OCSPP 850.4100: Seedling Emergence and Seedling Growth

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. Ten plant species are chosen according to the specific properties of the test item and the intended use. There should be six dicot species of at least four families, one species of which is Glycine max (soybean) and four monocot species of at least two families among them Zea mays (corn). One of the 10 chosen species has to be a root crop such as Allium cepa (onion), Daucus carota (carrot) or Beta vulgaris (sugar beet).

Test 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 other 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 test item/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 onto the soil surface after sowing (plant protection products) or the test item is incorporated into the soil (chemicals) and seeds are planted in this treated soil. The test item concentration of each spraying solution has to be confirmed analytically before and after application. After the application the plants are evaluated weekly for effects (emergence and phytotoxticity) in comparison to the control plants for 14 to 21 days after 50 % emergence of the seedlings in the control group. At the test end the endpoints (e.g. shoot dry weight, shoot height, emergence, mortality) are measured and recorded.

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

Endpoints are emergence, mortality, shoot height and shoot dry weight. If the test is conducted as multiple rate test effects on shoot height and shoot dry weight are reported as ERX (Effective Rate) for each species individually as NOER (No Observed Effect Rate) in case of a limit study.
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

• OCSPP 850.4100 “Seedling Emergence and Seedling Growth”