109 學年度學測英文 第 21 題

When a person sneezes, the droplets can spread diseases. Now research shows that plants have a somewhat 21 problem. Plant diseases can also spread through tiny water drops that jump off leaves—a plant’s version of a sneeze.

Scientists already knew earlier that wind and splashes of rainwater can move bacteria and other germs from leaf to leaf. 22 other possible transmission routes, researchers at Virginia Tech observed water drops on the leaves of wheat plants that were infected with leaf rust. They found that the sick plants could “sneeze” and 23 tiny water drops filled with leaf rust germs, spreading the disease to neighboring plants.

The researchers noticed that small drops of water on the wheat leaves would move to combine and form a larger drop. As they were moving, the energy of the droplets in motion would be released. This energy allowed the water 24 into the air, which looked just like sneezing!

However, not all plants can sneeze. The ability is 25 to those with leaves that are hydrophobic, or repel water—a special feature that forces the liquid to move away when the leaf is exposed to it.