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Smoke-stimulated germination (2): Shedding light through the smoke

November 1st, 2016 Leave a comment Go to comments

There are plants in which fire can breaks seed dormancy and stimulate germination. In some species, it is the heat of the fire that breaks seed dormancy and triggers germination (heat-stimulated germination, [1, 2]). In others, germination is stimulated by chemicals produced during the combustion of the organic matter (e.g., chemicals found in the smoke and charred wood) [1, 3]; we call this process, smoke-stimulated germination [5]. That is, in fire-prone ecosystems many plants have evolved seeds with sensitivity to heat and/or to chemicals produced by fire [1, 2, 3].

There are many species from a wide phylogenetic range with smoke-stimulated germination [5]; they appear in different regions worldwide and are stimulated by different combustion-related products, both organic and inorganic [4, 5]. All this suggest that smoke-stimulated germination is a trait that has appeared multiple times during the evolution, and thus is another example of convergent evolution [5].

In the Mediterranean Basin we currently know about 67 species (from 19 families) showing a significant increase in germination in response to smoke [6]. Families with many smoke-stimulated species in this region are Lamiaceae, Ericaceae and Asteraceae. However, there is still a lot of research to be done on smoke-stimulated germination in Mediterranean Basin flora, as many species have not yet been tested; in fact, very few annuals has been tested [6] despite there is evidence from field studies (3) and from other Mediterranean regions suggesting that smoke-stimulated germination is important in annuals.

But remember, plants are not the only organisms that have evolved in response to chemicals present in the smoke, humans too! [7].

smoke-germinationFigure: Germination (proportion of seeds) in control conditions (light yellow) and after a smoke treatment (blue) for four Mediterranean species in which germination is strongly dependent on smoke: Coris monspeliensis (Primulaceae), Erica umbellata (Ericaceae), Onopordum caricum (Asteraceae) and Stachys cretica (Lamiaceae) See [6].

 

References
[1] Moreira B., Tormo J., Estrelles E., Pausas J.G. 2010. Disentangling the role of heat and smoke as germination cues in Mediterranean Basin flora. Ann. Bot. 105: 627-635. [pdf | doi | blog]

[2] Moreira B and Pausas JG. 2012. Tanned or Burned: the role of fire in shaping physical seed dormancy. PLoS ONE 7:e51523. [doi | plos | pdf]

[3] Tormo, J., B. Moreira, and J. G. Pausas. 2014. Field evidence of smoke-stimulated seedling emergence and establishment in Mediterranean Basin flora. J. Veget. Sci. 25: 771-777. [doi | wiley | pdf | blog ]

[4] Smoke-stimulated germination, jgpausas.blogs.uv.es/2011/12/02/

[5] Keeley J.E. & Pausas J.G. 2018. Evolution of ‘smoke’ induced seed germination in pyroendemic plants. South African J. Bot. 115: 251-255 [doi | pdf] <- New

[6] Moreira B. & Pausas J.G. 2018. Shedding light through the smoke on the germination of Mediterranean Basin flora. South African J. Bot. 115: 244-250 [doi | pdf] <- New

[7] Smoke and human evolution, jgpausas.blogs.uv.es/2016/08/31/

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