Seed-based restoration in dryland environments is commonly limited by low and sporadic rainfall, extreme temperatures, and degraded soils. These challenges are exacerbated in dryland mine restoration sites where species are seeded onto mine waste substrates due to limited availability of topsoil. Native grasses are focal dryland and mine restoration species, though the ability to deliver seeds to targeted sites presents further constraints to seed-based restoration due to complex seed morphology and site attributes. Seed enhancement technologies (SETs) may help to mitigate environmental stressors and improving seed handling. In this study, SETs which promote seedling recruitment and/or address edaphic challenges while also improving seed morphology and handling were tested in four Australian native grasses (Cymbopogon ambiguus, C. obtectus, Eulalia aurea, and Eriachne obtusa). Flash flaming or acid digestion (depending on species), extruded seed pellets with or without the addition of topsoil, and flaming or acid digestion used in combination with extruded pellets (with or without topsoil) were evaluated on topsoil and mine waste substrates. Material treated with either flash flaming or acid digestion tended to produce similar maximum emergence (week 3), final emergence (week 14), and above-ground biomass (week 14) on both topsoil and mine waste when compared to the un-enhanced (‘control’) treatment. Extruded pellets enhanced emergence (maximum and final) on both soil types, though had no effect on biomass. Extruded pellets containing topsoil and/or when used in combination with flash flamed or acid digested florets, provided the most significant benefits to seedling emergence, particularly on mine waste soil. However, SETs were unable to mitigate the detrimental effects of mine waste substrates on seedling biomass. This study shows promise for improving seed-based restoration in post-mine and dryland environments using SETs, though also highlights potential limitations and the importance of understanding long-term (i.e., beyond emergence) plant recruitment outcomes in SET applications.

QuestionsNative grasses are widespread with high commercial value and demand across the restoration sector, though their uptake is often hampered by seed-use challenges. Seed enhancement technologies (SETs) provide a valuable tool for improving plant establishment outcomes for species (such as native grasses) where seed-based approaches are essential to achieve large-scale targets. However, due to the increased investment in resources and time associated with application of SETs, their adoption is dependent on the ability of these treatments to consistently provide benefits to one or more demographic life stages, particularly under field conditions. This meta-analysis addresses the following research question: what are the overall effects of SETs on plant establishment outcomes compared to untreated florets or seeds in native grasses globally?LocationGlobal.MethodsThe effects of six major SET categories (acid treatment, coating, pelleting, flash flaming, priming, and treatment combinations) on germination, emergence, and shoot and root length and biomass were explored. Furthermore, the consistency of the effects of SETs across study types (i.e., laboratory, glasshouse, and field) was investigated.ResultsThe overall effects of SETs on native grasses in this meta-analysis were positive for germination (16% improvement), emergence (22% improvement), and growth (6.42-8.86 cm and 2.26-2.77 g increase in seedling length and biomass, respectively). However, effects ranged from neutral to positive when data were grouped by SET type, with coating, pelleting and priming delivering consistent benefits across multiple life stages, and acid treatments, flash flaming, and combination treatments having mixed effects. This analysis also provided evidence that benefits observed from SET application in laboratory and glasshouse studies are not translating to field environments.ConclusionsOverall, SETs generally had positive effects and can therefore provide a relatively low-risk approach to improving seed-based restoration outcomes in native grasses. Continued SET research focussed on long-term plant establishment outcomes in field environments is needed to further advance SET uptake. Through this meta-analysis, the overall effect of seed enhancement technologies (SETs) on plant establishment outcomes in native grasses compared to untreated florets or seeds was found to be positive. SETs provide a relatively low-risk approach to improving seed-based restoration outcomes in native grasses. Further research focussed on specific SETs, and long-term plant establishment in field environments is needed to advance SET uptake.image

Almost 1 billion hectares of land have been pledged for restoration globally under the UN Decade on Ecosystem Restoration. Seed‐based restoration will be essential to achieve native revegetation targets in a timely and effective manner. However, problematic seed germination, seeding environments, and seed handling can limit our ability to use native seeds in revegetation. Seed enhancement technologies (SETs) are post‐harvest seed treatments, which may improve seed performance and handling, thereby optimizing seed‐use efficiency and success in restoration. We highlight SETs as a restoration tool accessible to anyone and which can also be used to deliver seed‐based restoration at scale. If SETs are to rise to the challenge of restoration targets in the coming decade, improving native seed supply, research efforts, knowledge and data sharing, and collaboration and funding will be essential. These actions are discussed within a roadmap for advancing SETs in the UN Decade on Ecosystem Restoration.

Difficult to handle seed material and poor germination commonly limit the uptake of native grasses in restoration and commercial-scale seeding efforts. Seed enhancement technologies (SETs) offer valuable solutions for improving the handling of seed material and optimising germination. This study considered eight widespread Australian native grasses; two representative of Mediterranean to temperate climates ('cool-climate' species) and six representative of arid to subtropical climates ('warm-climate' species). Through a series of experiments, this study logically selected and applied SET treatments to improve seed handling and germination for each study species. Seed handling was prioritised and addressed using flash flaming and/or acid digestion, while hydropriming was used following seed-handling treatments to enhance germination. Flash flaming and acid digestion were both applied to successfully reduce or remove bulky floret structures while maintaining or improving germination. Flaming at 110 ± 10 °C with continuous exposure for 10 min and acid digestion concentrations of 75-80% with exposure times of 1-2.5 min were generally successful. Sub-optimal concentrations of sulphuric acid often compromised germination. Hydropriming did not improve germination outcomes when applied following flaming or acid digestion. Optimising SETs for germination, emergence and establishment in different environments, and the viability and costs of application on larger seed batches are key considerations for the implementation and upscaling of SETs in the future.

The use of native grasses for both restoration and commercial purposes is becoming increasingly important globally. Many native grasses have limited success in seed‐based restoration (e.g. post‐mine rehabilitation) and commercial industries (e.g. agriculture) due to poor seed germination and handling. Seed‐enhancement technologies can assist in overcoming these barriers. This study aimed to use combinations of seed enhancements to overcome the germination and handling challenges in two dominant Australian native grass species with demand in restoration and commercial industries (Triodia wiseana C.A Gardner and Rytidosperma caespitosum [Gaudich.] Connor & Edgar). Selected enhancements included hydropriming (including inoculation with karrikinolide [KAR1]), flash flaming, and seed coating. Combinations of these seed enhancements allowed improvements in both germination (by up to 55% and 18% for T. wiseana and R. caespitosum, respectively) and floret geometry (flowability, as measured through a mechanized seeder, improved by up to 6‐fold and 17‐fold for T. wiseana and R. caespitosum, respectively), with the order of enhancement application being important. The responses of each species to enhancements corresponded with key biological processes and ecological cues required for recruitment events in nature, such as fire and rainfall events. Triodia wiseana germination was driven by fire‐related cues (i.e. KAR1, flaming), while R. caespitosum germination was highest in response to moisture‐related cues (i.e. hydro‐priming). Responses to seed enhancements (and combinations of) may have implications for the management and scaled use of the targeted species. This can assist in improving the restoration and commercial success of the study species, and potentially other grasses with germination and handling challenges, into the future.

The demand for native grasses is increasing in restoration and agriculture, though their use is often limited due to seed handling challenges. The external structures surrounding the grass seed (i.e., the floret) possess hairs, awns, and appendages which create blockages in conventional seeding equipment. Flash flaming is a patented technology which allows precision exposure of floret material to flames to singe off hairs and appendages. We used two grasses native to Mediterranean ecosystems of Western Australia (Amphipogon turbinatus R.Br. and Neurachne alopecuoidea R.Br.) to evaluate the effects of different flaming techniques on flow properties and germination. Flaming significantly improved flowability in both species and had both neutral (A. turbinatus) and negative (N. alopecuroidea) effects on germination. Flaming torch size influenced germination, though flaming temperature (low or high) and whether this was kept constant or alternating had no effect. The best evaluation of germination following flaming was achieved by cleaning flamed florets to seed and/or germinating in the presence of karrikinolide (KAR1) or gibberellic acid (GA3). We suggest that flaming settings (particularly torch size) require species-specific evaluation and optimisation. Removing seeds from flamed florets and germination testing this material in the presence of stimulants may be a useful protocol for future flaming evaluations.