Zohra Omouri*, Jalal Hawari, Michel Fournier and Pierre Yves Robidoux
Phytotoxicity of Bi citrate and Bi nitrate on perennial ryegrass were evaluated using standardized filter paper and soil tests. Endpoints included seeds germination, and root and shoot growth. The results showed that Bi nitrate seemed to be more toxic than Bi citrate, and root growth more sensitive than seeds germination and shoot growth. Filter paper test indicated that Bi nitrate significantly decreased root elongation (IC50=60.34 mg/L) at tested concentrations ≥ 30.35 mg/L
and seedling germination at 485 mg/L. Bi citrate decreased significantly root elongation (IC50=139.5 mg/L) and seedling germination at concentration ≥ 99.52 mg/L and at 398.08 mg/L, respectively. Data from OECD artificial soil spiked with Bi nitrate indicated a significant reduction on root mass at 485 mg/kg soil but no significant effect was observed on shoot mass and germination at concentration ≤ 485 mg/kg soil. In natural soil, Bi nitrate reduced significantly root mass and root
elongation at concentration ≥ 4.8 and 48.5 mg/kg soil, respectively. No effect was however observed on seeds germination and shoots mass. Natural soil spiked with Bi citrate showed no significant decrease in seed germination and root growth at concentrations ≤ 398 mg/kg. The toxicity of Bi salts on perennial ryegrass varied with the matrix in the following order: filter paper>natural soil>OECD artificial soil. We assume that Bi phytotoxicity is related to Bi bioavailability which in turn is controlled by solubility of the Bi salt in addition to the physicochemical properties of the tested matrix.
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