Scarification of seeds of Acacia angustissima (Mill.) Kuntze and its effect on germination

Field germination of Acacia angustissima (Mill.) Kuntze, a N-2-fixing tree whose bark is traditionally extracted for tannins used in the leather industry, takes up to 55 days and the percentage of germination is generally less than 20%. Abrasion, dry or wet heat, or immersing the seeds in different concentrations of sulphuric acid, chloric acid or hydrogen peroxide for different lengths of time, were tested as germination enhancers. The application of dry heat resulted in < 37% germination, less than the 44% found for untreated control seeds. The application of wet heat for less than or equal to 30 s and abrasion for 1200 s resulted in 69% germination. Immersing seeds in concentrated H2SO4 for 900 s resulted in 77% germination while diluting H2SO4 or longer exposure to concentrated H2SO4 decreased it. Immersing the seeds in concentrated or diluted H2O2 also increased germination, but to a lesser extent than when immersed in H2SO4. We found that the exposure of seeds of A. angustissima to concentrated H2SO4 for 900 s appeared to be the best technique to stimulate their germination; the treatment gave the largest percentage of germination in the shortest time, the technique is easy to apply and many seeds can be treated at once.