Lead phytotoxicity in soils and nutrient solutions is related to lead induced phosphorus deficiency

Cheyns, Karlien; Peeters, Sofie; Delcourt, Dorien; Smolders, Erik

Lead phytotoxicity in soils and nutrient solutions is related to lead induced phosphorus deficiency

2012

Cheyns, Karlien | Peeters, Sofie | Delcourt, Dorien | Smolders, Erik

This study was set up to relate lead (Pb) bioavailability with its toxicity to plants in soils. Tomato and barley seedlings were grown in six different PbCl₂ spiked soils (pH: 4.7–7.4; eCEC: 4.2–41.7 cmolc/kg). Soils were leached and pH corrected after spiking to exclude confounding factors. Plant growth was halved at 1600–6500 mg Pb/kg soil for tomato and at 1900–8300 mg Pb/kg soil for barley. These soil Pb threshold were unrelated to soil pH, organic carbon, texture or eCEC and neither soil solution Pb nor Pb²⁺ ion activity adequately explained Pb toxicity among soils. Shoot phosphorus (P) concentrations significantly decreased with increasing soil Pb concentrations. Tomato grown in hydroponics at either varying P supply or at increasing Pb (equal initial P) illustrated that shoot P explained growth response in both scenarios. The results suggest that Pb toxicity is partially related to Pb induced P deficiency, likely due to lead phosphate precipitation.

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