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A chemical ‘smoke signal' enables seeds and seedlings to better ‘see' the light and to adapt their growth to the new conditions, according to researchers at The University of Western Australia.

A paper documenting the results of years of research by scientists in UWA's Faculty of Life and Physical Sciences in collaboration with Kings Park and Botanic Garden is published today in the prestigious Proceedings of the National Academy of Sciences in the USA.

The ‘smoke signal', named ‘karrikins', comprises the substances in bushfire smoke that stimulate germination of dormant seeds, and make some seeds and seedlings more responsive to light.  The name derives from the Noongar word for smoke - karrik.  In keeping with convention in naming families of biologically active molecules, the -in suffix was added to form ‘karrikin'.

After a fire, the light quality is altered because it is no longer filtered by a canopy of leaves, and the soil is blackened.  Karrikins make some seeds much more sensitive to this new light regime, so that they germinate more readily and produce sturdier seedlings.  This discovery has major implications for understanding bush regeneration after fires and for using karrikins to help germinate valuable seeds, or to restore the vegetation at mine sites.

UWA plant biologist Dr David Nelson who discovered the response to light said: "We found that seedlings exposed to karrikins become more responsive to light.  They shorten their stem and expand their first leaves to produce a stockier seedling that is adapted to the exposed conditions left by fire."

"Living organisms have learnt to use a range of chemicals to provide them with information about the surrounding environment," said UWA chemist, Professor Emilio Ghisalberti.  "Karrikins provide plants with more information than we ever imagined."

"We've found that plants are highly adapted to the post-fire environment so that they maximise the chances of seedling establishment," said Kings Park Director Professor Kingsley Dixon.  "The name ‘karrikins' recognises that the scientific discovery was made on Noongar land, and reflects the importance of fire and smoke to plant ecology and to Aboriginal culture."

Photograph courtesy of Ben Miller, Kings Park and Botanic Garden.

Media references

Winthrop Professor Steven Smith (+61 8)  6488 4403
(UWA ARC Centre of Excellence in Plant Energy Biology and School of Biomedical, Biomolecular and Chemical Sciences)
Sally-Ann Jones (UWA Public Affairs)  (+61 8)  6488 7975  /  (+61 4) 20 790 098