Copper phytotoxicity in native and agronomical plant species

Copper (Cu) is a widespread soil contaminant that is known to be highly toxic to soil biota. Limited information is available on the response of wild endemic species to Cu in the literature, which hinders ecological risk assessments and revegetation. In the present study, the phytotoxicity of Cu in nutrient solution was studied in five Australian endemic plant species (Acacia decurrens, Austrodanthonia richardsonii (Wallaby Grass), Bothriochloa macra (Redgrass), Eucalyptus camaldulensis var. camaldulensis (River Red-Gum) and Dichanthium sericeum (Bluegrass) and two vegetable plants species (Lactuca sativa L. ‘Great lakes’ and Raphanus sativa L.). Vegetable species were grown in a more concentrated nutrient solution. The response of B. macra was also compared between the two nutrient solutions (dilute and concentrated nutrient solution). In the first experiment, D. sericeum and E. camaldulensis were found to be highly sensitive to Cu exposure in nutrient culture. Critical exogenous Cu concentrations (50 percent reduction in roots) for E. camaldulensis, D. sericeum, A. richardsonii, B. macra (dilute), L. sativa, B. macra (concentrated), R. sativa and A. decurrens were, respectively, (μg/L) 16, 35, 83, 88, 97, 105, 128 and 186. Copper tolerance in B. macra was observed to be higher in the more concentrated nutrient solution despite the estimated Cu2+ concentration being very similar in treatment solutions. Additional short-term rhizo-accumulation studies showed that neither Ca2+ not K+ was responsible for reduced uptake at the roots. However, the estimated maximum shoot Cu was reduced from 41 to 24 mg/kg in the more concentrated solution.

► Eucalyptus camaldulensis was highly sensitive to Cu exposure. ► Bothriochloa macra tolerance was enhanced by greater nutrient content in solution. ► Calcium and potassium did not influence the rate of Cu uptake in Bothriochloa macra.