Use ofLemna minor L. as a bioassay in allelopathy

Investigations in allelopathy often require the use of a bioassay for evaluating limited quantities of potentially active growth regulators. A bioassay procedure was developed usingL. minor grown in 1.5-ml aliquots of nutrient medium with and without allelochemicals in wells of 24-well tissue culture cluster dishes with loose-fitting lids. Tests using six replications per treatment with several flavonoid compounds and derivatives of coumarin, benzoic acid, and cinnamic acid demonstrated that the bioassay was capable of measuring inhibition at levels of compound ranging from 50 to 1000 μmol. Strongly inhibitory treatments were visible after 1 or 2 days. After 7 days of growth, frond number, growth rate, and dry weight were used to evaluate effects. The bioassay system is relatively simple, very sensitive, reproducible, and can be used for testing small amounts and dilute concentrations of unknowns which have been separated by chromatography.