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Toxicity to aquatic plants other than algae

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Description of key information

In duckweed (L. gibba), the 7-d EC50-values for inhibition of the specific growth rate of fronds (ErC50) and dry weight (ErdwC50) are 30.4 mg/L and 12.3 mg/L, respectively. No toxicity were observed within the water solubility (WS ≤0.01 mg/L).

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Additional information

The toxicity to aquatic plants other than algae was determined in a study according to OECD guideline No 221 and in compliance with GLP criteria (BASF, 2015).

In this study 3 replicates of 3 uniform, healthy-looking duckweed (L. gibba), with 4 fronds each, were introduced in test vessels containing test substance at 0 (control), 1.20, 3.79, 12.0, 37.9 and 120 mg/L. Plants were exposed for 7 days under semi-static conditions. Test concentrations were not analytically verified because the water solubility limit was below the analytical limit of quantification. Observations of frond size, appearance, indication of necrosis, chlorosis or gibbosity, colony break-up or loss of buoyancy, of root length and appearance, as well as of change in colour and destruction of roots, were made on every determination day and at the end of the exposure. At the end of the test period, dry weight was determined. Throughout the test a decrease in frond numbers was visible with increasing test item concentrations. These effects were statistically significant from a test item concentration of 3.79 mg/L. The EC50-values for inhibition of the specific growth rate of fronds (ErC50) and dry weight (ErdwC50) were 30.4 mg/L and 12.3 mg/L, respectively. The EC50-values for inhibition of yield (EyC50) and dry weight inhibition of yield (EydwC50) were 11.4 mg/L and 5.27 mg/L, respectively. All effects are higher than the solubility limit of the substance in water.

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