Can phosphate compounds be used to reduce the plant uptake of Pb and resist the Pb stress in Pb-contaminated soils?
Can phosphate compounds be used to reduce the plant uptake of Pb and resist the Pb stress in Pb-contaminated soils

The effects of different phosphate-amendments on lead (Pb) uptake, the activities of superoxide dismutase (SOD) and the level of malondialdehyde (MDA) in cauliflower (Brassica oleracea L.) in contaminated soils with 2 500, 5 000 mg P2O5/kg soil of hydroxyapatite (HA), phosphate rock (PR), single-superphosphate (SSP) and the mix of HA/SSP (HASSP) were applied in pot experiments. Results showed that the Pb concentration in the shoots and roots was decreased in 18.3%-51.6% and 16.8%-57.3% among the treatments respectively compared to the control sample. The efficiency order of these phosphate amendments in reducing Pb uptake was followed as: HASSP≈ HA > SSP ≈ PR. With the addition of SSP, HA and the mix of HA/SSP, the SOD activity in the shoots was markedly reduced (P < 0.05) compared with that in control group, for example, the SOD activities in the shoots by the treatments of HASSP, SSP, and HA in 5 000 mg P2O5/kg were found to be only 51.3%, 56.2%, and 56.7%, respectively. The similar effects were also observed on the level of MDA in the shoots with the decrease in 24.5%-56.3%. The results verified the inference that phosphate compounds could be used to reduce the plant uptake of Pb and resist the Pb stress in the plant vegetated in Pb-contaminated soils.