AsianScientist (Mar. 22, 2012) – Studies done on parasitic witchweeds as well as plants that thrive in the aftermath of bushfires have enabled researchers at the University of Western Australia to unlock two secrets of seed germination – linked to parasitism and fire.
Witchweeds are parasites that live off a range of weedy grasses and cereal crops. Its seeds lie dormant in the soil until an unsuspecting host plant starts to grow, producing host chemical signals called strigolactones in the process. The strigolactones kick-start the seeds into life which then attack the host. In Africa and Asia, witchweeds cause serious losses to food production.
In the second case, a different group of seeds lies dormant in the soil until a bushfire passes overhead. The following rains send chemical signals called karrikins (‘smoke’ substances) into the soil to tell these seeds to germinate and exploit the sunny, nutritious environment above for reproduction. Karrikins thus play a vital role in landscape regeneration after fire.
Strigolactones and karrikins comprise a family of related chemical agents that are able to trigger the same molecular machinery to stimulate seed germination. However, karrikins do not stimulate witchweeds and strigolactones do not stimulate smoke-responsive species.
The discovery of the two related genes that distinguish the two signals was led by Dr. Mark Waters of the ARC Center of Excellence for Plant Energy Biology, and published in the journal Development.
“It’s like having two keys to open two different doors of the same control box. Each key has to match the correct lock but both get access to the controls,” said Waters.
“It appears that plants have adapted a common mechanism for two very different cases of opportunism – parasitism and fire.”
This research may provide scientists the know-how to develop new strategies to encourage seeds to germinate, whether for forest rehabilitation, conservation, crop production, or eradication of weeds.
Source: University of Western Australia.
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