Effects of low temperature plasmas and plasma activated waters on Arabidopsis thaliana germination and growth

Abstract

Two plasma devices at atmospheric pressure (air dielectric barrier discharge and helium plasma jet) have been used to study the early germination of Arabidopsis thaliana seeds during the first days. Then, plasma activated waters are used during the later stage of plant development and growth until 42 days. The effects on both testa and endospserm ruptures during the germination stage are significant in the case of air plasma due to its higher energy and efficiency of producing reactive oxygen species than the case of helium plasma. The latter has shown distinct effects only for testa rupture. Analysis of germination stimulations are based on specific stainings for reactive oxygen species production, peroxidase activity and also membrane permeability tests. Furthermore, scanning electron microscopy (SEM) has shown a smoother seed surface for air plasma treated seeds that can explain the plasma induced-germination. During the growth stage, plants were watered using 4 kinds of water (tap and deionized waters activated or not by the low temperature plasma jet). With regards to other water kinds, the characterization of the tap water has shown a larger conductivity, acidity and concentration of reactive nitrogen and oxygen species. Only the tap water activated by the plasma jet has shown a significant effect on the plant growth. This effect could be correlated to reactive nitrogen species such as nitrite/nitrate species present in plasma activated tap water.

Plasma‐activated water to improve the stress tolerance of barley

“…However, germination is not affected by the PAW under optimal conditions in the case of barley, in contrast to lentil, where the synergetic effect of NO 3 − and H 2 O 2 has been emphasized . Although in the present study, the shoot and root length and the fresh weight of the barley seedling at three‐leaf stage is also not affected by the PAW, in Arabidopsis , the leaf number and area and rosette diameter have been increased by it . The protective effect of the PAW against salt stress is demonstrated by the significant increase of the fresh weight of shoot and root in the case of PAW‐hardened seedlings after the recovery period, compared to the nonhardened, but stressed ones.…”

“…Therefore, it is concluded, that the synergy of the NO 3 − and H 2 O 2 is responsible for the efficient growth of the plants. Interestingly, PAW did not influence peroxidase activity and O 2 − levels, as was shown by in situ staining on spinach ( Spinacia oleracea ), radish ( Raphanus sativus var.…”

“…In the last few years, studies have been conducted on selected species to test the effect of PAW on seed germination and plant growth …”

“…Results show that the CAT activity and protein content of seeds decrease during the first 2 days after the phytochrome activation (induced by light pulse after 3 days of imbibition in darkness), whereas on the third day, they increase significantly compared to the control seeds. The increase in CAT activity after 3 days may be a result of the PAW‐induced accumulation of H 2 O 2 observed in Thale cress ( Arabidopsis thaliana ), radish ( Raphanus sativus ), tomato ( Solanum lycopersicum ), and sweet pepper ( Capsicum annum ) . During the first 2 days, H 2 O 2 can be removed by other antioxidants, such as the ascorbate–glutathione (GSH) cycle being an important regulator of H 2 O 2 concentrations …”

“…The PAW‐induced changes in the reactive oxygen species (ROS) probably also influence the concentrations of various antioxidants such as ascorbate, GSH, and carotenoids (Car) that regulate the ROS levels. This possibility has been investigated earlier only for peroxidase in Arabidopsis and catalase in P. tomentosa .…”