Introduction: Silver nanoparticles (AgNPs) have garnered significant attention in recent years due to their unique physicochemical properties such as nanoscale size, high surface area-to-volume ratio, and potent antimicrobial activity. These features have led to their extensive use in agriculture, medicine, and industry. Despite their beneficial applications, increasing evidence indicates that AgNPs can induce phytotoxicity by generating reactive oxygen species (ROS), leading to oxidative stress in plants. Oxidative stress disrupts cellular homeostasis, damages membranes, proteins, and nucleic acids, and ultimately reduces plant growth, development, and yield. Given the escalating use of nanomaterials in agroecosystems, understanding and mitigating their adverse effects on crop plants is of paramount importance. Hydrogen sulfide (H₂S) and nitric oxide (NO) are gaseous signaling molecules involved in regulating plant responses to various abiotic stresses. Sodium hydrosulfide (NaHS), an H₂S donor, and sodium nitroprusside (SNP), an NO donor, have been reported to enhance plant tolerance by modulating antioxidant defense systems, improving photosynthetic efficiency, and maintaining cellular redox balance. However, their potential roles in alleviating AgNP-induced stress in economically important crops like soybean remain underexplored. This study aimed to investigate the efficacy of NaHS and SNP in mitigating the detrimental effects of silver nanoparticles on growth, physiological traits, and yield of soybean (Glycine max L. cv. Williams).



Materials and Methods: A factorial experiment was conducted in 2023 based on a randomized complete block design (RCBD) with three replications under field conditions. Treatments consisted of three concentrations of silver nanoparticles (0, 1.5, and 3 g.L⁻¹), three concentrations of NaHS (0, 0.5, and 1 mM), and two concentrations of SNP (0 and 120 µM). Soybean seeds were sown in well-prepared field plots, and treatments were applied as foliar sprays at the early vegetative stage. Growth parameters including dry weights of stem, leaf, and pod; yield components such as number of pods per plant, seeds per pod, and 100-seed weight; and physiological measurements including total chlorophyll content, seed oil percentage, and protein content were recorded at physiological maturity using standard protocols.



Results and Discussion: Application of silver nanoparticles (AgNPs) had a notable impact on the growth, physiological traits, and yield of soybean. Increasing AgNP concentration from 0 to 3 g.L⁻¹ significantly reduced the dry weight of aerial parts (stem, leaves, and pods), as well as several yield-related traits including number of pods per plant, seeds per pod, and 100-seed weight. At the intermediate concentration (1.5 g L⁻¹), most reductions were not statistically significant, suggesting a dose-dependent phytotoxic effect. Exogenous application of sodium hydrosulfide (NaHS) and sodium nitroprusside (SNP) showed a mitigating effect on AgNP-induced stress. The treatment with 1 mM NaHS, regardless of SNP presence, led to the highest dry weight of stem and leaves, indicating enhanced vegetative biomass under stress conditions. However, no treatment showed a statistically significant increase in the number of seeds per pod compared to the control. Grain yield was significantly influenced by the treatments. The highest grain yield (420.3 g m⁻²) was obtained in plants that did not receive AgNPs but were treated with 1 mM NaHS. This represents a 36% increase compared to the untreated control (270 g.m⁻²). In contrast, under 3 g.L⁻¹ AgNP treatment, all combinations of NaHS and SNP resulted in lower yields compared to the control, emphasizing the negative impact of higher AgNP concentrations. Regarding total chlorophyll content, a general decline was observed across all treatments involving 3 g L⁻¹ AgNPs. The lowest value (1.27 g.per g fresh leaf weight) was recorded in the treatment with 0.5 mM NaHS and no SNP, which corresponded to a 22.5% reduction compared to the control. These findings indicate that AgNPs disrupt chlorophyll biosynthesis, while NaHS and SNP may offer partial protection. Seed oil content in control plants was recorded at 16.6%. Among all treatments, only the combination of 0 mM NaHS and 120 µM SNP in the absence of AgNPs resulted in a statistically significant increase in seed oil percentage, reaching 17.35%. This suggests a possible synergistic role of nitric oxide in enhancing lipid metabolism under normal conditions. As for seed protein content, control plants exhibited a mean value of 40.64%. Significant increases were observed under two specific conditions: (i) 0.5 mM NaHS combined with 120 µM SNP without AgNP application, and (ii) under 1.5 g.L⁻¹ AgNP treatment, both the 0 mM NaHS + 0 µM SNP and the 1 mM NaHS + 120 µM SNP combinations resulted in statistically higher protein levels than the control. These results point to complex interactions between nanoparticle stress and signaling molecule treatments, with potential modulation of nitrogen metabolism pathways.

Conclusion: The findings demonstrate that silver nanoparticles, particularly at higher concentrations, exert phytotoxic effects through oxidative stress pathways, adversely affecting soybean growth and yield. Nevertheless, foliar application of sodium hydrosulfide, alone or in combination with sodium nitroprusside, effectively mitigates these effects by enhancing antioxidant capacity, improving photosynthetic pigments, and maintaining seed quality.