Sodium Selenate Under Moderate Salinity Stress Enhances Selenium Concentration and Antioxidant Activity in Dill (Anethum graveolens L.) Across PFAL and Greenhouse Systems

Enhancing selenium (Se) content of aromatic plants addresses micronutrient deficiencies affecting billions. Plants are the primary dietary Se source, so biofortification can enhance Se intake. This study examined the effects of Se biofortification with sodium selenate (5 μM Na₂SeO₄) and moderate salinity stress (10 mM sodium chloride NaCl) on dill (<i>Anethum graveolens</i> L.) grown in a Plant Factory with Artificial Lighting using Nutrient Film Technique (NFT-PFAL) or Floating System (FS-PFAL), and in a Greenhouse with FS (FS-GH). Se biofortification and moderate salinity stress did not affect dill yield in any hydroponic system. Plants under combined Se biofortification and salinity stress (Se + NaCl) showed increased Se concentration in leaves of 31.78 mg kg^-1, 33.12 mg kg^-1, and 23.32 mg kg^-1 in NFT-PFAL, FS-PFAL, and FS-GH, respectively, compared to Se alone. Total phenolics content in leaves increased under Se biofortification with salinity stress across all systems, showing 159.57%, 223.13%, and 82.64% increases over control in NFT-PFAL, FS-PFAL, and FS-GH. Oxidative stress enzymes increased in response to Se, NaCl, and combined treatments across systems. FS-GH showed highest ascorbate peroxidase and guaiacol peroxidase activities, while PFAL systems showed lower but comparable activities. This study demonstrates that combining Se biofortification with moderate salinity stress in hydroponic systems can enhance plant functionality and human nutrition.