title: The effect of creosote on the growth of an axenic culture of Myriophyllum spicatum L.
abstract: Due to the importance of submersed, rooted macrophytes to the aquatic ecosystem and the use of creosote impregnated structures adjacent to or within water bodies, a study was conducted using an axenic culture of Myriophyllum spicatum to determine the effect of creosote on this aquatic macrophyte. Four plants were cloned and exposed to nominal creosote concentrations ranging from 0.16 to 200 mg/l for 14 days. A variety of response parameters were assessed, including shoot and root length, number of roots and nodes, and dry weight biomass, as well as visual observations on plant colouring and morphology. Regression and ANOVA analyses were conducted to determine EC50s and significant differences. Biphasic responses were observed for shoot length, node production and biomass, with shoot length showing statistically significant stimulation (hormesis) at creosote concentrations below 13.3 mg/l. EC50 values of 55.1 (CI 40-60) mg/l, 33.4 (CI 26-48) mg/l and 86 (CI 70-120) mg/l were determined for shoot length, dry weight and node production, respectively. Root number was significantly higher at 3.6 mg/l and root length was significantly reduced at 4.5 mg/l creosote, within the concentration range that stimulated shoot growth. Visual changes, including an increase in pink colouration and changes in the location of root initiation, were also observed in the same creosote concentration range that affected root length and numbers. Therefore, it appears that changes in root growth and location of root initiation may be the most sensitive endpoints for creosote effects on Myriophyllum.
authors.affiliation: Department of Environmental Biology, University of Guelph, Ont., N1G 2W1, Guelph, Canada
authors.initials: JH
authors.lastname: McCann
authors.initials: BM
authors.lastname: Greenberg
authors.initials: KR
authors.lastname: Solomon