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The article focuses on the species-specific ex situ conservation techniques employed to protect five threatened subtropical rainforest species in the Tweed Caldera region of Northern New South Wales and Southern Queensland in Australia. It emphasizes the critical need for tailored conservation strategies, including seed banking, tissue culture, and cryopreservation, due to the unique challenges posed by threats such as climate change, disease, and habitat loss.

Context: Knowledge of seed biology is imperative for effective curation and utilisation of seeds. Aims: We studied the seed biology and reproduction of Geijera parviflora , a species suitable for ecological restoration and ornamental horticulture that has largely been overlooked because of issues with unreliable germination and viability. Methods: Germination in response to dormancy-breaking treatments and soil seed burial, and variation in germination at an inter-population level were assessed for G. parviflora. Seed storability in a conventional seedbank was tested. Floral phenology was assessed. Key results: Germination of untreated and seed coat removed seeds were 0 ± 0.0% and 67 ± 5.5% respectively. Seed germination varied between 21.9 ± 1.8 and 66.6 ± 5.5% at an inter-population level. Seeds buried in soil for 6 months showed 11.7 ± 0.8% germination without any treatment. All seeds buried for 12 months were non-viable. Drying seeds from 11.4 ± 0.19% to 5.79 ± 0.17% moisture content resulted in 40% less germination. Visual observation of floral attributes confirmed the presence of orange-coloured pollen grains for 3.5 ± 0.48 days from floral opening. The stigmatic surface became shiny 3.5 ± 0.21 days after floral opening. Conclusion: Seeds of G. parviflora demonstrate physiological dormancy; treatments that remove seed coat resistance against embryo growth enable germination. Local environmental conditions may explain the inter-population variation in germination. Seeds are short-lived in soil and ex situ seedbank conditions. In soil, seeds release dormancy at the end of first winter, so seeds are available to germinate the following spring/summer with high rainfall. Floral phenology assessment indicated protandrous sequential hermaphroditism, which may reduce the probability of self-pollination in G. parviflora. Implications: This knowledge supports use of G. parviflora in ecological restoration and horticulture. Photograph of flowering Geijera parviflora. This study investigated seed biology and reproduction in the Geijera parviflora to inform conservation actions. Geijera parviflora is a species suitable for ecological restoration and ornamental horticulture, but has largely been overlooked because of issues with unreliable information on its seed biology and reproduction. The results of this study addressed several issues leading to poor seed germination and shed light on the previously unknown seed- storage behaviour of G. parviflora in both in situ and ex situ conditions. Photograph by Ganesha Liyanage. [ABSTRACT FROM AUTHOR]

In physically dormant species, fire-generated heat breaks seed dormancy, with dormancy-breaking temperature thresholds varying among species. Fire-related heating decreases with depth, due to the insulating effects of soil. Concurrently, smaller-seeded species are restricted to germinating near the surface because of limited reserves within such seeds. We hypothesized that dormancy-breaking temperature thresholds of physically dormant species would be higher in smaller-seeded species, to ensure emergence is restricted to shallower soil depths, and that seed survivorship would follow the same pattern. This was tested experimentally for 14 species from south-eastern Australia, and by using a larger data set of species compiled from the literature to assess if any patterns hold across a broader group. Seed size was negatively related to dormancy-breaking temperature thresholds. Mortality at 100 °C showed a positive relationship with seed size. Our findings suggest that small-seeded species are subject to firerelated selection pressure that results in higher dormancy-breaking temperature thresholds and resistant to hotter temperatures, which may act as a depth detection mechanism. By using a broader range of species, we highlight that this relationship is strong and representative of species across a number of phylogenetic groups. [ABSTRACT FROM AUTHOR]

In fire-prone ecosystems, many species regenerate after fire from persistent soil seed banks. Species with physically dormant (PY) seeds have dormancy broken by fire-related heat. The magnitude of post-fire recruitment, to predict response to varying fire severity, is commonly estimated by testing dormancy-breaking temperature thresholds of fresh PY seeds. However, seeds spend years in the soil during the inter-fire period, and determining whether dormancy-breaking thresholds change over time is essential to accurately predict population persistence. Germination of four south-eastern Australian PY species from the Fabaceae family (Acacia linifolia, Aotus ericoides, Bossiaea heterophylla and Viminaria juncea) were studied. Dormancy-breaking temperature thresholds vary inter-specifically and the species represented either high or low dormancy-breaking threshold classes. Freshly collected seeds, and seeds that had been buried in the field or stored in dry laboratory conditions for 6 and 18 months were subjected to a fire-related range of heat treatments (40–100°C). Seed ageing increased germination response to heat treatments, effectively lowering the dormancy-breaking thresholds of three species. The fourth species, A. linifolia, initially had a relatively large non-dormant fraction which was lost as seeds aged, with older seeds then displaying PY broadly similar to the other study species. Patterns of threshold decay were species-specific, with the thresholds and viability of low-threshold species declining more rapidly than high-threshold species. The non-dormant fraction did not increase over time for any of our study species. Instead of increasing their non-dormant fraction, as is common in other vegetation types, these fire-prone PY species displayed a change of dormancy-breaking temperature thresholds. This is an important distinction, as maintaining dormancy during the inter-fire period is essential for population persistence. While changes in sensitivity to dormancy-breaking treatments have previously been reported as seeds age, our study provides the first test of changes to temperature thresholds, which increases the range of germination response from the seed bank under varying fire severity. [ABSTRACT FROM AUTHOR]