The Role of the Cell Wall in the Intracellular Uptake of Cations by Lichens

Abstract

When lichens or bryophytes are placed in solutions containing cations, an equilibrium is rapidly achieved between free cations in solution and cations bound to the exchange sites on the cell wells. For a given cation the extent of this process depends on the nature of the exchange sites, the affinity of the ion for these sites and the nature and number of pre-existing cations (Nieboer et al., 1978; Nieboer and Richardson, 1981; Brown and Beckett, 1984, 1985). With low concentrations of “heavy” metals in limited volumes of solution lichens and bryophytes can significantly reduce the cation concentration in solution. As heavy metal cations are effectively bound outside the plasma membrane, which surrounds the metabolically active cytoplasm, such binding might represent an apparent means of detoxifying the solution.