Plant growth-defense trade-offs regulate phytoremediation efficiency and ecosystem resilience in the contaminated...

Understanding how plants balance growth and defense under contamination is indispensable for designing sustainable remediation strategies. However, its role in regulating remediation under multi-metal stress remains poorly understood in realistic field conditions. We examined 21 indicator plants from the lead, zinc and manganese contaminated environments to test how plant growth-defense allocation regulates remediation efficiency. Field-based analyses integrated toxic elements bioaccumulation, bioconcentration and translocation factors with physiological traits viz., proline osmolyte, antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), lipid peroxidation (MDA) and chlorophyll pigments. Results showed that phytoremediation capacity varied among species and was associated with growth defense allocation patterns. Chlorophyll pigments significantly declined with increased accumulation of proline, antioxidant enzyme activities and lipid peroxidation increased, indicating a growth-defense trade-off under metal stress. Ordinary least squares and mixed-effects models determined that proline osmolyte significantly relates to Zn, Pb, Mn, Ni, Cd, Co, Cr and Cu remediation. Antioxidant enzymes showed element-specific responses. SOD and CAT were associated with Cd, Pb, Ni, Zn and POD with Mn, Pb, Ni, Co, Cr and Cu detoxification. Structural equation modeling further confirmed plant growth-defense trade-offs and revealed that the polluted environment induced phytoremediation and antioxidant enzymatic activities, lipid peroxidation, proline osmolyte and reduced chlorophyll pigments. It is concluded that the studied indicator plants exhibited higher defensive investment accompanied by lower growth-related traits during remediation of the contaminated world, although the magnitude and direction of these trade-offs different among species and PTEs. These findings provide a mechanistic understanding of how natural vegetation regulates remediation through growth-defense trade-offs and offer new insights for ecological resilience and sustainable environmental management.