Title: Surprising Twist: Plants May Contribute to Air Pollution While Fighting Pests
The Hidden Side of Nature’s Air Purifiers
For years, plants have been celebrated for their ability to purify the air and combat pollution. However, new research reveals that these green allies might also play an unexpected role in worsening air quality—despite their best intentions. While their defense mechanisms protect them from pests, these same processes can negatively impact the atmosphere.
Isoprene: The Unsolved Mystery of Plants
Scientists have long known that plants emit a natural compound called isoprene, but its purpose remained unclear. Hypotheses suggested it played a role in pest deterrence, but concrete evidence was scarce. Now, a groundbreaking study published in Science Advances confirms that isoprene acts as a natural insecticide, shielding leaves from harmful insects.
Under stress—such as heat—plants produce even more isoprene, dedicating up to 2% of their stored carbon to its production. Researchers at Michigan State University conducted greenhouse experiments, modifying tobacco plants to emit isoprene and comparing them to non-emitting counterparts. The results were striking: tobacco hornworm larvae (Manduca sexta) heavily targeted leaves without isoprene while largely ignoring those that contained it.
A Double-Edged Defense Mechanism
Within 10 days, plants responded to pest attacks in just 2 hours. Insects feeding on isoprene-rich leaves showed stunted growth, likely due to digestive issues caused by the compound. Interestingly, isoprene itself isn’t directly toxic—instead, it boosts levels of jasmonic acid in plants, making their proteins harder for pests to digest.
Tom Sharkey, the study’s lead author, explains: “Isoprene didn’t directly defend the plant—it triggered changes inside the plant that provided protection.”
The Environmental Cost of Plant Protection
However, this natural defense comes at a cost. Isoprene is a volatile organic compound (VOC), emitted by trees like oaks and poplars. It’s the second-most abundant hydrocarbon in Earth’s atmosphere after methane. When exposed to sunlight and nitrogen oxides, isoprene contributes to ground-level ozone—a harmful pollutant linked to respiratory issues and environmental damage.
A Dilemma for Scientists
Now, researchers face a tough question: Should we enhance plants’ isoprene production to bolster pest resistance, or suppress it to improve air quality? Sharkey poses the challenge: “Do we add isoprene to crops, or disable the enzyme that produces it?”
The answer remains unclear, but one thing is certain—nature’s solutions are rarely simple.
