Copper tolerance and accumulation in two cuprophytes of South Central Africa: Crepidorhopalon perennis and C. tenuis (Linderniaceae)

Crepidorhopalon perennis is an endemic metallophyte restricted to only one site on Cu-rich soils in Katanga. Crepidorhopalon tenuis has a broader niche, from normal to Cu-rich soils, but has high affinity for cupriferous habitats. Both plants have been considered as Cu-Co accumulators. Cu tolerance and accumulation of C. tenuis were studied in axenic conditions in vitro in four metallicolous populations and one non-metallicolous population whereas for C. perennis only one population was investigated. Results showed a Cu tolerance of both C. tenuis and C. perennis. Variation of tolerance among metallicolous and non-metallicolous populations was also observed. The addition of Cu enhanced the growth of some metallicolous populations under sterile conditions, hence confirming the high needs in copper of metallicolous populations. This could represent a cost of tolerance which would explain the high affinity of species for cupriferous habitats. On the other hand, Crepidorhopalon perennis did not show the same features. Its restricted distribution may be explained by a cost of Cu tolerance. Crepidorhopalon perennis and C. tenuis are not Cu hyperaccumulators and seem to behave rather like excluder species. (C) 2012 Elsevier B.V. All rights reserved.