Microbial Silver Nanoparticles Enhance the Performance of Maize Plants Cultivated in Naturally Occurring Saline Soil

Abstract

Soil salinity is a major abiotic stress that limits agricultural productivity worldwide. Theaim of this study was to evaluate whether biogenic silver nanoparticles (AgNPs) canmitigate salt stress in maize while preserving soil biological health under realistic soilconditions. Biogenic AgNPs were synthesized using biomolecules from the actinobacterium Streptomyces sp. Z38 and characterized, confirming spherical morphology, colloidalstability, and surface functionalization. Maize plants grown under greenhouse conditionswere treated with biogenic or chemically synthesized AgNPs, and plant performance,oxidative stress responses, and soil biological properties were evaluated. Under salineconditions (6 mS cm−1), biogenic AgNPs markedly improved plant growth, almost fullyrestoring leaf dry weight (165.08 ± 23.68 mg) to values comparable with non-saline controls(171.81 ± 15.00 mg), while chemical AgNPs induced only partial recovery. Biogenic AgNPsalso enhanced antioxidant defenses, increasing catalase activity by ~15% above non-salinelevels and reducing lipid peroxidation from 232.34 ± 31.74 to 102.63 ± 5.75 Eq. MDA g−1.In parallel, chlorophyll a content increased by ~29% relative to non-saline plants, indicating improved photosynthetic performance. Transmission electron microscopy of leavesconfirmed AgNPs internalization, with nanoparticles primarily sequestered in vacuoles.Analyses of experimental soils showed that biogenic AgNPs enhanced microbial enzymaticactivity and respiration, while chemical AgNPs had inhibitory effects. Ecotoxicologicalassays further indicated low soil toxicity following biogenic AgNPs plant treatment, asreflected by high lettuce germination rates. Overall, these findings highlight the potentialof biogenic AgNPs obtained from actinobacteria as sustainable nanobiotechnological toolsto mitigate salt stress in crops while improving soil health. Future field-scale studies willbe required to validate their agronomic applicabilit