A versatile Lepidium sativum bioassay for use in ecotoxicological studies

This study presents a straightforward and efficient bioassay with garden cress (Lepidium sativum L.) for ecotoxicological analyses. Cress seedlings grow upright in hanging plastic bags on chromatography paper soaked with the test substance. Scans of the bags easily allow digital measurement of the length of the seedlings after the growth period. Suitability of this test system was examined by treating cress with different concentrations of several heavy metal compounds (cadmium nitrate, copper sulphate, iron sulphate, lead nitrate, manganese chloride, zinc chloride) and sodium chloride. Germination rate, length of shoot and root, total length, and root-to-shoot ratio of the seedlings were measured. Calculated values for half maximal effective concentration (EC50) showed that the used heavy metal compounds affected root length, total length, and root-to-shoot ratio of cress in the following order of toxicity: copper > cadmium > iron > lead > zinc > manganese. The results of our experiments indicate that the cress bioassay presented is an efficient and suitable approach for future investigations on water-soluble ecotoxicologically relevant substances.