Reactive nitrogen species in plasma-activated water: generation, chemistry and application in agriculture

Abstract

The interest in plasma-activated water (PAW) has been greatly increasing during the last few years due to its potential applications in biological and medical sciences, as well as in agriculture and food industry. The effect of PAW is caused by the reactive oxygen and nitrogen species (RONS) generated in the liquid exposed to plasma. This work reviews recent research on the formation of reactive nitrogen species (RNS) in aqueous solutions treated by non-thermal plasma. The most important chemical reactions leading to the production of these active species in the gas and liquid phase, as well as their chemistry in the liquid, correlated with their lifetime are addressed. The literature data on the most important long-lived RNS in PAW (nitrite and nitrate) and the short-lived ones (peroxynitrite and peroxynitrate) are reviewed. The reported results show that their concentrations strongly depend on the type of electrical discharge, gas composition, liquid properties and treatment conditions, and thus tuning the PAW composition over a relatively wide range can be achieved. Results on the possible application of PAW in agriculture are also reviewed. The role of RNS in this area is related to their participation in various signalling pathways in plants, which regulate metabolic processes, plant development, response to stress, etc, and thus can finally lead to enhanced germination and/or faster germination process and increase in plant growth.

Plasma activated water triggers plant defence responses

“…On the other hand, the effect of fosetyl aluminium (FoAl), used as control, was more variable. Moreover, preliminary tests carried out with a synthetic solution with the same concentration of hydrogen peroxide and nitrates and the same pH of PAW, showed the same behaviour of SDW negative control (data not shown), confirming that PAW effect is due to a complex of factors 13 .…”

“…The exposure of water to a cold atmospheric pressure plasma induces the production of both reactive oxygen and nitrogen species in the liquid phase, indeed PAW is characterized by the high concentration of long-lived RONS (e.g. hydrogen peroxide and nitrates) that participate in various signalling pathways in plants, which regulate metabolic processes, plant development, and stress responses 13 .…”

Plasma agriculture: Review from the perspective of the plant and its ecosystem

“…[ 40–47 ] Although there are many plasma‐generated species such as superoxide and NO solvate, most are transient species that react to form the end products H 2 O 2 , NO 2 − , and NO 3 − . [ 48 ] Water is introduced in three ways: as part of the feed gas, in contact with the plasma, or exposed to an effluent. Tachibana et al [ 49 ] demonstrated preferential production of NO 2 − , NO 3 − , and H 2 O 2 through feed gas choice or by plasma discharge method.…”

“…, and NO 3 − . [48] Water is introduced in three ways: as part of the feed gas, in contact with the plasma, or exposed to an effluent. Tachibana et al [49] demonstrated preferential production of NO and reactive species are produced in direct contact with water.…”

The use of plasma‐activated water in viticulture: Induction of resistance and agronomic performance in greenhouse and open field

“…The exposure of water to cold atmospheric‐pressure plasmas (CAPs) induces different reactive oxygen and nitrogen species (RONS) in the liquid phase, leading to the production of plasma‐activated water (PAW), [ 1‐3 ] and it exerts different effects on biological materials, mainly reduction of the bacterial load, [ 4,5 ] and in the agricultural field, leading to the increase of seed germination, [ 6‐11 ] plant growth, [ 12‐14 ] and induction of disease resistance in plants. [ 15‐17 ]…”