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Environmentally cued germination may play an important role in promoting coexistence in Mediterranean annual plant systems if it causes niche differentiation across heterogeneous microsite conditions. In this study, we tested how microsite conditions experienced by seeds in the field and light conditions in the laboratory influenced germination in 12 common annual plant species occurring in the understorey of the York gum-jam woodlands in southwest Western Australia. Specifically, we hypothesized that if germination promotes spatial niche differentiation, then we should observe species-specific germination responses to light. In addition, we hypothesized that species' laboratory germination response may depend on the microsite conditions experienced by seeds while buried. We tested the laboratory germination response of seeds under diurnally fluctuating light and complete darkness, which were collected from microsites spanning local-scale environmental gradients known to influence community structure in this system. We found that seeds of 6 out of the 12 focal species exhibited significant positive germination responses to light, but that the magnitude of these responses varied greatly with the relative light requirement for germination ranging from 0.51 to 0.86 for these species. In addition, germination increased significantly across a gradient of canopy cover for two species, but we found little evidence to suggest that species' relative light requirement for germination varied depending on seed bank microsite conditions. Our results suggest that variability in light availability may promote coexistence in this system and that the microsite conditions seeds experience in the intra-growing season period can further nuance species germination behaviour., (© 2021. The Author(s).)

Trait-based approaches have improved our understanding of plant evolution, community assembly and ecosystem functioning. A major challenge for the upcoming decades is to understand the functions and evolution of early life-history traits, across levels of organization and ecological strategies. Although a variety of seed traits are critical for dispersal, persistence, germination timing and seedling establishment, only seed mass has been considered systematically. Here we suggest broadening the range of morphological, physiological and biochemical seed traits to add new understanding on plant niches, population dynamics and community assembly. The diversity of seed traits and functions provides an important challenge that will require international collaboration in three areas of research. First, we present a conceptual framework for a seed ecological spectrum that builds upon current understanding of plant niches. We then lay the foundation for a seed-trait functional network, the establishment of which will underpin and facilitate trait-based inferences. Finally, we anticipate novel insights and challenges associated with incorporating diverse seed traits into predictive evolutionary ecology, community ecology and applied ecology. If the community invests in standardized seed-trait collection and the implementation of rigorous databases, major strides can be made at this exciting frontier of functional ecology., (© 2018 The Authors. New Phytologist © 2018 New Phytologist Trust.)

Seed coating is the practice of covering seeds with external materials to improve handling, protection, and, to a lesser extent, germination enhancement and plant establishment. With an annual value exceeding US$1 billion dollars, this technology is mostly the preserve of the private research sector, with few links to the scientific community. Here, we analyse the science and industry of seed coating and its contribution to seed establishment and plant performance. We posit that a closer collaboration between academia and industry is critical to realising the potential of seed coating both as a tool for enhancing plant establishment in the face of the challenges posed to agricultural systems and to propel the multibillion-dollar global push for ecological restoration of degraded ecosystems., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Background and Aims: Several ecologically important plant families in Mediterranean biomes have seeds with morphophysiological dormancy (MPD) but have been poorly studied. The aim of this study was to understand the seed ecology of these species by focusing on the prominent, yet intractably dormant Australian genus Hibbertia. It was hypothesized that the slow germination in species of this genus is caused by a requirement for embryo growth inside the seed before germination, and that initiation of embryo growth is reliant upon a complex sequence of environmental cues including seasonal fluctuations in temperature and moisture, and an interplay with light and smoke. Using the results, the classification of the MPD level in species of Hibbertia is considered., Methods: Four species of Hibbertia in winter rainfall south-western Australia were selected. These species, whilst differing in geographic distributions, are variously sympatric, and all are important understorey components of plant communities. The following aspects related to dormancy break, embryo growth and germination were investigated: temperature and moisture requirements; effects of karrikinolide, gibberellic acid and aerosol smoke; and phenology., Key Results: Following exposure to wet/dry cycles at low or high temperatures, embryo growth and germination occurred, albeit slowly in all species at low temperatures when moisture was unlimited, corresponding to winter in south-west Australia. Photo regime influenced germination only in H. racemosa. Aerosol smoke triggered substantial germination during the 1st germination season in H. huegelii and H. hypericoides., Conclusions: Although the study species are con-generic, sympatric and produce seeds of identical morphology, they possessed different dormancy-break and germination requirements. The physiological component of MPD was non-deep in H. racemosa but varied in the other three species where more deeply dormant seeds required >1 summer to overcome dormancy and, thus, germination was spread over time. Embryos grew during winter, but future studies need to resolve the role of cold versus warm stratification by using constant temperature regimes. To include Mediterranean species with MPD, some modifications to the current seed-dormancy classification system may need consideration: (a) wet/dry conditions for warm stratification and (b) a relatively long period for warm stratification. These outcomes have important implications for improving experimental approaches to resolve the effective use of broadcast seed for ecological restoration.

Background and Aims: Karrikinolide (KAR(1)) is a smoke-derived chemical that can trigger seeds to germinate. A potential application for KAR(1) is for synchronizing the germination of weed seeds, thereby enhancing the efficiency of weed control efforts. Yet not all species germinate readily with KAR(1), and it is not known whether seemingly non-responsive species can be induced to respond. Here a major agronomic weed family, the Brassicaceae, is used to test the hypothesis that a stimulatory response to KAR(1) may be present in physiologically dormant seeds but may not be expressed under all circumstances., Methods: Seeds of eight Brassicaceae weed species (Brassica tournefortii, Raphanus raphanistrum, Sisymbrium orientale, S. erysimoides, Rapistrum rugosum, Lepidium africanum, Heliophila pusilla and Carrichtera annua) were tested for their response to 1 µm KAR(1) when freshly collected and following simulated and natural dormancy alleviation, which included wet-dry cycling, dry after-ripening, cold and warm stratification and a 2 year seed burial trial., Key Results: Seven of the eight Brassicaceae species tested were stimulated to germinate with KAR(1) when the seeds were fresh, and the remaining species became responsive to KAR(1) following wet-dry cycling and dry after-ripening. Light influenced the germination response of seeds to KAR(1), with the majority of species germinating better in darkness. Germination with and without KAR(1) fluctuated seasonally throughout the seed burial trial., Conclusions: KAR(1) responses are more complex than simply stating whether a species is responsive or non-responsive; light and temperature conditions, dormancy state and seed lot all influence the sensitivity of seeds to KAR(1), and a response to KAR(1) can be induced. Three response types for generalizing KAR(1) responses are proposed, namely inherent, inducible and undetected. Given that responses to KAR(1) were either inherent or inducible in all 15 seed lots included in this study, the Brassicaceae may be an ideal target for future application of KAR(1) in weed management.

Cyanide is well known for its toxicity towards living organisms. Many plants use cyanide as a defensive agent against herbivores, releasing it through the enzymatic hydrolysis of endogenous cyanogenic compounds. At low concentrations, cyanide has been proposed to have a regulatory role in many plant processes including stimulation of seed germination. However, no ecological role for cyanide in seed germination has been established. In the present study, we show that burning plant material produces the cyanohydrin, glyceronitrile. We also show that, in the presence of water, glyceronitrile is slowly hydrolysed to release cyanide that stimulates seed germination of a diverse range of fire-responsive species from different continents. We propose that glyceronitrile serves as an ecological store for cyanide and is an important cue for stimulating seed germination and landscape regeneration after fires.

Background and Aims: The smoke-derived compound karrikinolide (KAR(1)) shows significant potential as a trigger for the synchronous germination of seeds in a variety of plant-management contexts, from weed seeds in paddocks, to native seeds when restoring degraded lands. Understanding how KAR(1) interacts with seed physiology is a necessary precursor to the development of the compound as an efficient and effective management tool. This study tested the ability of KAR(1) to stimulate germination of seeds of the global agronomic weed Brassica tournefortii, at different hydration states, to gain insight into how the timing of KAR(1) applications in the field should be managed relative to rain events., Methods: Seeds of B. tournefortii were brought to five different hydration states [equilibrated at 15 % relative humidity (RH), 47 % RH, 96 % RH, fully imbibed, or re-dried to 15 % RH following maximum imbibition] then exposed to 1 nm or 1 microm KAR(1) for one of five durations (3 min, 1 h, 24 h, 14 d or no exposure)., Key Results: Dry seeds with no history of imbibition were the most sensitive to KAR(1); sensitivity was lower in seeds that were fully imbibed or fully imbibed then re-dried. In addition, reduced sensitivity to KAR(1) was associated with an increased sensitivity to exogenously applied abscisic acid (ABA)., Conclusions: Seed water content and history of imbibition were found to significantly influence whether seeds germinate in response to KAR(1). To optimize the germination response of seeds, KAR(1) should be applied to dry seeds, when sensitivity to ABA is minimized.

The butenolide, 3-methyl-2H-furo[2,3-c]pyran-2-one (1), has recently been identified as the germination stimulant present in smoke that promotes the germination of seeds from a wide range of plant species. In this paper, we describe the preparation of a number of analogues of 1 and compare their efficacy in promoting seed germination of three highly smoke-responsive plant species, Lactuca sativa L. cv. Grand Rapids (Asteraceae), Emmenanthe penduliflora Benth. (Hydrophyllaceae), and Solanum orbiculatum Poir. (Solanaceae). The results show that the methyl substituent at C-3 in 1 is important for germination-promoting activity while substitution at C-7 reduces activity. In contrast, bioactivity is mostly retained with analogues substituted at C-4 or C-5.

Questions: Annual species have evolved sets of germination cues that are thought to be predictive of the post‐germination environment. In naturally patchy environments, germination microsites often vary considerably in the amount of light they receive and in the diurnal temperature fluctuations they experience. However, whether species' differential germination responses to light and temperature are associated with their spatial patterns of occurrence remains largely untested. Location: Mediterranean‐climate woodlands in Southwest Western Australia. Methods: We surveyed species' occurrences in annual plant communities in 150 quadrats across gradients of canopy cover and litter cover. Nineteen species recorded in this survey were then included in a germination experiment that manipulated (1) Light vs Dark (12 h light or continuous dark) approximating seeds near the soil surface vs those covered by litter and (2) Cold vs Warm temperature regimes (7/18°C and 7/24°C) approximating diurnal fluctuations experienced in shaded vs sun‐exposed microsites, respectively. Results: In the germination experiment, six species had highest germination probabilities in the Light treatment (regardless of temperature), five in Cold + Light, one in Warm + Light, two were indifferent to the treatments, and four did not germinate at all. Binomial linear mixed‐effects models showed that species' maximum responses to light and temperature did not explain their spatial distributions along canopy cover and litter cover gradients, contrary to theoretical expectations of germination being a strong driver of species' occurrences. Conclusions: Despite variation in species' responses to experimental treatments, no association was found with their field microsite associations. Germination strategies in our system were wider than expected for Mediterranean systems. Our results support that germination cues are not strong drivers of microhabitat associations in this system. [ABSTRACT FROM AUTHOR]

Unseasonal fire occurrence is increasing globally, driven by climate change and other human activity. Changed timing of fire can inhibit postfire seedling recruitment through interactions with plant phenology (the timing of key processes, e.g., flower initiation, seed production, dispersal, germination), and therefore threaten the persistence of many plant species. Although empirical evidence from winter‐rainfall ecosystems shows that optimal seedling recruitment is expected following summer and autumn (dry season) fires, we sought experimental evidence isolating the mechanisms of poor recruitment following unseasonal (wet season) fire. We implemented a seed‐sowing experiment using nine species native to fire‐prone, Mediterranean‐climate woodlands in southwestern Australia to emulate the timing of postfire recruitment and test key mechanisms of fire seasonality effects. For seeds sown during months when fire is unseasonal (i.e., August–September: end of the wet winter season), seedling recruitment was reduced by up to 99% relative to seeds sown during seasonal fire months (i.e., May–June: end of the dry summer season) because of varying seed persistence, seedling emergence, and seedling survival. We found that up to 70 times more seedlings emerged when seeds were sown during seasonal fire months compared to when seeds were sown during unseasonal fire months. The few seedlings that emerged from unseasonal sowings all died with the onset of the dry season. Of the seeds that failed to germinate from unseasonal sowings, only 2% survived exposure on the soil surface over the ensuing hot and dry summer. Our experimental results demonstrate the potential for unseasonal fire to inhibit seedling recruitment via impacts on pregermination seed persistence and seedling establishment. As ongoing climate change lengthens fire seasons (i.e., unseasonal wildfires become more common) and managed fires are implemented further outside historically typical fire seasons, postfire seedling recruitment may become more vulnerable to failure, causing shifts in plant community composition towards those with fewer species solely dependent on seeds for regeneration. [ABSTRACT FROM AUTHOR]

Variations in the degree of seed dormancy expressed among conspecific populations provide a basis for improving understanding of the mechanisms controlling species persistence, especially in fire-prone ecosystems. We investigated seed germination of 12 Anigozanthos flavidus populations in response to various fire-related cues that included exposure to karrikinolide, glyceronitrile and smoke water at five temperatures, and the effects of heat shock and its interaction with glyceronitrile. Seeds from populations with deep-degree dormancy (DD) and light-degree dormancy (LD) were subjected to 0–8 months of after-ripening, and the viability of the ungerminated seeds was tested. The degree of seed dormancy and responses to fire-related cues were highly variable among populations. Glyceronitrile and smoke water significantly improved germination in 12 and 8 populations respectively. Heat significantly enhanced germination in all populations, but was less effective when combined with glyceronitrile. After-ripening for 3 months increased germination, whereas ≥4 months led to secondary dormancy or loss of viability. Loss of viability was greater for DD than for LD seeds. Interpopulation variations in the degree of seed dormancy, seed germination requirements for fire-related cues and germination viability in response to after-ripening in A. flavidus contribute to persistence in the variable and unpredictable Mediterranean environment. We investigated seed germination of 12 Anigozanthos flavidus populations in response to fire-related cues and after-ripening durations. We found that dormancy degrees were highly variable among populations. Glyceronitrile and heat significantly improved germination in 12 populations, but was less effective when combined. After-ripening for 4 months or more led to loss of viability, especially for deep-degree dormant populations. [ABSTRACT FROM AUTHOR]

Aims: We aimed to understand the influence of differing soil rock content on seedling emergence of a dominant arid zone grass critical to mine restoration (Triodia pungens R.Br.). We assessed whether emergence mortality resulting from seedlings failing to navigate rocky soils contributes meaningfully to failed recruitment and the maximum emergence depth. Methods: Cleaned seeds and florets (the natural dispersal unit) were buried at discrete depths of 0, 5, 10, 15, 20, 30, and 40 mm in three soil-rock matrices of varying rock content (soil sieved to <5 mm, sieved to <25 mm, or left un-sieved). Results: Rock content reduced emergence of seeds buried below 15 mm and truncated the maximum emergence depth. When seeds were buried at 5 mm; near the modelled 6.0 mm optimal depth, any failure to emerge was largely attributable to failed seed germination. However, when seeds were buried greater than 20 mm, failure of pre-emergent seedlings to reach the surface became the significant factor contributing to failed emergence. Florets failed to recruit under all scenarios. Conclusions: Soil rock content can influence critical seed germination and emergence life stages and therefore the optimal seed recruitment depth. Emergence of deeply (>20 mm) buried seeds is likely restricted by rocks imposing a physical barrier to recruitment. [ABSTRACT FROM AUTHOR]

The methods used to distribute seeds influence the success of a restoration project. We surveyed 183 restoration practitioners from across the globe with the aim of identifying common limitations to the effective use of mechanical direct seeding in large‐scale restoration practice to highlight avenues for design improvement to mechanized seeding equipment. Results from this survey show that direct seeding methods are commonly used for ecological restoration and agree with other studies that suggest the method can achieve results much quicker and cheaper than the alternative of distributing nursery‐grown tube stock. However, this study indicates that current mechanical direct seeding methods lack adequate control of seed sowing depth and spatial distribution and highlight that the inability to sow seeds of varying morphology over complex topography are common limitations to direct seeding. To improve restoration success, engineering improvements to mechanical direct seeders used in large‐scale restoration should focus in particular on addressing issues of precision of delivery for diverse seed types and landscapes. [ABSTRACT FROM AUTHOR]

Background and Aims Substantial evidence supports the hypothesis that morphophysiological dormancy (MPD) is the basal kind of seed dormancy in the angiosperms. However, only physiological dormancy (PD) is reported in seeds of the ANA-grade genus Nymphaea. The primary aim of this study was to determine the kind of dormancy in seeds of six species of Nymphaea from the wet–dry tropics of Australia. Methods The effects of temperature, light and germination stimulants on germination were tested on multiple collections of seeds of N. immutabilis, N. lukei, N. macrosperma, N. ondinea, N. pubescens and N. violacea. Embryo growth prior to hypocotyl emergence was monitored. Key Results Germination was generally <10 % after 28 d in control treatments. Germination percentage was highest at 30 or 35 °C for seeds exposed to light and treated with ethylene or in anoxic conditions in sealed vials of water, and it differed significantly between collections of N. lukei, N. macrosperma and N. violacea. Seeds of N. pubescens did not germinate under any of the conditions. Embryo growth (8–37 % in length) occurred before hypocotyl emergence (germination) in seeds of the five species that germinated. Conclusions Fresh seeds were dormant, and the amount of pregermination embryo growth in seeds of N. lukei and N. immutabilis was relatively small, while in seeds of N. macrosperma, N. ondinea and N. violacea it was relatively large. Thus, seeds of N. lukei and N. immutabilis had PD and those of N. macrosperma, N. ondinea and N. violacea had MPD. Overall, we found that seeds in the most phylogenetically derived clades within Nymphaea have MPD, suggesting that PD is the most likely basal trait within the Nymphaeales. This study also highlights the broad range of dormancy types and germination strategies in the ANA-grade angiosperms. [ABSTRACT FROM AUTHOR]

Morphophysiological dormancy (MPD) is predominantly found in seeds of temperate regions and is uncommon in arid biomes. MPD has been reported in a number of Hibbertia (Dilleniaceae) species of temperate Australia, and in a single species of the arid zone, H. glaberrima. This study aimed to examine the dormancy and germination ecology of seeds of H. glaberrima. Seeds were subjected to temperature stratification treatments designed to mimic summer and autumn conditions in the Pilbara region of Western Australia. Seed germination and embryo growth were measured. We also tested the interaction between temperature stratification and cycles of drying and wetting designed to mimic sporadic rainfall events. All temperature and moisture treatments were tested in combination (+/–) with the smoke-derived chemical karrikinolide (KAR1). Exposing dormant seeds to temperatures suitable for warm stratification (35°C) for ≥ 8 weeks, followed by incubation at 25°C, resulted in significantly higher germination compared with non-stratified seeds. Exposing seeds to dry/wet cycling in conjunction with temperature stratification did not significantly increase germination. Exposure to KAR1 increased germination under most conditions. Once seeds are shed during October to December, they are exposed to hot and sporadically wet conditions over summer, allowing MPD to be overcome in a proportion of the seed population. Seeds may germinate in autumn (March to April), in conjunction with cooler temperatures. More deeply dormant individuals may require more than one summer to overcome dormancy. Similar to other species occurring in fire-prone ecosystems, fire also plays a crucial role in the germination ecology of H. glaberrima. [ABSTRACT FROM AUTHOR]

The use of native plant seeds is fundamental to large-scale rehabilitation and the re-establishment of self-sustaining ecosystems after high-impact mining activity has ceased. However, many of the biological attributes of seeds are often overlooked in large-scale rehabilitation programs. Multi-disciplinary, long-term research collaborations are required to improve seed-based mine rehabilitation. In this paper, we review the steps that BHP Western Australia Iron Ore (WAIO), a large iron ore mining company that operates in the Pilbara bioregion of north-west Western Australia, has taken over the past 9 years to ensure continuous improvement in rehabilitation procedures. We introduce the mining activities that WAIO undertake in the Pilbara, and emphasise specific examples of how research findings have led to incremental improvements in the seed management cycle, growth media management and mine rehabilitation practices. Specifically, we outline how the implementation of structured seed collection and storage programs has created the capacity to maintain high-quality seed stocks sufficient for 3-5 years of future rehabilitation. Research has documented the prevalence of seed dormancy in the flora (>70% of 105 species examined produce dormant seeds), with physical and physiological classes of dormancy most commonly encountered. We discuss the development of seed-treatments such as optimised wet-heat and dry after-ripening that have increased the germination capacity of many previously dormant seed batches. In addition, we highlight how seed enhancement technologies, such as hydro-priming with smoke-derived germination stimulants and polymer seed coating, and a greater understanding of the biological and physical limitations present in the growing environment, have vastly improved seedling emergence performance under field conditions for key framework Triodia species. Ongoing industry support (e.g. construction of a purpose-built rain manipulation shelter) has ensured research in the Pilbara will continue to unpack and resolve the complex challenges associated with seed regeneration of biodiverse native plant communities after mining. [ABSTRACT FROM AUTHOR]

Ecological restoration of grasslands using wild-collected seeds is a major undertaking in many parts of the world. Impediments to effective seed use such as low seed quality, difficult-to-handle and bulky collections of seeds, and seed dormancy and germination constraints contribute to restoration failure. Native grass florets are typically irregular in shape, with appendages that impede efficient mechanized sowing and render agricultural technologies, such as the application of polymer seed coatings, impractical. Our goal was to investigate the application of a novel flaming device to remove floret appendages and improve geometry using Triodia wiseana (C.A. Gardner [Poaceae]), a key framework grass of arid ecosystems in north-western Australia, as a test species. Through the modification of a rotary seed coater with an engineered flaming apparatus, a flash flaming technique was developed. We demonstrate that flash flaming is a highly effective and efficient means of removing floret appendages and subsequently improving geometry. Once flamed, the bulk density of florets was significantly increased, the application of polymer coatings was more effective, and germination was enhanced. The improved floret geometry through flaming therefore shows promise for enhancing the mechanization of direct seeding of grasses. [ABSTRACT FROM AUTHOR]

Reinstating dominant Triodia grassland communities following disturbance has been a focus of arid land restoration practitioners for decades in Australia. Yet, seed quality and variable seed germination have seriously hindered the reestablishment potential of Triodia species to date. This study set out to examine diaspore quality, germination requirements, and seed dormancy in seven Triodia species to identify first, then resolve, germination impediments. Freshly collected florets from all species were cleaned to ensure that each floret contained a viable seed and then evaluated for their initial germination capacity. Very low germination from florets (<10%) indicated the presence of physiological seed dormancy ( PD) in all species. However, germination was significantly improved (up to 57%) with the use of 0.67 µm karrikinolide ( KAR1), and to a lesser degree with 289 µm gibberellic acid ( GA3). When the covering floret structures (i.e. lemma and palea) were removed, germination increased up to 59%, which was further enhanced after exposure to GA3 (up to 66%) and KAR1 (up to 92%). Optimal germination temperatures varied from 20 to 35°C and were species specific. Dry after-ripening ( DAR −30°C and 50% relative humidity [ RH]) of florets and seeds promoted the progressive loss of PD over 12-24 months storage for most species. Germination, dormancy level, and response to incubation temperature differed amongst species, experimental units (florets and seeds), DAR treatments, and after exposure to germination stimulants ( GA3 and KAR1). For use in restoration seeding programs, careful consideration of seed pre-treatments is necessary to improve germination in Triodia species. [ABSTRACT FROM AUTHOR]

Byblidaceae is one of the most poorly studied carnivorous plant families, with seed dormancy and germination biology remaining unresolved. This knowledge deficit has significant conservation and management implications, particularly as the most southerly distributed species, the south-west Western Australian endemic Byblis gigantea, is listed as critically endangered. This study examined the ecophysiology of seed dormancy and germination in B. gigantea in concert with a study of the population dynamics of a single plant community. Mass seedling emergence and plant establishment were observed after a wildfire in 2007 in the natural population, followed by a rapid decline in mature individuals (91%) over a 4-year monitoring period, with almost no inter-fire recruitment (1.4% of all emergence) observed. Seeds possessed a fully developed embryo, and the germination characteristics of fresh seeds classified them as showing physiological dormancy. Seed dormancy was partially alleviated by warm stratification (30 ° C) for 8 weeks prior to incubation at 15 ° C, with c. 40% germination observed. With the additional exposure of seeds to the germination-active chemical in smoke, karrikinolide, the germination of warm-stratified seeds increased to 89%. Seeds also displayed orthodox storage behaviour and appeared to be amenable to long-term seed banking for conservation. These results present the first observation of the stimulation of the germination of a carnivorous plant by a smoke-derived compound. © 2013 The Linnean Society of London, Botanical Journal of the Linnean Society, 2013, 172, 143-152. [ABSTRACT FROM AUTHOR]

Seeds of many coastal plants can survive exposure to seawater and may be dispersed long distances by the ocean. The salt tolerance or avoidance strategies of seeds are poorly understood, even though these traits may fundamentally influence dispersal and recruitment in coastal dunes. This research aimed to demonstrate how salt exclusion or localization within germinating seeds may affect salt tolerance. To determine the response of seeds to external salinity during imbibition (water uptake), it was necessary to quantify uptake and spatially resolve the internal distribution of salt. Flame photometry was used to quantify salt concentration in imbibing seeds and a new application of full-spectrum X-ray mapping allowed visualization of the spatial distribution and relative abundance of salt. As external salinity increased, salt-sensitive Spyridium globulosum ( Rhamnaceae) seeds accumulated sodium and chlorine in the seed embryo, while potassium was increasingly displaced and germination was reduced. Conversely, salt-tolerant Ficinia nodosa ( Cyperaceae) seeds avoided ion uptake and germination was not affected by imbibition in high sodium chloride ( NaCl) concentrations. These results provide insight into mechanisms of salt tolerance/avoidance during imbibition and early germination and suggest that oceanic dispersal can be a viable explanation for the distribution of some plant species. © 2013 The Linnean Society of London, Botanical Journal of the Linnean Society, 2013, 173, 129-142. [ABSTRACT FROM AUTHOR]

Karrikins and cyanohydrins discovered in wildfire smoke stimulate seed germination. Genetic analysis suggests that plants contain endogenous karrikin-type molecules. Cyanohydrins are made by plants to defend against herbivores, but a role in endogenous cyanide signaling should now also be considered.Two new types of signaling compounds have been discovered in wildfire smoke due to their ability to stimulate seed germination. The first discovered were karrikins, which share some structural similarity with the strigolactone class of plant hormones, and both signal through a common F-box protein. However, karrikins and strigolactones operate through otherwise distinct signaling pathways, each distinguished by a specific α/β hydrolase protein. Genetic analysis suggests that plants contain endogenous compounds that signal specifically through the karrikin pathway. The other active compounds discovered in smoke are cyanohydrins that release germination-stimulating cyanide upon hydrolysis. Cyanohydrins occur widely in plants and have a role in defense against other organisms, but an additional role in endogenous cyanide signaling should also now be considered. [ABSTRACT FROM AUTHOR]

Manycoastal plant species are widely distributed, including several pan-global species. Long-distance dispersal and physiological resilience of diaspores (i.e. the plant dispersal unit encompassing the seed and any additional surrounding or attached tissues at dispersal) to adverse environmental conditions are possible contributors to the presence of species over hundreds of kilometres of coastline. Dispersal by water (hydrochory) may occur in coastal habitats. This study investigated diaspore traits considered important for oceanic hydrochorous dispersal, including morphology, buoyancy and survival in seawater, and germination under saline conditions for 13 species common to Holocene dune communities in Western Australia. Of the diaspores of 13 species dominant in this coastal community, 11 floated in seawater, with 7 having >50% of diaspores buoyant after 14 days and some diaspores remaining buoyant for 70 days. Of the 10 species that germinated, diaspores of 9 survived exposure to seawater for up to 70 days. Germination of physiologically dormant seeds contained within indehiscent woody fruits and physically dormant seeds was least affected by time in seawater. The effects of varying concentrations of NaCl (0-500 mM) on germination differed between species, but most were able to recover and germinate when transferred to non-saline water. Three different patterns of salt response were observed. It appears likely a combination of diaspore traits, rather than a single factor, facilitate oceanic hydrochorous dispersal. [ABSTRACT FROM AUTHOR]

Seeds from ten terrestrial orchid species, nine from the south-west Australian biodiversity hotspot ( Caladenia arenicola, Caladenia flava, Caladenia huegelii, Diuris laxiflora, Microtis media ssp. media, Pterostylis recurva, Pterostylis sanguinea, Thelymitra crinita and Thelymitra macrophylla) and one from south-east Australia ( Diuris fragrantissima), were placed into experimental storage to assess their relative longevity and likely optimal conditions for long-term conservation seed banking. Seeds from all species were desiccation tolerant, germinating after drying at 23% relative humidity ( C. arenicola, C. huegelii, P. sanguinea and T. macrophylla) or 5% relative humidity ( C. flava, D. laxiflora, M. media ssp. media, P. recurva and T. crinita) at 23 °C. From automatedly determined moisture adsorption and desorption isotherms at 23 °C, these equate to tolerance of drying to 0.03-0.06 g water g−1 dry weight or 0.013-0.028 g water g−1 dry weight, respectively. Results of storage experiments at a range of moisture contents and temperatures suggest conventional seed bank storage at −18 °C after equilibration at c. 23% relative humidity (at 23 °C) may be suitable for most of the species, although there was higher germination of P. recurva seeds stored at −80 °C and of M. media ssp. media seeds equilibrated at 75% relative humidity. However, there was considerable variation in germination of seeds sampled after different storage periods, making it difficult to identify optimal storage conditions definitively. Results of comparative longevity storage experiments at 60% relative humidity and 40 °C suggest seeds from these orchid species are short-lived compared with non-orchid species, and with Australian species in particular. © 2010 The Linnean Society of London, Botanical Journal of the Linnean Society, 2010, 164, 26-41. [ABSTRACT FROM AUTHOR]

Germination of freshly collected seeds of three sympatric herbaceous species native to fire-prone environments in south-western Australia was significantly improved through the application of novel combinations of dry heat, gibberellic acid, smoke water and dry afterripening. For fresh seeds, combinations of dry heat, gibberellic acid and/or smoke water resulted in >80% germination in Austrostipa elegantissima (Poaceae) and Stylidium affine (Stylidaceae) seeds and >60% germination in Conostylis candicans (Haemodoraceae) seeds, compared with <10% germination of control seeds. For fresh seeds, two broad germination patterns were observed in response to smoke water: nil – low germination for both control and smoke water-treated seeds ( A. elegantissima and S. affine); and a significant smoke response (35%) compared with control seeds (1%) ( C. candicans). During afterripening, high germination for A. elegantissima seeds was achieved following 3 months storage of seeds at equilibrium relative humidities of 23–75%, but seeds stored at 5–13% equilibrium relative humidities took 6–36 months to achieve similar levels of germination. Germination of C. candicans seeds also increased after 3 months storage, to >60% at each equilibrium relative humidity and further increases over time were slight. For S. affine seeds >60% germination was achieved only after 36 months storage at 50% equilibrium relative humidity. Seeds from all three species were smoke-responsive at some point, but the interaction/effects of afterripening on the smoke response varied significantly between species. This study highlights an apparent effect of seed dormancy status on response to smoke and a surprisingly high level of ecological variation in pre-germination requirements (cues) for these co-occurring species that may relate to variation(s) in microsite selection forces operating on the soil seed bank of the different species. [ABSTRACT FROM AUTHOR]

The effects of after-ripening (storage under warm, dry conditions) on seed germination was examined in six plant species from the arid zone of Western Australia with the aim of improving germination and germination rate for rehabilitation objectives. Study species ( Acanthocarpus preissii, Anthocercis littorea, Dioscorea hastifolia, Eremophila oldfieldii, Thryptomene baeckeacea and Zygophyllum fruticulosum) were selected based on diverse plant habits, seed types and requirements for rehabilitation. After-ripening was investigated by adjusting seed moisture content to 13 and 50 equilibrium relative humidity (eRH) at 23 °C and storing seeds at two temperatures (30 and 45 °C) from 1 to 18 months. Following storage, seeds were incubated in water, gibberellic acid (GA3) or karrikinolide (KAR1; the butenolide, 3-methyl-2 H-furo[2,3- c]pyran-2-one). All after-ripening conditions increased germination percentage and rate of A. littorea and D. hastifolia, with A. littorea only germinating when treated with GA3 or KAR1. The germination of Z. fruticulosum was dependent on after-ripening temperature and seed moisture content. After-ripening had a limited effect on the remaining three species. The restoration implications of the findings are discussed. © 2009 The Linnean Society of London, Botanical Journal of the Linnean Society, 2009, 161, 411–421. [ABSTRACT FROM AUTHOR]

• We assessed regeneration from seeds of Australian Nymphaea under increased salinity. • Significant reductions in seed germination were observed at ≥100 mM NaCl. • Early seedling growth was also significantly affected by salinities ≥100 mM. • Increased salinity in freshwater wetlands will reduce habitat for Nymphaea. Coastal, freshwater wetlands in northern Australia are at risk of increased saltwater intrusion associated with sea-level rise, which threatens the persistence of numerous freshwater plant species by increasing salinity. Waterlilies (Nymphaea) are widespread in northern Australia, and their loss from these wetlands will be detrimental, both ecologically and culturally. This study aimed to define the regeneration tolerance of Nymphaea to increased salinity through quantifying the effects of salinity on seed germination and early seedling growth in four Nymphaea species. Seed germination and seedling growth were assessed under a gradient of salinity concentrations. Seeds that did not germinate after salinity exposure were assessed for their ability to recover in fresh water. For all species, there was a significant reduction in germination when seeds were exposed to salinities of ≥100 mM NaCl. Total seedling biomass was less sensitive to increasing salinity than germination, however declined significantly across all species at salinities ≥100 mM NaCl. Ungerminated seeds from all salinity treatments displayed some degree of recovery when transferred to fresh water. For the majority of species, however, seed germination of these transferred seeds never reached the percentages observed in the non-saline controls. For most species of Nymphaea , any salinization event reaching ≥100 mM NaCl will significantly reduce recruitment from seeds, irrespective of whether saline water is flushed from the system. The predicted future increases of saltwater intrusion into coastal freshwater wetlands in Northern Australia associated with global sea-level rise will likely result in significant habitat loss for many Nymphaea species. [ABSTRACT FROM AUTHOR]

The seagrass, Halophila ovalis plays an important ecological and sediment stability role in estuarine systems in Australia with the species in decline in many sites. Halophila ovalis is a facultative annual, relying mainly on recruitment from the sediment seed bank for the annual regeneration of meadows. Despite this, there is little understanding of seed dormancy releasing mechanisms and germination cues. Using H. ovalis seed from the warm temperate Swan River Estuary in Western Australia, the germination ecology of H. ovalis was investigated by simulating the natural seasonal variation in water temperatures. The proportion of germinating seeds was found to be significantly different among temperature treatments (p < 0.001). The treatment with the longest period of cold exposure at 15 °C followed by an increase in temperature to 20–25 °C (i.e. cold stratification) had the highest final mean germination of 32% and the fastest germination rate. Seeds exposed to constant mean winter temperatures of 15 °C had the slowest germination rate with less than two seeds germinating over 118 days. Thus temperature is a key germination cue for H. ovalis seeds and these data infer that cold stratification is an important dormancy releasing mechanism. This finding has implications for recruitment in facultative annual species like H. ovalis under global warming since the trend for increasing water temperatures in the region may limit seed-based recruitment in the future. [ABSTRACT FROM AUTHOR]

Abstract: Karrikins are a chemically defined family of plant growth regulators discovered in smoke from burning plant material. Karrikins are potent in breaking dormancy of seeds of many species adapted to environments that regularly experience fire and smoke. The recent discovery that karrikins trigger seed germination and control seedling growth in taxa that would rarely experience fire indicates that their significance could extend far beyond fire ecology. This is exemplified by new studies showing that seeds of Arabidopsis thaliana respond sensitively and specifically to karrikins in smoke. These exciting discoveries might be explained if karrikins are produced in the environment by processes other than fire, such as by chemical or microbial degradation of vegetation in response to disturbance of the soil or removal of the plant canopy. Another hypothesis is that plants contain endogenous karrikins that function naturally in the control of seed germination and that species from fire-prone habitats have evolved to respond also to exogenous karrikins. A variant on this hypothesis is that karrikins mimic endogenous plant hormones such as terpenoids that control seed germination. The evidence for these hypotheses is discussed, but whatever the explanation karrikins are now firmly established as an important family of naturally occurring plant growth regulators. [Copyright &y& Elsevier]

In degraded drylands, post-disturbance native plant community re-establishment is almost exclusively conducted using seeds. These restoration efforts are challenging, in large part as a result of a limited understanding of seed dormancy and germination traits. In this paper, we characterize these traits for four herbaceous perennials (Asteraceae) that are widely distributed and highly desired in the restoration of ecologically imperiled drylands of North America. We assess baseline germination and the effects of chemical stimulants across a suite of temperatures and quantify the influence of (1) cold stratification, (2) dry after-ripening, and (3) dry cold storage on germination. Three months of cold stratification achieved near-maximum dormancy alleviation for all species. Exposure to warmer temperatures following stratification increased germination further, reducing the required stratification length. Across all species, at least a third of seeds maintained at 3 ± 2 °C germinated, suggesting that in situ germination occurs in late winter or early spring. Changes in the thermal germination envelope were species-dependent, indicating different germination niches and strategies for population persistence. Dry after-ripening and cold storage improved germination, but responses were highly variable across species, temperature, and time. Chemical stimulants promoted germination in three species and may be an alternative to cold stratification or after-ripening. • Seeds of many perennial Asteraceae are physiologically dormant at maturity. • Congeners of these species differ in germination niches and bet-hedging strategies. • Cold stratification is the primary driver of dormancy loss for these species. • Dry after-ripening and dry cold storage can promote partial dormancy loss. • Alleviating seed dormancy has the potential to enhance plant recruitment. [ABSTRACT FROM AUTHOR]