Agriculture is increasingly challenged by declining crop yields, reduced plant growth, and escalating environmental pressures, thereby intensifying the threat to global food security. While several technologies aim to address these challenges, sustainable and innovative solutions remain urgently needed. Nanotechnology, particularly zinc oxide nanoparticles (ZnO NPs), has emerged as a promising tool to enhance nutrient delivery, minimize fertilizer overuse, and reduce environmental impacts. Unlike previous reviews that broadly summarize nanoparticle applications, this study provides a targeted synthesis of green-synthesized ZnO NPs, highlighting their distinctive physicochemical properties, slow-release nutrient dynamics, and plant–nanoparticle interaction mechanisms. Characterization studies using SEM, TEM, XRD, and FT-IR confirm particle sizes in the nanoscale range (5–100 nm) and highlight structural features that underpin their bioactivity. A key insight of this review is the comparative evaluation of green synthesis approaches using plant-derived materials, which not only reduce hazardous chemicals but also improve cost-effectiveness and sustainability. This study further highlights how ZnO NPs influence seed germination, root development, chlorophyll synthesis, photosynthetic efficiency, and stress tolerance, while emphasizing the dose-dependent trade-offs where excessive concentrations may trigger phytotoxicity. Importantly, this review identifies critical knowledge gaps, including the scarcity of field-based studies, species-specific responses, and long-term ecological assessments. By integrating these limitations with practical strategies for safe application, this study proposes translational pathways to bridge laboratory insights with scalable, field-ready solutions. In summary, this review advances the current understanding of ZnO NPs by uniting perspectives on green synthesis, mechanistic plant responses, and risk–benefit considerations, thereby offering a comprehensive framework for developing eco-friendly nanofertilizers that can sustainably enhance crop productivity and strengthen global food security.
Ashokkumar et al. (Sat,) studied this question.