Early Dynamics of Zinc-Based Nanofertilizer Absorption in Plants of Glycine max L. (Fabaceae): Short-Term Ultrastructural and Functional Changes and Subcellular Localization

This study investigated the initial absorption dynamics and ultrastructural responses of soybean leaf tissue to foliar application of zinc-based (Zn2+) nanofertilizer, using brightfield light microscopy, electron scanning and transmission microscopy (SEM and TEM), and Raman spectroscopy. Anatomically, no relevant structural changes were detected in the roots or stems in any of the treatments. However, leaves treated with ionic Zn2+ (T1) exhibited thickening of the palisade parenchyma with Zn2+ accumulation in the adaxial epidermis. Samples treated with T2 and T3 revealed epidermal precipitates and intracellular deposits within leaf cells, as evidenced by brightfield optical microscopy and Raman spectroscopy. These aggregates were absorbed and subsequently dissolved, being no longer observed at the 30 min time point. Ultrastructural analysis confirmed the presence of nanofertilizers within the vacuoles and cytoplasm, suggesting absorption and translocation of Zn2+, reinforcing the ability of nano-enabled materials to overcome biological barriers. Our results indicate that zinc-based (Zn2+) nanofertilizers can alter cellular features without evident short-term phytotoxicity. Theoretically, this study provides mechanistic insights into nanoparticle dissolution dynamics, biological barrier penetration, and subcellular compartmentalization pathways in crop plants. From an applied perspective, the rapid absorption (<30 min) and preferential organelle targeting suggest potential for precision nutrient delivery systems, though long-term and efficacy evaluations are required before agricultural deployment can be recommended.