Leafless tamarisk uses salt to obtain water from the air. This plant lives in extremely dry conditions on highly saline soils. Scientists suspect that this water-collecting mechanism could also help humans.
Tamarisk leafless (Tamarix aphylla) is a halophyte, i.e. a salt-loving plant. It grows in the dry, salt-rich soils of the coastal plains of the Middle East. Excess salt is secreted from special glands in the form of concentrated brine drops. On a hot day, the moisture contained in these droplets quickly dissipates, leaving white crystals shaking in the wind.
As a study recently published in the journal “Proceedings of the National Academy of Sciences of the United States of America” shows, they perform another function without which the plant might not survive.
While driving through the hot, humid deserts of the United Arab Emirates, Marieh Al-Handawi of New York University in Abu Dhabi noticed dew drops condensing on salt crystals. Many plants have mechanisms and leaf structures adapted to absorb water from the air, so the researcher suspected that salt crystals may also be among them.
Al-Handawi and her team recorded time-lapse videos of tamarisks in their natural habitat. The recordings showed that salt crystals formed during the day attract water at night. At a temperature of 35 degrees Celsius and a relative humidity of 80 percent, the branch covered with salt crystals collected 15 milligrams of water after two hours, while the washed branch collected only about one tenth of that amount. Moreover, the researchers observed dew forming on the crystals down to levels as low as 50 percent relative humidity.
– This result was decisive for us – said Al-Handawi. – He proved that in the process of collecting water, the main factor contributing to the accumulation of water are salts, not the plant surface – she added.
Analyzes have shown that the tamarisk salt “sprinkle” contains at least 10 different types of salt that have crystallized together. The crystals consist mainly of sodium chloride and gypsum, but traces of lithium sulfate have also been detected. This mineral absorbs water at much lower humidity than sodium chloride or gypsum. And although sodium chloride and gypsum provide the most water, the addition of lithium sulfate helps explain how tamarisk stores water even in low humidity.
Al-Handawi added that the water-obtaining mechanism used by tamarisk can also be useful to humans. Based on the collected data, it will be possible in the future to design preparations based on salt particles for collecting water from the air or seeding clouds at low humidity.
– This will allow us to modernize cloud seeding technology by making it more effective and more environmentally friendly – explained the researcher.
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