Accumulation capacity of cadmium and copper and their effects on photosynthetic performance in Azolla filiculoides Lam. under induced rhizofiltration

Abstract

This study evaluated the capacity of Azolla filiculoides to enhance heavy metal accumulation through the addition of different concentrations of cadmium (Cd) and copper (Cu), as ethylenediaminetetraacetic acid (EDTA) complexes, under hydroponic conditions. The physiological effect was determined by Photosynthetic efficiency (Fv/Fm) as an indicator of plant stress, and heavy metal content was measured with flame atomic absorption spectroscopy in the whole plants. The results obtained in rhizofiltration systems did not show an increase in accumulation when Cd-EDTA was added, but the Cu-EDTA increased the accumulation of Cu by plants. Although the Fv/Fm was decreased in all treatments, only the Cd-EDTA complex caused damage to photosystem II (PSII) activity, and that damage was critical. These results coincide with the higher toxicity of cadmium to plants; the quantity of cadmium in the plants, although small, was indeed harmful to them. The correlation analysis for both heavy metals coincides with the assumption that the heavy metals on leaf tissue affected the photosynthetic metabolism. This research makes a new contribution to the field by evaluating EDTA-induced Azolla rhizofiltration in aquatic systems, a departure from the majority of the literature on the topic, which examines EDTA in soil remediation. In future, further study is needed on the interactions of EDTA with other ions and the physiological consequences for different plant species.