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Pistia, Azolla, Salvinia: Buoyant hair

Most aquatic plants can float thanks to thickened, air-filled organs on the surface of the water. On some kinds, however, you may notice the matte, green surface of their leaves. Look closely at the upper surfaces of these free-floating plants: you’ll see that the leaves are covered with a thick, satiny coat of hair.

If you push one of these plants below the surface, they’ll have a silvery gleam thanks to the air trapped among the hairs. As soon as you release it, it will pop to the surface and resume its original color. The hair repels water so well that every last drop will simply roll off.

These plants get their buoyancy from a combination of a water-repellent surface with air-trapping hairs. This strategy is particularly evident in the water lettuce Pistia, a free-floating member of the arum family, but aquatic ferns of the genera Azolla and Salvinia use the same principle.

Audio file download
Pistia, Azolla, Salvinia: Buoyant hair (MP3, 382 KB)

Audio production and copyright: Soundgarden Audioguidance GmbH
Text: Günter Gerlach, Botanischer Garten München-Nymphenburg

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