The plant growth inhibition test determines toxic effects of test substances in soil on the germination capacity and early growth stages of various terrestrial plants
Different amounts of the test substance are added to a sieved natural soil (0.5 cm, carbon content < 1.5%, pH 5.0 - pH 7.5, clay and silt fraction 10-20%), and at least 5 plant seeds per concentration in four replicates are used . The number of germinable seeds in the test lines and controls is recorded. Fourteen days after 50% of the seeds in the control lines have germinated; the mean weight (wet weight taken directly after harvesting or dry weight after drying at 70 °C) is determined and compared with the values in the controls. The concentration at which the plant growth is inhibited to 50% (EC50) or at which 50% of the seeds did not germinate (LC50), in comparison to the control, is given as result.
The selection and number of plant species to be tested depends on the particular requirements of the regulatory rules and is not defined in the OECD method.
In the Hydrotox laboratory currently no terrestrial ecotoxicity tests are conducted under GLP, but co-operation laboratories are commissioned with these tasks.