Water capturing salt crystals
Plants and animals that live in dry or salty environments often have ingenious ways for catching water. Like for example the athel tamarisk (Tamarix aphylla), a scrub that is growing in salty marshes. Now researchers report in PNAS how this scrub is cleverly using its salty environment to capture water.
The athel tamarisk grows in salty coastal mudflats of the United Arab Emirates. Like scales of a fish are the small leaves covering the branches of this bush. They contain salt glands that excrete droplets of excess salt. The water evaporates, leaving salt crystals, covering the plant behind.
At dusk and during the night, the researchers noticed, these salt crystals turn into droplets. Catching the moister out of the air. During the day this captured water evaporates again, leaving salt crystals behind. The researchers decided decipher this phenomenon.
Plants keeps us amazed by their inventiveness
First they analysed the contents of the salt crystals. Discovering that in addition to sodium chloride these crystals also contained other salts like calcium sulphate and lithium sulphate. Subsequently they studied why these other salts were there. Finding that these additional salts help the droplets and crystals to stay attached to the leaf. Moreover, the researchers noticed, that plants with salt crystals captured more water than plants without salt crystals.
But the most important effect of the other salts in the salt crystals was that they enabled the capture of water at a lower humidity. Salt crystals containing only sodium chloride start capturing water at a relative humidity of 70%. In contrast the salt crystals of the athel scrub already start capturing water at a relative humidity of 50%. Capturing in a night more that their weight in water. But before the scrub can consume this water it first needs to evaporate. Only then can the leaves via their stomata drink the water.
Plants keeps us amazed by their inventiveness. It not only enables the athel scrub to hold out in arid circumstances. It also gives inspiration for new ways of capturing water out of thin air.
Literature
Marieh B. Al-Handawi, Patrick Commins, Robert E. Dinnebier, Mahmoud Abdellatief, Liang Li, and Panče Naumov (2023) Harvesting of aerial humidity with natural hygroscopic salt excretions. Proc Natl Acad Sci USA 7;120(45):e2313134120. https://doi.org/10.1073/pnas.2313134120
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