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This Test Guideline is designed to assess the toxicity of chemicals on the growth of the rooted aquatic plants (Myriophyllum spicatum) growing in water-sediment system. Shoot apices of healthy and non-flowering plant are potted in standardised, artificial sediment supplemented with additional nutrient and exposed to at least five concentrations of the chemical over a period of 14 days. A minimum of 6 replicates for the untreated control and 4 replicates for each test concentration should be used. The measured quantitative variables include growth of shoot length and development of fresh and dry weight, and the measured qualitative variables include presence or not of chlorosis and necrosis or growth deformities. Both average specific growth rate (r) and yield (y) are determined and then used to expressed ErCx and EyCx respectively (x can be e.g. 10, 20, 50.) In addition, the lowest observed effect concentration (LOEC) and the no observed effect concentration (NOEC) may be statistically determined.