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

Giles Grainge

Research output: ThesisDoctoral Thesis


It is a priority for seed companies to establish uniform seedling emergence within a broad range of abiotic conditions. To achieve this goal, the industry actively pursues the development of innovative seed treatments, and the emergence of utilizing non-thermal atmospheric gas plasma is drawing attention. Plasma, commonly denoted as the 4th state of matter, has been studied in two distinct forms, direct NTAGP (non-thermal atmospheric gas plasma) exposure or expose to gas plasma activated water (GPAW). The former, requires a highly energetic electric field to a gas, causing ionisation, this results in myriad production of energetic reactive species, ions, and free electrons. Whilst the formation of NTAGP at a gas-aqueous interface results in the production of many transient species (OH·,NO2·, NO radicals) and more stable compounds (H2O2, NO3-, NO2-). I first studied different model systems, Nicotiana tabacum, Lepidium Sativum, Arabidopsis thaliana, and their response to NTAGP and GPAW treatment. Treatment with NTAGP of both freshly harvested and after-ripened N. tabacum seeds resulted in no statistical distinction in germination performance; this is true for when treated in a imbibed metabolically active and desiccated metabolically low-active states in stressed environments (temperature, salinity, osmotic). However, I identified imbibition of GPAW lead to significant changes in germination performance of primary dormant A. thaliana accession seeds. In A. thaliana accession col-0 & C24 we demonstrated dormancy breaking with both Air-GPAW and He/O2 GPAW. It was deduced that physiological regulatory mechanisms are affected, with GA3ox1 and Cyp707A2 positively responding to treatment, whilst NCED2 & 9 showed a negative response. Furthermore, highlighted through col-0 mutant lines (nlp1, prt6), effects to germination are not solely due to nitrate signalling, and ROS pathways are likely involved. Biomechanical experiments with L.sativium further highlighted that GPAW has a clear and direct weakening effect on the puncture force of the micropylar endosperm tissue whilst also increasing elasticity. Finally, we proposed a method for how the technology can be scaled for industry, showcasing that the treatment also enhances abiotic stress and ageing tolerance. These findings provide a better understanding of how NTAGP technology can be best utilised in industry, which could significantly impact the reliability of crop yields.
Original languageEnglish
Awarding Institution
  • Royal Holloway, University of London
  • Leubner, Gerhard, Supervisor
  • Steinbrecher, Tina, Supervisor
  • Nakabayashi, Kazumi, Supervisor
Thesis sponsors
Award date1 Apr 2022
Publication statusUnpublished - 2022


  • Seed biomechanics, Endosperm weakening, Germination
  • gas plasma activated water
  • Seed dormancy

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