Dormancy release in Australian fire emphemeral seeds during burial increases germination response to smoke water or heat

Fire ephemerals are short-lived plants that primarilygerminate after fire. Fresh and laboratory-storedseeds are difficult to germinate ex situ, even inresponse to fire-related cues such as heat and smoke.Seeds of eight Australian fire ephemeral species wereburied in unburnt and recently burnt sites of naturalbushland during autumn. Seeds were exhumed after6 and 12 months and incubated in water and smokewater, either with or without a heat treatment at 708C for1 h. Generally, germination did not increase after 6months of burial, but after 12 months of burialgermination was enhanced in seven of the eightspecies. Actinotus leucocephalus produced highergermination following 12 months of burial without anyfurther treatment, and smoke water and heat furtherimproved germination. The four Gyrostemonaceaespecies, Codonocarpus cotinifolius, Gyrostemonracemiger, Gyrostemon ramulosus and Tersoniacyathiflora, only germinated in the presence ofsmoke water, and their germination was enhancedby burial. Burial improved germination in response to aheat treatment in Grevillea scapigera and Alyogynehuegelii seeds, but did not enhance Alyogynehakeifolia germination. During concurrent dry laboratorystorage of seeds at 158C, only Actinotusleucocephalus produced increased germination inresponse to smoke water and heat over time. Insummary, soil burial can alter the dormancy status of anumber of Australian fire ephemeral seeds, renderingthem more responsive to germination cues such assmoke water and heat. The requirement for a period ofburial before seeds become responsive to smokeand/or heat would ensure that seeds persist in the soiluntil a subsequent fire, when there is an increase innutrients available for growth and reduced competitionfrom other plants.