Toxicity of Metal Elements on Germination and Seedling Growth of Widely Used Medicinal Plants Belonging to Hyacinthaceae

In South Africa, pollution of agricultural soils is on the increase primarily due to excessive application of fertilizers, sewage disposal and mining activities. This study was done to determine the effect of trace elements (Cu, Zn) and heavy metals (Cd, Pb, Hg) on germination and seedling development of Bowiea volubilis, Eucomis autumnalis and Merwilla natalensis. These medicinal plant species are highly recommended for cultivation in South Africa to reduce the pressure on wild populations. Copper and Zn at 1 mg L-¹ significantly (p < 0.05) reduced the percentage germination of E. autumnalis. Low concentrations (>=1 mg L-¹) of Cu and Zn negatively affected the roots of all three species. Mercury concentrations of 0.5 and 1 mg L-¹ significantly (p < 0.05) decreased the percentage germination of B. volubilis and E. autumnalis respectively. Cadmium and Hg at 2 mg L-¹ showed a detrimental effect on the root growth of B. volubilis. Concentrations of 0.5 mg L-¹ of all heavy metals tested significantly (p < 0.05) decreased shoot length of M. natalensis.