Studies were undertaken on the seeds of four Acacia species-Acacia albida, Acacia senegal, Acacia tortilis, Acacia nilotica-considered to be the most important for dry land afforestation. Seed dormancy caused by an impermeable seedcoat is the main problem to overcome if planting programmes for these species are to be successful. Twelve provenances for the four species were used in this study which involved presowing treatments in cold water, hot water, sulphuric acid and a hot-wire scarifier. Seed coat dormancy was observed in three of the four species but no dormancy was evident in the three provenances of A. senegal. The duration of water treatments used did not appreciably increase level of germination, but both the sulphuric acid and hot-wire treatments increased germination to 80% and above in all provenances. The hot-wire treatment showed clear evidence of an optimum treatment duration of between 5 and 10 s for nearly all the provenances. It is concluded that hot wire presowing treatment is worth considering as an alternative to sulphuric acid because of safety problems associated with handling the acid. The hot wire as a prototype requires some modifications to enable more seeds to be pretreated at a time.
