White mustard (Sinapis alba) is a sensitive test plant. Its growth is inhibited in contact with toxic substances. The toxic effect can be estimated by measuring its root and shoot length. The test procedure applied to chemical substances is identical with the one detailed in the surface water and sediment photo gallery. https://www.enfo.hu/en/node/13295
The difference compared to the environmental samples is that for toxicity assessment of chemical substances the substance is dissolved in distilled water then the dilution series is prepared. The inhibition of the members of the dilution series is measured.
The concentration-effect curve based on the concentration series data is used for the evaluation. EC50 (concentration causing 50% inhibition), NOEC (the highest no effect concentration) and LOEC (the lowest no effect concentration) are read by statistical methods from the curve fitted to the measurement points.
Feigl, V. White mustard (Sinapis alba) root and shoot growth inhibition test for ecotoxicity assessment of chemical substances (in Hungarian) https://www.enfo.hu/node/7530