Abstract:
Phytoextraction of metals is frequently limited by contaminant bioavailability and plant uptake rates. Chemical amendments can be added to increase the uptake and translocation of metals to aerial biomass. A range of amendments of various types was tested for increasing the copper uptake with the test species Indian mustard and ryegrass. These included citric acid (an organic acid); histidine (an amino acid); ethylenediaminetriacetic acid (EDTA), nitrilotriacetic acid (NTA), and ethelynediaminedisuccinic acid (EDDS) (aminopolycarboxylic acids); rhamnolipid (a biosurfactant); and Triton X-100 (a synthetic surfactant). EDTA was the most effective amendment for enhancing copper uptake and translocation into the shoots of Indian mustard and ryegrass, with respective shoot tissue copper levels of 1230 and 1360 ¼g-Cu/g-dry weight after 10 d compared to 90 and 220 ¼g-Cu/g-dry weight, respectively, in the unamended treatments. However, the EDTA application resulted in symptoms of toxicity in both Indian mustard and ryegrass, leading to drastic decreases in biomass yield. The application of high levels (300 mg/L) of the biodegradable chelator EDDS was found to be effective for improving translocation of copper in both species. The NTA addition provided benefits to root and shoot growth, with increased copper translocation to shoot tissue. Tests with biosurfactants and synthetic surfactants indicated detrimental effects on copper uptake, biomass yield, and the translocation of copper from roots to shoots in both plant species.
