Water Crowfoot (Ranunculus penicillatus subsp.
pseudofluitans (Syme) S.Webster) plants were grown in two artificial
recirculating rivers, in one of which the phosphate concentration of the input
was raised from 40 µgPl-1 to 200 µgPl-1. Fennel Pondweed (Potamogeton
pectinatus L.) plants were planted as a competitor in association with 50%
of the Ranunculus clumps. Chemical concentrations of the major elements
in the water were measured weekly. Filamentous algae grew in profusion in the
channel with added phosphate (0.77 T fresh weight), compared with an immeasurably
low amount in the control channel. After 100 days the plants were removed, dried
and weighed and the tissue concentrations of the major elements were measured.
The Ranunculus shoots grew less in the eutrophic channel, and its roots
grew less in the presence of Potamogeton. The Potamogeton showed
a greater reduction in shoot and root biomass than the Ranunculus. Tissue
phosphate concentrations were higher in both species in the eutrophic channel.
The data suggested that P. pectinatus is a more competitive species (sensu
Grime) than R. penicillatus.