Kamogelo Makgobota

This study aimed to evaluate the size of Senegalia mellifera seeds and determine the most effective scarification techniques to improve germination. The experiment, conducted at Botswana University of Agriculture and Natural Resources, involved ten presowing treatments, including control, nicking, soaking in sulphuric acid for different durations, and boiling water for varying periods. A completely randomized design (CRD) was used for the experiment. Germination data was transformed using arcsine to meet normal distribution requirements and then analyzed using analysis of variance (ANOVA). The results showed that the presowing treatments had a statistically significant effect on germination (P<0.00001). Seeds treated with sulphuric acid, nicking, and those left untreated exhibited the highest germination rates, while seeds treated with boiling water showed the lowest germination percentages. These findings indicate that the seed coats of S. mellifera are permeable to water and air, and presowing treatments do not show any significant effect on the successful germination of S. mellifera seed.

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.