Got sick plants? Give them an aspirin

Alaska Science Forum
December 26, 1990
Not Feeling Green Enough? Take Two Aspirin...
Article #1010
by Carla Helfferich

This article is provided as a public service by the Geophysical Institute, University of Alaska Fairbanks, in cooperation with the UAF research community. Carla Helfferich is a science writer at the Institute.
--------------------------------------------------------------------------------

Once in a while my voracious reading of general scientific literature turns up something that strikes me right on the funny bone. The scientists didn't mean it to be funny; maybe other nonscientists won't find it funny. See how this strikes you:

Sick plants take aspirin. They don't even call the plant doctor first.

OK, OK, I'm being irreverent here, and am oversimplifying to the point of inaccuracy. The story really isn't goofy.

When a plant is attacked by pathogens---viruses, bactena, fungi, or some such noxious microorganism--it often resists the invaders by fencing them off somehow. Disease starts up, but the plant rcstricts the damage to a small area near the site of infection. That's an obviously useful ability, and one worth study. One group of researchers from New Jersey pursued that study into the genetic makeup of the tobacco plant.

Tobacco was the chosen subject because of two convenient features. It is attacked by a pervasive enemy, tobacco mosaic virus (TMV); and one strain of tobacco is naturally resistant to TMV. The virus attacks the resistant strain, but doesn't overcome the plants. Furthermore, researchers knew that resistant tobacco fights back with a suite of proteins that nonresistant tobacco can't produce. Many plants can produce these PR (short for pathogen-resistant) proteins, but the exact chemical trigger that sets their biochemical factories to cranking out these defenses hasn't been clear. What tells the genes that it's time for PR production?

Here I quote directly from the Science magazine reporting the research: "Application of exogenous salicylic acid or its derivative acetyl salicylic acid is particularly effective in inducing PR genes in many plants, including tobacco." Translated into basic English, that means if you give a sick tobacco plant with the right genetic makeup some aspirin precursor or even plain aspirin, it tells the genes to get busy with the defenses.

The report went on to note that one tobacco strain makes its own salicylic acid if injected with tobacco mosaic virus, with increased levels showing up about a day after infection and peaking to twenty times initial concentration after two days. In effect, the plant increases its dosage. Only the virus could trigger the salicylic acid-protein production reaction; when the researchers tried abrading, slashing, or freezing parts of the plants, they did not give them- selves aspirin. (The life of a laboratory tobacco plant is a high-risk existence.)

The next report in that issue of Science told of similar work on cucumbers. Most of the researchers on this team were Swiss, but they were as willing to give plants a tough time as the New Jersey group was. They challenged cucumbers with a fungus and a virus, and both turned on the aspirin-making response. That in turn apparently triggered the PR-producing genes, and the plants fended off the infections. They also developed what the scientists called "systemic acquired resistance"---that is, they had more resistance to new infections by the same organisms introduced at other sites on the plants.

See? It really is a nice story, with nothing funny about it. It's just that I got this image of a sickly philodendron showing plant-flu symptoms: I'm going to paint that sucker with an aspirin solution and send it to bed. If it calls me in the morning, it'll get chicken soup next.