Plasma treated water with metal ions enhances Pak Choi growth, salinity tolerance and accumulation of primary metabolites

Abstract

Salinity stress is a serious environmental threat that has a detrimental impact on agricultural yield and productivity. The effects of plasma-treated water (PTW) and metal ions (M) on Pak Choi growth and salt tolerance genes under salinity stress have not yet been studied. To bridge these gaps, we explored the effects of PTW and PTW + M, prepared using multi-electrode cylindrical dielectric barrier discharged plasma, on Pak Choi seedlings irrigated with 100 mM NaCl solution for 7 d, with an aim to improve plant tolerance to salinity. PTW and PTW + M significantly improved the length and dry weight of shoots and roots, as well as photosynthetic activity, by increasing chlorophyll a and b, pheophytin a and b, total pheophytin, and carotenoid contents. Plant biomass increased maximum of up to 54.4%, shoot length 18.1%, and root length 26.01% in the PTW + M group compared to the control. Furthermore, total chlorophyll and pheophytin content increased 2.16 and 1.55 times after PTW + M irrigation compared to control (DI irrigation) under salinity stress. PTW and PTW + M irrigation further reduced the plasma membrane permeability along with an increase in hydration and intracellular NO and Ca²⁺ levels, with ionic balance and osmotic adjustment genes under salinity stress. Additionally, the treatments improved the primary metabolite accumulation of sugars, sugar alcohols, organic acids, and amino acids, as osmo-protectants, and modulated the adaptation to mitigate salinity stress. In conclusion, PTW and PTW + M irrigation mitigated salinity stress by promoting osmotic adjustment, membrane impermeability, hydration capacity, and the upregulation of salt tolerance genes and primary metabolites in Pak Choi seedlings under salinity stress.