Studies on serpentine flora : Preliminary analyses of soils and vegetation associated with serpentinite rock formations in the south-eastern Transvaal

Abstract

Soils sampled from sites adjacent to two disused mines in the Barberton district were found to be derived from ultrabasic rocks. The soils contained elevated concentrations of Ni and Cr. Although potentially phytotoxic, the soils supported a relatively diverse flora. Samples of six species collected from both sites had unusually high root and leaf tissue concentrations of Ni, suggesting physiological tolerance of the metal. Berkheya coddii Roessl. showed hyperaccumulation of Ni in leaves and is likely to be endemic to nickeliferous serpentine; it may also have value as a geobotanical indicator species. Only Sporobolus pectinatus Hack. and Sutera sp. aff. S. silenoides Hilliard absorbed Cr from soil solution and translocated it to leaves. Uptake and translocation of Cr is rare and the physiological mechanisms of Cr tolerance in these species remains unclear. Grondmonsters is in die Barbertonse distrik, in die omgewing van twee myne wat nie meer bewerk word nie, versamel. Die grond is gevorm uit basiese gesteentes. Die grond het hoë konsentrasies Ni en Cr bevat. Alhoewel die grond potensiaal fitotoksies is, kom ’n relatief diverse flora daarop voor. Monsters van ses plantsoorte wat op albei lokaliteite versamel is, het ongewoon hoë Ni-konsentrasies in beide die wortels en blaarmateriaal gehad, wat dui op die fisiologiese verdraagsamheid van die spesies teenoor die metaal. Berkheya coddii Roessl. hiper-akkumuleer Ni in die blare en is heelwaarskynlik endemies op nikkeldraende serpentyngesteentes; dit mag van waarde wees as ’n geobotaniese indikator-spesie. Slegs Sporobolus pectinatus Hack, en Sutera sp. aff. S. silenoides Hilliard absorbeer Cr uit die grondoplossing en translokeer dit na die blare. Die opname en translokasie van Cr is ’n seldsame verskynsel en die fisiologiese meganismes wat verantwoordelik is vir die verdraagsaamheid van Cr in die spesies is nog onduidelik.