Seed enhancement research for improving ecological restoration
Many restoration projects attempted in Australia have been rarely cost-effective on a broad scale. For example, many projects rely on planting seedlings and despite showing good results, their employment on a large scale is not affordable. Direct seeding, in theory, may be a more cost-effective alternative, but so far, its success rate has been low (<1-5%) and the use of advanced seed enhancement technologies (SET) limited. Despite SET’s being developed in agriculture/horticulture to improve seed performances, they have not been rigorously transferred into the restoration industry. Their customization on native species could potentially enhance seed germination and recruitment and therefore significantly increase seed-based restoration effectiveness.
Of the available SET’s, seed coating represents a major opportunity for improving the success of restoration by providing more cost-effective and scalable solutions.
Seed coating is commonly used for crop, vegetal and flower species and is a standard procedure in the seed industry. This treatment is performed to:
- modify seed shape and size, increasing homogeneity and improving handling and sowing.
- integrate active ingredient to improve seed germination, seedling survival and ultimately yield.
An analysis of the published scientific literature and information released by seed technology and agrochemical companies, reveals that:
- seed coating is mostly applied to crop and vegetable species but rarely on native seeds.
- most of the active ingredients employed are pesticides, insecticides, and fungicide. The integration of germination promoters and growth regulator are rarely reported.
- colors are widely employed to help discriminate among treatments or variety, but more importantly, as an embellishment tool for marketing purposes.
- in up to 50% of scientific publication, the coating and pelleting material and techniques were performed by private companies and not disclosed; the benefits of seed coating were not always evident.
More transparency by seed companies is needed to prove the effectiveness of seed coating/pelleting and further collaboration with academia could spark innovation and breakthrough such as the novel integration of phytoactive promoters, and extend the application of this technology to seed-based restoration, were the need of effective seed enablement is crucial for achieving landscape-scale restoration (Pedrini et al. 2017).
The main goal of this research project is to increase the understanding of seed coating physical/mechanical proprieties, interaction with the soil, and effects on seed germination, emergence growth.
But seed coating usually represents just the last stage of a longer seed enhancement journey.
Depending on the species, steps might be required prior the coating, to allow for the mechanical process to be performed correctly and for the active ingredients to be delivered evenly. Some seed, for example in grasses, have complex morphological structures, called floret, whose awns, hairs and appendages, makes any mechanical operation challenging. Sometimes those appendages have proven to delay and reduce seed germination.
Therefore, the removal of floret is sometimes a necessary step to advance to the seed enhancement stage.
Different methodologies to remove or reduce the floret have been described in the literature, but never directly compared. In an experiment with four grass species, naturally occurring across the temperate southern regions of Western Australia, floret has been removed:
- manually, crushing the seed gently with rubber mat and gloves.
- using the novel technique of flash flaming (Guzzomi et al. 2016), in which seeds are rapidly and repetitively exposed to a flame until most of the awns and hairs are burned of
- through a process called acid digestion (Stevens et al. 2015), in which seeds are immersed in sulfuric acid until the floret are turned into pulp and seed could easily be extracted.
Among the 3 treatments, both flash flaming and acid digestion have proven to be much faster and efficient than the manual cleaning and when tested for germination, the seeds cleaned with acid have constantly outperformed the once flamed and germinated as good (and sometimes even better) than the manually cleaned seed.
The following step in the seed enhancement process is to test phytoactive compounds that are known for promoting germination, like the smoke derived compound Karrikinolide, and improve stress resistance.
Once those compounds have been tested, the once that have shown beneficial effects will be delivered to the seed via seed coating. The coated seed will then be tested both in control laboratory condition and in the field.
The significance of this research lies in the novelty of researching the application of new and novel high-tech seed based solutions to native species, increasing the knowledge on seed coating physical and mechanical behaviour and the capability to deliver beneficial compounds, increasing seedling emergence and survival in restoration site and improving the overall capacity to restore Australia’s degraded landscapes.
This research could eventually underpin further investigations on SET for native species and provide protocols and advice for native seed industries and restoration practitioners for a more efficient landscape scale restoration in Australia and globally.
Guzzomi AL, Erickson TE, Ling KY, et al (2016) Flash flaming effectively removes appendages and improves the seed coating potential of grass florets. Restor Ecol 24:S98–S105. doi: 10.1111/rec.12386
Pedrini S, Merritt DJ, Stevens J, Dixon K (2017) Seed Coating: Science or Marketing Spin? Trends Plant Sci 22:106–116. doi: 10.1016/j.tplants.2016.11.002
Stevens J, Chivers I, Symons D, Dixon K (2015) Acid-digestion improves native grass seed handling and germination. Seed Sci Technol 43:313–317. doi: 10.15258/sst.2015.43.2.19