Cold Plasma Treatment of Sunflower Seeds Modulates Plant-Associated Microbiome and Stimulates Root and Lateral Organ Growth.

Inga Tamošiūnė,Perttu Haimi,Vida Mildažienė,Dalia Gelvonauskienė,Kazunori Koga,Masaharu Shiratani,Danas Baniulis

doi:10.3389/fpls.2020.568924

Abstract

Cold atmospheric pressure (CP) plasma irradiation of seeds has been shown to promote plant growth, but the molecular basis of this phenomenon is poorly understood. In our study, optimum irradiation of common sunflower seeds using a dielectric barrier discharge CP device stimulated growth of sunflower lateral organs and roots by 9–14% compared to the control. Metagenomic analysis revealed that the structure of plant-associated bacterial assembly was greatly modified upon CP treatment and could be attributed to the antimicrobial effect of CP-generated reactive species. The treatment resulted in the domination of spore forming Mycobacterium sp. in the above-ground tissues of the seedlings. While the overall bacterial diversity in the roots was barely affected, the CP-induced shift in microbial composition is the likely basis for the observed seedling root growth stimulation and the long-term effect on lateral organ growth and could be mediated by increase in water uptake and/or direct root signaling. Low amplitude protein abundance differences were detected in the roots of the emerging seedlings that are characteristic to low intensity stress stimuli response and could be linked to the changes in plant-associated microbiome upon CP treatment.

Highlights

Plant seed treatment with high-frequency atmospheric-pressure plasma, known as cold plasma (CP), has been shown to have a potential to enhance agronomic seed quality by surface decontamination, germination enhancement, and promoting plant growth (reviewed by Ohta (Ohta, 2016)
During the 2 weeks of seedling growth, the height of the seedlings remained similar in all experimental groups (Supporting material Figures S1 and S2), the effect of Cold atmospheric pressure (CP) treatment emerged as a difference in size of cotyledons and first true leaf (Figure 1)
The most significant difference in length of cotyledons was reached at day 10 for the CP 4 min group which had an 11.6% ± 2.1% higher mean value compared to the control

Summary

Introduction

Plant seed treatment with high-frequency atmospheric-pressure plasma, known as cold plasma (CP), has been shown to have a potential to enhance agronomic seed quality by surface decontamination, germination enhancement, and promoting plant growth (reviewed by Ohta (Ohta, 2016). UV radiation could have a direct impact on biological systems; the main biologically active constituent of CP is a complex mixture of activated radical species produced by dissociation, excitation and ionization of gas atoms and molecules [mainly molecular oxygen (O2), nitrogen (N2) and water (H2O) in air atmosphere] upon collision with high energy electrons and in subsequent chemical reactions (Turner, 2016; Whitehead, 2016). At relatively low gas temperature and electron energies (2-5 eV), which are characteristic to CP, excitation of N2 molecules and dissociation of O2 in air atmosphere leads to accumulation of ozone (O3) (Whitehead, 2016). Due to the presence of an unpaired electron, OH· radical is highly unstable and could readily oxidize a range of organic compounds (Gligorovski et al, 2015)

Objectives

Methods

Results

Conclusion