Abiotic factors modulate lead depletion and the phytoremediation potential of three herbaceous plant species under hydroponic conditions

The present study investigated the role of abiotic factors in lead (Pb) depletion via mass balance analysis and the accumulation potential and physiological responses of herbaceous plants, Cynodon dactylon, Centella asiatica, and Eragrostis pilosa, under hydroponic conditions. Aqueous Pb concentrations declined by more than 99% within the first 96 h, which was predominantly contributed by abiotic factors. Plant biomass accounted for 1.79–38.48% Pb recovery, while the remaining 61.52–98.21% Pb was not recovered in biomass, highlighting the contribution of non-plant-associated processes in Pb depletion. C. dactylon and E. pilosa accumulated 3.3-fold more Pb than C. asiatica. A translocation factor below 1 (E. pilosa < C. dactylon < C. asiatica) and a bioconcentration factor above 1 (E. pilosa < C. asiatica < C. dactylon) indicated Pb accumulation in roots. Plants showed lead-associated toxic stress via alterations in phyto-pigments, carotenoids, free amino acids contents, and antioxidant enzymes. Scanning electron microscopy of the root tissues supported anatomical alterations. Energy-dispersive X-ray analyses suggested nutrient imbalances (Ca, Mg, N, Fe, and Mn). These findings indicate species-specific Pb accumulation and stress-response patterns, while highlighting the need to distinguish aqueous Pb depletion from plant-mediated uptake when evaluating phytoremediation performance. Pb depletion was observed in hydroponics with three herbaceous plant species.Pb depletion followed a distinct dual-phase pattern.Non-plant-associated processes were a major contributor in aqueous phase Pb depletion.Root Pb accumulation exceeded shoot accumulation across treatments.SEM-EDX indicated Pb localization within root tissues.Species-specific differences were observed in Pb depletion and accumulation. Pb depletion was observed in hydroponics with three herbaceous plant species. Pb depletion followed a distinct dual-phase pattern. Non-plant-associated processes were a major contributor in aqueous phase Pb depletion. Root Pb accumulation exceeded shoot accumulation across treatments. SEM-EDX indicated Pb localization within root tissues. Species-specific differences were observed in Pb depletion and accumulation. This research provides a comprehensive analysis of three herbaceous plants in terms of lead phytoremediation capabilities. We have used metal uptake indicators as well as used a battery of biochemical parameters to test the metal-response mechanisms of these plants. We have also studied the nutrient imbalance in plant roots due to the presence of Pb using SEM-EDX analysis. Mass-balance analysis was also made in order to achieve valuable insights into aqueous Pb depletion. The outcome of this study highlights the mechanism of Pb depletion from aqueous phase and plant uptake/response vis a vis its phytoremediation capabilities.