Effect of seed treatment on the emergence of Cassia brewsteri and Lysiphyllum carronii seeds stored in soil

Dormancy-breaking treatments are applied to seeds of many Australian species used for mine-site restoration in arid and semi-arid regions of Australia. Once seeds are sown, several months may pass before a rain event sufficient for germination. Therefore, it is important that treated seeds are able to survive in soil until conditions are hospitable for germination and growth. However, little is known about the effects of seed dormancy-breaking treatments on the longevity of seeds in soil. Two species that are potential candidates for use in mine site restoration programs in Queensland were trialed viz., Cassia brewsteri (F.Muell.) Benth and Lysiphyllum carronii (F.Muell.) Pedley. Untreated, boiled and acid treated seeds of the two species were sown in soil in a glasshouse. Seeds were watered immediately or kept dry for one or three months before watering and emergence was assessed. When applied to seeds incubated on filter paper in a germination cabinet, boiling and acid treatments were effective methods of breaking dormancy and increasing germination for both C. brewsteri and L. carronii seeds. However, in soil, seedling emergence from boiled seeds was the same or less than that of untreated seeds. Storage time in soil before watering had little effect on seedling emergence in the glasshouse, suggesting that most decreases in emergence compared with laboratory germination occurred after the input of water to the system. Treatments that promote germination in the laboratory can reduce seedling emergence in soil. Thus, treated seeds should be tested for survival in soil before use in mine-site restoration programs.