Appearance of the shrub, branches, and surfaces of T. aphylla. (A) A photograph of T. aphylla located across the coastal sabkha of the United Arab Emirates. (B) A close-up view of the branches. (C) A branch recorded in the late morning (11 a.m.) was encrusted with salt crystals. (D) A branch recorded in the early morning (8 a.m.) showed condensed water droplets. (E and F) Scanning electron microscopic images of the surfaces of leaves with salt crystals (E) and a zoomed image of a single salt gland (F). The length of the scale bars in panels B, C, D, E, and F are 5 mm, 3 mm, 3 mm, 1 mm, and 50 µm, respectively.
Yesterday it was fish 'designed' to live in a desert that demonstrated how biological 'design' is a bottom-up process where, in this case, a fish, is faced with increasing desertification of its environment and only those fit for living in the environment survive to breed, so, over time, and with whatever increased complexity evolves, we have fish 'designed for living in a desert.
An intelligent designer, on the other hand, starting with a desert, would be insane to imagine that what was needed was a fish to live in it, and then set about designing all the complexity and elaborate workarounds for the problems it has needlessly created for itself.
And today, we have another example, in the form of a plant that also lives in a desert, so needs an alternative source of water.
What intelligent designer not in need of responsible adult supervision, would look at a desert and think, "I know what that needs - plants!", then try to solve the problem of, being a plant, it needs water which is singularly lacking in a desert, so it designs a ludicrously complicated way to get water, instead of simply designing the plant to live where there is enough water for it, using the method it has already used successfully in just about every other plant.
The method it invents is first to put the plant in conditions where there is a lot of salt in the soil which it needs to excrete through special glands on the leaves. The salt, being hygroscopic then attracts and captures the water molecules in the air - more complexity to do what could have been done much more simply using tried and tested roots and putting the plant in an environment where there is water in the soil.
Evolution, On the other hand, is a bottom-up design process that responds to the here and now with whatever it has to hand and has no choice but to accept whatever is better than the previous because those with the better adaptation leave more descendants, so the trait which gives them an advantage comes to dominate in the population,. So, this process could take a plant that has already adapted to live in salty soil by excreting the excess salt through glands on its leaves and exploit the hydroscopic nature of that salt to either move into a desert with costal fogs and moist air or adapt to increasing desertification. Evolving to cope with excess salt in the soil, was the fortuitous key to opening up the new niche and being able to move into the Arabian Coastal Desert.
Evolution doesn't have the mechanism that we would expect a real intelligent designer to have - the ability to think, "This is all getting a bit silly and over-complicated, so why don't I scrap this design and just put the plant where these things aren't problems?"
Complexity is a typical result of the utilitarian bottom-up natural design process that doesn't have a plan; the typical result of good intelligent design is minimal complexity and maximal simplicity - things we rarely find evidence of in nature.
Having said that, though, the mechanism that evolution has produced is fascinating, as is so much else of evolved nature. It was discovered by a team of scientists, led by Post-Doctoral Associate Marieh B. Al-Handawi and Professor of Chemistry Panče Naumov from New York University (NYU) Abu Dhabi’s Smart Materials Lab and NYU Abu Dhabi Institute’s Center for Smart Engineering Materials (CSEM). The team's findings are published, open access in PNAS. The NYU Abu Dhabi news release explains the research and its importance for water conservation:
[The research team] has revealed the mechanism a desert plant native to the United Arab Emirates uses to capture moisture from the desert air in order to survive. The identification of this unique mechanism, in which the plant excretes salts to extract and condense water onto the surface of its leaves, has the potential to inspire the development of new technologies, and improve existing ones such as cloud seeding, to harness atmospheric water resources.More technical detail is given in the team's paper in PNAS:
Tamarix aphylla, or athel tamarisk, is a halophytic desert shrub, meaning it can survive in hypersaline conditions. Over time, the plant has evolved to take full advantage of the prevalent humidity and fog occurrences in the UAE. Many plants and animals that inhabit arid regions have developed water-harvesting mechanisms and morphophysiological traits which have given them the ability to utilize abundant, untapped sources of water such as fog and dew. The fundamental principles governing this natural water collection serve as an inspiration for emerging water-collection technologies, which are developed to maximize the efficiency of the existing methods for harvesting aerial humidity.
In the paper titled Harvesting of Aerial Humidity with Natural Hygroscopic Salt Excretions published in the journal Proceedings of the National Academy of Sciences of the United States of America, the researchers present their exploration of the physicochemical aspects of salt release and water collection mechanisms by Tamarix aphylla that has allowed it to thrive in hypersaline sands.
The plant absorbs saline water from the soil through its roots, filters out the salt, and expels the concentrated salt solution onto the outer surface of its leaves. The researchers found that as the salt solution undergoes evaporation, it transforms into a hygroscopic crystalline mixture composed of at least ten different minerals. It was discovered that some of these salt crystals have the ability to attract moisture from the air even when the humidity levels are reasonably low (~55% relative humidity). This moisture condenses onto the surface of the plant's leaves and is then absorbed.
The global scarcity of freshwater has stimulated research into alternative water-harvesting technologies to supplement the existing conventional resources in water-stressed locations. Within a broader context, this natural mechanism developed by the research team for harvesting humidity using environmentally benign salts as moisture adsorbents could provide a bioinspired approach that complements the currently available water collection or cloud-seeding technologies.Our findings not only reveal a unique, natural complex mechanism for water utilization, they also open prospects for designing environmentally benign formulations based on a biogenic salt mixture that could be used for efficient harvesting of aerial water or cloud seeding at low humidity. This holds the promise of revolutionizing cloud seeding practices by rendering them more effective and environmentally friendly, while also aligning with our responsibility to use the planet's scarce water resources wisely.
Dr Marieh B. Al-Handawi, lead author
Post-Doctoral Associate
Smart Materials Lab,
New York University Abu Dhabi, Abu Dhabi, United Arab Emirates.
SignificanceIt is the many examples such as this where no sane intelligent designer would attempt to design what the bottom-up process of evolution produces, that give the lie to the intelligent design hoax that creationists are using to fool scientifically illiterate fools into sending them money, joining their cult, and - their ultimate goal - giving them political power to pursue the extreme theocratic agenda that the Discovery Institute was established for.
Some of the most innovative water collection technologies are inspired by natural organisms that have optimized their physiology to thrive in arid conditions such as deserts. In this work, we explore the physicochemical aspects of salt release and water collection mechanisms by a desert shrub that has adapted to thrive in hypersaline sands. This work not only reveals the dual nature of the mechanisms underlying a plant’s ability to survive in highly saline regions but could also become an inspiration to devise methods for enhancement of the water-harvesting capacity of artificial materials by combining different principles of water collection and salt release.
Abstract
Plants and animals that thrive in arid regions utilize the diurnal changes in environmental temperature and humidity to optimize their water budget by combining water-harvesting mechanisms and morphophysiological traits. The Athel tamarisk (Tamarix aphylla) is a halophytic desert shrub that survives in arid, hypersaline conditions by excreting concentrated solutions of ions as droplets on its surface that crystallize into salt crystals and fall off the branches. Here, we describe the crystallization on the surface of the plant and explore the effects of external conditions such as diurnal changes in humidity and temperature. The salt mixtures contain at least ten common minerals, with NaCl and CaSO4·2H2O being the major products, SiO2 and CaCO3 main sand contaminants, and Li2SO4, CaSO4, KCl, K2Ca(SO4)2·H2O, CaMg(CO3)2 and AlNaSi3O8 present in smaller amounts. In natural conditions, the hanging or sitting droplets remain firmly attached to the surface, with an average adhesion force of 275 ± 3.5 μN measured for pure water. Rather than using morphological features of the surface, the droplets adhere by chemical interactions, predominantly by hydrogen bonding. Increasing ion concentration slightly increases the contact angle on the hydrophobic cuticle, thereby lowering surface wettability. Small amounts of lithium sulfate and possibly other hygroscopic salts result in strong hygroscopicity and propensity for deliquescence of the salt mixture overnight. Within a broader context, this natural mechanism for humidity harvesting that uses environmentally benign salts as moisture adsorbents could provide a bioinspired approach that complements the currently available water collection or cloud-seeding technologies.
A summary of the water collection and salt crystallization over the diurnal cycle of T. aphylla. (A) The plant condenses water on its surface in the early morning when the humidity is high, and the temperature is low (9 a.m., 60% RH, 20 °C). (B) The water starts to evaporate, and the salts crystallize on the surface of the branch around midday, when the humidity is low and the temperature is high (12 p.m. noon, 35% RH, 30 °C). (C) During daytime, the water evaporates, resulting in the formation of salt crystals (7 p.m., 52% RH, 22 °C). (D) Overnight, when the humidity is high, the crystals adsorb water and dissolve (2 a.m., 80% RH, 18 °C).Al-Handawi, Marieh B.; Commins, Patrick; Dinnebier, Robert E.; Abdellatief, Mahmoud; Li, Liang; Naumov, Panče
Harvesting of aerial humidity with natural hygroscopic salt excretions
Proceedings of the National Academy of Sciences 120(45) e2313134120. doi: 10.1073/pnas.2313134120.
Copyright: © 2023 The authors.
Published by PNAS. Open access.
Reprinted under a Creative Commons Attribution 4.0 International license (CC BY 4.0)
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