Scientists Investigate Smoke as Trigger for Seed Germination

To the dismay of many Californians, and most recently Floridians, nearly every summer it happens. Trees alight in a fiery blaze, resulting in millions of dollars in property damage, displaced families, and in some instances the loss of life. All thats left after the last ember dies out is a charred, skeleton forest. Yet the next generation of forest lies beneath the scorched soil as once dormant seeds are awakened. In the October issue of Ecology, scientists investigate the mechanisms behind fire-triggered seed germination, and focus specifically on the role of smoke.

Scientists have previously reported that heat shock and charred wood induce germination in dormant seeds. In their study of California chaparral, Jon E. Keeley, of the USGS Biological Resources Division, and C. J. Fotheringham, of California State University, show that smoke also triggers germination in deeply dormant seeds.

Keeley and Fotheringham compared seed characteristics of species stimulated by smoke to those stimulated by heat shock, and the different mechanisms behind germination. Seeds that germinate after exposure to smoke are distinctly different from those that do not:

outer seed coats are highly textured
have a poorly developed outer cuticle
are missing dense tissue in the coat of the seed
have a membrane which allows water to pass through but not larger particles

Smoke triggers germination directly by penetrating the seed, as well as indirectly, by vapor or liquid transfer from soil to seeds.

The scientists found, within the smoke-stimulated plants, that a variety of factors trigger germination. Such factors are: charred wood, Nitrogen dioxide, duration of exposure to smoke, soil content and moisture level, and the influence of day and night. In some species, exposure to smoke alone was enoug
'"/>

Contact: Jennifer Maerz
esahq@esa.org
202-416-6181
Ecological Society of America
13-Oct-1998