Methods for Breaking Seed Dormancy in Acacia Species

Seeds of six species of Acacia namely, Acacia nilotica (L.) Delile, A. tortilis (Forssk.) Hayne, A. victoriae Benth, A. trachycarpa E. Pritz., A. leucophloea (Roxb.) and A. holosericea G. Don were subjected to various physicochemical treatments to break the hard seed coat imposed dormancy. The treatments included immersing in hot water (different temperatures for varying duration), chemical scarification with concentrated sulphuric acid (varying duration), subjecting seeds to dry heat (16 hrs in an air-circulated oven at 65±1°C), pouring boiling water over seeds and mechanical abrasion and scarification using sand paper. The treatments resulted in significant improvement in the germination percentage in all the species, however, the response of the species differed to the various treatments. Maximum germination (60%) could be achieved in A. nilotica by mechanical scarification. In other species better germination (70–100%) could be achieved by various treatments. Sulphuric acid treatment for 20 and 50 minutes produced the best results for A. leucophloea and A. tortilis. Hot water treatment at 70°C for 30 min was found best for A. trachycarpa and A. holosericea and 80°C for 10 min was more effective in improving the germination of A. victoriae. Other treatments were beneficial to the different species to various extents.