Estudos de fitorremediação de solo contaminado com chumbo por Helianthus annuus L. (Girassol): análise fisiológica, bioquímica e proteômica

Abstract

Environmental contamination by heavy metals represents one of the greatest ecological challenges of the present time due to the persistence of these elements and their toxicity to living organisms. Phytoremediation emerges as a sustainable alternative for soil decontamination, exploiting the potential of plant species capable of absorbing, stabilizing, or degrading pollutants. The present study aimed to evaluate the remediation potential of soils contaminated with lead [Pb(NO₃)₂] using two Brazilian sunflower cultivars, BRS 323 and BRS 415. Plants were cultivated for 30 days in soils containing different Pb(NO₃)₂ concentrations: 0, 150, and 900 mg kg⁻¹, corresponding to the alert and intervention levels established by CETESB and CONAMA. Samples of roots, stems, and leaves were collected and subjected to physicochemical, morphological, enzymatic, and proteomic analyses. Physiological results demonstrated that both cultivars exhibited high germination viability; however, BRS 323 showed greater tolerance to lead, maintaining higher germination and growth rates. Lead accumulation was predominantly concentrated in the roots, indicating a phytostabilization mechanism. Morphological development showed alterations in leaf and root structures and a reduction in overall growth, although the 900 mg kg⁻¹ treatment (PB900) displayed superior performance compared to 150 mg kg⁻¹ (PB150), suggesting a non-linear adaptive response. Regarding photosynthetic pigments, a slight reduction in chlorophyll content was observed under contamination, while carotenoid levels remained stable, indicating possible resilience of the photosynthetic apparatus. Biochemical analyses revealed elevated ATP content, reflecting increased energy demand to sustain defense processes. Although hydrogen peroxide (H₂O₂) levels increased, this effect was counterbalanced by the activation of antioxidant enzymes, particularly catalase and ascorbate oxidase. Proteomic analysis identified 1,691 proteins associated with detoxification pathways, ion homeostasis, energy metabolism, and protein repair. The study demonstrated that sunflower possesses a complex molecular machinery capable of reorganizing its metabolism under lead-induced stress, involving ion sequestration responses, redox adjustments, and proteomic reprogramming. The superior performance of the BRS 323 cultivar under high contamination conditions suggests the presence of efficient resistance mechanisms and potential use in sustainable remediation strategies. Based on these findings, we conclude that cultivar BRS 323 exhibits a high phytoremediation potential for lead-contaminated soils, combining physiological tolerance, root sequestration capacity, and adaptive proteomic reprogramming.