The effects of water level variation on the growth of Myriophyllum aquaticum
Myriophyllum aquaticum (Haloragaceae, EPPO List of Invasive Alien Plants) is not typically a weed problem as water level increases, despite its submersed leaf form. As little data exists describing basic biological and ecological mechanisms affecting the development of this species, a study to quantify changes in M. aquaticum growth as water level increases was conducted. M. aquaticum was subjected to different water levels from 0 to 137 cm deep and one flood duration of 12 weeks. It appeared that M.;aquaticum was negatively affected as water levels increased, with the exception of submersed shoot biomass that increased at intermediate water levels. The plant responded quickly to immersion, by changing leaf morphology. However, plants in deeper water levels were unable to grow to the water surface and to start an emergent growth.
The data suggest that this species does not grow well under sustained deep flood conditions and that M. aquaticum is rather limited to shallow areas where fragments can root and plants can grow rapidly to the water surface and establish an emergent canopy.
Wersal RM ; Madsen JD (2011) Comparative effects of water level variations on growth characteristics of Myriophyllum aquaticum. Weed Research 51, 386-393.