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Orchids: Aerial roots with Velamen radicum
Orchids living as epiphytes in humid tropical rain forests often have aerial
roots that hang down like long beards. These roots are relatively thick and
smooth. Except for a green tip, they are silvery-white in color. This color
comes from a layer of dead, air-filled cells, known as Velamen radicum. When
it rains, these cells soak with water like blotting paper and become transparent,
revealing the green core of the root beneath. Roots containing chlorophyll are
an anomaly in most of the plant kingdom, but they’re nothing special among epiphytes.
In the bromeliad and aroid house you can see species of Anthurium that
produce roots very similar to those of epiphytic orchids. Though these plants
are not related, they have developed the same mechanism to quickly absorb water.
As you can see, similar survival strategies can evolve independently among very
different members of the plant kingdom.
Audio file download
Orchids: Aerial roots with Velamen radicum (MP3, 425 KB)
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