Patterns in the seed germination response to smoke in plants from the Cape Floristic Region, South Africa

De Lange and Boucher (1990) discovered the germination enhancing effect of plant-derived smoke on seed of fynbos species. This finding has been applied to horticulturally important fynbos species and to date 301 species have been tested for a response to smoke. Germination in 150 (49.8%) of these was significantly improved by smoke treatment; the remaining 151 species showed no significant response. Families in which species showed a significant response included the horticulturally important Asteraceae (everlastings), Bruniaceae (brunias), Crassulaceae (crassulas), Ericaceae (ericas), Geraniaceae (pelargoniums), Mesembryanthemaceae (mesembs), Proteaceae (proteas) and Restionaceae (restios). No species responded in the families of geophytes such as Amaryllidaceae and Hyacinthaceae and in the Iridaceae the majority of species studied (also geophytes) did not respond. Further analysis of the germination results using ordinal logistic regression confirmed that the geophytic growth form was a robust predictor of response to smoke; geophytes exhibited a very low germination response to smoke. In addition, the analysis indicated that serotinous species had seeds that were less likely to respond to smoke than non-serotinous species, presumably as a consequence of their seeds not being in the soil when fire occurs. It also indicated that plants with some capacity to re-sprout were less likely to respond to smoke than obligate seeders.