Rising from the ashes

Burnt old plants generate a chemical message for the next generation, telling dormant seeds it’s time to sprout. Scientists explain that controlling a forest fire can actually be harmful in the long run because the soil then loses the important minerals and chemicals needed to nudge the new generation into wakefulness, writes Atula Gupta.

There is something that is whispered in the ears of a dormant seed. An urgent message prompted by a forest fire to germinate, propagate and spread out.
Scientists have finally found the answer to why seeds lying dormant for years and years on the forest floor suddenly wake from their slumber and literally rise from the ashes after a forest fire. It is thanks to a chemical communication between one that is burning away and the one that is eager to embrace the world with its new shoots and leaves.

Forest fires are in most cases a natural phenomenon, a cleansing ritual where the old dies and the new sprouts forth. But, for centuries, it has been a mystery how seeds seemingly dead, sprawled on the forest floor, can energetically take the place of their charred brethren once the fire has subsided and new green cover is urgently required. Scientists at the Salk Institute and the University of California, San Diego, now say that they have found the molecular trigger that pushes this rapid regeneration.

The researchers explain what happens is nothing less than a magical passing of information. Burnt old plants generate a chemical message for the next generation, telling dormant seeds it’s time to sprout! They also add that controlling a forest fire can actually be harmful in the long run as the soil then lacks the important minerals and chemicals needed to nudge the new generation into wakefulness.

Explains James J La Clair, one of the researchers, “When Yellowstone National Park was allowed to burn in 1988, many people felt that it would never be restored to its former beauty. But by the following spring, when the rains arrived, there was a burst of flowering plants amid the nutrient-rich ash and charred ground.”

Life-triggering chemical

Previous studies in the same area have noted that special chemicals known as karrikins are created as trees and shrubs burn during a forest fire. This time, the scientists found a plant protein called KAI2, which binds to the chemical karrikin on the dormant seed.  

The dormant seeds might be living with the protein for years, but it is only when it is bound to karrikin, that the seeds perceive its presence.

Role of karrikin

Binding changes the shape of the protein and this changed shape signal other proteins to begin working too. “These other protein players,” plant geneticist Zuyu Zheng says, “together with karrikin and KAI2, generate the signal causing seed germination at the right place and time after a wildfire.”

While the new findings were made in arabidopsis, a model organism that many plant researchers study, the scientists say the same karrikin-KAI2 regeneration strategy is undoubtedly found in many plant species.

“In plants, one member of this family of enzymes has been recruited somehow through natural selection to bind to this molecule in smoke and ash and generate this signal,” they say. “KAI2 likely evolved when plant ecosystems started to flourish on the terrestrial earth and fire became a very important part of ecosystems to free up nutrients locked up in dying and dead plants.”

Understanding the chemistry behind the bountiful growth and forest regeneration post a wild fire is a significant discovery. Not only does it give a more positive view of the devastation that seems to eradicate an entire living, breathing, thriving ecosystem, it also might give scientists the choice to build their own forests.

Afforestation in the future might not be about planting tree saplings, but simply triggering the natural molecular process of growth in seeds by providing them the right signals. Rapidly vanishing natural habitats can be re-generated by prompting grasslands, tropical forests, rainforests to grow again where human negligence and interference has created mass forest vacuums. It is still a niche study area, but the possibilities are immense if the science is used in the right direction.

Situation in India

In India, statistical data on fire loss are weak but it is estimated that the proportion of forest areas prone to forest fires annually ranges from 33 per cent in some states to over 90 per cent in other. Sadly, most of forest fires in India are man-made. Burning of forest understorey at the peak of the dry season helps to stimulate grass growth before the monsoon rains break and this is a major grazing source for cattle. Collecting non-wood forest products in the dry deciduous is often associated with burning — the fire removes the leaf litter layer, and freshly fallen fruits become visible and easier to collect.

Although the present research highlights that rapid re-generation is a certainty, deliberate fires can, time and again, lead to other problems such as soil erosion and loss of wildlife.

By using the same chemistry to trigger seed sprouting, perhaps the need to burn an entire forest down for human and cattle needs can be avoided.

As scientists try to unravel little by little the infinite mystical ways Mother Nature ensures sustenance of life, it becomes clearer that humans have a long way to go before they achieve nature’s perfection — where even in death, it is assured that millions of new lives spring forth precisely when they are needed the most.