Zinc promotes cadmium leaf excretion and translocation in tall fescue (Festuca arundinacea).

Phytoexcretion is a novel strategy to remediate cadmium (Cd) pollution by leaf excretion in tall fescue (Festuca arundinacea), which involves the processes of Cd leaf excretion, root-to-leaf translocation, and root uptake. A hydroponic experiment was designed to investigate a series of 11 zinc (Zn) concentrations on Cd leaf excretion in tall fescue under 75 μM Cd stress. The results showed that the promotions of Zn on Cd leaf excretion, root-to-leaf translocation, and leaf accumulation were concentration-dependent in tall fescue. Zn treatments at 90 and 135 μM resulted in the highest Cd leaf excretion with 118.1 and 123.6 mg/kg of Cd excretion amount and 27.0 and 26.6% of excretion ratio, which were 2.6 and 2.7 fold of the control (15 μM of Zn), respectively. Cd leaf excretion was decreased when Zn treatments reached 180 μM, which could be toxic to plants as indicated by the decline of plant biomass. Zn also promoted leaf Cd accumulation and Cd translocation from roots to leaves and reached the highest at 90 and 180 μM respectively. Root Cd accumulation decreased with the increase of Zn concentrations, but the total plant Cd uptake did not decrease significantly until Zn concentration reached 90 μM. Our results indicate that 90 μM of Zn treatment can be served as the threshold to promote Cd leaf excretion and improve the efficiency of Cd phytoexcretion in tall fescue.