Scientific Note: Effects of Smoke on Seed Germination of Twenty Species of Fire-Prone Habitats in Florida

Studies conducted in many parts of the world over the past 20 yr have shown that smoke can induce seeds to germinate, especially those of species native to fire-prone habitats. Chemicals in smoke may signal to the seed that environmental conditions are favorable for its germination and growth (Roche, Koch, and Dixon 1997). However, smoke stimulated germination appears to have developed even in some species that are not native to fireprone habitats (e.g., lettuce; Jager et al. 1996). In fire-prone habitats around the world, including the California chaparral (Keeley and Fotheringham 1997), South African fynbos (Brown et al. 2003), Western Australian shrublands (Morris 2000), and northeastern Australian savannas (Williams et al. 2005), seeds of a wide range of species germinate in response to cues from 3-methyl-2H-furo[2,3c]pyran-2-one in smoke (Flematti et al. 2004). Some plants, such as the Australian Grevillea spp. , show a significant increase in germination after exposure to smoke compared to other signals such as scarification or heat shock (Morris 2000). In Western Australia, 45 of 94 species responded positively to smoke fumigation (Dixon et al. 1995). Five of eight species in the same experiment known to require heat or scarification treatment for germination showed a seven-fold greater germination percentage following smoking, indicating that smoke alone is sometimes sufficient to induce high germination percentages in some species. Here we report the results of testing seeds of 20 Florida plant species for smoke induced germination, using five levels of smoke exposure (0, 1, 5, 10, and 30 min of aerosol smoke). Upland Florida ecosystems such as Florida scrub, sandhill, and flatwoods are shrublands dominated by xeromorphic plants resilient to periodic fires. Most fires occur early in the growing season, during late spring droughts (Menges 1999). Smoke-stimulated germination may be particularly important for species that require seedling recruitment to recover post-fire (Weekley and Menges 2003). Seeds often lie dormant until the right cues stimulate them to germinate (Baskin and Baskin 1998). Many upland Florida species are specialized for the first decade post-fire and recruit many seedlings in that time period, e.g., Eryngium cuneifolium Small (Menges and Quintana-Ascencio 2004) and Polygala lewtonii Small (Menges and Weekley 2004). The primary purpose of this study was to determine if any upland Florida species have smoke-responsive germination. We hypothesized that the long history of fire in this region has led to some species to use smoke as a germination cue. Seeds were collected from 20 species of upland plants from Highlands and Polk Counties in south-central Florida: Abrus precatorius L. , Bejaria racemosa Vent. , Callicarpa americana L. , Chamaecrista fasciculata (Michx.) Greene, Crotolaria pallida Aiton, Dicerandra frutescens Shinners subsp. frutescens, Eryngium cunefolium, Garberia heterophylla (W. Bartram) Merr. & F. Harper, Lechea deckertii Small, Liatris chapmanii Torr. & A. Gray, Liatris ohlingerae (Blake) Robinson, Opuntia humifusa (Raf.) Raf. , Pityopsis graminifolia (Michx). Nutt. , Polygala lewtonii, Polygonella basiramia (Small) G.L. Nesom & V.M. Bates, Polygonella robusta (Small) G.L. Nesom & V.M. Bates, Rhus copallinum L. , Serenoa repens (Bartr.) Small, Sisyrinchium xerophyllum Greene, and Ziziphus celata Judd & D.W. Hall. Seeds of Ziziphus celata were collected from plants introduced to Historic Bok Sanctuary in Lake Wales in 2002, and those of Polygala lewtonii from The Lake Wales Ridge National Wildlife Refuge, Carter Creek Tract, Sebring in 2004. All other species’ seeds were collected at *email address: heather.lindon@gmail.com Received 4 July, 2007; Accepted 14 January, 2008. CASTANEA 73(2): 106–110. JUNE 2008