Clonal lines of the submersed aquatic angiosperm Potamogeton pectinatus were grown in three culture systems. The first, which used sucrose as a carbon source in a liquid medium, supported vigorous vegetative growth and can be used to propagate large numbers of plants in axenic conditions. In this culture system, plants were responsive to increasing photosynthetically active radiation (PAR) photon flux density (PFD) and were photosynthetically competent. However, their growth was heterotrophic and root development was poor. When these plants were transferred to a second nonaxenic culture system, which used 16-l buckets containing artificial sediments and tap water, growth was autotrophic and plants were morphologically identical to field-harvested P. pectinatus. The last culture system which consisted of a sand substrate and inorganic nutrient bathing solution aerated with 135 ml min-1 ambient air enhanced to 3.0% CO2 was axenic and supported autotrophic growth by plants that were also morphologically normal.