FURTHER INDICATIONS THAT ETHYLENE IS THE GIBBOSITY REGULATOR OF THE LEMNA GIBBA/LEMNA MINOR COMPLEX IN NATURAL WATERS

In the laboratory flat forms of the Lemna gibba/Lemna minor complex which are potentially gibbous, swell up in the presence of extremely low concentrations of ethylene (from 24 nl/l air upwards). In control cultures, where the ethylene concentration is 16 nl/l air or lower, the plants remain flat. In ditches in the Netherlands ethylene concentrations occur which are in the same range as the concentrations which induce gibbosity in the laboratory. These are further indications that ethylene is the gibbosity regulator of the Lemna gibba/Lemna minor complex in natural waters.