The adaptive significance of plasticity was evaluated for eight genotypes of Lemna minor L. based on two inter-related assumptions: a display of plasticity in the form of increased growth rate after environmental amelioration is directly more adaptive than an absence of plasticity; and a display of plasticity in the form of decreased growth rate after deterioration of environmental conditions has no direct adaptive interpretation, and may be less adaptive than an absence of plasticity if the decreased growth rate implies decreased fitness (...)