New insights of low-temperature plasma effects on germination of three genotypes of Arabidopsis thaliana seeds under osmotic and saline stresses

Maxime Bafoil,Olivier Eichwald,Christophe Dunand,Aurélie Le Ru,Mohammed Yousfi,Nofel Merbahi

doi:10.1038/s41598-019-44927-4

Abstract

In order to investigate the effects of low temperature plasmas on germination of Arabidopsis thaliana seeds, a dielectric barrier discharge device generating the plasma in ambient air was used. To highlight the different plasma effects on the seed surface, saline and osmotic stresses were considered in the case of reference Col-0 seeds and two further seed coat mutants gl2 and gpat5 to better analyse the seed surface changes and their consequences on germination. The GL2 gene encode a transcription factor controlling the balance between the biosynthesis of fatty acids in the embryo and the production of mucilage and flavonoid pigments in the seed coat. The GPAT5 gene encode for an acyltransferase necessary for the accumulation of suberin in the seed coat which is essential for the embryo protection. The testa and endosperm ruptures are identified to note the germination stage. An increasing of germination rate, possibly due to the modification of mantle layers structure, is observed in most of cases, even in presence of saline or osmotic stress, after plasma treatment. Furthermore, we demonstrated that the germination rate of the gl2 mutant seeds is increased by at most 47% after plasma treatment, contrariwise, the germination of gpat5 mutant being initially lower is inhibited by the same plasma treatment. The scanning electron microscopy pictures and confocal microscopy fluorescence both showed changes of the exterior aspects of the seeds after plasma treatment. Considering these results, we assumed that lipid compounds can be found on the surface. To validate this hypothesis, permeability tests were performed, and it was clearly shown that a permeability decrease is induced by the low temperature plasma treatment.

Highlights

Germination is a vital process in plant development
In standard growth conditions without any specific stress, the low temperature plasma treatment increases the speed of testa and endosperm ruptures of the ecotype Col-0 of A. thaliana (Fig. 2A)
The low temperature plasma was generated in ambient air by a dielectric barrier discharge setup while the ecotype Col-0 and the two mutants gl[2] and gpat[5] were analyzed under osmotic and saline stresses to better understand the plasma effects on testa and endosperm ruptures during the early germination step

Summary

Introduction

Germination is a vital process in plant development. It gathers events that result from the water absorption by the quiescent dry seed and end with the lengthening of the embryonic axis[1]. In order to find other substitute methods based more on the use of the low temperature plasmas, the collaboration between plant biology and plasma physics aims to find alternative solutions to increase the germination rate while preserving both the environment and the seed quality. The resulting weakly ionized gas, composed by low densities of energetic electrons with dissociated, excited and ionized species, is called non-thermal plasmas since there is a strong thermal non-equilibrium between the different species. It is called low temperature plasmas because the mean plasma temperature generally does not exceed the body temperature (about 37 °C) allowing the treatment of living cells without any significant thermal effects. Low temperature plasmas contribute to tumour cell reduction[12] and even can partially permeabilize cell membranes for gene transfection applications[13]

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Discussion

Conclusion