Copper and cobalt in African species of Crotalaria L

Abstract

Nearly 1500 herbarium specimens of 284 of the 438 known species of African Crotalaria were analysed for their cobalt and copper content in order to identify accumulator species of interest for the fields of ecology, mineral exploration and plant physiology. Significant concentrations (> 5 $\mu $g/g Co and/or > 50 $\mu $g/g Cu) were found in C. cornetii Taub. & Dewevre, C. peschiana Duvign. & Timp., C. prolongata Baker, and C. variegata Welw. ex Baker, and a few other species. All except one species were from Central Africa and were found mainly in the 'Copperbelt' area of Zaire-Zambia. Accumulator species were confined to 4 of the 15 sections and subsections of the genus, and were found mainly in the closely related sections Dispermae and Crotalaria Longirostres. Discovery of metal accumulation by these species should assist further studies on their ecology and possible role in mineral exploration.