THE UPTAKE OF HEXOESTROL BY PLANTS AND ITS PERSISTENCE IN SOIL

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Abstract
SUMMARY 1. A grass-clover mixture and turnips were grown on control plots and on plots dressed with hexoestrol at rates of 3·7 and 14·8 g/acre; that applied at the lower rate was labelled with tritium. 2. No oestrogenic activity was detected in any of the crop samples taken at intervals over 4 months, indicating that the hexoestrol content was less than the minimum which was detectable: between 10 and 19 μg/kg fresh weight. 3. The specific activities of plant samples from the plots dressed with labelled hexoestrol corresponded to 0·12–0·49 μg hexoestrol/kg fresh weight which is clinically insignificant for the consumer. 4. The presence of an unidentified oestrogen, with marked local variations in concentration, was detected in the soil of the control plots. 5. Bioassay and tritium determinations on soil extracts showed that the method used extracted 20% or less of the applied hexoestrol. 6. During 3 months there was no appreciable change in the specific activity of the soil dressed with labelled hexoestrol, showing that neither hexoestrol nor any possible decomposition products had been lost by evaporation or by leaching. 7. It required 7 days' continuous treatment with ethanol in a soxhlet apparatus before the calculated amount of radioactivity was extracted from soil samples taken at the beginning and end of the experiment, dried by heat and stored for several months. Only 9–11% of the radioactivity in the extracts was in the chemical form of hexoestrol. The significance of this is discussed.