Gas plasma treatment as a novel seed technology to release dormancy and improve germination uniformity of vegetable seeds.

Improving the utilization of land has been identified as a global priority in order to increase the sustainability of crop and animal production even in erratic weather due to climate change. Inconsistencies in the release from dormancy of plant seeds result in failure to maximise crop yields from a given land area. This has implications for food security, resource utilization (water, energy, etc.) and the economy as a whole. We propose the treatment of seeds with non-thermal atmospheric gas plasmas (NTAGP) to achieve uniformity in germination. NTAGPs comprise a cocktail of electrons, ions, neutrals, radicals, and excited species and photons. These are generated at ambient pressures and at temperatures within the range of 30-60 C, thus avoiding the possibility of thermal damage. There is mounting interest in the application of such plasmas in the fields of biology and medicine in particular. This includes food treatment (inactivation of surface-borne microorganisms) , bioactive coatings (modifying biomaterial surface properties including tissue permeation) and controlling cell proliferation (wound healing, cancer therapy) .Gas plasmas can be operated over a wide range of scales and can be used to treat large surface areas in food packaging as well as targeting them to confined microscale regions. Some quite rudimentary studies have appeared in which gas plasmas were used to treat seeds contaminated with fungal pathogens. Some effects on germinability were also noted but were not thoroughly investigated largely because seed experts had had no input into these studies. There is evidence that the type and dose of gas plasma determines the effects on seeds, but the underlying mechanisms have not been investigated and are therefore unknown. The PhD research project brings together a team comprising expertise in seed biology and gas plasma technology to undertake a fundamental investigation into the effects of gas plasma treatment on physiological seed responses and their underlying biomechanical, hormonal and molecular processes. This will include modelling the effects of gas plasma on dormancy and germination of vegetable seeds imbibed in abiotic stress conditions, as well as investigating the mechanisms by hormone profiling, transcriptome (RNAseq) ,qRT-PCR, cell-wall immunofluorescence, and reactive oxygen species (ROS) analysis. From a mechanistic point of view seed dormancy and germination are determined by the balance of forces between the embryo growth potential and the restraint weakening of the seed "coats" (endosperm, testa, pericarp). Seed tissue interactions and molecular processes regulated by plant hormones and ROS signaling lead to Biochemical processes with the cell wall as target. Cell-wall remodeling by the direct action of enzymes and apoplastic ROS are required for endosperm weakening and "coat" rupture, embryo growth, radicle emergence, and seedling root growth. Many of these key species including hydroxyl radicals, superoxide, nitrogen oxide (NO) can be generated by plasmas, thereby offering the possibility to influence the natural processes of seed dormancy ,germination, longevity, water uptake and seed coat permeability, storage and quality as well as seedling growth. Moreover, the chemical species comprising gas plasmas can be controlled through gas composition and electrical operating characteristics and therefore gas plasma treatment of seeds could constitute a novel seed enhancement technology important for food security and sustainability. Elsoms Seeds Ltd is a leading UK seed company and germination synchronisation is an area of strategic interest for the company. The PhD student will gain valuable commercial experience during their placement at Elsoms and benefit from working in a multidisciplinary team comprising engineers, biologists and industrialists at Loughborough University, Royal Holloway University of London and Elsoms Seeds.