Biology

Plants can pollute the air we breathe in a surprising way

Plants can pollute the air we breathe in a surprising way
Some plants can produce their own natural pesticide but this self-defense tactic comes at a cost to our air quality
Some plants can produce their own natural pesticide but this self-defense tactic comes at a cost to our air quality
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Some plants can produce their own natural pesticide but this self-defense tactic comes at a cost to our air quality
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Some plants can produce their own natural pesticide but this self-defense tactic comes at a cost to our air quality

For years, we’ve admired plants for their ability to cleanse the air and help fight air pollution. However, our green ally might be contributing to air pollution in an unexpected way. While they may be just trying to fend off pests, this particular self-defense mechanism is also harming the environment.

Researchers have long known that plants secrete a natural chemical called isoprene, but exactly why and how plants did this was sort of an enigma. Though it was hypothesized to be a pest-resisting tactic, there was no empirical evidence proving this. Now, a study nearly four decades in the making has been published in Science Advances, showing how isoprene acts as a natural insecticide to protect plant leaves from insects.

Plants tend to produce more isoprene under extreme environmental conditions like heat stress. For this, plants release up to 2% of their stored carbon to synthesize isoprene. The allocation of substantial resources towards isoprene formation indicates its importance. To demonstrate the pivotal role of this compound, researchers at Michigan State University conducted lab experiments.

In the greenhouse trials, researchers bioengineered tobacco plants to emit isoprene and compared the observations with tobacco plants that didn’t produce isoprene. The team found that hungry tobacco hornworms (Manduca sexta) intensively attacked the non-emitting leaves, leaving the isoprene-emitting leaves alone.

The 10 days of observation showed that plants responded to the pest infestation within two hours. Results revealed that insects that fed on isoprene leaves showed stunted growth, likely stemming from digestive problems triggered by exposure to the chemical, unlike those that munched on the normal leaves.

But the isoprene doesn’t work the way you might think. The isoprene itself is not toxic to insects. Instead, it triggers a reaction inside plants that elevates the levels of Jasmonic acid. This makes the plant’s proteins tough for insects to digest.

“The defense was not the isoprene itself, but the consequence of what isoprene did to the plant,” says the lead author, Tom Sharkey.

However, this natural pest control mechanism comes with an environmental cost. Isoprene is a volatile organic compound (VOC) produced by plants like oak and poplar trees. It’s the second-highest emitted hydrocarbon on Earth, following methane emissions from human activities. Once in the environment, it interacts with sunlight and nitrogen oxides to form ground-level ozone, a harmful pollutant linked to respiratory problems and environmental concerns.

Now, the discovery of this isoprene mechanism has set researchers up with a tough choice: should we breed more isoprene-emitting plants to curb pest attacks and improve food security, or constrain commercial crops' ability to produce this chemical in the hopes of protecting the air we breathe?

“Should we add isoprene to crop plants so that they’re protected against insects and put up with their effect on the ozone? Or should we genetically engineer plants to turn off the isoprene synthase as much as we can to improve the atmosphere?” Sharkey asked, summing up the dilemma future bioengineers will face.

The study has been published in Science Advances

Source: Michigan State University

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8 comments
8 comments
YourAmazonOrder
Leave the plants alone. They know what they're doing. We do not.
Nobody
We always called that pollen.
Steve Pretty
There are so many forms of air pollution caused by us humans. Lets focus on pushing forward with our efforts to tackle those, mainly through stopping burning stuff!
McDesign
Reagan pointed out that trees pollute DECADES ago - and you folks just categorically dismissed it.
Nelson
In the sixties there were a lot of notable people warning us about to many humans, and that was when there were only three billion of us. With current technology an Earth of four billion could be an Eden, approaching nine billion things are getting bad, and an Earth of ten plus billion the Earth will just be one huge living Hell.
meofbillions
The questions asked at the end may be good ones, but we cannot know the answers until we know the amounts produced and the amount of greenhouse gases produced compared to other greenhouse gas sources. I agree with YourAmazonOrder, above. In the meantime, leave the plants alone and stop looking for excuses for mankind's destruction of its own environment.
Karmudjun
Oh once again the theoretical barnyard chemists come to protect us by hypothesizing methods of dealing with VOCs from plants under attack. Isoprene and the resultant Ozone are not great for human health, but the levels produced are not significant for human civilization either. Now the jasmonic acid produced that reduces pest growth is a big unknown in this process. The Isoprene uptake and resultant transcription of glucosinolates, polyamines, oxylipins, apiose, and phenylpropanoids listed in the source article may have an impact on mammals and on other plant life. Sure GHG are damaging, but what are the other compounds doing? I say continue studying, get a doctorate if you wish to stop the plants from joining in on climate change. After all, our GHG production has spiraled out of control, why are we worrying about this?
Ranscapture
@YourAmazonOrder This is correct