Synthesis of Fe-loaded mesoporous silica nanoparticles for improving the growth, ion homeostasis, osmolyte, and oxidative status of wheat seedlings under salinity stress

Among the major abiotic stressors, salinity and micronutrient deficiency severely limit wheat production. The present conventional strategies have failed to provide an adequate solution, and the development of sustainable systems for micronutrient delivery in plants in stressed environments is in its infancy. In this context, we attempted to employ mesoporous silica nanoparticles (MSNPs), which have been known to possess stress alleviation properties, for the delivery of Fe, thus addressing the problem of salinity and micronutrient deficiency. In this study, MSNPs and iron-encapsulated MSNPs (Fe-MSNPs) were synthesized and characterized using field emission scanning electron microscopy (FESEM), dynamic light scattering (DLS), and Brunauer-Emmett-Teller (BET) analysis, which confirmed their spherical morphology, nanoscale size, and negatively charged mesoporous surface. Fe-MSNPs exhibited a sustained Fe release (86.83% over 10 days) under physiological conditions, following a non-Fickian diffusion pattern. Furthermore, for the in planta experiments, wheat seedlings were treated with MSNPs and Fe-MSNPs (1 g L-1 and 5 g L-1) simultaneously under different levels of NaCl stress (0, 200, and 300 mM). Increased levels of salinity hindered the growth parameters compared to the untreated plants, but MSNPs and Fe-MSNPs significantly boosted the germination, plant height, and biochemical traits like chlorophyll, sugar, and protein contents. Among the treatments, Fe-MSNPs (5 g L-1) proved to be the most effective across all the NaCl treatments, enhancing K+ retention (1.67-3.29 fold) and reducing Na+ accumulation (1.89-3.18 fold), while also improving the silica-iron uptake and antioxidative defenses. Therefore, these findings underscore a groundbreaking strategy for the potential use of Fe-MSNPs as nanofertilizers, thereby boosting the goal of sustainable agriculture.