Improved germination of the Australian natives: Hibbertia commutata, Hibbertia amplexicaulis (Dilleniaceae), Chameascilla corymbosa (Liliaceae) and Leucopogon nutans (Epacridaceae)

Hibbertia commutata (Steudel), H. amplexicaulis (Steudel), Chameascilla corymbosa [(R.Br.) F.Muell. Ex Benth.] and Leucopogon nutans (E.Pritzel) are four Australian species that are difficult to germinate during mine-site rehabilitation. Laboratory germination trails were conducted to identify dormancy mechanisms and to improve germination response. Treatments applied to all species included scarification and scarification followed by soaking seeds in smoke water (1, 5 or 10%) or gibberellic-acid solution (50, 200 or 1000 μM). Additional treatments with kinetin solution (50, 200 or 1000 μM) and smoke water (50 or 100%) were applied to scarified or unscarified seeds of C. corymbosa. Thermal-shock treatment was applied to L. nutans fruit, some of which were subsequently scarified and subjected to both smoke water (10%) and gibberellic-acid solution (1000 μM). Significant germination increases were obtained by using dormancy-breaking treatments on H. commutata (from 12.8 to 76.0%), H. amplexicaulis (from 6.8 to 55.1%) and C. corymbosa (from 48.5 to 86.4%). Scarification alone increased germination of both Hibbertia species, suggesting that these species display a physical seed coat-imposed dormancy mechanism. Germination of H. amplexicaulis was further increased by the application of gibberellic-acid solution, indicating a possible embryo-imposed dormancy mechanism. Scarification followed by the application of smoke water produced the highest germination response for C. corymbosa seeds. Scarification alone did not significantly increase germination, inferring the existence of a smoke-responsive embryo dormancy mechanism. Seeds of L. nutans, although viable, failed to germinate and are thought to display complex seed coat- and embryo-imposed dormancy mechanisms.