Heavy Metal-Induced Phytotoxicity, Accumulation, and Phytoremediation Potential of Euryale ferox Salisb. in the Wetlands of North Bihar, India

Abstract

Euryale ferox Salisb. is an ecologically and economically important aquatic macrophyte widely cultivated in the wetlands of North Bihar, India, where increasing metal contamination may pose risks to plant growth and wetland sustainability. The present study evaluated the comparative phytotoxicity, growth responses, tissue-specific metal accumulation, and phytoremediation potential of E. ferox exposed to chromium (Cr), lead (Pb), and cadmium (Cd). Plants were subjected to 0, 50, 100, 150, 200 and 250 μM concentrations of the respective metals under controlled conditions. Morphological and growth responses were assessed together with visual toxicity symptoms, biomass production, metal accumulation in roots and shoots, bioaccumulation factor (BAF), and translocation factor (TF). All three metals produced concentration-dependent reductions in plant height, leaf number, leaf area, root length, fresh biomass and dry biomass. The inhibitory effects were most pronounced under Cd exposure, followed by Cr and Pb. At 250 μM, Cd reduced plant height, leaf area, root length, fresh biomass and dry biomass by approximately 31.3%, 42.2%, 40.2%, 34.2% and 38.7%, respectively, relative to the control. Visual toxicity also increased progressively with metal concentration, with overall stress indices reaching 19, 18 and 15 under Cd, Cr and Pb, respectively. Metal accumulation was predominantly localised in roots, with Pb showing the highest accumulation, reaching 1495 ± 38 mg kg⁻¹ dry weight at 250 μM. BAF values were highest for Pb (12.3–14.8), while TF remained below 1 for all metals, indicating restricted translocation to shoots. In addition, E. ferox substantially reduced dissolved metal concentrations in the growth medium, with reported removal of 41–73% Cr, 46–78% Pb and 38–70% Cd after seven days. These findings demonstrate that E. ferox exhibits considerable metal tolerance together with strong root-based metal sequestration. Although its low TF excludes it as an efficient phytoextractor, its pronounced root accumulation and metal-removal capacity indicate promising applications in rhizofiltration and phytostabilisation of multi-metal-contaminated aquatic habitats.