HARNESSING THE POWER OF LIGHTING – A MOLECULAR APPROACH TO UNDERSTANDING HOW GAS PLASMA ACTIVATED WATER (PAW) ALLEVIATES THE PHYSIOLOGICAL DORMANCY OF ARABIDOPSIS THALIANA
Grainge, G.1, Steinbrecher, T.1, Nakabayashi, K.1, Iza, F.2, Sharma, G.2, Dunford, A.3, Kennedy, S.3 and Leubner-Metzger G.1
1School of Biological Sciences, Royal Holloway University of London, Egham, Surrey, United Kingdom
2School of Electronic and Electrical Engineering, Loughborough University, Loughborough, Leicestershire, United Kingdom
3Elsoms Seeds Ltd, Spalding, Lincolnshire, United Kingdom.
Contact: Giles Grainge, www.seedbiology.eu,
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 gas plasma is drawing attention. The formation of non-thermal atmospheric gas plasma at a gas-aqueous interface results in the production of many transient reactive species (OH·, NO2·, NO radicals) and more stable compounds (H2O2, NO3-, NO2-). Several of these chemicals synthesised in gas plasma activated water (PAW) are known to affect seed germination and dormancy, and therefore open an intriguing area of study. Previous reports on PAW have shown significant improvement in germination speed of mung bean and increased tolerance to both salt and osmotic stress, however, no underlying mode of action has been ascertained. This work looks at deciphering which constituent chemicals of the PAW are critical to seed germination performance and whether this is linked with dormancy alleviation of seeds. The stable nitrogen anions, nitrate and nitrite, act through increasing the GA/ABA ratio via activating the nuclear bound transcription factor nin-like protein 8 (NLP8). Nitric oxide is a known dormancy breaking radical which functions as part of the N-rule pathway regulating ethylene response factors. Hydrogen peroxide is an established intercellular signalling molecule associated with dormancy alleviation, and the more reactive, oxygen species O2- and OH. are critical for endosperm weakening. Here we show that PAW can break the dormancy of Arabidopsis thaliana ecotype C24, and describe the effects this has on the expression of genes implicated in the germination regulatory pathways that are influenced by NO3-, NO, H2O2. Furthermore, mutant studies were conducted to reveal which specific underpinning mechanisms PAW influences. Improving our understanding of this novel technology aids the process of establishing its true potential as a new agri-technology. If the improvements to seed germination performance are optimized and shown to be conserved amongst crops seeds, the environmentally friendly aspect and practically of PAW technology would be an enticing prospect for the seed industry.