Physiological and uptake responses of Tagetes erecta to lead and cadmium stress mediated by arbuscular mycorrhizal fungi

Soil contamination with potentially toxic elements (PTEs) such as lead (Pb) and cadmium (Cd) poses a significant threat to food security, ecosystem stability, and public health, particularly in urban and peri-urban environments. Despite increasing interest in phytoremediation, limited attention has been given to ornamental species with dual ecological and esthetic value. This study aimed to evaluate the capacity of Tagetes erecta (marigold), inoculated with arbuscular mycorrhizal fungi (AMF), to tolerate and accumulate Pb and Cd under controlled conditions. A greenhouse factorial experiment was conducted using five concentrations of Pb (0–200 mg/kg) and Cd (0–52.2 mg/kg) with and without Rhizophagus irregularis inoculation. AMF inoculation significantly improved biomass production and altered metal uptake patterns under PTE stress, suggesting modulation of physiological tolerance mechanisms. Key variables measured included shoot and root biomass, chlorophyll content, metal accumulation, and translocation/bioaccumulation factors. AMF inoculation significantly increased shoot dry weight by up to 43% under Pb200 and Cd52.2 treatments (p < 0.05), while reducing shoot Cd concentration by 41% at moderate contamination levels. Root colonization ranged from 80% to 94% in inoculated plants. Translocation factor for Pb reached 2.11 in AMF-treated plants, indicating enhanced mobility. These findings demonstrate that T. erecta–AMF symbiosis promotes biomass retention and selective metal uptake under PTE stress, suggesting a role in phytostabilization rather than active phytoextraction in ornamental settings for moderately contaminated soils.