Investigating plant response to chromium stress in a greenhouse setup: phytoremediation vs ZnO-assisted nanophytoremediation using Marigold

Chromium exposure has emerged as a critical concern due to its bioaccumulation in living tissues and associated adverse health effects. To address this challenge, the present study systematically compares conventional phytoremediation and nanophytoremediation approaches employing Tagetes erecta for enhanced chromium removal. In the nanophytoremediation approach, zinc oxide nanoparticles were synthesised from the same plant through a green synthesis method. Various biochemical parameters were analysed to assess dose and time-dependent variations under exposure to chromium and nanoparticles. The statistical significance of the observed changes was evaluated using two-way ANOVA, and all the values are statistically significant among all treatments with p < 0.05. Additionally, this pioneering work offers theoretical insights into the interactions between nanoparticles and key enzymes involved in the synthesis and degradation of biochemical compounds, as explored through molecular docking studies using AutoDock software. The docking studies highlight the strong interaction of ZnO nanoparticles with the enzyme involved in the synthesis and degradation of biochemicals, which helps to strengthen the phytoremediation efficiency of the plant. The average chromium removal efficiency was 69% under phytoremediation conditions. In nanophytoremediation, a maximum efficiency of 76.6% was achieved at 10 µg/mL ZnO, while increasing nanoparticle concentrations to 50 and 100 µg/mL decreased chromium removal to approximately 50% and 41.8%, respectively. This work can serve as a reference for genetically modified and advanced remediation measures to effectively and sustainably remove toxic chromium from water.