Heavy metal tolerance in plants: A model evolutionary system.
- M R Macnair
- Trends in ecology & evolution
Succisa pratensis Moench is an ecologically wide-ranging hemicryptophytic plant species. The wide ecological amplitude is at least related to edaphic factors such as wide variation in soil pH from strongly acid to alkaline, and variation in soil wetness from aerobic to anaerobic. Al and Mn are generally considered important growth-limiting factors of many acid (sub) soils, whilst both reduced Mn and Fe are soluble and many reach phytotoxic concentrations when soil is oxygen-depleted after flooding. The growth of young individuals of two populations from contrasted ecology was compared: one from a dry heath vegetation on acid podzol, and one from a waterlogged fen meadow vegetation on non-ripened raw peat with ripened top. Seedlings raised from fruits were grown on a complete nutrient solution situated in a controlled environment. Various concentrations of the microelements Al, Mn and Fe at high acidity (pH 3.8) were used separately. It appeared that both populations showed the same response curve to concentrations of the three elements. Al did not differentiate between them, while the production of the waterlogged fen meadow population was less inhibited by either Mn or Fe compared to that of the dry heath population. These results may indicate that the wide ecological amplitude of this species is partly achieved by genetic differentiation into separate populations (edaphic ecotypes) as far as Mn and Fe are concerned. The study is used to evaluate generalization from experiments on genetic variation and phenotypic plasticity as adaptive responses to contrasting habitats.