Zinc biofortification and implications on growth, nutrient efficiency, and stress response in Amaranthus cruentus through soil application of biosynthesized nanoparticles

Abstract

The study investigates the effects of treating Amaranthus cruentus (red amaranth) plants with biosynthesized zinc nanoparticles (Zn Nps) and zinc sulfate at concentrations of 10, 25, and 50 kg/ha [4.46, 11.11 and 22.32 ppm, respectively] on plant height, weight, zinc accumulation, zinc use efficiency, health risk index associated with the consumption of treated plants and gene expression analysis of stress-responsive genes. Notably, applying 10 kg/ha [4.5 ppm] of biosynthesized Zn Nps resulted in an increase in the plant height by 34 % and the fresh weight by 53 % compared to the other treatments. However, an increase in the concentration of Zn Nps application led to reduced plant height and fresh weight, both for 25 [11 ppm] and 50 [22 ppm] kg/ha concentration, likely due to excessive zinc toxicity. Zinc accumulation in plant tissues increased significantly for all treatments compared to the control, with dose-dependent increases in leaves, shoots, and roots for Zn Nps. Zinc use efficiency was evaluated, with biosynthesized Zn Nps at 10 kg/ha displaying superior agronomic efficiency, partial productivity factor, and physiological efficiency. While zinc sulfate at 10 kg/ha exhibited lower values than biosynthesized Zn Nps, they still surpassed other concentrations, highlighting the benefits of optimizing zinc levels. Health risk assessment revealed safe consumption across treatments, with hazard risk index (HRI) values below one, particularly for plants treated with 10 kg/ha biosynthesized Zn Nps. Gene expression analysis of stress-responsive genes AhDGR2 and AhGSH1, remained relatively consistent across all treatments.