Breaking seed dormancy in Philenoptera violacea (Klotzsch) Schrire using different pre-sowing treatment methods

Seeds of many woody plant species cannot germinate even if they are sown under optimal moisture, oxygen and soil conditions because of hard seed coat dormancy. A seed germination experiment to evaluate the suitability of various dormancy breaking methods in Philenoptera violacea seeds was conducted in the laboratory of the Department of Crop Science and Production, Botswana University of Agriculture and Natural Resources (BUAN) between November and December 2017. A completely randomized design (CRD) with 10 treatments, involving; control (untreated seeds), mechanical scarification, hot water (24 hours), boiling water (1, 3 and 5 minutes) and concentrated sulphuric acid (15, 30, 45 and 60 minutes) was used. Germination percentage, germination mean time (GMT) and germination index (GI) were significantly (P <0.01) affected by seed dormancy breaking methods. The highest germination percentages were recorded in seeds immersed in concentrated sulphuric acid for 15 and 30 minutes (100%), followed by concentrated sulphuric acid 45 minutes and hot water for 24 hours (99%), mechanical scarification (98%) and concentrated sulphuric acid for 60 minutes (97%), which were significantly higher than the rest, boiling water being the least. Untreated seeds took the longest time (20.50 days) for 86% of the seeds to germinate whereas the shortest significant GMT (2.23-2.66 days) was recorded for maximum germinations (100%). Boiling water (1, 3 and 5 minutes) revealed significantly lower GI (0.00-0.02). Although, 86% of untreated seeds germinated, the present findings emphasize the importance of treating P. violacea seeds before sowing to promote quick and uniform germination.