OECD 221: Lemna growth inhibition test
The OECD 221: Lemna Growth Inhibition Test measures a chemical's toxicity to plants in the genus lemna (duckweed). Lemna cultures are grown in various concentrations of a test substance. Throughout the study, growth levels and environmental characteristics (pH, light level etc.) are assessed. From this, a ratio of chemical concentration to growth level inhibition is determined, as well as the NOEC and LOEC.