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Sneezing Plants

The surface of a wheat leaf is superhydrophobic, which means that it's really good at repelling water. Instead of sticking to the leaf, water beads up into tiny droplets. (Shree Krishna Dhital, Wikimedia Commons)

Agriculturalists are worried about a fungus-caused plant disease called leaf rust that afflicts wheat, barley and rye. It's produced plant epidemics in North and South America, and had devastating consequences in India.

Scientists are still trying to understand how it spreads. According to a study published in 2019 by a team of American and Indian scientists, the plants spread the disease by a process that's a bit like sneezing in people.

Of course, plants don't really sneeze, but it's a useful metaphor to understand what's actually going on. The surface of a wheat leaf is superhydrophobic, which means that it's really good at repelling water. Instead of sticking to the leaf, water beads up into tiny droplets, just about like the ones that get expelled from your mouth in a sneeze.

The tiny droplets pick up fungus spores from an infected plant. If two tiny droplets come together, their surface tension-the stickiness of water-acts like a spring to fling them off the plant. It's like the droplets flung out from your mouth in a sneeze.

Once these tiny droplets are flung off from the plant, they can be carried by air currents to a neighboring plant and spread the fungus spores.

The researchers hope they can stop the spread of the disease by coating the leaves with a chemical that will make them less superhydrophobic.

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