Development of a growth inhibition test using Veronica undulata, a dicot aquatic plant

Abstract

We aimed to develop a growth inhibition test using Veronica undulata, a dicot aquatic plant. The examination was carried out using simetryn, 2,4–D, and 3,5–DCP as the test substances, to confirm the precision of the examination and sensitivity of Veronica undulata to herbicides. Directly post-germination, Veronica undulata was exposed to each test substance for seven days, and ErC₅₀ was calculated based on the growth speed of the leaf area or the dry weight. The coefficient of variation of ErC₅₀ for each test was less than 20%, and stable test results were obtained. In the growth inhibition test, the ErC₅₀ (μg/L) values of 2,4–D and 3,5–DCP were 585 and 3,394, and the sensitivity was at the same level as that by using Myriophyllum spicatum. These results suggest the possibility of using this test as a screening method for assessing the toxicity of chemical substances to dicot aquatic plants.