Germination of Pterocarpus angolensis DC. and evaluation of the possible antimicrobial action of the phloem sap

Abstract

The Transvaal teak (Pterocarpus angolensis) is being over utilised in its natural habitat, although it is a protected tree in South Africa, Swaziland and Namibia. The phloem sap of this species has several traditional, medicinal uses and the wood is used primarily for furniture and fuelwood. The aim of this study was firstly, to determine which seed pre-treatments would ensure optimal germination and secondly, to evaluate the potential antimicrobial activity of the phloem sap. The initial germination trial was conducted by using unsterilised seeds in the dark, which resulted in low germination rates (7.78%) and high percentages of fungal infections (45.56%), primarily Aspergillus niger and a Fusarium sp. In the second experiment the seeds were sterilised with a mixture of 60 g Thiram and 70 g Captan and germinated in an alternating light/dark environment. In both experiments the seeds were subjected to either a hormonal, heat or control pre-treatment and were allowed to germinate at three different temperature regimes. Different sap concentrations were tested for antimicrobial activity against both gram positive (Staphylococcus aureus) and gram negative (Escherichia coli; Pseudomonas aeruginosa) procaryotes as well as two eucaryotes (Candida albicans; Aspergillus niger), with negative results. The phloem sap was analysed by means of GC-MS and a few compounds, which have been identified, are reported.