Environmental factors affecting seed germination in Myriophyllum spicatum L

Myriophyllum spicatum L. is a submersed aquatic macrophyte that has colonized aquatic habitats across North America. Vegetative propagation is prevalent in M. spicatum and is highly visible, because of the extraordinary capacity of this plant to spread by fragmentation. Because of this, sexual propagation has been considered of limited importance and little is known about in situ seed germination of this species. Laboratory studies were conducted on seeds of M. spicatum to determine the light and temperature requirements necessary for maximum seed germination. Seed germination was also examined in situ at depths of 1, 3 and 5 m in two bays at Lake George, New York (USA). Significant germination of seeds was observed in the northern bay of the lake, but not in the southern, probably because of increased sedimentation in the latter. Temperatures higher than 15°C were found to be necessary for successful seed germination in laboratory studies; however, light was determined not to be a limiting factor on its own. Seeds buried under more than 2 cm of sediment were shown to experience significant decreases in germination.