Physiological dormancy in forbs native to south–west Queensland: Diagnosis and classification

Seed physiological dormancy (PD) is reportedly the primary reason why many Australian native plants are not currently used for revegetation of degraded land. However knowledge of germination and dormancy of forb species from semi-arid environments is lacking. Consequently, we investigated germination of 15 Australian forb species from four families, particularly Asteraceae, native to south–west Queensland (Qld). Seeds were tested for viability using tetrazolium chloride (TZ) and sown at 5 to 35 °C. Nine species, including seven Asteraceae, achieved germination exceeding or not significantly lower (P > 0.05) than TZ test results. Despite spring dispersal, the majority of species had optimal germination at temperatures reminiscent of winter months. Only six species exhibited low germination across all temperatures investigated when compared to TZ results (P < 0.05), i.e. low germination could not be attributed to low seed viability. Of these, Actinobole uliginosum (Asteraceae) had non-deep PD since seeds responded to gibberellic acid (GA3) and dry after-ripening. In contrast, Goodenia fascicularis appeared to exhibit deep PD since seeds did not respond to GA3 or dry after-ripening, and scarification led to germination of abnormal seedlings. It appears that, contrary to expectations, seeds of many forbs native to south–west Qld (9 of 15 in this study), possess negligible or no dormancy and may therefore be suitable for use in land rehabilitation. Other species e.g. G. fascicularis require further work to investigate dormancy mechanisms and develop reliable germination techniques before seeds can be used effectively.