Plasma-activated water (PAW) is a sustainable and innovative alternative for agriculture, especially in controlled environments like greenhouses. Tomato and pepper are key horticultural crops worldwide, with a considerable part of their production in greenhouses. This study examined the effects of PAW irrigation on seed germination, plant growth, and oxidative stress in tomato and bell pepper plants. PAW was activated for up to 15 min using a 1 L capacity plasma reactor based on a glow-type discharge in air with water-cathode. The concentration of nitrogen compounds and the energy efficiency of synthesis obtained with the reactor were moderately high (5.4 mM and 60 nmol/J, respectively). The most notable effects of PAW were observed in bell pepper. The germination percentage in bell pepper increased by up to 26%, while no significant effects were found in tomato seeds. PAW irrigation significantly promoted plant growth, with dry weight increasing by up to 61% in bell pepper and 42% in tomato. Lipid peroxidation results showed no oxidative damage in either crop. The biochemical analysis of antioxidant enzymes (catalase, superoxide dismutase, and guaiacol peroxidase) confirmed that plant defense systems responded adequately to PAW irrigation. These results highlight PAW’s potential as an innovative and eco-friendly alternative in agriculture.

The effect of the application of plasma-activated water (PAW) on the quality and preservation of fresh-cut lettuce is reported in this article. PAW was produced by using a liquid-cathode air discharge. The average (bulk) water temperature was kept at $\sim$ 22 $^{\circ}$ C during the activation procedure and stored at 4 $^{\circ}$ C for up to five days. The pH value, electrical conductivity, and concentrations of H $_{2}$ O $_{2}$ and NO $_{3}^{-}$ in liquid at day 1 were 2.81, 1492 $\mu$ S/cm, and 77.8 and 223.4 mg/L, respectively, with slight variations over the whole storage time. No measurable amounts of NO $_{2}^{-}$ were found. Twenty pieces of lettuce leaves were washed for 1 and 5 min in 1 L of PAW and stored for one and five days. PAW treatments were compared to tap water treatments. The lettuce samples were stored at 4 $^{\circ}$ C and analyzed on days 1, 3, and 7. The chromatic parameter results suggest that PAW treatments significantly reduce the degradation of lettuce chlorophyll from day 3 of refrigerated storage. The lettuce firmness was not significantly modified. The microbiological results of aerobic mesophilic (RAM), enterobacteriaceae, and psychrotrophs populations have shown that lettuce treated with PAW after three days of storage exhibited the strongest inactivation efficiency. Psychrotrophs counts were maintained for up to seven days. Similar inactivation efficiencies were found regardless of the PAW storage time. PAW treatments also favored both the antioxidant capacity FRAP, ABTS, and DPPH, and the total phenolic contents of lettuce at day 7 of storage.

In recent years, one of the fastest growing technological applications in the field of nonthermal plasmas is the degradation of organic contaminants of water. In this work, the degradation of indigo carmine (IC) in water induced by a pulsed positive corona discharge operating in ambient air is reported. Degradation levels in different volumes of IC in solution with distilled water treated with different plasma exposure times immediately after discharge (0 h), and in the postdischarge up to 24 h were examined. To explain the IC discoloration in the postdischarge phase, a chemical model was developed. The stability of the reactive species in solution nitrate (NO₃⁻), nitrite (NO₂⁻) and hydrogen peroxide (H₂O₂), as well as the properties of the solution (electrical conductivity, pH) were also measured. The results suggest that the hydroxyl radical (OH˙) as well as ozone (O₃) are the main oxidizing species during the discharge phase, being primarily formed in the gas phase through plasma-mediated reactions and then transferred to the liquid by diffusion, while the OH˙ production in the bulk liquid through the decomposition of peroxinitrous acid (O=NOOH) plays a major role in the IC degradation during the postdischarge. These results are associated with a noticeably increase in the energy-yield values observed at 24 h post-treatment.

In this study, plasma-activated water (PAW) was generated using a large-volume (5 L) plasma reactor with a quasi-stationary, water-cathode glow-type discharge in atmospheric pressure air. Tap water was activated up to 75 min. PAW exhibited high concentrations of long-lived reactive nitrogen species (RNSs), reaching 8 mM, which is between 4 and 26 times higher than those reported in previous studies. The reactor reached an RNS synthesis efficiency of 61 nmol/J and an RNS production rate of 526 μmol/min, both among the highest reported. PAW was evaluated on tomato and bell pepper. Seedling emergence was determined in a nutrient-free substrate. To assess plant growth, seedlings were transplanted into pots filled with either nitrogen-free or nutrient-rich substrate. PAW-irrigation significantly promoted seedling emergence and leaf expansion, especially in tomato plants. The plant growth-stimulating effects of PAW were more pronounced in nitrogen-free substrate: fresh weight of tomato and bell pepper increased up to 13.1-fold and 2.6-fold, respectively. In contrast, the effect on the nutrient-rich substrate was negligible. Tomato plants grown in the nitrogen-free substrate and irrigated with 75-min PAW reached a dry weight comparable to those grown in nutrient-rich substrate. PAW irrigation did not induce oxidative stress, as confirmed by malondialdehyde (MDA) levels and antioxidant enzyme activity.

Nonthermal discharges in atmospheric pressure air in contact with water produce large amounts of reactive species in the gas phase that can enter into the water by diffusion, thus inducing the formation of secondary reactive species in the liquid phase, including those long-lived species such as NO $_{2}^{-}$ , NO $_{3}^{-}$ , and H $_{2}$ O $_{2}$ . Depending on the controllable parameters of the discharge, the plasma activated water (PAW) may acquire different physicochemical properties, resulting in various applications. Physicochemical measurements of PAW obtained by means of a water-cathode glow-type discharge in atmospheric pressure air operating in open and closed reactor conditions are reported. The discharge was operated in a millisecond pulsed-dc regime at an rms current value of 100 mA and a power of 100 W. A large volume of 1 L of distilled water was treated for 30 min. In both cases, low pH values of $\sim$ 2.5 and very high levels of NO $_{3}^{-}$ (up to 250 mg/L) in PAW were obtained; however, in the closed system, no H $_{2}$ O $_{2}$ was found and high concentrations of nitrite (120 mg/L) were measured, while in the open system, large levels of H $_{2}$ O $_{2}$ were observed (45 mg/L) and no NO $_{2}^{-}$ was found. Likewise, the electrical conductivity value for the closed reactor ( $\approx $ 2000 $\mu $ S/cm) was significantly higher than for the open reactor ( $\approx $ 1000 $\mu $ S/cm). The reasons for these different behaviors in terms of PAW chemistry are discussed. Also, the time stability of PAW was measured.

Chickpea seed quality is highly susceptible to mechanical damage during handling and to rapid deterioration under postharvest storage. Atmospheric pressure Non-Thermal Plasma (NTP) has shown positive effects on seed quality in several species, but its long-term impact on chickpea remains poorly understood. This study evaluated the effect of NTP on the physiological germination process and postharvest deterioration of Cicer arietinum L. (Fabaceae) ’Felipe UNC-INTA’ seeds. Seeds were treated for three minutes with dielectric barrier discharge using O₂ and N₂ as carrier gases. Results showed that NTP optimized the triphasic germination response in embryo, especially in phases II and III, where radicle protrusion occurred earlier in treated (27 and 30 h) than in control (33 h) seeds, accompanied with a partition ratio < 1, indicating the roots’ preferential assimilate allocation. Fungal incidence decreased notably, e.g., Aspergillus decreased from 31% (control) to 11% (N₂) and 10% (O₂). O₂-treated seeds exhibited higher germination (94%) than the control (90%) and an 11% reduction in individual electrical conductivity, indicating enhanced membrane integrity. After six months of storage, both treatments delayed aging, maintaining higher vigor than untreated seeds. Overall, NTP emerges as a promising postharvest technology to enhance and preserve seed vigor and viability in C. arietinum.