Are current seed storage approaches suitable for Macrozamia fraseri (Cycadales), a temperate species used in restoration?

In this study, we focused on understanding key storage traits of seeds from Macrozamia fraseri, an unusual though important species that is impacted by mining. To support current restoration activities, large amounts of seed from M. fraseri have been regularly collected and stored for up to 8 years under standard seed banking conditions (5°C and 20% relative humidity), though in situ recruitment from directly sown seed is poor. To investigate the underlying constraints to germination on demand, we set out to assess the viability of M. fraseri seeds that had been stored in a restoration seed bank from 6 to 66 months. Seed moisture content (MC) (fresh weight basis) was also determined for seeds with different storage histories to ascertain whether M. fraseri seeds display traits (i.e. high MC) that might suggest non-orthodox seed storage behaviour. The youngest seed accession (6 months old) was found to have a high MC (45.8 ± 5.4%-fresh weight basis), and >50% viability. In comparison, older (>30 months old) accessions were observed to have a marked reduction in both seed MC (10-35% MC) and viability (0-29.4%). While preliminary, we conclude that M. fraseri seeds appear to lose viability during conventional storage with younger accessions displaying both a higher seed MC and viability, compared to accessions stored for longer. Given the significance of these results, future research activities are recommended to better understand the interplay between seed MC and storage environment and how this relates to the seasonally dry Mediterranean climate where this species naturally occurs. As well, storage and propagation approaches are proposed to increase success when using M. fraseri for conservation and restorative activities.

Germination physiology of Cochlospermum fraseri (Bixaceae), a deciduous tree from Northern Australia with physical seed dormancy.

Cochlospermum fraseri ('Kapok', Bixaceae) is a deciduous tree widely distributed throughout semi-arid and monsoon tropical northern Australia, and an important species for ecological restoration in the region. We aimed to better understand the seed biology and ecology of C. fraseri to determine the mechanisms by which seed dormancy might be alleviated, and the conditions that support germination to inform the use of this species in restoration. Dormancy breaking treatments (wet heat, dry heat, scarification) commonly applied to species with physical seed dormancy (PY) were tested along with stratification at 5-35°C (nine treatments). Following dormancy alleviation, seeds were germinated at nine temperatures (5 to 40°C) and five water potentials (0 to -0.8 MPa) to understand environmental thresholds that regulate germination physiology in non-dormant seeds. A proportion of seeds (<0.3) lose dormancy naturally in response to warm (25 to 35°C) moist conditions, which dislodges the hypostase plug that prevents water uptake, whilst neither dry (≥100°C) nor wet (~100°C) heat were effective. Dormancy loss was also achieved by exposing seeds to concentrated (95-98% v/v) sulphuric acid for 3-7 hours, after which high proportions (>0.75) of germination were observed. Cochlospermum fraseri seeds possess PY, which is alleviated by seasonal temperatures that occur when soil moisture is high, allowing seeds to employ a risk-adverse strategy and maximize establishment success in episodic environments with stochastic rainfall events. The understanding of dormancy alleviation requirements gained here adds to our knowledge of PY worldwide and recruitment dynamics in the Australian monsoonal tropics and will aid land managers and restoration practitioners by informing both seeding sites and optimal time for in situ sowing as well as the potential capacity of this species to form a persistent soil seed bank.

Indigenous and local communities can boost seed supply in the UN decade on ecosystem restoration.

The UN Decade of Ecosystem Restoration is poised to trigger the recovery of ecosystem services and transform structural injustices across the world in a way unparalleled in human history. The inclusion of diverse Indigenous and local communities to co-create robust native seed supply systems is the backbone to achieve the goals for the Decade. Here we show how community-based organizations have co-developed native seed supply strategies for landscape restoration from the bottom-up. We draw on the interconnections over two decades of seed networks in Brazil and the emerging Indigenous participation in native seed production in Australia. From an environmental justice perspective, we provide a participatory seed supply approach for local engagement, noting local geographical, social and cultural contexts. Meeting large-scale restoration goals requires the connection between local seed production and collaborative platforms to negotiate roles, rights and responsibilities between stakeholders. An enduring native seed supply must include a diversity of voices and autonomy of community groups that builds equitable participation in social, economic, and environmental benefits.

Seed encrusting with salicylic acid: A novel approach to improve establishment of grass species in ecological restoration.

To achieve global ambitions in large scale ecological restoration, there is a need for approaches that improve the efficiency of seed-based interventions, particularly in overcoming the bottleneck in the transition from germination to seedling establishment. In this study, we tested a novel seed-based application of the plant stress modulator compound salicylic acid as a means to reduce seedling losses in the seed-to-seedling phase. Seed coating technology (encrusting) was developed as a precursor for optimising field sowing for three grass species commonly used in restoration programs, Austrostipa scabra, Microlaena stipoides, and Rytidosperma geniculatum. Salicylic acid (SA, 0.1mM) was delivered to seeds via imbibition and seed encrusting. The effects of SA on seed germination were examined under controlled water-limited conditions (drought resilience) in laboratory setting and on seed germination, seedling emergence, seedling growth and plant survival in field conditions. Salicylic acid did not impact germination under water stress in controlled laboratory conditions and did not affect seedling emergence in the field. However, seedling survival and growth were improved in plants grown from SA treated seeds (imbibed and encrusted) under field conditions. When SA delivery methods of imbibing and coating were compared, there was no significant difference in survival and growth, showing that seed coating has potential to deliver SA. Effect of intraspecific competition as a result of seedling density was also considered. Seedling survival over the dry summer season was more than double at low seedling density (40 plants/m2) compared to high seedling density (380 plants/m2). Overall, adjustment of seeding rate according to expected emergence combined with the use of salicylic acid via coating could improve seed use efficiency in seed-based restoration.

Seed Coating: Science or Marketing Spin?

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.

Climate warming could increase recruitment success in glacier foreland plants.

BACKGROUND AND AIMS: Glacier foreland plants are highly threatened by global warming. Regeneration from seeds on deglaciated terrain will be crucial for successful migration and survival of these species, and hence a better understanding of the impacts of climate change on seedling recruitment is urgently needed to predict future plant persistence in these environments. This study presents the first field evidence of the impact of climate change on recruitment success of glacier foreland plants. METHODS: Seeds of eight foreland species were sown on a foreland site at 2500 m a.s.l., and at a site 400 m lower in altitude to simulate a 2·7 °C increase in mean annual temperature. Soil from the site of origin was used to reproduce the natural germination substrate. Recruitment success, temperature and water potential were monitored for 2 years. The response of seed germination to warming was further investigated in the laboratory. KEY RESULTS: At the glacier foreland site, seedling emergence was low (0 to approx. 40 %) and occurred in summer in all species after seeds had experienced autumn and winter seasons. However, at the warmer site there was a shift from summer to autumn emergence in two species and a significant increase of summer emergence (13-35 % higher) in all species except two. Survival and establishment was possible for 60-75 % of autumn-emerged seedlings and was generally greater under warmer conditions. Early snowmelt in spring caused the main ecological factors enhancing the recruitment success. CONCLUSIONS: The results suggest that warming will influence the recruitment of glacier foreland species primarily via the extension of the snow-free period in spring, which increases seedling establishment and results in a greater resistance to summer drought and winter extremes. The changes in recruitment success observed here imply that range shifts or changes in abundance are possible in a future warmer climate, but overall success may be dependent on interactions with shifts in other components of the plant community.