OECD 208: Terrestrial Plant Test - Seedling Emergence and Seedling Growth Test


Non-target plants, i.e. plants in natural and semi-natural habitats within the agricultural land such as hedgerows, field borders, meadows and other small biotopes may unintentionally be exposed to Plant Protection Products, veterinary medicinal products, biozides or chemicals.
The OECD guideline 208 assesses the potential effects of a test item on seedling emergence and early growth of seedlings following exposure to the test item in or on the soil.

Study Design

Plant species

The plant species selected for the test should derive from different plant families to consider the taxonomic diversity and should give reliable and reproducible results. Usually 6 to 10 plant species are chosen according to the specific properties of the test item and the intended use. Among them could be for example Allium cepa (onion), Zea mays (corn), Brassica napus (oilseed rape), Cucumis sativus (cucumber), Glycine max (soybean), Helianthus annuus (sunflower), Solanum lycopersicon (tomato) or Stellaria media (common chickweed).



Test concentrations / rates

Test concentrations / rates are usually determined in a range-finding pre-test. For plant protection products the rates for the pre-test are calculated based on the maximum application rate. For veterinary medicinal products concentrations for the pre-test can be calculated based on the expected PEC (Predicted Environmental Concentration) soil. Alternatively, it is possible to use 1000 mg/kg dry soil as maximum concentration in the pre-test.

Course of the test

Depending on the expected route of exposure, the test item is either sprayed on to the soil surface after sowing (plant ptrotection products) or the test item is incorporated into the soil (veterinary medicinal products, chemicals) and seeds are planted in this treated soil. The test item concentration has to be confirmed analytically. After the application the plants are evaluated weekly for effects (emergence and phytotoxticity) in comparison to the water treated control plants for 14 to 21 days after 50 % emergence of the seedlings in the control group. At the test end the endpoints are measured and recorded.


Seedling emergence and seedling growth test with test item treated manure for veterinary medicinal products

In the case of strong effects for a veterinary medicinal products in a OECD 208 test this test item can be applied to manure to have a more realistic approach (Concept development for an extended plant test in the environmental risk assessment of veterinary medicinal products). This manure is then incubated under anaerobic conditions. The incubation time depends on the type of manure (cattle, pig) and its normal storage time. The spiked manure is then incorporated into the soil. The further study design has to fullfill the requirements of OECD 208. The effects are evaluated in comparison to a non-spiked manure treated control.

Growth Conditions

The studies are performed in a growth chamber with controlled, optimized test conditions for standardised studies. The temperature is 22 °C during the light period and 18 °C during the dark period (mean 22 °C ± 10 °C) and humidity is 70% ± 25%. During the photoperiod of 16 hours light the intensity is 350 ± 50 µE/m2/s.
For special needs, more differentiated studies and research these conditions can be adapted within a wide range.


Endpoints are emergence, mortality and shoot fresh weight. If the test is conducted as multiple rate test, effects on fresh weight are reported as ERX (Effective Rate) for each species individually as NOER (No Observed Effect Rate) in case of a limit test.
Additional parameters are shoot height and shoot dry weight, reported as ERX for each species individually.
Phytotoxicity (e.g. chlorosis, necrosis, deforamtion) and growth stages (BBCH code) are recorded. If the test is conducted as multiple rate test an ERX (effective rate) caluation on phytotoxicity is possible.


Guidelines and literature

  • OECD Guidelines for Testing of Chemicals No. 208 “Terrestrial Plant Test: Seedling Emergence and Seedling Growth Test”.

  • Concept development for an extended plant test in the environmental risk assessment of veterinary medicinal products, Federal Enviroment Agency.