Influence of aqueous extracts of plants from the shoreline of a reservoir on growth and element-composition of duckweeds.

Aqueous extracts of Trifolium repens L. and Polygonum lapathifolium L. were added to water from the Bleiloch-Reservoir (Thuringia). In a pilot study this solution enhanced the growth of the duckweed Lemna minor L., based on the increased nutrient supply, especially of potassium and phosphorus. Released nitrogen did not influence the biomass-production of Lemna compared to the water from the reservoir, obviously nitrogen was not limiting. Other released nutrients had lower importance to Lemon as was demonstrated by comparison of plant growth with the accumulated nutrients from the medium.