Division 1.7.4 Test medium

Different media are recommended for Lemna minor and Lemna gibba, as described below. Careful consideration should be given to the inclusion of a pH buffer in the test medium (MOPS (4-morpholinepropane sulphonic acid, CAS No: 1132-61-2; EINECS No: 214-478-5) in L. minor medium and NaHCO₃ in L. gibba medium) when it is suspected that it might react with the test substance and influence the expression of its toxicity. Steinberg Medium (12) is also acceptable as long as the validity criteria are met.

A modification of the Swedish standard (SIS) Lemna growth medium is recommended for culturing and testing with L. minor. The composition of this medium is given in Appendix 3.

The growth medium, 20X — AAP, as described in Appendix 3, is recommended for culturing and testing with L. gibba.

Steinberg medium, as described in Appendix 3, is also suitable for L. minor, but may also be used for L. gibba as long as the validity criteria are met.