The experiments in this study successfully covered the range of responses to copper from deficiency via optimal growth to lethal toxicity. Furthermore, the long (compared to almost all earlier studies) duration of these experiments, six weeks, combined with 10 different copper concentrations, allowed for analysis of threshold concentrations and time sequences. In this way it was possible to establish a sequence of events leading to optimal or suboptimal growth, as presented in detail below. The results have been shown as 2D graphs in the figures and their line graphs in the supplement.