Leaves Channel Dew As Water Source

Biological Strategy

Welwitschia

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Capture, Absorb, or Filter Liquids

The most common liquid used by living systems is water, which they require to survive. But there are many other liquids that provide nourishment, play a role in defense mechanisms, or serve other purposes. Water varies in its availability; it is sometimes plentiful and sometimes very scarce or only available as fog or mist. To minimize the energy required to capture, absorb, or filter liquids, living systems have strategies that take advantage of the unique properties of the given liquid. For example, water moves from a gaseous to liquid state when it encounters a surface colder than the air. Plants in forests that experience fog and clouds more than rain have strategies that condense liquid water from moist air.

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Store Liquids

Many living systems must store liquids, such as water or nectar, so that it is available over long periods of time, including when moisture levels are low. Because of their properties, liquids tend to disperse unless they are confined in some way. Each liquid has its own unique properties. For example, water is polar, exhibiting a strong negative charge on one side of the molecule and a strong positive charge on the other. Living systems have strategies to confine fluids by taking advantage of these properties. A good example of taking advantage of water’s polarity is using materials that repel water. In doing so, a living system can keep water on one side of a barrier, such as a membrane.

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Flowering Plants

Clade Angiosperms (“receptacle seed”): Dandelions, oaks, grasses, cacti, apples

With 416 families containing some 300,000 known species, angiosperms are the most diverse group of plants, and they can be found around the globe in a wide variety of habitats. They are characterized by seeds that grow enclosed in ovaries, which are enclosed in flowers. The floral organs then develop into fruits of myriad kinds and dimensions, from simple seed casings on maples to elaborate fleshy growths like papayas. The oldest flower known from fossils, Montsechia vidalii, appeared during the Jurassic Period 130 million years ago. They are the primary food source for herbivorous animals, which in turn makes them the indirect food source for carnivores as well.

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The long leaves of desert Welwitschia capture water by collecting dew and channeling it into the ground where a large tap root can absorb it.

Young Leaves Channel Water

Fish-pole bamboo

Young leaves of bamboo channel excess water using a combination of hydrophobic and hydrophilic surfaces.

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“Further inland, one of the oddest of all plants manages to survive largely on dew. Welwitschia is related to the conifers and the cycads and consists of just two long strap-like leaves that sprout from a central swollen trunk only a few inches high. The leaves grow continuously from their base and become very long indeed. They would doubtless be even longer were it not for the desert winds which, blowing them back and forth, frays the ends into tatters. Even as it is, these leaves may be twenty yards long and lie curled in untidy heaps around the stunted trunk. They collect droplets of dew and channel them down runnels into the ground where the water is absorbed and stored in an immense conical tap root.” (Attenborough 1995:267)

Last Updated March 14, 2018

References

Book

The Private Life of Plants

21/08/1995 | David Attenborough

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