Recommendations and Standard Procedures for Biotests

In most cases a test for direct material toxicity to animals (birds, rats, rabbits and so on), may not be of primary interest. Such interactions should only be considered if a product is applied in a shape and colour that may be confused with feed by such animals and may be consumed by them in relevant amounts. The encapsulation of fertilisers or pesticides with biodegradable polymers in granular shape may be such a case. On the other hand, the encapsulated substances are most probably more harmful to animals than the biodegradable polymer coating. 

In the following paragraphs the most suitable test methods are described in more detail and applied research results are added as far as possible. The list of methods may change frequently because method development is performed by many scientists in order to adapt and evaluate established methods for their use in complex matrices 

Test organism Sample types Standard/literature Comments 

Higher plant species, terrestrial (cress, millet, oilseed rape and so on) Compost and soil OECD 208 ISO 11269-1 and ISO 11269-2 Many species available 

Higher plant species, aquatic (Lemna sp.) Freshwater and sediments OECD 221 Simple, rapid, sensitive 

Since plants are in most cases the primary target organisms for agricultural applications the methods and influencing parameters of plant biotests will be described in more detail than for all the other test organisms. 

The OECD method 208 [32] requires the application of at least three tests in parallel using three different plant species. That seems to be justified, since the grouped species are sensitive to different inhibition mechanisms. Such tests could be varied for the determination of the germination rate or of the plant growth (biomass production) or for both effects at the same time. 

For the determination of the germination rate, a known number of seeds is put on top of the sample and watered properly. After the species specific germination time the number of young plants is counted and compared with the germination rate in the reference 

---