The effect of factors associated with fire on seed germination of Erica sessiliflora and E. hebecalyx (Ericaceae)

Seed Dormancy and Germination Responses of Nine Australian Fire Ephemerals

“…Ethylene, which is produced in smoke ( Van de Venter and Esterhuizen, 1988) and released from ash (Ne'eman et al, 1999), did not promote germination of any of the fire ephemerals examined, and although nitrate levels increase in the soil after fire (Christensen, 1973), nitrate only stimulated Actinotus leucocephalus to germinate. Although ethylene or nitrate stimulate the germination of many species from fire-prone areas, many other species from these areas are not responsive to these treatments (Keeley and Fotheringham, 1998;Thanos and Rundel, 1995;Van de Venter and Esterhuizen, 1988). Germination of Actinotus leucocephalus in response to nitrate supports the suggestion that some fire ephemerals can germinate in unburnt, nutrient enriched areas (Bell et al, 1984).…”

“…Heat and smoke are two of the main components of fire that are known to promote germination, and these can operate separately or in combination (Kenny, 2000;Morris, 2000;Thomas et al, 2003;Tieu et al, 2001). Germination has also been promoted by ethylene, which is a component of smoke (Van de Venter and Esterhuizen, 1988) and is released from wet ash (Ne'eman et al, 1999), and nitrate (Thanos and Rundel, 1995), which becomes more abundant in the soil following fire (Christensen, 1973). Gibberellic acid is a plant hormone that plays a role in releasing seed dormancy in many species (Bewley, 1997), including the fire ephemeral Codonocarpus pyramidalis (F.…”

Seed-Germination Patterns in Fire-Prone Mediterranean-Climate Regions

“…Heat-stimulated germination has also been shown for Elytropappus rhinocerotis (Levyns 1927) and Agathosma spp (Rutaceae) (Blommaert 1972). Erica hebecalyx (Ericaceae) germination is greatly stimulated by a 3-min treatment at 96.5°C, and this treatment is capable of overcoming the almost total inhibition imposed by darkness (van de Venter and Esterhuizen 1988). Podalyria calyptrata (Fabaceae) germination is increased from 9% (control) to 72% when seeds are exposed for just 1 min at 60°C (Jeffery et al 1988).…”

“…Pierce (1990) reported no such effect on germination of various coastal fynbos species, but these species had nonrefractory seeds that germinated readily under alternating temperatures. Van de Venter and Esterhuizen (1988) demonstrated that gases such as ethylene and ammonia, which are products of combustion, can stimulate germination of Erica hebecalyx. This species, however, seems also to be stimulated by heat shock, though it showed no response to charred wood (Keeley and Bond unpub.).…”

Promotion of germination of fynbos seeds by plant‐derived smoke

“…A number of factors have been proposed as being responsible for the effects of fire on germination. These factors include dry heat fracturing the seed coat of hard-seeded species (Gill, 1975;Jeffrey, Holmes & Rebelo, 1988), dry heat stimulating the seed embryo directly (Blommaert, 1972;van de Venter & Esterhuizen, 1988;Musil & de Witt, 1991); high-temperature desiccation of the seed coat (Brits & Brown, 1991); stimulation of germination by ethylene and ammonia contained in smoke (van de Venter & Esterhuizen, 1988), and less specifically, stimulation of germination by unknown chemical factors in plant-derived smoke and smoke extracts (de Lange & Boucher, 1990). Fire may also have an indirect effect on germination by causing changes in the soil temperature regimes in the immediate post-fire environments (Brits, 1986) or by resulting in mineral enrichment of the soil by ash (Levyns, 1935).…”