Burkea africana and Erythrophleum africanum are characterized by seed coat-imposed dormancy that prevents water entry and gaseous exchange, which are essential for the germination process. The objective of this study was to determine the best possible pre-sowing treatment method that maximizes seed germination of the two species. Seeds of both species were subjected to four experiments, containing 10 levels of presowing treatments: The control, mechanical scarification, soaking in concentrated sulphuric acid (for 15, 30, 45 and 60 min), immersion in boiling water (for 1, 3 and 5 min), and soaking in boiling water (and cooling down for 24 h). The germination data were subjected to ANOVA followed by Tukey's HSD Test to separate significantly different treatment means. The most promising results showed that seeds treated with mechanical, sulphuric acid and boiling water scarification had significantly higher mean percent germination than the controls for B. africana; whereas for E. africanum, mechanical scarification, exposure to sulphuric acid, boiling water (1 min) and immersion in boiling water (and cooling down for 24 h) had higher percent germination than the controls.

Cassia abbreviata and Senegalia nigrescens are indigenous trees found in North and Central regions of Botswana. However, inadequate knowledge of their silviculture and decline in population due to deforestation, expanding settlements, infrastructure and agriculture are major threats to most indigenous tree species in Botswana. Like many indigenous tree species, Cassia abbreviata and Senegalia nigrescens are slow-growing and are threatened by overexploitation for numerous uses. Because of the increased demand for medicinal uses, medicinal species such Cassia abbreviata are rapidly disappearing in many habitats and threatened to extinction. This study assessed the response of pre-sowing treatment methods on quiescency and germination of seeds of Cassia abbreviata and Senegalia nigrescens tree species found in semiarid Savanna Ecozone of Botswana. Pre-sowing treatment included immersion in 98% undiluted sulfuric acid (H2SO4) for 15, 30, 45 and 60 minutes, submergence in boiling water for one, two, three minutes and submerged in warm water for 24 hours, mechanical scarification of the seed coat and control. ANOVA showed that there is a highly significant difference (P < 0.0001) among the treatments of C. abbreviata in seed germination and no significant difference among the treatments of S. nigrescens. The highest germination percentage of C. abbreviata seeds was 81%, which was found from seeds immersed in H2SO4 for 30 minutes, while for S. nigrescens seeds, the highest germination percentage was 99%, which was found from seeds treated with mechanical scarification and those immersed in H2SO4 for 15 and 45 minutes. The objective of this study is to determine the effect of pretreatment methods on germination of C. abbreviata and S. nigrescens seeds. Based on these results, we recommend sulphuric acid and mechanical scarification as suitable seed pre-sowing treatments for enhancing the germination of C. abbreviata and S. nigrescens, respectively.

The effect of seed presowing treatment on Guibortia coleosperma and Amblygonocarpus andongensis was investigated. Seeds of both species were subjected to four experiments, containing 10 levels of presowing treatments: mechanical scarification, soaking in concentrated sulphuric acid (for 15, 30, 45 and 60 min), immersion in boiling water (for 1, 3 and 5 min), and soaking in boiling water (and cooling down for 24 h) and the control. The germination data were subjected to ANOVA followed by Tukey's HSD test to separate significantly different treatment means. The highest germination in G. coleosperma was recorded: mechanical scarified seeds, those soaked in sulphuric acid (15, 30, 45 and 60 min), hot water (and cooling down for 24 h) and the control seeds. For A. andongensis, seeds treated with mechanical scarification, exposure to sulphuric acid (15, 30, 45 and 60 min) and boiling water (1 min) had higher percent germination than the controls.