Uptake of lead by two populations ofGrimmia doniana

Analyses of populations of Grimmia doniana from Old Red Sandstone walls (Brecon Beacons, Breconshire) and vitrified lead slag (Charterhouse, Somerset) showed the former to have a low and the latter a high lead content. Lead in material from the field was shown to be ionically bound to an extracellular site. Uptake of lead from solutions of lead nitrate was by a passive physical process, without penetration of the cytoplasm. No difference in lead uptake capacity was detected between the two populations. The results are discussed in terms of a natural non-specific lead tolerance mechanism occurring in Grimmia doniana.