species germinated well following direct cooling in LN. There was no difference in the seedling development capability between cryopreserved and non-cryopreserved seeds of both tropical epiphytic species and direct immersion in LN enhanced seed germination and shoot formation in both temperate terrestrials. CONCLUSION: Through a range of analyses of germination and post-germination growth, our study shows the potential for cryopreserving epiphytic or terrestrial orchids from tropical and temperate regions. Doi: 10.54680/fr23410110312.

Seed viability and fatty acid profiles of five orchid species before and after ageing.

Changes in seed lipid composition during ageing are associated with seed viability loss in many plant species. However, due to their small seed size, this has not been previously explored in orchids. We characterized and compared the seed viability and fatty acid profiles of five orchid species before and after ageing: one tropical epiphytic orchid from Indonesia (Dendrobium strebloceras), and four temperate species from New Zealand, D. cunninghamii (epiphytic), and Gastrodia cunninghamii, Pterostylis banksii and Thelymitra nervosa (terrestrial). Seeds were aged under controlled laboratory conditions (3-month storage at 60% RH and 20 °C). Seed viability was tested before and after ageing using tetrazolium chloride staining. Fatty acid methyl esters from fresh and aged seeds were extracted through trans-esterification, and then analysed using gas chromatography-mass spectrometry. All species had high initial viability (>80%) and experienced significant viability loss after ageing. The saturated, polyunsaturated, monounsaturated and total fatty acid content decreased with ageing in all species, but this reduction was only significant for D. strebloceras, D. cunninghamii and G. cunninghamii. Our results suggest that fatty acid degradation is a typical response to ageing in orchids, albeit with species variation in magnitude, but the link between fatty acid degradation and viability was not elucidated. Pterostylis banksii exemplified this variation; it showed marked viability loss despite not having a significant reduction in its fatty acid content after ageing. More research is required to identify the effect of ageing on fatty acid composition in orchids, and its contribution to seed viability loss.

Evaluation of droplet-vitrification, vacuum infiltration vitrification and encapsulation-dehydration for cryopreservation of Syzygium maire zygotic embryos.

BACKGROUND: Syzygium maire is a threatened tree species with limited information on long-term storage options for its recalcitrant seed. OBJECTIVE: To evaluate the cryopreservation of S. maire zygotic embryo axes (EA) using dehydration, encapsulation-dehydration as well as PVS2 vitrification using droplet vitrification (DV) and the novel droplet vacuum infiltration vitrification (DVIV) methods. MATERIALS AND METHODS: Excised naked and sodium alginate encapsulated EA were desiccated to various moisture contents (MC) using a laminar flow cabinet. Moisture content, embryo survival and plantlet formation, before and after cryopreservation, were assessed at 1 h intervals during the desiccation period (0-6 h). The influence of PVS2, using DV and DVIV, was assessed for various desiccation times and temperatures. RESULTS: Encapsulated EA desiccated to 31% and 37% MC survived but no plantlets formed following cryopreservation. Exposure to PVS2 using the DV method had a negative impact on embryo survival and plantlet formation, while DVIV resulted in improved results for non-cryopreserved EA. However, neither PVS2 vitrification method resulted in embryo survival following cryopreservation. CONCLUSION: S. maire embryos are sensitive to desiccation and likely require physical, chemical or a combination of protection methods to increase embryo survival and plantlet formation following cryopreservation.

Comparative Biology of Cycad Pollen, Seed and Tissue - A Plant Conservation Perspective.

Cycads are the most endangered of plant groups based on IUCN Red List assessments; all are in Appendix I or II of CITES, about 40% are within biodiversity 'hotspots,' and the call for action to improve their protection is long-standing. We contend that progress in this direction will not be made until there is better understanding of cycad pollen, seed and tissue biology, which at the moment is limited to relatively few (<10%) species. We review what is known about germplasm (seed and pollen) storage and germination, together with recent developments in the application of contemporary technologies to tissues, such as isotype labelling, biomolecular markers and tissue culture. Whilst progress is being made, we conclude that an acceleration of comparative studies is needed to facilitate the integration of in situ and ex situ conservation programmes to better safeguard endangered cycads.