XVI International Botanical Congess

Smoke released from burning vegetation contains a chemical messenger that triggers seed germination of both fire climax and non-fire climax species from different parts of the world. The active constituent(s) is volatile, thermo stable, water soluble and long lasting. Smoke can be used as an effective seed pretreatment for breaking dormancy. Ecological studies have shown that there is no clear connection between a positive germination response to smoke and fire survival strategies, seed storage and dispersal, seed size and structure. Smoke treatment is most effective on seeds which have a light requirement for germination. A clear concentration effect resembling that of an hormonal response has been observed with aqueous smoke solutions. Interactions with plant hormones such as ABA, gibberellins, cytokinins and ethylene have been reported. Attempts to identify the active compound(s) and determine the mechanism of action have to date been unsuccessful. Smoke as a germination cue must have evolved as part of, or alongside, fire as an evolutionary factor, and as such, may be a very old development to serve as a protection mechanism to ensure germination at optimal times.