Duckweed cultures
Axenic cultures of the three duckweed species were maintained at the Department of Evolutionary Biology and Environmental Studies, University of Zürich. Three strains were delivered in July from the Landolt Duckweed Collection (www.duckweed.ch). Lemna turionifera , strain 9478, sourced from Racibórz, Silesian, Poland, Lemna minor , strain 9978, sourced from Oberegg, Appenzell Innerrhoden, Switzerland, and Lemna gibba , strain 9965, sourced from Schloss Wartensee, Rorschacherberg, St. Gallen, Switzerland. The axenic cultures were held on Hoagland’s E Medium (see Appendix for recipe used) in incubators at 18 °C with a light regime of 14/10h light/dark.