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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)
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