Mitigation of Cr (VI) phytotoxicity in mung bean seedlings through the supplementation of phyto-fabricated zinc oxide nanoparticles using Paederia foetida

The administration of biogenic zinc oxide nanoparticles (ZnO NPs) on Cr (VI)-stressed mung bean plants (Vigna radiata) promoted plant growth by reducing the phytotoxicity of hexavalent chromium. The biogenesis of ZnO NPs involved the use of the indigenous plant Paederia foetida Linn. The obtained ZnO NPs were characterized by TEM, FE-SEM, FTIR, Raman, AFM, and GCMS techniques that confirmed the formation of ZnO NPs. The antioxidant enzyme level, ultrastructural alterations, and plant growth were investigated in the presence of Cr (VI) and ZnO NPs on mung bean plants. Cr (VI) treatment of mung bean seedlings adversely affects whole plant growth in terms of length of roots, shoots, lateral root numbers, and weight of dry plant. Remarkably, ZnO NPs mitigated the adverse effects of Cr (VI)-stressed mung bean plants by restoring the enzymes and ultra-structural alterations. Mung bean roots exposed to Cr (VI) stress exhibited higher concentrations of antioxidant enzymes, while the ZnO NPs suppressed the elevated expression of the enzymes caused by Cr (VI). When treated with 10 ppm of Cr (VI) + 5 ppm of ZnO NPs, the plants had significantly longer roots and shoots (50-60%) than those treated with 10 ppm of Cr (VI). Further, the antimicrobial efficiencies of ZnO NPs against pathogenic organisms such as shiga toxin-producing Escherichia coli were investigated and proved to exhibit excellent antimicrobial activity. The MIC of ZnO NPs against Escherichia coli was found to be 15 mu g mL-1. The ZnO NPs revealed excellent DPPH radical and superoxide scavenging activities with an IC50 value was 400 and 200 mu g mL-1, respectively. The ZnO NPs (1000 mu g mL-1) exhibited effective inhibition of free radicals with a highest percentage inhibition of similar to 96 +/- 0.5%. Therefore, the findings