In the last few years the interest in the behavior and possible function of trace elements in biological systems has strongly increased. This seems to be stimulated by three different factors: i. e. 1. the slowly growing notion about the importance of some essential elements in the metabolism of plants and animals, including man, 2. the increasing extent of environ mental contamination caused by the disposal of heavy elements - both essential and toxic - and 3. the increasing sensitivity achieved in the analysis of these elements by modern techniques. The impact of the last mentioned...