Tagetes erecta as a Nickel Phytoremediator: Insights into Accumulation and Growth Response

Abstract This study investigates the nickel (Ni) accumulation capacity of Tagetes erecta L. in soils with varying Ni concentrations, focusing on its potential for phytoremediation. Preliminary analyses confirmed that approximately 60% of Ni remained bioavailable, facilitating efficient plant uptake. Adsorption-desorption experiments demonstrated that Ni binding to soil was reversible, predominantly driven by weak physical interactions, ensuring the sustained availability of mobile Ni fractions. Morphological assessments indicated that T. erecta exhibited optimal growth and increased biomass production at Ni concentrations up to 2000 mg/kg dry matter, with enhanced stem diameter, leaf mass, and flower production. In contrast, plants grown in soils with 6000 mg/kg d.m. Ni showed severe damage and did not survive. Twelve weeks after sowing, flame atomic absorption spectroscopy revealed that flowers were the primary Ni storage sites, followed by stems and leaves. At 2000 mg/kg d.m. Ni, T. erecta accumulated over 50 mg/kg d.m. Ni. These findings highlight the phytoremediation potential of T. erecta , particularly in moderately Ni-contaminated soils. From the circular economy perspective, phytoremediation offers dual benefits, firstly enabling the recovery of nickel from harvested biomass, which can be reintroduced into supply chains, hence reducing reliance on primary nickel mining and lowering the ecological footprint of metal production, while also contributing to environmental restoration through soil cleaning. Ability of T. erecta to accumulate significant Ni levels while maintaining viable biomass production offers a sustainable and promising approach that aligns with circular economy principles.