Smoke-induced germination is a well-established practice in commercial horticulture. Exposing the seeds of many plant varieties to controlled doses of smoke-either by directly immersing them in smoke or by submerging them in smoke-infused water-can invoke group germination, meaning that an entire crop or nursery batch will grow and flower in relative unison. Plants native to Mediterranean-type climatic regions, such as the southern California chaparral and large swaths of the Australian bush, most commonly respond to smoke-induced germination. These areas are known for their extended low-rainfall seasons that create dry, fire-prone underbrush, forcing the native flora to evolve fire-adapted reproductive countermeasures.
In some respects wildfire can be viewed as an opportunity for these plants to exploit catastrophe. The competitive environment is effectively "reset" by wildfire; access to available growing areas is wiped clean, and contact with groundwater and open exposure to visible sunlight is now up for grabs. Plants primed to germinate after a fire has died out to a smoking smolder are often best-suited to thrive in this reset post-wildfire landscape. Yet, for all the promise of this trait, smoke-induced germination also holds the potential for dire environmental consequences.
One of the primary chemical components of the smoke produced by burning wood is nitrogen dioxide, and initial insights suggested that nitrogen dioxide is one of the principal chemical triggers for smoke-induced seed germination. This discovery worried many environmentalists, however, because nitrogen dioxide is also a common component of smog. If smog forces plant seeds to germinate too soon, when an area has not been cleared by fire, the seeds are effectively wasted on an overly competitive growing environment. Could urban air pollution could be overstimulating and thereby disrupting the natural reproductive cycles of exposed plants? Scientists have a compelling incentive to answer these questions: If they can isolate and identify every component in wildfire smoke that induces seed germination, they could use that knowledge hopefully to counteract the effects of smog.
After 11 years of research, scientists at the University of Western Australia have presented convincing evidence that they have found the primary trigger for many species of smoke-sensitive plants: butenolide, a heterocyclic compound produced by burning plants and wood. What makes this discovery so intriguing is that butenolide exposure induces germination even in plants that are not native to Mediterranean climates, including lettuce, parsley, and the popular herbal remedy Echinacea. This suggests that butenolide-based fertilizers might be used successfully on a staggeringly wide array of commercial plants-even those not commonly preyed upon by wildfires.
This discovery, in turn, could also help control the effects of smog on nitrogen dioxide-sensitive plants. With judicious use of butenolide fertilizer in smog-prone areas, botanists could theoretically encourage mass seed germination during key time periods, compensating for reproductive disruption caused by smog. Thanks to savvy Australian biochemistry, agriculture may soon reap the benefits of wildfire-adapted evolution without ever needing to set even a single plant aflame.
