Ecological studies on Potamogeton pectinatus L. V. Nutritional ecology, in vitro uptake of nutrients and growth limitation

Abstract

The growth of Potamogeton pectinatus L. at different concentrations of bicarbonate, phosphate and nitrate was studied during long-term culture experiments in aquaria. The uptake of bicarbonate, phosphate, nitrate and ammonium by the shoots or the root system was studied during short-term experiments in 2-compartment chambers. When P. pectinatus was cultured without a phosphorus source, the tubers were able to supply phosphorus and enable growth for about 5 weeks before the plants died. Depletion of nitrate or dissolved inorganic carbon (DIC) caused a rapid death of plants. Potamogeton pectinatus takes up phosphorus and nitrogen with the shoots and the root system, bicarbonate can only be taken up by the shoots. The nutrient contents of plants indicated luxury consumption of phosphorus at high external phosphate concentrations. Critical phosphorus concentrations for plant growth according to biomass production in cultures at different external phosphate concentrations are supposed to be between 1.5 and 14 μmol 1 −1 phosphate. Analysis of plant tissue shows that the critical phosphorus content is 0.15%, which corresponds with a stock phosphate concentration between 3 and 4 μmol PO 4 3− l −1. It is argued that phosphate and nitrate are probably not limiting growth of P. pectinatus in the Veluwemeer study site (The Netherlands), but DIC might well be.