Effect of Zinc Oxide Nanoparticles on the Physiological and Biochemical Responses of Coffea arabica L. Exposed to Glyphosate

Glyphosate is widely used for weed control in coffee but can induce physiological alterations due to its lack of selectivity, and indirect spray drift can cause adverse effects, potentially increasing biological impacts upon exposure. In this study, we evaluated the attenuating effect of foliar-applied zinc oxide nanoparticles (ZnO NPs) on <i>C. arabica</i> var. Geisha seedlings exposed to simulated spray concentrations of glyphosate (3.6 and 17.9 g ae L^-1). Exposure caused a marked reduction in chlorophyll content, stomatal conductance, and net photosynthesis, while simultaneously promoting an increase in H₂O₂, MDA, and proline accumulation, reflecting a pronounced redox imbalance and oxidative damage associated with the production of reactive oxygen species (ROS). In contrast, the application of ZnO NPs improved photosynthetic efficiency, increased chlorophyll content, stabilized stomatal aperture, and reduced H₂O₂ and MDA levels in both leaves and roots. Moreover, it enhanced nutrient accumulation, ensuring greater membrane integrity and more efficient ion transport systems under glyphosate exposure. Overall, the ZnO NPs exhibited a notable protective effect by reducing glyphosate-induced phytotoxicity and strengthening the physiological tolerance of <i>C. arabica</i>. These findings support their potential as a sustainable tool to protect coffee crops from glyphosate exposure.