Achoo Better Watch Out: Sneezing Plants Spread Diseases

Featured Article: Saurabh Nath, S. Farzad Ahmadi, Hope A. Gruszewski, Stuti Budhiraja, Caitlin E. Bisbano, Sunghwan Jung, David G. Schmale and Jonathan B. Boreyko. ‘Sneezing’ plants: pathogen transport via jumping-droplet condensation. https://doi.org/10.1098/rsif.2019.0243

 

Fall is swiftly approaching and with the change in seasons comes pumpkin-spiced everything, colorful falling leaves and an increase in airborne pathogens! That’s right, everyone, it’s cold and flu season.

Airborne pathogens, such as the common cold, are frequently spread through coughing and sneezing. Your best bets for avoiding illness this holiday season: get a flu shot; wash your hands regularly; and above all else, avoid the dreaded cough clouds and sneeze sprays like the plague.

A recent study by Virginia Tech suggests that sneezing can also spell disaster for our chlorophyll filled friends.  Don’t get it twisted, an animal sneezing onto a plant will not make it sick! The plant must be doing the sneezing.

Virginia Tech’s Engineering and Agriculture Departments joined forces to conduct the $500,000 study on “sneezing” wheat. Assistant Professor of Mechanical Engineering Jonathan Boreyko and Professor of Plant Physiology, Pathology and Weed Science David Schamle led the three-year investigation. Their findings: plants can “sneeze.”

Have no fear, the fichus in your living room will not be spraying you with snot. “Sneezing” is a trait reserved for specialized superhydrophobic plants. Hydrophobic plants are extremely water resistant.

Figure 1: Wheat leaf rust https://commons.wikimedia.org/wiki/File:Wheat_leaf_rust_on_wheat.jpg

The study focused on Puccinia triticina commonly known as wheat leaf rust. As its name suggests, this rust-colored fungus primarily infects wheat, rye and barley. If unmanaged the fungus causes significant decrease in crop yield. Losses can be as high as 20%. Fungal spores of wheat leaf rust are spread through the air via strong gusts of wind or the occasional “sneeze.” When wheat sneezes, spore-filled water droplets take to the air and land on neighboring plants.

 Plants can Sneeze?

Yes, plants can sneeze. Well… sorta. When a human sneezes, they expel pathogen-laden water droplets and mucus from their nose and mouth as a response to irritation in the nasal cavity. Plant sneezes are a little different. On hydrophobic surfaces, spore-filled water droplets merge, and the surface tension is converted into kinetic energy creating a mist like spray of disease.

Wheat is extremely water resistant, meaning it is particularly good at sneezing! The pathogen laden spray can soar up to 5 mm in the air. This might not sound like a tremendous height, and that’s because it truly isn’t. For perspective 5 mm is equivalent to the width of a pencil eraser. All things considered, the infected water droplets have a pretty weak vertical leap; however, this tiny flight is enough for the wind to sweep the spores off to an unsuspected victim.

Figure 2: Water droplets containing wheat leaf rust spores launch into the air when condensate gathers converting surface tension into kinetic energy. https://royalsocietypublishing.org/doi/10.1098/rsif.2019.0243

An airborne, spore-filled water molecule requires a measly 0.1 meter per hour gust of wind to send it soaring. A droplet on a leaf requires a gust of wind 100 times stronger to lift it into the air. This proves that a plant “sneeze” makes it significantly easier to spread disease.

Importance

Like humans, plants frequently become infected by airborne pathogens. The wind carries spores from infected plants to neighboring greenery further spreading illness. This study proves fluid dynamics give hydrophobic plants a unique way to spread harmful pathogens.

By understanding this, scientists can begin research on ways to combat the problem. The original publishers of the study have already begun such research. Moving forward they will test if the water-repelling properties of the wheat plant can be altered. If they are successful in reducing the species hydrophobia, the newly discovered plant “sneezing” phenomenon could quickly become a thing of the past, resulting in reduced agricultural losses.

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Laine Farber

Laine Farber

I am recent graduate of Louisiana State University. With a background in journalism and a love of science, I have a passion for making science stories easy to understand and enjoyable to read. I am currently working in the education department of an environmental non-profit based out of New Orleans and stepping into the highly competitive freelance journalism game. When I am not rewriting a textbook or chasing down a story, you can find me walking along the lakefront, painting or feeding dry corn to ducks. For more information follow me on Twitter at @lfarber14 or Instagram @lainefarber.

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