Stable isotope tracer technique as a tool to increase the sensitivity of plant growth bioassays - Investigations with pentachlorophenol and trichloroacetic acid

The Lemna growth test is used to study the uptake of C-13-labelled organoch lorines (Pentachlorophenol, Trichloroacetic acid) into the plants as well a s their effect on the incorporation of N-15 labelled nutrients into the pla nts' nitrogen fraction simultaneously. There was to observe a time- and a c oncentration dependent incorporation of C-13 labelled Pentachlorophenol (10 to 1,000 mu g L-1) into Lemna gibba and Lemna minor and an inhibition of N -15 incorporation into the plants. The effect parameter N-15 tracer incorpo ration was about twice as sensitive as the growth rate over 7 days. On the other hand no incorporation of C-13 labelled Trichloroacetic acid (50 to 80 0 mu g L-1) into Lemna gibba was to be observed within 24 hours and there w as no effect on N-15 incorporation either.