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Moisture content determination is one of the most important and common assessments made on seeds. It contributes to the estimation of the value of a seed lot in commercial settings and the physiological status of seeds in research and conservation. The most common method for determining seed moisture content is by measuring the change in weight of a sample after drying at a constant temperature for a set period of time. This, however, renders the seeds unusable for other purposes, such as viability testing. Here, we review various methods for assessing the moisture status of seeds, including non-destructive methods. Controlling the amount of water in seeds is just as important as being able to measure the amount of water in seeds. Perhaps most notably, orthodox seeds are normally dried to low moisture content to maintain viability and vigour for longer, with the seeds either stored in breathable containers in a dry environment or sealed in air-tight containers such that they cannot reabsorb water. However, and especially in seed research, we are sometimes interested in having seeds at an intermediate or high moisture content. Hence, in this review we also discuss various ways to adjust the moisture content of seeds.

Societal Impact Statement: Trees are an important part of many ecosystems. The Global Tree Assessment data can be used to focus conservation and restoration efforts for the circa 30% of tree species that are threatened worldwide. The conservation status for the tree flora of Limahuli Valley on Kaua'i Island and a restoration plan for 11 endangered tree species is evaluated in the Global Tree Assessment framework. Lessons learned from Limahuli Valley, one of the most biodiverse valleys in the Hawaiian Islands, provide recommendations for developing long-term sustainable restoration projects. Summary: Based on conservation status assessments of the world's circa 60,000 trees, the Global Tree Assessment (GTA) report revealed that 30% (17,500) of known tree species are currently at risk of extinction. This study aims to evaluate the conservation status for the tree flora of Limahuli Valley and a restoration plan for 11 endangered tree species, in the Global Tree Assessment framework. Of the 117 tree taxa found in Limahuli Valley, 83 (71%) have been assessed for the International Union for the Conservation of Nature (IUCN) Red List and 90% of the assessed tree taxa are threatened. However, only 19 (21%) of these are federally listed and nine tree taxa were not found under their current name or at all in the GlobalTree Portal, suggesting a need for additional curation as well as a conservation status assessment gap. Progress has been made in Limahuli Valley on most restoration goals suggested by the GTA framework, but challenges remain related to both access to material for restoration, mitigation of threats, and understanding correlates of survivorship. Furthermore, trees only constitute about 40% of the flora in Limahuli Valley, and it is important to also consider nontrees including ferns and allies to strive for restoration of an ecosystem as well as the targeted species.

Context Seed banking is the most efficient and cost-effective method of preserving plant germplasm, but not all species can be conserved by conventional practices. Further, restoration of plant populations from seeds often is hindered by a lack of a priori knowledge of seed dormancy and germination requirements. Aims Our objective was to determine seed desiccation, initial freezing tolerance and the dormancy-breaking and germination requirements of Coprosma kauensis, a dioecious shrub endemic to Kauaʻi Island in Hawaiʻi. Methods The effects of temperature and gibberellic acid (GA3) on germination of fresh seeds were tested in light/dark at 15/5, 25/15 and 20/10°C with and without treatment with GA3. To test effects of desiccation and initial freezing on germination, seeds were dried to 15% relative humidity at 15°C and then stored at −20°C. Key results Regardless of incubation temperature and treatment (or not) with GA3, final germination ranged from 78 to 88%; however, time to 50% germination decreased at 20/10°C for seeds treated with 500 ppm GA3. There was no significant difference in final germination percentage between freshly harvested seeds and those desiccated, nor of those desiccated and then subsequently frozen at −20°C. Conclusions Fresh seeds of C. kauensis exhibit a low degree of nondeep physiological dormancy. They can germinate over a range of temperatures, but germination speed is increased by GA3. Fresh seeds are desiccation and freeze tolerant (after 6 months storage). Implications This vulnerable Kauaʻi endemic species easily can be propagated from seeds. Future studies should investigate long-term longevity at various storage temperatures.

The estimated rate of ongoing plant extinctions per year is up to 500 times the background extinction rate, and this is of even greater concern when the species at risk are endangered and endemic. Endemism-scaled richness of vascular plants is 9.5 times higher on oceanic islands than on continents, with land cover change being a primary threat. Hawaiʻi, the most isolated archipelago on Earth, has less than 1% of the land mass of the rest of the United States, it contains over half of all the federally listed endangered species, and has over 250 plant taxa with fewer than 50 individuals remaining in the wild. Therefore, the need for understanding plant conservation practices in Hawaiʻi and beyond are more urgent than ever. Fortunately, seed banking provides the most efficient and cost-effective means of ex situ plant conservation. However, not all species can be conserved by conventional seed banking methods and even in those that can, current genebank standards may not be maximizing seed longevity. Seed traits that lend to a species being able to be conserved long-term by conventional methods include desiccation (i.e. drying) and long-term freeze tolerance (i.e. orthodox seed storage behavior). Although many species of the Hawaiian flora produce desiccation tolerant seeds, some sensitivity to long-term freezing stress (reduced longevity) has been detected in Hawaiian Lobelioideae (Campanulaceae), Cyperaceae, Rubiaceae, and Urticaceae. To date, the Hawaiian flora is the largest reported with this curious intermediate “freeze-sensitive” storage behavior. Recently each of the 256 Kauaʻi endemic taxa were reviewed for the IUCN Red List of Threatened Species and in Chapter I our synthesis of these Red List Assessments showed that 95% were threatened by extinction and 5% were already extinct at least in the wild. This emphasized the need for urgent and effective seed banking intervention in support of global and local plant conservation strategies. Both

BACKGROUND AND AIMS: Island communities, with their long coastlines and increased vulnerability to sea level rise, offer compelling opportunities to investigate salinity tolerance of coastal plants. Seeds are generally more vulnerable than other plant stages to increased stressors. The aim of this study is to characterize salinity tolerance during germination across a diverse pool of 21 species from 14 plant families found in coastal communities throughout the Hawaiian Islands in order to increase our general understanding of coastal plant ecology for conservation and restoration.METHODS: Seeds of each species were exposed to unfiltered/untreated seawater (35 ppt total salinity) and two salinity treatments (10 and 20 ppt) in which the seawater was diluted with distilled water, and germination percent and timing were compared to seeds in a distilled water control. Non-germinated seeds were then tested for recovery germination. We quantified and compared germination percent, time, and recovery among species and across salinity levels and tested for heterogeneity related to seed size, dormancy class, habit, and threatened status.KEY RESULTS: Although salinity tolerance varied considerably among species, salinity exposure generally reduced and delayed germination. The greatest effects were detected at higher salinity levels. Recovery germination overall was higher for seeds that had been exposed to higher salinity. None of the factors we explored emerged as predictors of salinity tolerance except seed mass, which tended to enhance germination at higher salinity.CONCLUSIONS: Species responses to salinity exposure indicate high vulnerability of coastal systems to increased salinity stress, and variability among species could lead to shifts in community assembly and composition under sea level rise. These results can help guide coastal ecosystem conservation and restoration management decisions in the face of climate change.

Understanding the relative longevity of different seed lots, perhaps of different species or genotypes, but also following production under different environments or using different cultivation methods, or following different post-harvest treatments, is relevant to anyone concerned with the retention of seed lot viability and vigour during storage. However, different scientists over the years have used different conditions to assess seed lot longevity, as well as different variables as the measure of 'longevity.' Here, we give some of the backgrounds to how two standard protocols, with an open and closed system respectively, were derived, and explain why we consider p(50), defined as the time during storage when seed lot viability, as measured through a germination test, has declined to 50%, is a suitable longevity trait parameter.

Climate can play a critical role in seed development and germination. Linking seed germination information with environmental variables and provenance may be important in understanding plant community structure and response to climate change, which can help guide conservation planning. Native Hawaiian Metrosideros (Myrtaceae; Modified Letter Turned CommaOhiModified Letter Turned Commaa) is a hyperdiverse species complex that dominates HawaiModified Letter Turned Commai's wet and mesic forests and serves as the most bioculturally important native plant in HawaiModified Letter Turned Commai. In response to Rapid Modified Letter Turned CommaOhiModified Letter Turned Commaa Death, a major threat to native forests caused by introduced fungal pathogens, seed collections of Modified Letter Turned CommaOhiModified Letter Turned Commaa across the state have increased. We used initial seed germination data from recent collections stored in the National Tropical Botanical Garden's Seed Bank to explore if seed germinability is correlated with seed zones and environmental variables. Linear models of the proportion of seed germinated, seed zones, and environmental data revealed that only seed zones were significantly correlated with the proportion germinated. Seed germination was lower for the "Na Pali Valleys" than the "Windward Ranges." Generalized provisional seed zones are a helpful tool for conservation collecting and restoration planning. Germination data routinely collected for seed bank collections provide an easily accessible source of preliminary information for these purposes.

Premise: The Campanulaceae (Lobelioideae) is the Hawaiian plant family with the most endangered and extinct species. Although seeds of Hawaiian lobelioids are desiccation tolerant, the species are exceptional (i.e., they present challenges at various stages of the conventional ex situ conservation chain) due to their generally poor seed survival at the conventional seed-banking temperature (–18°C). Both morphological dormancy (MD) and morphophysiological dormancy (MPD) have been identified in the seeds of other Hawaiian lobelioids; however, the class of dormancy and germination requirements of the Critically Endangered genus Brighamia have not yet been determined. Methods: We measured the embryonic growth in 12-week-old seeds of B. rockii and tested their germination at three temperature regimes (15/5°C, 20/10°C, and 25/15°C) in light and at 25/15°C in darkness. Results: The embryos grew prior to radicle emergence, and the seeds germinated rapidly to high percentages in all tested conditions. Discussion: Whether fresh B. rockii seeds have MD or MPD still needs to be determined; nevertheless, 12-week-old seeds germinated well in light and darkness, and thus the seeds can be used for conservation purposes. Germination in the dark suggests that the species may not form a long-lived soil seed bank in its native habitat.

The International Union for Conservation of Nature's Red List of Threatened Species (IUCN Red List) is the world's most comprehensive information source on the global conservation status of species. Countries, governmental agencies, and conservation organizations increasingly rely on IUCN Red List assessments to develop conservation policies and priorities. Additionally, funding agencies use the assessments as evaluation criteria, and research uses meta-analysis of IUCN Red List data to address fundamental and applied conservation science questions. However, the circa 138,000 assessments included in the IUCN Red List to date represent a fraction of the world's biodiversity and the included assessments are biased in regional and organismal cover. It is unknown what proportion of the unlisted taxa are threatened and with an increasingly global conservation agenda, these biases may impact both conservation priorities, funding, and uses of the data for understanding global patterns. Isolated oceanic islands are characterized by high endemicity, but the unique biodiversity of many islands is experiencing high extinction rates, primarily due to habitat disturbance and loss, competition with invasive species, spread of new diseases, and climate change. The archipelago of Hawai'i has one of the highest levels of endemism of any floristic region with 90% of its 1,367 native vascular plant taxa classified as endemic. Of these, 454 (33%) are listed as Threatened or Endangered under the U.S. Endangered Species Act and by the State of Hawai'i. IUCN Red List assessment of all 256 single island endemic vascular plant taxa of Kaua'i reveals 95% of the flora is threatened with extinction and 5% are already extinct using IUCN Red List criteria. This is the highest extinction risk reported for any flora to date. Comparative analysis suggests that the flora of Hawai'i may be one of the world's most threatened calling for urgent conservation measures of remote oceanic island floras.

Historical herbarium collections have been proposed as a last resort for recovery of extinct plant species not represented in dedicated seed banks or other living conservation collections. For critically endangered plants at the brink of extinction, herbarium collections may also contain historical material from extinct subpopulations representing a species' former range and lost genetic diversity of high value for conservation management. We explored the potential for germination of 81 critically endangered seed plant taxa endemic to the Hawaiian island of Kauaʻi from herbarium specimens in herbarium PTBG of the National Tropical Botanical Garden (NTBG). Of 1250 recorded specimens of wild origin, 138 specimens representing 37 taxa contained mature seeds that could be subjected to germination testing. Seven of these taxa were not represented by any NTBG seed bank collections. Fresh embryos were observed in one seed of each of the three species Schiedea helleri, Schiedea kauaiensis and Viola helena. While potential germination success may be low, we conclude that testing of seeds from herbarium collections should be extended from a focus on strictly extinct taxa to critically endangered taxa, which may not have sufficient representation in seed banks or other living collections of subpopulations and genetic diversity across their wild range.

Questions Islands harbour a disproportionate amount of global plant diversity, yet their unique native assemblages are particularly vulnerable to biological invasions. It is therefore critical to identify the macroecological constraints that mediate spatial distributions of alien species on islands. Here, we examined abundance-occupancy relationships of native and alien woody plant species, and the role of niche properties and functional traits related to dispersal and competition in shaping occupancy and abundance patterns. Location Hawaiian Islands. Methods We calculated relative abundance and occupancy for 64 woody species (42 natives, 22 naturalized aliens), and estimated each species' niche breadth and position. We fitted phylogenetic hierarchical Bayesian models to evaluate abundance-occupancy relationships and the impacts of niche properties and functional traits on occupancy and abundance of native and alien species. Results Our analyses revealed that locally more abundant native species were also more widespread, but that the abundance of alien species was unrelated to their occupancy. Yet, we found evidence that alien species with longer residence times on the Hawaiian Islands were more widespread. While widespread native and alien woody species both had broad niches, widespread alien woody species exhibited a tendency to occur in more marginal niche positions than widespread native woody species. Niche properties did not affect abundances of either native or alien woody species. Traits associated with dispersal capacity and competitive ability had minimal impacts on either occupancy or abundance of native and alien woody species. Conclusions We found that niche properties shape the occupancy but not the abundance of native and alien woody species across Hawaiian forests. Our results suggest that, because of substantial invasion debts, the impacts of alien woody invasions in native forests have yet to fully manifest.