W.The heat was It was among the first plants to be domesticated and is now the most widespread crop in the world. Thus it seems unlikely that there will be much more to learn about what makes it thrive. However, about 12,000 years after the start of relationships between people and wheat, a wheat plant was discovered doing something unexpected. She helped herself get a dose of much-needed phosphorous when her leaves got desert dust.
The plant (or rather plants) was in the care of Avner Gross of Ben-Gurion University of the Negev in Israel. As Dr. Gross said at this year’s meeting of the American Geophysical Union, which took place online during the first half of December, his study was prompted by his hiking visits near Neve Shalom, his village in the Judean Hills. In this regard, he often observed the leaves of a plant completely covered in dust carried by sandstorms from the Sahara Desert.
It occurred to him that this dust might not be the nuisance blocking the light that appeared at first glance. On the contrary, it could be beneficial due to the growth-promoting elements like phosphorous it contains. Until then, botanists had assumed that the phosphorous in the dust falling on the plant was of little value, because it is trapped in an insoluble mineral called apatite. This makes it unavailable for absorption. However, Dr. Gross suggested that plants that have evolved near deserts, the source of nearly all the natural dust in the atmosphere, may have developed a way to exploit it.
He and his colleagues, Sudip Tiwari, also in Ben Gurion, and Ran Erell of the Gelat Research Center, began experimenting with a pair of varieties, wheat and chickpea (the seventeenth most cultivated crop in the world), both of which originally came from the Levantine East. As a control, they also bred some corn, a plant from the Americas that evolved in less dusty surroundings.
First, having established them as seedlings, they starved the phosphorous charge until signs of deficiency appeared like yellow leaves. Then they spread desert dust on the leaves of half of the samples of each species, while taking steps to prevent any of them from reaching the soil. Then, although the dusty corn continued to suffer from a phosphorous deficiency, the wheat and chickpea plants proliferated and grew to more than twice the size of their non-expatriate lab colleagues. Moreover, this species was clearly ready for the arrival of dust. Once the phosphorous deficiency declared itself, two things happened. Its leaves are hairier and therefore better at catching dust. The leaves also began to produce acidic fluids that can dissolve any incoming apatite, thus helping the phosphorous uptake.
The ability of plants to absorb phosphorous through their leaves is not in itself news for growers – this was established in the 1950s. But so far the practical result of this knowledge has been to spray crops with liquid fertilizers derived, in turn, from apatite-containing rocks that have been treated with acid. Dr. Gross suggests that leaf dust could be an alternative and more effective way to supply desert-derived crop varieties with the phosphorous they need. And maybe not just these. His next plan is to look at the avocado and cocoa trees, which have evolved in tropical regions of the Americas that regularly get a beneficial dose across the Atlantic from the desert dust carried west by the trade winds. It will be interesting to see if they follow the same tricks as wheat and chickpea.■
This article appeared in the Science and Technology section of the print version titled “Good catch.”
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