Phytoremediation Potential of Forage Grasses in Copper-Contaminated Environments

Elevated copper (Cu) concentrations in soils due to anthropogenic activities present a significant environmental challenge, necessitating effective remediation strategies. This study investigated the phytoremediation potential of eight tropical forage grasses, categorized as either resource-exploitative or resource-conservative species, for Cu phytoextraction under controlled greenhouse conditions. Plants were cultivated in nutrient solutions containing 0.3 and 20 µmol L⁻¹ of Cu, and a comprehensive suite of morphophysiological and root architectural traits was evaluated. Variables included plant morphogenesis, leaf area measurements, SPAD index, specific leaf area, specific root area, root density, root length density, specific root length, and the relationships between leaf and stem biomass, as well as root and shoot biomass. Under standard Cu conditions (0.3 µmol L⁻¹), species maintained distinct functional group characteristics, with resource-exploitative species exhibiting 2.0-fold higher leaf expansion rates and 1.6-fold greater specific leaf area compared to resource-conservative species. However, this functional differentiation was not maintained under elevated Cu (20 µmol L⁻¹), where marandu, piatã, and giant missioneira grasses demonstrated a greater adaptability through a better root development (increases of 151%, 292%, and 140% in root length, respectively), higher Cu accumulation in roots (> 1000 mg kg⁻¹), and greater translocation capacity (translocation factors of 0.18, 0.15, and 0.25, respectively). These findings position these species as promising candidates for phytoremediation in Cu-contaminated environments, particularly in tropical regions.