A comprehensive study evaluating the use of ZnO-NPs by functionalizing with Alizarin red S and Zn solubilizing bacteria for Zn fortification of Triticum aestivum, influence of ZnO NPs on ZSB.

One of the most attractive solutions to deal with global Zinc-deficiency problem is Zn-biofortification of wheat using a combination of Zn-solubilizing bacteria (ZSB) and ZnO-nanoparticles. This study compared commonly used Zn-fertilizer, bulk-ZnO and nano-ZnO by functionalizing both with Alizarin Red S (ARS) to track their passage into plant tissues in a ZSB environment. Mung bean and wheat were grown in the presence of these functionalized ZnO. Mung bean tissues exhibit higher intensity of pink/purple color (ARS) when grown with functionalized ZnO-NPs as opposed to bulk-ZnO indicating a higher ZnO-uptake. SEM-EDX analysis of roots and shoots grown with ZnO-NPs revealed a higher Zn-weight% of 0.76% and 0.16%, respectively compared to 0.50% and 0.04%, respectively obtained with bulk-ZnO. This was further confirmed with dithizone staining and AAS analysis. Migration of bulk-ZnO and ZnO-NPs along a soil column was also checked. The results suggested that the use of ZnO can be reduced by half if nano-ZnO is used instead of bulk-ZnO. When the influence of ZnO-NPs on plant-growth-promoting activities of ZSB was checked, low concentration (5 µg/ml) was found to enhance multiple PGP-activities, increase germination and vegetative growth. While high concentration (500 µg/ml) were inhibitory. Cytotoxicity of ZnO was also checked using Allium cepa assays. Higher concentration of ZnO (500 µg/ml) significantly decreased mitotic-index, increased total abnormalities percentage, and dead cells population. This study for the first time reports a holistic approach to understand the passage of ZnO-NP into plant tissues in a ZSB environment and consequent increase in plant growth and Zn content. Supplementary Information: The online version contains supplementary material available at 10.1007/s13205-025-04606-w.