Witchweeds suck the juices from their host plant while other plants sprout after bushfires and reproduce. Now a coven of researchers at The University of Western Australia has unlocked the secret of the dark arts that could help to bring the dormant back to life.
Insidious witchweeds live off a range of weedy grasses and cereal crops. Its seeds lie in wait in the soil until an unsuspecting plant starts to grow. Chemical signals called strigolactones (‘witch' chemicals) produced by the host inadvertently kick-start the seeds into life which then attack the host. The consequences are devastating. In Africa and Asia, witchweeds cause serious losses to food production.
Meanwhile a different group of seeds lies in wait 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. These signals say that there is a great opportunity to exploit the new sunny and nutritious environment above for reproduction. Karrikins play a vital role in landscape regeneration after fire.
The new research led by Dr Mark Waters and published in the prestigious journal Developmenthas discovered two related genes that distinguish the two signals.
Strigolactones and karrikins comprise a close-knit family of related chemical agents working undercover to trigger the same molecular machinery to stimulate seed germination. However, karrikins do not stimulate witchweeds and strigolactones do not stimulate smoke-responsive species.
"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," Dr Waters said.
"It appears that plants have adapted a common mechanism for two very different cases of opportunism - parasitism and fire."
The research will provide the know-how to develop new strategies to persuade seeds to germinate, whether for forest rehabilitation, conservation, crop production or eradication of weeds.