Modulatory Effects of Cold Plasma Seed Priming on the Morphophysiological and Phytochemical Traits of Fennel ( Foeniculum vulgare ) Under Salinity Stress

This study evaluated the effects of salinity stress (0, 60, and 120 mM NaCl) and cold plasma seed priming (0 and 90 s) on morphophysiological, biochemical, and phytochemical traits of medicinal fennel ( Foeniculum vulgare ). Conducted as a factorial experiment in a completely randomized design with three replications in spring 2021, results revealed that salinity significantly impaired plant growth, reducing height, shoot and root biomass, total chlorophyll content, and leaf relative water content (RWC). At 120 mM salinity, severe declines were observed, whereas cold plasma priming mitigated these effects, increasing plant height to 60.53 cm, shoot fresh weight to 64.20 g, and root dry weight to 4.13 g, while restoring total chlorophyll and RWC by 42.2% and 50.67%, respectively. Salinity elevated proline accumulation and superoxide dismutase (SOD) activity, while cold plasma priming modulated these responses and partially reduced malondialdehyde (MDA) accumulation. Phytochemically, phenol and flavonoid levels peaked at 60 mM salinity and were further enhanced by priming. Salinity stress reduced essential oil and seed yields, whereas cold plasma seed priming effectively mitigated these effects. Overall, cold plasma priming enhanced fennel salinity tolerance by improving growth, physiological and biochemical traits, and mineral nutrient uptake, thereby preserving the quantity and quality of valuable secondary metabolites.